Has anyone changed their hubs to change bolt pattern?
12-03-05, 09:57 PM
#5
Actually, I'm going to be doing that. That's a Porsche bolt pattern. There are rims I really want/am dead set on/incredibly stubborn about, but don't come in the width I'd like. They have 'em in much wider sizes for Porsches, hence why I'm changing out the rears with a wheel spacer & adapter.
I'd only go with the 6061 T6 Billet aluminum spacer & adapter from Performance Wheel & Tire: http://www.performancewheel.com/spacers.cfm Only place that actually stands behind their spacers & adapters. You provide them with all the information, and they'll tell you if it's safe to do or not. If it's safe, they'll do it and guaratee they won't fail. I spoke w/ the head guy who does the calculations and makes the actual spacers, and he told me mine would work no problem.
Now of course, since a Porsche's rear wheels have a +35 offset, and the adapter must space your wheels by 1" (ie 25mm) minimum (minimum safe thickness), that leaves you w/ a +10 offset or so. Obviously, that won't work w/o fender flares (OEM is +50, you're now at +10, you're sticking out +40 from ideal, and +30 from the fender's limit). Since I'm going to be running 50mm rear fenders/fender flares, I'm good to go, w/ 10mm to spare (about 2/5ths of an inch). In fact, after disussing this at LENGTH w/ the two leading offset experts on the forum, Daniel (dclin) and Rishie (ARD T2) of Auto RnD, I was told that I'm good w/ a +15 to a 0 offset with my setup (wheels, tires, spacer/adapters, and wide fenders). Guys were AMAZING in spending a LOT of time talking to me like the suspension idiot I am, and explaning everything to me
So in short, YES it can be done, but a) the offset has to be taken care of so it'll fit right, and you'll need fender flares, and b) you gotta make sure you have good safe spacers/adapters.
~Ramy
I'd only go with the 6061 T6 Billet aluminum spacer & adapter from Performance Wheel & Tire: http://www.performancewheel.com/spacers.cfm Only place that actually stands behind their spacers & adapters. You provide them with all the information, and they'll tell you if it's safe to do or not. If it's safe, they'll do it and guaratee they won't fail. I spoke w/ the head guy who does the calculations and makes the actual spacers, and he told me mine would work no problem.
Now of course, since a Porsche's rear wheels have a +35 offset, and the adapter must space your wheels by 1" (ie 25mm) minimum (minimum safe thickness), that leaves you w/ a +10 offset or so. Obviously, that won't work w/o fender flares (OEM is +50, you're now at +10, you're sticking out +40 from ideal, and +30 from the fender's limit). Since I'm going to be running 50mm rear fenders/fender flares, I'm good to go, w/ 10mm to spare (about 2/5ths of an inch). In fact, after disussing this at LENGTH w/ the two leading offset experts on the forum, Daniel (dclin) and Rishie (ARD T2) of Auto RnD, I was told that I'm good w/ a +15 to a 0 offset with my setup (wheels, tires, spacer/adapters, and wide fenders). Guys were AMAZING in spending a LOT of time talking to me like the suspension idiot I am, and explaning everything to me
So in short, YES it can be done, but a) the offset has to be taken care of so it'll fit right, and you'll need fender flares, and b) you gotta make sure you have good safe spacers/adapters.
~Ramy
12-03-05, 10:08 PM
#6
Also, I wanted to add this thread: https://www.rx7club.com/showthread.p...ight=spacer%2A
You'll see that while some individuals raise concerns about the safety of a wheel spacer (allegedly increasing the load on the studs), Takumi's response (post #29) is right on the money, from the research I've done.
~Ramy
You'll see that while some individuals raise concerns about the safety of a wheel spacer (allegedly increasing the load on the studs), Takumi's response (post #29) is right on the money, from the research I've done.
~Ramy
Originally Posted by Takumi
Spacers.....
First of all, wheel studs don't hold the wheel, but the friction between the hub and wheel does. That's why properly torquing down the lug nuts is crucial and some high torque cars use 6 studs (SUVs, Vipers).
With that said, using spacers would not increase the load in the studs, because what they do is to provide a "pressing force" on the wheel to the hub. So the only load exerts on a wheel stud is AXIAL, no bending or shear. Therefore, having a spacer or not would not make much a difference.
Effects of spacers can be beneficial. It increases track width hence, as other has already pointed out, decreases weight transfer at cornering ---> increase grip, more power to the gound. But also, the front needs to be balanced out otherwise it would have too much understeer.
Drawbacks of spacer:
1) It increases stress on the wheel bearing. It might get worn out faster.
2) It increases the motion ratio of the suspension geometry, and causes the wheel rate to decrease. In other words, it retards the effectiveness of the spring so when spacers are used, the car would feel "softer".
That's all I can think of right now.
First of all, wheel studs don't hold the wheel, but the friction between the hub and wheel does. That's why properly torquing down the lug nuts is crucial and some high torque cars use 6 studs (SUVs, Vipers).
With that said, using spacers would not increase the load in the studs, because what they do is to provide a "pressing force" on the wheel to the hub. So the only load exerts on a wheel stud is AXIAL, no bending or shear. Therefore, having a spacer or not would not make much a difference.
Effects of spacers can be beneficial. It increases track width hence, as other has already pointed out, decreases weight transfer at cornering ---> increase grip, more power to the gound. But also, the front needs to be balanced out otherwise it would have too much understeer.
Drawbacks of spacer:
1) It increases stress on the wheel bearing. It might get worn out faster.
2) It increases the motion ratio of the suspension geometry, and causes the wheel rate to decrease. In other words, it retards the effectiveness of the spring so when spacers are used, the car would feel "softer".
That's all I can think of right now.
12-04-05, 06:20 AM
#7
You better REALLY love the wheels your trying to put on... if they are just a set you got cheap, think again, because the conversion cost and hassle would probablty be more $$ than a set of the right size wheels!
The only reason i'd shange my hub patter is to go with center locking wheels!
The only reason i'd shange my hub patter is to go with center locking wheels!
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12-04-05, 06:40 PM
#9
Peter, yes I REALLY love these wheels...and they're not just wheels I got for cheap. I'm buying these wheels new, and they're $700 a pop. Right up there w/ your RGRs. Bottom line, I'm VERY picky when it comes to wheels. I like a lot of wheels in general, but there are only 2 I like enough to put on my car: Fikse FM-5s and SSR GT3s. And in this case, I'm talking about the SSR GT3s. They come in 11.5" for Porsches. Only come in 10s (max) for the FD. So I'm going to sell my 8.5s (fronts), move the 10s from the rear to the front (no spacers/adapters necessary; wheels will fit w/ the fender flares that give me 20mm additional, and the 10s have a +41 offset), and buy 2 new rear 11.5" SSR GT3s.
nopistons94, sorry, when I meant Porsche wheels, I didn't mean exclusively Porsche. I meant that SSR ONLY makes SSR GT3s that wide to fit a Porsche. All other cars only go to 10.5" wide max.
The hardest part of the entire process will be locating the wheels, seeing that the GT3s are low in availability. Might have to grab 'em now while I still can...
~Ramy
Bottom line, I'm VERY picky when it comes to wheels. I like a lot of wheels in general, but there are only 2 I like enough to put on my car: Fikse FM-5s and SSR GT3s. And in this case, I'm talking about the SSR GT3s. They come in 11.5" for Porsches. Only come in 10s (max) for the FD. So I'm going to sell my 8.5s (fronts), move the 10s from the rear to the front (no spacers/adapters necessary; wheels will fit w/ the fender flares that give me 20mm additional, and the 10s have a +41 offset), and buy 2 new rear 11.5" SSR GT3s.nopistons94, sorry, when I meant Porsche wheels, I didn't mean exclusively Porsche. I meant that SSR ONLY makes SSR GT3s that wide to fit a Porsche. All other cars only go to 10.5" wide max.
The hardest part of the entire process will be locating the wheels, seeing that the GT3s are low in availability. Might have to grab 'em now while I still can...
~Ramy
for about 5 min haha
12-06-05, 02:12 PM
#12
Lives on the Forum
Originally Posted by FDNewbie
You'll see that while some individuals raise concerns about the safety of a wheel spacer (allegedly increasing the load on the studs), Takumi's response (post #29) is right on the money, from the research I've done.
Originally Posted by Takumi
First of all, wheel studs don't hold the wheel, but the friction between the hub and wheel does. That's why properly torquing down the lug nuts is crucial and some high torque cars use 6 studs (SUVs, Vipers).
With that said, using spacers would not increase the load in the studs, because what they do is to provide a "pressing force" on the wheel to the hub. So the only load exerts on a wheel stud is AXIAL, no bending or shear. Therefore, having a spacer or not would not make much a difference.
With that said, using spacers would not increase the load in the studs, because what they do is to provide a "pressing force" on the wheel to the hub. So the only load exerts on a wheel stud is AXIAL, no bending or shear. Therefore, having a spacer or not would not make much a difference.
Originally Posted by Takumi
Effects of spacers can be beneficial. It increases track width hence, as other has already pointed out, decreases weight transfer at cornering ---> increase grip, more power to the gound. But also, the front needs to be balanced out otherwise it would have too much understeer
Originally Posted by Takumi
Drawbacks of spacer:
1) It increases stress on the wheel bearing. It might get worn out faster.
1) It increases stress on the wheel bearing. It might get worn out faster.
Originally Posted by Takumi
2) It increases the motion ratio of the suspension geometry, and causes the wheel rate to decrease. In other words, it retards the effectiveness of the spring so when spacers are used, the car would feel "softer".
Basically if the spacer is hubcentric and is merely being used so that a wheel with the "wrong" offset may be fitted to the car, the studs and car will not know the difference.
My apologies to Takumi if these are out of context. I have not seen his original post.
Last edited by DamonB; 12-06-05 at 02:16 PM.
12-06-05, 03:29 PM
#14
Originally Posted by DamonB
Takumi is right with some qualifiers:
ONLY IF THE WHEEL, SPACER AND HUB ARE HUBCENTRIC TO EACH OTHER. If the spacer is merely a flat plate (not hubcentric) then the studs are supporting the weight of the car and that is a no-no.
Does a hubcentric spacer look like this (the lip)?
The spacer will only cause added stress to the wheel bearing and suspension if the total offset of the spacer plus the offset of the new wheel equals non-stock. If the total offset of the spacer plus the new wheel offset equals stock then the wheel bearing doesn't know the difference.
The spacer will only change motion ratio if the total offset of the spacer plus the offset of the new wheel equals non-stock. If the total offset of the spacer plus the new wheel offset equals stock then the motion ratio does not change.
Basically if the spacer is hubcentric and is merely being used so that a wheel with the "wrong" offset may be fitted to the car, the studs and car will not know the difference.
My apologies to Takumi if these are out of context. I have not seen his original post.
Thanks for all the help (as usual)
~Ramy
12-06-05, 03:49 PM
#15
Hey Damon, I called the shop (Performance Wheel & Tire: http://www.performancewheel.com/spacers.cfm) and spoke w/ one of the spacer/adapter guys there, asked him if the spacers were hubcentric, and he said no, they're lugcentric. And he said the only reason we have hubcentric wheels is to center the wheel, but it doesn't affect it's performance or something like that... I asked if lugcentric spacers would add more stress on the bolts, and he said no... He said some more stuff too, most of which I wasn't understanding, made me feel dumb, so I said thanks, and hung up lol. Your take? Or if you'd even wanna have a go at it haha
I'm not doubting you...just trying to understand, and I'm sure him, being at a shop, he'll sellin me anything no matter what
~Ramy
I'm not doubting you...just trying to understand, and I'm sure him, being at a shop, he'll sellin me anything no matter what
~Ramy
12-06-05, 04:09 PM
#16
Lives on the Forum
Originally Posted by FDNewbie
Does a hubcentric spacer look like this (the lip)?
With a spacer we are adding a piece into the middle of the hub/wheel sandwich. That means the spacer must have a hollow in the back that mates perfectly with the lip on the hub, and it must also have a lip on the front that mates perfectly with the hollow in the back of the wheel.
Originally Posted by FDNewbie
That's a given though. Unless you're buying wheels w/ some crazy high offset (like a +70 or something), a spacer will always push the wheel far enough out to have the final offset equal non-stock
http://www.tirerack.com/wheels/tech/...jsp?techid=101
Think of the spacer as becoming part of the wheel. If the aftermarket wheel offset plus the offset of the spacer equals the stock wheel offset the car will in no way be able to tell. It will look exactly the same from the car's point of view because the center of the tire's contact patch in space will be in the exact same position in both cases.
12-06-05, 07:06 PM
#17
Ok instead of bother with you 1001 questions (
) I did a bit of reading on a few diff websites, and I think I understand what you're saying a LOT better. Not that you need my approval, but you're 100% right, if it's not hubcentric, it has no lip, so yes, the studs carry the load, vs. having the adapter sit on the FACTORY hub, so the hubcentric adapter is exactly like your factory hub in terms of carrying the weight. Beautiful
Having said that...aren't factory hub lips different widths? I've seen pics of some which were only 1/2 an inch thick, and others that were much thicker (prob an 1" at least). I'm guessing this is something they can look up on a computer and know exactly the depth/width of the factory hub lip?
Just a tidbit I picked up from this site: http://bernardembden.com/xjs/hubcentric/ One (if not the main) reason that a lugcentric adapter bears more weight/stress on the lugs is b/c w/o a tight fitting hub lip (ie a non-hubcentric adapter), the space around the wheel studs will be uneven, and thus apply more stress on some studs than others. That's in addition to what you point out below: that the lip is made to bear the weight of the car, and non-hubcentric adapters eliminate that key fact. Pretty scary...
It's freakin crystal clear Damon!
On that note, forget that fruity company (Performance Wheel & Tire) that I spoke of before. I just got off the phone w/ a guy who seemed very knowledgeable and took the time to answer all my questions in detail... Skulte Performance Designs (http://www.skulte.com/info_pages.php/pages_id/3). They make hubcentric adapters and spacers, fully custom, all diff thicknesses and bolt patterns, and from the same material: precision CNC machined aerospace grade 6061-T6 aluminum. They even offer a wheel centric lip if you want, but say that for adapters under 3", it's unnecessary, as they've never had any vibration issues with smaller adapters. Sounds like we got a winner
If anyone's curious, he quoted me for my application (5 lug to 5 lug adapter, approx. 1" thickness) $125 for the pair. He did tell me however that I need to look at the back of my wheels and see if there are indentations around the lug holes for the stock studs to fit/sit. Otherwise, the lug nuts may stick out from the face of the wheel. The other option to avoid this is to increase the thickness of the adapter a bit. He said 1.25" adapters should cover the length of pretty much any common stud.
Yea I understand that part, but I get lost amidst the calculations. Tell me if I'm wrong here. Stock offset is +50. So the wheel sits 50mm OUTward. The Porsche wheels are a +35 offset. That means they sit 15mm inward compared to the stock offset. Right?
So if I use a 1.25" adapter, I gain/add on about 32mm. So my new final offset is now +67mm. The wheel is sitting OUTWARD 17mm. Right?
I'm going w/ fender flares that will give me up to +50mm outward additional if I understand correctly (so total possible offset of +100). So at +67, I still have between 1.25" and 1.33" between the edge of the wheel and the wide fenders.
According to Daniel and Richie, ideally w/ my setup, I should be going for (going by the old convention) a +15 to a 0 offset, which w/ the new convention would equal +85 to + 100 offset, no?
I'll stop here, cuz I'm sure w/ all the offset calculation mumbo jumbo I just wrote, someone's gonna chime in and be like "you're a DUMBASS..." LOL
~Ramy
) I did a bit of reading on a few diff websites, and I think I understand what you're saying a LOT better. Not that you need my approval, but you're 100% right, if it's not hubcentric, it has no lip, so yes, the studs carry the load, vs. having the adapter sit on the FACTORY hub, so the hubcentric adapter is exactly like your factory hub in terms of carrying the weight. Beautiful Having said that...aren't factory hub lips different widths? I've seen pics of some which were only 1/2 an inch thick, and others that were much thicker (prob an 1" at least). I'm guessing this is something they can look up on a computer and know exactly the depth/width of the factory hub lip?
Just a tidbit I picked up from this site: http://bernardembden.com/xjs/hubcentric/ One (if not the main) reason that a lugcentric adapter bears more weight/stress on the lugs is b/c w/o a tight fitting hub lip (ie a non-hubcentric adapter), the space around the wheel studs will be uneven, and thus apply more stress on some studs than others. That's in addition to what you point out below: that the lip is made to bear the weight of the car, and non-hubcentric adapters eliminate that key fact. Pretty scary...
Originally Posted by DamonB
Yes. On a stock car there is a lip on the hub that fits inside a hollow in the back of the wheel. This lip carries the weight of the car and all the studs must then do is keep the wheel pushed against the hub as well as feed brake and power torque from the tire, through the wheel and into the hub.
With a spacer we are adding a piece into the middle of the hub/wheel sandwich. That means the spacer must have a hollow in the back that mates perfectly with the lip on the hub, and it must also have a lip on the front that mates perfectly with the hollow in the back of the wheel.
With a spacer we are adding a piece into the middle of the hub/wheel sandwich. That means the spacer must have a hollow in the back that mates perfectly with the lip on the hub, and it must also have a lip on the front that mates perfectly with the hollow in the back of the wheel.
It's freakin crystal clear Damon! On that note, forget that fruity company (Performance Wheel & Tire) that I spoke of before. I just got off the phone w/ a guy who seemed very knowledgeable and took the time to answer all my questions in detail... Skulte Performance Designs (http://www.skulte.com/info_pages.php/pages_id/3). They make hubcentric adapters and spacers, fully custom, all diff thicknesses and bolt patterns, and from the same material: precision CNC machined aerospace grade 6061-T6 aluminum. They even offer a wheel centric lip if you want, but say that for adapters under 3", it's unnecessary, as they've never had any vibration issues with smaller adapters. Sounds like we got a winner
If anyone's curious, he quoted me for my application (5 lug to 5 lug adapter, approx. 1" thickness) $125 for the pair. He did tell me however that I need to look at the back of my wheels and see if there are indentations around the lug holes for the stock studs to fit/sit. Otherwise, the lug nuts may stick out from the face of the wheel. The other option to avoid this is to increase the thickness of the adapter a bit. He said 1.25" adapters should cover the length of pretty much any common stud.
Not necessarily; depends on the offset of the aftermarket wheel you're trying to fit. If the aftermarket wheel didn't have enough offset to start with for your application you could add a spacer to increase the offset. I figured that's what you were doing.
http://www.tirerack.com/wheels/tech/...jsp?techid=101
Think of the spacer as becoming part of the wheel. If the aftermarket wheel offset plus the offset of the spacer equals the stock wheel offset the car will in no way be able to tell. It will look exactly the same from the car's point of view because the center of the tire's contact patch in space will be in the exact same position in both cases.
http://www.tirerack.com/wheels/tech/...jsp?techid=101
Think of the spacer as becoming part of the wheel. If the aftermarket wheel offset plus the offset of the spacer equals the stock wheel offset the car will in no way be able to tell. It will look exactly the same from the car's point of view because the center of the tire's contact patch in space will be in the exact same position in both cases.
So if I use a 1.25" adapter, I gain/add on about 32mm. So my new final offset is now +67mm. The wheel is sitting OUTWARD 17mm. Right?
I'm going w/ fender flares that will give me up to +50mm outward additional if I understand correctly (so total possible offset of +100). So at +67, I still have between 1.25" and 1.33" between the edge of the wheel and the wide fenders.
According to Daniel and Richie, ideally w/ my setup, I should be going for (going by the old convention) a +15 to a 0 offset, which w/ the new convention would equal +85 to + 100 offset, no?
I'll stop here, cuz I'm sure w/ all the offset calculation mumbo jumbo I just wrote, someone's gonna chime in and be like "you're a DUMBASS..." LOL
~Ramy
12-06-05, 10:01 PM
#18
Hey Ramy, I think you have some concepts mixed up. No worries, its a tough thing to wrap one's mind around (at least for me, slow that I am), Here we go:
First off, keep in mind what 'offset' is. Mentally picture a wheel and imagine a center line that bisects it into two even halves. The measurement from this imaginary center line to the mounting hub face of the wheel is the offset.
Most modern passenger vehicles have a postive offset, which means that the wheel's mounting hub face is on the 'outside' of the imaginary center line. If you had x-ray vision and looked at a car from directly behind, you would see the hub face on the outboard side of the imaginary center line of the wheel. Negative offset then, is a hub face that sits on the inboard side of the wheels' imaginary center line.
Secondly, you cannot talk about offsets without considering the wheel width. An 18x8 +50 and a 18x10 +50, for example, are two different things. If, for example, an 8" width wheel with a +50 offset sits 1" inset (has 1" of clearance) from the fender lip, a 10" wheel with the same offset would sit flush with the fender lip. This is because the 2 extra inches of the wider wheel is split on both sides of the imaginary center line; 1" is added to the outboard side, and 1" is added to the inboard side. That extra 1"on the outboard side wiped out the 1" inset/clearance the narrower 18x8 wheel had. In the same way, the inboard side lost 1" of clearance as well, in this example. For the moment though, we'll save the wheel width factor for later. When figuring out fitment, you deal with one set of figures at a time (if you're slow like me).
Yea I understand that part, but I get lost amidst the calculations. Tell me if I'm wrong here. Stock offset is +50. So the wheel sits 50mm OUTward. The Porsche wheels are a +35 offset. That means they sit 15mm inward compared to the stock offset. Right?
You've got this mixed up. Now that we've got the idea of offsets squared away, we now know that all +50 means is the distance between the imaginary center line of the wheel and the wheels hub face. In the case of the stock wheel, there is 50mm of distance. Because it is '+', it means the wheel hub face sits on the outboard side of the imaginary center line. Now, with the new wheel, the distance between the imaginary center line and the wheel hub face is only 35mm. Because it is '+', it's still on the outboard side.
If you were to mentally take both wheels and flip them upside down on the floor and stand over them, looking down, you would see (important!! remember what perspective I'm looking at them from!!) the wheel hub face of the +35 would be sitting 15mm higher off the ground then the +50.
Remember, the axle hub is stationary/fixed. Now take those two wheels and mentally mount them on to the axle hub. The +35 wheel will have a lip that sits 15mm outboard then the +50. Why? Another way to look as this is to mentally keep the wheel hub face in the same position for both wheels. The 15mm loss between the two offsets causes the imaginary center line (and therfore the entire outer rim) to shift outward.
Makes sense? Therefore, assuming same wheel width, a +35 wheel will sit 15mm outboard of the +50 wheel.
So if I use a 1.25" adapter, I gain/add on about 32mm. So my new final offset is now +67mm. The wheel is sitting OUTWARD 17mm. Right?
Remember, offset is the distance between the imaginary center line of the wheel and the wheel hub face. Take that imaginary wheel off and flip upside down on the floor again. If you were to put a 1.25" (approx 32mm) spacer on the wheel hub face (which is the same thing as putting it on the axle hub face), you would move the effective wheel hub face closer to the imaginary center line by 32mm. Taking the Porsche wheel offset of +35, you now have an effective offset of +3
I'm going w/ fender flares that will give me up to +50mm outward additional if I understand correctly (so total possible offset of +100). So at +67, I still have between 1.25" and 1.33" between the edge of the wheel and the wide fenders.
If you have flares that add 50mm, then you would want to push the wheel outboard 50mm, which would make the offset in the above example -47 (don't freak out, we havn't considered wheel width yet! ). We are at +3 offset, and we want to shift the wheel hub face inboard 50mm. +3 means the wheel hub face sits 3mm outboard of the imaginary center line. Shifting it inward 50mm would push it past the imaginary center line into '-' offset territory, or -47. Sorta like algebra.
*(the offset in this example would actually be -46, as that '0' counts as a digit. I've ignored this, because it's a theoritcal excercise and don't want to make it more confusing; and 1mm ain't ****)
Now we take into consideration WHEEL WIDTH. The stock wheel width is 8". You want to use a 11.5" width wheel. Taking what we've learned above, a 18x11.5" would be 3.5" wider then an 18x8 (duh). That extra 3.5" would be evenly divided on the inboard side of the wheel and the outboard side of the wheel, or 1.75". That means, offset being equal, the 18x11.5 -47 (if anybody built it) would stick out past the 18x8 -47 by 1.75" (and also be closer to the suspension bits by 1.75"as well).
1.75" is approx 45mm, which we need to compensate for (push the wheel back in). This means moving the -47 offset 45mm, netting an effective offset of -2. Because we are in negative territory, going froma -47 offset to a -2 offset actually shifts the entire wheel inwards. Use your x-ray vision again and look that the car/wheel from behind to visualize.
Now, the 16x8 we've been using as baseline (or 18x8 for that matter) sits nowhere close to being flush with the stock fenders. Likewise, if we stayed with these numbers, the 18x11.5 will be equally inset from the fender lip as the 16x8 (or 18x8) would be. If you want it more flush, then you would want to push it back out. How much? Depends on what you are comfortable with, you could likely add an 1" and still stay under the fender lip.
So, according to these figures, you can use anything froma 18x11.5 -2 to a +23, maybe even more based on some extreme offset/width numbers I've seen on stock fendered FDs. A 0 to +15mm offset range falls neatly within this.
Hope that helps!
According to Daniel and Richie, ideally w/ my setup, I should be going for (going by the old convention) a +15 to a 0 offset, which w/ the new convention would equal +85 to + 100 offset, no?
I'll stop here, cuz I'm sure w/ all the offset calculation mumbo jumbo I just wrote, someone's gonna chime in and be like "you're a DUMBASS..." LOL
~Ramy
First off, keep in mind what 'offset' is. Mentally picture a wheel and imagine a center line that bisects it into two even halves. The measurement from this imaginary center line to the mounting hub face of the wheel is the offset.
Most modern passenger vehicles have a postive offset, which means that the wheel's mounting hub face is on the 'outside' of the imaginary center line. If you had x-ray vision and looked at a car from directly behind, you would see the hub face on the outboard side of the imaginary center line of the wheel. Negative offset then, is a hub face that sits on the inboard side of the wheels' imaginary center line.
Secondly, you cannot talk about offsets without considering the wheel width. An 18x8 +50 and a 18x10 +50, for example, are two different things. If, for example, an 8" width wheel with a +50 offset sits 1" inset (has 1" of clearance) from the fender lip, a 10" wheel with the same offset would sit flush with the fender lip. This is because the 2 extra inches of the wider wheel is split on both sides of the imaginary center line; 1" is added to the outboard side, and 1" is added to the inboard side. That extra 1"on the outboard side wiped out the 1" inset/clearance the narrower 18x8 wheel had. In the same way, the inboard side lost 1" of clearance as well, in this example. For the moment though, we'll save the wheel width factor for later. When figuring out fitment, you deal with one set of figures at a time (if you're slow like me).
Originally Posted by FDNewbie
Yea I understand that part, but I get lost amidst the calculations. Tell me if I'm wrong here. Stock offset is +50. So the wheel sits 50mm OUTward. The Porsche wheels are a +35 offset. That means they sit 15mm inward compared to the stock offset. Right?
If you were to mentally take both wheels and flip them upside down on the floor and stand over them, looking down, you would see (important!! remember what perspective I'm looking at them from!!) the wheel hub face of the +35 would be sitting 15mm higher off the ground then the +50.
Remember, the axle hub is stationary/fixed. Now take those two wheels and mentally mount them on to the axle hub. The +35 wheel will have a lip that sits 15mm outboard then the +50. Why? Another way to look as this is to mentally keep the wheel hub face in the same position for both wheels. The 15mm loss between the two offsets causes the imaginary center line (and therfore the entire outer rim) to shift outward.
Makes sense? Therefore, assuming same wheel width, a +35 wheel will sit 15mm outboard of the +50 wheel.
Originally Posted by FDNewbie
So if I use a 1.25" adapter, I gain/add on about 32mm. So my new final offset is now +67mm. The wheel is sitting OUTWARD 17mm. Right?
Originally Posted by FDNewbie
I'm going w/ fender flares that will give me up to +50mm outward additional if I understand correctly (so total possible offset of +100). So at +67, I still have between 1.25" and 1.33" between the edge of the wheel and the wide fenders.
). We are at +3 offset, and we want to shift the wheel hub face inboard 50mm. +3 means the wheel hub face sits 3mm outboard of the imaginary center line. Shifting it inward 50mm would push it past the imaginary center line into '-' offset territory, or -47. Sorta like algebra.*(the offset in this example would actually be -46, as that '0' counts as a digit. I've ignored this, because it's a theoritcal excercise and don't want to make it more confusing; and 1mm ain't ****)
Now we take into consideration WHEEL WIDTH. The stock wheel width is 8". You want to use a 11.5" width wheel. Taking what we've learned above, a 18x11.5" would be 3.5" wider then an 18x8 (duh). That extra 3.5" would be evenly divided on the inboard side of the wheel and the outboard side of the wheel, or 1.75". That means, offset being equal, the 18x11.5 -47 (if anybody built it) would stick out past the 18x8 -47 by 1.75" (and also be closer to the suspension bits by 1.75"as well).
1.75" is approx 45mm, which we need to compensate for (push the wheel back in). This means moving the -47 offset 45mm, netting an effective offset of -2. Because we are in negative territory, going froma -47 offset to a -2 offset actually shifts the entire wheel inwards. Use your x-ray vision again and look that the car/wheel from behind to visualize.
Now, the 16x8 we've been using as baseline (or 18x8 for that matter) sits nowhere close to being flush with the stock fenders. Likewise, if we stayed with these numbers, the 18x11.5 will be equally inset from the fender lip as the 16x8 (or 18x8) would be. If you want it more flush, then you would want to push it back out. How much? Depends on what you are comfortable with, you could likely add an 1" and still stay under the fender lip.
So, according to these figures, you can use anything froma 18x11.5 -2 to a +23, maybe even more based on some extreme offset/width numbers I've seen on stock fendered FDs. A 0 to +15mm offset range falls neatly within this.
Hope that helps!
Originally Posted by FDNewbie
According to Daniel and Richie, ideally w/ my setup, I should be going for (going by the old convention) a +15 to a 0 offset, which w/ the new convention would equal +85 to + 100 offset, no?
I'll stop here, cuz I'm sure w/ all the offset calculation mumbo jumbo I just wrote, someone's gonna chime in and be like "you're a DUMBASS..." LOL
~Ramy
Last edited by dclin; 12-06-05 at 10:30 PM.
12-06-05, 10:47 PM
#19
Originally Posted by dclin
So, according to these figures, you can use anything froma 18x11.5 -2 to a +23, maybe even more based on some extreme offset/width numbers I've seen on stock fendered FDs. A 0 to +15mm offset range falls neatly within this.
Hope that helps!
Hope that helps!
12-06-05, 11:04 PM
#20
Originally Posted by dclin
Now, the 16x8 we've been using as baseline (or 18x8 for that matter) sits nowhere close to being flush with the stock fenders. Likewise, if we stayed with these numbers, the 18x11.5 will be equally inset from the fender lip as the 16x8 (or 18x8) would be. If you want it more flush, then you would want to push it back out. How much? Depends on what you are comfortable with, you could likely add an 1" and still stay under the fender lip.
So, according to these figures, you can use anything froma 18x11.5 -2 to a +23, maybe even more based on some extreme offset/width numbers I've seen on stock fendered FDs. A 0 to +15mm offset range falls neatly within this.
Hope that helps!
So, according to these figures, you can use anything froma 18x11.5 -2 to a +23, maybe even more based on some extreme offset/width numbers I've seen on stock fendered FDs. A 0 to +15mm offset range falls neatly within this.
Hope that helps!
12-07-05, 01:49 AM
#21
Oh My God lol. And ppl wonder why there are a 1001 questions about offsets?!
First of all, Daniel, I gotta thank you yet AGAIN like crazy...that explanation was AMAZING. I really appreciate you taking the time to write it out. It took me maybe 20 min to go through it (had to stop, visualize what you were saying, and sometimes that wasn't happening off the bat haha), but in the end, I got it.
I'm with you the WHOLE entire way, except the VERY last step, where you skipped an explanation/step lol. I don't follow.
Got the 18 X 11.5 wheel, pushed it out 47, which would be fine if it was an 8" wheel. But you gotta make room for the extra 1.75" (45 mm) on each side, so you gotta move the wheel inward by 45 mm. So you get the +2. Beautiful.
Now, you're not worried about the INSIDE of the wheel at all, because we've already pushed it out so far that it's past the stock middle point, right? So I'm going to clear the suspension components by a mile, correct?
Now when you say the stock wheels aren't flush w/ the stock fenders, so my calculations would leave the wheel not flush from the wide fenders...I have an inch to go outward... that's an inch in one direction/one way, right? I basically have 25 mm to spare that I could push the wheel OUT with, and it would still clear the fender, correct? Now those 25mm would be in the form of a THICKER spacer, right? Because the thicker the spacer, the less positive the offset, the further OUT the wheel will stick, right? (This is all for understanding's sake...I'm fine w/ the 1" lateral space. No need to push it, plus I don't want to put too much stress on the wheel bearings & suspension components by having the wheels incredibly far out comapred to stock).
So when you said -2 to 23, that's taking into consideration the 1" I can move the wheel out (-2 + 1" aka 25mm = +23, right?). So I'm good with that... -2 to +23. How on EARTH did you get from that, to a 0 offset to +15mm offset? There's a conversion/step there that I don't see...
And lastly, the 0 offset would leave the wheel further out (closer to the end of that 1" limit), while the +15mm would leave it a bit closer inward. How do I figure out the proper spacer size? Simple math? Wheel is +35, I want a FINAL offset between +15 to 0, so I'm looking at a spacer that's 20mm (35mm - 15mm) to 35mm (35mm - 0mm) thick? (about 3/4" thick to about 1.33" thick, roughly speaking)? Cuz in that case, to make sure the lug nuts sit flush (spacer's gotta be thick enough to be the length of the studs so the lug nuts are flush), I'd go with a 1.25" (31.75mm) spacer. Sound good? Still leaves me a bit of wiggle room...
Whew. Man...you should get paid for this stuff...
Incredibly grateful,
~Ramy
PS: I'm especially grateful since I just got off the phone w/ Tire Rack earlier today, and they said the SSR GT3s may not be continued after all, and they only have a few wheels in this size left!
So now I'm pressed for time to make sure it's all gravy...
First of all, Daniel, I gotta thank you yet AGAIN like crazy...that explanation was AMAZING. I really appreciate you taking the time to write it out. It took me maybe 20 min to go through it (had to stop, visualize what you were saying, and sometimes that wasn't happening off the bat haha), but in the end, I got it.
I'm with you the WHOLE entire way, except the VERY last step, where you skipped an explanation/step lol. I don't follow.
Got the 18 X 11.5 wheel, pushed it out 47, which would be fine if it was an 8" wheel. But you gotta make room for the extra 1.75" (45 mm) on each side, so you gotta move the wheel inward by 45 mm. So you get the +2. Beautiful.
Now, you're not worried about the INSIDE of the wheel at all, because we've already pushed it out so far that it's past the stock middle point, right? So I'm going to clear the suspension components by a mile, correct?
Now when you say the stock wheels aren't flush w/ the stock fenders, so my calculations would leave the wheel not flush from the wide fenders...I have an inch to go outward... that's an inch in one direction/one way, right? I basically have 25 mm to spare that I could push the wheel OUT with, and it would still clear the fender, correct? Now those 25mm would be in the form of a THICKER spacer, right? Because the thicker the spacer, the less positive the offset, the further OUT the wheel will stick, right? (This is all for understanding's sake...I'm fine w/ the 1" lateral space. No need to push it, plus I don't want to put too much stress on the wheel bearings & suspension components by having the wheels incredibly far out comapred to stock).
So when you said -2 to 23, that's taking into consideration the 1" I can move the wheel out (-2 + 1" aka 25mm = +23, right?). So I'm good with that... -2 to +23. How on EARTH did you get from that, to a 0 offset to +15mm offset? There's a conversion/step there that I don't see...
And lastly, the 0 offset would leave the wheel further out (closer to the end of that 1" limit), while the +15mm would leave it a bit closer inward. How do I figure out the proper spacer size? Simple math? Wheel is +35, I want a FINAL offset between +15 to 0, so I'm looking at a spacer that's 20mm (35mm - 15mm) to 35mm (35mm - 0mm) thick? (about 3/4" thick to about 1.33" thick, roughly speaking)? Cuz in that case, to make sure the lug nuts sit flush (spacer's gotta be thick enough to be the length of the studs so the lug nuts are flush), I'd go with a 1.25" (31.75mm) spacer. Sound good? Still leaves me a bit of wiggle room...
Whew. Man...you should get paid for this stuff...
Incredibly grateful,
~Ramy
PS: I'm especially grateful since I just got off the phone w/ Tire Rack earlier today, and they said the SSR GT3s may not be continued after all, and they only have a few wheels in this size left!
So now I'm pressed for time to make sure it's all gravy...
Last edited by FDNewbie; 12-07-05 at 01:56 AM.
12-07-05, 03:20 AM
#22
No problem Ramy, I'll break it down tomorrow. Wife's finals are this week, and I'm helping prep her. What you are talking about is where I got my own brain twisted into a pretzle - it basically has to do with me making the leap from the +50 offset to the +35... and forgetting about it.
12-07-05, 10:01 AM
#24
Ramy, you're STARTING OUT with a +35 offset wheel, and expecting to be able to add a spacer?
If so, that isn't going to work. +35 is really too low to start with unless you're talking about an 8" wheel... and really you want +40 or more for either the front or the rear of an FD. To use even a 1" (20.5 mm) spacer, you'd need to START with a +60.5 mm offset wheel to NET a +40 offset with the spacer.
If so, that isn't going to work. +35 is really too low to start with unless you're talking about an 8" wheel... and really you want +40 or more for either the front or the rear of an FD. To use even a 1" (20.5 mm) spacer, you'd need to START with a +60.5 mm offset wheel to NET a +40 offset with the spacer.