Johnny

I dont know..18x10.5... that's huge...I dont think I could positively recommend those without coilovers..rolling fenders lip or something..because you would have to run 285's on that for sure. Looks like 8.5 might be the way to go for you...and your le37t's

ARD T2

iTrader: (22)

Wow, you guys got the record for the longest thread in the shortest amount of time. Let's call Guiness Book of World Records.

What Sleep did is exactly what I would have done, and in fact would have used almost the same resources. I love you guys, you're so internet Savy.

I am going to read the last few posts and check with my fitment guide right now. Not sure if you're still on, didn't look at the times, but I will respond in about 5 minutes. hehe.

Didn't want to keep you waiting to long.

Rishie

SleepR1

My guess would be 2.25 inches (57.15 mm) assuming a 10.5 overall wheel/tire width with 9.5-inch wide Forgelines. This would be the ultimate road/track setup, which I've already mentioned on page one of this topic! I'd be curious what offset your mech/tech has with his 9.5 x 17 Forgeline RSes. I'd go with those cool Bridgestone Potenza S-03s or Pirelli P-Zero Asimmetricos in 255/40-17 all around. I'm getting too old to swap wheels and tires. I either need a pit crew, or run the ultimate road/track wheel/tire setup

Johnny

I'll ask nexttime I see him.which shoule be early next week...he's closed until next wed....I need to go there for a alignment after putting in my GC coilovers and m2 links and arms... .. Hey Manny do the calcs for me...I have a 18x9 with a 50mm offset...I should be fine with 255's correct........? I got height adjustablilty anyways so I think I would be alright.

ARD T2

iTrader: (22)

Your only dilemna is the style of wheel you have chosen. If you were to pic a different style your chances of success would be much greater.

Holy Crap, the +50, 8.5's are actually coming in around the end of Jan. Looks like you might get lucky. I will need to do a physical check on an FD to see for proper fitment.

My simple method of interpolation of fitting offset, by using stock wheel and tire on the vehicle.

1. Stick fingers between tire and strut housing and lower spring perch. Since you're not worried about O.D. finger between the tire and strut is fine. Do a basic measurement with your fingers, i.e. measure the portion of finger used for approximation. i.e. 0.5" = 13mm of clearance on the inside. Let's round down and make it 10mm.

2. Compare the section width of the current tire being used and the desired tire's section width. Subtract the lesser from the greater and see if the number is small enough that it will fit where your fingers were.
Say there's a difference of an inch in section width =26mm. Well, we only have 10mm of room on the inside, so we still need to space the wheel out 16mm. Question now, is if there is room on the fender for not rubbing with that tire pushed out 16mm.

3. Then adjust the offset accordingly.

This is actually how I would do it if I had the vehicle in front of me and just needed to do a quick approximation. This actually a pretty good way to do it, without having to write **** down on paper. Which most of the time can't be done when working.

So I will see if I can hook up with Ivan and measure his car. FC's would be no problem, cause I have three of them. FD, problem, don't have one, but know tons of guys who do.

Thanks, Rishie

SleepR1

Perhaps we should look into 8.5 x 18 up front with 235/40-18 for the fronts and 9.5 x 18 with 265/35-18 in back (25.4/25.3 inches overall tire diameter both fr/rr)? That would make a nice compromise, ensure proper fiment and get you the staggered look you're after. Offsets that Volk will have for both 8.5 and 9.5 x 18 will range from 40 to 44 mm. I know for a fact that a 42 mm offset will work because that's what I have on my SSR Comps in 8.5 and 9.5 x 17, which I run Hoosier 245/45-17 and 275/40-17 on their respective rim widths (those Hoosier sizes have an overall tire diameter of 25.3 inches). Even with hard cornering at the track, I get no rubbing whatsoever (I have the stock diameter H&R sport springs).

Yes, bartender I'll have ANOTHER

SleepR1

Assuming that your 255/35-18 measures out to 10.3 inches in overall tire section width (S-03 width spec with 9-inch wide spec rim), and using the general rule of max front space of 3.5 inches we could do the math (but I won't bore you with the number crunching). Well ok maybe a little arithmetic. We could have Steve Cirian in here and check my figures:

(Tire Section Width in inches/2) - offset in inches = front space in inches:

Let's plug and chug baby (I happen to be chugging a Warsteiner--it's my 4th one, so I hope my fingers don't fail me on the calculator!)

(10.3/2) - 1.97 = 3.18 inchs of front space Oh, dude, You're way OK, no worries with contacting that left-front fender bolt. What' really cool is the stock overall tire diameter remains with your 255/35-18, right at 25 inches! Excellent! Just for kicks lets do your back space measurement (based on the 10.3-inch wide S-03), shall wee?

Overall Tire Width (inches) - Front Space (inches) = Back space (inches)

Since you have 2.5 inch coilover springs, you can have a max back space of 7.5 inches. Your fitment will use up:

10.3 - 3.18 = 7.12 inches of back space. Dude I could run your setup with my lowly stock sized H&R springs!

How about another round, I'm buying!

HedgeHog

Manny,

R U sure about that formula/calculation? I'm just curious as my tires rubbed quite badly (had to roll fenders) and dclin also posted a pix of the same issue. I run 245/40-18 on 18x8.5 on 42mm offset.

So, the calculation becomes:

(10.0/2) - 1.65 = 3.35 front space

10 - 3.35 = 6.65 back space

Based on Bridgestone/TireRack's spec of 10.0 section width.

What did I do incorrectly in the above calculation?

Oh..and when I turn the wheel lock to lock, the front part of the fender liner hits the tires. Granted my overall diameter is 0.81" taller than stock.

TIA.

2nd BTW, I was sure also that Max Cooper indicated a fitment clearance of 7.5" backspace , 48-50mm offset for his 18x10 CCW to run w/ 285/30-18 on the front w/o rubbing. Seems everything goes back to 50mm offset to clear.

SleepR1

No, our arithmetic is correct. I know because that's exactly what my setup yields except with 8.5 and 9.5 x 17! The only difference is my Hoosier racing R3S03 tires, in 245/45-17 and 275/40-17, are closer to stock tire heights (25.3 inches). Admittedly my front clearance is rather tight (at the left-front position), and it does rub very slightly (at the left-front position) AT FULL LOCK LEFT OR RIGHT.

Out on track I don't input full lock, unless I've got the turn completely wrong, and am desperately trying to save face with a huge dose of opposite lock! Luckily I was feeling like Michael Schumacher the last time I was out at Putnam Park; I had no fender rubbing experiences (with the tire--heaven forbid not with the wall or another car!) My FD is setup with very good roll control (Eibach Comp sway bars fr/rr, and H&R springs), so even at a perceived 1g+ of cornering (no real data to support that), there is no rubbing with my setup out on track.

I considered going with 225/45-17 and 245/40-17, as those Hoosier tire sizes have overall tire diameters of 24.5 inches. Much better for clearance, but clearly not as meaty. So I took the chance and have done ok with the wider and slightly taller Hoosiers!

Anyhow, that's what you and dclin did wrong--mounting too tall a tire. The 42 mm offset is correct, in that it provides clearance away from the fenderlip ASSUMING YOU HAVE STOCK HEIGHT TIRES. It should make sense that when you have 0.81 inches in excess height (dude that's almost a full inch!), that you WILL MOST DEFINITELY CONTACT THE RIMLIP and FENDERLINER.

This is one of the big reasons why this thread got so long in such a short time--deliberating about which front tire size that yields max width, but still stays within the stock tire height to assure adequate clearance from the fenderlip, fenderwell liner, and fenderliner bolt (especially that damned left-front position!).

Max and I had exchanged emails regarding his (and Steve Cirian's) track setup. You see, I was going that route too (CCWs), and had spoken with John Purner considerably. Purner says 10 x 18s with 285/30-18s will fit all around, using 2-inch offset, 7.5-inch backspace. I tried to verify this with Max Cooper and Steve Cirian--who both have this setup--and they said ONLY WITH 2.5-INCH COIL SPRINGS.

There's the key--2.5-inch outer diameter springs. The stock spring outer diameters are 4 inches. When we do the arithmetic we get (4 - 2.5)/2 = 0.75 inches more space, effectively creating 0.5 inches more coil spring clearance than stock. This is why the general rule for max back space for stock diameter springs is 7 inches up front, because you leave yourself 0.25 inches of CLEARANCE from the spring!

Now if you have 2.5-inch coil springs then your maximum backspace clearance is 7.5 inches. So let's do the math for 10 x 18 with 285/30-18 shall wee-wee

I keep the Hoosier Racing Tire specs close by for such occasions According to their table, the 285/30-18 tire tread width (not section width) is ~11 inches, and the overall tire diameter is 24.6. You see that the tire height is within stock range, so we don't worry about that parameter anymore.

So let's crunch numbers. Following the general rule of 3.5 inches of max front space and 7.5 inches of max back space (with 2.5 inch springs), we can check your 50 mm offset spec.

(11/2) - 2 = 3.5 front space

11 - 3.5 = 7.5

Voila! It all works ONLY with 2.5 inch coil springs.

Sadly I didn't have 2.5 springs, so I bought Rishie's SSR Comps, in 8.5 and 9.5 x 17 with 42 mm offsets, from Dreamin (Azeem).

That brings us full circle to your question.

Another round of espressos for everyone--I'm buying!

SleepR1

I'd like retract my last guess and reguess at 2 inches of offset. I'd forgotten that your mech/tech has the stock springs, thus his FD would be bound to the 7-inch spring clearance rule. With 2 inches of offset he put the extra half-inch toward the front space, thus yielding 3.5 inches (the maximum) of front space, and 7-inches of backspace (also the maximum). These specs are assuming an overall rim width of 10.5 inches (since 9.5 inches is the bead-to-bead measurement--and isn't useful for clearance calculations).

You guys might have noticed that I switch around and use overall rim width, overall tire section width, or tire tread widths for clearance measurements. It all really depends on information availability. Most tire specs only provide section widths, not tread widths. If you don't have access to tire specs, then you have to work off of overall rim widths. If you don't have exact specs for overall rim widths, you must guess that the overall rim width is one inch greater than the bead-to-bead rim width measurment.

Having the exact spec measurements is key in determining clearances, although you can make very good approximations if you make the right assumptions--engineers and scientists do this all the time

1FAST7

the highest offset for the 18x9.5 LE37T goes to 40.

1FAST7

1FAST7

I pretty much have 2 choices.

1) LE37T in 18x8.5 all around. With bridgestone potenza S-03 255/35-18 all around. keep the offset at 50??

2) LE37T 18x8.5 and 18x9.5. Bridgestone potenza s-03 235/40-18 for the fronts and 265/35-18 for rear. 40 offset fit on rear??

what do you guys think i should do. pick from one of these or do you have an better idea?

1FAST7

SleepR1

Option 2! Option 2!

Max Cooper has a similar setup except he has Volk SE37K in 17-inch diameters. He's running 245/40-17s up front and 265/40-17s in back. There shouldn't be any issues with the rear fitments using 40 mm offsets with a 9.5-inch wide wheel.

Now we need to hear from Rishie to see if these are available!

1FAST7

Thats good. Finally a answer to my problem..

what offset should be in the front and what offset should be in the rear?

1FAST7

SleepR1

40 mm for both the 8.5 and 9.5 x 18!

YAY!

:1party:

1FAST7

both front and rear tires equal 820 revs per mile. And they both equal 25.4" in diameter. Are these ok? 820 and 25.4"? because the stock is 24.8" in diameter. Will i have fender rubbing? thanks

1FAST7

HedgeHog

Thx for the clarification....now how the heck did they fit these on? Looks like stock fenders.


SIZE
F17-9.0J +32(H) 255/40-17
R17-9.5J +33(H) 255/40-17

Using, say Victoracer V700 @ 255/40-17 yields a section width of 10.6". 32mm offset = 1.26".

So, (10.6/2) - 1.26 = 4.04" frontspace
but
10.6 - 4.04 = 6.56" backspace!!!

I guess they must have an F1-styl push-rod swingarm suspension.

Ack! Still confused as to what to get for autox. Like Max had concluded, we're left w/ either a stagger set-up w/ brand names or CCW for 255/40-17 or 285/30-18 at all corners.

SleepR1

They rolled the front fenderlips and removed the fenderliner bolt. It's the only explanation I have!

1FAST7

will this work?

SleepR1

Of course there are no guarantees until you actually mount them up and see, but I can say this--Tire Rack's tire size and wheel size recommendations are notoriously conservative. This means they leave plenty of room for variation between tire maker and wheel maker specs. Honestly, I think you'll be fine. Just be careful going up your driveway curb with your wheel cranked all the way to the left, that's all!

1FAST7

would it be better with coilovers?

1FAST7

ARD T2

iTrader: (22)

If stuffing the wheel and tire further under the fender, I would say yes the coilovers will help. Also depends on what coilovers you go with. For the most part, all coilovers should have a smaller O.D. than the lower spring perch on yout existing struts.

Rishie

SleepR1

The revs/mile spec is about 2.4% off from stock, which means your speedometer might be off by a similar mount. This is neglible if you do the math.

An indicated speedometer reading of 65 mph will register 66.56 on you state trooper's radar gun. If your VA trooper has time to pull you over for doing 1.56 mph over the speed limit,-then s/he has way too much time on her/his hands. Seriously, I think they allow for a certain amount of speedometer error!

Happy New Year!

Flobb

This may be helpful for someone here. I didn't read all five pages though.

http://www.miata.net/garage/tirecalc.html

SleepR1

AND, you'll need the right wheel offset to take advantage of the increased back space clearance. This brings us back to the problem with Volks. Their offsets don't come very high in wide wheel widths.

You'll need to go custom (Forgeline, HRE, Fikse) and use a 2-inch offset (50.8 mm) to move the wheel/tire more inward toward the coil spring and away from the front fenderlips