So i have a few questions for those of you in the know. I have a set of 99 spec rims (8.5" x 17" rear ) and 8" x 17" front). i want to use a 255 on the "rear" rim, move that up front, and have the old 8" fronts widened to accomidate 275's in the rear for my 20b project car. So i had a couple questions.

The rim width range for the tire i want to use in the rear is 9"-11" optimal is 9.5". Theorecically i could have them widened from 8" to whatever i would like. Would i see any advantages from 11" rims VS 9" rims as far as contact patch/tire performance etc? or is it the case that as long as i meet the minimum rim width requirements everything is basically the same (as far as a particular 275's performance on either rim)?

If i use the minimum requirement for the 275's (9") then i need a net of 1" added to the rim. If I understand correctly, this will move my centerline and scrub radius. to counteract that, i take the additional 1" added behind the hub, divide by two (1/2") and add that amount to the front of the hub in the form of a spacer (1/2" = 12.7mm... so i assume a 10mm spacer would get me as close as i can get). First of all, is my reasoning correct? Secondly, would a 10mm spacer require longer wheel studs, or be spaced passed the existing hub-centric ring? Basically what would i need to do to remedy adding a spacer if anything.

Lastly, some car manufacturers actually exceed the specified limit for minimum rim width (BMW, Ford, etc have done this on stock cars). Would i be better off simply exceding the minimum rim width requirements and not messing with the wheels.... So, using a 255 (8.5" minimum) up front on an 8" rim, and 275 (9" minimum) in the back on a 8.5" rim?? Whatever I end up doing id like it to be the safest solution (aside from buying aftermarket rims )

thanks, Heath

 

Wheel widening adds width to the back side of the wheels, so yes, to maintain stock offset, add a spacer equal to half the added width. This is not guaranteed to fit, be sure to search for offsets that'll fit. Using a given tire on a wider wheel (within reason) will give you more grip and better feel. For a spacer above about 5mm you'll need longer studs and even below that, you're not guaranteed to be in the clear. Make sure you can get at least 8 full turns of the nuts or it's not safe. As a rule, hub centering rings don't work with spacers, so don't even bother, but then again you don't need them (just tighten the lugs with the wheel in the air and make sure the wheel centers properly). Lots of spacers are actually in inch sizes, so you should be able get exactly 1/2".

 

Ok the rear wheels are off to Weldcraft to be widened. Price is $200/wheel with a 2 week turnaround. while im waiting for them to return, i need to pick out spacers. since im lazy and dont want to mess with replacing wheel studs, im going to use bolt on spacers with new studs installed. these either come in 10mm or 15mm widths. I am trying to compensate for + 1/2" (half of 1" additional). .5" = 12.7mm basically right inbetween the 10mm and 15mm spacers... so im not sure which to choose.

 

go with 15mm

 

But make sure your wheels have a cavity between each lughole to absorb the extra 10mm of OEM studs that will protrude past the spacer.

Otherwise you'll end up cutting the studs on the spacer down.

If you need spacers hit me up.

Ichiba or KICS.

Rishie

 

so i put some washers on approximating 10 and 15mm spacers, and took some pics. i im not sure the 15mm will work as its puts the tire basically right on top of the fender, the 10mm one could cut it but then i lessen my margin of clearance in back (which im nearly out of). im having a hard time judging based off of some old 93 rims/tires. i suppose i could wait till i have the rims and tires in hand, but now im getting worried that this may end up being a big $1K mistake after factoring in the rear widening + tires if it doesnt work out . i can only get so close with my measurements, hopefully i didnt overlook anything important.

The tires im planning on using are the new-ish toyo R1-R in 275/17/40 for the rear. on a 9" rim toyo claims the overall width for that tire should be 10.55" . im hoping i made the right decision going down this path... im not so confident at the moment. ill post some pics of the mock up spacers -Heath

 

on a 10" Wide wheel with 275's for the FD you want to end up with a +45 to +50 offset ideally.

Based on information i've found the 99 spec wheel is a +50 offset front and rear.

If that's the case then:

You add 2" to the inside and you'll end up with:

10" +76 offset.

Just get a one inch studded spacer, SO EASY TO FIND and you're all set. Don't even need to worry about those cavities.

See how easy that was. If you put the offset info i would have given you the answer uber quick.

Thanks,
Rishie

 

Just measure your 8" wheel from outside to outside.

It should measure a total of 9" of "SPACING".

This means approx:

Front Spacing = 2.5"
Back Spacing = 6.5"
Origin = 4.5" = 9" div by 2

Deviation of 2" = 50mm of offset.

So when you send the wheels in make sure you indicate that you want a total of 8.5" of Backspacing, netting a total spacing of 11".

Since they are building onto rim halves it could be a matter of 0.5" in discrepancy if you don't lay it out like this.

You could be talking "Printed Width" they could be talking "Backspacing Width".

Regardless my 25mm spacer solution will solve the problem if they do it correctly.

Rishie

 

Rieshie,

can I be able to use: 17x9 and 17x10 + 25 offset all around ? with the stock fender and Tein Flex coilover??

i'm looking for BBS ( the one that look exactlly on the spirit R wheels )..and do u carry those?

 

Nope won't work.

Stock fenders require +45 offsets in those widths front and rear.

Rishie

 

so in order for it to work... what should i do? roll the fender? or ?

 

hey rishie, ok let me clear a few things up . ok stock 99 is stamped 50 front (8") and stamped 50 rear (8.5") if i remember correctly. to accomplish this on the stock 99 rear they added what seems to be 1/4" of material to the wheel face (basically a 1/4" spacer built into the wheel... (if you look at the front vs rear you can see the extra material), and the other 1/4" they added to the barrel. how its still +50 with a longer barrel i dont understand, but its stamped 50. either way, rears dont matter cause im moving them up front w/255's. The stock fronts are what are out to be modified.

The shop is adding 1" (25.4mm) back-spacing to the wheel. Adding that to the stock 50 i now have a +76 offset. To bring the centerline of the rim back into spec I divide the additional material by 2, and add that to the front of the rim in the form of a spacer. Half of 25.4mm is 12.7mm (not a common spacer). So i could choose either a 10mm or 15mm spacer. the rim alone will work with either size spacer and still clear all of the suspension hardware/fender etc... the problem comes in when i add tires.

toyo guestimated the overall width of the tires to be ~10.5" when mounted on a 9" rim. where exactly the tire will end up in relation to the various suspension pieces and fender im not quite sure yet (and not really sure how to accurately measure it out on the car). unless anyone has a clever method to measure out the various dimensions on the car i think ill just have to wait to get the rims back with the tires mounted, see where im at, and choose spacers then. from my mock up (with washers) of the two different spacers with a random buldgy stock FD tire/rim im definately going to need a fender roller for the 15mm.

 

You lost me on your math, it's a bit opposite of how I do things.

In any case, i'm just gonna give you 2 solutions. The one above was the best one.

Don't quote my Front spacing and Backspacing measurements here. In all honestly you'll need to add about 0.5" to either side for accurate total spacing of the wheel. Just hit me up privately if you still have the wheels in your possession so i can have you measure a few things for me. OR just bring them down to San Jose/Milpitas.

For reference purposes:
8" wheel
+50 offset
CENTER = 4"
FS = 2" FIXED variable
BS = 6"

1. Make 8" wheel 10" wide by adding 2" of more barrel to the inside.
FS = 2" FIXED variable
BS = 8"
CENTER = 5"
DELTA = 3" = 76mm
DESIRED OFFSET +50:

76-50 = 26, 25mm is good enough

2. Make 8" Wheel 9" wide by adding 1" of more barrel to the inside.
FS = 2" FIXED variable
BS = 7"
CENTER = 4.5"
DELTA = 2.5" = 63mm
DESIRED OFFSET +43
63-43 = 20mm is good to go.

If you specify the values above to them in terms of FS, BS, and Offset you'll get an exact fit to what you need. Please follow either formula and hit me up for the spacers to make it all work.

Rishie

 

money,

PM me please, keep this thread on topic for rotormotor.

Rishie

 

hey rishie, thank you. i commute from Oakland to San Jose every day (im going to grad school at SJSU now) so youre on my way . unfortunately the rims are in the mail to weldcraft, so ill have to wait till i get them back to bring them by. thanks for the help. -heath

PS The thing I'm not sure about with your calculations is that you are not taking into account the center-line of the wheel. To keep the wheels center-line where it normally would reside i divide my additional back spacing by two, and add that amount as a spacer for front spacing. Your calculations only take into consideration offset. does that create a wear problem? i was under the impression it did (i may be wrong).

 

OK sounds good, hopefully it all works out.

In my calculations you can see that i left the Outer barrel as a fixed value and only adjusted the Inner Barrel.

Once we have separate FS and BS values we can interpolate the resulting offset.

To bring the wheel back to the desired offset we simply use spacers. All I know is that my math is correct and will work depending on which route you go:

9" Wide wheel or 10" Wide wheel.

Once you get the wheels back i'll be able to tell ya exactly what you have and what offset.

Rishie

 

just spoke with weldcraft today... and paid for the wheels. they are done and on the way back to me in the mail now. ill update with some pics/measurements when they arrive

 

Another update, i just got the tires ordered and they will be here in a couple weeks. I settled on the new and somewhat un-proven Toyo R1R's. I hope it was an ok decision. anyway, ive got 255/40/17's coming for the front, and 275/40/17 for the rear. well see how everything works out soon. im a little nervous. -Heath

 

Those tires are very well proven in autocrossing.

 

And on the road course. They're excellent. You'll love the grip.

 

if they are predictable like the t1s then im happy plus i picked them cause they have a hundred dollar rebate going till the 31st... that was a big selling point lol

 

wheels are back. Id say that i was completely satisfied, welds look good and strong, but measuring it out, it did not come to a true +1" .... unfortunately its more like +7/8" on each wheel. it wont make much of a difference and i will compensate, but i expected a true +1" . they do however look rather strong. im a bit nervous to see how they balance out, but only time will tell (im still waiting on tires).

ill get some pics up in a bit

 

not a true +1" ->


so this is +7/8" = .875" /2 = .4375" = 11.1mm. So, that's a 10mm spacer for sure.... before i could have gone 10 or 15 cause it was in the middle.

 

They look great! i dint know some could have winded alum rims, i tought it was only for steal rims.

 

I'm here until nov 1 then going to LA to do some consulting. Let me know if you'd like me to do some tire mounting or measuring. I won't need your car to do that either.

Thanks,
Rishie