Re: Tire sizes for urQ!? (longish)

[John Karasaki <johkar@teleport.com>]

I have run 225/45/16 tires on 16x8, 35mm offset 3 piece BBS wheels on the
urq ('82 without rolled fenders) for years without problems.  This is under
hard track use as well.

I have also used A8 wheels (16x7, 37mm offset) with 205/55/16 tires on and
off track on the same car.  This also is a good combination.

Several friends have tried the 225/50/16 tires on 16x8, 35mm offset 3 piece
BBS wheels on their urqs and had rubbing under spirited driving condtions.

BTW, our urq has the Eibach sport springs and koni shocks.





At 06:01 PM 1/18/99 -0600, Fluhr wrote:
>Richard,
>
>Here are some of my thoughts on that issue.  I have a 1982 urquattro
>with rolled rear fenders and I want to go to either 16" or 17" rims.  
>I have been very concerned about tire fitment, and so have done some
>calculations on it.
>
>>Calculated good combinations (right at the edge) end up as: 
>>
>>- - 225/50 16, ET 35
>> - same inside clearance as stock 206/60 15, ET 45
>> - 20mm closer to the fender
>> - 0.7% larger radius (in the noise)
>>
>>- - 225/45 17, ET 35
>> - same inside clearance as stock 206/60 15, ET 45
>> - 20mm closer to the fender
>> - 1.2% larger radius (still in the noise)
>>
>>In both cases this fit will be so close that variations in tire design will
>>make it or not, and rolled fenders may be needed to be sure.  Rolled
>>fenders seem to allow at least an extra 6 or 7 mm, which seems logical
>>looking at the lip.  In either case, going to a 215 tire and ET 40 wheel
>>should be a slam dunk, since that reduces the fender side increase from
>>20mm to 10mm.  
>
>
>The factory wheel is 15x6", ET45, with a 205/60-15 tire.  This means
>that the wheel extends 121.2mm into the car from the mounting face
>of the wheel, and 31.2mm out towards the fender. 
>
>To get an idea of fitment, I mounted the 5-spoke 16x7" ET45 wheel from
>the A4 on the rear of my urquattro, and it appeared to fit fine with 
>plenty of space with 205/55-16 tires.  Doing the calculations, this
>shows the wheel to extend 133.9mm into the car and 43.9mm towards the 
>fender.  Comparing it to the 15" rim, the 16" wheel extends 12.7mm
>(1/2 of an inch) further towards the inside of the car.
>
>So, now the question becomes, "What width 16 inch or 17 inch wheel
>and tire will fit under the urquattro's fenders?"
>
>Based on direct experience, 16x7" ET45 will fit with 205/55 tires.
>Since I only saw the wheel with 205/55 tires on it, I do not know
>if 225/50 tires will fit without rubbing on the inner suspension
>components.
>
>It seems commonly accepted that 16x7" ET35 and 16x7.5" ET35 will both
>fit the urquattro.  The 16x7" sounds reasonable, since the wheel is
>moving 22.7mm out toward the fender (and only 2.7mm inward), relative
>to the stock 15x6 wheels.  The 7.5" wheel is a bit more extreme,
>extending 29.05mm further towards the fender and 9.05mm further towards
>the inside.  I might feel more comfortable with an offset of 38mm for 
>a 7.5" wheel, since that would result in 133.25mm inner and 57.25mm 
>outer rim edges. 
>
>Now, the fellow who owned my urquattro before me used 16x8 wheels
>with an offset of ET35 and 225/50-16 tires.  From what I understand,
>this rubbed until he rolled the rear fenders.  Still, I would hesitate
>to use a 16x8 wheel unless I could verify that the offset would work
>with the tire I was using.  The 8" rim with a 35mm offset yields an
>inner extension of 136.6mm and an outer extension of 66.6mm. 
>
>As for 17" rims, I would expect them to fit similar to the 16" rims.
>Hence, an ET35 for 17x7" and 17x7.5" should work fine.  Now, 17x8
>may be a bit trickier.  Jeff Goggin and Ben Howell both seem to be
>OK with 17x8 ET35/33, but they are only running 215/45-17 tires
>rather than 225/45-17.  The 215 tire seems rather narrow for an 8"
>width rim, and I would be more inclined to use a 7.5" rim.  I would
>probably go with a greater offset (i.e. 38-40mm) if I planned on using
>a 225/45-17 tire on a 17x8 rim, if there was enough clearance on the
>inner suspension components.
>
>Personally, I would like to run 16x7.5 ET35/38 rims with 225/50 
>tires or 17x7.5 ET35/38 rims with 215/45 tires.  I know most TSW
>rims come in 16x7.5 sizes, but I do not know if any rims are
>available in 17x7.5 widths.  In that case, 17x7 may be the best
>choice for 17" with 215 tires.
>
>Later,
>Eric
>'85 CGT, '82 urq
>---
>Eric J. Fluhr                                Email:  ejfluhr@austin.ibm.com
>630FP Logic/Circuit Design                   Phone:  (512) 838-7589
>IBM Server Group                             Austin, TX
>
>
>
>
Best Regards,

John Karasaki