Help me figure out what wheel sizes to order please?

[rennch]

Hi,

I'm about to put an order in for some Braid wheels, and I'm not sure how to correctly size them.

The car is an RSR clone. I have SC struts in the front, and original narrow body trailing arms.

Currently I have some 15 X 7, 15 X 8 Wheels on the car.

Rear wheels are 15 X 8, have a 54mm spacer, and are ET 11.

Fronts are 15 X 7, have a 27mm spacer, and are ET 23. (stamped on the wheel)

Here are pictures of my fender gap, which is perfect. So, I'd like to maintain that, and move inward. I have plenty of space inside my wheel wells.

Dog is ET 8 years old.






Any help greatly appreciated. I'd like to order tomorrow.

[JeremyD]

Originally Posted by Ferrino

Thanks for those pics Jeremy. According to my calculations:

9" front at 5.5" backspace = ET+12.7. With 22mm spacer = ET-9
11" front at 5.375" backspace = ET-15.8. With 18mm spacer = ET-33

Those values are closer to the backspacing of the original RSR 15x9/15x11 wheels (4 7/8" from my notes).

I have [17's] 9's and 11's

[rennch]

Jeremy...thanks for the answer. I'm pretty confused about this whole nonsense. Do the numbers you wrote apply to me?

[Pato911]

My favorite site/calculator for wheels and tires is here:
Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

P

[JeremyD]

Yes your car is very similar to mine. Wide body. SC/carrera suspension.

[rennch]

Pato, that looks great if i needed to figure out rim and tire size. I need to know what offset to order.

[rennch]

I have stock narrow body rear though

[JeremyD]

do you have aluminum trailing arms? Don't think there is any difference between narrow body and carrera/sc flared body except for the flares

[Bill Verburg]

Originally Posted by emptyo

Hi,

I'm about to put an order in for some Braid wheels, and I'm not sure how to correctly size them.

The car is an RSR clone. I have SC struts in the front, and original narrow body trailing arms.

Currently I have some 15 X 7, 15 X 8 Wheels on the car.

Rear wheels are 15 X 8, have a 54mm spacer, and are ET 11.

Fronts are 15 X 7, have a 27mm spacer, and are ET 23. (stamped on the wheel)

Here are pictures of my fender gap, which is perfect. So, I'd like to maintain that, and move inward. I have plenty of space inside my wheel wells.

Dog is ET 8 years old.






Any help greatly appreciated. I'd like to order tomorrow.

What you have now is
front 7ET -4
rear 8ET -43

to get wheels that have the outer lip where the existing wheel outer lips are you need
front 9 ET 21.4
rear 11 ET -4.9

tires will complicate it a bit as a 255 will hang out ~15mm more than a 225

Jeremy's is a good place to look, form my notes he has
9ET17.7 w/ a 4mm spacer for net ET13.7 w/ 255/40
11ET-8 w/ 315/35

If you like his fit you will like them on you car

to me the 7/8 w/ spacers pictured is too aggressive and sits too far out, especially so should you want to lower the car some.

[Bill Verburg]

Originally Posted by Pato911

My favorite site/calculator for wheels and tires is here:
Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

P

That site has one of the better calculators I've seen

[IROC]

Originally Posted by emptyo

I have stock narrow body rear though

It seems this important detail is being overlooked? I can't help with the required offsets, but it seems like you might be able to use 8s and 9s? Or maybe even 9s front and rear? I'm not sure what your performance goals are but 9s all around with 245s and 275s might be fun.

[Bill Verburg]

Originally Posted by IROC

It seems this important detail is being overlooked? I can't help with the required offsets, but it seems like you might be able to use 8s and 9s? Or maybe even 9s front and rear? I'm not sure what your performance goals are but 9s all around with 245s and 275s might be fun.

The picture and op show RSR body

[IROC]

Originally Posted by Bill Verburg

The picture and op show RSR body

Sorry. My reading comprehension stinks today...

[rennch]

I'm doing 15 X 9, 15 X 11 (original RSR) with Avon historic tires. So, they need to be spot on. My thought is that the rear spacers make up for the original narrow body trailing arms. When I go SC aluminum trailing arms, I'll have to eliminate the spacer, or get different widths I imagine. But I want to make sure I'm ok otherwise. I'm not sure I'm any closer to a solution just yet.

[Bill Verburg]

Originally Posted by emptyo

I'm doing 15 X 9, 15 X 11 (original RSR) with Avon historic tires. So, they need to be spot on. My thought is that the rear spacers make up for the original narrow body trailing arms. When I go SC aluminum trailing arms, I'll have to eliminate the spacer, or get different widths I imagine. But I want to make sure I'm ok otherwise. I'm not sure I'm any closer to a solution just yet.

Using SC aluminum trailing arms or the earlier steel makes no difference to wheel fit, using 930 aluminum however does make a difference, as these move the wheel outboard. I use to know buy how much but can't remember and can't find my notes on it either.

[KTL]

Ferrino & I have been discussing various wheel fitments via email. Tony recently mentioned the information he'd gathered indicates 930 trailing trailing arms are 22mm further outboard than typical 911 aluminum trailing arms.

[rennch]

Bill, are you saying they are essentially the same offset? For some reason, I thought SC arms were a bit more outboard.

Originally Posted by Bill Verburg

Using SC aluminum trailing arms or the earlier steel makes no difference to wheel fit, using 930 aluminum however does make a difference, as these move the wheel outboard. I use to know buy how much but can't remember and can't find my notes on it either.

[Bill Verburg]

Originally Posted by emptyo

Bill, are you saying they are essentially the same offset? For some reason, I thought SC arms were a bit more outboard.

yes, 911 steel and aluminum will place the wheels in the same place

930 aluminum moves the wheel outboard, WAG ~23mm

[bhmkv]

Your car looks great!!! I like the bbs wheels. Are you switching to Fuchs?

[kandhmfg]

Not sure if this helps or not, and everyone's car's like these are going to be a little different on the outside, but should be the same on the inside. BTW-love your car, looks great!

On my RSR racecar '71 chassis, alum SC/Carrera trailing arms, which is lowered significantly, but runs a fairly tall rear hoosier tire at 25.5" (front is 24.5"), I have found the wheels that setup the best for me, clearance wise/tire size wise are 8.5" fronts and 10" rears. These wheels are 2pc made up using the original 6" fuchs centers with a BBS bolt on outer, roughly a 5" backspace (Bill V. knows this by heart, these are 16" wheels), but you may be running the same 245/275 widths in a 15" tire I would guess? Or bigger? I also have a set of 3pc HRE fuchs in the same widths/setup with 5" backspace f/r 8.5F/10R. I don't know how to calculate ET, unless he is phoning home. Both provide ample clearance to inner oil lines and trailing arm bolts.

In the rear I run a 1/4" spacer, if I run a 1/2" spacer the tire will rub up inside the rear flare, but only when I am 3-wheeling...so you really have to push to get that to happen. Probably not going to happen in street conditions. I can squeeze a custom 9" in front, same backspace, but it is really tight on the outer flare lip. The outer edge of my tires sit much farther inboard than your pictures show.

For cars at such a light weight like ours (2200-2300lbs), I am not sure how much the delta is between a 275 tire and a bigger tire in the rear, but I can run faster than similar RSR type cars like ours with bigger motors and more horsepower and the same weight that are running a bigger tire package. Like, multiple seconds a lap faster and these drivers are not slouches. Maybe its a heat thing, easier to get the tires up to temp?

A couple photos for reference