Messing around with tire/wheel sizing

[TypeRbuilder]

Sooo! Just picked up the CTR and looking to upgrade the wheels/tires soon. However it'll take me weeks of messing around with a few programs I use to dial it in. So this is a "thought process" thread. Just like the one I did for the TLX Type S a few years back when making those wheels!

With that car: 255/35-20 tires on a 20x9 rim, I wanted it more aggressive WITHOUT spacers. So the first thing I did was slap as set of 275's on the factory lightweight rims and...oooo! Filled the gap nicely as it brought the sidewalls more UPRIGHT. So the immediate need to drop the car was held off for a bit...looked much better than the factory look.

Then: Made the first set of forged alloys: 9.5 wide x 20, with a 275/35-20 tire. Offset went from 52 to 47. Much better, brough it CLOSE to the edge of the fender and filled the gap nicely. Then the car got dropped 1" and that made a huge difference as well!

Then? Made a set of 10" wide rims, with a 43 offset, wanting to keep the same inside clearance. Tires: 285/35-20. PERFECTION! Just at the edge of the fender, super wide looking tires and drove awesome!! Just the perfect look and ride!


So onto the CTR: I'm putting a set of 275/35-19 Vredestein ultra high perf all season's on it for the winter as I deal with new rims: 18".

Preliminary work is heading toward a 10x18 rim, in a 53 offset (vs 60). This will keep the back spacing the same as stock, but bring the tire 13.5mm further out, which should be perfect. I have a set of 5mm spacers on now and that's looks better for as little as it is. So 13.5 will be right where I want it without going "past" that fender. The tire will be a 275/35-18 to square up nicely on top of that. So when DO lower the car .8-1" it will sit even more where I need it to without the threat of hitting the fender as it'll barely be back from that edge!

Phew......wish me luck and keep you posted! First step is getting the taller tires on tomorrow to see how the theory is going to work in real life

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[optronix]

Interesting why the wider wheel and narrower offset. I think through the community trial and error, lots of folks seem to land on 19 x 9.5 +45 for the "mild" fitment option, and 18 x10 +40 for a more aggressive fitment paired with the drop to 18s for more tire options and rim protection/comfort for nastier roads. The latter 18 x10 +40 option has been dubbed the "god spec", and there are several threads on that wheel fitment alone.

All that being said, I think there's still a gap for those who want to remain in street class autocross. The wheel has to remain the same width but can gain or lose an inch of diameter- but the offset has to remain within 7mm of factory, which is why +53 jumped out to me. I think there's a growing market for this fitment option, but the extra wheel width would make this move obsolete for these folks.

So I'm curious- what's the benefit of the added wheel width if not for performance reasons? Aesthetically you can get the same result with a few more mm of offset. I guess it doesn't REALLY matter, but assuming you're building something from scratch (which would be some welcome context- not all of us have the ability to "make" sets of wheels at our own discretion...) and you're soliciting opinions, mine is that if there are already tons of wheel options available, why literally "reinvent the wheel" with a width/offset combination that the community hasn't already vetted extensively?

 

[TypeRbuilder]

It's more cost effective to make my own. And I can tweak it mm by mm. I like a WIDE wheel/stance, and when I hit the track, the less the tire 'rolls' the better. Wider wheels give me better grip than the same size tire w/narrower wheels.

 

[MvV]

just for visual reference, and much more inline with @optronix comments, Apex EC-7 18x9.5" ET43 Wheels with 265/35 R18 Bridgestone ExtremeContact DWS06+ A/S tires(no spacers, stock suspension)

 

[TypeRbuilder]

Nice....but it does stick out a bit too far for my taste. That's why the 53 should pull that in JUST ENOUGH! Also when I get the 275/35 19's on there tomorrow...that should look good on the stock wheels/5mm spacers and filling that gap a bit more!!

 

[MvV]

Nice....but it does stick out a bit too far for my taste. That's why the 53 should pull that in JUST ENOUGH! Also when I get the 275/35 19's on there tomorrow...that should look good on the stock wheels/5mm spacers and filling that gap a bit more!!

I think the difference will be 5mm? my setup is pretty much flush, either way show some pictures of your work, sounds intriguing!

 

[TypeRbuilder]

I think the difference will be 5mm? my setup is pretty much flush, either way show some pictures of your work, sounds intriguing!

Absolutely! Will keep all posted!

 

[MvV]

that's fast !! I like it !! I was hoping for some "raw" pictures of how you go buy creating these wheels what sort of shop do you work for or own to be able to create your own ?
here's something that's been bothering me on my FL5: the gap between wheel arches and top of tire on the rear is quite uneven on my 2025 FL5, difference being 1/2" easily, how is this on yours ?
how about a picture from the side

 

[TypeRbuilder]

That looks good!

that's fast !! I like it !! I was hoping for some "raw" pictures of how you go buy creating these wheels what sort of shop do you work for or own to be able to create your own ?
here's something that's been bothering me on my FL5: the gap between wheel arches and top of tire on the rear is quite uneven on my 2025 FL5, difference being 1/2" easily, how is this on yours ?
how about a picture from the side

Haha. In due time. I do kind of have a part-time shop. And work with a lot of companies on a lot of development stuff like paragon brakes, and planted tech technologies.

actually, working on a grounding kit now for the car. But I’ll keep you posted on the rest. It’ll be a while before I get the exact sizing on the wheels and have them made so I’ll keep everybody posted.

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