New guy ... more questions ... wheels and offsets

Discussion on wheel & tire issues
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Bowtie Junkman
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New guy ... more questions ... wheels and offsets

Post by Bowtie Junkman »

OK ... looking to move up to 20"s ... hoping to run around a 245/45 and 275/40 combo ...

I found a nice set on local CL ... 20x8.5 and 20x10 with 245/45 & 275/40 .. all are offset +35

BUT ... I believe I read that offset 35 will cause them to "stick out" too far .... thus also causing problems when I lower the car later (probably with Eibach or H&R springs) ...

I also found a set of 20x9 American Racing wheels that are offset +40, which I understand will fit much better ....

BUT ... then again ... I believe most of the fitment info I've been getting are related to a G8 or Super Sport ...

SO ... once again I rely on the experts for guidance ... are the wheel openings or wheel-wells on our cars more "forgiving" than a Camaro, G8 and/or Super Sport ... thus allowing for a different offset .... or should I stick with the tried and true +40 or +45 to be safe ... ???

Thanks in advance ...

The Junkman
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GTObert
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Re: New guy ... more questions ... wheels and offsets

Post by GTObert »

245/45 is just too big. The tire will rub and it's way too close to the front bumper to even look good anyway. I have Camaro wheels which are 35 offset in the front and I think 40 in the rear. With the right size tire it's not an issue. They don't stick out at all.
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bsparks72
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Re: New guy ... more questions ... wheels and offsets

Post by bsparks72 »

I will agree that 245/45/20 is too big (tall) for the front. When I got my car, the tires had been replaced with 245/55/18 RSAs on stock wheels. Those have a 28.61 overall tire diameter. The front tires rubbed on the struts where the spring sits. And I don't mean a little...it ruined the tires quickly. I ditched the ruined 2, sold the other 2 and put stock size tires back on. Go look at your car stock, and see how little room there is between the front tires and the struts where the spring pocket is. I'd say anything over about 28" diameter is getting close to rubbing.

A 245/45/20 has an overall diameter of 28.68, which is slightly taller than what I had. No way that will work. You either need a 245/40/20 on the front, or a 255/35/20 - which oddly enough is less expenive tire to tire in a lot of cases. The 245/40/20 is slightly taller than the stock 235/50/18, and the 255/35/20 is slightly shorter than stock.

As for the rear, a 275/35/20 is closer to the stock overall tire diameter than a 275/40/20 is. I have stock Camaro 20s in the garage. I plan on trying 255/35/20 front, and 275/35/20 rear. If you want to do tire comparisons, this is among the friendlier tire calculators I've found:

https://www.tacomaworld.com/tirecalc" onclick="window.open(this.href);return false;
-Brandon
2012 9C1 L77 - 228/234, .604/.609 112 cam, JBA shorty headers, Solo high-flow cats, X-pipe, Cherry Bomb single-chamber mufflers (Frankenstein exhaust), Roto-Fab CAI, CTS-V torque converter, 3.45 Camaro diff, G8 red/black seats/steering wheel
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Bowtie Junkman
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Re: New guy ... more questions ... wheels and offsets

Post by Bowtie Junkman »

Thanks for the help guys ... seems I was on the right track, but slightly off on my aspect ratio ....

SO ... lowered slightly with a 245/35 front and 275/30 rear ... what wheel offsets would you recommend? At least +40 all around, or try for +40 front and +45 rear?
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GTObert
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Re: New guy ... more questions ... wheels and offsets

Post by GTObert »

The problem is finding matching sets of decent tires in all those sizes. 245/35/20 and 275/30/20 gives you a couple options and is almost exactly the same as stock height. I went with the Continental DSW and it's a really nice tire. There's almost no road noise, they do well in rain and snow, and the treadwear is pretty good for a performance tire. I simply won't run Falkens or similar junk tires.
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GTObert
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Re: New guy ... more questions ... wheels and offsets

Post by GTObert »

A 35 offset does work in the front and in my opinion looks better than a higher offset. If you're going with a 8.5" wheel I'd say keep it at 35 so you don't contact the strut or the fender liner. The rear is fine with a 40.
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CrashTestDummy
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Re: New guy ... more questions ... wheels and offsets

Post by CrashTestDummy »

Do aftermarket coil-overs provide some needed space? Just wondering, as it seems most of the aftermarket coil-overs use coil-over springs at least for the front struts, but I haven't been under that end of the car yet to see for myself.
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bsparks72
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Re: New guy ... more questions ... wheels and offsets

Post by bsparks72 »

245/35/20 in the front is too short of a tire, and 275/30/20 for the rear is also too short. Use the calculator link I posted to see the overall tire diameter vs. the stock 235/50/18.

Stock tire diameter is 27.25".

For the front, a 245/40/20 is close at 27.72". A 245/35/20 is 26.75", which is too short and will look weird...and probably ride really rough.

Also for the front, a 255/35/20 is 27.03", but is a tad on the short side. The bonus there is some of the tires in that size are considerably cheaper than the 245/40/20.

For the rear, a 275/35/20 is close at 27.58". A 275/30/20 is 26.5", which again is too short.

You can find plenty of tires in all 3 of those sizes.
-Brandon
2012 9C1 L77 - 228/234, .604/.609 112 cam, JBA shorty headers, Solo high-flow cats, X-pipe, Cherry Bomb single-chamber mufflers (Frankenstein exhaust), Roto-Fab CAI, CTS-V torque converter, 3.45 Camaro diff, G8 red/black seats/steering wheel
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GTObert
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Re: New guy ... more questions ... wheels and offsets

Post by GTObert »

My tires don't look too short and they ride just fine. Do whatever you want, but you're talking about fractions of an inch that you really can't see. A 245/40 is 1.5% taller than stock and a 245/35 is 1.8% shorter. If you can tell then you have a sharper eye than I. You may have a point with the rears, but again it's all about what tires you can get in those sizes. I don't want another car with 15,000 mile tires, one is enough. Of course you could go 245/40 and 275/35 and get the same Continentals I did. I just went a touch conservative because I didn't want to risk rubbing and ruining $1000 of tires. If anyone does do this and it works let me know.
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bsparks72
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Re: New guy ... more questions ... wheels and offsets

Post by bsparks72 »

I understand what you're saying. And if the car is lowered accordingly, it will make up for any gap a shorter tire may have. I have no problem with it, and might not be able to tell. I would just try to stay as close to stock diameter for speedometer accuracy, shift points, etc. In the end, it probably wouldn't matter much anyway. One of the reasons I haven't bought tires yet is because I don't want to ruin my good ride, and risk having tire/wheel damage from crappy streets. Mine gets 70+ miles a day on it, so I have plenty of opportunity to have a problem.
-Brandon
2012 9C1 L77 - 228/234, .604/.609 112 cam, JBA shorty headers, Solo high-flow cats, X-pipe, Cherry Bomb single-chamber mufflers (Frankenstein exhaust), Roto-Fab CAI, CTS-V torque converter, 3.45 Camaro diff, G8 red/black seats/steering wheel
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