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Its a very common misconception that going up in rim diameter will help "get rid of the gap".
When you go up in diameter you should also being going down in aspect ratio (sidewall thickness). This is to ensure that you keep the overall diameter of the wheel (rim with tire on) the same as the factory diameter.
Maintaining the factory diameter ensures that your speedometer as well as features like ABS/ TC/SC, etc work as the engineers intended.
The only proper way to eliminate the wheel gap is to lower the suspension.
Some people also do it the wrong way and go with a higher aspect ratio sidewall but this is the incorrect way to do it and will at the very least throw off your speedometer.
My car is done the proper way with 20x9 fronts with 245/30/20 and the rears are 21x12 with 325/25/21 tires lowered with the stock Z51 suspension collars turned down to the maximum.
What tire pressures do you run in the 20-21 setup?
Hey! Theoretically, it should be different because a few variables have changed. But since we don't know that formula, sticking to the factory recommended PSI should be within the margin of error because 20/21 with the same overall diameter is not that drastic of a change from stock. The TPMS might also be programmed to check for that PSI +/- some margin threshold.
Do you have any pictures of your car? (Side and profile to see the difference)
Here are a few pics. The front tires are perfectly flush with the front fender. The rear tires stick out about 1/4 in, which is exactly what I wanted. I know it's slightly aggressive for some but to me it's perfect.
More rubber on a sports car is not my taste, but if he likes it that is all that matters.
He went that way because it is the only way to get decent track tires....you don't find GT-based track tires in the low profiles required when using 20" plus tires...
@Semifighter18 Do you have any issues with the tire hitting the fender when the car compresses on bumps? Does the tire move inward at the top when the suspension compresses or something?
I'm working with HRE on a wheel/tire combo and they are saying the build would leave me with the rear "being dead flush with fender not including tire bulge" with the biggest offset they can create and they are not advising it. At first, I thought it would be a definite no-go based on that comment, but you are saying you've got a 1/4" that actually stick out on yours and it works?
@Semifighter18 Do you have any issues with the tire hitting the fender when the car compresses on bumps? Does the tire move inward at the top when the suspension compresses or something?
I'm working with HRE on a wheel/tire combo and they are saying the build would leave me with the rear "being dead flush with fender not including tire bulge" with the biggest offset they can create and they are not advising it. At first, I thought it would be a definite no-go based on that comment, but you are saying you've got a 1/4" that actually stick out on yours and it works?
I have 1100 miles on this setup and have had zero issues with the rear tires hitting the fenders. Caveat my comment with the fact that I'm not tracking it (I wouldn't have this setup if I was), it's a weekend canyon carver where I'm probably driving at 6/10s at most compared to track (I've done track days). I'll call it "spirited" driving, good pace but safe. With that said the roads I drive on are mountain twisties with lots of on camber turns so quite a bit of compression on the suspension.
There was a comment previously about the "correct" way to put 20/21" wheels on and the "incorrect" way, which is how I've done it. I won't comment on correct vs incorrect, but I understand the point. I personally can't stand wheels with the low profile tires, but that's a purely personal subjective opinion, to each his own. For my situation this was the easiest way to solve the wheel gap. As long as the ratio front to rear is close to stock there will be no issues with traction control, however it is true there will be an error in the speedometer (at 70mph it's a little more than 3mph). All I can say is to me the car now looks perfect, it runs flawlessly with zero issues (I did have to cut the mud guards so the front tires didn't rub) and being about a half inch taller is actually a good thing to me because I don't scrape the front splitter as much anymore. For others they wouldn't even consider doing what I did and that's their choice.
I'm a bit of an experimenter so who knows, down the road I might just get a set of lowering springs and go back to stock wheel size (though I'd have to have them flush with the fenders, being tucked in to me looks absolutely terrible).
someone has to have properly worked this out, by now. its well known on the c7 but for some reason no one wants wide rubber on the c8.
the correct way to handle wheel gap is to lower the car. even just a little makes quite a difference. so people can spend however much on wheels and tires but wont drop the few bucks on collars (especially for those with front lift) from paragon? heh.
no, no one should be concerned about the speedometer. who the hell cares, right? and the amount by which its off is never gonna be an actual problem. things like traction control however do matter. on the C7 a chief concern was the difference in diameter between front/rear.
the stock ps4s tires on a z51 c8 are 26.0" dia front, 27.4" diameter rear. keep in mind, the stock ps4s runflats are always juuuuuuust slightly larger diameter than all the non-runflats. so anyway, that means the rear is 5.3% larger than the front. put whatever donuts you guys want on your cars but you wanna make at least some effort to maintain that ratio between front/rear.
someone has to have properly worked this out, by now. its well known on the c7 but for some reason no one wants wide rubber on the c8.
the correct way to handle wheel gap is to lower the car. even just a little makes quite a difference. so people can spend however much on wheels and tires but wont drop the few bucks on collars (especially for those with front lift) from paragon? heh.
no, no one should be concerned about the speedometer. who the hell cares, right? and the amount by which its off is never gonna be an actual problem. things like traction control however do matter. on the C7 a chief concern was the difference in diameter between front/rear.
the stock ps4s tires on a z51 c8 are 26.0" dia front, 27.4" diameter rear. keep in mind, the stock ps4s runflats are always juuuuuuust slightly larger diameter than all the non-runflats. so anyway, that means the rear is 5.3% larger than the front. put whatever donuts you guys want on your cars but you wanna make at least some effort to maintain that ratio between front/rear.
Concur, which is why "tire size calculator" is such a great tool to use for something like this. I must have done 20 different calculations with different front/rear combos, comparing them to stock to maintain the same ratio. Worked out perfectly.......
Concur, which is why "tire size calculator" is such a great tool to use for something like this. I must have done 20 different calculations with different front/rear combos, comparing them to stock to maintain the same ratio. Worked out perfectly.......
yeah those calculators are great, so far i'm a little unclear on people running a 20" in the front. when ppl do it, they're still using a fairly skinny tire? 255 or whatever? because michelin lists their 285/25/20 ps4s as needing a 10.5 rim width which we know damn well wont work on the front =D
Its a very common misconception that going up in rim diameter will help "get rid of the gap".
When you go up in diameter you should also being going down in aspect ratio (sidewall thickness). This is to ensure that you keep the overall diameter of the wheel (rim with tire on) the same as the factory diameter.
Maintaining the factory diameter ensures that your speedometer as well as features like ABS/ TC/SC, etc work as the engineers intended.
The only proper way to eliminate the wheel gap is to lower the suspension.
Some people also do it the wrong way and go with a higher aspect ratio sidewall but this is the incorrect way to do it and will at the very least throw off your speedometer.
My car is done the proper way with 20x9 fronts with 245/30/20 and the rears are 21x12 with 325/25/21 tires lowered with the stock Z51 suspension collars turned down to the maximum.
Great looking Car and Thank you for your previous responses on other topics. I have a non z51 HTC; how much should I lower and what’s the approx cost for doing the same including any hardware required. Would really appreciate your feedback.
If you don't have the Z51 package and don't have mag ride you cant adjust your factory coils. You would have to buy lowering springs from Hyperco or Eibach.
10-17-2023, 04:39 PM
