Hey guys,


should be an easy question that I haven't been able to find searching.


I am running on my G37S


20x9 +25
20x10.5 +15


I did have 245/35/20 front and 255/35/20 rear and that was cutting it real close. (rubbed a little in rear and very little up front)


I was thinking of getting new tires with 245/30/20 front and 255/30/20 rear to give a little clearance. I noticed however a lot of members run 245/35 up front and 255/20 rear. Is there a reason for that? I had a tire shop mention it to me as well?


Thanks guys!

 

Also based on the tire offset calculator, it seems like going with a 255/30 rear compared to 255/35 saves about an inch off the diameter overall. I also tried doing 275/30 compared against the 255/35 and my outer position stays the same but my diameter still drops .53. Does this mean I would be ok with going with a wider tire with lower height?

 

My car is dropped on Eibach springs and I'm running 20s with the same dimension as yours are. I have 245/35/20 I'm the fronts and 275/30/20 in the rear and never experienced any kind of rubbing issues at all so you should be fine as well with those sizes!

 

really 275 in the rear?! Im on coilovers so im assuming im running lower than you. I had 255/35 and could barley fit a CC between my wheel and fender

 

How low are you running the coil overs? Yeah the tire size I listed before might to to much a stretch for you if that's the case.

 

My tires tuck into the wheel well slightly. I have no camber arms so im running with just a slight camber.


is there a particular reason why you ran the 35 up front and 30 in the rear?

 

To be completely honest when I bought my wheels those were the tires that came with them lol I've never had any issues with rubbing or anything and I feel they look great as well

 

To keep the diameters consistent between front and rear, the profile in the rear needs to be lower than the profile in the front. For example, a common staggered tire set are 245/35 in the front and 275/30 or 285/30 in the rear. The wider tires in the back require the profile to be reduced compared to the front (30 vs 35) in order to maintain the same diameter. A 285/35 tire would be 1.12" taller (more than 4% difference) than a 285/30 tire, which in turn would also be about 4% taller than a 245/35 tire. In contrast, a 245/35 would have nearly the exact same diameter as a 285/30 tire. Hope this makes sense.


https://www.myg37.com/forums/tire_rim_calculator.php would help with figuring out size differences.

 

Thanks so much man that makes perfect sense! So now where I plan on running the tires so close 245/30 and 255/30 it comes to .24 difference .91%

I'm assuming that would be ok? Since I don't believe much wider than a 255 would fit in the rear.

 

That sounds like it would work! If you're AWD, you'd be cutting it a little close; the general rule of thumb would be to keep front and rear diameters within 1% of each other to prevent VDC from kicking in. With RWD the rule is 3%.

Also, a 245/30 has a pretty thin sidewall. With 19" wheels people generally run 245/40 and with 20" usually 245/35, but of course you can run whatever you want based on your needs/preference. But just putting it out there FWIW

 

Nice reply^^^^
If you only have a couple mm room to the fender about all you can do when running 255s (and no I wouldn't run an even further stretched 245 back there) would be to run a bit more camber to allow a bit more room, the rear camber/toe kit should be bought when lowered on coilovers (preferably the front & rear but at least the rear kit). Running real small series sidewalls can be done but your ride is already harsh, going down another series in sidewall height and the ride may be almost unbearable. It would be better to raise your coilovers a bit instead of going to even smaller sidewalls, that's what I'd recommend.
G/L