Upsize Tires from OEM

[jackliu0527]

I am currently running the crap oem 245/35/20 and 275/30/20 dunlop rfts, I am thinking about switching to non rfts such as pilot sport 4s as well i would like to upsize the sidewall to increase pothole resistance, so the size i am looking at is 245/40/20 and 275/35/20, so the diameter between the front and rear of the new tires will be the same, however it is a 1 percent total diameter increase from the old ones

So I would like to know, beside speedo errors which I can prob code it, would there be other issues such as tire pressure monitor system issues, tranny issues, transfer case issues, and another other issues?

As well has anyone here with up sizing experience they could share?

Thanks

[upstate650]

I would be a little nervous starting off with mismatched tire diameters. Fronts and rears wear very differently on these cars. My rears wear about twice as fast as the fronts, so at some point your diameter is going to be off a lot more than your 1% starting point, potentially causing damage to your x drive system Nothing else will be affected by this slight change.

[jackliu0527]

Stock Sizes
245/35/20 Diameter = 26.8"
275/30/20 Diameter = 26.5

Proposed New Size
245/40/20 Diameter = 27.7
275/35/20 Diameter = 27.6

If anything it made the front and rear closer in size no?

[upstate650]

Note sure where your tire diameters are coming from. Every tire is a little different. Go to tire rack, figure out which tire you want to run, and then you can look at the exact specs, including diameter and revolutions per mile. If the tire size you want to run is indeed a closer match than the stock tires then you have nothing to worry about.

I run 255/35/20 and 295/30/20 for summer. They are perfectly matched at 27" each :-)

[simmo3187]

I would be sticking with a 35 profile front and 30 rear

[Walt White Coupe]

I was thinking about doing a similar increase in tire diameter on 2013 650 coupe. I have standard 245/40/19 tires front and rear (square setup). So I was thinking about 245/45/19 all around. The rear is no problem but the fronts have to clear the front suspension piece that goes over the inside top of the tire. I had about 3/4 of an inch clearance with the stock tires and the 45's would have changed that to about 1/4 inch. I decided that that was too close and abandoned the idea. Something you should check first.

[jackliu0527]

Thats guys for your input

So I guess ill have to go with 245/35/20 + 275/30/20
Anyone have used non rft michelin pss or ps4s with those size? how are they to pothole resistance and ride comfort?

[PIR3lly]

Or just go a little wider, 255/35 front and 295/30 rear. It will also make the sidewall slightly thicker.

If however you are running the stock 9 inch rear wheels, 295 might me a little too wide...

I went from 19" Dunlop rft to 21" Michelin pss non-rft and the ride is so much better.
If you can, go for the newer ps4s, but the pss is still a great tire.