Leicht

any precaution if I install there for the front tyres but with 275/35/20 on the rears? Can't find any much info on the web for the 981.

My front 20 inch Carrera sport rims is 8.5x20 ET 57.

Thanks.

PorscheAddict

No problem with 255/275 generally, provided the 255 fits up front. That's right on the edge of what'll fit stock, but I can't confirm either way.

Voyager6

I have tried 255/35-19 on my 14 Cayman, The car has Bilstein Damptronics with coil over modification and the 255 rubbed at extreme steering lock. 20" rims may give you a bit more clearance to the springs, but the only way to know is to try. It will likely require spacers to get things right,

V6

Leicht

Leicht

storii

I run 245/35-20 in front on 8.5x20 ET57 wheel with no issue. The rear is 275/35-20 on 10x20 ET50.

Leicht

PorscheAddict

255/275 will have slightly less understeer or more oversteer than 245/275 by virtue of having more front grip. That difference won't be material if you aren't tracking (I hope )

ghartke

My 2014 MT CS (bought used with 6800 miles on the clock) came with 20" Sport Technos, 255/35-20's on the front, and 285/35-20's on the rear. (P-zeros all around.) Never noticed any trouble. That was also my first season AXing the car, but I was limited by lack of grip from the tires, so the next season I switched to RE-71Rs in 245 and 285 sizes. (Bridgestone doesn't make that tire in 255/35-20.) I worried about the "unbalanced" setup with the new tires giving me too much understeer, but I've been very successful campaigning the car in PCA AX events (14 or so events per year), so really can't complain.

I'm unable to give a comparison of grip levels for the 255s vs 245s because the car with the original tires had sat out on the dealer's lot all winter before I bought it and no matter what we may say about P-zeros, that made it an unfair comparison. Next spring I'll be on my 3rd set of RE-71Rs in the sizes I stated and while I still wish I had 255s on the front, I'm content for now with the 245s.

Regards,

Greg

storii

Let us all remember that, for the 981S, the stock tire sizes for 20" rims are F235/35-20 & R265/35-20. The front-to-rear ratio in this size is 0.8868:1. This is what Porsche intended for street use and I tried not to differ too much from this ratio when I upsized my tires because I didn't want to change the handling characteristics too much. I also wanted to limit the increase of the overall diameter to absolute minimum. I wanted to upsize the tires because I changed the wheels from 8x20 ET57/9.5x20 ET45 to 8.5x20 ET57/10x20 ET50. The stock 235/265 looked too skinny on the wider wheels. The following are the front/rear ratio of the sizes discussed in this thread so far:

• 235/265 (stock) 0.8868:1
• 245/275 0.8909:1
• 255/275 0.9273:1
• 245/285 0.8596:1
• 255/285 0.8947:1

You can see why I settled with the 245/275 combo. I could have done 255/285, but I thought this combo would increase the overall diameter too much. After the switch, I didn't notice any change in the handling characteristics from stock at all. I think I would have noticed slightly more oversteer if I went with 255/275 and understeer with 245/285. So, for street use, if one wishes to maintain the stock handling characteristics, I recommend one would stay close to the stock front/rear ratio. Obviously, for track and autocross, one can purposefully change the handling characteristics by changing the tire sizes, air pressure, suspension settings, etc., etc.

Leicht

Dicknose