ok, i got it,

i talked to the guys at the tire co, 245's would fit on the stock 17" rims, and he said the looks might be different, but he said that 245/40 would definately fit on the rims.

 

That was the exact size I was hoping to put on the car next. I like my rims too much to change it all out.

Thanks for doing the research. Do you know how much the tire difference, if any, will have on the speedo readout. I guess I can go to tirerack.com and look it up myself. Man, this site will make you lazy sometimes. Thanks for all of the foot work.

Cheers!

Chef

 

Might do some good to talk to Tire Rack, Hartmann, or another tire/wheel expert about the sizing issue. My take so far is that 235/45 is about the biggest you'd want to put on those 17 x 7.5 wheels. Tire Rack has spec charts with the tire listing that note the nominal, minimum, and maximum wheel widths recommended for a particular tire size. As a general rule, we've found that nominal to max width rims give best perfromance on our 911's; getting too far from vertical on the sidewall comprimises performance, ride, and durability

 

225/235s are the ideal width on a 7.5" wide wheel. You can fit 245s on them and it will work, but you may be sacrificing performance by doing so by distorting the tires shape.

 

i agree with jackmott and hesaputz, you do sacrafice performance by going 245's, and they told me with the 245's, you'll actually be running at 65mph when the meter says 68mph,

but with 280lbs of torque, do you think 235's will help stick it to the ground?

 

It's another 1/3 - 1/2 " of rubber on the ground, and every bit helps. 235's are generally also about 1/3" taller, so they should up your speed about 1% above the speedo reading. Several manufacturers make a 235/40 - 17 that is fatter and shorter, but I don't have experience fitting or running these.

 

you will get WAY more benefit from having a nice soft tire compound in your current size than just going bigger with a similar tire compound.

Try some *good* 225s before adding weight and such with larger tires.

 

Okay on the good tires. I'm currently running Pirelli Rosso 225 45 17 which I would consider to be most excellent tires. Not sure what your point was in getting good rubber? These cars chipped need MORE quality rubber, which means increasing the amount of tread on the ground to help move the car with the added power.

Wondering what the increased percentage of contact surface is with each change of size? Maybe I can do some research to help this thread as well.

Chef

 

the guy i talked to says if you go 245/40's, it'll be about 1.25 inches extra in width on EACH tire, that's and extra 5 inches in width of contact, not considering the contact in length of the new tires.

chef, how bout you take one for the team and get the 245's for your 17's, then i'll go get my 18x9" rims with my 265's or even 275's. hee hee.

 

The guy you talked to is full of it. Look up tire spec charts at Tire rack, and look at actual tread width. Varies by brand, but it will be about half that or less over a 235.