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Discussion Starter · #1 ·
Why would someone put 235 35 19 and 265 35 19 tires on a CS instead of 235 40 19 and 265 40 19 ? Any advantages or disadvantages?
 

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I bought 245/35r19, 275/35r19 for the track.

They are wider, shorter sidewall, and less circumference so you get a little more Torque out of them.
 

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Why would someone put 235 35 19 and 265 35 19 tires on a CS instead of 235 40 19 and 265 40 19 ? Any advantages or disadvantages?
The only difference in your example is the sidewall profile will be 5% lower than the 40s, so possibly a little harsher ride that may or may not be able to be detected. The front/rear rolling ratio is still maintained since both changed equally, so there shouldn't be any issues there. The speedo will be off just a bit though

It is possible to get the sidewall profile too low to the point that it just looks funny and the tire/wheel combo doesnt fill the wheel well as it should since typically the tire sidewall goes up as the rim size goes down and vice versa, but I wouldn't think that small change would cause that problem. The 35 profile is what comes on the 20" rims but that doesnt mean they cant be used on 19s. And as Big said, there is a small gain in mechanical torque though gearing on paper due to the smaller circumference, but I'm not sure if you would feel that or not?

One last thing that can become an issue with a lower sidewall profile is it can be easier to curb damage the rim if contact is made since you have less sidewall to protect it
 

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Discussion Starter · #4 ·
Ok guys thanks for the info, so I may go to the 40's to see if the ride improves.
 

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On the stock 981 suspension, you should be able to use these sizes on streets without an issue but cars equipped with the PASM and X73 already start out with a lower suspension that could create problems on poor roads. I used the 270/40/18--same height sidewall os the 265/35/19-- rears on a BS with the X73 and it worked fine at the track but the streets/driveway approaches were daunting.
 

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The 35 will give you less tire flex under cornering load, which of course means potentially higher g-force. Higher performance tires tend to have lower aspect ratios. That is one of many factors to consider.
 

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Discussion Starter · #7 ·
Ok guys I don't track the car so max performance is not needed, I would like a better ride if possible. I can live with the current 235 35 19 and 265 35 19 setup if I have to. Just trying to get the best option.
 

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Ok guys I don't track the car so max performance is not needed, I would like a better ride if possible. I can live with the current 235 35 19 and 265 35 19 setup if I have to. Just trying to get the best option.
The 35 series tires I have (Firestone Indy 500) give a ride that is noticeably harsher than the 40 series tires I have (Michelin PS4S).

Now, is it a lot harsher, I would say no, but it is noticeable.
 

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If ride comfort is your goal, a small increase in sidewall height is unlikley to get you there. Better options are lower tire pressure or buy a Lexus.
 

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My S came with Spyder 19' wheels. Factory spec is 235 35, 265 35. Michelin 4s tires ride great. Have PASM, stiffer ride with it on. Tracked with the wheels and tires, no issues. Moved to 18" wheels this year for track with track tires. 235 40's. Tires are different, no real difference in the ride.
 

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Porsche engineers spec'd the 35 vs 40. My guess is they know a bit more about tire performance and the CS performance target Porsche was trying to achieve.
 

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Porsche engineers spec'd the 35 vs 40. My guess is they know a bit more about tire performance and the CS performance target Porsche was trying to achieve.
Porsche spec'ed 40's on 19" rims and 35's on 20" rims. Both maintain nearly the same tire diameter.
 
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What? My 987.2 came from the factory with 35's on 19" rims.
The tire size was increased to a larger diameter on the 981 (265 40 19) from the 265 35 19 used on the 987. This was described in the 2013 Technik 981 introduction book as “new generation of tires with larger rolling circumference (+4%) and enhanced rolling comfort”.

Jim
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What? My 987.2 came from the factory with 35's on 19" rims.
This is a 981 forum question, not a 987 forum question. The 986 came with even smaller rims.
 
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