cosm3os

I'm getting a set of the MPS4S this weekend to run the One Lap of America. I have Carerra sport wheels which I understand came stock with a 235/305 stagger. Should I go with that or 245s? Or 295s.

kisik

If you are not professional racer you will notice zero difference in any setup. Also it depends of your definition "best". Best for lap time (wrong tires), best for streetable track tire (probably wrong as well), best for track longevity (wrong tire again), best for street (may be but there is no history).
You want 9" front wheel to fully utilize 245 tire which I believe yours is only 8".

Just have fun on the track and beer after with your friends.

cosm3os

I'm not a professional, but I am NASA TT National Champ, and GTS National Rookie of the Year. So I have a pretty good idea what I'm doing on a track.

One Lap rules limit us to 200 treadwear tires, so "track tires" are out.

I specified that I have the Carerra Sports because they are wider (8.5/11.5).

Now that we have that out of the way, how about an answer to the question?😀. My concern of course is understeer. Usually, if it's good enough for Porsche, it's good enough for me, but like all manufacturers, I'm guessing they are erring on the side of safety.

Devil Boy

You could fit 245/305 easy on those size rims.

cosm3os

That's where I'm headed. Seems to me, if Porsche put 235/295 on all other rims, and then 235/305 (IE bigger stagger) more likely than not, they werent doing it to make it better balanced!

Devil Boy

I have OZ Ultraleggera 19x8.5 front and 19x11 rear and I'm currently running Bridgestones 245/35 and 305/35 with no problems. The shoulders are not stretched or bulging. Good fitment all around.

JCGMS

Is 245 a better match for 305 than 235?
Does it give you less understeer?

orange260z

I have the CS also. I don't think that you can run a 295 safely on the 11.5" CS rears, the max rim width for a 305 is 11.5". I find the 305 looks pretty stretched, and the tire shops have a hell of a time peeling them off the wheel.

I am curious on the feedback regarding the front sizing... I was wondering if people largely stayed stock, or if the car benefits from a 245. I know on my old 986 the stock front tire size used to cause a fair bit of understeer, which was resolved by sizing the tire up from a 205/50 to a 225/45.

StormRune

On my prior 997.2 I ended up using 245/305 MPSSes along with a increase in negative front camber to end up with a very good balance that worked quite well for me in autocross. The car also felt well-balanced at higher speeds as well. I assume that this year's Lap will include some autocross too.

cosm3os

After a long talk with Luke at Tire Rack, I went with the 245/305. Thanks guys. Gonna drive them awhile and test at Gateway in a couple weeks. I'll report back.

Petza914

See this chart that provides recommended tire widths for each rim width, including a min and max outside the recommended range.


A 305 width tire is an ideal fit for only an 11.5"-12" wide rim though you can use it on an 11". 235 or 245 on an 8.5" is also OK.

orange260z

Petza, thanks for this chart. Where is it from?

Not to argue, but I was going from Michelin's website, which said that the max rim width for the 305 PS2/MPSS was 11.5".

Petza914

It showed up in a google search for "tire wheel width chart" and was posted here - http://mechanics.stackexchange.com/q...im-width-chart

Here's another with the same info
https://www.clubpolo.co.uk/topic/282...m-width-table/

and another (post 7)
http://forum.mazda6club.com/mazda6-a...l-spacers.html

I actually haven't been able to find one that shows anything different.