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Old 02-09-2009, 09:24 AM   #1
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Another Tire Conundrum

Last summer I decided to just run my MPSC track tires all the time as I was at the track every few weeks and thought it wasn't worth the swap back and forth each week.

After burning up the inside edge of 4 sets of rears from the daily commute I have decided that this year I will grab another set of rims with some street tires and put that extra effort in (of stopping my my mechanics for a coffee and rim swap) for each event. I was just going to grab some random set of rims in stock sizes, but I have the opportunity to grab a set of 996 rims for free from a family member who's car is going back off of lease.

The questions that come up are;

I have the choice of either set of rims on the car... some Porsche Sport Designs, or BBS LM's. (in 911 offsets, so I will be running spacers)

If I am going to keep using the stock rims and tire sizes for the track I should grab the sport designs for the street because I think they look far better on the car...

But

I could go to running 235 / 285 MPSC at the track, in which case the BBS's make more sense.

I worry that the 285's might be too much tire for the back of the car on the track... the balance of the 225 / 265 stock sizes works really well and I would hate to ruin that. On the other hand 285's are really easy to find around here... and more grip is more grip.

Is anyone running 235/285's at the track on their car?

What are the thoughts of the group?

Thanks
Marc

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Old 02-09-2009, 09:40 AM   #2
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Two sets of wheels is definitely the way to go if you run comp tires. The fastest Boxsters in SoCal right now run 285s all around. Some are running 245/285. Some very fast guys last year ran 245s all around to good effect. The plot thickens.
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Old 02-09-2009, 12:34 PM   #3
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I wonder if you are burning up the tires

because you are driving on the street or because your alignment is set for racing. It is quite possible to be within spec and be biased towards even wear or to be biased to max traction.

Trying to run the same alignment for both track and street makes compromises you at one venue or another.

I guess my suggestion is cheap long wearing tires for the street and leave the alignment alone.

But expect to replace street tires frequently.
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Old 02-09-2009, 01:07 PM   #4
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The tire wear is most definitely due to the aggressive alignment, big negative camber etc... it is great on track but hell on tire wear! Street tires at least have more tread to wear off.

In the off season I re-align the car to a street set up, but I leave it set for the track all summer.

Marc
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Old 02-12-2009, 08:54 AM   #5
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Typically "Toe in" burns up tires far faster than negative camber. Try a Zero Toe setup front and rear and see if you get more miles while retaining good aggressive negative camber. Also some guys who street their R comps will flip their tires on the rim every 2000 miles or so to extend their life. I think the Michelin Cup has a dedicated outside shoulder so you can't flip those. With Nittos and Toyos you can flip them for longer life.
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Old 02-12-2009, 06:28 PM   #6
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I run autocrosses (no DE's) so keep this in mind. I started running 225/255 Victoracers and found that the front still pushed a lot. I have since switched to 245/275 V710's and absolutely love them! Most of the front push is gone (what is left is me diving too deep into a corner and not the tires fault) and holy cow is there grip!!!

BTW-I run 17's for my r-compounds to save weight (and $$$). They aren't nearly as good looking as my 18's but that isn't the purpose of track tires/wheels.

BTW2-I have a 02' S with the only mod being lower stress bars, intake, and exhaust.

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