Thoughts on going to a wider rear tire?

[SVTHorsnake]

I just rolled 11,000 miles and it seems my rear tires are ready to be changed. Apparently, I didn't do too bad. Most people say they don't last 8,000 miles.

Regardless, it comes with 305's stock. I'm thinking about going to 315's or even 325's in the rear. Is there an engineering reason not to do this? It seems like the 305's are a little narrow, the sidewall bows a little. Is this technically deliberate?

Will it also add to the oversteer these cars are supposedly known for (although I've never felt it, if anything I've felt oversteer)

Also, is there a different tire I should consider than the factory Michelin and why?

Thoughts?

PS: Thanks for all the consistent input. I will contribute very soon with a DIY V1 install WITHOUT cutting or perminantly altering a single oem part, a DIY for tinting the corners and 3rd brake light, again, with tint that can be pulled, and spacing the rear spoiler, the first 2 of which have already been done on my car.

Edited May 6, 2008 by SVTHorsnake

[PAULSPEED]

Hi,

You might have a problem finding anything bigger then a 305. I

saw a 325 but it was a racing tire. Let us know what you find.

Paul

[berty987]

To keep the same rolling radius you will need the same sidewall height , even though the aspect ratio will need to decrease , so i'm not sure why you think a wider tyre will give less tyre bulge, or what benefit. On the reports I've seen for Techart and Gemballa tuned cars which genuinely need wider rear tyres thanks to significant power upgrades, the consensus is that a wider tyre actually hinders cornering and handling. Ultimately its your choice , but the wisdom of the motoring press would suggest that a wider tyre will give limited improvements and upset the front/ rear balance of the car. A better grade of tyre or a track orientated tyre will probably give better results than just stepping up the width , the "set up" of the suspension geometry is also key to the under/ over steer characteristics.

Edited May 7, 2008 by berty987

[PAULSPEED]

Hi,

I went looking on tirerack yesterday.

www.tirerack.com

There are wider tires then 305 but not the same aspect ratio. The

rear tires on my 997 S are 305/30/19. Good luck

finding wider street tires.

Paul

[jhbrennan]

I just rolled 11,000 miles and it seems my rear tires are ready to be changed. Apparently, I didn't do too bad. Most people say they don't last 8,000 miles.

Regardless, it comes with 305's stock. I'm thinking about going to 315's or even 325's in the rear. Is there an engineering reason not to do this? It seems like the 305's are a little narrow, the sidewall bows a little. Is this technically deliberate?

Will it also add to the oversteer these cars are supposedly known for (although I've never felt it, if anything I've felt oversteer)

Also, is there a different tire I should consider than the factory Michelin and why?

Thoughts?

PS: Thanks for all the consistent input. I will contribute very soon with a DIY V1 install WITHOUT cutting or perminantly altering a single oem part, a DIY for tinting the corners and 3rd brake light, again, with tint that can be pulled, and spacing the rear spoiler, the first 2 of which have already been done on my car.

If you get the front and rear sizes too out of whack you may burn out the AWD differential.

[SVTHorsnake]

ok people. Take it easy. Remember that a 1 to 2 mm difference is the same as the wear difference between the front and rear tires and won't make a notable difference for either the speedometer or the center differential.

I'm simply asking if there is a reason Porsche chose a 305 mm contact patch or if I can go wider.

[PAULSPEED]

Hi,

I think Porsche chose the 305 tire because it was the biggest high

performance tire at the time. Did you find a wider tire?

Paul

[SVTHorsnake]

Hi,

I think Porsche chose the 305 tire because it was the biggest high

performance tire at the time. Did you find a wider tire?

Paul

I know there are up to 335s available in 18" sizes but I don't know about the 19"s. I'll do some digging and post my results when I get away from work later today.

[PAULSPEED]

Hi,

I would sure like to know who makes a 335 in a 18 inch tire. I saw

a 325 but it was a racing tire not made for the street.

Paul

[JotaEmE]

The wider you go, the clumsier it will get.

If it's esthetics what you're after, ok then, however if you think you'll get a better response, I'd think it twice.

Your choice.

JM

[R Young]

I bought a set of new take off Carrera 4S rims and Pirelli Rosso tires, 295's in the back. The car had a noticeable understeer. I put the original rims and 305's back on and was surprised at how much better it handled. I am surprised how 10mm width in the rear tires had such a dramatic effect. I would not go with wider tires.

[SVTHorsnake]

I bought a set of new take off Carrera 4S rims and Pirelli Rosso tires, 295's in the back. The car had a noticeable understeer. I put the original rims and 305's back on and was surprised at how much better it handled. I am surprised how 10mm width in the rear tires had such a dramatic effect. I would not go with wider tires.

sorry for the late reply. first a little background.

Car: 2001 Mustang Cobra (about a year ago)

I went to a 315 in the rear, from a 275, while maintaining 275s in the front. As people predicted here, the car began understeering.

Car:2007 997 TT

I kept the stock 235s in the front and bought some 325 PilotSport Cups (DOT, stock 997 GT2 tires) with an 80 treadwear rating. This past Saturday, I took it to a GT Live event at Miller Motorsports park. Outcome: no noticable oversteer increase (although I might not be a good enough driver to push its thresholds) and, when I turned PSM off, and activated the stiffer suspension setting, it would oversteer under throttle blips.

Verdict: I was very satisfied with this tire combination. Traction was greatly improved over my last runs (as defined by an average of .75 to 1 second faster times on a 2 minute average course), although, the last time I ran on the stock 305's it was about 5 degree F colder)

My next move: I will mount PilotSport Cups on the front and report back soon.

Thoughts?

Edited July 2, 2008 by SVTHorsnake