Important - DO NOT put 315's in rears!!!!
#1
Important - DO NOT put 315's in rears!!!!
Hi guys,
More to follow but my car is in the shop as I have an over heated front differential clutch. This is not the actuall clutch, but a clutch in the differential. (this showed up while looking for fault codes). It shows up on the computer as an overheated clutch.
Porsche is looking into this but the preliminary diagnosis is that it seems to be related to the height of the rear tire, in relation to front/rear tire size. The front tire height is the same as stock, the rears are an inch shorter, which seems to have burnt out the clutch in the front diff.. They are saying that difference can definitely burn the clutch and is not warrantable.
Therefore I am going back to stock tires sizes.
More to follow but you might want to hesitate on going with 315's at this moment.
Thanks!
More to follow but my car is in the shop as I have an over heated front differential clutch. This is not the actuall clutch, but a clutch in the differential. (this showed up while looking for fault codes). It shows up on the computer as an overheated clutch.
Porsche is looking into this but the preliminary diagnosis is that it seems to be related to the height of the rear tire, in relation to front/rear tire size. The front tire height is the same as stock, the rears are an inch shorter, which seems to have burnt out the clutch in the front diff.. They are saying that difference can definitely burn the clutch and is not warrantable.
Therefore I am going back to stock tires sizes.
More to follow but you might want to hesitate on going with 315's at this moment.
Thanks!
#3
Originally Posted by fredttx50
Hi guys,
The front tire height is the same as stock, the rears are an inch shorter, which seems to have burnt out the clutch in the front diff..
The front tire height is the same as stock, the rears are an inch shorter, which seems to have burnt out the clutch in the front diff..
#6
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Sorry to hear about that Fred. We had a 997TT here in the shop a few weeks ago with 315's. Todd spent all day on the dyno pulling his hair out with the car. It was 100% stock and we wanted to get a baseline number on it before we upgraded him with our new EVT6XX system. The car had major power fluctuations throughout the <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-comtuning</SPAN></st1:PersonName><font color=" /><st1:stockticker><FONT color=black><st1:stockticker>RPM</st1:stockticker><FONT color=black></st1:stockticker> range and acted it very strange. We then thought that maybe the tires were causing the PTM to freak out so we installed the stock wheels and the problem went away.
<FONT color=black>The rolling diameter is different enough to cause the traction management to freak out. Also, we noticed that on the street the car would "hunt" and pull to the left and right under acceleration. This is a major problem as Fred has experienced first hand. Hopefully you can convince the dealer to take care of it for you. Keep us posted<O</O
<O</O
Sorry to hear about that Fred. We had a 997TT here in the shop a few weeks ago with 315's. Todd spent all day on the dyno pulling his hair out with the car. It was 100% stock and we wanted to get a baseline number on it before we upgraded him with our new EVT6XX system. The car had major power fluctuations throughout the <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-comtuning</SPAN></st1:PersonName><font color=" /><st1:stockticker><FONT color=black><st1:stockticker>RPM</st1:stockticker><FONT color=black></st1:stockticker> range and acted it very strange. We then thought that maybe the tires were causing the PTM to freak out so we installed the stock wheels and the problem went away.
<FONT color=black>The rolling diameter is different enough to cause the traction management to freak out. Also, we noticed that on the street the car would "hunt" and pull to the left and right under acceleration. This is a major problem as Fred has experienced first hand. Hopefully you can convince the dealer to take care of it for you. Keep us posted<O</O
<O</O
Last edited by Nate@EVO; 03-11-2007 at 12:46 PM.
#7
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#8
As well, due to the tires in the rear being too large, I was getting the PTM warning on the dash. " PTM briefly inactive - too hot " . It appears and goes away all the time!
#12
As a general rule, you want to keep your tire rotational speed identical to the stock speed, and in effect proportionally stock tire height for the front and rear wheels. If you don't, the difference in tire circumference and hence wheel speed will quickly start roasting diffs.
The width of the tire doesn't matter. The overall height of the tire does. You can run 315/25/19 rear tires just fine, but you will need to size the front ones appropriately. I believe the closest you could get with commonly available tire sizes in 19" would be a 265/30/19 in the front. It would still be slightly slower than the stock front wheel speed, but much less so than 315's and 235's.
Alternatively, you could just rip the AWD system out and run whatever you want.
The width of the tire doesn't matter. The overall height of the tire does. You can run 315/25/19 rear tires just fine, but you will need to size the front ones appropriately. I believe the closest you could get with commonly available tire sizes in 19" would be a 265/30/19 in the front. It would still be slightly slower than the stock front wheel speed, but much less so than 315's and 235's.
Alternatively, you could just rip the AWD system out and run whatever you want.