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Tire threads showing on inner rear - tire pressure of 42 psi too high?
Recently looked under the car and noticed the rear right tire is showing threads right on the edge of the tire, not showing on the left rear but probably means I take a lot more right turns. I find this interesting as there's still a little bit of tire thread. I checked the tire pressure and both rears are at 42 psi (fronts are 35 psi) measured undriven in 55 degree temp.
Does this indicate that the tire pressure is too high? I've already ordered a new set of tires but they're backordered so ideally want to make these last for about two more weeks. Would it make sense to reduce the pressure to something like 37 psi? Would it matter at this point?
this. i've run up to 44 in the rears before during my earlier years of ownership - no issues (but the ride definitely felt stiffer)
Originally Posted by LexVan
Speaks more to your alignment.
How many mikes on this set?
Back your tire pressures down to about 38. Don't let them go over 40 hot for best performance and comfort.
That's the common wisdom. Too much negative toe is the culprit. But... if one is not a smooth driver, keep the negative toe and pay the price for tires.
That's the common wisdom. Too much negative toe is the culprit. But... if one is not a smooth driver, keep the negative toe and pay the price for tires.
This.
High tire pressure balloons out the center of the tread and protects the edges.
When commuting or driving distances on freeways I'll go to 42 psi cold (ambient temp compensated). This accomplishes higher mpg and longer tire life.
Recently looked under the car and noticed the rear right tire is showing threads right on the edge of the tire, not showing on the left rear but probably means I take a lot more right turns. I find this interesting as there's still a little bit of tire thread. I checked the tire pressure and both rears are at 42 psi (fronts are 35 psi) measured undriven in 55 degree temp.
Does this indicate that the tire pressure is too high? I've already ordered a new set of tires but they're backordered so ideally want to make these last for about two more weeks. Would it make sense to reduce the pressure to something like 37 psi? Would it matter at this point?
slightly off topic, but did you order Michelin Pilot Sport 4S'?
I tried getting 295-35-19's for the rear, but was told they were a 6-8 week backorder (both from Tire Rack and Costco). Went with 305's as I could get them in 3 days.
As far wear, I agree that alignment looks like the culprit
Are you saying 35/44 PSI @ 55 degrees ambient, cold measurement? That's pretty high. Try 33/37 cold. I've found most tires start greasing up above 40 PSI Hot.
Alignment: it looks like you do not take corners hard enough to get on the outer edge of the tire :-)
(kind of joking)
These cars like Negative camber to deal with the weight on the back end and factory specs dial in the toe to help stabilize it from over steer.
You can adjust these things to extend tire length at the cost of handling or you can just live with the fact that 911's will abuse rear tires a little more that most cars
but will let the fronts live a long happy life. Plan on Two sets of rears to each set of fronts.
Hard accelerations also wear the inner rears out quicker.
If you AutoX or DE then you need a different alignment, If not, stick with the factory until that's to tame for you. Don't align for tires. Align for performance.
Personally, I wouldn't drive if chords are showing but that's me.
Congrats on getting that many miles! Fronts get close but rears nope.
For all tire pressure I try to keep where hot psi is exactly 10% higher than cold. Usually rear 40 does that. Old bike approach, if hot is less than 10% then too much cold psi, if more then too little. Especially if you run 100+, tires are your friend. On a bike you have maybe 6-8” total contact with surface, perfection of tread and pressure is life changing. Being **** is not a character fault.
I have GT3 wheels with GT3 sized PS4S (235f/305r)
At first I used my door card to inflate them when I was still on the Lobster FORKS but they were like rocks and also (although fun) it was too easy to kick out the rear.
I dropped to GT3 PSI (door sticker below) and everything felt more like butter.
Now on GT3 wheels, I definitely run GT3 pressures.
I also had Tyson Schmidt at PRO Motorsports in Burbank do my alignment and corner balance on OEM GT3 coilovers, which gives me confidence it is done right.
After almost 8k, my tires are solid.
...but I live in LA where the temp is rarely below 70. I also will run 30/35 cold to start and just keep checking it as I go. I know it isn't most people's cup of tea but I picked up the habit tracking where I check my tires and wheel bolts once or twice a week after 1-2 drives.
It also matters on tires as well. (e.g. older OEM tires vs. new tires or different tires = different pressures...).
Last edited by jamesinger; 03-11-2020 at 08:16 PM.
slightly off topic, but did you order Michelin Pilot Sport 4S'?
I tried getting 295-35-19's for the rear, but was told they were a 6-8 week backorder (both from Tire Rack and Costco). Went with 305's as I could get them in 3 days.
As far wear, I agree that alignment looks like the culprit
I currently have Michelin Pilot Sport 4S’s....
reached out to my local dealer and Tire Rack and they both said the rears are backordered. I didn’t realize they were 6-8 weeks backordered....shoot.
I guess my options are to drive on these for 6-8 weeks, get the Michelin PSS instead, or try 305 rears on my 997S....
Recently looked under the car and noticed the rear right tire is showing threads right on the edge of the tire, not showing on the left rear but probably means I take a lot more right turns. I find this interesting as there's still a little bit of tire thread. I checked the tire pressure and both rears are at 42 psi (fronts are 35 psi) measured undriven in 55 degree temp.
Does this indicate that the tire pressure is too high? I've already ordered a new set of tires but they're backordered so ideally want to make these last for about two more weeks. Would it make sense to reduce the pressure to something like 37 psi? Would it matter at this point?
All three of my 997's have worn the rear tires just like that no matter what alignment or toe setting. All three have been lowered with H&R springs though which the techs at the dealer said makes all the difference. Picture attached of one set of Michelin PSS's I got 12,000 miles out of which has been typical or maybe even on the high side.
Move up to the 305 and replace them. Have your alignment done to minimize (not eliminate) rear camber and rear toe and they'll wear a bit more evenly, but 20k miles from a set of rears is really good. You must be driving pretty gently.
03-10-2020, 05:56 PM
Tire threads showing on inner rear - tire pressure of 42 psi too high?
