City driving, uneven tire wear, and tire pressures

[Sabs]

Are others seeing unusually high wear on the outer edges of their tires?

Despite being in spec for alignment, my tires have worn 2 or 3/32" more on the outer edges compared to the center of the tire.

I'm running 36psi front/rear on staggered tires. The majority of my driving is city miles with lower speeds and lots of stops and turns. I've put on enough miles to go through 2 sets of tires now - one set of PS4's and one set of DWS06+'s. The DWS06+'s lasted a bit longer, but had the same problem with high outer wear, especially on the front tires.

Has anyone tried running 40psi, or even higher during the life of their tires? Other than being a bit harsher over certain bumps, have you seen any downsides?

 

[Thomby]

Some of the AWDs recommend slightly higher front pressure (36-38psi vs. a fixed 36psi rear). And I've always heard "better 2 over than 5 under", since most people probably run under-pressured tires most of the time from not checking them.

So going from 36 to 40 psi up front shouldn't hurt anything and may balance out your wear. Might be getting a bit high for the rears in terms of grip, but you did mention it was mostly the front. Maybe 38 rear as a compromise.

Of course you could also get an alignment check to make sure you don't have too little (zero or positive) camber. If so correct it, and if not you could ask them to bias you toward the aggressive (more negative) side of the recommended range, but if you do that you'll want to keep an eye on the inside edges to make sure you don't overcompensate and wear them down.

 

[Sabs]

Thanks for the response. 40 front/38 rear is actually what I've been running for a little while, since the issue was worse on the front. I probably won't know if it helps for several thousand miles, but those numbers seem safe.

Unfortunately Stingers don't have a front camber adjustment, just the rear, but I'm close to -1 on both front wheels.

 

[Snicklefritz]

So going from 36 to 40 psi up front shouldn't hurt anything

That would be 38 psi to 40 psi. The door card on an AWD with 19" wheels says to inflate to 38 front 36 rear.

This outer wear on the front tires has bugged me throughout ownership, now almost seven years. I never got a handle on a solution. I tried 40 psi at all four staggered corners for most of half a dozen years. But I think that if it made a difference it wasn't much of one. I refuse to bump the psi over 40, as the ride and handling/grip suffer. Recently I changed to A/S year-round. I noticed that my previous set of A/S seemed to wear more evenly, if they didn't actually last much longer than the Michelin Pilot Sport. One of the last negatives I had running the Michelin is that the rear tires wore down first on the inside edges. I took a bit of the negative camber out. I am still watching to see if the inside rear edges wear faster. If they do I'll reduce the camber even more I suppose.

 

[Thomby]

That would be 38 psi to 40 psi. The door card on an AWD with 19" wheels says to inflate to 38 front 36 rear.

He said he was running 36, and I thought the front was spec'd at 36-38, but maybe that's RWD. The point being that jumping 4 psi would only put him 2 above what's called for which seems reasonable (and probably the minimum change it would take to really notice anything).

Outside front does seem odd because if anything I'd expect things like aggressive/sporty suspension setups (lots of front camber, weird toe effects in the rear under hard acceleration) to impact the inner edges. I don't know of any common suspension wear that would hit the outside edges.

 

[Snicklefritz]

That would be RWD. With AWD the psi is reversed on 19s. We are actually talking about potentially at least four sets of door card specs. When I go to my GT wheels this fall, and shelve the 18s, I will be running staggered on my Premium. Spec on the door card is 36-39 on squared 225s. This is AWD too. Ima going to run A/S 225 front 255 rear, like I do on the 3.3L. My question is, do I run 38-36 like the AWD door card says for the GT1? Or is the different weight distribution with the 2.0L engine going to recommend some other psi setting front and rear? What do you think?

He said he was running 36, and I thought the front was spec'd at 36-38, but maybe that's RWD. The point being that jumping 4 psi would only put him 2 above what's called for which seems reasonable (and probably the minimum change it would take to really notice anything).

Outside front does seem odd because if anything I'd expect things like aggressive/sporty suspension setups (lots of front camber, weird toe effects in the rear under hard acceleration) to impact the inner edges. I don't know of any common suspension wear that would hit the outside edges.

 

[Thomby]

My question is, do I run 38-36 like the AWD door card says for the GT1? Or is the different weight distribution with the 2.0L engine going to recommend some other psi setting front and rear?

Definitely not a tire guru, but it seems like there are 3 major factors that might impact front vs. rear pressure.
- RWD vs. AWD: all else equal I would expect a lower rear pressure vs. front on RWD since those tires need to grip more (but less critical for the I4)
- Weight distribution: for V6 vs. I4, and for AWD, more weight up front would mean higher front pressure relative to rear
- Staggered tires: wider rears = shorter contact patch, so maybe reduce rear pressure as a way of increasing contact patch (making it as deep as fronts, just wider)

So for an AWD, staggered tire, 4 cylinder, you have some of the extra weight up front that an AWD 3.3 has, but not all of it. You have less power going to the rear, plus the front tires helping pull the car, and the larger rears sized for 3.3 power. Seems like less need for lower rear pressure, less need for higher front pressure, so maybe same pressure or 1psi higher in front?

 

[Snicklefritz]

Definitely not a tire guru, but it seems like there are 3 major factors that might impact front vs. rear pressure.
- RWD vs. AWD: all else equal I would expect a lower rear pressure vs. front on RWD since those tires need to grip more (but less critical for the I4)
- Weight distribution: for V6 vs. I4, and for AWD, more weight up front would mean higher front pressure relative to rear
- Staggered tires: wider rears = shorter contact patch, so maybe reduce rear pressure as a way of increasing contact patch (making it as deep as fronts, just wider)

So for an AWD, staggered tire, 4 cylinder, you have some of the extra weight up front that an AWD 3.3 has, but not all of it. You have less power going to the rear, plus the front tires helping pull the car, and the larger rears sized for 3.3 power. Seems like less need for lower rear pressure, less need for higher front pressure, so maybe same pressure or 1psi higher in front?

Thanks for the assessment. Ima even less of a tire guy than you. It looks like there is no reason to change the front psi as shown on the door card, since the tire width is identical at 225. Wider in the rear at 255 is the question I guess. Since 36 psi is the AWD spec for rear tires on the 3.3L I will probably leave them alone and run 36 psi at all four corners - unless someone sees this conversation who knows a good reason to run a different psi in the rear with a 255 on a 2.0L setup.

 

[Thomby]

It looks like there is no reason to change the front psi as shown on the door card, since the tire width is identical at 225. Wider in the rear at 255 is the question I guess.

When I wrote "1psi higher in front" I meant relative to the rear, rather than over front spec. Going wider at the same load should shorten the contact patch front to rear (to maintain same area as it gets wider), so dropping pressure could compensate for that by increasing the contact patch (ie wider at original depth).

But dropping rears to 35, while having less weight & power than the V6, doesn't really make sense as I think about it. Plus I have a bias toward the high side of spec (36-38 front for me), so I guess I was thinking more like 37F/36R as a compromise. Although that's really nit-picking since the first weather change will throw that out the window.

 

[Snicklefritz]

Yeah, Ima nitpicky but not quite that much. Lately, I like my cold psi to exactly match the door card spec. But if it is lower than that - like right now when the temperatures have dipped quite a bit - and warms up to door card spec that's good too. We are talking typically of a 3-4 psi difference cold to running temperatures. It can be even more in the summer. So, why do we fixate on exact psi? Maybe it's fun. I recently acquired a nifty Longacre tire gauge, a racing quality instrument. That is probably not going to help my OC behavior in this area. Ah hah.