Some thoughts towards our LSD's

[Silver Ecstasy]

So I had a few thoughts today about our LSD that I haven't seen a single person post on here (or atleast since i've gotten my MS3).

-Tire pressure should absolutely even between the front two tires. If any tires should be monitored, it should be the front two. If you have a tire that is lower or higher than the other, you will have unequal rotation and this will cause the LSD to work overtime, causing eventual failure of the diff. The mentality is almost no different than cars with AWD systems. If you have varying tire PSI's on opposite sides of the car, that can cause damage. So..friendly reminder would be to make sure both tires have the same amount of pressure!

-Rotating or replacing tires: I thought about this today. Let's say you were to blow your front tire. So common sense would be to install the spare tire until you get to your destination. But..shouldn't you install the spare on the rear wheel instead, and swap good rear wheel to the front, until you can get safely home? I can't imagine how much damage that would cause to the LSD, forcing so much power to one side of the car for an extended period of time.

Also, if you were to replace your front tire, you should probably just replace both, or replace the one, and rotate your rear wheels to the front, and swap the front tire with the new tire to the rear?

I did not read any of this in the manual, and i'm taking what i've learned from owning a GTO, TBSS and seeing what happened to my mom's 03 Mountaineer AWD after having to replace the front diff twice and the rear diff once. She NEVER checked her pressure and we took a lot of trips in that car.

 

[MS3 GT]

make sense...???

 

[Silver Ecstasy]

Agreeing? Or asking the crowd?

 

[PCspeed3]

is one or two psi really going to make iff by that much and cause a diff. to go out? atleast i know my tires are all aat 38 psi.

 

[Silver Ecstasy]

I highly doubt that would make much of a difference, especially considering the fact that, since this hasn't really be brought up, i'm sure there are plenty of 07 guys with high mileage and no humming or howling diffs.

Naturally, the tires' psi is going to fluctuate, but you should really really not drive on different psi's on the drive wheels for extended periods of time.

The tire with less psi is not only going to have more load against the ground since it's tire contact patch is wider, it's also a smaller rotating diameter than the other tire with more psi in the tire. So the diff is constantly sending more power to one wheel than the other. This is a problem with limited slip diffs or awd systems because they work TOO constantly, rather than the diff doing it's job and maintaining equal power to both wheels.

One note on your 38 psi all the way around, you would really want to lower the psi in the rear wheels. You have a lot of weight in the front wheels from the engine and transmission, so the tires are actually going to bulge slightly, whereas with the rear, there is a lot less weight. Therefore, your rear tires are going to flex less during cornering since the tire pressure in the rear is so high, it's keeping the tires extra stable. This could cause some unwanted oversteer, especially in colder temps or enviroments. Just some food for thought or my own personal .02.

I would run 38F psi and 36R psi. It will be a even and comfortable pressure level, with neutral stability and predictability.

 

[MikeHTally]

Logic and caution would dictate NOT putting down any major ponies while the spare is on any corner, front or back. As for extended periods, that isn't the purpose of the spare. It's job is to hold up that corner 'til you can get the flat fixed/replaced.

I would suspect (don't know for sure) that it would take more than a couple-of-pounds difference to change the circumference significantly enough to affect the LSD components.

Ouch, 38 psi?! I'll stick with 34/32.

 

[Silver Ecstasy]

Mike,

When I say extended periods, I really am only referring to those emergency situations where you are forced to install a spare but arn't close to home and have to drive on it.

Also, 38 isn't as crazy as it sounds. 32psi cold pressure is the bare minimum and you run relatively close to running lower pressures when the temperature is low in the morning. Basically, the possibility that your tires will actually be lower than 32 at some points is extremely possible, and will net you less MPG.

 

[BOOSTR]

Running the spare up front is not the way to go ever with an LSD. I always run more psi than the sticker says and its equal all the way around. OEM Bridgestones lasted for 38,115 miles by doing that along with frequent rotations. Second set of tires, Goodyears are hanging in strong with 33K. Both are soft compound low wear rated tires.

Individual driving style has more to do with LSD failure versus tire psi, rotation or replacement. High speed driving around banked corners or on/off ramps places much stress on it, as does hard launching or launching on uneven surfaces. Basically driving like a fucknut is what kills them.

 

[Kain]

LSD or no, always run the spare in the rear on a wrong-wheel-drive car. The limits of a donut taking on both power and handling duties are low.

 

[MikeHTally]

...Basically driving like a fucknut is what kills them.

Hear, hear!