lexusrus

Anyone rotated their front tires "side to side"?

I have Michellin PS AS. I took my RCF to a tire shop to get two new REAR tires put on (worn almost down to indicator bars).

They noticed there were very very minor uneven wear on fronts (inside areas).

Since I had LIFETIME alignment with them so I got alignment done free of charge.

They recommended moving the front tires side to side to even out the tire wear. (The front tires are still very good with lots of treads left and looked new). I asked then if this is "safe to do". They said bc the tires I have are not "directional", so it's ok to do.

Afterwards I found my RCF just "sliding" left to right at around 45 to 65 mph. Meaning it's got a mind of its own, kind of. It's getting hot where my RCF is at (90F+) and I noticed the tire pressure is reading at 40 front tires and 38 rear tires. (When I did the tires it was like 40'sF up further north.)

Also they did not have matching Michellin PS AS at the time. So I got new Pirelli P Zeros AS for the rears.

So is it because the tire pressures are too high which I'll have to adjust. Or the swapping front tires side to side is BAD? Or the Pirellis not getting along with Michellins?

Anybody with this experience? Any insights is greatly appreciated. Thanks

05RollaXRS

Yes, side to side rotation is part of our service and maintenance. The dealership did it on my RCF just last week. Inner side wear is also normal and is quite typical of this car, according to the dealership. If you want to reduce inner tire wear, you can get the RR lower control arm bushings that are polyurethane and very stiff so they prevent the tires putting more load on the inner tire under braking. I have something like 5 mm tread left and I have some more wear on the inner side as there is some negative camber. Dealership did not recommend alignment because the tech said, having less aggressive alignment will not be good for handling.

The side to side slipping is most likely because of your tires lacking grip. You need grippier tires as those all seasons don't offer enough grip in the warmer weather. Also, mismatched front and rear tires also compounds the issue as you have different grip front and back.

lexusrus

Thanks for your insights.

Here is my alignment printout before and after.

05RollaXRS

Interesting how your camber is still negative after the alignment. It is good in the sense since neutral camber usually reduces grip while turning (leads to understeer) so some negative camber (in your case, it is very minimal) is good for handling as it maximizes contact patch while turning. You might experience some inner tire wear (I have the same). If you want to reduce inner wear during hard braking, you can get the RR ultimate steering response bushings and it will help in reducing inner tire wear under braking.

Also, consider switching your tires ASAP. Running two different types of tires front and back on a performance car, is not a good idea. I would recommend the XL-version of the MPS4S tires.

I get some side to side darting on the OEM michelins, but only when they are cold. Once they warm up on a grippy surface, it tracks straight as an arrow.

buister

iTrader: (1)

I just looked up the tread design of the PS AS and they don't look symmetrical inner half vs outer half, which means they are specific left tire and right tire. I don't think it's a good idea to switch them. It's designed to work one way only. Some tires like the Hankook Ventus that has the symmetrical tread across the center line are ok to switch left and right.

lobuxracer

iTrader: (2)

I'm not at all sure what Rolla is talking about. Camber less than +/-2.5 degrees is not a primary wear issue. Toe is the big problem with these platforms, and the big squishy donut bushing at the rear of the lower control arm is a huge contributor to this problem because the front tires toe out a LOT under braking with the more brake you apply creating more toe out. On the track, it can be a little helpful to rotate the car if you trailbrake. Anything else and it's nothing but bad. The bushings in the RC F and GS F are significantly stiffer than the 2IS, but they're still big flexy fluid filled rubber bushings. Toe control in the rear is equally vexing, but not as prone to unusual wear as the front is.

I would not be super excited with the alignment you got. If it were my car, I'd move the front subframe just a tad to balance out the camber from side to side, and I'd figure out what is all screwed up with the rear camber. A difference of 0.5 degrees from left to right isn't exactly small. You've also got a lot of rear toe. I generally don't go more than +0.08 a side in the rear. It is true rear toe will help the car turn, but it will also eat up your rear tire edges pretty quickly so you need to find balance with your driving/roads/tire selection. My Supra ate up a pair of rear tires in 6k miles because I set it to the factory recommended 3mm total toe in. That's what drove me to come up with the "lance alignment" so popular with Supra owners way back in 1998.

05RollaXRS

I heard that here where Rafi explains the USRS lower control arms. At 5:42, he talks about camber gain and how it can address the typical inner tire wear issue on the ISF.

lobuxracer

iTrader: (2)

You misunderstood what he is saying. Camber doesn't cause the problem on the IS F. Toe does.

https://www.clublexus.com/forums/is-...alignment.html

Watch the video in the first post of this thread:

https://www.clublexus.com/forums/cl-...eo-inside.html

This isn't something I am guessing about at all.

buister

iTrader: (1)

True, bad toe kills tires. I remember reading a brochure at the alignment shop that I went to: something like 0.3 deg off can have the same effect as dragging the tires for 67 miles after 10,000 miles of use.

lexusrus

Thanks for everyone's suggestions and insights.

I stopped by a truck stop and aired my rear tires (new Pirelli P Zero AS XL) to 42 psi. I kept the front old Michellins PS AS 3+ at 40 psi. BTW, these were "hot temperature" after driving for about an hour in 92+ F ambient temperature. (The COLD psi were like 38 fronts and 36 rears from the tire shop install. I don't know why they did it like that?) The tire PSI's stayed STABLE at the above newly inflated PSI after driving for like 2 more hours.

After I aired up the rears.....the wobbling left to right disappeared and my RCF is again ALMOST as stable as before. I agree the OEM PS tires were even more stable.

I looked at the front Michellin PS AS 3+ tires and it did say "outside" which made me to believe these are "directional" snd SHOULD NOT BE switched left to right.

I also plan to just go ahead and order ASAP two more P Zero AS front tires to match the new rear P Zero AS rear tires to keep it all the same.

Thanks for all of your input. I just can not believe some 4 -6 psi air pressure difference front and back can make a big difference in the RCF handling (before when my RCF was wobbling side to side it was so weird like it has a mind of its own and was very scary when I was going some 65+mph on perfectly dry flat highway)!!!