Help with tires/wheels/alignment
 

I've got a 3 week old (to us) 2001 x5 4.4i with 20 inch wheels 275-40-20 Frt & 315-35-20 Rear. Just had a flat on rear after 3000 km vacation pulling 3500lb boat. The inside of the tire was worn right down to the steel cords. This wear was only about 2" on the inside of the tire (driver's side) the other side rear also shows a lot of wear with cupping- but again only 2" or so on the very inside edge. When I had these tires on, the camber was very pronounced. I have since changed over to winter Nokian Hakapalitta 18". They ride so much better, I'm thinking I should change out the 20's for 18" for next summer. I do want to address the rear alignment and will be getting a four wheel alignment. What is the preferred setting for camber, toe in, caster on rear & front? Any suggestions if I keep the 20's on how to relieve the harsh ride? Does lowering tire pressure help (was at 32 psi)? Thanks to all who share their wisdom.

The harsh ride is probably due to the low aspect ratio of your tyres. 35 on the rear and 40 on the front does not give a lot of softness at all. your tyre pressure is spot on. They should be pressurised to 2.2 bar which in old money is 32 psi. If you reduce this then you will wear the tyres more around the outer edge and the inner edge. If you want a softer ride then stick with the 18's as the aspect ratio for these is higher

I had the same problem with excessive wear on inside tread on rear tires. Replacing rear axle ball joints at 150,000. There's a youtube vid showing what happens when rear axle ball joints go bad. VAC Motorsports - Correcting tire wear on a BMW X5 E53 - YouTube
Hope this helps

32 psi is spot on for the 20s, I actually run 33 psi in mine and love the ride. Obviously its a bit stiffer than 18s, but you learn to love it because the X looks so much better. Do you need to increase tire pressure when towing though? I never towed so I don't know.


The rear inside tread wear is most likely due to worn suspension parts, the upper control arm (wishbone) and the rear wheel carrier ball joint get worn quite easily, which slips the camber wayyyyyy out of spec. How many km's on your X? I have 69k MILES (don't know what it is in km's) and for example I recently had to replace all my front suspension parts (thrust arms, control arms, ball joints, tie rods, sway bar links) because all had a varying degree of wear, I even had a bad wheel bearing so replaced both, don't ask.

The rear on my X is all original still, save for the sway bar bushings and end links which I did myself. When I went for alignment, the rear right corner could not be brought into spec for camber, so it is at -3.0 degrees right now. Proper spec is between -1.0 and -1.9 in the rear I believe.



HOWEVER, if you dial out the TOE as close to zero as you can get it in the rear, you should be ok even if your camber is out of spec. I kept all my front alignment settings within spec, and everything in the rear is set within spec EXCEPT I had the shop adjust so the TOE is set to close to 0, .01 I believe. If you dial out the toe you will save your tires, the camber puts enough pressure on the inside edge, the TOE will shred them. The guiding link (straight control arm) on the rear adjusts the toe, the camber is adjusted at the lower swing arm near the frame at the eccentric bolt.



However, like I said, depending on how many km's on your X, you might want to replace any worn suspension parts in the rear first, before aligning. Most shops will do an alignment check for free, or for a couple bucks, so you can see how bad your current settings are.

Good luck and hope that helps!

:iagree:
Incorrect tire pressure is not good either. Over-inflate will make the center of the tire wear out faster. Under-inflate will wear out the side faster, which add to the camber/toe problem you already have.

Since you just purchased your X I assume you don't know how many miles were on the tires? (Note) rear tires and an X almost always wear faster than the front.

BMW alignment specs call for negative camber that (especially the rear tires) will wear the inside tread faster. The BMW negative camber specs are for handling. Any reduction in negative camber will be a negative impact to handling. That said, you can ask the alignment shop to dial it out if you want. Toe can also wear tires but in spec toe should not.

Dialing negative camber out won't be a safety concern unless you are pushing handling to the limits. At the limit less negative camber will increase oversteer. The X5 already oversteers at its limits. If you frequently drive on slick roads, including rain, the handing limit can be at very low speeds. I don't think you like more oversteer. I wouldn't dial it. I would much rather have the rear get loose than turning the wheel and the vehicle doesn't respond.

If you will be towing a 3500 lb. boat very often or the number of miles you mention, I would not dial out the negative camber. Tongue weight will increase negative camber if leveling system does not adjust accordingly. You should be able to see if the rear is lower than normal. Significant tongue weight, assuming alignment is in specs will increase inside tire wear. It is common towing practice to increase tire pressure to help compensate and to keep the tire heat normal.

I would get a 4 wheel alignment done first. If worn suspension parts are what is causing the wear, any shop worth going to will tell you they couldn't get it within specs, or, it is now but is not going to stay that way and why. If they are successful with alignment ask them to give you a copy of the before and after readings for reference in the future. I would not replace any suspension parts before an in spec alignment cannot be achieved.

I appreciate the replies. I do like the stance with the 20's on, but the stiff ride is not pleasant. The air leveling keeps the rear up when hooked to the boat. The car has 180k km and the suspension is reasonably tight-but I will do a closer inspection of the ball joints etc. The 20" tires looked to have about 50% wear on them- other than the scrubbed section on the rear. But i now have all winter to play with it. I don't think I will sacrifice handling by taking out the camber- I like the handling- as does DW. I really like this car, it's handling, it's gas mileage (even pulling the boat), but I will have to rethink the 20" wheels by spring. I'm leaning toward 18" and maybe something like Nokian All Weather tires or similar.

I'm sorry redliner but we are usually in sync, but I don't agree with this statement. With the -2.0 degrees of camber in the rear that is "in spec", adding +.15 of toe as well absolutely is the culprit to shred the tires. I have to pull up my alignment sheet from my last one, but "spec" for toe in the rear is something like +.08 - .16 if i recall correct, and just leaving in spec even at the lower end (most shops will get as close as they can, or just set in the middle) is wayyyyyy too much toe in conjunction with the already aggressive negative camber.


I was just telling him in the meantime if his camber is way out he can try to offset it by dialing down the toe closer to 0, obviously if all worn suspension parts are replaced and his camber is at the lower end of the acceptable range (think -1.5 or so), then having toe set "within spec" at the lowest end of the range should be ok for tire wear.


Most of us on here have some aspect of worn rear suspension parts so obviously the tires do wear somewhat unevenly unless you pay attention to it.

Spec toe for the rears should be 0.07 to 0.23. Mine has been set to as close to the middle as possible (around 0.14) with about -2.1 of camber...No excessive wear on inner edges. 90k miles...all original suspension components.

Yes, we often agree. I like that much better but I don't mind when we don't as you do so with respect.

Not sure but I think we are saying the same thing. Seems like the difference is that I missed you were suggesting how to deal with suspension as is and I was coming from a suspension that is in good shape that can be adjusted to be in spec. If we are not saying the same thing that's OK.

Coincidentally, this past Thursday I replaced two front tires on my wife's 335. They are certainly proud of run flat tires. The inside of the tires were worn more than the outside. I am taking it in Monday for an alignment.

We are on the same page for sure :thumbup:


Obviously I and you both recommend replacing the parts that are worn in the rear then bringing into spec on the alignment. If he wants to just get it align until he wants to overhaul the worn suspension, dialing out the toe will take a lot of the scrubbing on the rear edges that happens when too much neg camber and too much toe is present. That's definitely a band aid fix which could buy some time for the OP until he wants to really fix the problem.

OP I think you need to replace those rear swing arm ball joints, and possibly the wishbone control arms, then get an alignment, those are the two most popular culprits in the rear. The straight guide link is usually pretty stout, and above 100k the bushings on the subframe may need to be checked/replaced as well.