535/540 v 525 suspension and negative camber

[kouks]

So I installed new rear shocks with new shock mounts and rubber stops and new rear pitman arms. I also swapped the 525 springs for 535 springs, which are 22mm shorter and I'm guessing more tighter, or so it feels like slightly when I drive. But I've encountered a negative camber problem on the 525, see photos below.



Its even more noticeable in real life. From RealOEM, the trailing arm on the 535/540 is a different part number than the 525, and so are the output shafts from the differential to the axle. Does this mean to lower a 525 you need to rip out the entire rear suspension and replace from a 535/540 car, or is there any way to reduce the camber effect? When I torqued the pitman arms, I compressed the rear axle to normal ride height first. I assume that was the correct procedure?

My concern is excessive inner tire wear, especially since I'm considering 235 or 245 wide tires for the rear.

The front has not yet been dropped from 525 to the M5 OE springs I have, wonder if that will also show negative camber. or if it will help any with the rear.

[moroza]

535i springs are 22mm shorter than 525i? That doesn't sound right... are you sure they're stock, base suspension, not M-Tech or such?

The trailing arms are different because the wheelbearings and hubs are different. I highly doubt - but am not 100% certain - that there is any difference that would affect suspension geometry.

Considerable negative camber (some 2, 3 degrees) is normal for an E34 rear. You might just have worn RTABs.

Yes, the dogbones are to be tightened at normal ride height.

[demetk]

Yes, the dogbones are to be tightened at normal ride height.

Only reason for that is you can't tighten them any other way, otherwise the second bolt won't go through.

[kouks]

535i springs are 22mm shorter than 525i? That doesn't sound right... are you sure they're stock, base suspension, not M-Tech or such?

.

Hmmm...

Here's a side by side photo, 525 on left. BleedsBlue sold me his old springs from an M5 he was parting out I think (SLS delete), M5 OE front and 535 OE rear, that's what he told me. I measured them side by side and the 535 were about 22mm shorter.

[demetk]

Looks like the one on the right is broken?

[moroza]

It does. Furthermore it looks like a progressive-rate spring (uneven coil spacing), compared to the fixed-rate (even coil spacing) on the left.

I would expect an M5 owner to use "sport" or "low-slung" or "M-Tech" or some other non-base spring, but who knows? Paging BleedsBlue...

[BleedsBlue]

Interesting...I did not carry out the the SLS delete on my car, but my good buddy did, and he took those springs off a stock 535i parts car and installed them with no modification.

I used them for a good 5k miles with zero issues on my M5, first on blown 535i rear shocks, then fresh Billie HDs. They certainly aren't broken. There is a bit of surface corrosion on the end of a coil, which can be seen.

In my notes it looks like I sold the set to you for $100 shipped, and I know shipping was about $30; I was basically throwing the 535i springs in there are no charge, since I assumed $70 was a decent price for good OEM M5 front springs.

Let me know if I need to rectify anything with this, Bill? Any reason you can't re-use the 525i springs, if these springs turn out to be the issue?

Here's a reference picture of my M5 with these springs and pretty tall tires, it was as high as a stock M5 + or - a few mm:



- - - Updated - - -

Edit: I'll admit I'm not quite following how negative camber would be caused by the spring, just FYI. I played a lot with springs, and separately camber, and obviously lowering a car significantly induces negative camber. But I can't tell how much Kouks' car was lowered compared to before.

[kouks]

Couple questions and comments.

The ride height is actually perfect on the rear axle, looks very close to your M5 Brent. I planned to measure before and after to see how much the car lowered but escaped my mind at the time. Just by looking at photos it appears to be close to about .75-1 inch lower. My daughter drives the car and says it definitely feels better after I changed out the shocks and springs. New Meyle standard shocks.

The original 525i springs are still usable if needed

I installed the springs with the tighter coils on top. Is this correct for progressive springs or should the tighter pitch be on the shock (bottom) side??

Both springs looked identical, and both sides are same ride height, so if they were "broken" or cut by someone I think the differences would have been apparent. The top tip looks broken in the picture because there is a plastic sheath over the spring on the top third, that is the plastic end jest warped.

The car is also sitting with negative rake (back lower than front) since the front has not been lowered yet. Would this make a difference?

I know the car had a bit of negative camber before this mod, but I thought that was because of the worn out shocks. I did not take any measurements, but just an eyeball feel that the current camber is greater than before. The previous camber was barely noticeable. Now it looks like a fat guy is sitting in the back seat. Just basic geometry says that the axle will rotate at the differential and a lower spring will increase the negative camber.

I looked at the RTABs and they were not torn up, however, they are still original with 22 yrs and 240k miles of use, so not perfect either. Will change those (what a PITA).

Brent - Don't worry about the transactions, all is well. I'm just wondering and learning more about the car. For all I know this could be normal.

How to I go about measuring camber so I can report in with some actual numbers, not just an opinion?

[BleedsBlue]

Cheers Bill, I just want to make sure I didn't sell ya duds. I do know the fronts are OEM M5, at least.

In general, any lowering of the car will induce more negative camber, your geometry is correct. It's tough to tell from the pictures, but yours does look a bit excessive. For instance, installing H&R springs on this M5 (after the picture above) and making no other changes pushed me past -2 camber (which I like, but that's a different story). No way I'll profess to accurately estimate your negative camber from a picture, but it looks more like -3 or more (or less... you know what I mean).

I agree the top coil or two in your picture above makes it look progressive, which confuses me. Perhaps these are not OEM springs at all? I thought they were stiff enough, but not uncomfortable--sounds like you are finding the same. A mystery!

I don't think the rake would cause extra negative camber.

I have heard that torn RTABs will cause excess negative camber, and at 240k I would assume those babies are destroyed.

There are measurements and calculators available online, to use angle measurements/levels and the like to determine camber, though I haven't tried those myself.

[kouks]

Found this thread on changing the RTABs, man what a PITA, more so than the front trailing bushings on the e36/e46 cars.

https://www.bimmerforums.com/forum/s...g-arm-bushings

[BleedsBlue]

Yep, I would totally rent Greg (93FIM5)'s tool for that. And I would also install OEM bearings, rather than OE rubbers that will go bad, or poly which can squeak.

Do you agree worn RTABs may cause excessive camber? A few more threads I've found would support that as being at least part of the problem.

[gearheadE30]

E34s have quite a bit of dynamic camber gain in the rear, meaning that the lower the car is, the more negative camber will be. What you're showing there appears to be normal; my 525iT at about the same height looks about the same. Hard to tell from pictures though. Your RTABs may well be worn, but I'd guess it's just because the car is lower.

Most people use the 535i sport springs when doing the SLS delete on an M5 - they are indeed a bit lower than the stock 525i springs, but I'm not sure by how much. Doesn't matter which direction you install the spring; it will work the same either way.

If you want to measure camber, you can either make a T plate and check it with a digital angleometer (zeroing off the ground first) or you can take it to an alignment shop and they can give you a printout.

[BleedsBlue]

Most people use the 535i sport springs when doing the SLS delete on an M5 - they are indeed a bit lower than the stock 525i springs, but I'm not sure by how much. Doesn't matter which direction you install the spring; it will work the same either way.

What do you make of the progressive-looking coils? Just an optional delusion? My buddy was pretty convinced they were OEM springs from the 535 parts car. All I know is the car rode great with them...

[gearheadE30]

What do you make of the progressive-looking coils? Just an optional delusion? My buddy was pretty convinced they were OEM springs from the 535 parts car. All I know is the car rode great with them...

I don't know that can draw any serious conclusions from the pictures. However, the coil spacing and wire diameter of the shorter spring is the same as the longer spring, aside from the progressive part. It almost looks like that 'progressive' coil is just a more-collapsed version of the longer spring. I suppose it could be a few things: the 'sport' factory springs lowered the car by progressively winding the spring, the spring was heated by some previous owner in an effort to lower a car (would have a non-factory finish or discoloration from heat), or they aren't OEM springs. Maybe you can scour the internet for what those should look like? I can definitely see how the rear would be a lot lower with those springs - based on the coil geometry, they won't be any stiffer than the taller spring (may even be softer), and so will lower the car by at least the delta in free spring length, if not a bit more.

[kouks]

I don't know that can draw any serious conclusions from the pictures. However, the coil spacing and wire diameter of the shorter spring is the same as the longer spring, aside from the progressive part. It almost looks like that 'progressive' coil is just a more-collapsed version of the longer spring. I suppose it could be a few things: the 'sport' factory springs lowered the car by progressively winding the spring, the spring was heated by some previous owner in an effort to lower a car (would have a non-factory finish or discoloration from heat), or they aren't OEM springs. Maybe you can scour the internet for what those should look like? I can definitely see how the rear would be a lot lower with those springs - based on the coil geometry, they won't be any stiffer than the taller spring (may even be softer), and so will lower the car by at least the delta in free spring length, if not a bit more.

The springs were not heated and reshaped, the paint was good on them throughout, and they had a yellow stripe painted on them. Both were identical in shape and size, so they are factory production. I'll have to get photos of 535i or M-tech springs to compare and see if they are OEM. Like I said, my daughter likes the ride so no issues there, and when I drive it it is stiffer than before, however, I also replaced the shocks, so maybe the new shocks are part of the damping too.

I'll be replacing the front springs with the M5 OE soon, along with new front wheel bearings, sway bar bushings, and sway bar dogbones. Not replacing the front struts since they are relatively new (about 50k miles on them) with no leaks (Boge). I'll see what that does to the ride.

Visually inspected the RTABs with the car on the pavement and the ones closer to the wheels are off center, (could not get a good view of the ones close to the drive) so, yes, worn. BleedsBlue you said to possibly replace with bearings instead of the rubber. Not on Pelican Parts, where can I find those?

Measured camber using this method:



Driver is 4.35 deg and Passenger side 3.4 deg, difference may be due to a slanted pavement in my case, but basically, the camber is about 4 deg on both sides. Definitely doing the bushings.

[BleedsBlue]

Good stuff, Kouks. I'm hoping the bushings get that camber back above -2/normal range!

The bearings came in all M5s, and are not cheap, but they last forever and are the ultimate upgrade there (above poly, which are cheaper and easier to install). The part number is 33321135808, and you need 4.

[kouks]

I was in the process of removing the RTA links and was reading the Bentley about removing the brake line. Says ASC+T cars (which is what I have) require special tools from BMW for brake bleeding. So I stopped right there. Anyone done this with ASC+T brakes??

[Onizukachan]

If you have to do the bushings anyway, consider doing the kmacs. No more dogbones, and you can fix your camber, and more importantly the toe.

Otherwisevtake the subframe out and mod it for camber and toe adjustment.

[kouks]

Replaced RTABs with Febi rubber ones. Also swapped to Vogtland springs. Have not taken any measurements yet, but the springs have lifted the rear so its not an apple to apples comparison. The old RTABs did not look bad, although they did have a bit of off centering. The shop the pressed them in thought they still looked OK for their age. Well, at least they are new now, good for another 200,000 miles.

[fo3]

I've got to do this job next for the same reason (excessive camber and most likely they're the original bushings on the RTA). It's my next job as I have just finished the front end rebuild today.
I've been trying to find out i) if the worn bushings are causing excessive camber as I know some camber is normal and my car is lowered so even worse. I might go taller springs and standard RTABs if that is all it takes to fix it
ii) if the adjustable kmac bushes are worth it or the bavauto ones - some say yes and others say no as very minor changes in camber can be done-like 1deg and I need about 3 deg
iii) whether anyone has tried the weld in ireland engineering system.-and if so then I've got to find someone in aussie that can fit it.

E: I know when i put it into gear and release the brake there is a lot of movement in the rear. maybe RTABs, maybe subframe bushes.