E36 rack swap -THE correct location for the spacers

[benz-tech]

I have read many opinons on where to place the rack spacers and they are in-fact just opinions. I have an alignment rack at work sooo, time to end the debate. Here is the sum-up:

SPACERS UNDER THE RACK-- this yeilds an incredible amount of bump-steer. Somwhere around 1.5 degrees in about 3" of upward and 2" of downward movement. PER SIDE! So if you set the toe at 0*, when you raised the car 4" it would be 1.5* and the opposite when lowering. 5-6* of toe change per side per suspension sweep. Unacceptable.

SPLIT A SPACER ON TOP AND BOTTOM OF RACK-- long story short this yeilded a bit less than 1* when moving the suspension up 4" and close to it when sagging. Again starting from 0* toe at normal ride height. Still unacceptable.

INSTALL THE SPACERS ON THE TOP OF THE RACK!!-- When doing this, the most I could get the toe to change per side was around 20min up and 20min down. 40' through the my full sweep (4" up and 3" down from my ride height) 40 min is just over half of 1 degree. IMO this is still barely tolerable but it is certainly the best of the 3 options.

I haven't driven the car too far since changing it. I have thrown it through a few bumpy turns and it is more stable. Oh that reminds me, I ran my little test with the steering wheel turned 180* just to see if that affected the measurements. It didn't.

I have H&R sports w/ e90 drop hats, so my car is not too low.

[jeffnhiscars]

Thanks for making this effort. It's always appreciated when someone tries to de-mystify some of what we do on faith.

I'm a "spacer on top" guy having done it that way on both my lowered 84 318i (BS Sports, Eibach Prokits, new strut mounts) & my stock Cabrio. Both cars have brand new lemforder CA's, tie rods, links & offset CAB's. The rack install on the 318 actually eliminated the bump steer I didnt even know I had. Both cars track rock solid (without an alignment) & I am not getting any tire wear issues (yet anyway).

It's a fair "control" situation so you'd think the 2 cars would behave differently after identical rack swaps (despite obvious weight differences) since 1 is lowered and 1 isnt

If spacer placement is supposed to compensate for lowering, shouldnt I have a camber issue somewhere ?

I hope that made sense :)

[benz-tech]

A steering rack replacement will only affect camber if you have not properly set the toe. And that is only because the castor angle causes the camber to go more toward negative as the front of the wheel turns in. In general, though, your camber changes because you lowered your car. My car is at -1.5* in the front and -2.0* in the rear.
You say that you did not align the car. I hope at least you set the toe with a measuring tape ;)

[scottinAZ]

problem I have with the spacers on top is oil pan clearance. I have maybe 1/4 inch of clearance with the 1/2 inch spacers on the top. I cannot physically fit the spacers in the bottom on my application. I have an M50 swap in place.

has anyone checked to see what the toe change is throughout the sweep with a factory rack?

[jeffnhiscars]

A steering rack replacement will only affect camber if you have not properly set the toe. And that is only because the castor angle causes the camber to go more toward negative as the front of the wheel turns in. In general, though, your camber changes because you lowered your car. My car is at -1.5* in the front and -2.0* in the rear.
You say that you did not align the car. I hope at least you set the toe with a measuring tape ;)

The rack swap itself shouldnt effect camber (subject to your toe comment) but the lowering does and the consensus seems to be that spacer placement when you DO change the rack, can effect camber and\or bump steer. I asked since I have 1 car lowered one not and both have spacers on top...although I did change to offset CABS in the Cabrio.

What were we talking about :)

As for alignment, I actually measured the old & new tie rods & racks on the ground. One set of e36 tierods & 1 e30 set. The racks were the same length so I adjusted the tie rods to match at 15 1/2" measuring from the inner hub (where it butts to the rack end) to the centre of the outer ball joint (underneath). I did 2 cars recently like this and they both track straight. Go figure.

[pantelones]

Hmmm I was under the impression that the more parallel the tie-rod is to the control arm the less bump-steer you get. I currently have the spacer on the bottom and when I drove my car for the first time in a few months and I did notice a good amount of bump-steer. I'll have to do some measurements of my own and see if I can eliminate it with the spacer placement. BTW I am running stock 325e front springs (-1 coil and heat treated top coil) w/ e90 drop hats, and stock m3 springs in the rear. About a 1.5" drop all around. Also no power-steering and a 75d poly steering coupler.

[benz-tech]

As for alignment, I actually measured the old & new tie rods & racks on the ground. One set of e36 tierods & 1 e30 set. The racks were the same length so I adjusted the tie rods to match at 15 1/2" measuring from the inner hub (where it butts to the rack end) to the centre of the outer ball joint (underneath). I did 2 cars recently like this and they both track straight. Go figure.

If your toe-in happens to be correct it would be a miracle. Ofset CAB's will change the toe dramtically after you install them. I highly suggest a proper toe adjustment. Measuring the tie rods is a good starting point but even after I do that on an MB rack replacement, the actual numbers are off far enough to have caused tire wear.

[benz-tech]

Hmmm I was under the impression that the more parallel the tie-rod is to the control arm the less bump-steer you get.

I thought the same thing, hence the reason I started out with the spacers in the middle (hit the pan if I put them on the bottom). But the real place to draw the imaginary line at is the pivot points from the inner and outer ball joints. When I eyeballed that up on the alignment rack it made more sense why the bumpsteer got better when the rack was placed lower. Either way, I knew the numbers wouldn't lie and I was suprised with the results. Several miles on it now and it is much much better than before.

[Wild Ride]

Added this to the list of things I do as I have my spacers centered on my install and this car felt more unstable and less planted than my other car with an e30 m3 rack. Thank you

[jeffnhiscars]

If your toe-in happens to be correct it would be a miracle. Ofset CAB's will change the toe dramtically after you install them. I highly suggest a proper toe adjustment. Measuring the tie rods is a good starting point but even after I do that on an MB rack replacement, the actual numbers are off far enough to have caused tire wear.

I'm inclined to agree that my toe is unlikely to be on spec. However, if you read enough of these threads you begin to wonder what IS spec. I know what the book says but once you start changing your suspension around, does "spec" still count ? While offset CAB's MAY effect toe, its really castor that they change, which is also non adjustable in an otherwise stock car.

I'm old school but then I drive an old school car. The only e30 I ever had aligned was my 84 318i when I put in the Bilstein Sports & Eibachs. They set the front toe, told me my rear was out and those tires wore well until they literally fell of the wheels (I lent it to my son for that. Dont ask).

They want $99 here for an alignment and we know all they can adjust is front toe since I have no camber plates front or rear we KNOW my camber is out. If the car tracks well, feels stable, doesnt pull to the side & the tires wear reasonably well, I dont see the point in worrying about "spec toe in" especially if I know I'm going to be taking something apart in the not too distant future.

Just sayin'

[harv]

While offset CAB's MAY effect toe, its really castor that they change, which is also non adjustable in an otherwise stock car.

By relocating the rear of the control arm they end up changing toe quite a bit.

John

[JonnyOg]

Anyone have a pic of the spacers on the top of the rack? I thought there was only one place you could put the spacers :/

[VinniE30]

This is strange advice. I've always read that putting the spacers on the bottom would create less bump-steer than putting the spacers on the top... because with the spacers below the rack the rack would be higher than with them above the rack.

[AndrewBird]

Hmmm I was under the impression that the more parallel the tie-rod is to the control arm the less bump-steer you get.

This is only true in an ideal situation where the pivot point for the control arm and the pivot point for the tire rod are at the same distance from the center of the car.

[benz-tech]

This is only true in an ideal situation where the pivot point for the control arm and the pivot point for the tire rod are at the same distance from the center of the car.

And where the actual pivot point of the ball joint and tie rod is. Believe me, I thought at first the spacers should go under the rack. That is, untill I put the car on our alignment rack. Spacers on the top= far less bump steer.