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Discussion Starter · #1 ·
I've finally received all the parts to refresh my suspension (stage2 ECS kit, H&R cup kit, OEM M3 RTABs/Vorschlag limiters) and was wondering how to go about preloading the RTABs. Searching only came up with some M specific threads from various forums.

It's my understanding that preloading will ensure the same angle on the bushing inside the casing. Am I just basically bolting everything back up to the exact (or very close to it) location? I'm planning on marking the console bolts to their location on the car. Will this be sufficient or is there more involved?

Thanks in advance for any help/advice. Can't wait till Friday to get this job started!
 

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i would be wary of preloading. every time I do it, I put on the control arms and put the fcabs on under the car one side at a time.
 

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Guys, guys, guys how many times do I have to say this: PRELOAD IS NOT NECESSARY (NOR IS IT EVEN POSSIBLE) on E46 bushings. This method is for E30s and E36s only that use a circular hole for the control arm. E46s have a hex-shaped hole which you couldn't preload even if you wanted. The only way you could get into trouble is if you pressed in new bushings the wrong way into the carrier. 95% of people buy the bushings preinstalled into new lollipop carriers.

NO NEED FOR PRELOAD.
 

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Guys, guys, guys how many times do I have to say this: PRELOAD IS NOT NECESSARY (NOR IS IT EVEN POSSIBLE) on E46 bushings. This method is for E30s and E36s only that use a circular hole for the control arm. E46s have a hex-shaped hole which you couldn't preload even if you wanted. The only way you could get into trouble is if you pressed in new bushings the wrong way into the carrier. 95% of people buy the bushings preinstalled into new lollipop carriers.

NO NEED FOR PRELOAD.

Not all e46s have hex-shaped control arm ends. Mine are round, and preload is indeed an issue.
 

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Not all e46s have hex-shaped control arm ends. Mine are round, and preload is indeed an issue.
Sorry then maybe it's an Xi-specific thing. If so, then use soap and water to grease the bushing and control arm and drop car on the wheels within half an hour.

As for the RTABs, my understanding is to use a long straight-edge or a ruler and press it against the BOTTOM of the RTAB carrier. Then you measure 8mm BELOW the center of the hub and you put your straight edge to this point while pressed flat onto the bottom of the RTAB carrier. Then you tighten your 18mm carrier bolt to spec which I believe is 81 ft-lbs.
 

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RTABs require preloading, otherwise, you will wear them pre-maturely. You can either use the special BMW tool which attaches to the wheel and provides the proper angle, or you can use a marker and mark the "box" perimeter to maintain the angle.
 

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Discussion Starter · #12 ·
Thanks for the replies. This is exactly the info I was looking for. When I searched I couldn't find anything that seemed definitive. So I need to loosely bolt the new RTAB into the carrier, then run a straightedge from the bottom of the carrier to 8mm below the middle of the hub? Seems easy enough. I don't know why for some reason I thought this was going to be a complicated procedure. Does this all have to be exact or is just getting it close sufficient enough to maintain toe/camber?
 

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Thanks for the replies. This is exactly the info I was looking for. When I searched I couldn't find anything that seemed definitive. So I need to loosely bolt the new RTAB into the carrier, then run a straightedge from the bottom of the carrier to 8mm below the middle of the hub? Seems easy enough. I don't know why for some reason I thought this was going to be a complicated procedure. Does this all have to be exact or is just getting it close sufficient enough to maintain toe/camber?
You will still need to get a wheel alignment. When I installed the new RTABs, I tried to center them in the RTA, but the original bushings were not. So I know my toe is off, but good enough until I can get to the tire shop.
 

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Never heard of a preload as applied to RTABs. No preload is mentioned in the above Powerflex install DIY. Is the preload for OEM type bushings only? Can someone explain? I have HD bushings with Turner limiters. There is no preload.
 

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With RTABs (rear trailing arm bushings--NOT front control arm bushings), you do need proper preload (aka no preload) on the bushing because the bushing carrier rotates on the rear trailing arm. If you bolt it at an angle, then when you drop the car back down, the bushing will have a pre-loaded amount of flex on the bushing. Meaning it will be stressed at rest. You want the bushing to have zero stress on it at rest. I'm sure not even the factory always gets this 100% correct, but you can do your best to minimize flex. The 8mm below hub center line/straight edge rule was developed as an alternative to the expensive BMW tool.
 

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Oem type bushings require pre load. You need a bar that will align the rtab carrier base to the center hub. Or you can mark it with a marker like orient says. That's what's i did and its perfect

Sent from my DROIDX using BimmerApp
 

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With RTABs (rear trailing arm bushings--NOT front control arm bushings), you do need proper preload (aka no preload) on the bushing because the bushing carrier rotates on the rear trailing arm. If you bolt it at an angle, then when you drop the car back down, the bushing will have a pre-loaded amount of flex on the bushing. Meaning it will be stressed at rest. You want the bushing to have zero stress on it at rest. I'm sure not even the factory always gets this 100% correct, but you can do your best to minimize flex. The 8mm below hub center line/straight edge rule was developed as an alternative to the expensive BMW tool.
Sir, you are the only one who knows how and why the bushing must be installed properly. As you say, "You want the bushing to have zero stress on it at rest." You are 100% correct. Let me just add, "at rest" means the car is sitting on the ground and the suspension settled to its normal ride height.
 
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