Bimmerworld RTABs

[RBNetEngr]

Has anyone on here installed these RTABs? If so, can you share your experience with them, and how they perform compared to stock RTABs?

https://www.bimmerworld.com/E46-E36-3-Series-and-Z4-Rear-Trailing-Arm-Bearing-Kit.html


-rb

[ScotcH]

We have them in a race car ... they work as advertized. I'm sue they are harsh as hell on the street as they are actually solid and would be similar to the GC or Turner setup.

[aeronaut]

I also have them. Installed last year. So far so good.
I'll add, they both press in and have flanges on both sides to sandwich the RTA between the flanges. I don't think these do much, there was a mm or so gap after install on mine.

Also, I wouldn't run these on a street car.

I think FCPEuro sells a version also, which you know, free lifetime replacements. But they are a chunk more change.

[RBNetEngr]

Thanks. My application would be for a street car that does 1-3 track events (HPDE,
Track Night, etc.) per year.


-rb

[NoLastName]

Thanks. My application would be for a street car that does 1-3 track events (HPDE,
Track Night, etc.) per year.

For that use your best bet is stock trailing arm bushings with limiters installed.

[TostitoBandito]

For that use your best bet is stock trailing arm bushings with limiters installed.

This is the correct answer. OEM rubber with limiters.

[propcar]

Rogue Engineering has also just released their own version.

Looks great, although I'd probably go with FCP/Syncro since they were one of the first and they're local shop.

https://www.rogueengineering.com/Rogue-Engineering-E36E46-Monoball-Rear-Trailing-Arm-Bushing-RTAB_p_303.html

[blckstrm]

Those Rogue ones aren't the same as most of the others - they're not sealed. The others all house what looks to be the same ball joint from the control arms. The Rogue one is not sealed. While some of it's unique benefits may appeal to some, the amount of maintenance it would require makes it less than ideal for most people.

...

The question I've got about these is do the Bimmerworld ones clear the mounting bracket, or do they interfere with it since they have a flange on both sides? And how tight is the ball joint inside the housing? Can you unbolt the little hex bolts on the one side flange and remove and replace the ball joint?

Same questions for the Synchro Design Works version from FCP - those look like they're solely press-thru (and seem at lower risk of interfering with the bracket). Can you undo the little hex bolts and get the lid off to replace the ball joint even though it's inside the trailing arm?

[RBNetEngr]

The Bimmerworld RTABs have replaceable bearings, they sell the replacement pair of bearings for $80.


-rb

[blckstrm]

The Bimmerworld RTABs have replaceable bearings, they sell the replacement pair of bearings for $80.


-rb

Makes sense - not that I've looked it up, I'm almost positive they're the same ball joint used in the rear control arms, and those are about $40 each.

I'm going to pull the trigger on these - just need to decide which ones (they all look pretty similar, just need to make sure the flanges on the Bimmerworld ones don't interfere on the bracket). Maybe if you're still on the fence we can meet up and you can see how they feel (assuming you can discount / factor all the other NVH-inducing changes I've got going).

I did find an interesting discussion on another forum discussing the different ball joints used and weaknesses with some of them (someone mentioned a plastic inner race with one of them, which would obviously be a problem pretty quickly).

In general though, the E46 sentiment is far more positive on these than what I'm reading here. Lots of "you won't notice any worse NVH" from that crowd.

I also saw this interesting comment (where "this" was this boll joint solution)



For ride quality: rubber > this > polyurethane

Hit a bump, there's a solid thud, and that's it. With the Powerflex in, it felt more like the car crashes into it.

So from my perspective this should be better than the (offset) delrin RTABs I've got (which are obviously worse than poly). And I can vouch that it absolutely crashes when I hit an abrupt bump or a transition lip. I loved the better rear end control, running 0 toe, but that crashing and the constant squeaking - no matter how much I grease it, I'm just a rainstorm away from the squeak again - have got my mind made up.

I have FLCAs, camber plates, and steering rack / tie rod boots on my to-do list, so I may as well get the rear end in on the action while I'm at it next weekend.

[ScotcH]

Makes sense - not that I've looked it up, I'm almost positive they're the same ball joint used in the rear control arms, and those are about $40 each.

I'm going to pull the trigger on these - just need to decide which ones (they all look pretty similar, just need to make sure the flanges on the Bimmerworld ones don't interfere on the bracket).

Yes, they use the same ball joint. Why would BW sell a part that interferes with the bracket?

[craigjimc]

I have had no problems with the BW RTABS as far as fit, finish & 2000 miles on the road. Highly recommended.

[scoobiedoo2029]

dont remember anyone ever complaining of nvh when installing theise ball joints in the outer trailing arm locations. an upgrade for e28's was to use the lower front control arms off a e31 850 /e32 750 as they had ball joints on the inner location not bushings. both those cars ride like clouds.

[blckstrm]

dont remember anyone ever complaining of nvh when installing theise ball joints in the outer trailing arm locations. an upgrade for e28's was to use the lower front control arms off a e31 850 /e32 750 as they had ball joints on the inner location not bushings. both those cars ride like clouds.

96+ have ball joints in both upper and lower locations (out at the wheel) on the rear. I believe non-M and 95 M3 have a rubber bushing in the bottom location, though that's easy to swap out. I got some aftermarket adjustable camber arms that have a ball joint in the inner instead of the normal rubber bushing. That didn't change NVH one iota.

All my stuff should be here next week - so we'll know fairly soon.

[golgo13]

Those are cool.

I run the ones from Syncro Design Works that can be serviced and use an OEM Saab balljoint 4567244 replacements which are readily available.

https://syncrodesignworks.com/products/rtabs

[RBNetEngr]

Thanks for the feedback. So, for those of you using the Bimmerworld, or similar, bearing-based RTABs rather than the stock RTABs, how much NVH increase have you experienced? My car may see 1-3 track days per year, but much more ‘spirited’ backroad driving.


-rb

[nick325xit 5spd]

It’s a noticeable increase. I plan to go back to stock.

[blckstrm]

I currently have delrin RTABs. They are fine for the most part, but harsh over transitions.

From feedback I saw on an E46 thread, people generally agreed that in terms of harshness they are (from good to bad) stock > ball joint > poly. I'll assume delrin would be worse than poly since it's harder. So I'm hoping this is an improvement, but if not, I don't currently find that aspect of it annoying (but then again I'm in newer Texas suburbs, so most of the roads are nice. I might change my tune if I was driving on crap roads all the time). But I guarantee the squeaking will be gone!

I have these at home, but I'm traveling right now. I will do this next weekend - I'll check back and provide feedback.

Also, I should point out that I've got RTAB pocket reinforcements welded in - I'd think strongly about doing this if I was going with one of these non-factory setups. And in some ways, the poly or delrin RTABs are worse because they don't articulate transversely (not that the rubber can either, but it's softer). The control arms move the suspension in an arc as it moves up and down, so the ball joint can move freely in both the longitudinal plane as well as the transverse plane.

[golgo13]

Oh, the OP was also asking about NVH? I have a gutted track car with straight pipes so I can't help you there. Everything in my car makes some sort of noise.

Good luck!

[blckstrm]

Took me a minute to get these installed - had to refresh my FCAs first.

These accomplished everything I wanted.

Having had everything but poly at this point, I agree that in terms of harshness they are (from good to bad) stock > ball joint > delrin. Poly may be slightly better than delrin, but it's a bit of a not point.

This is absolutely an improvement. More controlled than the delrin, but less harsh. And yes, the squeaking is gone!

I do not find these to be too harsh for the street, but it probably depends on how firm your springs are and what you like.

With new FCA ball joints and these ball joints in back, the car is solid and composed. No clinking, clanking, clunking. No shudders, no secondary impacts or anything. Just immediate dealing withhard bumps, and composure and response for everything else.

[RBNetEngr]

Thanks for sharing the update.


-rb

[blckstrm]

Thanks for sharing the update.


-rb

Next time you're up in Austin I'd be happy to let you drive it. Or next time I'm in SA with the car. I'm usually in the E32 or the Escalade since it's usually a family trip, but sometimes I make trips with just a kid or two.

Maybe a Rudy's halfway in between? ;)

[RBNetEngr]

Sounds good. I am ‘tuning’ my new ST coilovers right now.


-rb