E36 Roll Center Correction Experience(s)

[fbirch]

Good luck with the new kit. I wouldn't be willing to continue using anything that repeatedly loosened up on a part that will destroy the car (and maybe you) if it comes completely loose.

I inquired about Turner's kit a month or two back and they told me no stock until Oct

[MPWRCPE]

Good luck with the new kit. I wouldn't be willing to continue using anything that repeatedly loosened up on a part that will destroy the car (and maybe you) if it comes completely loose.

I inquired about Turner's kit a month or two back and they told me no stock until Oct

If you pick up the Turner kit please report back!

[cledbetter]

I second paint marking the outer big bolt on the SLR. I have had one of them back off some as one side is not quite long enough to engage the metal lock on the nut. I put red locktite on it and re torqued it and been 20+ hours on track with no change.

[aeronaut]

If you pick up the Turner kit please report back!

It would be cool if someone got experience with the Turner kit. FYI, I couldn't find specs on it (amount RC and bump correction) on their web site. Gave them a call, but was on hold too long.

[jonb94118]

Curious - did you ever try using Loctite Red on the nut and seeing if it held?

[aeronaut]

No I haven't. I didn't want to use that until the parts had been cycled/seated, but because they've been coming loose from day 1, I just haven't felt red-locktite is the right answer. I'd probably try that at this point, but the SLR kit arrives Saturday. To be clear, there are 2 problems with the MRT kit. It has a 25mm RC drop, which puts the widest part of the LCA right next to the edge of the rotor (E46 M3 rotor on an E36 M3), and it rubs. And this nut comes loose every 2 days problem.

Hoping the SLR kit (30mm RC drop, bigger bolt/nut compared to MRT) fixes both those problems.

[aeronaut]

Got the SLR kit in. I'll do a better comparison once I remove the MRT kit. For starters, this bolt is 16mm on the SLR kit, 11mm on the MRT kit (which is the one that keeps coming loose).
If the same thing happens on this nut, it's big enough to drill and safety wire, which with my history, I may do from the get-go.

One advantage of the MRT, it can use OEM tie rod ends ( because its RC & bumpsteer correction is ~ 5mm less).

There's a lot going on here, and I think the MRT kit may be fine for some applications (OEM rotors, street application).

SLR-lca-boltnut.jpg

[jdehaan]

My Large bottom nut came loose (despite ample red locktite) again this weekend. Seems to be that it does this every time I go to Mid-Ohio! Anyone try wiring the nut, or using those washers mentioned above?

[aeronaut]

My Large bottom nut came loose (despite ample red locktite) again this weekend. Seems to be that it does this every time I go to Mid-Ohio! Anyone try wiring the nut, or using those washers mentioned above?

That's a bit concerning. IMO, that nut is large enough to drill & safety wire. If you're not up for that, try Nord-lock washers (not cheap, but available on Amazon, McMaster, etc).
Also, double check the torque of the top nut on that stud.

[fbirch]

Got the SLR kit in. I'll do a better comparison once I remove the MRT kit. For starters, this bolt is 16mm on the SLR kit, 11mm on the MRT kit (which is the one that keeps coming loose).
If the same thing happens on this nut, it's big enough to drill and safety wire, which with my history, I may do from the get-go.

One advantage of the MRT, it can use OEM tie rod ends ( because its RC & bumpsteer correction is ~ 5mm less).

There's a lot going on here, and I think the MRT kit may be fine for some applications (OEM rotors, street application).

SLR-lca-boltnut.jpg

How much RC correction does the SLR provide?

[aeronaut]

SLR says 35mm.
MRT says 30mm.
I'll try to remember to actually measure them both.

[dominator293]

Just drill through the nut and bolt when fully tightened and run a split pin through it. Not sure if that's the same theory as your safety wire one.

[aeronaut]

Just drill through the nut and bolt when fully tightened and run a split pin through it. Not sure if that's the same theory as your safety wire one.

This would reduce the strength of the both the nut and bolt. (Safety wiring a nut reduces the strength of the nut but not the bolt.)
This wouldn't allow for minor torque adjustments of the nut. (eg, a need to tighten 1/8th of a turn.)

[Def]

At the end of the nut/bolt engagement it wouldn't be a big deal. If it survived untorqued, it'll survive a tiny .040 safety wire hole in it!

That said, safety wire/cotter pin torquing is usually some minimum torque (like 50% target torque), then turn until you get the holes lined up. So I'd torque everything, then drill, and you're good to go from then on +/- any tolerance that matters.

[aeronaut]

Due to a misunderstanding (my fault), and a part that was manufactured out of spec (SLR's fault), I've emailed SLR and been on the phone with them twice.
Their service and support is stellar. I ended up talking to Shawn for about 15min about various geometry/brake/LCA setups.
Good stuff. Hopefully replacement parts get here this week, and I can get them installed and report back.

One BIG difference between MRT and SLR is the spindle size that bolts through the LCA. MRT=13mm, SLR=16mm. Yea. That feels much better. I have no engineering analysis to support my emotions.

[aeronaut]

The tapered studs used by MRT (top) and SLR (bottom). The 13mm nut on the MRT is the one that kept loosening every 2 days. A NordLock washer seemed to have finally stopped that from happening. However, on removal of this stud, the top nut (16mm) was partially stripped. The MRT spec for that nut is 105Nm. A class 4.8 16mm fastener max tq is 89Nm, a 8.8 class 16mm is 237Nm. I'm confident I never overtorqed that nut.

taperedstuds.jpg

[ScotcH]

omg, that is a massive stress riser where the threads start! Why would the step down the diameter so much? Seems like a bizarre engineering choice.

[aeronaut]

Yep. Agree. And there's no reason for that sudden step down. Other than bearing choice (small ID), and lower machining costs. (Meaning, they picked a small bearing ID, then chose the cheapest way to fit that bearing.)

- - - Updated - - -

Actually...no...I'm wrong.
I have no idea why that step down to 13mm is needed. That's not the bearing ID.

[Def]

It's probably so they can use an off the shelf nut and get more angulation on the spherical bearing. Still needs a giant radius on the lead out of the threads.

Losing torque and preload on that tapered stud probably didn't do any favors for thread loading, with large dynamic amplification factors being reacted by parts of the threads. As those yield, the whole thing is on borrowed time as it keeps getting hammered with these high loads.

[aeronaut]

Good point on the articulation of the spherical, yes, that would allow the nut to be closer to the bearing and still articulate.

[aeronaut]

The saga continues. I'll avoid the details...but I have a technical question. Spacers and spherical bearing; should there be "slack"? See video:

https://www.amazon.com/clouddrive/sh...tries*=0&mgh=1

SLR was to ship a few replacement parts yesterday, but haven't been shipped yet. (Maybe I'm just destined to not have RC correction.)

Also chatted with TMS about their kit. Asked what the RC correction was. They said they didn't know, and that I should contact ECS.
Ok, Chat with ECS. Nope, didn't know. Sent an email, we'll see.

[jakermac]

The saga continues. I'll avoid the details...but I have a technical question. Spacers and spherical bearing; should there be "slack"? See video:

Is there a chance that there's a top and bottom standoff, and you have 2 of the "top" or "bottom" ones together that are too long?

[aeronaut]

Damn I wish. But nope. 1 of each:
IMG_20200929_173812.resized.jpg

[ScotcH]

Looks easy to fix on a sanding disc ... though a lathe would obviously be the right tool to take it down a touch. Of course you should not have to do anything. Sheesh.

[aeronaut]

Agreed, Everytime I look at buying a lathe, I get lost in the "next version up".

I need to remove about 0.3mm.

But jesus....why do I need to make custom spacers.