Rear multi-link bearings

[Joe D]

As some of you may know, SCCA requires the use of factory suspension arms. Does anyone know if the knuckle bearings fit in the arms? SPL says no, but from what I can find they're the same size. I would hate to ruin a bushing on the stock arm just to see if they fit and be screwed sourcing more parts.

[Matt93SE]

What class are you looking at? Club race or Auto X?
different classes allow/require different things.

I did find a solution on my car using Mazdacomp spherical bushings from an FD. I don't have the part number right off, but they're the bushings for the rear multilink from an FD RX7.
the only drawback is that they have a 10mm bore in them vs the 12mm our cars use, but I just bought a 10mm eccentric bolt from something else (I think it was a Jeep?) and made them work.

[Joe D]

The car is built for club racing in Improved Touring S. I was originally going to just build it for NASA, but I would like to be able to switch around and run with either group.

I'm fine with smaller bolts I suppose. A quick search finds 2 options for rear sphericals on the FD. FD01-26-230 is for the toe link and FD01-26-220 is for the upper and lower control arm. Just looking at pictures the FD01-26-220 looks too big so I'm leaning towards FD01-26-230, but it's hard to tell without seeing in person.

[Def]

If it were me I'd just go custom and do something with a steel sleeve welded to the arm and a -8 COM-T bearing epoxied (Loctite 620 Bearing Mount, clean both surfaces, scuff well with 40-60 grit, clean again, apply liberally - it'll hold forever since all the loading is in tension).

The COM-8T is 1.000" OD. I've used quite a few different brands, and like the QA-1s personally.

[djsilver]

http://www.improvedtouring.com/forums/forumdisplay.php?f=58

The IT forum is not as active as this one but the guys there will be happy to share what they use. Thanks!

[Jason M]

I have some oem s13 steel rear spindles with custom fit sphericals, and some oem arms that I've started to fit bearings into. I don't think I'am going to use them. They are only half way finished right now, but I can finish them up for you if you are interested.

I used Qa1 com-T, -8 bearings in the spindle that is finished, they are custom fit for each hole, so retaining compound is not necassary. I have a bunch of surplus wide series aerospace bearings for the control arms, but I can use Qa-1's if you would like. All of my bearings are in 6061-t6 housings, retained by snap rings, and the high misaignment spacers are custom made 7075 aluminum, which machines up nice, and is much stronger then 6061 t6. The 7075 spacers won't get close to the yield point like 6061 when the suspension bolts are torqued down to spec. From my experience 7075 spacers will not gaul like 6061 spacers, so they stay looking pretty for much longer, even after multiple disassemblies..

[T-Rex]

You are allowed to tack weld in the spherical bearings as well these days, per the rules.

I used the same size bearing in both the knuckle as well as the control arms, although from what I remember off hand ( and I may be wrong) the RLCA require a larger bearing.

You can also use delrin in the RLCA as they only move in a single plane.

[Matt93SE]

Def, problem is the class rules don't allow modification of the arms and such. you can replace the bushings, but you can't modify the arms to make a different bushing fit. At least that's my understanding of the ITS rules without going back and reading the manual.

the FD RX7 bushings I used pressed right into the stock arms and voila. With the rubber bushing moulded into them, they're sealed from environment and everything, so are OEM quality and longevity, with the benefit of being a spherical.
you also get the benefit for SCCA of being mashed into an unmodified arm, which is their rule.

[Def]

Is a tack weld modification though? Like T-Rex said, I thought this was a common practice in ITx.

[Joe D]

OK, so going off what Tristan and Matt said, I removed a bushing from a traction arm and verified fitment of SPL knuckle bearings. I don't know why SPL said they wouldn't work, but they are in fact the same. I guess I just needed a little nudge in the right direction.

Def, the tack weld is specifically allowed in the rule book. No other modifications are allowed.

[Def]

Still missing where the cheap custom getup I talked about wouldn't work then...

But sometime it's easy to underestimate the value of just hitting the easy button when modding a car.

[Matt93SE]

Tack welding a bushing into a stock arm is fine. Modifying the arm by cutting off the end and welding a new housing onto the end is co queered modifying the arm. At this point who can tell if you shortened the arm or lengthened it by welding in a larger bushing onto the end, so the center of the bushing is effectively farther from the stock end.
The reasoning is that changing the length of any arm is expressly prohibited, but bushing material is free.
If you go to a metal bushing, you need a way to secure it. Thus you're allowed a tack weld, but not replacing an entire sleeve.

[Def]

Reread my original post. I talked about making a bearing sleeve that gets tacked to the arm in the stock bushing bore that has a 1" ID that you then epoxy a COM-8T spherical bearing into.

Same thing as the SPL bushings for like $10/arm. Hardest part would be ghetto'ing up some misalignment spacers, as nothing off the shelf will work.

[Joe D]

So going off of Def's thinking, I could just go with this http://www.midwestcontrol.com/part.php?id=2578 Since the bore is 30mm it should fit perfectly. Then I could use Locktite 680 to secure it in place and then rig up the spacers.

[Def]

I'd have to look at the arms to determine which one to use, but the COM-8T would just need 1/2" bolts and opening up the subframe holes just a hair. They're smaller on the OD vs. the M12 COM's, so it's easier if you need something smaller in diameter.