CMP 12May12

#1

Fred and I spent the day at CMP instructing with Turn1. I was incredibly slow. Incredibly slow. I noticed that the rear end felt “wiggly”. It turned out that 6 of the 7 bolts that secure the rear subframe were loose. Only the diff carrier was tight. Let that be a lesson to us all. I tightened every one of those bolts up to spec when I installed the rear end a couple months ago.

I think that maybe the rear subframe takes some time to work itself into it’s final position after installing. There probably needs to be an SOP where after you install a rear subframe you go back and hit all the bolts after your first track day. If that’s the case, you won’t want to install the subframe and then use locktite on the fasteners, because once the subframe moves around a bit the fasteners won’t be tight any more. Using locktite during a later “nut and bolt” might work tho.

I was pleased to note that my suspension stayed true. Fred’s rtabs didn’t stay tight tho and he’s got one of those snazzy Ireland rear subframes with the serrated adjusters.

There were a lot of beautiful restored muscle cars at CMP for the SpeedTV reality show “Are you faster than a redneck”, or something like that. The show’s producers have been posting at NASA forums for months looking for participants. The cars were beautiful, but as much as their brakes and suspensions were upgraded, they still seemed to have problems with stopping and turning.

#2

That just makes me more convinced that my theory as to why the adjusters move is correct. The serrated plates aren’t going to move unless the bolts loosen, but the rotational movement of the trailing arms will loosen the bolts if those forces get applied to the bolts.

Preventing the bolt from rotating has proven to be the solution for me. I have a lot of track time on the car now and the adjusters haven’t moved at all. Before I’d have to tighten them after every session, and frequently have to realign the rear wheels after a session.

#3

Yep, that’s exactly right. I had (after reading the RTABs thread) marked the bolts to see if they were rotating and sure enough they (well, the right side one anyway)had rotated about a 1/4 inch. That wasn’t enough for the adjusters to move (thank goodness) but I’m going to have to keep that bolt from rotating…

And FYI, Ranger is right about the subframe bolts - a couple of mine were less than tight after the first track sessions. And I had torqued them to spec.

#4

When installing the bushings, they should be greased with a MSO2 base grease so the bushing will rotate on the bolt, not in the trailing arm. No force = no rotation . CB

#5

Been there, done that, and it didn’t help. A positive lock on bolt movement did solve the problem. The forces that can be applied to the toe adjusters are pretty large. So it isn’t a surprise to me to see the bolts move.

#6

Been there, done that, and it didn’t help. A positive lock on bolt movement did solve the problem. The forces that can be applied to the toe adjusters are pretty large. So it isn’t a surprise to me to see the bolts move.[/quote]

Jim, does tack welding the eccentric washers do the trick? While prepping for Putnam Park, I found that my car developed 3/8" toe out. I adjusted accordingly, but haven’t checked for change after the race. If it moved again, I plan to weld something…

#7

The one time I tried tack welding the eccentrics the tacks broke when the bolts loosened. And the nuts were MIA (I stole parts off the trailer to make it through the weekend). Now if you welded the bolts to the eccentrics and the eccentrics to the brackets, maybe… But that sort of means that the next time an adjustment (or TA replacment) is needed major surgery is going to be required. And since the trailing arms on these cars have the approximate strength of wet spaghetti…

#8

There should be three parts to the bushing. The bolt with nut and eccentrics, the sleeve, and the bushing. The bushing should be a fairly tight fit on the arm. The sleeve needs to be STEEL because all the clamping force from the nut is on this piece and that is the only thing that holds it in place. Lubricate the interface between the bushing and the sleeve. I use 1/2-20 bolts on mine, and Jet nuts. One eccentric is fine…it is just used to move the adjustment, not hold things in place. You can, however, tack weld the eccentric in place…have done it for years without problems and it will keep the bolt from sliding in the slot. The alignment guys look at you funny when you show up with a die grinder and cutoff wheel so he can align the car. Chuck