RE: trailing arm bolts

[Darryl Tinnerstet <darryl@xxxx>]

Walt said:
> the problem is more than weak
> bolts and soft washers. Additional weak components include the metal sleeve
> in the rubber bushing and the rubber bushing itself. If a trailing arm bolt
> is over-tightened, then the sleeve in the bushing starts to crush. At
> proper torque, the sleeve is only a couple of foot-pounds away from
> crushing. As for the rubber bushing -- I do not like the idea that two
> little rubber doughnuts are transferring most of the engine's horse power to
> the chassis. This rubber permanently deforms with use. Rubber has many
> good uses, but not here!
> 
> Toby, if you are going to come out with a kit of new bolts & washers, how
> about coming up with a new bracket that holds the trailing arm bolts from
> both sides? This should significantly reduce the bending force on the bolt
> by reducing the length of the lever arm (effectively cutting it in half).
> Also, I see no point in even having any rubber in there. Wouldn't a steel
> bearing make more sense?

Some years ago there was such a bracket available. But unfortunately the
answer isn't that simple. If you look at the geometry of the rear
suspension you will notice that the upper and lower links are a different
length. I believe the purpose is (remember I'm a civil, not mechanical,
engineer) to make the contact patch of the tire remain in the same relative
position on the ground as the tire moves up and down. But by so doing the
trailing arm which extends forward must then twist as it moves up and down.
Something in that forward joint must be able to flex. 1963 and later
Corvettes solved this problem with a rubber bushing in the end of the arm,
with the bolt supported on both ends. They survived huge amounts of HP,
torque, and tire smoking. But for whatever reason DMC/Lotus put the rubber
bushing on the frame, requiring the outer end of the bolt to be free to
slightly move. If the rubber bushings are in good condition, and the new
bolts properly torqued, the factory setup should function as designed. Its
just when the soft original (or currently available replacement) bolts begin
to stretch and bend that you have problems.

Personally, when a Boeing structural materials engineer and hard driving
DeLorean enthusiast of many years says the old ones are a problem and then
goes to this much trouble to have the best possible ones custom made, I
would tend to believe him. This is not a profit driven venture. It is
totally based on his desire to provide other owners with the best possible
remedy to a serious problem. He/we will barely be making enough to cover
phone calls, packaging, going to the P.O., etc. - and if they don't sell we
are stuck with having fronted the production cost. It will only happen,
though, if he gets enough positive responses.

-- 
Darryl Tinnerstet
Specialty Automotive
McCleary, WA