JoeSimcoe@aol.com wrote:
>
> To all,
>
> Shane asked:
>
> <<Apparently, the down-side
> of this material is that it compresses after 10-20K miles and
> never returns to its original shape, allowing a lot of free-play
> into the system. I've not heard if this is true of the urethane
> bushings.>>
>
> I have been told - i.e. not first hand experience or any scientific evidence
> to this fact - that indeed nylatron will compress over time and not "rebound"
> to its original shape.
>
> My source (British Parts Northwest - I didn't say that) opined that indeed
> Nylatron would be better for a race/autocross car where you would need the
> additional toughness of Nylatron and where you would be changing out the
> bushings regularly - but that for the average Joe (pun intended) poly would
> be better as it "rebounds" keeping its round, and under normal average
> driving conditions will outlast the car, or at least outlast me.
>
> Just my opinion, and I know that there are a couple of folks out there that
> disagree with me. Thats OK, no hard feelings.
>
> JoeSimcoe
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I agree with Joe that the Polyurethane would be the wise choice for
overall usage. Just purchased all the urethane bushings for my TR6 (74)
including the differential mounts.
I think Mark had some negative comments on the urethane that were
important to note. These comments, I thought, regarded the fact that
many suppliers of Poly bushings do not incorporate the inner metal
portion of the bushing. The BPNW bushings for the lower control arm
(front) do include the inner metal just like the stock rubber and the
trailing arm bushes also include these inner metal pieces. The purpose
of the inner metal in a rubber or urethane bush is to allow for a clamp
load to be achieved when torquing the bolt across the clevis bracket.
Without this inner metal no reliable torque setting can be achieved.
The upper control arm bushings do not have inner metal and the torque is
reached when the castle nut bottoms on the shoulder of upper control arm
pivot.
Despite buying all the urethane bushes from BPNW I still needed the
trunion to lower control arm bushes and they are still experimenting
with their supplier on these. In there place, I stopped at Detroit Ball
Bearing ( a large Bearing supplier in the Midwest and picked up 4 brass
bushings 7/8" O.D.- 9/16" I.D. and 1" in length. No compliance with
these and they fit great (also used brass thrust washers). This car is
for Autocross and the target was little or no compliance.
On the urethane Steering Rack bushings I 'm saving them for my 71
stocker, which has lots of lateral movement. I bought the aluminum rack
mounts from Moss.
>From a cost standpoint the Nylatron may be better and costlier, but the
urethane will probably meet your requirements. I have a full set of
urethane bushings on a CJ8 Scrambler (thats a Jeep) that I just finished
a frame off on and they are holding up fine. I did use liberal amounts
of silicone grease. Rumor has it that when the lube is gone they SQUEEK!
Glenn Franco
71 & 74 TR6
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