I just replaced my whole front end with a PST polygraphite kit. Polyurethane is obviously superior for the suspension bushings. Now comes the subframe and radiator bushings. Is there an advantage to using poly on these as well besides the longevity factor? I'd like to keep the ride from getting too harsh and was wondering if the rubber ones might not be a better choice here? I'd like to isolate noise and vibration as much as possible.

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Shawn Peterson
1969 Z28, 406SB

Everything I have read says go with the poly subframe bushings. I do not think the radiator bushings would matter (not part of handling). When I do my subframe bushings I am going with the poly.

I did PST front end, subframe, and rear leaf bushings all Polygraphite.

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70 & 1/2 RS
SB406 & M20 4spd
9" rear

70 Malibu 350/TH400

Gold member #103

shawn i can't see any advantage to installing poly. body mounts other than lasting longer but the factory ones have lasted 30 yrs.i'm going to use factory replacements for all body and poly. for steering and susp. and save some money.

Poly bushings will help stiffin up your car which will reduce body twist. Better handling and acceleration characteristics. Plus they will last longer. I havent gotten mine on the road yet, (I installed poly) but I've heard there is not a very noticable differance in ride quality.

Austin is right on track with his handling observations. The stiffer the body to subframe connection the less chance there is of changing the steering and tracking geometries. On Trans-Am racing f-bodies the original rubber bushings were replaced with aluminum in order to minimize these distortions. As for the differences between rubber and polyurethane, I drove my '68 as a daily driver for 10 years with the rubber bushings all around, and now that I have polyurethane I wish I had changed years ago. The only drawback that is the small annoying rattles in the passenger compartment will become more persistant.

Shawn - I have poly bushings everywhere they'll fit on my '69. (I also cut my coils and changed a bunch of other suspension stuff.) It does ride a bit rough and starts up squeeks and rattles here and there but I think a lot of that is because: 1) the bushings are not the graphite type; 2) the springs are cut and therefore much stiffer; and 3)I also have 17" Comp TAs which give away a lot of sidewall mush that the taller tires have. But it handles great!

My recommendation is to use poly everywhere - especially the subframe because it limits flex of a major structural component.

i too would suggest all poly, except the radiator mounts. save your money on those. I replaced all the bushing in my 79 with poly as well as heavy duty springs. well almost, i used solid alluminum front eye bushing in the leaf springs (drag racing). the poly did increase the rattles and harshness a little and i do get an occasional squeak (i think that it is from the A-arms). the upgrade was well worth it though, it's so tight i can drive over a quarter and tell if it is heads or tells.

josh

tails..

The complete energy suspension kit cames with all the subframe mounts and the radiator core support mounts as well.