More of a philosophical rather than practical question, but ......... what do the top suspension mounts actually do ??
I recently had cause to dismantle my front suspension and mine were OK - almost certainly fairly recently replaced by a previous owner but I know that they are made of a special short-lasting foam gunge which degrades over a ridiculously brief period of time.
I can't see that they have any "vertical" function - the spring and shock absorber (damper) takes care of that, and there's a quite sophisticated bush - more like a universal joint - on the bottom of the damper to accommodate the fairly small amount of lateral movement in the suspension.
I can only think they are for accoustic isolation - in which case, pretty much anything non-metallic but very firm, ought to be suitable material.
Any thoughts Oh Wise Ones ????????

 

Dave, I agree with you analyzes on the mount, but what don't we know? I have been wanting to try the poly mount on someone's car, but most want to keep it as is. Mine are fine, as they were replaced sometime ago.


Wayne

 

After replacing the top mounts there was a noticeable improvement in ride quality on rough roads. Poly mounts would feel harsher, but I know many owners would like that. More sports car than touring car.

 

RJ237 - If your old mounts were on their way out, then I am not surprised that ride quality was better after replacement. My point is more that I can't see why there would be any noticeable difference between (for example) Jaguar crumblegunge (when new), hard rubber, polyurethane, nylon or indeed any other very slightly flexible material when there's so much vertical movement in the damper / spring assembly, and provision for a small amount of lateral movement in the lower bush.
As I say, more a philosophical than practical question, but this one comes up so often that I thought it worthwhile to seek other opinions.

 

David, the ride quality on these cars are effected by almost anything you do. I went from 17" to 18" rims, same tires (tyres) and didn't have to go a block to know the ride was a little firmer. If I went to poly and back to 17" would it be the same as it is now?
I can see heavy duty shocks, poly mount and lower springs could make the ride uncomfortable for street use, but I'm not convinced the average driver would know if they had poly in the mount.


Wayne

 

2 cents: While the spring and damper (shock) work in unison over bumps anyone who's replaced the upper mounts knows compressing the springs are pretty stiff (I think xkr are a bit stiffer than xk8) that said any movement within that mechanism is going to be forced to the mount to some degree and having a donut on the top would provide a bit more suppression of these forces, easier on chassis and driver. Now what they are made of or replaced with would be up to the mechanic and what he wants his drive to feel like. Jaguar probably used a compromise between function and cost with materials available at that time and ended up with a product that dries and crumbles over time/heat/pressure. I've replace mine but maybe going back in the next year or two for new springs since my ride height is still low (15"), not something I'm looking forward to, I might need a bigger compressor before hand to compress the springs quicker (always a good reason to ask wife for a new tool ;-)
Yes a bit philosophical but I'm not a mechanical engineer, just a garage dog.

 

replaced mine with the poly rebuild kit from motorcars limited and don't really notice any difference other than its flatter in the corners now because the top of the shock doesn't wiggle anymore in the mount .

 

This kit looks good, I wish I had used it when I rebuilt mine.


mja2170bd.kit - Shock Mount Bushing Kit

 

RD, then that takes care of that, poly it is, when the time comes.
Jamdmyers, do yourself a favor and get a 20 ton press from HF, or look out the estate sales, something to do over the summer and keeps the wife entertained. They sale cages to make it safe, and you can do bushings and help your buddies out.


Wayne

 

can rent a spring compressor from orielys auto for nothing just a deposit required which is refunded when you return it...it is time consuming and a lot of muscle work but free. another option is to remove the assembly from the car take it to a shop and have them compress the spring and disassemble... rebuild the mount (may want to add a new shock while at it seeing as the lower bushing is probably loose ) and then have them reinstall the parts. also may want to mark on the mount a center position in relation to the lower shock bushing so when you reassemble the upper bolts are in the same position to the lower bushing... saves trying to turn it a lot to realign. also when retightening or reassembling the shock make sure you hold the top part of the shock shaft in place while tightening the top nut ...I didn't and had a rattle for about a month before I found that it wasn't completely tightened down due to the shaft spinning while tightening ... another thought while everything is apart is to replace the upper whishbone bushings(upper control arm bushing)... I pressed mine in using a c clamp was very easy to do. make sure its the original style bushing some of the aftermarket bushings are a different style and are much harder to replace.