Hey Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
swift6
Yoda
Offline
There can be a real difference between rubber and poly. But Peter is right that our cars will also be more sensitive to profile changes. I have been able to compare my TR6 back to back with 'stock' TR6's on several occasions. I have a mix of poly and rubber in the front suspension, poly in the rear, rubber on the diff, poly on the sway bar, solid steering mounts, fast road springs, KYB's on all four corners and 195/65R15 tires. Compared to my car, 'stock' TR6's (in regards to suspension, tire size, etc...) feels more like a Buick to me than a Sports car. However, there are several factors at play in that comparison.
Solid Steering rack mounts:
The biggest factor in steering feel is the difference between rubber vs. solid steering rack mounts. HUGE.
Ride Height:
The ride height change, my car sits a full 1.5 inches lower than a 'stock' TR6, is also HUGE. Lowering the roll center is a very noticeable change. To me, it was well worth the trade off of being very careful of steep driveways and big speed bumps due to the reduced ground clearance.
The fast road springs, with their reduced height and increased spring rate also lessen the need for a rear anit-roll bar.
Rear tube shocks:
Tube shocks on the rear are smoother riding than the lever arm shocks, especially when compared to the heavy duty units I was using to work with the stiffer springs. The difference was most notable on long sweeping, high speed corners.
Poly Trailing Arm bushes:
I've said it before, I'll say it again, I feel these should be mandatory in TR6's. The original rubber bushes allow so much flex in the trailing arms that the rear tires can actually point in slightly different directions in corners. Have you ever gone through a corner quickly and felt the rear wiggle or get unsettled sapping any confidence for going faster? Poly here will almost eliminate that. Roller bearing units here that are available in the UK completely eliminate it.
Tire Profile:
As well as contributing to small changes in ride height, lower profile tires transmit more shock but due to the stiffer sidewalls also have better transient response (side to side), ie better handling. I was driving another TR6 once and the owner was bragging about his new tires and how much he loved them. They were a 215/75R15 major brand name tire. As soon as I began to push the car in some corners I could actually feel the sidewalls start to roll. I have never felt that with my 195/65's. Modern tires in 70-75 profiles are generally not sports oriented tires. They are usually 'Touring' tires which mean soft sidewalls for comfort over handling. 65 Profile tires straddle that line between performance and touring.
After all that, mixing poly bushes into the suspension will tighten up response, firm up the ride and transmit more NVH. Squeaking can be eliminated with a good synthetic lube. By themselves, poly bushes will only "transform" a worn out rubber suspension but so will new rubber.
You have to decide what you want and how you intend to use the car. When I set my car up I was doing quite a few track days. I compromised on the set up, not going full track ready but keeping some idea of comfort in the mix as well. But my approach, as detailed above, was far more than just poly bushes. I do know a few people who seem to be pretty happy with all poly bushes with stock size tire, springs etc... Using the polys to increase their feel and soft(stock) springs and high tire sidewall to provide the comfort. They generally use their cars as cruisers, for relaxed and comfortable driving. I'm a bit more agressive with mine. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif When traffic permits of course. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
Solid Steering rack mounts:
The biggest factor in steering feel is the difference between rubber vs. solid steering rack mounts. HUGE.
Ride Height:
The ride height change, my car sits a full 1.5 inches lower than a 'stock' TR6, is also HUGE. Lowering the roll center is a very noticeable change. To me, it was well worth the trade off of being very careful of steep driveways and big speed bumps due to the reduced ground clearance.
The fast road springs, with their reduced height and increased spring rate also lessen the need for a rear anit-roll bar.
Rear tube shocks:
Tube shocks on the rear are smoother riding than the lever arm shocks, especially when compared to the heavy duty units I was using to work with the stiffer springs. The difference was most notable on long sweeping, high speed corners.
Poly Trailing Arm bushes:
I've said it before, I'll say it again, I feel these should be mandatory in TR6's. The original rubber bushes allow so much flex in the trailing arms that the rear tires can actually point in slightly different directions in corners. Have you ever gone through a corner quickly and felt the rear wiggle or get unsettled sapping any confidence for going faster? Poly here will almost eliminate that. Roller bearing units here that are available in the UK completely eliminate it.
Tire Profile:
As well as contributing to small changes in ride height, lower profile tires transmit more shock but due to the stiffer sidewalls also have better transient response (side to side), ie better handling. I was driving another TR6 once and the owner was bragging about his new tires and how much he loved them. They were a 215/75R15 major brand name tire. As soon as I began to push the car in some corners I could actually feel the sidewalls start to roll. I have never felt that with my 195/65's. Modern tires in 70-75 profiles are generally not sports oriented tires. They are usually 'Touring' tires which mean soft sidewalls for comfort over handling. 65 Profile tires straddle that line between performance and touring.
After all that, mixing poly bushes into the suspension will tighten up response, firm up the ride and transmit more NVH. Squeaking can be eliminated with a good synthetic lube. By themselves, poly bushes will only "transform" a worn out rubber suspension but so will new rubber.
You have to decide what you want and how you intend to use the car. When I set my car up I was doing quite a few track days. I compromised on the set up, not going full track ready but keeping some idea of comfort in the mix as well. But my approach, as detailed above, was far more than just poly bushes. I do know a few people who seem to be pretty happy with all poly bushes with stock size tire, springs etc... Using the polys to increase their feel and soft(stock) springs and high tire sidewall to provide the comfort. They generally use their cars as cruisers, for relaxed and comfortable driving. I'm a bit more agressive with mine. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif When traffic permits of course. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
