Redoing my suspension and I have the choice between stock rubber bushings everywhere up front or Polyurethane bushings. I've heard they improve feel of the road and cornering capability. Can anyone who's had both types on the same car speak about how much of a difference in road feel they felt and was it noticeable enough to justify the price? (in my case 120 dollars more) don't care about comfort I'm simply looking for benefits to spirited driving. Thanks.
Don’t do it. Urathane bushings ruin a car. I did it to my CSP Miata and it was awful. They squeak, the ride is harsh, they just make a car unpleasant. So unless your ride is chasing the last few thousandths around the cones, skip it and stay with rubber bushings.
I liked them in my BMW 2002. I was chasing time around cones. The car was already noisy enough to mask a lot of what the bushings added, I think.
I haven't driven that car in a long time and have spent some time in newer vehicles since then. I do wonder in my older and more spoiled state whether they'd bother me more.
I suspect it's one of those things that depends on the application significantly, and how squishy the stock bushings are.
I've had full poly on my last three daily drivers, plus a handful of project cars.
They feel like you have maybe 10-15psi more air in your tires, and do feel slightly more precise.
They do end up with a bit of "sticktion" where they don't really want to move initially. They also squeak - I've tried it all, ES grease, synthetic grease, moly grease, never-seize, (though I haven't tried wrapping it in teflon pipe tape, that one is new to me), they still squeak, worse the colder it gets.
They are also now a sliding service, which -should- be occasionally disassembled and re-greased and eventually replaced. I dutifully disassembled and re-greased my B13 Sentra every year (6 years), and on my D21 Hardbody I never went in there again (7 years), and my current '77 C10 (5 years now) have never been re-greased - it's "scrunchy" over speedbumps, just ignore it.
"Ride quality," though, is a subjective thing. What one person can put up with another person can hate; it will depend on you.
I will likely continue to do Poly on my own vehicles, but I usually discourage people from doing so.
I had a STS miata full of poly bushings. I also drove another one with essentially the same suspension but all stock rubber. The difference was noticeable but not life changing. I was just as fast on course in the rubber bushing car though it did feel a little bit less precise. I definitely liked the rubber car better on the street though. I never had any squeaking issues (at least not that I could hear over the road noise of a miata with sticky tires and aftermarket exhaust) though the PO had installed grease fittings along with the bushings. I definitely recommend doing that if you go the poly route, it turns yearly service from a week of disassembling and reassembling the suspension to about half an hour with a grease gun. All in all I'm not sure poly is worth the extra money on anything less than a purpose built autocross/track car or the stock bushings are particularly squishy or prone to failure. On a miata it's easy to justify because you basically can't buy stock bushings anymore so poly is way cheaper.
I would say it really depends on the car. A very popular upgrade for new (R50/53 & R56) MINI's is to replace the problematic oil-filled rubber LCA bushings with a poly option. I've don't this on a lot of cars and no owner has complained about a change in ride quality.
Changing to poly bushings on a Triumph Spitfire doesn't seem to adversely affect ride quality, although the car isn't exactly smooth riding to begin with.
I have them in the front of my AE92. Frankly there was no noticeable difference in ride quality, handling, or noise, but the car was already on rock-hard coilovers, so it might've been that any difference the bushings made was small in comparison.
The big difference is in longevity, that car used to wreck rubber LCA bushings within a year of autocross alone, and I'm on at least my 3rd season of autocross and track days with the poly bushings.
Also a great place to use poly bushings is on the steering rack, they'll help tighten up the steering a bit with no meaningful potential for NVH problems.
One thing to consider, depending on how the control arms and sway bars are configured is what Polyurethane will do to the movement of the pieces.
Sometimes poly can make things worse. Not all the time, but often if you can use poly without causing binding, etc. you can fit metal spherical joints and have even more precision and ease of movement.
Things like motor, transmission, steering rack mounts generally make a lot of sense.
Stefan said:One thing to consider, depending on how the control arms and sway bars are configured is what Polyurethane will do to the movement of the pieces.
Sometimes poly can make things worse. Not all the time, but often if you can use poly without causing binding, etc. you can fit metal spherical joints and have even more precision and ease of movement.
Things like motor, transmission, steering rack mounts generally make a lot of sense.
That seems to be why on a lot of double wishbone Hondas it is recommended to NOT use poly. Most seem to recommend rubber or for racing purposes spherical bushings instead.
I have a steering rack, transmission, rear diff, and rear subframe bushings on my FRS. Made a pretty big difference. No more slop and everything seems much more direct (e.g., inputs seem to be faster, and I can react faster to something like the rear coming out). I also have no noise. Not sure if this is the case but maybe more of the noisy poly bushings come from the sway bar bushings given the constant movements/twists?
That's one thing I forgot. The biggest difference I ever saw from polyurethane bushings were subframe bushings on an E30. Totally eliminated nasty wheel hop on my autocross launches.
Bushings which are just isolators and don't have to accommodate rotation seem like a less compromised fit for polyurethane, at least avoiding sliding motion on a material arguably not well suited to it.
I don't know what type of car the OP is referencing, but for a Miata I'd recommend the IL Motorsports rubber bushings. They're stiffer than OEM but don't have any of the downsides of poly. I did my last Miata with them.
I think it depends on the car, and the suspension design and geometry whether poly bushings will make the ride harsh. I put some on my front lower control arms on my old E36 BMW, and it did nothing to diminish the ride quality, but it exponentially sharpened the steering response mid-corner. I also happened to forget to grease them, and they didn't squeak. Since the OP said they didn't care for comfort, I would suggest to go with poly. However, I would suggest that you only switch if you owned your car for a while, so you can notice the difference.
I put some in the rear knuckles of my MN12 when I did a disc brake swap. Felt fine.
Put some in the front upper control arms. Felt fine.
Put them in the steering rack. Felt fine.
Put them in the lower control arms. Felt awful. Hated it.
I made the switch to poly bushing when refreshing a Miata suspension before turning it into an Exocet. Truly the only decision that I made that I wish I could rethink., as I hate the harshness and noise vs. rubber bushings.
my old 318ti was fully polybushed. I never had any squeaks, but with the PSS9 coilovers, I could feel every pebble on the road. It was not a car for going long distances with. You could turn and stop on a dime, and tell which side was up
In the Fiat 124 application that the OP has I would leave the front on rubber, but I would go poly on the rear upper trailing arms. Only the uppers, the lowers need the extra compliance of softish rubber to prevent fatigue failure on the lower arms. The Fiat rubbers in the front are small area and limited enough in original compliance that the improvement from poly is negligable. More important is to insure the condition of the steering idler (no rack here) and the quality of the ball joints. Many ball joint failures I have seen/ repaired on these cars, never rubber bushing failures.
In reply to TurnerX19 :
Happy Birthday.
Depends on the car. A lot of non-enthusiast older cars will have absolute E36 M3 replacement rubber bushings available.* Also, in some cases the rubber bushings (bonded to a steel sleeve) is an epic pain in the ass to install, where a 2 piece poly bushing is a piece of cake.
Poly can improve the way a car feels and drives. But it degrades a lot faster, is susceptible to squeaking, etc. I wouldn't hesitate to do it to an older car where the only options are what is shown on Rockauto. But if OEM-ish, or hard-than-oem rubber bushings are available, I'll take that route every time.
* Depsite being a simple (in most cases) cylinder made of rubber, there is a lot of R&D that goes into rubber bushings. Especially in the chemistry, which others can't duplicate easily at all (see-also E36 M3ty tires). Aftermarket replacements are made to a price with near zero R&D beyond matching the dimensions (sorta). It results in stuff that is tolerable for the average guy just trying to keep a 20 year old beater on the road, but for GRM types they are often inadequate.
I put poly bushings in my Miata and honestly the car is so uncomfortable with 800/500 lbs springs anyway it doesn't make that big of difference. I also installed zerk fittings so I can re-grease them easily.
I've done zerks in the past, but I find the fit is so tight that the grease doesn't get in there well, if at all.
Mind you, a recent poly install showed that they've since put grooves in the bushing for the grease to go, so the times might be a-changing.
TurnerX19 said:In the Fiat 124 application that the OP has I would leave the front on rubber, but I would go poly on the rear upper trailing arms. Only the uppers, the lowers need the extra compliance of softish rubber to prevent fatigue failure on the lower arms. The Fiat rubbers in the front are small area and limited enough in original compliance that the improvement from poly is negligable. More important is to insure the condition of the steering idler (no rack here) and the quality of the ball joints. Many ball joint failures I have seen/ repaired on these cars, never rubber bushing failures.
Agreed on all counts. The bushings on the A Arms are quite small with very little rubber between the sleeves. In the rear Compliance is needed as the axle will want to twist with torque and poly will not allow for it. You take a big chance with bending arms or ripping off mounts
I have them in the MGB and like the way they work compared to factory rubber. Truth be told, unless they crawled out and stabbed me with a shiv, it would be hard to differentiate any bushing specific NVH over the rest of the riot.
Must admit that this thread is not making me comfortable about having replaced the rubber stuff in the Molvo with poly. $400 USD for the rubber seemed like a lot of $$ at the time.
Pete
In reply to NOHOME :
IMHO, for anything chassis (Miata) related with the Molvo, I would not pass Go and deal directly with Keith at Flying Miata. Especially since he has basically done all of this before with his BGT.
SkinnyG said:I've done zerks in the past, but I find the fit is so tight that the grease doesn't get in there well, if at all.
Mind you, a recent poly install showed that they've since put grooves in the bushing for the grease to go, so the times might be a-changing.
IME Zerks help a bit, but don't really solve the problem because the grease finds a single path through the bushing to escape the pressure. So it lubricates maybe 30% of the total rotation area.
One solution that looks interesting is replacing the solid steel sleeves inside the poly bushings with a pair of oilite sleeves. Instead steel-on-poly rotation that gives you oilite-on-oilite which is self-lubricating. I have a set of these on my Miata, but I haven't really put enough miles on it yet to comment on how well it works.
Delrin solves the squeaking and stiction problems without needing lubrication, but it's even firmer than poly and can't be used in bushing locations that need to rotate in more than one plane because it will bind.
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