Polybushes - Any Good?

[untakenname]

I'm not sure if it's the same with the MX-5 but Mazda use interleaved bushes on the RX-8 which is basically a metal tube that floats in the middle of the rubber which gives far more radial stiffness than even the hardest rubber polymounts whilst still leaving a degree of compliance on the roads.
People tracking their cars (me included) have learnt the hardway that poly isn't always better, I polybushed quite a bit of my car last year and as soon as it warms up I'm going to revert back to oem as the NVH with poly is jarring on the road and offers no benefit on the track.

[SebringMan]

MiniCooperYes said:

You need those rubber polybushes

Or simply not going to the cheapest stuff you can find.

I'll be honest, I was of exactly the same thought. A few cars I have owned haven't helped here.

What did? Going to SuperFlex on my MGB and driving other cars with their bushes. Here are my examples.

-MGB : I had rubber bushes as everyone knows as loves. The back of that car was so firm that it was terrible! I went with SuperFlex bushes there and even on Spax dampers and 8Jx15" Minilites it was one of the nicer MGBs I drove ; speed bumps weren't a chore ; I finally had a 'B with the rear suspension as pliant as the front. Of course the forums made out my setup was terrible and I ummed and ahhed for a long time.

-Triumph 2.5PI Mk1 : This car had been through a couple of known Triumph hands (Including Canley Classics and maybe even Chris Witor). Despite it being lowered on the CW springs and on KYB dampers on those SF bushes the car throughout just glid over bumps! I really was shocked at the ride quality. Sure it wasn't a Citroen DS but it was not as far away as you'd think! I could have driven that car all day. I've not to this day driven another Triumph Saloon as comfortable or as controlled as that car ; that for me was the convincer. It's a shame I didn't buy the car when I had the chance!

But I'll agree , my other cars on poly bushes have been medicore, but both were on the cheapest kits you could buy ; a Triumph Spitfire kept shaking itself to bits and the Mazda seemed a little busier than it should. Someone on Youtube did compare PowerFlex bushes with SuperPros on an MX-5 which was very interesting to see ; the PFs would have you having a semi seized arm in place ; the SPs (SuperFlex are the same people in most respects) actually allow the suspension to do what it was designed to .


Most people won't go with SuperPro/Flex since they are not what you'd call a bargain. They're working a charm on my M3 for subframe bushes mind you and get around an issue with the factory bushes (the stock ones rub on a spot weld which of course doesn't help with their habit of boot floors falling out.

Edited by SebringMan on Tuesday 2nd January 10:57

[PaulKemp]

My thoughts on this are that for most applications that us amature drives will do, a good set of new OEM bushes is the best option.
If you are doing some serious track day work or starting out racing there may be some bushes that would benefit from a change to poly bush but just changing them all is not a scientific way to achieve better handling. Reaserching what works in what application first.
I picked up on a point in the first post about poly bush internal tube, this should be a few mm longer than the bush so when bolted up it does not move but the poly bush moves round it.
The OEM void bushes do indeed provide rotational damping and I would question replacing them with polly bushes unless you are compensating somewhere else in that suspension area.
Everything to do with suspension affects every part of it one way or the other, change one bit for the better and you’ll be looking at other areas very soon.

[SebringMan]

PaulKemp said:

My thoughts on this are that for most applications that us amature drives will do, a good set of new OEM bushes is the best option.
If you are doing some serious track day work or starting out racing there may be some bushes that would benefit from a change to poly bush but just changing them all is not a scientific way to achieve better handling. Reaserching what works in what application first.
I picked up on a point in the first post about poly bush internal tube, this should be a few mm longer than the bush so when bolted up it does not move but the poly bush moves round it.
The OEM void bushes do indeed provide rotational damping and I would question replacing them with polly bushes unless you are compensating somewhere else in that suspension area.
Everything to do with suspension affects every part of it one way or the other, change one bit for the better and you’ll be looking at other areas very soon.

On newer cars with dealers still about I agree you can do this.

Anything pre early 90s thought and it is hard. Try getting decent rubber bushes for any old Triumph ; new stuff is simply terrible, generally being softer than factory stuff and lasting around a year tops if you ever intend to use the car.

[Mr2Mike]

SebringMan said:

-MGB : I had rubber bushes as everyone knows as loves. The back of that car was so firm that it was terrible! I went with SuperFlex bushes there and even on Spax dampers and 8Jx15" Minilites it was one of the nicer MGBs I drove ; speed bumps weren't a chore ; I finally had a 'B with the rear suspension as pliant as the front. Of course the forums made out my setup was terrible and I ummed and ahhed for a long time.

So your PU bushes had more compliance than original equipment rubber bushes? That is extremely unusual to put it mildly, since the main claim for PU bushes is to remove unwanted movement.

[227bhp]

Mr2Mike said:

SebringMan said:

-MGB : I had rubber bushes as everyone knows as loves. The back of that car was so firm that it was terrible! I went with SuperFlex bushes there and even on Spax dampers and 8Jx15" Minilites it was one of the nicer MGBs I drove ; speed bumps weren't a chore ; I finally had a 'B with the rear suspension as pliant as the front. Of course the forums made out my setup was terrible and I ummed and ahhed for a long time.

So your PU bushes had more compliance than original equipment rubber bushes? That is extremely unusual to put it mildly, since the main claim for PU bushes is to remove unwanted movement.

Lateral movement, not vertical at the hub.

[GreenV8S]

Mr2Mike said:

So your PU bushes had more compliance than original equipment rubber bushes? That is extremely unusual to put it mildly, since the main claim for PU bushes is to remove unwanted movement.

There are different grades of rubber and PU so PU aftermarket bushes could easily be harder or softer than OEM. The PU bushes I've seen have actually been relatively soft.