Poly or original
Discussion
Big suspension refurb planned for winter but I need to get a couple of things straight in my head.
Originals: I assume the original bushes comprise two steel tubes bonded together with a rubber core. The outer sleeve is a press fit in the wishbone and the inner sleeve is bolted tight to the chassis. Thus, the tortional twist of the rubber allows the wishbone to move.
If the rubber can twist it can also compress, thus absorbing vibration (good) but also allowing the wishbone to 'float' a little and deteriorate over time (bad).
Polys: I assume polybushes are essentially plain bearings, fixed in the wishbone and free to rotate on the chassis bolt. Provided the bolt and bore are a good fit the wishbones will be accurately supported but free to rotate smoothly (good). However, they will not absorb vibration and, like any plain bearing, will eventually wear the bore oval (bad). I assume once the wear starts it will accellerate quickly.
So, if I'm looking for a slightly smoother, slightly less precise ride with a long life, replace the originals. Or, if I'm looking for a slightly harsher, slightly more precise ride, possibly with the need to replace the bearings more often, go poly.
Can anyone tell me if I'm talking c**p or not?
Originals: I assume the original bushes comprise two steel tubes bonded together with a rubber core. The outer sleeve is a press fit in the wishbone and the inner sleeve is bolted tight to the chassis. Thus, the tortional twist of the rubber allows the wishbone to move.
If the rubber can twist it can also compress, thus absorbing vibration (good) but also allowing the wishbone to 'float' a little and deteriorate over time (bad).
Polys: I assume polybushes are essentially plain bearings, fixed in the wishbone and free to rotate on the chassis bolt. Provided the bolt and bore are a good fit the wishbones will be accurately supported but free to rotate smoothly (good). However, they will not absorb vibration and, like any plain bearing, will eventually wear the bore oval (bad). I assume once the wear starts it will accellerate quickly.
So, if I'm looking for a slightly smoother, slightly less precise ride with a long life, replace the originals. Or, if I'm looking for a slightly harsher, slightly more precise ride, possibly with the need to replace the bearings more often, go poly.
Can anyone tell me if I'm talking c**p or not?
Jon
Just fitted poly to my front.
They don't turn on the bolt, they have a steel sleeve that the bolt goes through and clamps up just like the originals. So the sleeve turns in the bush.
I can't say I can feel any more vibration, as the whole front end behaves much better with pin sharp precision than it did on the old bushes. I RECOMMEND YOU TRY THEM!
They come with lubricant - looks like copper slip to me - and polyurethane is a very tough and resilient material so I would expect them to last as long as the rubber originals at least.
The Land rover lads have been fitting these for a long time, and when I had my Range Rover I never read in any of the magazines/web sites that they wear out quickly.
One of the reasons I never had a second thought in fitting them to my Cerbera.
Going to do the rear end over the winter if not before, as I found it a very easy job to do the fronts to be honest.
Steve
Just fitted poly to my front.
They don't turn on the bolt, they have a steel sleeve that the bolt goes through and clamps up just like the originals. So the sleeve turns in the bush.
I can't say I can feel any more vibration, as the whole front end behaves much better with pin sharp precision than it did on the old bushes. I RECOMMEND YOU TRY THEM!
They come with lubricant - looks like copper slip to me - and polyurethane is a very tough and resilient material so I would expect them to last as long as the rubber originals at least.
The Land rover lads have been fitting these for a long time, and when I had my Range Rover I never read in any of the magazines/web sites that they wear out quickly.
One of the reasons I never had a second thought in fitting them to my Cerbera.
Going to do the rear end over the winter if not before, as I found it a very easy job to do the fronts to be honest.
Steve
jonbarrett said:
Tim
What aspects of the handling did the Polys transform and have you found any drawbacks? I use my car mainly on the road with three of four track days per year.
I may not be the best person to ask as mine is 99% track use these days, but it's tightened everything up, it now goes where I point it and they seem to have removed some of a 'vagueness' that 10 year old metalastic bushes by nature have. I personally have yet to find a dissadvantage, but I may change my tune, if I need to replace them in a few years time, as a full car kit isn't cheap!What aspects of the handling did the Polys transform and have you found any drawbacks? I use my car mainly on the road with three of four track days per year.
But, having said all that you need someone who uses the car more on the road than I do, mine is almost undriveable on most roads as it's so bl**dy hard, due to the shock and spring setup.
I would say have a go in mine, but I think you'd hate it.
Tim
Steve
Posted my question to Tim before I saw your detailed reply. So, two immediate votes for polys.
I get the idea of the inner sleeve, allowing a much more accurate assembly.
How are they held in the wishbone? Friction, adhesive, lock screw?
I'll also be replacing the shocks and ARB droplinks. I've heard good reports re Nitrons but am unsure about the droplinks. There seem to be mixed feelings regards the originals.
Posted my question to Tim before I saw your detailed reply. So, two immediate votes for polys.
I get the idea of the inner sleeve, allowing a much more accurate assembly.
How are they held in the wishbone? Friction, adhesive, lock screw?
I'll also be replacing the shocks and ARB droplinks. I've heard good reports re Nitrons but am unsure about the droplinks. There seem to be mixed feelings regards the originals.
They're just held in with friction and the fact that they're 'squeezed' between other components, if that makes sense.
Here's a pic of the bits of the 'main' bush that is used on most of the suspension:
And, here's the Powerflex page relating to the Cerbera.
As for the drop links, I assume you mean the 'upgraded' ones, there are mixed opinions, mine are okay, but I only have them on the front, complaints that I've heard have been due to the failure of the rod ends, mine seem okay, so far but I don't do many miles. I also only have a front ARB so the rear drop links have never been fitted.
As for Nitrons, I have them and they work well, Nitron I believe also build the 'budget' monoshock under the Racing Red banner, again, there's been some teething troubles, but the common consensus seems to be that these have been ironed out. Another plus in Nitrons favour, is that you can have them rebuilt and re-valved to suit your application, so in effect for around £60 a corner you can, in effect, have a new shock should you ever wear them out.
There are plenty of people on her Jon, who have Nitrons fitted and Polybushes, and also use their cars in a similar way to you, so hold fire and wait for some more comments, before parting with £1.4K!
Good luck
Tim
Here's a pic of the bits of the 'main' bush that is used on most of the suspension:
And, here's the Powerflex page relating to the Cerbera.
As for the drop links, I assume you mean the 'upgraded' ones, there are mixed opinions, mine are okay, but I only have them on the front, complaints that I've heard have been due to the failure of the rod ends, mine seem okay, so far but I don't do many miles. I also only have a front ARB so the rear drop links have never been fitted.
As for Nitrons, I have them and they work well, Nitron I believe also build the 'budget' monoshock under the Racing Red banner, again, there's been some teething troubles, but the common consensus seems to be that these have been ironed out. Another plus in Nitrons favour, is that you can have them rebuilt and re-valved to suit your application, so in effect for around £60 a corner you can, in effect, have a new shock should you ever wear them out.
There are plenty of people on her Jon, who have Nitrons fitted and Polybushes, and also use their cars in a similar way to you, so hold fire and wait for some more comments, before parting with £1.4K!
Good luck
Tim
Edited by TT Tim on Saturday 22 August 19:44
jonbarrett said:
Steve
Posted my question to Tim before I saw your detailed reply. So, two immediate votes for polys.
I get the idea of the inner sleeve, allowing a much more accurate assembly.
How are they held in the wishbone? Friction, adhesive, lock screw?
I'll also be replacing the shocks and ARB droplinks. I've heard good reports re Nitrons but am unsure about the droplinks. There seem to be mixed feelings regards the originals.
Initially they just push into the wishbones (once you get all the powder coating out!) and are a very precise fit.Posted my question to Tim before I saw your detailed reply. So, two immediate votes for polys.
I get the idea of the inner sleeve, allowing a much more accurate assembly.
How are they held in the wishbone? Friction, adhesive, lock screw?
I'll also be replacing the shocks and ARB droplinks. I've heard good reports re Nitrons but am unsure about the droplinks. There seem to be mixed feelings regards the originals.
I bolted up and then removed one wishbone and then found it much more difficult to move the polybush, in fact I could not move it by hand, so they seem to set themselves.
But once bolted up, the wishbones move up and down without any "stick-tion".
I did have one problem, which could be because my car is an early GT?
The workshop manual, shows the upper rear mounting plate as being flat, but mine has a stiffening lip on the outer edge.
This means the leading side of upper rear bush has to tuck behind this lip and is packed out with washers on mine. Not sure if this was a TVR factory bodge, or the bushes have replaced and bodged in the past.
The TVR shop shows a thicker spacer that I suspect should be fitted on mine instead of the washers, but are not!
http://www.racetechdirect.co.uk/search-subsection-...
I also had to modify the kit a bit for this upper rear, by drilling out the extra "special" washer they supply. I had to drill the hole out a bit to allow it to fit over the shorter spacers I have.
However this uprated bush kit seems to be much more robust than the original, as this "extra" washer and its poly disc stops any fore-aft movement at this point.
For my particular set up, it would have been much better to fit a different sleeve with a smaller (to match the bolt diameter) inner diameter. I could then just have left out these little spacer ferrules which seem to be an afterthought to make a standard bush fit the bolt!! VERY TVR???
So check to see if you have this lip or just a flat plate where the upper rear fits to the shock mount.
Steve
The poly bushes on the inboard end of the lower front drag struts only lasted 3 months 
Theory is that the powder coating being missing from the inside of the arms meant that the bush was too loose in the arm. Excess movement then lunched the flange on the rear of the bush.
I have new bushes on now having coated the inside of the drag struts to improve the fit. The new ones havn't really been on long enough to tell if the problem is going to recurr, but be warned that it might be worth checking the coating on the inside of the bores where the bushes fit.
Theory is that the powder coating being missing from the inside of the arms meant that the bush was too loose in the arm. Excess movement then lunched the flange on the rear of the bush.
I have new bushes on now having coated the inside of the drag struts to improve the fit. The new ones havn't really been on long enough to tell if the problem is going to recurr, but be warned that it might be worth checking the coating on the inside of the bores where the bushes fit.
That's interesting, as I only had what I would call a "splatter" of powder coating on the inners of all my fronts. Which I eased out with wet&dry.
Have to wait and see how they stand up to wear and tear.
RE Nitron.
I believe that they have separate adjustemnt for compression and rebound damping.
Which should allow a more supple set up for the road.
I always found on sports bikes a good rebound, stiffer than compression gave better handling.
I have Gaz Golds fitted and they seem prettty good, but one click makes a big difference. I also find they need to warm up before they settle down, so I adjusted them after a good run and have a nice balance between too bouncy and too hard now. So I know that 1 click should be put on when I finally get a track day sorted.
One problem I found while doing the bushes at the front, was that when on the axel stands, the top of the Gaz shock touches the mounting bracket (MY STRANGE EARLY GT WITH THE BRACKET) so I had to just tweak them to get the bottom bolt in. Not a lot, but it's there.
On the road this wont be a problem unless I take off!
Have to wait and see how they stand up to wear and tear.
RE Nitron.
I believe that they have separate adjustemnt for compression and rebound damping.
Which should allow a more supple set up for the road.
I always found on sports bikes a good rebound, stiffer than compression gave better handling.
I have Gaz Golds fitted and they seem prettty good, but one click makes a big difference. I also find they need to warm up before they settle down, so I adjusted them after a good run and have a nice balance between too bouncy and too hard now. So I know that 1 click should be put on when I finally get a track day sorted.
One problem I found while doing the bushes at the front, was that when on the axel stands, the top of the Gaz shock touches the mounting bracket (MY STRANGE EARLY GT WITH THE BRACKET) so I had to just tweak them to get the bottom bolt in. Not a lot, but it's there.
On the road this wont be a problem unless I take off!
A couple of points here:
Powerflex say that the bushes were made to fit the standard TVR wishbones that are powder coated on the inside. The obvious deduction is that this should not be removed. They also do special versions for certain positions to improve the life.
As for spacers... there are some variations around including some cars that have Tuscan style bushes! It is also not uncommon for the spacers to be lost on a complete strip down.
As a result I have made custom spacers up for my powerflex customers who have encountered strange cars as part of the after sales service. It has been the exception rather than the rule though.
Powerflex say that the bushes were made to fit the standard TVR wishbones that are powder coated on the inside. The obvious deduction is that this should not be removed. They also do special versions for certain positions to improve the life.
As for spacers... there are some variations around including some cars that have Tuscan style bushes! It is also not uncommon for the spacers to be lost on a complete strip down.
As a result I have made custom spacers up for my powerflex customers who have encountered strange cars as part of the after sales service. It has been the exception rather than the rule though.
TT Tim said:
As for the drop links, I assume you mean the 'upgraded' ones, there are mixed opinions, mine are okay, but I only have them on the front, complaints that I've heard have been due to the failure of the rod ends, mine seem okay, so far but I don't do many miles. I also only have a front ARB so the rear drop links have never been fitted.
Just to clarify things: Edited by TT Tim on Saturday 22 August 19:44
The rose jointed drop links are far better and will improve the handling dramatically as the ARB is working as it should be.
Some people have had problems but they are usually with Griff and Chimaera rear setup where TVR tolerances are all over the place and the fitting can be very critical.
In all the cases that I looked at... the fitting wasn't right and the rose joint locked out and broke.
I can't remember having any customer come back to me with a broken rose joint on a Cerbera set up.
PS Johnny W has been using them on his Race Cerbie for a couple of years.
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