Rubber or Polyurethane?

[WoodleySaint]

Hi,

The Sprint I'm restoring has been garaged for 40 years and all the bushes need replacing. Looking at Rimmer's the polyurethane kit is £348, and £192 for the rubber equivalent.

1) Should I use polyurethane or rubber?
2) Are there any specialist tools that are required to do the replacing?
3) I'm not too keen on the coloured poly bushes. If the recommendation is poly is there another supplier of black ones?

Thanks as always.

Cheers Mark

[Carledo]

A question with at least 500 different answers!

I use a mixture of both types, But even my most track focused cars aren't fully polybushed. The front of front tie bars, rear of rear upper tie bars and bulkhead column bush are the poly versions I consider essential. For a normal roadgoing car, this is sufficient and everything else can and probably should be replaced with quieter and more compliant rubber.

That Rimmers price is exorbitant and anyhow Chris Witor's Superflex bushing is far superior and you can buy as much or as little as you want. And I think Fitchets have all the rubber versions (they don't sell Poly - At all) Whilst the Superflex bushing IS coloured, rather than black, it is a least a fairly dignified and unobtrusive dark Blue.

HTH, Steve

One more thing, consider solid rack mounts (at least one, if not both) they sharpen up the steering no end!

[WoodleySaint]

Thanks Steve, it certainly does help. I hadn't even thought about selective use of poly bushes.

[Carledo]

Poly will stiffen up the suspension and that will, if used judiciously, sharpen up the handling. Especially if used with other mods like shorter stiffer springs and variable rate dampers. But too profligate use will turn the Dolomite into an uncomfortable, noisy, vibrating beast.

There are a couple of places I WON'T use poly EVER. I won't poly fit both ends of the rear trailing arms (usually just the axle end) Poly at both ends doesn't allow the arm to flex as it should and can weaken the trailing arm to the point of cracking and ultimate failure. And the "rose joint" inner track control arm bush fitted to all Dolomites except early Toledos and 1500FWD models, is almost indestructible, the normal replacement poly bush (which isn't a "rose joint" type) is actually weaker. If it ain't broke, don't fix it!

There are no special tools required to fit any of the Dolomite's suspension bushes, but you will find a good bench vise useful, along with a selection of bush sized sockets and a bucket of washing up liquid to ease their passage in.

Finally, not suspension, but important. If all you do with the Sprint is car shows on sunny Sundays, and pottering locally, the brakes are probably adequate (if maintained in top condition) If, however, you wish to exploit the Sprint's performance potential on any sort of regular basis, may I point you in the direction of the "Trackerjack" vented front disc conversion. It's the brakes the car SHOULD have had from the start and turns hard stops from nerve racking to "no worries".

Steve

[cliftyhanger]

I would be wary of rubber stuff unless OEM. I fitted a few rubber bushes from a "recommended" supplier, they failed in under 2 years.
Many of the poly bushes are the same shore rating as OE rubber, so should not make things harsher.
Also, check the old bushes carefully before buying new stuff, some are probably still absolutely fine.

Chris witor now sells his own bushes, superflex as opposed to the original super pro. (I think that is teh right way round!) I think I would choose the originals....

A few years ago I managed to find some TR7 OEM void bushes from the training arms which were a perfect fit, very happy with those. May still be available.

[yorkshire_spam]

My 2pm worth... in an ideal world OE spec rubber would be the way to go, but in my experience across multiple models/marques the modern rubber is junk, plan on replacing every 12 to 24 months, less if they get contaminated with oil.
The poly world is full of sharks and chancers. To be honest the only ones I trust are SuperFlex (Triumphs) or SuperPro (Land Rovers)
They cost a fortune, but as a "fit and forget" replacement to me they are worth it.

[xvivalve]

The other place I would avoid poly bushing is the axle end of the rear radius rods; I've seen too many polybushed cars compromising the threaded ends of the radius rods due to insufficient flexing causing the threaded ends to bend and in worst case scenarios shear the threaded end completely.

[cliftyhanger]

The other place I would avoid poly bushing is the axle end of the rear radius rods; I've seen too many polybushed cars compromising the threaded ends of the radius rods due to insufficient flexing causing the threaded ends to bend and in worst case scenarios shear the threaded end completely.

It was those bushes that failed on my car very quickly. I initially dismissed them as the cause of the odd handling because they were so new. Lesson learnt
If the std shore polybush are used it should not cause extra strain. Another case of "uprated not being better!"

[Carledo]

The other place I would avoid poly bushing is the axle end of the rear radius rods; I've seen too many polybushed cars compromising the threaded ends of the radius rods due to insufficient flexing causing the threaded ends to bend and in worst case scenarios shear the threaded end completely.

It was those bushes that failed on my car very quickly. I initially dismissed them as the cause of the odd handling because they were so new. Lesson learnt
If the std shore polybush are used it should not cause extra strain. Another case of "uprated not being better!"

This is just weird! I went mad on the Carledo and polybushed BOTH ends of this upper rod and used Chris' race spec red bushes at the axle end. WHY? Because doing line lock burnouts on the dragstrip caused massive axle tramp until I did it! The combo turned a faint axle whine into a howl at certain road speeds (another good reason not to poly both ends) but I had no other ill effects. The arms are still the ones that came with the car and still behaving perfectly despite many burnouts and trackdays plus 60odd thousand miles of "enthusiastic" road use and have now been transplanted into another bodyshell and still giving good service (though I've deleted the line lock from this car)

Not saying it can't happen, it obviously can or you wouldn't mention it! But if it was gonna happen to anyone, I would've thought it would be ME! I've certainly given it every chance and encouragement I can!

Perhaps the arms that failed were already compromised, I've rejected a few for refitting over the years that have been reduced to half their original thickness from corrosion. Same with trailing arms, sure a few people have snapped them on full polybushed race cars, but not long ago I found a cracked, ALMOST snapped one on a rubber bushed 1500 AUTO! You can't GET an easier life than that and yet it broke. And the one on the other side wasn't much better.

We have to accept that a lot of these pressed steel parts are well past their sell by dates and examine them thoroughly before pressing them back into service.

Steve