[kingspoons]

Hi all,

It's MOT season again so I've been doing a few pre-test checks, only to find that the rear bush in the trailing arm - which I'd only replaced in 2022, has somehow already become debonded, with a large gap beneath it when the car is jacked up. The originals lasted nigh on 30 years, the replacements (aftermarket, so not even likely to be old rubber) didn't even get to two!!

Am I right in thinking this will be an MOT fail? If so, is there a way to "re-bond" it? Or if not, does anyone know of any quality replacements, so this doesn't end up becoming a very big job every two years!

Picture of the offending bush attached!

[g259fsg]

I had the same problem. The original Rover parts lasted about 18 years and then failed the MOT. The garage put in new ones (aftermarket parts). After three years got advisories that they had deteriorated like yours. You may get a failure or more likely an advisory, depends on the tester, but you'll want to replace them.

When I took off the aftermarket parts they seemed pretty flimsy and a bit rubbish. The garage said they are mostly like that and they regularly replaced them. I went for polyurethane replacements, that was a few years ago, and I've not had to replace them. They do make the ride a bit harder. I wrote a Viking article about this which is available through the Technical Archive. It's in the Spring 2011 edition pages 14 to 17, a long time ago, so the bushes have lasted now over 13 years. Quentin Howell also wrote a piece about these bushes in the April-June 2019 p19-21. See what you think.

Hugh

[itcaptainslow]

Genuine MGR trailing arm bushes are long NLA, unfortunately. As you’ve seen, the quality of aftermarket replacement parts is variable.

Don’t try and rebond it - that bush needs replacing, unfortunately.

The Powerflex alternatives sound interesting. If you try these, please let us all know how you get on.

[kingspoons]

Hi both, many thanks for the replies!

I'd been digging through past issues of the Viking and had come across the polyurethane bushes being available. I like the sound of the lifetime warranty they offer, but the only thing putting me off - aside from the fact it may make the ride a bit harder (although I had heard rumblings that other manufacturers offer a variety of softness choices) - was the added complexity of fitting them.

From what it sounds like, you re-use all the metal bits from the original bushes, but fit the polyurethane in place of the rubber. In that case, unless I'm misunderstanding the fitting process, will the polyurethane bush not actually be bonded to the metal that runs through the centre (or the metal that surrounds it)?

[g259fsg]

I'm fairly certain I removed the complete old bush assembly including the metal shell round the rubber part. The new poly bush fitted directly into the housing of the trailing arm (see the photos in my article). It's a very tight fitted so I doubt it would move after installation. The shaft which goes through the centre of the bush is not bonded but again is a tight fit. I think in the last 10+ years it has worked slightly loose, however, so far the MOT guy hasn't commented on it. I can see it could be a failure point eventually as the shaft could be weakened by corrosion and friction. Unless it is very loose, it shouldn't make much difference to the handling, however when tight it would present a very slight additional resistance to the suspension movement. Given the size I would think it insignificant compared to the strength of the coil spring and damper.

Hugh

[crepello]

My replacements parted like that pic after quite a short time in service, with the car jacked up.
I noted the suspension does adopt a pretty extreme degree of camber when drooping without any load.

But if that's considered a MOT fail condition, I couldn't understand why polybushes with an unbonded
centre beam should be acceptable. What do those look like when similarly jacked up?

Incidentally, there is very little information in the manuals about the correct assembly alignment of the
bushes in the trailing arms. Replacement isn't even considered in my copy of the Rover WSM, bought in
1991.

[g259fsg]

Good point about the geometry. You need the shaft with the two bolt holes to be set at the right position relative to the chassis fixings, otherwise there would be some sideways force built in when you bolt it up. I measured the bolt hole position relative to the trailing arm before taking out the old bush. The back end of the arm bolts to the rear hub, but the front end anchors through another link to the body. This should be bolted back in the same position to maintain the rear tracking.

Hugh

[GTiJohn]

These bushes need to be bonded as they do take some side load, as well as vertical and fore-aft.

The basic geometry is basically that of the Porsche "Weissach" axle, with this bush inserted to avoid design infringement

See - https://www.youtube.com/watch?v=BFtVV5V-ZMw

So you see that stopping this point, sliding out of position is rather important and why making it a solid bush harms the ride.

As all R8's will need good quality replacements sooner or later, this is a part that we could consider re-manufacture.

[rjessett]

The bushes were not on the early EPC's and Workshop manuals as replacment was not a service replacement, so you had to buy the whole arm(!). MK4 Mondeos have a similar bush, and similar situation in the early days.

However, bushes are easily obtainable, both pattern and (Genuine) Xpart - RGX100980

An ex-Rover trained mechanic friend of mine's record of changing both of these is 12 minutes on a ramp! back in the day, very common thing to replace.

[itcaptainslow]

The “genuine” XPart bushes aren’t of the same quality as the original MGR ones unfortunately.

Great effort on changing them - they’re usually a pig to get in and out!