Rear lower links

[Steve_Lindford]

Someone has offered to add grease nipples to each end of my rear lower links as I happen to have them off the car. Can anyone confirm that the inner metal part of the bush remains fixed in position by the bolt - and the rubber part moves around it - fixed to the cylinder part of the end of the link?? - Nothing like the front suspension where the rubber flexes as part of the suspension...

Steve

[RoddyMac]

The bushing should be bonded to the inner steel sleeve, and a press fit into the link.  All the deflection should be in the rubber, it shouldn't rotate about the sleeve or the link.  There should be enough of an interference fit between the rubber portion of the bushing and the link to keep the bushing from rotating. 

As for a grease nipple, no need, rubber doesn't really like petroleum based grease.  If the bushing is poly, then you can use the lube that comes with the bushing, but even in that situation, the grease nipple isnt needed as the poly bush is stationary in the link and rotates about the inner crush tube. 

[jbcollier]

Lower links from the tranny to the rear upright use suspension bushings from the MGB's front suspension.  They are bonded to an inner steel bush.  Do not lubricate with chassis grease.

[Steve_Lindford]

Well the rubber on  mine cant be bonded to the inner sleeve as they have a 'top hat' profile - so you would never get them in!

[RoddyMac]

That bushing looks like a poly bush. The crush sleeve isn't bonded to anything, it pivots in the poly top hat.  But again, there isn't any reason to install a grease nipple as the outside of the bushing should be firmly held by the link.

[EuropaTC]

It does look like a poly bush, but the S2 used 2-part bushes which you fitted from both sides so they could easily have a shoulder on them as in Steve's photo. I've never used that type myself but I'd noticed the difference in the S2 & TC parts manuals. It wouldn't surprise me to find they are interchangeable between S2 & TC ?

Brian

[Steve_Lindford]

What is the definition of a polybush?? I dont have any of the components with me at the moment as I am having the lower links straightened - but they are pushed in from each side and they dont touch in the middle. I am told they compress if you push a finger nail in - so certainly is not made of nylon. What is the logic of not lubricating 2 moving parts that rub together??

Steve

[EuropaTC]

What is the definition of a polybush?? I dont have any of the components with me at the moment as I am having the lower links straightened - but they are pushed in from each side and they dont touch in the middle. I am told they compress if you push a finger nail in - so certainly is not made of nylon. What is the logic of not lubricating 2 moving parts that rub together??
Steve

I'm not sure I've seen a definitive statement on what a polybush should be, but we're generally referring to polyurethane bushes with non-bonded stainless inserts which are fractionally longer than the polyurethane so that when the assembly is tightened up it locks the stainless insert into your wishbones and leaves the polyurethane free to rotate with suspension movement. When you assemble them you use a light grease on the inside and the ones I have are machined in the bore so they'll retain some grease once assembled.

It's a contrast to the normal bushes where the steel insert is bonded to the rubber and it's the twisting of the rubber which accommodates the suspension movement, but one plus point for the polybush is that you no longer need to load the suspension before tightening the wishbone bolts/nuts.  I have polybushes on my car and if I'm honest I'm not sure what they bring to the party; maybe it's noticeable on track but I can't honestly say it's given me the ability to out-corner Lewis Hamilton on the roads around here.

Second part, if your bushes come as 2 halves that go in from either side I think you have the correct part for the S2 cars, or at least it looks like that from the parts manual. The bushes on my TC are one part components which push in from one side only and are in fact the same dimensions as those used on the front wishbones. AFAIK they (both types) were designed to be used without lubrication.

Brian

[jbcollier]

Petroleum based lubricants dissolve rubber.

[BDA]

I have polybushes on my car and if I'm honest I'm not sure what they bring to the party; maybe it's noticeable on track but I can't honestly say it's given me the ability to out-corner Lewis Hamilton on the roads around here.

 I can see a few advantages that really only apply to the front suspension. First, with poly bushes, you don't have to torque the front suspension at ride height. Second the stock rubber bushes sometimes, for lack of a better term, "delaminate" (see attached picture). Third, poly bushes don't have to be pressed into the A-arm like the stock bushes. If/when my stock bushes go out, I'll replace them with poly bushes.

[Steve_Lindford]

I hadnt thought about issues with lubricants dissolving rubber.

It seems like my bushes (on TC) are from a S2 - from what is being said. If they were one piece either the bracket on the gearbox would have to be smaller - or the end of the link would have to be bigger to stop the link sliding forward and back.

Anyway they seem to work ok - I will have to be careful when  I replace them so I get the correct part.