Poly subframe mounts

[Andrew S]

Just out of interest, the rubber subframe mounts have a vulcanised centre tube, how does this work on the poly ones? Can they vulcanise them or are they glued?

[jleyton]

Hi Andrew,

I've no personal experience of this, however if you look on Chris Witor's site (http://www.superflex.co.uk/technical.php) you'll see that he refers to 'crush tubes'.

My understanding is that, as you torque up the fitting, the crush tube errr..... crushes and in so doing it then grips the polybush. Does that make sense ?

Cheers

Julian

[Andrew S]

Thanks Julian. I guessed that's what it would be but having previous rubber ones fail as they bottom out as the tube separates from the inner tube, I would have thought that a rubber one was better as it can be vulcanised whereas the crushed tube and the flexibility of poly maybe would be as strong. What stops the poly sliding down the tube and bottoming out?

[jleyton]

Hi Andrew,

I would have thought that the crushing action makes the tube corrugated so that the poly cannot then slide on it but I really don't know for sure.

Why not give Chris Witor a call tomorrow - you hear lots of very positive comments about him (although ISTR he asks for telephone calls only at a certain time of the day).

Cheers

Julian

[Andrew S]

Thanks Julian

[V Mad]

Vulcanisation is not a gluing process, its a chemical treatment of rubber to make it more durable. The rubber will presumably be 'cast' around the bush just like the poly rubber so in either case they should stick to the bush? But which has a stronger bond remains to be seen.

[Andrew S]

Cheers Chris

[Andrew S]

Have looked at the mounts today and can see that they differ in height. The nearside appears to have a narrower gap, so presumed it has dropped slightly compared to the drivers side (The photo with the red trolley jack in the back ground).

Being that I have trying to improve the drive train alignment to get rid of drone / vibration under acceleration, could this be it? The sub frame mount has not dropped enough to cause a knock.

The reason why I ask is that if I leave the car on axle stands on the subframe arms for a long while, the vibration goes almost for around 10 miles or so afterwards and then starts to come back so presuming the mounts settle or sink

Any comments appreciated. My doubt is that its not enough to cause the problem but if I have the 3mm and the 6mm washers above, then surely these make a difference so this could be an area where you need to align

Thanks
Andrew

2015-04-05 13.17.17.jpg 2015-04-05 13.18.25.jpg

[Ian Durrant]

I have heard that if those mounts collapse you get drivetrain vibration. I had it on mine when I last drove and both mounts have collapsed so they will be getting done before it goes back on the road. if it is that it is at least a simple fix.

[Andrew S]

Thanks Ian
It used to be the case that rubber broke away from the inner tube but now with the quality of rubber, I think its just that, the rubber sags or softens rather than breaks away. May go down the route of poly's

[new to this]

Andrew

youve had a lot of problems with this vibration,if you change the subframe bushes,it may be a good idea to check the holes in the end of subframe arms,where it meets the diff,in case they have elongated,

dave

[Andrew S]

Thanks Dave, good point but I have even gone to the lengths of replacing the arms and even the holes being welded up even though they were not elongated.

[new to this]

Thanks Dave, good point but I have even gone to the lengths of replacing the arms and even the holes being welded up even though they were not elongated.

andrew

i did the same thing,welded tube in the holes then redrilled

dave

[Andrew S]