Technical Rear Subframe Modification Bushes(caps) - How do they work?

[yaztaz]

punto mk1 rear subframe bushes press into the subframe from above, so no easy way to replace, right? but apparently there are 'modification bushes' available that are like 'caps' and are fitted simply by taking the long mounting bolt out, putting the 'cap' over the underside of the old bush then putting the bolt back and re-tightening. this stabilises the worn-out bush by stopping the excessive (mainly vertical) movement, is that right? ok, if so, then does anyone know what the relationship is between the subframe and the cap which is held tight against the inner part of the old bush at the lowest point? what i mean is when tightened does the rim of the cup (1) come very close to, or (2) touch lightly against, or (3) push hard against the underside of the subframe? i am considering buying a set of four of these 'modification bushes' and need to find out exactly how they work, as i have another idea for them that i want to try out. any help much appreciated!

 

[dumbledore]

I believe is (3). If there is any vertical movement in the subframe do to worn out bush the additional bush will stop it. The bush is popular as people buy it in the hope they can get rid of the knocking noise coming from the rear which normally is actually caused by damaged radious arm bearing.

 

[yaztaz]

thanks v much for your wise words <>dumbledore<>. i want to be absolutely sure how they work so if anyone else kno about these cups id be v plsd to hear of your experiences. if the rim of the cup tightens against the subframe then this will mean the subframe becomes solid with the body of the car, does it not? if thats what happens after the four cups are fitted then what effect does that have on handling or noise transfer? these cups are said to be a fiat approved mod though arent they? <>dumbledore<> in the cases of rear-end-knock due to subframe and not trailing arm, can you (or ne1 else) describe what happens to the old bushes? does the centre (alloy?) part become detached from the surrounding rubber and therefore its this that enables the up-down movement? i kno this happens with multipla rear subframe front bushes but thats a heavier vehicle so maybe a different sit. good to see this is a busy forum, punto mk1, hope this thread can be busied-up

 

[dumbledore]

I would say if the bush perishes then the sub frame will start getting nearer the body. The bolt will then not be able to clump the sub frame to body properly. When you go over a bump the sub frame will try to move away from the body causing a knock. If you use the cup that will stop this move. However a badly perished bush will alter the geometry and hence using a cup the end result will not be perfect.

 

[flisko]

this

boom

it goes over the old bush, remove 1 bolt and put the bush over the old one and tight the bolt back, same on other side, u dont even need to lift up the car