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Rear bump stops


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Can anyone tell me if there are 2 standards of rear bump stops for a 4A? (the large bracket under the wheel arch). The ones from my 67 4A that I'm rebuilding have a hexagonal 35mm spacer between the bracket and the rubber, that screws into a captive nut on the inside of the bracket. The rubber is also about 35mm. These need replacement/repair and I've found some replacements, but although the bracket itself is the same overall dimension, it doesn't have the spacer, just a longer rubber. On the replacements, the bottom tip of the rubber is positioned about 30/40mm higher than my originals, so the trailing arm will travel further before hitting the bump stop. Not sure if the replacements are from a 4A, 5 or 6.

 

This is probably difficult to visualise from my description and I'll try to post some pics later.

 

Jeff

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Sounds like you may have TR5/6 ones which screw onto a plinth on top of the trailing arms. They are wrong for your application so send them back and get the correct ones. You need part number 140290.

Stuart.

Edited by stuart
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Bit difficult to see from the picture but I would say that neither is correct, I think you should have something like this.

Stuart.

Rearaxle004-Copy_zps5fa8e76f.jpg

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Hopefully this pic is a bit easier to see what the differences are.



Roger - Have you had any problems with the shorter stop? There seems to be about 1.5 inch difference between the position of the rubber on my old one than the replacements.



I think what I'm going to have to do is rebuild the bracket and then attach a new rubber to it - but is the rubber stop position critical?



Jeff




post-11991-0-23620600-1409596283_thumb.jpg

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What you would need to do to check criticality is remove the road spring and push the trailing arm up until it contacts the rubber stop. If the shock absorber bottoms out first before the trailing arm hits the rubber then it is possible to snap the rear section of the trailing arm.

Stuart.

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Its possible that the factory decided on the change as the circular base doesnt spread the load that well as I have seen some where the stop has been punched up into the box. The squarer base would spread the load better. The factory changed the spring rate when they went to the later style of bump stop on the TR5 as well.

Stuart.

Edited by stuart
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Thanks for the info and advice, it seems there is a variety of standards on these cars!!

 

I haven't yet decided what rear suspension set up I will be using. It will either be lever arms or the Revington telescopic set up. Once I've bottomed that out :lol: and have the dampers fitted I'll do Stuarts test before I weld refurbished brackets and bump stop in place at the appropriate height.

 

Jeff

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when you end up with this you're probably better off having an hexagonal spacer to work with. Possible why they changed it. Mine is 66 reg w com# 65808

 

 

The square shaped one is just as susceptible to the bump rubber breaking off as its the usual steel to ally reaction problem.

Stuart.

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The square shaped one is just as susceptible to the bump rubber breaking off as its the usual steel to ally reaction problem.

Stuart.

 

I mean it's probably easier to remove the bump stop assembled with the hexagonal spacer which you can handily undo with a spanner unlike the circular one.

Edited by Geko
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