Technical Diesel Bump Stop (Auxiliary Spring) Replacement

[Anthony489]

The elastomer "helper" cones on my motorhome were in a poor state after 18 years of service, and rear was more "bouncy" than it should be. I think the remains of the "bump stops" were about as much use as a piece of cold yorkshire pudding and looked rather similar !

I decided to replace with original style rather than anything more exotic like a semi-air setup. During replacement, I hit the common problem that the bolts were seized into the captive nuts in the chassis rail. Applying a fair amount of torque from a chain wrench to the upper metal cups simply resulted in breaking the feeble welds between the cups and the button heads of the bolts.

Fortunately, I found it possible to keep the old upper "cups", and simply lever out the old "rubber" which is held in place by a narrow formed ring. The new rubbers were removed from the replacements and swapped over to the new cups in-situ. They are quite a squeeze to get in, but it helped to have a combination of some silicone grease and a large jubilee clip to compress near the top. I then levered upwards with a crowbar which got it most of the way in, a prod with a large blunt screwdriver persuaded the last section to pop in.

This shortcut is unfortunately no help if you really do need to extract the upper cup in order to fit semi-air. To do that you would need to drill out the old bolts, and due to lack of room (the rear axle and leaf spring is directly in the way) a right angled drill attachment would be necessary

 

[bugsymike]

I suppose dropping the rear spring hanger moving bracket and jacking up high would give the clearance, but still a fiddle.

 

[Jockstrap]

There are two issues which relate one I had:

First the spring assist should only be hand tight. It's not a bump stop. Sumo replaced mine under lifetime warranty. I believe a fault bubble in the yellow bit was the cause.

Anyway as I have hydraulic levelling it's easier but the same problem: access. The photo shows the amount of clearance with the suspension hanging. 10 minute switch.

Problem welded nuts. My weld released the captive nut. I cut the bolt head and wiggling out the captive. Replacement nut was held with a spanner and replacement spring assist screwed in place. Near side released easily.

I had kept the Fiat originals and still using. 3 years on I think my early dissatisfaction with the original ride was more the original spec. Michelin campar tyres at 80psi . I switched to Fallen All Season at 60psi.

I'd agree with bugsymike and would suggest drilling out, and replacing with stainless rivnuts.
That will allow for oversize hole and ID for nut.