Rear Suspension

[Guest elwe]

I got my 2B/4 through the SVA two weeks ago and I have been finding that the rear suspension is grounding a little too easily.

 

I have the old sierra rear suspension with the front struts modified as top spring mounts. I have set the ride height as high as possible. The ride height isn't bad, without a passenger its been fine. However with a passenger or a boot full of stuff (or worse, both) I find that the rear end will sometimes ground out going over small bumps.

 

I have also found that the rear end will hit the ground when doing a standing start. OK, I have the high torque, low compression 2 litre engine but it still should ground should it?

 

Does anyone have any suggestions? I don't really want to change to coi overs (though I will with my second kit). I have thought of getting some slightly longer stiffer springs. Does this sound like a good idea? Or do the dampers really need changing as well?

[Guest Guy]

Hi Elwe,

 

Firstly congratulations on passing the SVA

 

My Sub-K had the same rear suspension setup as yours and was fine, are you sure you've not got the Sierra front springs in there instead of the rear ones? The front ones are thinner metal and are slightly tapered, they are also as soft as rice pudding so the back end of the car will sag under load.

 

If you're sure you've got the rear springs fitted then I'd look at the dampers.

 

I had to cut the spring cup off the strutt an weld it onto the bottom of the shaft to get some extra length.

[Guest TerryBarry]

Yes, well done with the SVA

Have you though of trying those spring assisters sold to prevent the rear suspension bottoming out when towing

Shown HERE, also I'm sure there are some spherical shaped ones which go inside the spring

[Guest elwe]

I definatly have they rear springs in there.

 

I had thought of spring assisters usually used for towing but for some reason I don't like the concept.

 

The rear suspension does seem soft compared to the front.

 

Could I use a second set of 2" springs inside the Sierra ones? The rate and length would need to be chosen carefully.

[Guest TerryBarry]

It seems odd that the rear suspension is soft since it was originally designed to support three people in the rear seat and a boot full of luggage in the Sierra.

The pivot points and spring location in the trailing arm are the same as the Sierra.

My donor had a tapered central bump stop at the top of the spring - have you carried these over to the 2B/4

[Guest elwe]

No, I don't have a bump stop. But the torque tube mounts are hitting the road before the suspension bottoms out anyway.

[Guest old_timbo]

I had exactly the same problem with a 2B that I bought, including grounding under hard acceleration. I was concerned about hard grounding causing rear end slides and the rapid rate that the bolt heads for the rear subframe were dissappearing. I increased the ground clearance by making large flat washers instead of the cups scavenged from the front suspension. This gained about 20mm. Still had a problem with two people and very bumpy roads at speed. So then I fitted the rubber spring assisters from Grayston Engineering (type GE15). This transformed things. So I've still got the same ride height (5 1/2" inches, so less than recommended), progressive rate suspension - the rubber assisters only fill about 1/3 of the coils - which gives good ride comfort when bumbling along, and its never grounded again.

Got the ideas for all this from reading the various historical threads, so lots of people have had the same problem.

[Dave R]

where are you measuring the 5 1/2 inch ride height from ?

 

my subframe is a lot lower than that

[Guest old_timbo]

Bottom of the chassis rail just in front of the rear wheel. Think it is supposed to be about 6 1/2 - 7 inches.

[Dave R]

will measure mine tomorrow

but from memory i only have 3 inches clear from the lowest point with 16 stone sitting in it

[Grim]

anyone know what the bolts for the rear subframe are? i need to replace my quite soon.

[Guest old_timbo]

Original Bolts seem to be 100mm x 12mm. The replacements I fitted after washer mods were 80mm x 12mm. Originals length would have stuck up too far into the car - stick up a fair distance when a nyloc is used anyway! Was trying to find some nice stainless socket button head screws to do the job and minimise the risk of damage, but then I found I had a couple of hex head bolts of the right size knocking around so the quest ended.

[Grim]

Are they high tensile bolts at all?

Can you post a picture / diagram of your 'washers instead of cups'? I didn't build the car, so i've no idea how it's put together.

[Guest old_timbo]

Bolts aren't anything special. I'll try and take some photos later.

[Grim]

cheers