Suspension upgrade

[LesG]

Hi, I have an older ('85) de-dion chassis car, with the Triumph trunnion type front uprights originally.

I have upgraded my top and bottom front wishbones to standard-track tubular type, and also bought new uprights to do away with the trunnions and utilise the spherical joint in the later type bottom wishbones.

Still with me? Good!

I have bought a nearly-new set of Superlight R road-going Bilstein shocks (MO suffix) with the Eibach springs on adjustable platforms, and have found a problem. both the front and rear units are about 2 inches longer than the units I am replacing!

Now then, surely I'm not the first person to try this conversion? Obviously I'm going to have to fabricate a new top mounting for the front struts, and weld into place. This I don't think will be too difficult. The other thing that is troubling me is, the length of the rear units. As they just bolt into position, will I be able to lose the extra length by simply winding up the platforms? Or will I have to get a shallower top-hat for the spring? Can anybody out there help?

Les.

[Irrelevant]

You have dampers from a newer car(for c.97 -> anti-dive front geometry and progressively sprung rear dampers) - these are longer at the front and rear.

You should have spacers on the front ones - just take them off and the dampers will fit.

Rear - you're bu99ered if your dedion does not have lower mounting points as well as the older 'through the tube' holes. If you fit the long rear dampers through the holes that go through the middle of the dedion, the dedion will hit the chassis rails on full extension(i.e. over big bumps or hard cornering).

[LesG]

Hi Adam,

For the front shocks, do you mean the wide-track spacers? I have already removed them, and they still look too long, but you think they'll fit without moving my top mount on the chassis?

As for the rear, I've bought a newer de-dion tube from ebay, I'll have to check what you mean by the 'through the tube' mounts etc., but there are 2 differences that I've noticed; one is the triangular box-section is a lot wider than my original; and the other is the tube is approx. 10mm wider than the original. The mounts appear to be the same, but without having another look, I'm just guessing here. I'll try and get into the workshop tomorrow and take some measurements etc.

Cheers!

[Irrelevant]

one is the triangular box-section is a lot wider than my original

This will not fit between the bracing chassis bars that run between the rear of the floor and the back of the rear basket. These are simple to move though, mine's had it done.

still look too long, but you think they'll fit without moving my top mount on the chassis?

---

Yep that's what I was thinking . .. . now you mention it though, I think you're right about the fronts - they are too long - IIRC(without checking), std is 12" or so, anti-dive 13" or so, and wide track antidive is 14"ish with the spacer on.

Front suspension mounts are not a simple move and I wouldn't take that route if I were you. You'll need to peel back and then reshape your sideskins as well remember.

Sell the wrong dampers you have now (which will fetch a good price as they're for the recent chassis) and get the correct dampers. The new dedion is worth fitting though as the wider brace is stronger than the narrow one and a bit of extra rear track is nice.

[LesG]

I don't suppose you have any 'before' and 'after' pics of your rear bracing bar mods? The newer de-dion bar is a lot nicer/newer than the rusty old thing I have, so that's defo going in. I'm still undecided about the shocks though, I'm reskinning the chassis anyway, and realise now that the (earlier) skins I've ordered do have the hole in the wrong place for the later struts. Doh! I thought these cars were all the same!

Thanks for your input, I take it you have a similar, early car too?

[Irrelevant]

I don't suppose you have any 'before' and 'after' pics of your rear bracing bar mods?

Nope - just move them both about 2" further out at the back - enough to rest the de dion tube on the outer rails without the triangular bracing hitting the tubes we're talking about.Position isn't critical as these tubes don't do much other than support the rear end.

If you're determined to change the front mounts - you might be able to get the real mounts from Arch if you ask them nicely. Remember that these are normally brazed on rather than welded. I don't know if changing the way such a highly loaded area is constructed is a good idea - well it isn't to be honest. But it may be OK if the welding's done to a high standard, but it might not . . . I'm not a metallurgist. Safe bet is to bronze braze it or get Arch to do it. This will likely cost their minimum fee of £150 and they will ensure the alignment is correct. They can do the back tubes for that as well as £150 will get you just over 3 hours work.

[LesG]

Ok, I'll give Arch a bell tomorrow, and see what they say. I already have all the outer skins from them, and maybe this'll spur me on to get them to do the whole job together! Potentially, they may even swap the earlier side skins for the later type, if they'll change the shock mounts for me? I'll let you know, cheers!

[LesG]

Ok, this is turning out to be a bit of a blog!

 

Right, after spending some time scratching my head in the garage last night, I'm now a little clearer! The newer de-dion has the lower mounts as you described, not the older 'through the tube' type on my original. I have to confess, I thought the radius arm mounts were the shock absorber mounts, what an idiot! This car I've bought was completely disassembled, and I haven't looked at a completed (or even part-built) rear suspension set-up before starting the job! Typical bloke I hear all the women calling!

Also, the two rear support bars you mentioned don't appear to need moving, as there seems to be plenty of clearance for the wider bracing.

[Irrelevant]

LesG: What car did you buy . . . . is it red by any chance?

What did Arch say about modifying the front suspension mounts? If you haven't called them yet, ask for Bruce and see if he wants the old mounts stripped off and the area prepared before you take it to them - this time consuming yet unskilled task will save money and make them more likely to do the job as a £150 job rather than a big job.

[LesG]

Er, yes, it was red originally, been over-sprayed white before I got it though. Should I be worried by your question lol?

I did ring Arch today, however, I made the mistake of calling after they'd all gone home! 1pm finish on Fridays it seems, so I'll try again on Monday, asking for Bruce as you say. Is he the 'top man'?

[Irrelevant]

Yep - Bruce is main man. They often work Friday afternoon but won't answer the phone.

If it's red on white, I don't think it's the one I was thinking about. Just thought you might have bought the red one on Pistonheads whose H reg and ID was moved to another car.

[LesG]

Will contact Arch on Monday, I'm gonna have a trial-fit of the rear suspension tomorrow and, if all's well with that, I'll defo plough on with the front mods.

The car is white on red, and is a Q plate (original kit-build). Was with the guy I bought it off for the last 2 years, and was barely used at all. So no, not the one off PH. The car had actually been laid-up in a barn for about 7 years prior to him buying it, and this accounts for the general decayed condition overall.

[LesG]

Ok, the rear struts do fit, as I HAVE bought the later dD tube with the lower mounts as you pointed out! Also, those two rear bars WILL need moving out as you mentioned, that triangular bracing WILL foul! I'll have a chat with Bruce tomorrow, and see how soon I can get the chassis down to him. Will be much more sensible to have them fit the new alloy panels that came with the car too. Jeez, I'm getting a bit giddy now, this car might even run one day!

Cheers for the help and advice Adam!

[LesG]

Er, I think I might just stick to the original chassis mounts and shorter struts! To do what I was proposing to do apparently requires a new long front! Looks like a trip to the sand-blaster with the old de-Dion, anybody need some late-spec Bilstein/Eibach struts? ☹️

[MartinWoodham]

[o/t]

Hi Les, which bit of Cumbria are you in? there's a dearth of Caterhams there, which I find surprising...

I'm an occasional visitor to the Northern lakes

 

Martin

Aero'd supersported ex-Roadsports B...anyone got a cheap LSD/ 6 speed box?

[LesG]

Hi Martin, I live in Penrith, on the edge of the Lake District, and I know what you mean about a lack of Caterhams! Mind you, they ARE there if you know where to look! If you're planning a trip up here and you're in need of some local knowledge, just ask, you're more than welcome. I live only five minutes away from a fabulous blat route, a road that was voted no. 5 or 6 in the UK top 10 best driving roads; the A686 Penrith to Alston, or 'mini Stelvio', as I like to call it! Definitely worth a look if you're up here in your Caterham!