De Dion tube variants and advice

[paul_w]

Hoping for some pretty niche/detailed knowledge and advice on De Dion tubes please! I am recommissioning my father's 1987 BDR HPC which he has had since new. It was restored in 2016 after a rear suspension mount pulled out of the rotten rear chassis rail. The car had been used in all weathers and had once been hit up the back by an errant French lady motorist so it wasn't too much of a surprise that the chassis was rusty, although the powder coating had been hiding it very well. It had a full chassis restoration and re-skin by Arch, then paint, rebuild and restoration at Kenrick Motors in Llangollen, who did an excellent job. Sadly, Dad has been ill for a few years and can no longer drive, and he has given me the car as thanks for all the time caring for him. I have just sold my Sigma car to raise funds to get the HPC back on the road.

So, the De Dion tube conundrum... It's the original, and I'm worried that if the chassis had rotted from the inside out, there is a good chance the De Dion tube is rusty too. It's the original drum braked type, and if I've understood this post correctly, then they aren't particularly strong anyway. The other thing is that I really liked the progressive springs on my Sigma car, given that they worked well both for when we pile up the car with luggage and drive across France, and for blats on my own, so I'm wondering if it is possible to fit the later shocks and progressive springs to an early De Dion car (and ideally keep the drum brakes, as they work fine and I don't really want the extra expense of changing out the rear brakes).

Post 11 in this thread suggests that the wider triangular section on the later tubes (post '94) will foul an earlier chassis.

So does anyone know:

- if there is a stronger version that will fit a pre 94 car with the lower damper mounts to take the longer dampers and progressive springs?

- if the tubes are interchangeable between drum and disc?

- if suitable shocks for the progressive springs are available with the stud type mounting at the top?

- if I'm really worrying too much and even pounding along bumpy French roads it will probably be ok?!

Any help appreciated

Cheers,

Paul

 

[ChrisC]

I believe the Narrow Buttress tube is what your looking for.  It has both lower and middle mounting points for the shocks and was recommended to me by Arch for my 93 car.  It's also stronger than the original being made of thicker steel. Not sure about drum brakes on a dedion car, I have never seen that.

[Nigel Blandin]

I agree with Chris on the tube, my '90 HPC tube broke and I replaced it with the later one, no problem. It would probably be worth asking Redline about the best fit. 

I never saw a de Dion with drums, but the first couple of years production apparently did have 9" drums.

[Jonathan Kay]

I have the 1988 and 1996 Assembly Guides. Please let me know if you would like copies.

Jonathan

[TomB]

I'd give Arch a ring and ask for advice. Caterham are unlikely to be much use. 

[ChrisC]

They still list the narrow buttress tube https://caterhamparts.co.uk/de-dion-tube/2588-de-dion-tube-s3-90-92-narrow-buttress.html

 

[paul_w]

Brilliant, thanks all - I did see that on the Caterham site Chris but wasn't sure if it was what I needed. The car was ordered in '86 (after Dad and I went to the Motor Show) and registered in '87 so an early De Dion with drums. They work fine, though probably a bit heavier than discs - if the De Dion tube part numbers stayed the same across that change I'll assume it's not an issue.

I'll try Redline and/or Arch and see if they can supply one