Progressive rear springs. 21 content

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Martin7H's picture
Last seen: 2 hours 54 min ago
Joined: 17/04/2014
Progressive rear springs. 21 content

Which way is the correct fitment of progressive rear springs? Tighter coils at the top or bottom. I was led to believe it was tighter coils at the top, but on my 21 they are fitted at the bottom. 

Also, there is no clearance between the springs and the seat belt inertia mechanism external bolt head. Any experience or observations from 21 owners.


Golf Juliet Tango
Last seen: 2 hours 21 min ago
Joined: 17/04/2014
Hi Martin

I no longer have progressive springs fitted but, provided nothing is fouling, then I don't see why the orientation should matter.

Your comment about the spring touching the seatbelt fixing is of more concern. Is this when not under load?


Democratic dissent is not disloyalty, it is a positive civic duty

C20 WUN's picture
Last seen: 1 day 12 hours ago
Joined: 08/06/2019

I agree the orientation won't make any difference, everything else being equal. Helper springs go on the top, but they are much weaker than the light end of a progressive spring. Fwiw there has been quite a lot of discussion about spring rates and dampers on the Caterham 21 Register Facebook page that you might find useful. I changed mine this winter to 250f/200r (linear) on the already-fitted AVO shocks which made a massive difference, if you like a sporty ride.

Guy Lachlan​

Caterham 21, 1.9 Scholar/DVA VVC 



Last seen: 3 hours 43 min ago
Joined: 17/04/2014

All things being equal, if you put the tighter coils on the bottom, you'll keep more mass of the spring lower down.  Im sure it will make bugger all difference, but its a nice idea.  Silly