Suspension Advice Please

[7 Minder]

One of the front Bilstein dampers is leaking on our car so I've removed both fronts ready to send off for rebuild.  However I've just discovered that the springs and dampers are different specs front and rear so need advice on how to proceed.

The fronts are Caterham part number 74501AW - "Front Spring/Damper Track M1 Specification".  These have the 77843 - "Spring Front Race 250LB Race" springs.  

The rears are 75531A -  "Damper and Spring Rear De Dion 2003".  These have 71198 - "Spring Rear Progressive Rate Standard Spec" springs.

The fronts are adjustable height but the rears are fixed.  The car is originally a 2003 kit built SV which has been rebuilt to 420R spec. 

I'm assuming this suspension combination is not recommended (unless anyone knows better) so it seems the choice is to change the front units to road spec to match the rears (so presumably 75530AWS or 38F020A on the Caterham parts website) or upgrade the rears to match the fronts (74502AR - Track M1 Spec).  Or maybe change the lot for something other than the Bilsteins.  Road use only so far but some track days planned, starting at Castle Combe in just over a month.  The fronts are pretty harsh on the road but I don't know how the standard road setup would be on track?

Finally, it needs aligning.  The original owner used the car pretty much exclusively for sprints and hill climbs apparently and I can visually see there is noticeable toe-out.  Can anyone recommend settings that would be ok for road and track day use running 6/8" Apollos with ZZS tyres.

Many thanks.

  

[Geoff Brown]

Strange that the front has adjustable platforms but the rears have not. The front & rear suspension combo as it is IMO is not recommended. Best to upgrade to rear adjustable platforms to get the best out of the car ?

Historically the R400D has always had progressive rear springs so one would imagine that the 420 would be the same but again with adjustable platforms.

[Gareth H]

If one of the fronts is leaking you can probably assume that all the dampers are past their best, and with front / rear spring rates not matching it could be a good time to consider other options

[Golf Juliet Tango]

Progressive rear springs have been standard fitment for decades. My 1996 live axle car started out with them.

I would agree that adjustable platforms all round are a step forward.

Before you get your Bilsteins refurbished, as well as checking on cost, check on their turnaround time. I found it advantageous to go to Protech whose dampers are inherently adjustable for platform and for rate, so you are two steps forward. Time between order and supply was a week, Bilstein offfered me four to six weeks for refurbishing. Cost difference was small.

https://www.protechshocks.co.uk/

 

[Tazio]

Regarding the current Spring rates, 250 fronts, progessive rears, they are the rates I have used on my 2 litre VX for years, I've tried lower rear spring rates, but found overall the progressives worked best for my driving. The 250 lbs rate fronts is a quite normal 'upgrade' to prevent the front of the car bottoming on our increasing poor quality road surfaces.