Rear spring rates and shock absorbers

Information / Questions and Discussion -
Imps and Imp based Motorsport stuff from the olden days and current
Post Reply
User avatar
knutspeed
Posts: 88
Joined: Sun Oct 25, 2009 7:01 am
Club Member: No
Car Model: Sunbeam Imp Sport

Rear spring rates and shock absorbers

Post by knutspeed » Thu May 16, 2013 6:48 am

Does anybody have info on what was used on the special saloon Imps way back when, or indeed if somebody are running slick-shod cars today?
I know the Maguire cars were far lighter than the GP2 cars, but what about the Rawlson cars?

What makes my head spin is that we're running two identical cars, identical springs, but one is far softer than the other. From what we're thinking, we need to go at least 25-30% stiffer than the currently fitted 800 lbs springs to try and keep the outer rear wheel from going through the roof.

We're running wide Avon ACB10s. much like the size on the Bevan car in the final years, and spats. Even with narrower Yokohamas (pictures below) I find it hard to keep more than 3 wheels on the ground and off the inner arches. Rear shocks are Spax, set to full stiff.

Image
Image
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
FIA App K Historic Racing Imp - Bevan Tribute - www.shag.no
SimonBenoy
Posts: 947
Joined: Mon Dec 01, 2003 8:27 pm
Club Member: Yes
Car Model: 68 Stiletto, 72 G15, 67 race Imp, 3 projects
Location: Stevenage, Herts

Re: Rear spring rates and shock absorbers

Post by SimonBenoy » Thu May 16, 2013 11:56 am

Matthew - I think that perhaps the Spax are your problem. I used to run Spax but they struggled, particularly through slow corners as the rebound wasn't sufficient causing hopping. Rear shockers are crucial on an Imp and I have fitted better ones (I find them better anyway). I know that some of the other HRSR cars also have replaced their rear shocks. Mine are single adjustable Nitrons (as I had a contact in the trade) but other cars are fitted with other makes which also seem to work well. Don't worry about the inner front wheel - it is rarely in contact with the tarmac through corners!
User avatar
knutspeed
Posts: 88
Joined: Sun Oct 25, 2009 7:01 am
Club Member: No
Car Model: Sunbeam Imp Sport

Re: Rear spring rates and shock absorbers

Post by knutspeed » Thu May 16, 2013 12:10 pm

Thanks Simon! Our other car is running proflex dampers which seem to work better. Time to go shopping!
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
FIA App K Historic Racing Imp - Bevan Tribute - www.shag.no
Post Reply