Page 1 of 2

suspension issues

Posted: Wed Jul 10, 2019 7:10 pm
by Firstcall
hi to all .first post of im sure many on my new project .i have a 1976 3 ltr beast thats just in need of a lot of TLC. but with it i also received a rather large folder containing paperwork from the day it was purchased.so that aside someone has fitted spax adjustable front and rear shocks that are unbearable on all road conditions as its like driving sitting on concrete seats.
so i would like to revert back to softer suspension, has anyone have an idea on what will fit my car thats softer ?
many thanks
steve

suspension issues

Posted: Wed Jul 10, 2019 8:03 pm
by TrevorG
Are they spax adjustables? If so, try winding them down first as someone may have put them on max hardness!

suspension issues

Posted: Wed Jul 10, 2019 8:07 pm
by Rev Light
I use Protech. I deliberately specified them for road use. They are a bit tasty, and I am very happy with them. Also, they are made in Wiltshire, which means that they are local to me.

suspension issues

Posted: Wed Jul 10, 2019 8:35 pm
by Oldconn
I've just put a pair of Spax adjustables on the back of my GTE. I first set them at about halfway, ie: ten clicks up from full soft. The ride was unbearably hard . I took four clicks off and the ride improved a little. Then I took two more clicks off , so then they were only four clicks up from full soft. That made all the difference, now the ride is firm( I have 350lb springs) but forgiving , I can thrash it down our local bumpy lanes, and it will ride over the "sleeping policemen" at 20mph without feeling as though the back axle is about to kick me into orbit. The moral- play with them .

suspension issues

Posted: Wed Jul 10, 2019 9:04 pm
by Roger Pennington
Welcome to the forum :D

As well as playing with the damper adjustment, it would be worth looking at the suspension bushes - there are quite a lot of them, originally they were rubber but they are often replaced by polybushes, which tend to be harder, and if either type are worn out (getting near to metal-to-metal contact), then things may be harder still

suspension issues

Posted: Wed Jul 10, 2019 9:16 pm
by Coupe Racing
350lb at the rear is very stiff no wonder you have problems

suspension issues

Posted: Thu Jul 11, 2019 12:05 am
by Firstcall
many thanks for all the reply's yes they are adjustable but even the lowest setting is unbearable.so im on the lines to changing the whole lot .also someone has replaced all of the rear bushes for Polly bushes and this is good in some respects but with the suspension it just makes the whole car unbearable

suspension issues

Posted: Thu Jul 11, 2019 8:00 am
by Oldconn
Coupe Racing wrote:
Wed Jul 10, 2019 9:16 pm
350lb at the rear is very stiff no wonder you have problems

Yes, I know, that's how the car came to me. However, with the new shockers set fairly soft it rides better than ever it did before.

suspension issues

Posted: Wed Jul 31, 2019 11:01 am
by tony1966
Firstcall wrote:
Thu Jul 11, 2019 12:05 am
many thanks for all the reply's yes they are adjustable but even the lowest setting is unbearable.so im on the lines to changing the whole lot .also someone has replaced all of the rear bushes for Polly bushes and this is good in some respects but with the suspension it just makes the whole car unbearable
if the spring preload is adjustable try slackening it off a little,lots folk preload the spring far too much on coilovers-makes the car a bit like a pogo stick

suspension issues

Posted: Thu Aug 08, 2019 1:11 am
by Dennis Nicholas
Spring preload???
A spring is just squashed enough to fit it onto the damper. For fixed seats the damper and spring rate and length are fixed to give the car its correct ride height. For adjustable seats the spring is compressed, if necessary, to fit on the damper then the seat is adjusted to give the car the right height......the spring does not get more or less "preloaded" (squashed) it stays the same length under full car loading and the height of the car just moves upwards as you screw the seat upwards.

Dennis

suspension issues

Posted: Thu Aug 08, 2019 1:18 pm
by GavinR
The spring may be the same length under full car loading, but raising the spring seat on an adjustable seat damper can result in the spring being preloaded (precompressed) when the wheels are off the ground and the damper is at full extension
This increases the ride height as the weight of the car has to compress the spring past the preloaded point before the damper itself compresses
One of my cars (not a Scimitar) has 200lb front springs which are preloaded by 1" to give the desired ride height (and it's not possible to fit longer dampers)

suspension issues

Posted: Thu Aug 08, 2019 2:33 pm
by tony1966
it doesnt matter what way you look at it -the more you wind an adjustable platform upwards compressing the spring you are preloading it..the correct spring height is vital due to this.its normally just touching the spring to hold/locate it in place and no more when set correctly
the spring will act completely differently when preloaded[more instant resistance] rather than a nice smooth ride
the best coilovers have a height adjustment separate from the spring preload-you wind the complete unit/ body in and out of a clamp etc

suspension issues

Posted: Thu Aug 08, 2019 10:41 pm
by Dennis Nicholas
tony1966 wrote:
Thu Aug 08, 2019 2:33 pm
the spring will act completely differently when preloaded[more instant resistance] rather than a nice smooth ride
NO.
The spring is linear...eg say rate is 200 lb inch then it stays 200 lb in when you screw up the seat and the shock absorber is fully open but the spring obviously becomes shorter. Say you screw up 2 inches then there is now 400lb of pressure to be overcome by the weight of the car before the spring compresses any more. If the car weight is 800 lb then the spring compresses a further 2 inches ....the first 400lb of car weight equals and opposes the spring resistance to squash then the next 400 lb of car weight squashes the spring 2 inches.......the spring stays linear and does not become any more or less squashier. It is the dampers (shock absorbers) that controls the drop rate or rebound up rate of the car and thus the harshness of the ride.
As long as there is enough car weight to overcome the amount of load on the spring through screwing up seat, and enough travel distance in the damper piston the car will move up and down at a linear rate.......the damper can be adjusted to give less resistance or more resistance to the plunger moving.
If adjusted to give more resistance then the time it takes for the piston to move will be longer.......say you hit a bump then if resistance is high the piston does not move quickly so the bump is felt via the chassis as a jarring bump but set just right and the piston moves just enough and quickly enough to smooth out the motion caused by the bump.

Dennis

suspension issues

Posted: Thu Aug 08, 2019 10:59 pm
by tony1966
the spring is linear-but you have already pre loaded it ,it acts differently...i had an rs4 b7 last year-i set the bilstein coilovers to max height[by preloading the springs-winding the seat up] although my car was higher than a friends with the same kit and much lower it was notably firmer[same profile tyres etc] due to mine being wound up to the max settings bilstein recommended...

suspension issues

Posted: Thu Aug 08, 2019 11:07 pm
by scimjim
“Preload” is a misleading term (and almost certainly an Americanism) relating to ride height - in the same way that “coilovers” are used to describe any height adjustable damper by some.

This article explains how it’s misused - as Dennis says, from an engineering perspective it’s compressed (although it’s not strictly linear but near enough over 90% of its travel), not preloaded.