OK, I HAD 200# springs on my car's Protech dampers. I went to LONGER, 600# springs. This gave reasonable ride height, using 13" wheels
(although I could use more for the road). This is too stiff all round.
Question: can I use the shorter 200# springs without changing the ride height? How might I increase the ride height if necessary?
If you have preload collars on the suspension, you can wind these up towards the top, but this will (as the name suggests) preload the springs and give you a firmer ride, as well as less bump protection against speed bumps, potholes etc.
quote:
Originally posted by MakeEverything
If you have preload collars on the suspension, you can wind these up towards the top, but this will (as the name suggests) preload the springs and give you a firmer ride, as well as less bump protection against speed bumps, potholes etc.
Within reason pre-loading the spring dosen't make the suspension harder but it will (normally) increase the ride unless the
shocks are already fully extended when the car is sitting normally with its weight on its wheels
However I am confused 200# and 600# ? lb/in ?
Springs are normally rated by poundage that is pounds/inch, the free length and id .
200lb/in is very soft but a jump from 200 lb/in to 600lb/in is a truly massive jump.
With short 200 lb/in springs if you pre=load them too much you might run into the problem of them becoming coil bound before the bump stop does its
stuff.
What poundage spring is used at each end of the car depends on a lot of things somebody might be able to give specific advice if you tell us what
chassis and engine you have.
[Edited on 5/2/12 by britishtrident]
Chassis: MK, independent rear, MX5 hubs
Came with (never mounted like this): 200 pounds/inch
NOW: 600 pounds/inch; I was originally not sure I could license it for the road, which I have now done
I am going to change over anyways. If it doesn't look like it would be liveable (ie. not enough clearance), I'll just order some 350#, and
go up from there if necessary. You can rent the spring compressors.
I'm far from a suspension expert, and only know what I have found from playing with bikes. Progressive springs do get stiffer as you preload them, by design. By preloading them, it pushes the top collar upwards and increases ride height.
quote:
Originally posted by RK
Chassis: MK, independent rear, MX5 hubs
Came with (never mounted like this): 200 pounds/inch
NOW: 600 pounds/inch; I was originally not sure I could license it for the road, which I have now done
I am going to change over anyways. If it doesn't look like it would be liveable (ie. not enough clearance), I'll just order some 350#, and go up from there if necessary. You can rent the spring compressors.
quote:
Originally posted by MakeEverything
I'm far from a suspension expert, and only know what I have found from playing with bikes. Progressive springs do get stiffer as you preload them, by design. By preloading them, it pushes the top collar upwards and increases ride height.
Even progressive springs will not change their rate with preload, preload merely determines how much force you have to apply to continue compressing
the spring. A spring's stiffness or rate is set as a function of the mechanical properties of the spring, you can't change it. A 200lb/in
spring with 200lb of preload on it will not start to compress until 200lbs are applied, however after that it will continue along 'hookes
law' and compress 1 inch for every 200lbs applied. Similarly a progressive spring with a specific function (ie F=kx^2) with 200lb of preload will
only start to compress once 200lbs have been applied, however after this it will continue to to obey the same function.
It should probably be pointed out that unless you are running zero droop (which you only do for very specific reasons and certainly not on a
spaceframed road car) there is no preload on the spring with the weight of the car on it.
Free length, 200#: 6", Free length, 600#, 8"
This is all very good information you are providing. Thanks! I have a much better idea how to set it up now, with the goal of softening things up, so
the car can turn better, whilst keeping reasonable ride height.
out of curiosity what is the uncompressed length of the dampers between mounting bolts
longer. i am not home atm, but will check. i suspect 12?
The dampers supplied with my indy appear to be 13" between bolt hole centres with 9" springs
http://www.protechshocks.co.uk/dimensions
tony
[Edited on 7/2/12 by mad-butcher]
[Edited on 7/2/12 by mad-butcher]
Then they are probably 13". The ID is 2" though, or very slightly under, therefore the commonly found 2.25" ID is the only one that will fit.