RK
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| posted on 5/2/12 at 04:38 PM |
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Ride Height adjustment
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?
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MakeEverything
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| posted on 5/2/12 at 05:23 PM |
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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.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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phelpsa
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| posted on 5/2/12 at 05:50 PM |
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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.
Preloading the spring doesn't increase its stiffness and therefore won't give a firmer ride unless you preload it past the point where
there is zero droop (that would make it a problem with your dampers being too short).
Essentially, you aren't preloading the spring with the collar, you are adjusting your ratio of bump/droop travel. If you are actually preloading
the spring (with the weight of the car on it) then you aren't increasing the ride height.
Does that make sense? I'm never going to be a teacher!
[Edited on 5-2-12 by phelpsa]
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britishtrident
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| posted on 5/2/12 at 07:14 PM |
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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]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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RK
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| posted on 5/2/12 at 09:09 PM |
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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.
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MakeEverything
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| posted on 5/2/12 at 09:51 PM |
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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.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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britishtrident
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| posted on 5/2/12 at 10:07 PM |
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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.
That sounds nearer the mark but it might be an idea to order 1 pair of 330s and 1 pair of 380s that way you can experiment with the handling
balance by swapping them front to rear.
What motor are you using MX5 ?
Somebody will post and tell you what springs they are using an MX5 powered car requirements should not be too different from a Zetec or Pinto
powered car.
You will also need to specify the free length of the springs
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 5/2/12 at 10:17 PM |
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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.
Unlike bikes rising rate springs are not the norm for home built cars. For most its range a normal coil spring has a more or less linear
characteristic ie it follows Hookes Law.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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phelpsa
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| posted on 5/2/12 at 10:49 PM |
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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.
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RK
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| posted on 6/2/12 at 02:37 AM |
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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.
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mad-butcher
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| posted on 7/2/12 at 03:36 PM |
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out of curiosity what is the uncompressed length of the dampers between mounting bolts
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RK
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| posted on 7/2/12 at 05:57 PM |
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longer. i am not home atm, but will check. i suspect 12?
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mad-butcher
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| posted on 7/2/12 at 07:47 PM |
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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]
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RK
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| posted on 7/2/12 at 10:39 PM |
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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.
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