mediabloke
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| posted on 27/11/08 at 11:03 PM |
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Adjusting ride height of an existing setup
One of my winter tasks is to sort out the speed handling of my MK Indy. From 70mph upwards, the handling sharply becomes light & twitchy. Not a
problem on the track, but it makes for an interesting motorway drive... So I thought I'd look closely at the ride height and springing. A bit
ambitious for my first time tackling these adjustments....?
I took the following no-load height measurements between the lowest chassis rails near each corner and the garage floor (a good flat surface):
O/side front 12.0cm 14.0cm O/side rear
N/side front 12.5cm 13.0cm N/side rear
These don't look right to me. Different front:rear ratios between each side of the car just seems wrong, but I haven't found any
definitive starting points as yet. 
Daft question - does anyone have an idea of the best approach to adjust the ride height? Do I unload the springs, measure them and start again from
scratch, or should I dive in & make some trial adjustments using the collars on the coilovers?
Measurements from other MK / Locost owners' measurements would be really helpful too, if anyone's happy to share them. 
Thanks in advance - Francis.
[Edited on 27/11/08 by mediabloke]
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Chippy
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| posted on 27/11/08 at 11:45 PM |
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You need to adjust the ride heights on opposite corners, so N/S front to O/S rear, O/S front to N/S rear. To get them even you would raise O/S front
and N/S rear, until both fronts are the same, and both rears the same. This "should" give equal weighting both sides, (but probably
won't), :-) Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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procomp
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| posted on 28/11/08 at 08:07 AM |
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Hi.
The exact figures of the ride height are not nesaceraly what you want to be looking at.
What you would want is to have the car corner weighted correctly tacking into account the general desired ride height that is necessary for the
application. it is more important to get the corner weight right than worry about the ride height being 5-6 mm up or down either side. It is all
dependant on where the masses are located in the car - the weight of the driver - the weight of the engine - bec cec - big battery small battery where
is it etc etc. And of course any twist in the chassis.
You will however find that it is worth playing with the camber tracking ride height thrust line springs first to try and gain better handling as any
adjustment made in those areas will affect the corner weights so leave that till last.
Cheers Matt
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mediabloke
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| posted on 28/11/08 at 06:29 PM |
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Thanks Ray / Matt for your advice - it's helpful to know where to start.
As it seems to handle perfectly below 65, I was wondering if the problem was one of lift, at first. Even with the throttle feathered, the tail feels
noticeably more loose at 70+ than a few mph less. However, as I'm also familiar with the sound of a stainless-steel tail pipe on tarmac when
cornering hard (box & hanger are secure) would the spring tension of the rears be something to eliminate first?
What do you reckon?
[Edited on 28/11/08 by mediabloke]
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Chippy
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| posted on 28/11/08 at 11:23 PM |
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Just out of interest, what spring rates do you have fitted, as that could have a big effect on the handling. Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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mediabloke
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| posted on 28/11/08 at 11:45 PM |
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Not sure at the mo, Ray. If I've read some earlier posts correctly though, I should be able to calculate the rate from the no. of coils, spring
diameter and wire diameter.
I'll measure them and post back.
Cheers - Francis
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mr henderson
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| posted on 29/11/08 at 12:39 PM |
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quote:
Originally posted by mediabloke
As it seems to handle perfectly below 65, I was wondering if the problem was one of lift, at first. Even with the throttle feathered, the tail feels
noticeably more loose at 70+ than a few mph less.
Presumably this change is noticed when you are driving in a steady state situation, for instance, along a reasonably straight road?
If that is the case (and I don't know at this stage whether it is) it would suggest some kind of aerodynamic problem rather than a suspension
problem.
Be wary of measurements between chassis and the ground, as there may be some distortion in the chassis which would respond better to corner weighting
that absolute measurements.
John
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mediabloke
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| posted on 29/11/08 at 11:56 PM |
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quote:
Originally posted by mr henderson
Presumably this change is noticed when you are driving in a steady state situation, for instance, along a reasonably straight road?
If that is the case (and I don't know at this stage whether it is) it would suggest some kind of aerodynamic problem rather than a suspension
problem.
Thanks for your reply, John. You're correct: it is noticeable when driving on a straight road.
It would be easy to correct if the problem occurred at low speeds, but the corrections tend to unsettle the car at high speeds.
One further thought: I'm running Avon ZV3 195/50 15s on 7.5x15" rims that were fitted by the previous owner. I notice that other LCB
members are also running 15s - can I discount this being a possible cause...?
The only obvious differences from other members cars that I can see are an air dam on the bonnet and a pair of wing stays that need straightening and
wider cycle wings need fitting. I'd have thought that the latter would affect the front end rather than the rear, though... :scratches head:
Thanks again - Francis.
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mr henderson
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| posted on 30/11/08 at 10:11 AM |
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I've not heard of people having similar aerodynamic problems, so the first thing to look at is any differences between your and similar cars. If
there aren't any, and they are not having the same problem, then I guess you can discount any aerodynamic problems.
If you are looking to reduce roll by altering the springs, then you need to consider that as you increase the spring stiffness so you will need to
reduce the unfitted length in order to achieve the same ride height.
You will need to know what the current stiffness is, and of course, you will need to remove the springs to measure their unfitted length.
Mike Capon has written an excellent spreadsheet which you can use to figure out what you need. I will post a link to it later if I can find it.
John
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procomp
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| posted on 30/11/08 at 11:12 AM |
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Hi
Before you start worrying about aerodynamics etc.
what you need to do is find out exactly what you have in terms of Camber front and rear. Toe front and rear. Castor on the front and where exactly
the thrust line is pointing down the car. Without looking at those areas first you will be guessing as to where the problem lies.
There are a few threads on the forum giving info on how to go about checking these settings. But they need to be absolutely right as measurements to
be of any use.
Cheers Matt
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