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]

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

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

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]

Just out of interest, what spring rates do you have fitted, as that could have a big effect on the handling. Cheers Ray

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

quote:

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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.

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quote:

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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.

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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

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