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MG Midget and Sprite Technical - Suspension Setup

Hi Guys,

I am struggling with getting a good setup for Autosols on my K powered midget. Currently I have 340lb 1" shorter front springs, 11/16 ARB, 1" shorter rear springs and frontline front and rear damper setups. I am running 6 click on the front dampers and found anymore than that produces terminal understeer. The back I am running 7 clicks. The car squats under acceleration and also moves rolls alot with the fast changes of direction amd resulting in a very loose back end needing very carefull power delivery. Should I be going stiffer on front springs, maybe different rear springs? I am currently not running a panhard rod but know that one is needed but suspect it is more than just that

Any suggestions?

Thanks

Michael
Michael Weeks

Try 400Lb springs from Peter May, they are good quality and rated at what they say.... :-)

Soften the back up a little.

Try the Peter May Alluminium spring mounting pads... they work wonders.

If it were mine, I'd ditch the Frontline rear shocks and go back to the Std Spridget ones...

Mark.
M T Boldry

Sounds like your rear is a bit stiff?!
Rear should be softer than the front...
Onno Könemann

If you're using sticky tyres, you might find a Panhard or similar will make a difference; like above, try undo the rear dampers say 2 clicks at a time.

A
Anthony Cutler

I don't have any specific advice, just more of a general tip I think.

If you think your front is having issues it may not be the set up at the front and vica versa. For instance, you could make the front 'harder' or, alternitavly you could make the back 'softer' both will have a similar effect in balancing the car.

This is broadly speaking correct isn't it all you racing boys?

Cheers,
Malcolm

M Le Chevalier

The trick with any live-axled car is to control it from the front. Ie stiff front, soft rear.

You aren't going to develop the corner speed of a Race car in an Auto Solo so there is no need to go psychotic on spring rate.

I would do the following:

Front Springs: 400-500lbs

ARB: Leave as is for now.

It sounds like your back end woes are a combination of Roll Steer (to soft a front), sideways movement, and I'm betting a pound to a pinch of salt here, torque and roll induced axle tramp. The 'squat' you are getting under acceleration is actually Torque induced Tramp - basically the cart spring rear set up isn't up to the torque of a K Series lump.

Furthermore, whacking up the damper rate on the rear of a Midget just doesn't work well!

So you need a tad more control on your rear axle, this means:

1. Panhard Rod - this will prevent sideways axle movement and also lower the rear roll centre a touch (meaning less Roll Steer).

2. Positive axle clamping at the U Bolts. Even nylatron spring pads here are pretty useless, so go for some of the 'Gucci' alloy ones. These are sold by Dominic Mooney (not Peter May) at Midlands Classic Restorations (Dom is a fellow Spridget Racer and all round good egg).

3. Cut down the axle tramp. Get some extra spring clamps, heat them cherry red with a gas torch and clamp them tightly around the spring FORWARD of the axle (FORWARD ONLY, NOT AFT).

4. Vertical Monotubes work well on the rear of a Spridget (we have them on the Racer), but ONLY if set up properly. The Frontline Avo are WAY too stiff and you need to check that they don't hit the internal bump stops when the suspension compresses (they are marginal on a lowered suspension). On our Racer we run 1 - 2 clicks (and we develop FAR more cornering load).

I'm looking at getting Pro-Tech to build up some bespoke dampers to replace the Frontline Avos.


The fact that you get Understeer when stiffening the front dampers is indicative of a geometry problem (and the Frontline kit is NOTORIOUS for this). So check your Camber and Castor settings.
Deborah Evans

Michael,

It sounds like your dampers are possibly too stiff. One of the problems you can get with that is transient handling issues such as understeer when the car is in the process of rolling but not when it has settled into the bend, do you know whether your current set-up exhibits that symptom.
David Billington

I learned secondhand (fortunately) that stiff rear shocks can yield massive oversteer in an autocross.

But, that's what the customer insisted on.

I changed his shocks back to soft.....

..... and sold him a rear wing. ;-)

Peter C
Peter Caldwell

There is much talk of 'soft' and 'stiff' as regards damping levels, in this instance for the rear.

Does anyone have any figures for damping levels they have used or force-velocity / force-displacement graphs for any of the dampers mentioned.

I appreciate that lever arms represent something of a challenge to extract such data

Cheers

Spencer
S Deakin

Spencer,

I think that data may be hard to come by unless you test them yourself. I knew a race engineer some years back that asked for this sort of information from some makers and didn't have any joy.
David Billington

Hi David,

Yes some manufacturers don't have the data! and some prefer not to give information (usually because they have trouble making two dampers the same),

I have measured some myself in defining the damper curves I will use for my front telescopic dampers.

I was originally going to get Protech make some to suit (who wouldn't supply me a characteristics for their 'off the shelf' units)

But then a contact at Bilstein did me a favour in agreeing to revalve units to my spec which I should finally pick up next week.

Who was the race engineer? I might know him it's small world - especially the race engineering one!

Cheers

Spencer
S Deakin

Spencer,

The race engineer was Chris Norris and he was working at Ray Mallock Ltd at the time around 2000, he then moved to get some race work in the US with NPTI IIRC and is currently, last I heard, at Swift Engineering in California.
David Billington

David,

The name is familiar or I might be confusing it with another Norris (Steve) I worked with, I knew Phil Barker, Pete Harrison, Stuart Ayling from RML and know the guys who work there now very well. Ray was very helpful recently when I asked about the Mumford configurations Arthur used.

Cheers
S Deakin

Spencer,

I worked at RML for about 6 months on the GT40 project around 2001. Met Arthur once also. I know of a Steve Norris that used to work for Unigraphics, he was a mate of a mate, now living in Devon IIRC selling windows. May be quite a common name though.
David Billington

David,

I worked with RML for a good few years on and off, nearly going back in 2002-3 but was tied up contractually and couldn't move in time.

I used to regularly see the GT40's in the workshop but that was early to mid 90's when they worked from the 'farm' unlike the current setup which is much more posh ;)

Steve Norris was a CAD jockey as well as a Race Engineer so he could well have been at Unigraphics at some point, but I think he is in Swedish Touring car now
S Deakin

Spencer,

It wasn't 2001 I was at RML, it was 1991, a bit of brain fade on my part. I think another Steve Norris in this case. Probably better let the thread get back on track now.
David Billington

Defo go with Debs advice (especially now she's been in a car with me driving and survived to tell the tale;)!) - but, you don't even say what tyres/pressures you are running - which can also be a factor.
rachmacb

Spencer

What are you having done to the shocks and for what use?
I am slowely thinking about changing the FL avo's but have not found a good alternative...
Onno Könemann

I know that the tyres are a bg factor and it is currrently running GT2's. Under Autosolo regs you are not allowed to be list 1b so have to be standard road legal. Was thinking maybe go to Yoko A008's.

Pressures were 28psi all round, originally back were at 30 but seemed to be a bit better after dropping them.

The understeer was intial understeer and being the couse layout was all slallom you could not see it it disapeared when settled
Michael Weeks

Michael,

Apologies for the thread de-rail, just trying to quantify what was considered as too 'hard'

Onno,

I will answer on my 'XE midget progress' thread if that's OK so as not to mess the thread up any further

Cheers

Spencer
S Deakin

I'm always surprised when advice is given on spring rates when the weight of the car is unknown and might vary from 550 to 900Kg.

What does the car weigh with a typical fuel load and how much do you weigh?
Daniel Thirteen-Twelve

I have Armstrong's performance curves for their Adjustable 22 lever shocks saved as a PDF. If anyone would like a copy emailed to them, send me an email. I don't think I can attach it as a picture, but will try.
(nope... can't)
This is what we have been doing with our adjustable units, with some success.

Peter C
Peter Caldwell

Oh Daniel do wind your neck in. If you read my post you would notice I gave a RANGE of spring rate based upon:

1. The OP made no mention of lightening the car.

2. It's got a K Series in it so is significantly lighter at the front than an A Series or 1500 Midget.

3. From his description he is OBVIOUSLY getting Roll Steer around the front axle.

But then, what would I know about setting up Competition Cars?
Deborah Evans

Daniel

It is a RWA full steel body 1.8 K-Series Midget and therefore running approx standard weight less the difference between the engine transmission combination.

One last thing also running a tran-x lsd

Deborah

many thanks for all your comments, i shall investigate them all further (spend money lol) and have some changes made before the next event.
Michael
Michael Weeks

Deb, take some chill pills! And list your race winners...

If it's got a K-series the engine is lighter but it will have a Type 9 which is heavier.

May have a roll bar which is heavier.

Drivers weight can vary from 10 stone to 20+ stone.

Hi Michael,

find a local scrap metal dealer and get it weighed in the condition you will compete with it, including yourself, bearing in mind the bridge can round up or down. See if you can borrow a camber gauge to use while it's on the bridge because even with a Frontline kit, when a Sprite/Midget is lowered can still have positive camber.
Daniel Thirteen-Twelve

Whilst the oldies argue over racing (which is different!) then the best advice I can give you is to go to as many as you can and you'll see who is winning and find out what they are using - you'll be surprised as to how little they have done or spent - so don't feel you have to spend loads.

As for tyres - yes, yokohamas are great - also toyos are good. I run goodrich directional on the front and that helps on the road too! Increase your pressures as well and go 2 higher behind than in front.

Would be interested to see a kseries doing this since none of them are prepared to put their money where their mouths are at the Lincs event the day before Midget50 to see if they can beat Ian Webb...!!!!
rachmacb

The answer to do what people are winnig is last event was won by a caterham 1.6K just and the previous a S2000

The Autosolo before Midget 50 clashes with the the autosolo at Abingdon CAR-nival and my birthday so still not sure what to do
Michael Weeks

Lol depends where you are spending the night then!
rachmacb

Michael
Are you doing the Oxford MC A-Solo at Silverstone this coming weekened 08/05 ?
I am entered, we could discuss your setup if you were there.
I will probably enter the Lincs M50 ASolo if you fancy that.
As Deb says you dont have to spend much to sort the car, but IMO your rear axle location probably needs attention to detail, as the extra torque of the K is making that move around more... than say mine which only has std engine power to cope with. Get all the bushing in tip top condition (probably you have already) and sort the clamping and chuck out the rubber spring saddle and replace with the ali one as suggested. Add panhard rod also.

Ian
Ian Webb '73 GAN5

This thread was discussed between 03/05/2011 and 04/05/2011

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