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MG Midget and Sprite Technical - reducing body roll

Inspired by this by this site I've started using my 1972 midget again after a few years neglect. Thanks folks!

It drives really well but I'd forgotten just how much the body roll you get when cornering hard. It has an uprated anti roll bar (can't remember the size but it's one up from standard) and uprated bushes. The mountings are all solid and in good condition.

Any advice on how to improve this without spending £500 on frontline kit greatly appreciated.

cheers

Bob
Rob Storer

Looking for an answer to the same question as Rob!

Was a rear ARB ever offered as a factory option?

Colin
Colin Mee

Colin - no.
Both - body roll is good; with a solid axle the body can move around while the axle and wheels stay in contact with the road. If it is stiff / solid then as soon as you turn you are trying to lift the inside rear wheel and both drive and grip are rapidly lost.
That's very simplistic, there's a lot more to it than that.
David Smith

Uprated front springs (along with your uprated swaybar) make a big difference. I probably wouldn't recommend a rear sway bar (not that I've tried one), normally accepted practice is to control body roll with the front, allowing the rear to move around a bit to keep the driving wheels on the road. My car corners pretty flat with uprated springs and 3/4" sway bar (and Frontline front conversion - shouldn't make a big difference to body roll, though the bit of neg camber couldn't hurt).
Andrew F

3 Little words

Pan hard rod!

Without a doubt the car.should have came from the factory with a rear pan hard rod it completely changes the personality of the car... makes it on rails

Also red neoprene suspension bushings...a little harsh but will firm up the ride

Prop
Prop and the Blackhole Midget

Never listen to Prop

A panhard does not stop body roll!
It stops the axle moving side to side a whole different problem.

You do not want neoprene bushes unless you take the midget for a swim.
To improve handling POLYURATHANE bushes are used.
But again it won't stop the body roling.

Springs and ARB's stop body roll but as David said you don't want to lose it completely
Onno K

Lowering, especially at the front, also results in a significant reduction in body roll. So lowered, stiffer front springs plus ARB. The lowered springs will also impart some negative camber which also helps.
Guy W

Agree re stiffer springs, cheap and easy too. Standard is 277 IIRC (sorry too lazy to check the book and see if my memory is playing up) with uprated available in 340 and 400lb/in. We are well happy with the latter, but other prefer the former.

Rear antirollbar: David's description is exactly what happens at the back. Furthermore, lateral (cornering) grip at the rear is reduced:
A car with less roll will get better lateral traction at the front end as the independently sprung wheels are retained at a better angle to the road.

If the ARB is at the front, and this wheel geometry gain exceeds the loss of grip due to ARB lateral weight transfer, then more total lateral grip is achieved.

For an ARB at the rear, it's a different story if the car has a live rear axle: The ARB transfers weight to the outside (rear) wheel, so its grip is reduced. However, there is no wheel geometry gain as the wheels are at a fixed angle thanks to the live axle, so the overall situation is a loss of grip at the back. Worse still, because the car is sitting flatter there is a geometry gain at the front. So grip at the front is increased, and together with the reduction of grip at the rear it makes for early loss of rear traction. I have given up counting the number of people who wouldn't believe me, tried a rear ARB, spun out at a ridiculously low speed on the track and realised it really isn't a good idea :-)
Paul Walbran

Paul,

I would disagree as I have a rear ARB and found it beneficial in countering understeer in tight corners, not noticed any drawbacks. Maybe the detail is in the set-up as usual.
David Billington

When I built my Sprite, I installed a rear anti-roll bar. I found that he held a corner well up to a point, and then it let loose all at once and would spin violently as Paul describes. It is still on the car, but it is disconnected. It was not a good idea for autocrossing. I never found out how it would act on longer higher speed corners, but I suspect I might not want to find out. Pic below shows body roll with shorter stiffer front springs, a front ARB, and beefed up rear springs.

Charley


C R Huff

Paul's just a few out standard is 271lb, I remember these numbers off the top of my head because of all the trouble with the front lowered springs from T*ss

as well as 340 and 400 you can also get 360 (more on this later)

I had 1" 340lb lowered and uprated front springs and uprated ARB and the handling was sharper and roll and bounce less

as on another thread, if the springs are uprated the dampers may need to be also

being 1" lower gave me problems with ground clearance to the exhaust and floorpan (not that I wanted the front lowered by 1" but that's another story)

my problems were resolved by Kim Dear at Magic Midget - http://magicmidget.co.uk/

and if I'd have followed advice given by others on here to go to him at the start I wouldn't have had problems - so have a word with Kim and see what he suggests - he does the 360lb lowered springs

I've got the 360lb 'standard' ride height springs from Kim just what I (wanted and) needed at the start
Nigel Atkins

Thanks fro the advice folks. The general consensus looks to be uprated from springs. I'm more than happy with the rear. I think the rear lever arm dampers get a lot of undeserved bad press, mainly due to knackered dampers and poor quality recon units.
Rob Storer

and possibly uprated front dampers

do consider the 360lb 'standard' ride height springs as what I meant to also put but forgot was that lowered the handling is sharper but IMO and experience at standard ride height it retains more of the 'classic' handling feel for road use

and it's a matter of overall balance go too far off standard at the front you may want/need to start looking at the back

if the car's not been used for a few years new tyres could improve the handling and ride (I don't know what's best out there at the moment other than it's not the Toyo 350 set I have)
Nigel Atkins

Charley,

I guess the devil is in the detail. I did some autotests, hillclimbs, and track days and found no tendency for the back to suddenly step out. On long sweeping bends the attitude could easily be controlled with the throttle. The basic set-up is a frogeye with FG front and rear with standard front springs, 5/8" front ARB but supported further out near the bends for greater effect and supported in wider Austin A40 Farina ARB mounts. Rear spring are 15 leaf with one long leaf removed and the rear ARB was off a Vauxhall Chevette rear re-bent to suit and IIRC about 1/2" diameter and fitted nicely in between the LA mounting gussets onto angle iron bolted in place of the LA dampers. Front and rear run adjustable telescopic dampers.
David Billington

Rob

If you fit 'stronger' springs, you should look at uprated dampers also... or you could make the front extra bouncy over bumps, as the springs store and release (cyclically) more energy than can be absorbed in 1 or 2 cycles by the dampers.

It's a very unpleasant sensation.

A
Anthony Cutler

Interesting point. "stronger" springs will compress less when you hit a bump. So the movement will be less and a greater proportion of he energy will be transmitted direct to the chassis. However the compressed spring, although only shortened by a smaller amount (than compared to a "softer spring") will store and then release the remaining energy more suddenly, or more powerfully. Hence the need for stiffer dampers. But take it to the theoretical extreme of a solid spring, then all of the energy goes into the car chassis and no damper would be needed.

In real life, I find my car corners flatter by having very stiff dampers as they slow the rate at which the spring on the inside of the corner compresses.
Guy W

Guy,

Using dampers in that way is not a good thing as it introduces transient handling problems. Your car might corner flatter when cornered briefly but given a long enough corner the steady state body roll will be reached so no cornering flatter achieved except initially.

<< the spring on the inside of the corner compresses.>> It extends on the inside unless I've missed something. Cars have been built which banked but not many that I'm aware of.
David Billington

David, my car is a hybrid. It uses the undercarriage of a Virgin West coast Pendolino express. Definitely leans into the corners! - Um, well, I lean into the corners, maybe the car does lean out. A bit. ;-)

Just a road car, not using it on track, and I am claiming no expertise in suspension dynamics. The bit about stiff springs was just me trying a bit of theorising. But some years ago one of the "instructors" at Croft drove my car and was surprised at just how flat it was cornering
Guy W

I read some years back that Colin Chapman used to use soft-springs/hard-dampers for his race-cars... one of the drivers described how the cars used to 'sigh' as you were getting into them.

Going back to Guy, David:
If you have soft dampers, then you can have overshoot on roll when turning in... at least you should chose a damper setting to overcome this.

A
Anthony Cutler

One guy I knew that had hillclimbed Wiscombe mentioned his dampers pumping down during the run up as they were set too hard and when he got to the paddock at the top the car would rise back to its normal height, he backed them off to a more sensible setting to resolve the problem but wasn't overly fond of normal Spax dampers anyway.
David Billington

Before I wrecked them in a accident, my elan was fitted with rear koni inserts in the rear struts. They were very strange , with much slower rebound. The rear would "jack down" on bumpy roads!
Dan Cusworth

My car had no anti roll bar as standard, so as the general wisdom is that the best single handling mod for a Spridget is to fit one I bought a standard ARB second hand from Midget Max. It certainly improved turn in and all round handling. I ran with it for a while and slowly started to fit other bits and pieces.
I replaced the standard ARB with an 11/16ths one, fitted 400lb front springs from Peter May and 30% uprated front dampers. I left the rear bog standard except for the fact that I fitted Superpro urethane bushes all round. I also fitted 175/70x13 Uniroyal Rain Expert tyres to my 5.1/2" wire wheels. The car now handles beautifully and is not at all harsh or over stiff and the mechanical grip from the tyres is superb, probably because the other stuff is keeping them where they should be, on the road.

Bernie.
b higginson

This thread was discussed between 24/07/2013 and 27/07/2013

MG Midget and Sprite Technical index

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