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MG Midget and Sprite Technical - Stop that body roll

Here is a picture of me entering the Chicane on the Grand Prix circuit at Castle Donington at a recent MGs on Track event. While my car held the road very well (no evidence of loss of grip) the amount of body roll was more than I expecting (to the extent that the body touched the tyre side wall and removed the 'TOYO' name off the sidewall!).

What is the best way of reducing that body-roll or should I just live with it? Stiffer front springs, lowering the car, harder dampers, thicker anti-roll bar at front all come to mind or is it something else. The car currently has an 11/16th anti-roll bar, uprated front springs (380 lbs if I recollect correctly), standard shocks at front and spax at rear. I also have a panhard rod at the rear but I was wondering if that actually made matters worse. Bearing in mind that I will continue to use the car on the road and don't want the suspension so hard it shakes out the fillings from my teeth, what is the best route to take. Thanks, Chris.


Chris H (1970 Midget 1275)

Chris,

The body roll doesn't look that bad I've seen far worse. Also you should get out of your head the notion of using dampers for stiffening the suspension in that way as its not their job and the effect in transient as it will only delay the car achieving full roll.
David Billington

Go round corners more slowly.

I'll get my coat.
Gary & Gaps

Gary - I found I was too busy watching in front and in my mirrors to look at my speed much, although I did glance down once and saw an indicated 85 mph (in 3rd gear!!!) on the approach to the chicane so that is probably what I'm doing here.

Dave - thanks for your comment, which is food for thought. I had no complaints about the way the car handled apart from the rubbing on the tyre - but there are other ways to deal with that (stretch the wheel arch a bit, go back to slightly narrower tyres etc.). You are right about dampers though and I don'y know why I mentioned them as I know they only have a short-term effect and I believe that soft at the rear [sic] is best for midgets in any case.

Chris
Chris H (1970 Midget 1275)

go round the other way to even up tyre wear
N Atkins

I find the easist way to avoid "body rolls" is to avoid the morning donuts....hahaha

One thing to keep in mind is how much wieght is seating in the drivers seat.... Id love to see a photo of taking that same turn with the driver in the passanger seat... Aka, the correct drivers seat USA..... I bet you would have a differant looking photo


I saw an interesting artical that may be intresting


Instead of the anti roll bar under the frame rail it was on top of the frame rails and was similaer in appearance to the adco bar that uses the chevy s 10 sway bar links....it looked like give more response....the bar wedged up next to the rad upright supports...on the frame rails

Prop
Prop

sit on the other side.
Rob Armstrong

It appears that the rear is higher than the front and I assume you are off the brakes at this point as you are starting to turn in. I'd think a rear sway bar would help keep the rear more level and that would inturn keep the front more level as well.
As for the panhard rod, it depends on the mounting. If it's low enough it should lower your roll center a bit.
B Young

Prop may be correct that the weight of the driver has an effect. I don't have any pictures of me taking a right-hand bend on my own for comparison - only me an my instructor (see attached). There is still a quite a bit of body roll but not as much (but then he is lighter than me!).



Chris H (1970 Midget 1275)

Re the rear being higher than the front, I don't think that is the case. Here I am at full chat on the pit straight and the car looks level to me.


Chris H (1970 Midget 1275)

Hi Chris

I think that Bill Young meant that in your cornering image the front appeared to be more level than the extremely pitching rear.

I agree with him that the rear of the car is pitching far more than the front however I do not agree with the solution described by him

When I was taught about dynamics and how to make a car handle I was always taught that to cure problems at the rear you should modify the front and to cure problems at the front then modify the rear. Sounds he wrong thing to do doesn't it, but I have found it always to be the case.

So my solution to your "slight" problem would be to fit a stiffer bar at the front. This will hopefully keep the rear inside wheel a little lower. :)
Robert (Bob) Midget Turbo

is it any lower than standard? You mention harder springs - are they shorter? If not then lowering the whole thing a bit would help, as would spacers on the front to make the front a bit wider and lower the roll centre. Made quite a difference to the body roll on mine, I made the front track 10mm wider. And that's quite cheap...
Rob Armstrong

I fitted up-rated front springs. They were around 1.5 inches shorter than standard but they did not result in a lower stance (presumably because they are stiffer). Otherwise the car is not lowered.
Chris H (1970 Midget 1275)

Please dont take my previous response as a mean spirited flipant remark about someones weight... That wasnt my intent.

I wanted to point out that there is a weight distribution differance from an occupied seat and a empty seat

Im sorry for any offence

Prop

Prop

After some study of the photos... I wonder if some ladder bars wouldnt help... Id imagine the leaf spring is flexing more on one side then the other, thus making the axle move fore and aft on each side... With the ladder bars it will force the axle to be perfectly perpendiculare to the car and id think force the car to ride more level... But im just guessing.... I cant back up my thinking with fact.

this is an addition to the pan hard rod

Prop
Prop

Chris

Looks fine to me - don't mess with it if you like how it handles... :)

Regards

James
James B

Robert understood my point, but I have to agree with him after his post that more front anti roll bar would be the way to go. You could go up to a 3/4" or even a 7/8" front bar and still not have too much harshness in the ride quality. My car also sits level, but displays the same rear high attitude as yours when under hard turns such as at an autocross and that's with a similar sized front bar and a 1/2" rear bar. I will definitely enlarge the front bar if I continue to run track days and autocross events. The rear of my car gets so high that I have lifted the inside rear tire and lost traction at times on a tight autocross track. Might be a good project for this winter, install that limited slip diff I have in the cabinet and put in a 7/8" front bar. I'll add that to my list.


B Young

One thing at a time. IMO lower the front and have another track test; inexpensive and easy to reverse. A
Anthony Cutler

How do you determine what size front anti sway bar to use

Im going to be ordering a new ADCO sway bar this week end but stuck trying to figure out what size to purchase... 3/4 or 7/8 inch

Thanks

Prop
Prop

The problem with rear bars on a live axle is that they cause weight transfer at the rear without any corresponding geometry gain. So the outside rear tyre gets more heavily loaded and will break away earlier. And the action of the arb also causes the inside rear wheel to lift.

The car does sit flatter with a rear bar of course. However, because it sits flatter there is a geometry gaint at the front - the outside front wheel is now at less of a lean outwards and so has more grip than before.

So overall the front has more grip, the rear has less, and the car loses the back end at the limit.
Paul Walbran

Thanks for all the comments and plenty of 'food for thought therein'.

One quick question - is it OK to have the front lower than the rear? Or is the aim always to keep the car level?

Chris
Chris H (1970 Midget 1275)

It is OK to have the car sitting in any plane that works the best... I have set up Midgets (on cornerweight pads) with perfect weight distribution that looked like they were sitting down on one wheel...
James Bilsland

>>is it OK to have the front lower than the rear? Or is the aim always to keep the car level?

Recommended to run the front lower than rear: reduces front cofg and roll, gives a little more -ve camber to front wheels, and reduces air-flow under car to give lower drag and additional stability at speed.

A
Anthony Cutler

Thanks Anthony - that explains your earlier suggestion. I'll give that a go. as you say, it is easy, reversible and does not cost much!

Chris
Chris H (1970 Midget 1275)

LOL - that looks straight as a die to me - take a look at mine :P!!!!!!


rachmacb

Rach, your not trying hard enough, looks like your driving to visit Asda or some thing like that.
Get one frontwheel of the ground woman!!!
LOL!!


For the record: ive havent achieved that either as far as I know as ive not seen it on film or photo and surly cant see it happening while Im in the car myself...
I was very close on Prescot but very close doesnt count.
Some day its going to be on photo... some day. :)


Paul Walbrans warning has to be recond with but despite that im very pleased with my Frontline RTL on my rearaxle.
I have it in combination with 400lbs lowered frontsprings, 11/16 rolbar and poly bushes front and rear.
Im not even near the status of an experienced amateur-racer but really enjoyed the full kit on my car when I was on the Ring(NortSchleife-Germany) a couple weeks ago.
Excelent roadhandling of the car and power of the K!!!
Ive learnt on the Ring that my car is more capable then its owner.
Practice, practice and more practice.
Arie de Best

Lol there is a photo of me airborne ... I just hid it well :)
rachmacb

"Lol there is a photo of me airborne ..."


Rach, does it have any thing to do with a midget?
LOL!!
Arie de Best

Needing all that practice Arie I suppose you'll just have to go back to the Ring for more. What a sacrifice!

I was referring to antirollbars, the RTL doesn't transfer any weight, it's providing better location.
Paul Walbran

"I suppose you'll just have to go back to the Ring for more. What a sacrifice!"

I know Paul, its one hell of a sacrifice... its so boring... :)



Arie de Best

Chris,

Taking a road car on the track is always going to make it look and feel horrible as you obviously pushing the car to limits not normally explored.

Without turing into it a race car you will always get out of shape on a track at speed.

Just keep changing one thing at a time as per the previous comments - wider, lower, stiffer, more level etc

Rgds

Nigel


Nigel Pratt

This thread was discussed between 19/10/2011 and 21/10/2011

MG Midget and Sprite Technical index

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