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MG Midget and Sprite Technical - Allan Staniforth made me wonder...

Has anybody fitted softer rear springs and an a rear anti-roll bar to a Spridget and did it make the car ride and handle better ?
Malc Gilliver

Rear springs are fairly soft, already.

A35s had a rear ARB as standard. When I raced mine, it would lift the inside wheel in corners, so I removed it.
Dave O'Neill 2

i used to have a rear ARB on my street Frog eye and it would over steer. Took it off and now it goes like on rails, exactly where I want it to go. Of course, I do have 6 inch wheels with 185/70 R tires and a 7/8" front ARB and the stock springs but I do like how it handles with this setup.
Martin Washington

Malc

MG midget Challenge racers may have tried this in the Modified Class.

Mike
M Wood

I've fitted softer springs on the back of my frogeye, one longer leaf removed. I later added a rear ARB to counter excessive understeer in tight turns. Front springs are standard with a 5/8" front ARB. Front and rear are fibreglass. The rear is also modified for more travel in bump and droop and the use of the later 1/2 elliptic softer bump stops. Works for me.
David Billington

How did Alan Staniforth make you think about a rear anti-roll bar? I wasn't aware he wrote about live axle cars.
Daniel Stapleton

Daniel,

I had expected to have a foot operation and planned to be out of action for a week or so, so I read the whole book.

While you are right about Allan focusing on real space frame independent suspension cars, I found myself being led into lowering the roll centre of a car - and then choosing road springs and dampers as soft as possible to literally just take up the undulations of the road, then fitting an anti-roll bar to do all the work with regards to cornering.

So rather than just blast in and soften my suspension and add an anti-roll bar, I thought I'd ask.

From the comments received (Dave and Martin - thanks both)- it is clear that taking a normally sprung car and adding an rear A/R I will have problems, but if I can soften the rear springs by moving the shorter lower leaves up unto the top of the rear springs then adding a rear A/R I should land up with a compliant ride with good performance in the corners. ( David - thanks for the info) Next job is then fabricate a Mumford linkage to pull the roll centre down and further tweak the front / rear A/R bars.

Malc
Malc Gilliver

I don't see a need for a rear anti-roll bar on a live axle car and cleverer people than myself and experts would agree with me.

Lowering the roll centre does make a big difference and my experience is that this is especially so if the springs are fairly stiff. You can lower the roll centre with a Panhard rod for a lot less money and aggro than a Mumford linkage kit and this is the principle reason why the Panhard rod is favoured by myself over a Watts linkage. Again, it would take a cleverer person than myself to expound the late Arthur Mallock's reasons that would support that statement.

There appears to be very little in books about this, but one day a revison of one book I am familiar with will have a lot more detail than the current edition does.
Daniel Stapleton

The problem I see with providing some additional mechanism to control the RC and maintaining the standard springs is that you have a RC dictated by the springs and a RC dictated by the new linkage, the more you move the 2 RC apart the more they fight each other resulting in a stiffening of the suspension in roll. The springs while soft in bending due to suspension movement are still stiffest in the lateral direction so an additional axle location trying to bend them sideways will meet resistance. You either need to go to coil overs for no location provided by the springs or an arrangement where the leaf springs can float laterally somewhat and allow the new axle location, Mumford, Panhard, or Watts, to do its job unhindered.
David Billington

This thread was discussed between 14/04/2015 and 16/04/2015

MG Midget and Sprite Technical index

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