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MG Midget and Sprite Technical - rear sway bar question

I saw a thread recently discussing rear sway bars. I think someone mentioned that they weren't necessary for street cars and tended to increase oversteer. It may have been David (I can't remember where I read it) Lieb who I think prefers a Panhard rod, but he also autocrosses his car. I don't understand all the nuances of suspension physics, but thought the swaybar was supposed to take some of the force from the outside wheel and transfer it to the inside wheel, which would improve traction on both wheels, keeping the rear from sliding out resulting in oversteer. That said, I installed a rear sway bar (as well as front) a long time ago when I was sutocrossing my midget, but don't plan on doing that anymore. I'm now more into trying to maintain it and driving it to LBC gatherings. So, my question is, would there be any affect on the ride if I remove it? Would it be more compliant and have a better ride on some secondary roads that are not always so smooth?
Jack Orkin

A sway bar transfers weight from one side to the other when the car leans in a corner. On the loaded side (the outside) the suspension is compressed - the wheel is forced into the arch. So the bar transfers some of this movement to the other side - so this wheel also moves up into its arch too (how much, depends on the strength of the bar). In other words, it puts less weight down onto the road which means less grip.

And the gain in grip on the outside tyre due to extra load on it is less than the weight transfered.

So overall, grip is lost.

Panhard rods are not used to lessen roll - they are there to reduce sideways movement of body on the leaf springs during hard cornering; essential for the press-on driver.

Taking the bar off the rear will make the rear more compliant.

A
Anthony Cutler

I agree with Anthony. The bars work fine with independent suspension because the reduced roll they give results in a more favourable wheel camber, which increases grip. With the right combination, you come out ahead overall.

However, with a live axle, there is no change in wheel camber with body roll, so an antirollbar/sway bar is all losses and no gains. I've lost count of the number of people who didn't believe me, fitted a rear bar to a B or Midget, spun out on the track and promptly removed it admitting their mistake.

I've described it more fully at
http://www.mgparts.co.nz/performance2.html
Paul Walbran

I think (perhaps) that Autocrossers like their cars to slide easily, that's why they fit rear bars.

(maybe!)

AndyB
a borris

Thanks for all your input. While it still seems somewhat counter-intuitive to me, it is starting to make a little sense! The article Paul mentioned was helpful. Since I'm less a boy racer now and more of a gentleman cruiser, I think I will at least disconnect the links and see how it rides and if I like it, will just remove the whole thing. Will save 5 pounds or so anyway!

Jack Orkin

In my case, a 3/4" front ARB in conjunction with R-compound race tires and my Phantom Grip "LSD" created a situation wherein I was routinely getting two tires off the ground in a skidpad at the autocross. Adding a loosely-coupled rear ARB keeps that from happening at the expense of the handling. Nonetheless, I prefer NOT to find out how effective my rollover bar is.
David "keepin the greasy side down" Lieb
David Lieb

I have just fitted Frontlines Rear Traction Link to my 1275, its not cheap, but well worth it if you have the budget. Straight line stability is much improved, and it handles bumps, (of which around here there are many),better. Went into a corner yesterday faster than I normally do, and it just went round as though on rails.
Normal disclaimer, I have nothing to do with this company. (unfortunately)

There is an issue with the Hand Brake linkage, but it can be resolved.

Dave


Dave Barrow

Dave,
what will you do to resolve the handbrake linkage? I've been told to change to a 1500 set up.
Brad
Brad (Sprite IV 1380)

Brad
After a morning of playing with hand brake adjustments, I managed to get the rods clear of the RTL bracket, but still had contact between the right hand RTL rod, and the RH hand brake link. I tried the link above and below the RTL, but it still would not clear, after a nights thought, I fitted the link above the RTL rod, and then removed the hand brake lever arm from the hub, and heated it up, and bent it up about 30o. Everything clears now, and the hand brake still works ok. See picture.

Dave


Dave Barrow

Thanks Dave,
i'll give that a go,
cheers
Brad
Brad (Sprite IV 1380)

Brad
I should have added that you need to put a slight twist in the lever arm as you bend it, to maintain alignment with the headed pin that attaches the link.
I am also assuming that you have the old style adjustable hand brake links, not the new fixed length ones. With the old style you can adjust the fork end angle to fit the bend in the lever arm. Not sure what you could do with the fixed length one, bite the bullet and put a twist in it I guess.

Dave
Dave Barrow

'old style' ?
the original handbrake link rods were never adjustable, on any model of Spridget. IIRC Moss were selling adjustable ones a few years ago, presumably to avoid making separate shorter ones for wire wheel axles.
David (davidDOTsmithAT stonesDOTcom)

Dave,
i made some S/S tubular adjustable rods years ago before Moss was selling them, it helps a lot with reducing the bending on the long rod & gives a firmer handbrake.
Brad (Sprite IV 1380)

Brad how would the long rod bend since it is only ever sitting free, or under tension? When the handbrake lever is released it is the springs on the shoes that return the rods to a resting position.
David (davidDOTsmithAT stonesDOTcom)

David,
your perfectly correct, i stand corrected it was early o'clock when i wrote that, but making the longer rod adjustable allows handbrake to be adjusted better, as you can have both rods at the same tension, so both brakes have the same pull on the levers.

Tommorrow i'm not going to post until i've had three cups of coffee!
cheers
Brad
Brad (Sprite IV 1380)

David
I only thought the adjustable rods were old style, as that was what was fitted when I bought my Midget, and they looked original. Also when I snapped the LH rod trying to adjust it, I went to moss for a new one, and they said they only had fixed length, and they had not seen adjustable ones for some time. So I don,t know, but I will bow to greater knowledge.

Dave
Dave Barrow

This thread was discussed between 27/05/2009 and 01/06/2009

MG Midget and Sprite Technical index

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