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MG Midget and Sprite Technical - Hub to Hub measurements

I have just replaced my rear spring hangers, inner and outer bulk panels, floor panel...Im converting a SWA to a RWA with the help of a crashed shell and just out of interest my nearside measurement is now 8mm shorter than my offside....

This got me wondering ..would you mind measuring your midgets from hub to hub and posting the answers, Im worried 8mm is way too much.

Many many thanks

Jon
J WHITE

Jon,

I can't help with that but it did remind of an incident I was told of at the local college auto shop. A Renault 4, IIRC, was on the dozer and the operator had checked the distance and found the wheel base shorter on one side and corrected it, the car was found to handling strangely after that and the problem was eventually determined to be the wheelbase correction as Renault intentionally design it with a 25mm IIRC difference so the rear torsion bars could pass each other across the car. It got bent back to what it should be and was fine after, although I wonder what stretched.

Did the sill arrive OK?.
David Billington

mmmm....I must admit im not sure whether it drives straight and true etc as its not quite ready for a trip??!!!

I got a note from Royal Mail today saying something was delivered...Ill pick it up at 7am...fingers crossed it's your sill.

Jon

PS cheque book has been hiding - found it and it will be in the post tomorrow....without fail.

Huge thanks
J WHITE

I seem to recall that the Renault 19 had a difference of 1/2" from one side to the other.
Dave O'Neill 2

Jon,

Not meaning to hassle you, just asking if it arrived OK. I considered it well wrapped, just wanted to make sure the PO had not tried to fold it up to fit through your letter box.
David Billington

I know that unequal wheelbase is not uncommon in some car designs. But I struggle to see how this would work in relation to mountings of the rear axle on a solid rear axle car. Either your rear axle is at right angles to the main axis of the car or it is not. If it isn't then the wheel alignment must be out.

Does it matter? Depends what degree of tollerance was allowed in the original design.

Guy
Guy Weller

Guy,

In the case of a solid rear axle car like the spridget the rear axle would have to be perpendicular to the axis of the car fairly closely or it would crab, saying that IIRC minis were known for that from the factory at times and I have seen a few examples on the road which seemed to quite obviously exhibit the behaviour.

Another interesting aspect of this line of thought, I was talking to an old racer who mentioned that one series he was involved in allowed welded additions to strengthen the axle but didn't mention where. Most welded them to strengthen the axle in bending but he added them at the front so the weld distortion caused slight toe in and helped high speed stability.
David Billington

David,
That is what I was meaning. Axle on a solid axle car really needs to by perpendicular to the axis of the car, but in any design there will be some degree of tolerance. I doubt it would be as much as 8mm though!

Of course the mini is not a solid axle car. You could, in theory, use unequal length rear swing arms and have differing wheelbases whilst still having both wheels running parallel to the car axis (I do know this wasn't the design) Crabbing in minis is not uncommon when the whole subframe is askew or if the whole body shell is bent. The latter can happen on dark wet nights in Wales when side-swiping the side of a cow shed at speed.

Guy
Guy Weller

For what its worth and adding my to cents worth

on my 71 midget swa...when I converted to my hurrican wheels, the USA passanger side was closer to the wheel by about 3/8 to a 1/2 inch then on the USA driver side

it sounds like your car and mine are a match
Prop

Great answers- I'll stop panicing and get on with welding it up...I should start a rebuild thread so you can all offer me tips!!!!

Dave, - I dont feel like you are hassling me one bit - Im off to the PO now to see if the parcel is your sill or my new ebay purchase...overalls and gloves??!!

Jon
J WHITE

Jon,
If possible do a 'drop test' from each wheel centre onto the floor, mark the spot with chalk.
Measure the diagonals i.e. FNS to ROS and vice versa FOS to RNS, the measurements should be the same which tells you the axle locations are square.

(Measuring the wheelbase, alone, on each side does not necessarily mean the axle alignement is correct but it is a consideration.)

Peter

PJ HOBSON

David may I say you are a fantastic engineer but handling engineer I may think you are lacking..
If you don't mind me saying.... :) only joking mate!

In most race cars getting the damn things to turn round corners is the main problem and crutial to that is to get the car to turn in. (must admit this is harder on front wheeled drive cars than our Spridgets).

So it is better sometimes to have toe out at the rear so that as the car turns the outside rear loads up and rear steers the car better around the corner.

Equally if the car was a bit oversteery to start with then as you correctly state that a bit of toe in can help to significantly reduce oversteer.

I suppose I mean to say straight line high speed stability is of limited benefit when compared to cornering assisitance.

As you state though probably if I were racing a Spridget today I would be welding the front of the axle casing and engoying less oversteer. I suppose we ought to ask a current racer if they believe their Spridget is oversteering or understeering?

I also used to autotest a Mini, marvelous machine. As I am sure you are aware autotesting benefits from a car with a very oversteering nature, bit difficult in a front wheeled drive Mini until you introduce a good bit of toe out, offset washers on the rear radius arms was the key!! LOVELY
Robert (Bob) Midget Turbo

Robert,

No problem, my handling experience is dealing with my cars and that of a few others and judged somewhat by my ar*e, and hopefully not talking out of it, analysis of its input afterwards as well as other inputs such as steering feedback etc, and physics. Largely road and hillclimb use.

IIRC the car in question may have been a Ford Falcon, the racer is a time served member of the BRDC and has raced internationally with success, more than I hope to do. One item I heard mentioned was that BRDC members are separated into 2 groups, those that race and honorary, the honorary members haven't pinned their balls to the dash and raced themselves. A separation but it doesn't detract from those that haven't raced but have been honoured for helping enable racing.
David Billington

Bob,
I purchased the ex Tommy Warburton 1293 'S' around '68ish, 93 at the wheels, Dunlop Green spots, ARB on the back and absolute magic at knocking off E types.Only problem was severe wear on rear radius arm set up, lots of slack.I asked why they did'nt fix it, answer was rear tyre was already halfway round corner when you turn front wheel into corner! It was lethal on the road so I fixed it, but, it held climb records at Harewood,Olivers Mount and LR at Oulton circa '65.
Memories! Memories!
Peter
PJ HOBSON

This thread was discussed between 25/11/2009 and 27/11/2009

MG Midget and Sprite Technical index

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