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MG Midget and Sprite Technical - Check your tracking !

OK, i'm an idiot, i admit it...
Fitted my new ARB a month or so ago and very happy with the results during the 20 or so miles i did with it. Been away for a month and back to drive the car for a 150ish mile trip during which the steering got heavier and heavier...

Looked at the tyres and found i had managed to wear out the passenger side almost completely, was worried i wouldnt make it home !

Got the tracking checked and found 17 degs toe-in...
Should have checked/adjusted after fitting the ARB...idiot.

Still now its sorted out and some new Goodyear tyres on the front its more fun than ever...


Andy Phillips (frankenfrog)

How did fitting an ARB alter your tracking?
Dave O'Neill 2

I was gonna ask the same question Dave. :)
Arie

I dont know,.. i wouldnt have thought it would have an effect which is why i didnt get it checked.

Only one thing i can think of is that i had to put thicker lowering spacers in the passenger side than the driver side to get the car to sit level, but when i did that i had the tracking set properly..

or... thinking a little more... is it because of the angle of the suspension as per this photo ? i posted this before a few months ago ......



Andy Phillips (frankenfrog)

So it was the camber on one side, not the tracking?
Lawrence Slater

According to the laser alignment machine there is 2 degrees positive camber on passenger side and 0.5 on driver side.
The same machine showed 17 degs toe in which has now been adjusted to 0 degs.

If you look closely at the tyre you can see the feathering of the tread..
Andy Phillips (frankenfrog)

It looks like you have a spacer between the steering arm and the stub axle that was fitted for the purposes of fitting a big brake (disc) conversion kit. If so was the tracking re-done afterwards?
Daniel Stapleton

Adding the spacer would make it toe-out, wouldn't it?
Dave O'Neill 2

Tyres wearing on the INSIDE of the tread suggest it was toe-ed out, not toe-ed in. Which fits with Dave's comment about the effect of the spacer.
Guy W

This link to a well repected local tuning company:

http://www.grahamhathawayracing.com/html/wheel_align.html

states toe out causes wear to the inside edge of the tread [which Andy is describing] where as toe in causes wear to the outer edge of the tread
Doug Plumb

Umm, that's what I just said, Doug!
Guy W

Let me be the 1st to say... I think its toed out


Haha

Prop
Prop and the Blackhole Midget

Guy, I think you and Doug were posting at the same time.
Dave O'Neill 2

Gold star to Daniel for spotting the spacers behind the steering arm, but i dont think they are cause of the issue, i put them on about 3 years ago as i needed clearance to fit my alloy wheels.
Doug, -- good link , bookmarked.

Wear is definately on the outside of the tyre see pic with it still on the car.
There was excessive wear on the other drivers side tyre also, but not as bad as on the passenger side.
I think the toe-in and the positive camber combined on the passenger side made it conditions worse for that tyre.

Strange that the passenger side is the one with the larger lowering spacers and that is the one with the more positive camber.. I thought the lowering blocks were supposed to give you more negative camber ?


Andy Phillips (frankenfrog)

Just a thought about the steering arm spacers....(3mm thick BTW)
By putting on the spacers then adjusting the rod ends to compensate you are actually making the arm from the rack shorter.

As the wheel moves up and down as it is supposed to do then the suspension components move in relation to fixed pivot points, these are the shaft through the lever arm and the pins through the bottom A-arm.

The length of the a-arms and lever arm is fixed and unchanged, but now the steering arm is effectively shorter and therefore moving in a slightly smaller arc than it should by design.

With a shorter steering arm then the wheel would gain toe-in when ever suspension is compressed.

This means that if you set the tracking with no one in the car as soon as you and a passenger get in and add extra weight then the tracking will change....?

see pic below originally posted by Norm ...


Andy Phillips (frankenfrog)

This thread was discussed between 20/04/2015 and 21/04/2015

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