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MG Midget and Sprite Technical - Tracking - where to measure from?

Morning all

Where do you measure from to set the tracking? I know it's between 0 and 1/8 of an inch (3ish mm) toe in, but surely that depends on where it's measured?

Would it not be more sensible to state an angle, then it doesn't matter where it's measured (though it'd be very small)

Is it from the edges of the sidewall? wheel rim? centre of the tread?

Is where it's supposed to be measured from different where you lot measure from? or is it the same?

(I've just put some new TREs on, and have some lowering to do!)

Cheers for your views!

Rob
Rob Armstrong

Rob,
I set mine by measuring from the wheel rim edge, at the 9 and 3 o'clock positions. i.e. height of the axle. But to do this you need to use some sort of device that allows for the sump and chassis rails being in the way. I use a home-made cranked pair of measuring sticks.

But someone recently mentioned this firm http://www.trackace.co.uk/Trackace.html

Looks like a really good bit of kit and I was very sorely tempted!
Guy W

I use an long straight ally bar, resting gently/horizontally along the hub centre-line to rear of car... to toe in a fraction, the bar needs to diverge along the car body very slightly.

I've used this on the midget, on the Honda ATR (I must have spent 500+ pounds over 6 year on tracking this car front and rear until I finally nailed it at home using the ally bar), and on current SLK (was runnning parallel at front causing wear on outer edges of both front tyres; handling sharper after adjustment.

A
Anthony Cutler

Yes its the difference between 9 oclock and 3 oclock on the inside of the Wheel rim.


I recently borrowed a friends gunson trackrite - and despite my sceptisicm... it was fantastic to use and very accurate. Worth a thought.
C L Carter

It's expensive, but the Gunson Trackrite is superb. You don't need to know the correct setting. You simply adjust the track until the gauge shows no sideways deflection when you drive over it. I have used mine on several cars with great success, including the rear wheels on my MGB with IRS.
Mike Howlett

It is measured from the center (more or less) of the tyre tread. To be precise, You jack the car up, chalk the tread, spin the wheel to scribe an accurate line in the chalk, lower the car, and roll back and forth a bit to settle, then measure between the lines at hub height front and rear.

It was formerly not specified as an angle because it is extremely difficult to measure such, but any idiot can measure with a string or a stick - well most. Now you get angles and need $100,000 worth of machinery, or enough math ability to calculate the simple 1/8".

FRM
FR Millmore

Thanks everyone :)

Dad has a trackrite, I admit to not using it because I couldn't see how it would be any good, but I might now give that a go!

Middle of the tread is easy enough, I originally set it with a long piece of wood with vertical ends, measuring at hub height on the sidewalls. I might compare this with tread middle and wheel rim measurements (and Ant's system if I can find a nice bar) and see how different they all are.

Even so, I might just get it so it feels right, I had it very wrong in both directions before and boy can you tell. With different tyres, wheels and ride height perhaps the 1/8 of an inch measurement is a bit vague anyway...



Rob Armstrong

Middle of the tread to middle of the tread, and rim to rim, give two different results, if using the same 0-1/8" spec.

I've always understood the 0-1/8" measurement, to be specified as being rim to rim. Is it in fact centre of tyre to centre of tyre?

Lawrence Slater

Rob,
there was a recent thread that IIRC had a useful diagram/photo(?) and loads of info of different methods

keep your eye on the TRE boots, rubbish rubber meets recent changes to MoT

I managed to keep my tracking, on only changing TREs, by very careful noting of the postion of the old ones and check old and new were the same size

I might get around to raising mine tonight, subject to weather and motivation
Nigel Atkins

Another vote for the Trackrite.

Dave
Dave Barrow

Tread surface to tread surface, and radial tyres generally want much less toe than bias did.
I was told by an old time very picky front end man years ago to set toe at "just" in or out as specified for radials. He had state of the art equipment, transits, plus sticks, strings and levels, and set them at 1/32 for most applications with all good parts in the suspension - and that is pretty much what I've done ever since.

FRM
FR Millmore

This whole thing is highly tyre & wheel dependent. As it would be 1/8" on the tread surface (or rim) of a 145-80-13 on a rostyle.

is it the same toe in settings all through midget life? even with the higher 1500?

Alas for the quest for accuracy. lol. I shouldn't think so hard about things :p
Rob Armstrong

Rob
The owners handbook for my 1500 states that tracking should be parallel to 1/8th Toe in or if you prefer 0 - 3.2mm

Alan
A Pritchett

When it is wrong you can see the tyre wear.
When it is right you can feel the difference!

1/8" is what is specified, but I set mine with slightly more. You can then feel the car turn in properly and it travels much more precisely in a straight line with little or no steering input needed. But it does depend also on the wheel offset, and tyres, pressures etc. Best to set to factory, and then experiment from there if you want.
Guy W

The whole point of track adjustment is to try and ensure that when in motion the wheel is travelling dead straight ahead. If it isn't, the tyre is being scrubbed because the wheel is holding it at an angle to the direction of travel (be it ever so small). I know it is a bit simplistic, but a rear wheel drive car tends to push the front wheels outwards as it moves, so you usually toe the wheels in a little.

The Trackrite simply measures if there is any sideways scrub on the tyre as it rolls over the gauge and displays the scrub with a pointer which tells you whether to adjust the toe inwards or outwards. It is a brilliant idea and is really simple to use. It must be used on level ground, and the gauge needs to be kept clean and free to move. I usually take two or three readings on both wheels to make sure the results are consistent. Then a quick adjustment, check again and it is done.
Mike Howlett

Wait for the nay sayers but after I replaced the rack gaiters, I nipped down to my local National Tyres Centre in Burton on Trent. The very friendly guy in his 40's checked the tracking and exclaimed "bang on mate!". Cost me nothing.
Pete Ottewell

"When it is wrong you can see the tyre wear.
When it is right you can feel the difference!"

That's my approach too Guy, starting at around 1/8th toe in max, measured from the inside of the rims, because I thought that was the specified measuring point.

But others say the centre of the tread on the tyres. Haynes doesn't say which.

1/8th at the rim, will be more than that at the tread centre. So where is the 0-1/8th toe in stated as being accurate? Rim or tread?

My cranked tool works well, but the trackrite sounds good too.
Lawrence Slater

You could work out what the tread measurement would be from the rim measurement = about 1.5x = too much. At that point I can soon see and feel the wear, and the fuel mileage will suck, and the actual handling will drop off, because the tyres are already sliding. It is a very controllable situation though, so good for amateurs or the timid.

I stated my practice above, learned from the best alignment man I ever met, and I have searched since he retired 35 years ago. Haven't found anybody to match, but I am in the bushes. I now set them up myself and the car always works better when I'm done.

I now set my own car about dead zero to faintly toe out, as it makes it very lively and responsive - you do have to drive it, not just ride around There is a fundamental fact in that stability is contrary to responsiveness, so you decide - and the difference is within +/- 1/8" for toe with decent tyre wear and fuel economy.

FRM
FR Millmore

Some forty years ago I worked a Bear Alignment machine for an Audi/BMW/VW dealership in Pheonix, Arizona. While various adjustments (toe/camber/caster)were possible, when it came to "toe adjustment" near neutral worked best with radials. One of the customers biggest concerns almost always turned out to be "centering" the steering wheel. This usually done with wedge between the seat and bottom of the steering wheel rim before I started. Loved the BMW 1600/2002, hated the Audi 100.

Larry C.
Larry C '69 Midget

This thread was discussed between 22/08/2012 and 23/08/2012

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