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MG MGB Technical - Toe Adjustment??

What is the recommended Toe alignment for a 78 RB with the decambered(longer) lower arms?
Thanks

Roger
Roger Nagy

I believe the recommendation is that you set it as close as you can to 1/8" and then drive directly to a good alignment shop and find out how easily we can screw up what looks like a simple job. I've tried this a few times - even with an experienced MG mechanic at my side. And I've replaced a lot of prematurely worn tires... 8^(

Allen
Allen

The *standard* toe-in is 1/16" to 3/32", or 1.5 to 2.3mm, FWIW.
Paul Hunt 2

Buy a gunson's Trackrite gauge. Then you don't need to know the toe setting. You simply adjust the track until the wheels run true. It's so clever and is ideal for modified cars.

Mike
Mike Howlett

Where does one find a Gunson's Trackrite gauge in the states?

Thanks

Roger
Roger Nagy

Mike - from what I read the Trakrite simply tells you what the tracking is i.e. how much it is toeing-in or out. You still need to know what to set it to, and keep tweaking the adjustment until the Trakrite shows the required figure.
Paul Hunt 2

Roger There are two main reasons for toe in. One is to allow for the deflection in steering and front suspension deflection in use. The other is to make the wheels roll without scrub caused by the camber angle. " If you project a line through the stub axle it will hit the ground some distance from the side of the car" The wheel tries to turn around this spot and toe in neutralizes this. As you are decambering the front end you don't need the toe for the second reason but I would still leave a little to allow for steering deflection. Set it at the min.tollerance 1/16". The deflection reason is why rear wheel drive cars usually have toe in and front wheel drive tow out. Denis
DENIS H

To answer Paul's query, the Trackrite gauge is a flat plastic thing with a pointer on one side. The top panel slides over the lower panel and as it does so the pointer moves over a scale that reads zero in the centre, and numbers of degrees in each direction.

OK, so you set the pointer to zero, lay the gauge in front of the wheel you want to measure, and drive the car gently over the gauge. The aim of the toe setting, as Denis describes above, is to prevent any tyre scrub. If the wheel is not running absolutely true, the scrubbing twists the gauge, sliding the top panel a little. This twist is translated to degrees by the pointer. Ideally you measure both front wheels and they should read more or less the same.

Then you have to adjust the track rods a little, equal amounts on both sides, and try again, so yes Paul, you do have to adjust and try, adjust and try. You know whether the wheels are toeing in or out - the pointer tells you that, and you also know how large an error there is. In my experience I have got it right on the first or second attempt every time, and I've used it on a variety of cars. You really don't need to know the "correct" toe, because you simply adjust out the scrub.

The car must be on level ground, must be normally loaded, with driver on board, and must be under power and not pushed. Use of the brakes just before the measurement is discouraged. In practice it is dead easy to use, and works really well. Like most Gunson's products it isn't particularly well made, but if you treat it carefully it just what it says on the label.

Mike _ no I don't work for Gunsons!
Mike Howlett

Roger,

I prefer zero toe with this set up.

Paul
Paul

I apologize for my incorrect advice above. My feeble memory had it at 1/16" to 3/16". If that's the way I did it myself, no wonder I had problems! Thanks to Paul2 for correcting me. I've never used the Gunson Trakrite.

Allen
Allen Bachelder

Mike - this does surprise me, but then I have never seen one in use. What also surprises me is that tyre places bother with all that alignment stuff and huge charts of toe values on the walls if they could simply push the car back and fore over a professional version of this device and adjust the track for no scrub. I'm also surprised that the different toe (out rather than in) for front-wheel drive cars therefore has to be because of significantly different camber angles, I've always thought it was because the wheels are trying to pull forwards most of the time and hence trying to toe in whereas with a rear-wheel drive car under braking they are trying to toe out. Out of interest I looked in my Toyota Celica (FWD) Workshop Manual and not only does it quote a toe-*in* figure (2mm if checking, 1mm if adjusting) but it also shows a 'side slip tester' being used quoting a maximum figure of 3mm per metre. However it says if it exceeds this you need to check the toe-in, rather than just saying 'adjust the toe for zero' or whatever. Toe-in for the Celica and MGB are very similar at 1 to 2mm, whereas caster is 1 degree for the Celica and 7 degrees for the MGB, and camber is -10 degrees for the Celica and +1 degree for the MGB both of which are significantly different. FWIW a Metro is all pretty-much zero.
Paul Hunt 2

I've always liked the Trakrite idea as it sets the toe spot on for the car rather than to an estimated manufacturer's figure (or worse a range of figures). I finally invested in one last year after spending money at a tyre place for a "proper job", but finding the inner inch of tread scrubbed off both sides after a few thousand miles. The steering feels more precise and the tyres are looking good. They did make a pro version, but I suspect as a professional you'd risk all sorts of litigation if you set to anything but manufacturer's figures.
Steve Postins

With regard to the "alignment stuff" that garages use, the way they get bashed about and generally abused, I'm amazed they give anything like the correct results. These are usually precision optical devices, but I've seen the "technicians" (read primates) chuck them down on the floor when finished. I'll stick with my Trackrite.

Mike
Mike Howlett

This thread was discussed between 17/02/2006 and 24/02/2006

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