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MG MGB Technical - Gunson Trakrite

Anyone with experience of this? Having trouble finding someone locally to do tracking with wire wheels (spinner in the way). I might be able to get one for £50, tracking is £27, I have three cars ...
PaulH Solihull

Paul,

I've had one of these for the better part of 20 years and found it worth its weight in gold. I first got it because I no matter how often I had my Sierra tracked the tyres always wore unevenly. Since then I've used it for for several more Fords, Nissans, and of course the MG. The first attempt might take a while, but once you have the method off pat you won't look back.

Miles
Miles Banister

I have one and it is excellent, providing you use it exactly as instructed, especially the ground must be completely flat and level. I normally take several readings of both wheels to make sure I have a true indication.

Keep it clean and make sure the slide can move freely. The construction of the thing is a bit cheap, but if you look after it, there should be no problem.

The idea behind it is brilliant - I wish I was that clever. I've used it on the front and rear wheels of my BGT (Hoyle IRS needs the rear to be tracked), and on my modern cars and several other cars as well. You don't need to know what the toe should be, you simply adjust until the wheels run straight and true. The guy (or gal) who thought of it is a genius.
Mike Howlett

I have always used the 'string' method, with very good results.
Dave O'Neill 2

I use one, and it works well, even on the kid's kerb magnets.
Has anyone used the DIY balancing kit?
c cummins

Since there seem to be other Trakrite enthusiasts out there, I thought it might be of interest to share my "non-standard" method of use.

The Trakrite shows total deflection whichever road wheel is used to take the measurement. This point was brought home to me when I first used it because I measured both wheels and adjusted each one. Unsurprisingly (having read the instructions properly) this had no effect on the tracking, but the more I adjusted it the more the steering wheel went off centre.

So now I hold the steering wheel dead straight and measure the deflection at both road wheels. That tells me the deflection for each wheel instead of the total. Then I know whether to adjust one wheel or both. Having done what we might consider the coarse adjustment, I then do the fine adjustment as standard and if any tweak is necessary it is so small that the steering wheel centralisation doesn't suffer. The same method can be used to centralise a steering wheel if it is already off centre.
Miles Banister

Thanks - all good stuff. I've just changed the track-rod ends, old and new were different lengths so counting the turns and reference marks were no use. I backed off the lock-nuts as close as I could get to the difference in length (the new ones being longer) then screwed the new ones up to that, but wasn't happy it was close enough to drive with so I made up a bar and pointers to use the method shown in my old Toyota Celica workshop manual, which showed my ball-park at about 4mm too much, which I then adjusted out. Good job I did as I may have to drive 20 miles or so to find a tyre place that can do it.

I've been thinking about the effects of toe. The MGB has to toe-in 1.5 to 2.3mm. With one wheel on the trackrite, free to move sideways relative to the *ground*, won't the effect of the toe of the wheel on the ground cause the front of the car to move sideways, effectively steering it, as the car goes back and fore? So doesn't that mean the only time the Trakrite is going to show zero scrub is when both wheels are parallel? I.e. zero toe which is incorrect?
PaulH Solihull

That's twice I've done an edit now that didn't work.

Scrub the second para, what I wanted to change it to is that the Trakrite instructions do say to check both wheels, but only to confirm the result, different results indicating other problems with suspension angles, tyre pressures or floor surface. It doesn't say whether to adjust one or both track-rods, but it has to be both, and either both screwed in or both screwed out, otherwise the steering wheel *will* change angle. I suspect Miles was screwing one out and one in. To just change the steering wheel angle, when the tracking is correct, you don't need the Trakrite anyway, just be sure to trak-rods by the same amount but this time in *opposite* directions i.e. one in and one out, which can be judged from how far the lock-nuts turn if these are kept clear of the ends of the track-rods.

Test edit.
PaulH Solihull

Huh! That edit worked!
PaulH Solihull

Paul,

You're quite right about what I was doing wrong the first time, and that the Trakrite only shows zero when there's no toe at all. But my understanding is that that's the point. When garages set track they do it with the car stationary and the toe-in, for a rear wheel drive car, is to allow for the splaying effect when the car is in motion. For a front wheel drive car they'd set toe-out because as the drive comes on the wheels tighten up. The Trakrite measures deflection while in motion and if that's zero then all's well. I suspect that if it was set by Trakrite and measured by a garage then they'd find a toe-in within spec. The first time I did an Escort (my father's) with it he didn't quite trust me and took it to be checked afterwards - the garage told him it was dead on spec by their measurement. What I do know is that after using the Trakrite I never get any uneven tyre wear.

Miles.
Miles Banister

"the Trakrite only shows zero when there's no toe at all"

Ah no that's not correct, the Trakrite shows zero when there is no *scuffing*, or side-slip, which is achieved by getting the correct toe in or toe out for the rest of the steering and suspension geometry. That's why with the Trakrite it's set to zero, whereas with tyre-place systems where they measure the actual toe, the amount is different for every car and why they have to have a big chart (or a massive database) on the wall.
PaulH Solihull

Ah – I naively assumed that no scuffing would mean zero toe when rolling. We learn something every day :-)
Miles Banister

Most car makers specify a little toe-in on the front wheels because there is no way to keep them perfectly aligned in all driving situations. Having the wheels toed in a little is better than having them toed out at all, which can make the car dart from side to side. If you set the wheels parallel, they will sometimes become toed out due to play in the linkage or change in suspension angles when loading or unloading luggage.

I wrote about this at length a while ago:

http://www.glenngoodspeed.com/volvo/caster.htm

-G.
Glenn G

I was going to edit the last post, but no edit button appears. Anyway, just wanted to clarify that the article on alignment was written for owners of Volvo P1800 cars, but the principles apply to most cars. -G.
Glenn G

That's not what use of the Trakrite implies, nor the description of scuff versus toe in my Toyota Celica manual. Any road up (as they say round these parts) It's irrelevant now as I have managed to get my tracking checked and they found it spot-on, so bar and pointers it will be in future.
PaulH Solihull

My understanding of the need for toe-in or toe-out is as follows:
Toe-in is required on rear wheel drive cars, because as the car moves forward, the drag caused by friction of the tires against the road causes a tendency for the wheels to want to toe out. Imagine if the tie-rod ends were disconnected entirely, and the car was driven forward, what would happen immediately to the wheels. This tendency to toe out causes the small "gaps" in the steering system to be taken up, to the point that when the car is rolling forward, the tires are actually neither toed in or out when set up properly. That would seem to me to be the reason why the Trakrite seems like such a good idea. It is measuring the intended result, in motion, as opposed to how the wheels are oriented when not moving. As the front wheels move over the trakrite, the plate should not have any sideways motion to it.
Toe-out is required on front wheel drive cars, because the wheels want to toe in when under drive. Again imagine what would happen if the tie rod ends where disconnected. Toeing out the wheels while stationary by a certain amount means the wheels should be exactly parallel when moving forward.
When a vehicle is moving backwards, the tires will always scrub. If towing a car for a significant distance from the rear of the car, it will save the tires by using wheel dollies.
Erick Vesterback

Maybe front drive fronts toeing out and rear drive fronts toeing in *is* generally the case, but I don't think it it as simple as that, else why is there a whole database listing the figures for each car when doing it by distance, but only a requirement for zero scrub when using side-slip?

As with any generalisation there are exceptions, and there is one not a million miles away in the rear-wheel drive MGF. This toes *out* at the front by 0 degrees 10 minutes +-6 minutes, and toes *in* at the rear by the same amount, i.e. opposite to the generalisation.
PaulH Solihull

This thread was discussed between 24/08/2010 and 13/09/2010

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