Check my figures, please?

I am checking and adjusting the toe of my MGF. I am aiming for 5' of toe in at each end.

Difference between front track and rear: front is 10mm narrower.
Wheelbase is 2375mm.

2375 x 2 x pi is the circumference of a circle with radius = wheelbase.

That when divided by 360 gives 41.5 mm per degree so 5 minutes of toe in equates to about 3.5mm.

A laser placed across the rear wheel, level and touching the rim at each end will strike a pointer at the front wheel centre 1 1/2 mm outboard of the edge of the rim. In practice, the laser is mounted on a block so there is a known offset from the edge of the rim to the beam of 68mm, so the true figure is 69 1/2mm.

A laser placed on the front wheel in the same way will strike the pointer at the rear wheel centre at 64 1/2 mm.

If you are bored enough, would somebody please check my calculation as I think this should work for DIY 4 wheel alignment.
Thanks.

This is the home made laser tracker in action. An examination of the rear tyres showed too much rear toe in after fitting the polybushes and adjustment of the rear control arms has dialled them in perfectly. I'll do the front end later in the week. When I have time, I'll do a how to, showing the construction and operation of the tracker.

All good stuff, once I'd freed off the rear control arm nuts I was going to devise a system, however there's no point re-inventing the (DIY) wheel alignment method.
I can't check your figures, you've worked in metric, you are aware that the UK has cast europe off to drift where it will. I'm just suprised you used degrees & minutes & not radians.
Your work is never less than impresive. Mike.

I did use radians but that would make it less comprehensible to most people so I reduced it to simpler terms. I used the MG quoted dimensions like the unashamed European I am but the English measurement is 2 1/14 Ells.

I was going to have a jolly trip around the mysteries of the imperial system to bolster you against meeting entrenched geezers such as I, but I’ve just read about your tribulations with the tyre fitters & have decided to keep a low profile. The more I can do on the car, the less time it will need to be in the clutches of the “professionals”, however the older I get the less easy it is to get into & out of the pit; the spirit is willing & the grey matter still functions to a high(ish) level, it’s the undercarriage that lets me down.

Exactly. If I could fit tyres, I would. The rest I do for myself. My bodywork skills are not as good as I would like but better than most. The rest is fairly easy. Just set the rear end to half a well ripened barleycorn toe in measured over the wheelbase.

I prefer angstrom unit, angstrom for distance, bushels for weight, cord (128 cubic foot), volume, which can be inconveinient when baking. The fortnight when measuring time, when sidereal time proves problematic, fathoms & nautical miles for boating or f***ing fathoms plus f***ing nautical miles for coarse fishermen. The dram is popular over the border, there are however different sizes from wee upwards.

Here in Oz we use the "bee's dick" and the "gnat's nasty" as small lineal units for measurement

I regularly use the cord which is three cubic metres, 3 stere to the cord, of course. It is the measurement for firewood. Cobber will know"' as a tenth of a French inch but the only imperial measurement of real value is twenty fluid ounces, give or take the head.