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MG Midget and Sprite Technical - DIY front wheel alignment
|Has anyone any good tips on sorting the toe in on a newly rebuilt '67 sprite. Was hoping to set up two strings either side of the car parallel with the hub centres and get my ruler out! If this is the way forward - is the 3.2mm or 1/8" the toe in measured on the wheel rim or should it be the tyre...I'm thinking the tyre but could be wrong...|
|Theres a "Drive over plate" (for lack of a better word/termenology) made by gunson and only sold in the UK, it appeartly works like a charm,and super easy to use. Ive been meaning to buy one, several people on here seem to like it a year ago when we talked about it last|
AHhhh i found one on ebay.. Number 180514378008
I use a long ally bar (straight); park the car on flat road; align bar 1/2 way up one front tyre, and arrange steering so bar parallel to side of car. Then align bar with other front wheel and expect it to diverge slightly from car body, looking backwards.
Not scientific, but works better than any tyre-shop with their laser gear, and my tyres wear perfectly evenly (normally end up renewing them after 5 or 6 years due to old age and loss of grip rather than wear).
BTW I always move car backwards/forwards say 5 yds whenever steering moved or track-rod adjusted to allow steering to settle.
Used the same process on my Honda a couple of years back, having spent £1k+ on alignment and tyres with no improvement.
I'll let you know how I get on .......if I drive off and see my boot lid overtaking me I'll know it's out ;0)
|I use the string and a helper method, quick and easy. It has proven so consistently spot-on that I've give up gettting the tyre shop to check it.|
I do one side at a time, it's simpler.
Measure the height off the ground of the front of the car of a suitable reference point - top of wheel arch, front of sill, bumper, whatever suits.
Jack the front up and check each wheel for run-out. If there is run-out, mark the high point and bring it to the top. (Ideally you would check that the run-out over 90 deg either way from this mark is the same amount, but in practice it hasn't made much difference.)
Lower the car to the ground with the high point marks still at the top.
Roll the car back and forwards as per Anthony's advice until it has settled to its original height.
Set the steering wheel to straight ahead.
(Not essential, you can adjust the toe-in on one side only if you don't mind a slightly crocked wheel)
Get two flat-ended rods or sticks and put a nick in each of them at 100mm from the flat end. If your car has different track front and rear you will need to shift the mark on one stick to compensate.
Example: BMC lists the midget track as 1-9/16" (40mm) greater at the front than the rear, ie 20mm per side, so put the mark for the front rod/stick at 80mm, the rear at 100mm.
Get a helper to hold the rear rod/stick on the edge of the rear rim (at the height of the wheel centre from the ground - ie the very front or rear of the rim), with one end of the string in the nick.
Hold the other rod on the front of the front wheel, same height off the ground as the rear one. (The string should then pass over the centre of the wheel) With the string in the nick, pull the string tight (tight enough to eliminate sag will do)
Measure from the string to the rear of the front wheel rim. The distance should differ from the front by half of the specified toe figure. For toe-in, the measurement at the rear of the rim will be LESS than at the front.
If necessary, adjust track rod until the right figure is attained. (Check that the steering wheel hasn't moved!)
About 1 turn of the track rod changes the toe by about 4mm. The exact amount depends on the pitch of the track rod thread and the length of the steering arm, but this is near enough to get a feel for how much to turn the rod before measuring again.
Repeat the string measurement and any necessary adjustment on the other side.
|Very interesting process, Paul. Can you provide pictures?|
|I did mine yesterday. I used the basic method described in the Haynes manual.|
I drive the car straight ahead on a flat surface. I measured the height to the wheel center, in my case 10-1/8 inches, and mark that spot on the front and back half of the outside tire.
I made an adjusting 'tool' by making two wooden "L"s with the short side about a foot tall. I put a nail in at the wheel center height sticking out about an inch.
I then set the nail on the front inside edge of the wheel rim, not tire, and overlap the two longer legs and put a pencil mark across them.
I then roll the car forward 180 degrees so that the rear mark is now at the front at center height. I then take a reading again. The correct toe-in is zero to 1/8 in. Adjust the tie rods accordingly and equally to get where you need to be. If the steering wheel is off center, then adjust one side in and the other out to correct.
The key is to not back up at all. This will upset the geometry. You can see this for yourself if you back into a parking space your front wheels will have a visible tilt.
The only thing that makes this hard is that the cars are so damned short that it is difficult to work underneath while on the ground.
|I use a DIY method which is far simpler - and probably far less accurate than Paul's - but it seems to work OK for me.|
I have 2 lengths of 1/4" wooden dowel, fastened side by side by wrapping with a couple of elastic bands. The dowels are about 4" less than the distance between the inner rims of the front wheels.
I roll the car back and forth a couple of times and bounce the front suspension a bit. Not sure why but it makes me feel as if I know what I am doing! I then hold the end of one dowel against the inside edge of one rim and slide the other dowel through the elastic bands until the end touches the other wheel rim. I do this as high up on the wheel rim circumference at the front as the chassis rails will allow. Mark the overlap with a pencil. Then repeat at the rear circumference and the difference gives the toe-in (or out).
Its very quick and simple, takes no account of the rear wheel alignment but is reliable and produces good results for my cars.
|Just tried editing my message in the light of Lee's post. (But missed the 5 min deadline!)|
Methods are basically the same, but I like Lee's sophistication of the two arms at right angles. This gets around the main limitation of mine of the chassis rails preventing one from measuring at the wheel centre height. This doesn't matter if setting at parallel, but makes judging a 1/8" toe-in a bit difficult. I like Lee's modification and will certainly try that next time around.
I cheat, I do my toe with the car on the trailer by just measuring from the sides of the trailer to the wall of the tyre and set it straight ahead - 0 toe in
Works for me Cheers Willy
|Thanks for all the tips guys - cheers, Neal|
|Lee, you wrote:|
>>> I then set the nail on the front inside edge of the wheel rim, not tire, and overlap the two longer legs and put a pencil mark across them.
I then roll the car forward 180 degrees so that the rear mark is now at the front at center height. I then take a reading again. <<<
Sounds to me like you're making the same measurement twice... that is, the distance between the rims ahead of the axle. Am I reading that wrong?
That said, I like the idea of your brackets, and may try to fabricate something similar.
|Gryf, my man, you are an observant fellow. THANKS!|
What I SHOULD have said was, "set the nail on the front edge of the wheel rim and overlap the longer legs and put a pencil mark across them AND THEN do the same thing at the rear edge of the wheel rim."
I roll the car forward a half turn or 180 degrees and take the readings again and average the sums to minimize errors.
It helps to have a helper set the nail on one side while you work the other.
Another method that avoids crawling around under the car, but I think is less accurate, is here:
This thread was discussed between 30/07/2010 and 04/08/2010
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.