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MG Midget and Sprite Technical - Excessive tyre wear (alignment?)

Changed the nearside front damper a few weeks ago to get rid of leaky and noisy old damper. Great, less noise, better handling etc. However the inside 25% of the tyre tread has worn away literally. The tyre is therefore not upright and I can see on closer inspection the wheel is slightly in at the top which accounts for it.

The top trunnion is the original and is on the right way around and apart from unbolting the damper with the trunnion so I could remove the top arm pin from it in the vice no other parts of the car were removed so the bottom link is exactly where it was. I have looked at the damper arm but there is no adjustment. The tyre fitter was stumped as he couldn't find any free play in any of the suspension to account for it. Any ideas? Do the nuts in the damper mounting move and adjust? and if so any advice on aligning? I just can't see any other way of adjusting. Or is there more than one pattern of damper and I have the wrong one?

I changed the damper on the modern last year, no problems, no tracking needed, etc. and a lot more of that had to come out and go back.

I have really just swapped the part and nothing else.
Dave Squire (1500)

I would re check the tracking before trying to adjust anything else. I have found settings change for no obvious reason.

Bob Beaumont

Despite the replaced suspension parts this is much more likely to be tracking - too much toe out. Is the other front showing any undue wear as well?

Alternatively, contact Pirelli. They know all about rapid tyre wear!
Guy W

Just checked and yes there is a lesser amount of wear on the other side. Definitely happened since nearside damper change and not before.
Now I've checked other side it makes sense now.

Add to the immediate fix list.

Never did like Pirellis tyres. Tried the tyres once and hated them :-( They wore out just as fast back then on the moggie in 1971 or 72). Tried the calendar once and loved it :-) Suppose that's a hate - love relationship ho ho!

Thanks fellers, its the job of the week if I am going to keep these tyres, stay in budget, and keep SWMBO happy.

Now I seem to remember you writing in a thread about pieces of wood, axel stands (or bricks) and string if I have it right Guy. About two years ago. Now what do you think the chances of finding that in the archive are do you think? I would say as good as zilch as it was part of someone else's question.
Dave Squire (1500)

Dave, I never use the archives. I can just never get the search engine to narrow down the number of topics. I put in "front wheel bearings" once and I think it linked to every message ever written!

My wheel alignment method is a bit shade-tree, though seems accurate. Others have more "proper" methods.

Guy W

I like your method. Others at the time were promoting similar. I will be rigging similar. Definitely not buying any kit to do it.
Dave Squire (1500)

I know you wont do it but for other viewers to perhaps consider

as you'll need to change at least one tyre and at 25% wear it would perhaps be more economic to have wheel alignment done professionally with new tyre(s) and then you can practice and learn these sticks and chalk mark methods knowing you're working from a known and correct point

you can also usually take the car back for a free recheck after/within a certain time
Nigel Atkins

Guy,
I don't know if you've seen it but it appears the problem with the tyres wasn't the manufacturer's fault but the teams - the old problem of using intuitive learning and knowledge instead of RTfM - and getting it wrong

http://www.pistonheads.com/news/default.asp?storyId=28016
Nigel Atkins

Guy,

Do you pick the whole car up or just the front when doing the tracking? And if you pick it all up do you support the back axel or the body?

As you have probably guessed I have at last found the ball of string :-)
Dave Squire (1500)

Dave,
The car needs to be sitting with the front wheels taking the weight of the car, not hanging in the air. The reason is if they are hanging down at the extreme of their movement then the track rods are pivoted downwards pulling the wheels inwards and increasing the toe-in. If you adjusted them to be correct whilst jacked up, then they would become toe-out when the car was back on its wheels.

Alignment is best checked with the car standing level on the ground. But this makes it difficult to measure across under the car, especially if it is lowered. In this case raise the car up on ramps or blocks to give a bit more working space whilst still having the suspension compressed.

If you DIY the alignment using "sticks and string" and are still unsure, THEN take it to a garage for checking. If you have got it right and their check shows this, then don't charge. If you take it to them first and they therefore have to adjust it, they will certainly charge. But be aware also that modern all wheel alignment systems used by some garages don't really suit these cars. If the operator doesn't fully understand what the gauges are showing, they may think that all sorts of things are wrong with your chassis and wheel alignment.
Guy W

Thanks for that Guy, I understand.

Dave Squire (1500)

Dave,
you might find the latest John Twist video useful/conformational - http://www.youtube.com/watch?v=a2U2SEbWtrs&feature=c4-overview&list=UU40j4KqUJPMVv4FQ29ro-xQ
Nigel Atkins

Now the strings are up the tracking is way out on the side I replaced the damper on. Way lots of toe out. Wouldn't have believed it if I hadn't seen it.
Dave Squire (1500)

Its unusual for tracking to be out on one side only.
The steering should self centre when you roll the car backwards and forwards before taking the measurements, so that any variation from correct should be shared equally between both sides, even if it is initially only one side that caused the error.
Guy W

Dave,
have a look at that vid and see if the tyre wear pattern matches yours
Nigel Atkins

Looked at lots of vids and yes, I get it Nigel, thanks.

The tracking is out cos I did the nearside damper Guy. Up until recently only worked on the modern so was not expecting the tracking to be out as the nearside strut change I did on the modern last year was just fine. I understand the differences in a geometric way between the two now so no problems; just needed a method.

Still at it cos the end of the steering arm thread is well rusted so soaking in Plus Gas. Its moving but tight and don't want to strip it.

In the mean time in between the tracking swwbo has me working on the plumbing. (no peace and all that). One tap done, one to go!

Then when tracking done, should be off for a test, and then if I feel like it I will re torque the head. (its the long and winding road to reliability and all that).
Dave Squire (1500)

Dave,

I understood that you had replaced the damper on one side and that work may have altered the tracking. But my point was that one would normally roll the car back and forth a few times to centralise the steering. The camber angle will self centre the steering so that the wheels point accurately forwards.

If the tracking is out on one side, as the steering self centres this wheel will pull the other one over, sharing the alignment error as it were, equally between the two sides. It would probably also pull the steering wheel around a bit off centre as well. You can still do the correction on the one side, which will probably turn the steering wheel back to centre.

If yours is definitely showing the tracking error on one side only, then your first guess that there was something wrong with the reassembly of the suspension on that side may be the reason why. It may need a closer inspection.
Guy W

Ok, all good methinks. Car drives fine and all checked OK after two runs and second adjustment.

Just one question. The drivers handbook says toe in is 0 - 1/8", I know this means a tiny amount of toe in and is as good as irrelevant, however can anyone enlighten me where / how this would be measured?
Dave Squire (1500)

difference between:

1) the distance (right across the car) between the outsides of the sidewall bulges at the back of the front wheels (9 o clock)

and

2) the distance (right across the car) between the outsides of the sidewall bulge at the front of the front wheels (3 o clock)

is how I've always measured mine.

the fronts are 0 to 1/8" further in.

I have mine set a bit more than that on 175 70 13 tyres.



Rob Armstrong

Thanks Rob, that's how mine are now so that's good to know it works. All the vids I looked at were going for dead straight.
Dave Squire (1500)

Thanks Rob, that's how mine are now so good to know it works. All the vids I looked at were going for dead straight.
Dave Squire (1500)

I had always thought the measurement was taken at the wheel rim at 9o/c, not the tyre sidewall bulge.

Surely the measurement given is for a Spridget, for a 13 inch wheel, not for a specific size of tyre?
Lawrence Slater

Agree, I always take the measurements at the wheel rim.
Guy W

I expect the difference between rim and sidewall measurements will be small, and sidewall bulge is a lot easier to do. With different wheels the rim is often in a different place anyway.

keep an eye on tyre wear, if it's ok and you're happy with the handling then you're good to go!

Rob Armstrong

Yup that's possibly true, the error is probably insignificant, given that there's 0-1/8th" to play with to get the correct angle of toe-in.

But even though a wheel rim may be deformed a little, a tyre side wall is more likely to be deformed I would have thought.

Also, a 13 inch rim, is a 13 inch rim. The measurement is in the same place no matter which brand/type of wheel surely? Solid or wire. The diameter is measured across the wheel from bead seat to bead seat. So how can this vary wheel to wheel?

Having said that, when I set mine, I sometimes then alter it subsequently, to how I visually read the tyre wear forming, until it's even.
Lawrence Slater

Wheel or tyre wall makes no significant difference. What you are measuring is the very short 1/16" base of a very skinny triangle, 6 3/4" high, or 8" high in the two alternatives. The difference in the length of the base will be well within tolerance and for all practical purposes too small to measure anyway.

Much harder is to get a true 3 and 9 o'clock position for the measurement as the chassis and engine get in the way. It can really only be done wit some sort of cranked ends to the measuring device so an ordinary tape measure or string won't work. L I know has a bought in device with cranked ends. I make one when needed that does the same thing as it is such a rare task, once set there is little likelihood of it changing unless you are making some other alterations.
Guy W

I have a [__] shaped thing that pokes all the way under the car in front and behind the wheels. Yup I agree Lawrence that 13 inches is indeed nearly always 13 inches, my comment was more thinking that the rim is in a different place relative to the turning axis of the kingpin, what with different offsets and such. I know fitting the slightly longer bottom arms/wishbone pans to mine threw the tracking out completely, it was so wrong as to make the car nigh on undriveable. Mended now though.

the [__] device I have has bolts through captive nuts on the top bits, so knowing the tpi of the bolts allows you to work out how many turns different the front needs to be to get the toe in measurement. It was built for dad's mini originally and works well for narrow cars - the Rover 25 is too fat for it!
Rob Armstrong

Gentlemen, tracking is measured to the mounting face of the wheel hub and is interpreted as the centre of the wheel or in modern tracking equipment the inside face of the wheel that fits against the surface of the hub.

Easy to find def on interweb.

However the toe in or out definition of how to measure is another thing. Can't find the def for that so did what rob says. I am in agreement with you all its so small an amount as probably makes v little to no difference on a road car being driven daily on a whole range of surfaces.

Good approach Lawrence, I like it, presumably you use the rub the hand across the tread method to feel for the smooth versus rough edges?

Would be nice to know what the def of how to measure toe in officially though.
Dave Squire (1500)

"you use the rub the hand across the tread method to feel for the smooth versus rough edges?"

Not quite so subtle as feeling it :).

As Guys says, I've got a cranked tool, and as also said, once set it sould be remain right. But my rims are a tiny bit bent. 2nd hand ally minilites. So I get it pretty much as required, and then look for visible signs of "feathering" on the outsides of the tyres over the next week or month, and adjust if needed. Then it doesn't get touched again unless a rod end is changed or the like.


Lawrence Slater

Dave,
I am going to be pedantic now! The measurement that you describe, from the inside face of the wheels is the track. Tracking is the process of adjusting the wheel alignment or the Toe-in of the wheels. Slight difference in the use of the words Track and Tracking!

Tracking (Toe-in) is important to do accurately and has a considerable impact not just on tyre wear, but on the handling as well, especially under braking. Although the toe in is small it does make a noticeable difference to the feel of the car, so does need to be right.

When I said it makes no discernible difference I was meaning there is little difference between setting the alignment by measuring from the tyre wall or from the wheel rim. But whichever is chosen, the setting still needs to be done accurately.
Guy W

My apologies, I have found the answer to my poorly defined mutterings, and lets hope Nigel is not going to use this against us!

Yes you guessed it! the toe in definition is in the owners handbook for a 78 on page 47. There is a pic and a description. (five lines). The pic has pointers pointing in line with the rims of the wheels. (like Lawrence says). And the text says:

<< The front wheels must be set so that the distance 'A' (pointing to the leading rim edges) is 0 to 1/8 in (3.2mm)(toe in) less than distance 'B' (pointing to the trailing rim edges). >>

So my toe in is approx. twice what the good book says as its the difference between the front and back rim measurement - 3 and 9 o clock - as Lawrence has said. It is not a distance simply measured between the front rims which I have approximately done.

The problem with the good book is its like a religious text, no index, everything is on faith! I found this looking for the definition of degrees peak to peak on a 1500 front timing cover. Doh. Now found an article by Deb giving all info for that by the way.
Dave Squire (1500)

I think between us we had described that process several times over! I don't understand at all how you can determine the toe in just by taking a single measurement anyway. And I still don't understand how you go to the statement earlier that "Now the strings are up the tracking is way out on the side I replaced the damper on. Way lots of toe out!" How were you measuring this?
Guy W

well of course I'm not going to let this slip

Dave,
if you'd have thoroughly read or reference the good book you'd know the info was in there and it's it's cross referenced in the 'Routine Maintenance Summary' pages in my good book along with all the other schedule cross reference to how to do the work on which page in the book (that sentence makes more sense for those with a copy of the good book)

you put in a post before that you check the good book first but now you've fallen in with the anti-reading books-to-learn brigade

the only reason I didn't pipe up before was











because in my copy of the good book it doesn't have the illustration and suggests you go to 'your Distributor or Dealer' as the work requires a special gauge
Nigel Atkins


<< Way lots of toe out!" How were you measuring this? >>

No measurement; it was so great I could see it simply by sighting in relation to the parallel strings once the strings were up and the correct distance apart Guy. Then by adjusting the track rod I gat the wheels parallel to each other, and then I allowed a bit for the toe.
At some point soonish I will make the cranked feely gauge for setting the distance across the front rims to check everything. As you probably realise I need to do everything at least twice to put my mind at rest and believe in my work.

Yet again Nigel my imperfections have been exposed to the world. Inability to read and internalise verses of the handbook this time. That is; I am pretty certain I have read them before at some point and forgot. :-)

45 mile run yesterday mainly open roads in traffic, some city, and all well, by feeling across the treads the wear has changed from lots inside to a tiny bit outside (rough versus smooth feel for edges of tread) and no visible wear for that trip. Will monitor as Lawrence says. Well chuffed as its another one of those 'mysteries' of mine solved.

Thanks everyone once more for your forbearance and help, much appreciated.

Back to mechanical next.
Dave Squire (1500)

Dave,
so you were using string down the side of the car aligning the front with the rear wheels? Sorry, I had thought you were setting or checking the toe-in somehow with string across the width of the car between one front wheel and the other. And I was struggling to think how you had managed that!

Here's a simple gauge for measuring and setting the toe in. Get two lengths of wooden dowel each about 30" long, Strap them side by side with a few elastic bands or small zip-ties. Thy need to be held parallel tightly enough that they don't flap about, but not so tight that they cannot be slid one against the other to extend the overall length.

Offer them up under the car and slide them along, increasing their length until the opposite ends touch the inner wheel rims as high up towards the front at of the wheels as you can get. Mark a line with a pencil across one dowel in line with the end of the second dowel. Repeat with the dowels held as high up on the front wheel rims at the rear of the wheel and mark again. The difference between the two marks is the amount of toe in. (or toe out if the second measure is shorter than the first).

This measuring method can be very accurate. Its a method used by joiners to transfer internal dimensions as when making window sashes. The limitation for setting toe in is that the toe in measure really needs to be done at 3 and 9 0'clock levels on the wheel rims. And at that level the engine and chassis rails get in the way. Either you take an easy compromise and measure at something like 4 and 8 o'clock levels, setting very slightly less toe in (perhaps 3/32 instead of 1/8") or you could make some sort of cranked ends to the dowels so they reach up to the correct levels on the wheels. Maybe something out of stiff wire, but anything that isn't very firm can distort and give a false measure. My car is pretty low but I still prefer to just use straight sticks and adjust the measure slightly. With the higher ride height on a 1500 this should be fine for yours.

Of course, having got your measuring system, if the marks show the wrong setting you then need to slacken the locking nuts on the tie rods and make the necessary adjustment. Most tie rods have a couple of flats ground into them to take a spanner as you need to screw the tie rod into or out of the track rod end to get the settings right. If there are no flats, then grip the tie rod with mole grips to turn it.

Don't forget, this needs to be done with the car on level ground and you should roll it back and forth by a couple of yards to get the wheels pointing straight forwards before you start.

Nice little job for a sunny day!
Guy W

Dave,
I can well understand forgetting something (well almost everything really) at least you have a copy of the good book and have read it you now just need to remember to reference it

I might have the wrong mental image but I'm thinking you'll need at least one new tyre or different tyre to replace the very worn front tyre if 25% of the tread width is worn away

I should think with the tracking that much out before you might notice the improvement of having it correct

when you have a car that can have full geometry adjustments and set up (not Spridgets obviously) once that is done properly the handling is like going from night to day with the handling
Nigel Atkins

Yes Guy; the old man was a carpenter and I use similar methods when working on jobs about the house to save measuring with tape measure and be accurate. Now I know what I am measuring, as in where, all your advice makes sense. No problem in future. Already have the door frame stop timber for it. (thin laths).

And Nigel, I changed my mind about carrying a spare in the midget when I started using it as my occasional day car. I need to get stuff in the boot as well as the 'whats in your boot' list (no spare on my list although there was a battery) so had a good spare awaiting use on the nearside front and that is the one that is now giving the correct wear pattern. Plan is to sort other front damper soonish, get car set up properly again, and then new fronts.

Now where is that strobe light? (got to keep you on your toes you know) - just kidding - I know how this one works, and read up the Debs over and over for the last few weeks, and looking at the static, unless something is seriously wrong with the dizzy, vacuum, or weights its a gonna be correct already. Car pulling well at the moment by the way and off for a 70 odd mile return trip first in the morning on B roads or less so will see how things are after that.

As said already, and once again, thanks for all your's help. It is very much appreciated.
Dave Squire (1500)

This thread was discussed between 03/07/2013 and 09/07/2013

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.