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MG Midget and Sprite Technical - wheel on caliper woes!

Hi! I'm a new member on here so here's a quick intro followed by my problem....
My midget was the preverbal "find in a barn" purchase, she'd been laid up for 4 years & in a sorry state, I set about fixing her up, albeit on a limited budget (taught myself MIG welding in the process) ..... long story short..... moving house left me with no storage space so midget was left in an ex girlfriends garage, I assumed it's fate was sealed.... 6 years later I discovered the midget was still there, nothing had been touched, a quick recovery to my new house has it sitting in front of me now. A new set of points, consdenser & splash of fuel & she started on the button.
The problem I have is the offside wire wheel is contacting the face of the brake caliper & scoring it badly, I've tried different wheel but the problem still exists, what I'm not sure about is wether the brake assembly is at fault or the wheel hub is causing the problem, I can't see any spacers that are worn or missing, any ideas?

I tried to upload a pic of the scored caliper but Internet connections on this phone baulked at that idea.
P Thurling

Many years ago when I bought my Midget, when I first removed the wheels I noticed the rear face of the inner hub of the wire wheel was fouling the caliper on the nearside front.
The PO must have ignored it because it had worn a little groove in the caliper.
I dressed the flange on the inner hub rear face with a small grinder (would use a Dremel type of thing now)so that it wouldn't rub any more.
Since then I have changed the calipers and there is no fouling occuring any more with the new ones.

Obviously I removed the minimum of metal so as not to weaken the wheel flange, but actually very little needed to be removed, in my case.

That was about 12 years ago and there have been no problems since.
I never change my wheels round. The n/s front is always on the n/s front etc, etc.

If you haven't already done so try swapping the front wheels over to see if both do the same.
The tolerances during build seem to be a bit variable, and one wheel might foul and another not.
Also try a rear wheel.

I wouldn't advise removing too much metal from the wheel if the rubbing is really excessive.
JB Anderson

Just re-read your post ,P, and see that you have tried swapping wheels already.
Sorry, I missed that.
JB Anderson

thanks JB, I've tried all the jiggery pokery I can thnk of, not sure about cutting anything off the inside of the wheels though, the spoke ends are a bit too close as it is without slicing any more off.

I have discovered that there's 2 different type of disc, BTA 383 for steel wheels & BTA 469 for wire wheels, I need to find out if there's a difference in size from the hub & see if I have the wrong ones.
P Thurling

I wonder why there are two types of disc, maybe someone else will know.Probably because the hub mountings/sizes are different.

If the inner flange of your wire wheel is fouling the caliper then that is independent of the disc and I don't think your problem is due to the disc.

The critical size is from the caliper mounting lugs on the hub/stub axle to the outer face of the caliper, when mounted in position.
If the caliper has an oversize casting for the outer cylinder then that will foul your wheel.
Perhaps you could take a measurement on the other front wheel brake assembly and see how much the caliper on that side sticks out.If it clears the wheel that fouls the caliper on the other side, then the caliper that is fouling must be slightly over size in its casting.

Before being laid up had the car been used for a long time with the wheel rubbing the caliper?
It would very quickly wear a groove and then it wouldn't get any worse.
I wonder how thick the cylinder castings are, and how much meat you have to play with before breaking through into the cylinder.
It would be interesting to cut an old one open to find out...no, it probably wouldn't be interesting really, just a thought!

The flange on the wheel that I dressed slightly, had a sort of sharp edge that I was able to remove without weakening the wheel, and that did the trick.
JB Anderson

Another reason for the fouling could be that the wheel on that side is moving too far inwards towards the caliper when it is being tightened with the centre nut.
This would only be due to an undersize splined hub allowing the wheel to move too far along the splines before reaching the angled seat on the inboard end of the splines.
The only solution for that is a new hub and I don't think you want to go there!(For a number of reasons)
JB Anderson

The Discs for s/w and w/w are different. Look at the pic, one has a larger distance piece.


Alex G Matla

The hub is mounted onto the stub axle and torqued into position which effectively fixes it's position relative to the stub axle.
When the road wheel is fitted to the hub it's relationship to the stub axle is also therefore fixed.

The caliper is bolted directly to the lugs on the stub axle.

Therefore the position of the wheel relative to the stub axle and caliper is always fixed regardless of the disc.

The different sizes of protrusions on the two different disc types will be to ensure, when fitted, that the disc always runs directly in the centre of the caliper whether a wire wheel hub or steel wheel hub is fitted.

I think if the wrong disc was fitted, for example a steel wheel one, the disc would be in completely the wrong position axially relative to the caliper, and it would be obvious.

I am quite happy to be proved wrong if it will help to solve this problem!

I have a feeling the fouling is due to a bit of lax tolerance-keeping during manufacture of probably more than one component, culminating in an interference rather than a clearance situation.
JB Anderson

JB, you're right. Wrong disc would only put the disc out of alignment of the caliper.
Alex G Matla

thanks for your input everyone.
it appears the difference between the steel & wire wheel hubs is the problem.
W/W hubs are 50mm, mine are steel wheel hubs at 30mm, changing them will hopefully solve the problem...... although it doesn't explain why only one side is rubbing.
Flyster

Are you sure the discs will run centrally in the calipers if you change the hubs?
If you are using the wrong hubs and there is a 20mm difference between them then I would have expected you to have a huge 20mm fouling on both sides.
As it is, the interference is not huge so I tend not to think changing the hubs will help..but if that does solve your problem then I will stand corrected! (again)
JB Anderson

hang on a minute - are you saying you have a 'bolt-on conversion' set of wire wheels, as against a proper set of BL parts originally designed for wire wheels?
I've always considered bolt-on w/w conversions the work of Beelzebub...
David Smith

P - Let me get this straight - you left the car at the ex's house/garage for 6 years, you got it back and all was well? If only my Ex would have been so helpful LOL
Dave
Dave Price

Replacing the 30mm hubs with 50mm ones wont affect the position of the disc, it does indeed seem to be the work of Beelzebub.... but the whole car is ravaged by demons.... especially the rust devil, it'll take more than a splash of holy water to sort it!

I'm not sure why the car was never touched Dave, the garage is in a block well away from the house and it was never used for anything before, the rear wall collapsed a long time ago and makes it useless for storing any household goods, plus the door is knackered, hanging off it's hinges and not so much an 'up & over' as a 'lift, jiggle, wrench, pull, heave, swear, pull, push, shake and prop open with a 6ft length of timber"




Flyster

Must be the wrong discs then, I can't think of anything else.
Maybe mine has always had the wrong discs too but the difference was not enough to really make a difference once I had relieved the slight fouling of the caliper.
Must go out and have a measure!
JB Anderson

About 20 years ago I converted my car to wires. I changed the rear axle but at the front I simply mounted the wire hubs onto my existing stub axles.
I did have the "slightest" rubbing of one of my wheels on the caliper but it just about fetched off the paint and no more so I never really worried. However knowadays I have knockon Minilites fitted and no longer have a problem but I am now intrigues by this thread.
Robert (Bob) Midget Turbo

I am intrigued too!

My car is 1977, have had it for about 12 years, and I bought it with wire wheels fitted.
I have no idea if they were on the car when built or added later.
I changed the handbrake cable last year and the one for a wire-wheel car fits perfectly, so hopefully that means the rear axle is a correct WW one.

At the front though, what is the difference between a "built as WW" car and one converted later?

Is it just the discs have a longer extension shoulder to give more clearance or is the difference more fundamental?

Any knowledge gratefully received!
JB Anderson

This thread was discussed between 17/04/2011 and 03/05/2011

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