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MG Midget and Sprite Technical - Tyres - again!

A couple of years ago there was a discussion about tyres, resulting in my purchasing 2 Uniroyal Rain Expert which went on the front. That was in May 2016. Early this year I noticed they were wearing unevenly, with much reduced tread on the outer edges, especially the nearside one. I spent hours with a tracking gauge and was sure I had it right, but the wear pattern continued. In April I got the local independent garage to check the entire steering geometry, and everything was correct except for a very slight toe-in which they corrected. Since then the wear problem has got worse, so back it went to the garage yesterday. This time I gave them the service manual and they again found that everything was correct.

These tyres have only done 6,500 miles, and the N/S one is down to about 2.5mm on the outside edge. There is no sign of feathering on either of them. I have never seen tyre wear like this in the 40 years I have had the car. Well they did go down a bit on track days, but these tyres have not been used on the track. The garage said that compounds are getting softer all the time and you have to pay huge amounts for anything that really lasts. I admit I do enjoy roundabouts, but I always did and was if anything more aggressive in my youth!

I remember some other folk had used these tyres, so I would be interested in your experience. I am looking at replacing them before they are 10,000 miles old.

Les
L B Rose

I have a set of 4 rain experts I fitted at the start of 2017. Done about 3750 miles on them and the fronts are all looking good with 5-6mm. Most has been touring mileage abroad and to Scotland. I don't drive it with as much verve now though!

Bob Beaumont

Possibly slightly under inflated? Even slightly soft at the front will wear faster on the outside edge.
GuyW

I run mine at 22 psi at the front with a 5/8" ARB
Bob Beaumont

Just checked pressures. They are 19.5psi. I normally keep them just over 20, vs 18 recommended for the original 145s (these are 165s on 5" rims). I'll get them up to 22 and see what happens.

Les
L B Rose

Les,
what toe-in do you have? A mate who used to be in the business and used to classic cars reckons near to parallel for road going. I used to run mine at 0.5mm and think I went to 1.5mm by mistake and had it reset there again last time.
Nigel Atkins

No Les, 18 psi is for cross-ply tyres!
The handbook states 22 front and 24 rear for 145-13 radials. If fully laden then increase the rears by 2 psi, and for sustained high speed cruising increase by 4 psi all round. When mine was new back in the 70s I used the M4 to commute into West London and ran 24 front and 28 rear.
David Smith

I have always run mine with 24 front and 28 rear, using 165/65/13s and around 1/8" toe in. Wear on the front is pretty well even across the tread. Car is lowered about 1" at the front which adds a little negative camber, probably compensating for a tendancy to wear faster on the outer edge which might otherwise result from the toe in I use.
GuyW

excuse the typo, meant to say *19* is the book figure for crossplies...
David Smith

the handbook gave tyre pressures "back in the day"..modern tyres are now made from compounds with different properties which may benefit from slightly higher pressures. No toe-in for me...I run parallel with no problems
David Cox

Tyre pressures is an interesting subject
Personally i like them high--
But the interesting bit is why run more in the back than the front
On my old racer I moved the engine back 6" to get the desired 55% rear weight with me in it and still ran higher pressure in the front than the back 38/34 to get the temps.right
A std road car is nose heavy so in my way of thinking front tyre pressure should be greater than rear

I'd be trying 26 all round---but that's just me

willy
William Revit

Not just you, Willy, me too. 18/19 is too low.

26 all round for me.
Rob Armstrong

As there are a lot of variables including the make and models of tyres I think starting with the book as a guide then increase 2-6 psi in 2psi stages to see what is best.

Personally on my set up I've had to drop back to book especially with the state of our roads but some seem to run happily at much higher pressures.
Nigel Atkins

Can I suggest that the camber angle is out for some reason maybe due to damage caused over a pothole or possibly due to the wearing of suspension or hub hardware.

As we are aware the camber is not "adjustable" on these cars.

A 4 Wheel Laser check while interesting would be near £100.

Can I suggest one of these inexpensive guages to check if the camber is out on this car. How to effect a cure to the tyre wear is another kettle of fish but that is my thoughts on the subject.

https://www.ebay.co.uk/itm/Universal-Magnetic-Camber-Castor-Strut-Wheel-Alignment-Gauge-Tools-Adjustable/123114411239?hash=item1caa30d4e7:g:e1oAAOSwFWda4Cm5

Eddie Cairns

It's easy enough to check the camber with a 12" spirit level and a bit of trigonometry, place the spirit level vertically against the rim and measure the gap at the bottom, for standard positive camber, and the camber can be worked out.
David Billington

Agreed but plenty people cannot get their head around that particular calculation.
Eddie Cairns

I got the garage to check all suspension geometry and they said it was spot on. I have the pressures at 24 front and 26 rear now - 4 psi up from before on the front. Time will tell.

Les
L B Rose

Les, did they check the toe in as well?

I only suggested tyre pressures were too low because this will cause them to wear on the outsides of the tread as you described. Its probably resolved now, but excessive toe in would still be the number 1 most common cause.

It should feel much nicer to drive with those raised pressures - more nimble, lighter steering and less wallowy on corners. What's not to like!
GuyW

Yes Guy, I originally took it in for a check of tracking. There is zero toe-in - in fact I had got it right anyway. What's not to like is the ride, but the handling is sharper.

Les
L B Rose

Ah yes, I suppose it will feel rather firmer. Not good for ageing B&B s.
GuyW

This thread was discussed between 06/09/2018 and 24/09/2018

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