MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Riveted wheel failure - is it common

I run the early holey frogeye / early mk2 wheels on my car though strictly speaking it should have the later solid ones. When I was a forum regular there was occasional talk of the riveted versions of these wheels failing i.e. the rim separating from the centre.

I'm just about to get some wheels blasted and painted as the ones I had done 30 years ago (30 years ago!!!!) are beginning to look a bit tired.

My stock of spare wheels doesn't stretch to 4 welded ones and I'm pondering doing some riveted ones.
So, is this riveted wheel failure thing a myth based on a very few isolated incidents or is there a real trend of these failures.

Discuss / thoughts please.

(I could get some of my in-use wheels redone but if I can avoid that I'd prefer it).

Thanks
Jeremy Cogman

I have riveted one on the Frogeye and they have been there for the life of the car. I have used the car on the occasional track day/sprint in the past and for a number of Europe trips. No problem to date during 45 years plus of ownership. I use the standard 145/13/80 tyre There was apparently a cracking issue around the centre where the holes are made (to adjust the brakes without removing the wheel). The later solid wheels do not have these holes. I personally though have not had that problem.
Bob Beaumont

Jeremy

This is a good question as I have wondered the same when contemplating my mix of welded and riveted wheels on my Mk2 Sprite and hopefully getting it sprinting/hillclimbing before too long.

Bob’s experience is very handy which is a nice counterpoint to the apparent reason for the factory to switch to the wheel without the MkI style multiple cooling holes approx 3 months into the production of the MkII Sprite with the 1098cc engine and disc brakes (HAN7, unofficially known as the MKIIa) - Horler has this in Dec 1962.

Interestingly these later wheels do initially have two brake adjuster holes which seems to have been deleted quite soon (maybe when the rear brakes switched to the dual piston rear wheel cylinder adjustable from the rear backplate rather than the sliding single piston item adjustable from the front through the brake drum; noting they were already superfluous for the front!). I have started collecting a set of these as a period upgrade. I guess the twin piston rear wheel brake cylinder was in place by Jan 1964 intro of MkIII Sprite, and hence no need for the adjusting holes for rear brakes, but maybe earlier?

Terry Horler’s book mentions the move away from the earlier wheels due to strength (but had not heard of the adjusting holes as the reason why) and IIRC one of my books on BMC Competitions Dept (rally cars) cites a move away from the early multi-holed wheels on 948cc works Mk1 midgets for reasons of strength. This for the Comps Dept may have been more about in 1962 getting one car - YRX 737 - a DHMC front disc brake conversion to fit and needing a switch to wire wheels to do so and rebadging the car as a Sprite and running homologated as a Sebring Sprite MkII (all about the year before the standard car got different Lockheed front brakes and 1098cc engine in MkIIa form).

I wonder if the tyres on riveted wheels go flat quicker?

Sorry for disappearing into an arcane rabbit hole!

Cheers
Mike
M Wood

Mike, it's an interesting little aside topic in its own right!

Another subtle change to add to the mix was when changing from rivetted to welded rims, but retaining the adjuster holes. The adjuster holes are moved around slightly such that a diameter line through them no longer bisects the two wheel webs, mid way between a pair of the cooling holes.

It does look like they were progressively playing around with the design, looking for a stronger solution.
GuyW

I believe rivetted wheels were always fitted with inner tubes on the production line - they couldn't be trusted to seal. Tubeless tyres were cheaper to fit as well as having the safety advantage of not deflating explosively when pierced by a nail. I suspect the change to welded wheels was more about the sealing than the strength: after all the Titanic had been held together with rivets and there wasn't any problem there, was there?

Also changed during the run of the frogeye were the gauge of the steel and the depth of the strengthening ribs, as well as the important re-alignment of the holes that Guy mentions. At every change, the Service Bulletin contained a stern warning that all cars used for motor sport should use the latest, strengthened wheel. I believe BMC Service was a fairly independent arm of the Corporation, and of course an extremely important one: it may be that they considered their direct feedback from dealers every bit as important as anything the Healeys or the Comps Dept had to say.

At any rate, I don't think the wire wheels were the attraction on YRX 737 as much as the Girling discs (not for greater braking power but for the fact that they didn't have to be adjusted all the time), the ARB, the Weber DCOE and the alloy panels. The Healeys used the Dunlop 60-spoke wire wheels on the works Sprites at Sebring in 1959 because they knew they were immensely strong, relatively light and even flexible - important advantages on the rough and rutted Floridian concrete.

Anyone considering using early frogeye wheels for any sort of spirited driving would do well to examine this period pic, where the left rear wheel is collapsing. The US driver was able to crawl from under the inverted car because he had a rollover bar - very few people had them in England in 1959/60:



Tom Coulthard

Ouch.

That's one of the main reasons that I have one in my car. Not that I drive like that.
Martin

Interesting I have never experienced any of the problems described such as flat tyres etc perhaps I wasn't trying hard enough!! but for safety's sake it makes complete sense to use appropriate wheels for motorsport.
Bob Beaumont

Must confess I had to look up what YRX737 was. I have the riveted wheels and have wondered about their safety.
Bill Bretherton

Thanks for your thoughts folks.

I've done a bit of research myself and come up with the following threads:

This one contains reports (with pictures) from our very own Flip of wheel failures: http://www.mg-cars.info/mg-midget-sprite-technical-bbs/steel-wheels-riveted-or-welded-20180119085040394.htm

This one quotes a thread from this BBS with more details: http://forum.austina30a35ownersclub.co.uk/viewtopic.php?f=21&t=5193&start=45

On balance I think I'm going to stick with welded bearing in mind the state of the roads and my spirited driving.



Jeremy Cogman

Couldn't the riveted wheels be welded for extra security?

I think all mine are welded (not sure about the ones I sold to Guy?!) but I still wouldn't want to push them too hard. Probably being over cautious though, with standard tyres they would probably be fine for normal road use.
John Payne

John, I cannot remember how many you sold me. At the moment I have 3 welded and 2 rivetted.
But is it the change from rivets to welds that makes them stronger, or the other changes that were introduced? Where exactly do they fail?
GuyW

Cracks emanating in the brake adjustment holes seems a common, if not the only, failure mode.

The rivet is a indication of the weaker wheel not the cause of the weakness. I have yet to come across a documented case of the rivets failing and the rim separating from the centre (despite what I said in my first post, either I misremembered or I'm full of sh*t, take your pick!)
Jeremy Cogman


"The rivet is a indication of the weaker wheel not the cause of the weakness. I have yet to come across a documented case of the rivets failing"

Thanks Jeremey. It will be good to remember at the moment the wheel disintegrates that it's not the rivets! But it maybe suggests it's worth keeping a good check on the adjuster holes, to spot the begining of stress fractures before they develop
GuyW

This thread was discussed between 09/06/2021 and 10/06/2021

MG Midget and Sprite Technical index

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