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MG Midget and Sprite Technical - Am I destined never to get on the road

Just set carbs and finnished a few bits ready for MOT rang and arranged one ,Thought I would just give it one last looking at and went to check all wheel nuts and one snapped off!So had to cancel MOT and ordered new wheel bolt.Also when setting off from stand still there is a slight judder through the steering only there if you set off fastish rest of time seems ok wondered if slightly scored disks might be the problem.
mark 1500 Lights on at the end of the tunnel

wheel studs can go when overtightened - again the Driver's Handbook is you friend here as it tells you the torque is 44-46lbs and not 70lb as most garage and tyre places will torque to out of habit

other thing does sound a bit like it could be disc/pads/callipers but it could something else, perhaps something needs tightening

if you're pulling off quick then the front will slightly lift a bit so that might be a clue, jack the front just enough to replicate this effect and have a look , pull and prod around

I always grease up the front suspension just before the MoT and have had three mentions of play over six years on one or both kingpins but only once in consecutive years and nothing this year
Nigel Atkins

I know your pain, some days just grind with dis appointment

Unless the shudder at take off is significant, i wouldnt get to excited...just note it, and track it to see if it gets worse.... a shudder like that, it could be anything, from fuel pooling in the intake manifold, a slick spot on the clutch to a worn tooth in the rear diff, to flat spots on the tires

Prop
Prop and the Blackhole Midget

bolt looked half through and it snapped below 44lbs as was using torque wrench, noise comming from drivers side and disk is faily scored would definitly be atleast an advisory, ordered new disks as i would prefer to solve problem before MOT.Had a prise round with jack handle and nothing seems to move on front end while in the air.

disk looks like on old 45 rpm single
mark 1500 Lights on at the end of the tunnel

Just curious about the special bolts on hubs what are the markings on the top for. I wondered if they are for tell tale markings so you can tell if they are coming loose.

mark 1500 Lights on at the end of the tunnel

pic of disk

mark 1500 Lights on at the end of the tunnel

it was the bolt and not the stud that snapped then, different

not that I know anything about it but that disc doesn't look good and wouldn't have been pleasing to an MoT tester's eye

if it's like that then would you not also replace the pads (even the Mintex 1144 aren't expensive)

Nigel Atkins

Managed to get the hub off then, without disintegrating the WB?

Just now finished a R&R on a rear disc hub on a 205GTi Bearings came off cleanly together with the hub with a puller. Just 1/2 hour to complete the job, - much quicker and easier than when leaving half the thing behind as with a Spridge!
Guy Weller

it was one of the splined stud that snapped i was just curious about the bolts. PO fitted new pads and I thought i would suck it and see with disks but looks like i was wrong.
mark 1500 Lights on at the end of the tunnel

I had stud go on my previous Spridget when a tyre fitter over torqued, I just shook my head at him and went across the road to the Rover (ex BL) dealership and thought I'd buy two, the amount they charged then was probably a lot higher than now, I wouldn't have the tyre fitting company company off so easily if I'd have know it was more than a couple of quid

with my present midget I done the same as you just tightening as normal and it snapped, I thought of all the places the car had been where the nuts were put back on as I knew I've never over tighten

Nigel Atkins

Nigel....Ha ha ha!

What about the time you loosened your king pin bolts!

They must have loved that one at the MOT! :-)


Steven Devine

The markings on the top of the bolt are an engineers code it tells the bolts specs to those that can read it

As to the studs... they are on avg 40 years old, sooooo nothing last forever....im sure over tightening was the cause, but metal does fatige with time and the common forces of life

I agree... new disk and pads both, using the old pads even if there recent new with that disk was a mistake

Prop
Prop and the Blackhole Midget

Mark,

Does you car have Rostyles fitted now or in the past. Years ago I found most Rostyle wheeled cars I checked had the studs bent inwards, likely due to over tightening at some point deforming the wheel, and one hub I checked showed most of the studs were cracked on the outside, most likely due to the bending. I changed all the studs to be on the safe side and with alloys fitted the studs stayed as intended.
David Billington

its interesting that the tightening torque for Mk1 Sprites is 37-39ftlbs. yet later cars with the same hub nuts and studs go up to 44-46ftlbs.
Bob Beaumont

Got to ask what determines the spec for how tight wheel nuts should be - and Nigel,I don't mean where does one look this up! ;-)

They need to be tight enough that the cone or bevelled face pulls the wheel into position as the centering accuracy is dependant on the bolts, not a concentric central flange like a modern wheel.
They need to be tight enough that they don't vibrate loose.
What else? Clamping pressure? but why? And they are not stretch bolts either - or at least they are not intended to be.

I cannot see why the bolts should need to be unduly tight at all. Other than perhaps a sort of gut feeling safety margin of "good and tight", so let's give the wheel brace an extra grunt or two for good measure.
Guy Weller

I wonder if radial tyres put more stress on the wheel hence the need for tighter nuts? The Mk1 would have used crossplies whereas later cars would have radials. I wonder when the spec changed?
Bob Beaumont

The 6 radial lines on bolt head means it a grade 8. When I did my new disks I just got some new gr8 ones
Andy Phillips (frankenfrog)

OK, The Brain Cell has been working. Clamping pressure IS important. Not because the wheel might fall off otherwise, but because the 4 wheel studs are in shear when it comes to transmitting the driving and braking loads. Its not so much the lateral thrust on the wheel from cornering - the studs are in tension for that. But the bolts are also in shear, and the clamping pressure is to maintain a good contact and friction surface between the wheel and the hub/ drum to transmit all that horse force.

This could be why the torque spec was increased between the 950cc and the later engined variants. Not more lateral loading, but certainly more wheel torque to transmit.
Guy Weller

Keep going Mark.
At some point you need to get it to MOT when you are determined to fix the bits that may fail to get it through in the retest period. (Known list and self pressure)
And getting it through is the aim.
Once it is MOT'd you can then gently test drive it and fix it until its fit to use as you would like . (A controlled testing and fixing period if you like).
Then you can get any other things done or upgraded as you want or as they happen.

Btw if you ever get to the end of that testing period then let me know how you did it ;-). But getting it all perfect is not where its at if you are going to use the car.

Cheers, Dave
Dave Squire

Interesting Guy... As a counter... The maximum torque you can put through a wheel is the torque required to make it lose traction and wheel spin. The engine power increased but this limit would be the same as the tyre grip would still be the same. Taking it to extreme, the wheel studs could take 1000 horse power and be ok, because 1000 horses through 145 tyres would just result in lots of tyre smoke!
M Le Chevalier

surely as engine size increases so dose weight of car so more torque required to spin wheels due to increase in car weight
mark 1500 Lights on at the end of the tunnel

Guy Weller,

Got to ask what determines the spec for how tight wheel nuts should be - and Nigel,I don't mean where does one look this up! ;-)


Its the 16 year old high school drop out kid, at the tire store that determines this spec....how he determines it , he says to his buddy, I bet I ca torque thise nuts to over 300 psi without busting one....his friend smokes the last of there weed, and says dude... your so on

Now you know why insurance companys dont allow the general public in the shop

I dont get it, I dont... what with tire guys and air impact guns loading the wheel nuts to a 1000 psi, do they get paid a bonus for each broken wheel stud

Prop
Prop and the Blackhole Midget

Yeah Mark, I suppose if you had an engine big enough to put out 1000hp it would weigh a wee bit more than an a series!

In a theoretical world, or even with the a series, you go from 950cc to 1300cc with the associated power increase with no increase in weight.

If you put in a big heavy v8 then you could increase tyre pressures to compensate! :-)

Not trying to be obnoxious here BTW. Just friendly engineering "debate".

Mal.
M Le Chevalier

Sure you can shoe horn in a huge V8, but where are you going to put your feet to drive the car

Prop
Prop and the Blackhole Midget

Lets face it....Those studs were inadequate to start with.or

Who would ever let that situation leave the factory as is?

A few years back the old president of our local mg club snapped two studs off on a high speed run to Vermont.

He was about on hour and a half from home.
Minilites were on the car so I just put it down to over torqueing. The replacement studs got wiped out on the way home.Scary how under engineered they seem.

When I drive a midget they stay on my mind!

http://www.youtube.com/watch?v=2A7iuQF_tAc
Steven Devine

Quite a few years ago there was a long-running discussion on the Spridgets Autox.net discussion forum - which was very largely USA based. It was apparent that at that time it was common practice in the USA to drill out and fit thicker diameter wheel studs - going to the next size up. A pretty easy modification I would think, but have never seen it discussed since then- and that was maybe around 1997?

Minis - at least the early ones - suffered the same problem of weak wheel studs. I remember very clearly when I sheared off a front wheel stud on my mother's brand-new Austin Mini Countryman, just using the supplied wheel brace. The car we owned was one of the early ones off the production line, bought around January 1961, so I was just turned 12
Guy Weller

I put the larger studs in mine. Just looking at the original ones was enough to scare me.

Charley
C R Huff

7/16 inch...

yepp, when I do my front end rebuild, ill be doing that mod as well, in fact because my hurricanes are slotted I may push the PCD out just a bit also from 4 inches to a 5 inch PCD, id think that would make for a stronger attachment

Prop
Prop and the Blackhole Midget

Look for threads by...

David "fill in this space" leib

I know he talked about using the 7/16 inch studs on several.occasions I think maybe even Bill young did as well

I miss Bill young... hard to belive he left us ....he was a good friend, and I wish him well in the after life.... when he retired, he had so many cool plans and ideas he wanted to persue...hard to belive he had to go so quick and the way he did... what a waste

Sorry... ive been thinking of him alot lately

Prop
Prop and the Blackhole Midget

This thread was discussed between 05/06/2014 and 09/06/2014

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