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MG Midget and Sprite Technical - Sprite floor dimensions

Or...Is my bottom too big?

I was about to fit new floor panels to my Frogeye but checking the dimensions there is something not right. I think I need to make some adjustments before welding in the new floor panels.

The shell I have has had some PO botched repairs in the past, including replaced floor cross members, and the two sides don't match. One measures 18 3/4" the other 18 7/8". I probably should have cut these out first as they cause the sills - which I have replaced - to splay outwards towards the rear. The between the sills measurement is 48" at the front and 48 1/2" at the rear.
(measured to inside surfaces of the inner sill panels)

The chassis rails at the front are parallel and 11" apart as measured between the flanged edges and I think they are correct.

Maybe the sills are supposed to splay outwards towards the rear by 1/2" but on mine the "repaired" cross members seem too long (and unequal anyway) so that the sills bow outwards slightly. It isn't discernible to look at, but measuring shows up the fault.

What I need is some kindly person with access to a Mk 1 Sprite - preferably an unrepaired shell - to check the underside measurements as shown on my diagram. My measurements are to nearest 1/8".

A task for a wet Sunday afternoon, if anyone can help.

Guy





Guy Weller

isnt it supposed to be the same dimensions as your midget Guy?

Except for the stiffeners along the rear floor area I understood them to be the same floor and sills

If not, wow, another live and learn...
bill sdgpm

Hi Bill,

It could be.
But a) my '71 Sprite isn't here at the moment as it is locked away at a workshop where I am doing the respray work.
And b) I rebuilt the floor on that and may not have got it right anyway!

So I could really do with dimensions from an unmolested early car. My suspicion is that the sills are supposed to be parallel at 48", and not splayed out to 48 1/2" at the back. And that these unequal cross members must definitely be wrong!
Guy Weller

But the tunnel isn't parallel is it? It flares out on the left side, so the crossmembers could be uneven...
Alex G Matla

You are right about that Alex, but the measurement I have taken (see diagram) is on the underside, from the sill to the inside edge of the flange of the front chassis rails, so the tranny tunnel becomes irrelevant.

If the sills were parallel, then this dimension would be 18 1/2". Mine are 18 3/4" and 18 7/8"

If the sills should splay by 1/2" towards the rear, then these two dimensions should both be 18 3/4"


Guy
Guy Weller

Hi Guy

I have measured my shell which is an early heritage example built 20 plus years ago. At that time heritage shells were not great however here is my measurement

The sills are parallel between the axles and the measurement between the bottom flange is just shy of 48.5 inches
Robert (Bob) Midget Turbo

Rob, That's helpful - and interesting. Assuming that is accurate (not your measuring, but the early Heritage shell) then mine is pulled in at the front of the sills by 1/4" each side. That will have been me then, when I fitted them. I am inclined to leave that though as I cannot see that it makes any real difference other than the front of the sill having slightly more "tumblehome" than they should!

Still bothered about the inequality in the region of the cross member though, Can anyone provide any confirmation measurement?

Guy
Guy Weller

OK I'll measure Lara tomorrow

Only 'cos it's you

:-)


bill sdgpm

Thanks Bill.

What I need is the measurement taken across the underside of the car between the sills, in line with the leading edge of the box section cross member. To be consistent the most accurate would be between the inner faces of the inner sills, where they drop down just below the floor pan.

To compare one side with the other I measured as above, but to the inner flange of the fore & aft chassis rails from each side. This eliminates the centre piece - the bit that you have cut out - so should be 11" less than the sill to sill figure.

I had forgotten, but checking my construction notes from several months ago, when I was rebuilding the rear heelboard, Nick gave me some accurate measurements for that so the rear end of the floor should be correct.

Guy
Guy Weller

Well I have got to say I am disappointed with you lot on the BBS. A fairly simple request for help and after two days waiting no one (excepting Bob) can bother to take the time to check a couple of measurements for me! All too busy discussing t-shirts!

It isn't that hard, you only need to reach under the car just ahead of the jacking point, hook the end of a tape measure onto the inside of the chassis rail and read off a measurement against the underside of the sill. But then, if no one can be bothered then this BBS isn't the helpful community that I always thought it was..

Grumble, mutter, shuffles off, head down, dejected....

Bye.

Guy
Guy Weller

Guy
do you know how hard your question is!!

"What I need is some kindly person with access to a Mk 1 Sprite - preferably an unrepaired shell - to check the underside measurements as shown on my diagram. My measurements are to nearest 1/8"."

an unrepaired mkI shell?!
all of our's are busted up and welded back ;)
even if you would widen your search to anny shell it is a stretch

Sorry i cant be of more help but i know how much filler is on my sils so i would not trust my own measurements
Onno Könemann

LOL - mine is so totally far removed that it would help you muck it up more ... but if you really really wanted ... - then start a thread asking everyone their measurements - and don't say our bums are too big :P!
rachmacb

same here - my sills have been replaced previously - and Ive had to repair on top. My floor pan is patchwork. I could have +/- 1/2" side to side just depending on how much weld has or hasn't been ground down
Dean Smith ('73 RWA)

you said - "So I could really do with dimensions from an unmolested early car"
and you have a Frog - so does it have to be a quarter-elliptic car? cos that cuts most of us out... but if any shell will do then I can measure mine easily...
David Smith

Guy,

I could measure mine but it's not an unmolested example as so much off the floor was patched when I got it the I had to make a best guess, IIRC it was a bit over 48". I've got too much crap around it at the moment to get underneath easily but have a mates mk3 handy so may be able to pop a tape measure on it tomorrow. It has been a bit molested also but I'll try and see what looks original.
David Billington

Guy. I know that my mk3 Sprite is unmolested in the areas you mention, as I only had to fit full outer sills and part inner sills forward of the cross member during the restoration. The area at and behind the cross member has never been interfered with so should be just as it left the factory. I'll measure it tomorrow morning and try and get the results on the BBS at lunch time by nipping home from work for half an hour, by which time someone else will probably have done it anyway. But if they do, at least my measurements will confirm theirs. BTW. I'm sure Bill is correct in thinking that in most respects they are all the same as regards general construction dimensions.

Bernie.
b higginson

Guy, my Gan3 Midget with original floors and inner sills is 18.5" from inner edge of chassis rail to sill inside edge. I can only get to one side. I now have EP90 on the end of my best tape and underseal all up my arm! - Cheers Mike
m fairclough

where's that grumpy old git?

I was so busy painting the bum end of mine to day I forgot

SO--- tomorrow

but Lara isn't unmolested you know

Her only original bit is the tunnel...
bill sdgpm

Grumpy old git is here Bill. ;-)

Thanks to Bob and Mike for providing measurements, and to Bill - forgetfulness I can accept!

Thanks to Bill for also pointing out in the very first response that the shells are all the same so measurement of any later model would have sufficed.

I had hoped to get a number of measurements which would have shown up what degree of tolerance there exists - I suspected some variation even on original shells. It might have been usefull information to others replacing floors or cross members, although I accept that the Archive is a unknown dark place that few venture.

Anyway, with the measurements provided by Bob and Mike I can now make my own judgements about my floor. So thank you, I don't need to trouble anyone else for further grovelling under their cars.

I am now taking some time out from this BBS to hopefully make better progress on my two cars.

Guy

Guy Weller

Guy. As promised, I measured mine this morning and the results are as follows:
Inner sill to inner sill, front and back 48 inches.
Inner edge of chassis rail to inner face of inner sill1 18.5 inches both sides.
Between chassis legs 11 inches.
As I said, my car has not been changed in these areas so it's as it left the factory.

Hope this helps.

Bernie.
b higginson

Bernie,
Thanks, you have mail.

Guy
Guy Weller

This thread was discussed between 04/07/2010 and 06/07/2010

MG Midget and Sprite Technical index

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