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MG Midget and Sprite Technical - Rear axle widths

Is it possible to use a wire wheel back axle and convert it to bolt on wheels? Would this axle then be slightly narrower and allow more clearance for wider rear tyres within the rear arches. If so are there tougher halfshafts available for this conversion?
Looking to do this on a later sprite with squared off rear arches. How much extra space could I gain .

R Mcknight

I suspect that all you would achieve is to swap the tyre contact problem from the wheel arch area to contacting the leaf spring.
How wide tyres do you want to go to? You can generally go as wide as 165/65/13 on a square arch car, with a bit of manipulation.
Guy W

Just thoughts really. Mine are second user 165/70/13 tyres from when I was just getting it on the road last year. My local new tyre man (who is generally very good) says put 165/80/13s on next time as that's what he puts on for other midgets in the area. The rims are standard rostyles and its SWA. So presumably the width of the 80 on a standard rim is considerably less that if it went on a wider rim that might catch the suspension?

Is there any rule of thumb about tyres and rims or are we back to going with recommendations as tyre manufacturers keep changing them?
Dave Squire

Roy: if you swap the axle you would probably have to shorten the halfshafts by 1/2" which in practice would mean remachining the spline at the diff end to make it run further up the shaft.
Graeme Williams

The polished bits on our springs testify that inner clearance is minimal too! With 175-65's it just contacts the spring on hard cornering. With 185's it also polishes the wheelarch with the outside of the wheel, so i'd say that it's slready quite centred.

However, that depends on the offset of the wheel you use. The above results are with disc wheel axle and 105mm backspace on 5.5" rims.

If you go for a wheel with 1/2" more offset to the outside, then you would be fairly centred using the wire wheel the way you propose, and would save the hassle of changing axles.

There are several halfshaft upgrade options, it would pay to check the archives. Nearly all halfshafts have sufficient spline that you could lob off the extra 1/2" or so on the very inside to get the shaft the correct length. Might be a little more that 1/2", memory just wen't blank on the exact amount - it would pay to check.
Paul Walbran

On a mates Austin sprite he had issues with rubbing with 185/60 13 tyres even with slightly jacked out and relieved arches. The rims were Jensen Healey alloys and 5.5" width from memory, no idea of the offset. I built him a Watts linkage and all the rubbing problems went away and the handling improved.
David Billington

Dave, my modern has a watts, great things, any chance of a rough spec? include my e-mail above if that helps.

Dave Squire

some manufacturers (subject to their published figures being correct of course) publish a range of recommend wheel widths for their tyres (see Toyo tyres UK as an example) and they can vary because the tyres vary - tyres are very complicated components

remember quoted sizes can be nominal, see the Toyo specs

(unless I misread your post, very possible) I think you might be getting a bit mixed up about the tyre ratio and the relationship fit to rim widths see here -

Nigel Atkins

with my bolt on wheel axle and 175 70 13s on KN minilite copies I can get rubbing on the spring even with 5mm spacers on the back. Though that's thrashing it in the dry.

Assuming the spring attachment points are the same distance apart on both axle types, then you're likely to have less clearance for a wide tyre with the narrower axle. Personally I'd rather they caught a bit on the outside where you can see them, rather than the inside where you can't..
Rob Armstrong

I have seen the spring rip the inside wall of a tyre - though on Mk1 1/4 elliptics and during severe autotest manoeuvres. But consistently, until a panhard was fitted ... cost quite a few tyres!
Paul Walbran

Hi Nigel, Just jumped in on wrong tack for the thread, that's very useful though, Thanks.
Dave Squire

Hi Dave,
I've put the link up many times before but if you've not used it the following link will help demonstrate nominal width sizes (an example tyre only)

from the link that follows click on the 'Sizes and Specification' tab and you'll see 'Overall Width (mm)' and compare with stated width and see the column 'Approved Rim Width Range (inch)' -
Nigel Atkins

This thread was discussed between 17/09/2013 and 18/09/2013

MG Midget and Sprite Technical index

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