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MG Midget and Sprite Technical - Help - tyre width

Hi All,

I've got 14" 5.5J alloy wheels on my round wheel arch car. For the last few years I’ve been using a set of Yoko A539's 185/50/14. I always felt that the rolling radius was a little small so when buying new tyres last week I went for 185/55/14 Dunlop sport 01.

Turns out that despite both being the same width, the Dunlop is wider and particularly bulbous at the tyre wall. Subsequently my tyres now rub the leaf springs on the rear (see images), and also the lip on the outer edge of the front wing. Full width of the tyre is 190mm at the widest part (see photo with calipers). I already use a 1/4" spacer on the rear, I think its also touching the lip on the rear wing on bump.

Is there anyone using 185 tyres that could take this measurement, I think I'll buy new tyres, I just don’t want to waste more money on a different make that turn out to be the same. I'd be particularly interested to know the width of Yoko A048...

Hope that all made sense, thanks in advance

Richard.



R T Jakeman

also


R T Jakeman

and


R T Jakeman

finally, front of spring


R T Jakeman

Jake,
My guess is that part of the problem is that the taller profile results in a little more bulging of the side walls (55 viz 50).

But quite apart from that I found when replacing some tyres a few months ago that exactly the same sized tyres from different manufacturer, they were in fact different overall widths. The tread contact area was fairly close bur when measured as in your photo my replacement tyres were a good deal wider across the tyre walls and in my case rubbed on the outer wing. I went back to the tyre depot and complained as I believed it was their responsibility to check that the tyres fitted correctly. They eventually agreed (even though I use something different to the manufacturer's recommendation), and replaced with a different make which didn't contact.
Guy

even 175 048s will touch the leaf spring under race conditions which is why most use RWA shells and wheel spacers...
David Smith

I've just fitted 185/60/14 -

Although not driven stationary spacing is well clear of the leaf springs - I think I opted for the pirelli brand!
They were cheaper than the budget brand??

Jon
Jon White

"even 175 048s will touch the leaf spring under race conditions which is why most use RWA shells and wheel spacers..."

Absolutely NOT true. We run 175/50 x 13 AO48R Soft Compound tyres on 5.5J rims as our Intermediates/Wets and have NEVER had an issue with tyres fouling the rear springs, with or without spacers.

We also run 71/2" Yoko slicks on 6J rims and, again, we've never had a tyre fouling problem.

Admittedly a SWA would cause problems with these but the Class C girls and boys running 175/60 x 13" AO48R on 5.5J rims seem to have no problems other than a little wheel arch seam adjustment on SWA cars.
Deborah Evans

My 048R 175/60 13's have about an inch of clearance to the spring (no spacers) normally but still touch the spring under hard use. I can't see how everything moves that much but it does. Never causes any problems though, well none that I know of.
John Payne

Deb, absolutely IS true - I am not in the habit of making things up and object to your assertion; I have the evidence here in my garage if you would like to see it. Obviously I'm not saying they ALL do on EVERY car - I only speak from my own personal first-hand experience.
David Smith

Not just me then.

Staticaly there is probably 10mm of clearence to the leaf spring. I am surprised there is that much movement so far away from the contact patch though. I have transverse location (panhard) but nothing longitudinal.

Maybe i'll have to go back to 185/50.

Jon, I think you might have problems, depends how hard you want to corner..
R T Jakeman

David, you made a GENERALISED statement about ALL race cars which I SPECIFICALLY refuted. Furthermore you stated that most racers are RWA and run spacers (they aren't/don't). By far the largest contingent in the MGCC midget Championship are Class C cars and they are predominately SWA.

As I stated, our cur, running WIDER tyres without spacers doesn't have an issue. Why? Because I set it up properly.

If you are going to make such broad brush statements don't get pissy when someone pulls you on them!

You may not like my assertion (tough) and you'll like this even less.

I will reiterate:

A PROPERLY set up Midget racer running 175/50 or 175/60 x 13 Yokos should NOT have issues with tyres fouling the springs.

ERGO yours is NOT properly set up. Either you have the incorrect offset on your wheels or you are not controlling the sideways movement of the live axle correctly.

I take it you have a Panhard rod. If so, and you are getting fouling, then it is not doing its job correctly.
Deborah Evans

Deborah,

Does any of the issue with fouling or not have to do with Richard using 14 inch wheels while you are using 13 inch?

Charley
C R Huff

I never said 'all'.
I wasn't confining my thoughts to the MGCC Midget championship or any other specific series, or even just the UK.
Don't assume I have a Panhard rod.
And by the way, where do you race?
David Smith

This thread was discussed between 17/04/2011 and 18/04/2011

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