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MG MGF Technical - Leaking rear wheels

Am I being sold a line by my local tyre people.?

They changed the back tyres on my MGF some time ago. At first no problem but then I noticed the wheels lost pressure slowly. The tyre company re-seated the tyres but then after a while the pressure loss returned.

Tyre co said it is the alloys that need to be replaced as they are porous and also said that it is not possible to fit inner-tubes.

I have no problems with the front tyres so suspect it is the backs moving slightly on the wheels.

Can inner tubes be used?

If the wheels are porous can they be repaired?

Thanks for your help, John
John

Yeah apparently OE MGF wheels do get porous over time... the same has happened to mine - mine were at a point where they lost 20lbs of pressure in a week - but it gives you a good excuse to get a nice shiny new set of TF Wheels!!

Or you could take off the tyres, paint the insides of the wheels with hammerite and that, Im told, should cure it.

Or get them professionally mended... at about £50 per wheel apparently...

Dont know about inner tubes sorry!
Nick D

Hi John,

Low profile tyres and inner tubes don't mix well, and your current tyres were designed to be tubeless so either making your current rims airtight or replacing them are definitely the better options.

Which style wheels do you have? If they're the standard 1.8i wheels (six spoke) then a browse of eBay might turn up a bargain or two. Full sets with half decent tyres have been known to go for just a few beer tokens.
Mike Hankin

You mustn't put tubes in tubeless tyres, a real no-no - cheapest thing is to smooth hamerite the insides and go from there. I have done this in the past and it was a complete cure. There was a thread about this around a month ago so maybe check the archives.
Tony

Had the same diagnosis by tyre fitters. However when the the rims were carefully and properly cleaned no leaks and over a year on now. It takes time to do the job properly.

If your wheels were porous why did reseating the tyres temporarily solve a porousity problem?

Porous wheels? What structural change takes place in the material and why? Does anyone know?
Ken Waring

Ken alloy castings can be porous from the outset although most wheels are likely to be low pressure die cast and suffer less. Any porousity present should be sealed by the paint or lacquer coat but this eventually starts to break down allowing leakage. Having said that I think the main cause of this type of problem is corrosion around the bead or valve allowing leaking as the alloy will corrode in the presence of moisture and salts once the paint, if any, deteriorates. I had this on a set of alloys on my sprite and took them to a good tyre place that put them on the balancing machine and wire brushed the bead area thoroughly, that cured the problem for many years although it has no recurred.
David Billington

That makes sense. Good job the same people don't make pressure vessels then, or do they???
Ken Waring

What we did on the race cars was to paint the inside of the wheel with a clear laquer - cures the problem straight away.
Deborah Evans

Thanks for all of your inputs. Think I'll try a repair first.
John

This thread was discussed between 21/09/2006 and 25/09/2006

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