Porous Speedlines

scarecrow · Post by **scarecrow** » Mon Nov 29, 2010 9:38 pm

I've discovered why my fuel consumption dipped below 40 mpg last week, and the power steering became very heavy. The front o/s tyre went from 30psi to 11psi over a 2 week period. The n/s was at around 25psi.

I'm told this is due to the alloy becoming porous - anyone know of a quick fix? I was going to put a couple of new tyres on, but I don't want to buggar them if they're going to go flat because of the wheels.

Cheers

MULLEY · Post by **MULLEY** » Mon Nov 29, 2010 10:15 pm

I had a tyre regularly losing air, so took it into my local tyre fitters who diagnosed the alloy wheel was causing the problem. They just took the tyre off & they cleaned up the alloy wheel, put some sort of bonding stuff around where the issue was, refitted the tyre & it was sorted. 3 years later & all is well.

Vanny · Post by **Vanny** » Mon Nov 29, 2010 10:29 pm

I'd expect a problem of corrosion around the sealing ring the casting goes pourus, are you sure the tyre doesn't just have a poor seal to the rim?

scarecrow · Post by **scarecrow** » Tue Nov 30, 2010 12:43 pm

I'm not sure at all - I guess there's only one way to find out. Fork out for a new tyre

Post by **Defender110** » Tue Nov 30, 2010 1:39 pm

Porous alloys did used to be a common problem, the leak on a porous alloy was not a problem of the tyre sealing ring but the actual cast alloy being porous through the rim. a cure for this was to clean the complete internal rim and apply etch primer followed by paint or varnish to seal the alloy. GKN alloys on Lotus Elites /Eclats used to be absolutly terrible for it.

Post by **Tim Leech** » Tue Nov 30, 2010 1:56 pm

When I had the alloys fitted to the GT which had been refurbed I found the next day they had all gone flat

Took them back in, they cleaned up the mating edges of wheels and used some bead sealer, 3 years later they are still holding 30psi.

I expect doing the same will cure your problem.

MULLEY · Post by **MULLEY** » Tue Nov 30, 2010 5:55 pm

scarecrow wrote:I'm not sure at all - I guess there's only one way to find out. Fork out for a new tyre

Why don't you take it to a local tyre fitter, they can diagnose whether its the rim in seconds, that way you might not have to fork out for a tyre which wont cure the problem anyway if its that in the 1st place....

scarecrow · Post by **scarecrow** » Tue Nov 30, 2010 6:10 pm

MULLEY wrote:
scarecrow wrote:I'm not sure at all - I guess there's only one way to find out. Fork out for a new tyre
Why don't you take it to a local tyre fitter, they can diagnose whether its the rim in seconds, that way you might not have to fork out for a tyre which wont cure the problem anyway if its that in the 1st place....

Thanks. I'll get them checked then.

I had a plan to put the Speedlines on the 14 when I put it back on the road - but I'm a bit worried that the steering will be too heavy as a result. Anyone tried this?

Cheers

MULLEY · Post by **MULLEY** » Tue Nov 30, 2010 6:15 pm

I presume that you'll be fitting 185/60's? if so then i suspect that the steering will be tougher than the narrow 165/70's that are normally on?

scarecrow · Post by **scarecrow** » Tue Nov 30, 2010 6:23 pm

Ehhh, I will have to join you and presume that is the size tyre I'll be fitting. I think Oscar said they might be a bit wider than usual. I'm not looking until the morning though - it's been snowing and I'm a great big Southern Jessie

MULLEY · Post by **MULLEY** » Tue Nov 30, 2010 6:59 pm

If there's plenty of snow & ice, then your steering will feel nice & light regardless of the tyre size

saintjamesy89 · Post by **saintjamesy89** » Tue Nov 30, 2010 7:19 pm

scarecrow wrote: I'm not looking until the morning though - it's been snowing and I'm a great big Southern Jessie

Your a Southern Jessie Scarecrow? How southern? I bet im WAY more of a Southern Jessie than you are!

scarecrow · Post by **scarecrow** » Tue Nov 30, 2010 7:39 pm

saintjamesy89 wrote:
scarecrow wrote: I'm not looking until the morning though - it's been snowing and I'm a great big Southern Jessie
Your a Southern Jessie Scarecrow? How southern? I bet im WAY more of a Southern Jessie than you are!

Manbags at dawn will settle this

Oscar · Post by **Oscar** » Tue Nov 30, 2010 8:32 pm

I told you the rims were a bit porous when you bought it, you must have not been paying attention in all the excitement.

I've long resigned myself to putting some air in every week - part of my weekly checks.

When I asked the tyre factors they said that 5psi per week was too low for them to do anything about. Sounds like it's progressed a bit since then. The tyres are new-ish, I hope they can sort the rims.

DavidRutherford · Post by **DavidRutherford** » Tue Nov 30, 2010 8:38 pm

Oscar wrote:When I asked the tyre factors they said that 5psi per week was too low for them to do anything about.

Pish pash! If they wanted to find that leak, they could have. You simply immerse the entire tyre and wheel assembly in water and look for the stream of bubbles. Even a loss of 5psi a month will show up.

99% of "porus alloys" turn out to either be corrosion at the tyre lip seal, or a leaking valve.