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        General >> Problems >> porous alloys?
        
(Message started by: bigmaltwo on Dec 19^th, 2004, 2:13am)

Title: porous alloys?
Post by bigmaltwo on Dec 19^th, 2004, 2:13am

ever since buying my (r-reg) 2.3 ultima this spring, the tyres lose air each week. my local tyre bay has had two of the boots off and sealed the rims. this has helped, but they reckon that the rims have gone porous. they are the 16" jobbies. does anyone know if tubes are available for this size, or will it be a refurb job? It only seems to happen whilst standing (being as i drive a breakdown truck for 4 days out of 6, she just sits on my drive gently deflating)! in use she seems fine??
dunno which will give out first, my hair, or their air!!!
anyone else had this prob?
thanks.

Title: Re: porous alloys?
Post by johnv on Dec 19^th, 2004, 8:24am

About two years ago, on a site like this on AOL. someone said that his Alloys had gone porus.
Everyone started to call him a idiot, how can metal be porus, they where saying.
I alway throught that it could not be the alloys being porus.
if they are indeed porus could not you paint them on the inside to seal them.
I myself would not paint the outsides, but I seem on Ebay in the past, alloys that the owners had painted black.

Title: Re: porous alloys?
Post by johnv on Dec 19^th, 2004, 8:30am

are you sure that its not the rims are indeed the trouble. Most of these lads that work in tyre bays could not care less about what they do.
Its tyre off and tyre on, no looking at the rims. I had in past years, tyres even on metal rims loosing pressure because of dirt on rims.
I alway stand over them now and I lay down the law and instruct them on how to correctly fit tyres.

Title: Re: porous alloys?
Post by Richard on Dec 19^th, 2004, 9:43am

What wheels do you have and what type of valve do you have fitted ?, Also what state are the wheels in ?,
If there is corosion around the rim this will cause pressure loss, If they are chrome sometimes this chrome can come off and get caught in the bead and cause pressure loss, If you have bolt in valves these can become loose and cause pressure loss, Are all the tryes deflating at the same amount of pressure through the week ?.
What you have been told about your wheels being porous is bollocks.

Title: Re: porous alloys?
Post by johnv on Dec 19^th, 2004, 12:56pm

That's what I throught, but I would not have put it so strongly. I mean how can metal be porus, wether steel or alloy.
Like Richard says. check valve and there rubber washers, then look for nails,screws or flints in tread and in-between treads, then its tyres off and clean rims real nice use some metal polish.
I lucky to have a set of four alloy wheels spare in my out house.
When I go for tyres, I take these without the tyres and I have cleaned them all nice, ready for tyres to be fitted.
Did you know that if you do this instead of having your car put on a ramp the new tyres are much cheaper in price. Well they are are my outlets. Its because they don't have to use up a ramp and remove wheels, they can get straight on with the job.

Title: Re: porous alloys?
Post by waders on Dec 19^th, 2004, 2:30pm

Sorry to be the thorn guys, but I used to be a professional motor cycle race mechanic and alloy wheels can be porous I'm afraid. They have a sealing coat on the inside which can break down with age, heat, excessive flexing or just bad finnish to start with.

(we would use a rubber solution to re-seal them)

8) ;D 8) ;D 8)

Title: Re: porous alloys?
Post by Dave Boulton on Dec 19^th, 2004, 2:32pm

I had this problem with my last car (a Granada Scorp). The local tyre & wheel "specialists" said I needed new wheels :-/

The local back street garage got an apprentice to rub down the rims with very fine glass paper and solved the problem! Apparently you get a very fine layer of corrosion that builds up over a long time and it is porous. Get rid of it and the tyres can seal properly to the wheels again. That was I was told and it did fix the problem so worth bearing in mind maybe.

HTH,
Dave

Title: Re: porous alloys?
Post by Richard on Dec 19^th, 2004, 3:01pm

Waders, Trust you to come up with a rubber story.
But as Dave says about the corrosion between the tyre and rim, this is normally the cause as water gets in here and will cause the problem you are having, But i would check the other options in my previous post aswell.

Title: Re: porous alloys?
Post by mr._floppy on Dec 19^th, 2004, 3:18pm

Would Engine designers use alloys in the production of engine blocks or cylinder heads if they tended to become a bit porous?

Verrrrrrry Interesting .

Title: Re: porous alloys?
Post by Richard on Dec 19^th, 2004, 3:27pm

As i said BOLLOCKS.

Title: Re: porous alloys?
Post by waders on Dec 19^th, 2004, 3:52pm

If my wheels are made of the same alloy as my crank cases, then I'd be worred :o.
First hard corner and no more round wheels :'(!
Worst offender for "air bleed" are magniesium based alloy mixes (real race wheels), and yes out with the rubber again :P

http://tinypic.com/xt9jt

Me at work, Estoril 2001 world endurance c/ship.

But I didn't say he couldn't have a rim leak!!

Title: Re: porous alloys?
Post by waders on Dec 19^th, 2004, 4:17pm

On reflection, even after what's been said on this thread before, I cannot see a vehicle manufacturer (car or bike) using a porous material to make their production wheels. The only experience of 'breathing' wheels I can honestly say has only been with aftermarket full race wheels.

Rim leak.

8) ;D 8) ;D 8)

Title: Re: porous alloys?
Post by Richard on Dec 19^th, 2004, 4:26pm

Waders, Which one are you in the pic ?, And call yourself a race mechanic ::), I mean just look at that rear tyre :D, It is as bald as my head,lol.
P.S. We don't want to go onto rim leak ;D.

Title: Re: porous alloys?
Post by waders on Dec 19^th, 2004, 4:33pm

I'm the one with the shades! Oh, long hair, beard.

And yep, thats one slick, slick 8)

8) ;D 8) ;D 8)

Sorry for making the page so wide.

Title: Re: porous alloys?
Post by johnv on Dec 19^th, 2004, 7:21pm

Hey, they have forgot to put the tyre on that back wheel. There is only the inner tube there, they won't get far on that.

Title: Re: porous alloys?
Post by waders on Dec 19^th, 2004, 8:22pm

Oh no, you meen that the floppy rubber thing with the valve in it wasn't a slick tyre........... :P

8) ;D 8) ;D 8)

Title: Re: porous alloys?
Post by dart on Dec 19^th, 2004, 8:52pm

And I'd just like to say bollocks! because I can without it being censored!nice one Richard! ;D ;D