Yokohama A-032R WARNING !!!!
Turbo Mini Forums

Hi Paneermeel, nice ancient post excavation......

Answer = "inconclusive"

They weren't prepared to say one way or the other and said I was the only person to have reported such a failure on that make/type of tyre.


So I gave up.

Unusual for me, but I did..... Bought some more and fitted them myself (with tubes as I don't have a beadblaster which is need for the mambas if you want them tubeless)

Schrödinger's cat - so which one am I ???

itresting rod, when i contacted Yokohama, they said I couldn't run tubes on the A-032's, so I went with the seal it up method on my force rims.

I presume you are happy with the tube solution?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Graham,

The tube/tubeless arguement comes up regularly on lots of forums.

Personally I would prefer tubeless but not for the usual arguement of the tube fretting/overheating/anything else inside the tyre. I think those arguements are crap.

The reason I don't like tubes is because any decent one has grooves around the valve stem and wheel to let the air out between the tube and tyre as it's being inflated. So if you get a puncture the tubed tyre goes down fast, the tubeless won't.

So I would prefer tubeless but, without a beadblaster, I can only fit them myself (on mambas which have a very wide center recess) with tubes.

So I'm not happy, but it's a balance of risk arguement....

Schrödinger's cat - so which one am I ???

could allways run some slime to help reduce the risk? well for a small hole?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Where i used to work, weve fitted tubes to tubless tyres for some old classic racing car... after umming and arring about it with the owner (another unit owner on site) they said apparently if you fit the tubes while generiously using talc powder between the tube and the tyre it stops some chaifing which is where the problems occur... if thats true though, who knows!

David.

arr just spent 10 mins reading the thread to find out it wasnt concluded!
ah well :)

Reading up on RTS Clutches

there is nothing wrong with a A-series that a turbo can't fix.

www.turbomini.nl

There is no way that the failure was caused during fitment, i can see why you pursued it. That is a poor show from Yoko they will have carried out rigorous design and testing of the A-032R especially as it is a performance tire, i guess they dont want to release this info. Unfortunately it is too easy for them to ignore it and we can just hope that it was a one off and that there are not others out there without the knowledge you have to question it.

Hi there,

First post on here... Drawn in by the tyre discussion (I have an XE Mini but don't hold it against me )

Intriguing failure, never seen one like it and I have cut up and examined (maybe not hundreds, but near 100 ) tyres over the years.

All of the tyre beads I am familiar with are made from one continuous piece of wire (As already mentioned) tightly wound into a former into the required configuration, such as 5 x 5, (5 wide x 5 deep) etc...

Instead of a single wire this bead construction seems to be made from 4 wires (wide) wound around 4 or 5 times (deep), I say 4 or 5 because if you look at both halves of the failure one side is 4x4 and the other 4x5 (4 wide x 5 deep).

Clearly this is the point where the bead wire was laid on the bead former - if you look at the photos the bottom 4 wires show no failure - because this is the cut end of the wire - hence no tensile cup / cone present, I cannot see clearly from the photos but the rest of the failures look like cup / cone as these were in tension. This would be the 'stress raiser' point/area in the bead due to the change in stiffness going from 4x4 to 4x5 – differential stiffness.

All of the Yokos I have cut up have been race tyres - they use a hexagonal bead design for these, say 4/5/6/5/4 in terms the number of wire configuration (so I have no direct experience of their road tyres), but again (as they should be) tightly packed, I have never seen a bead construction with such big gaps between the wires - the top layer of bead wires especially seems 'disconnected' from the rest of the bead body - but none of it closely packed.

Had to make two posts as one kept cutting the text in half (word limit?)

Edited by Aubrey_Boy on 23rd May, 2012.

My opinions...

I have burst test many tyres (race) and you usually have to be in the order of 12 - 14 bar before failure and even then plenty of failures are due to the actual wheel failing not the tyre. 40 psi (2.8 bar) should be fine all day long even just as a running pressure let alone the pressure to seat the bead. The bead wire would have to be chocolate or much more pressure (80 - 90 psi+) but even not fail the bead due to over pressure trying to get the bead on.

I have never failed a bead wire under any circumstances (20 years+)

Fitting damage? The bead wires failed at the stress raiser point - would be have to be hell of a coincidence for the fitter to kink the bead at the exact point where the bead wire ends/starts. Even then I have only seen tyres leak at the point were a bead is kinked and not fail as a result.

I know it’s long after the original post but hopefully of some interest, if it should be a 4x4 bead configuration (cutting other tyres of the same type would answer this if they were also 4x4) then check the wire physical properties – tensometer test to determine tensile behaviour of wire. If other tyres show it should be 4 wide x 5 deep bead configuration then a cock up manufacturing.

PM me if you interested in any further discussion

Cheers

Edited by Aubrey_Boy on 23rd May, 2012.