shredded tyres - the last straw!

[jd_hants]

OMG - I didnt realise how close the knobbly bit can be to the vreds - I think I'm going to have to get the angle grinder out asap!!!!

[Shoppinit]

I tried to take some photos of my knobbly bit but they're not very good because the car is on the ground so not much clearance. What we can see though is how rounded the PS2 R01 are on the inside. Bear in mind that my tyres are due for replacement, about 3mm tread left.

[bilko1]

I'm sure the knobbly bit is left over from the casting design like where the molten metal is poured into the mould, dosen't seem to have any impact on strength but i'm no expert.

[Digger]

As per DRC have our cousins across the pond managed to kick up a fuss or by some miracle are their knobbos non-existent!!?

[monoi]

Low pressure reduces the overall lateral stiffness of the tyre, so the whole tyre deflects sideways under lateral load - ie when cornering.

Dave

I got that, but unless the tyre touches the road which exerts a lateral force, it is not going to know that you are cornering at all other points and won't be deformed.

[bam_bam]

Low pressure reduces the overall lateral stiffness of the tyre, so the whole tyre deflects sideways under lateral load - ie when cornering.

Dave

I got that, but unless the tyre touches the road which exerts a lateral force, it is not going to know that you are cornering at all other points and won't be deformed.

Extremely good point Monoi, the tyre wall should only undergo deformation when entering and exiting the contact footprint. The infamous knobbly bit is at the furthest point from the footprint, ergo, no tyre deformation?!?!
I wish there was a tyre engineer still on this forum, he was awesome.
Did the OP mention what pressure these Vreds were run at? The problem could also be compounded as there is no way of knowing what the actual tyre pressure was at point of tyre failure against the knobbly bit. What if there was a slow leak present for the last xx miles?
An unbalanced wheel might cause the tyre wall to wobble but the OP made no mention of this.

TPMS all the way baby, they cost the same as a set of tyres to replace and now that seems like great value... I wouldn't be without them innit.

[Daveperc]

Extremely good point Monoi, the tyre wall should only undergo deformation when entering and exiting the contact footprint. The infamous knobbly bit is at the furthest point from the footprint, ergo, no tyre deformation?!?!

Sorry guys, but not correct. Think of the tyre and wheel as two concentric cylinders. The lateral force exerted by the road to change the direction of the car is applied to the tyre tread by the road. To transfer the shear force to the wheel (and car) the whole tyre tread is displaced laterally, deforming both tyre walls - the air pressure, and the deformed shape excert the force which is principally transmitted by changes in tension in the fibres in the tyre.

I'm not a tyre engineer, but I am a Chartered MechE .

Dave

[Shoppinit]

Nice explanation, Dave.

You can see it in action here:

http://www.youtube.com/watch?v=4lG2nNcYAtY

[Shoppinit]

THis one is even more demonstrative:

http://www.youtube.com/watch?v=W8UiE7yvO_M

[bam_bam]

Makes sense and I guess we want that sort of uniform rigidity.
Thanks Dave.

[Daveperc]

Thanks Shop - a picture's worth a thousand words - but I didn't have time to search!

Dave

[Mancmatt]

Did the OP mention what pressure these Vreds were run at? The problem could also be compounded as there is no way of knowing what the actual tyre pressure was at point of tyre failure against the knobbly bit. What if there was a slow leak present for the last xx miles?
An unbalanced wheel might cause the tyre wall to wobble but the OP made no mention of this.

I always ran at 40psi. Didn't use TPMS because it was useless - always relied on manual checks with an accurate guage.

It's important to remember that this was not specific to one wheel which could have been out of balance or with a slow puncture. The damage was to both front tyres at the same time. It wasn't quick - probably took 10-15,000 miles so they can only have been catching ol knobbly under certain conditions - I guess under faster cornering (not a common occurence when my wife's driving ). Im pretty certain that with a more "enthusiastic" approach we would have seen the blow out sooner.

Anyway, new Vreds are on, knobbles are gone so I'll give it a thousand miles or so then whip off the wheels for a looksie. Hopefully all should be fine now.

[Digger]

THis one is even more demonstrative:

http://www.youtube.com/watch?v=W8UiE7yvO_M

Interesting.

Thankfully my tyres are running 45psi which is what they were when I bought the car so felt no reason to change the pressure. A tad high? Might drop to 40/42?

[PhilT]

Had a similar problem with my last set of Toyo T1R tyres, but have not had it before. I had put it down to tyre pressure, but wonder if it may also be related to the KW/other kit or height setting... Just did a Google, and as Doug says, it's a solid unit.



So based on Dave's description, is it because I love that hairpin corner to and from the in-laws and the inner circle is fouling the leg? Maybe with a little mixer of low pressures?

[Mancmatt]

I had put it down to tyre pressure, but wonder if it may also be related to the KW/other kit or height setting... Just did a Google, and as Doug says, it's a solid unit.

I too have wondered if the other suspension components have added to the problem . I have KW's fitted but this was done before I bought the car and I've never adjusted it myself.

Unless I'm mistaken however, the relative position of the wheel/tyre to knobbly is fixed and independent of the other suspension components/setup.

Maybe someone who knows a lot more than me could confirm this (or tell me I am mistaken of course!)