Stupid question time...

[Jdubya]

Do tyres go "off"?

Just wondering as the bridgestones on the 'tona were really good in wet and dry up until about 500 miles ago. Now they just dont feel right. The front started going twitchy before we did the '.org does france' day (Baldyman can testify as to one of the moments I had) and the rear started feeling twitchy just the other day. Is it all just in my head? The tyres prolly have another 2000 miles left in them but my confidence in the tyres is just not there any longer.:( :smt089

[fizzwheel]

I found this with the Bridgestone also. They were reasonably OK for the first 2 / 3rds of their life, and then both the 020's and 014's I've had have gone down hill rapidly very quickly at the end of their life.

I've never had another brand of tyre do it.

the 014's went down hill rapidly on the GSXR, they went from OK ish, to no grip what so ever in the space of maybe 500 miles.

really knocked my confidence.

[Jdubya]

Ta for that... I thought it was just my imagination:)

[stuartyboy]

I don't think they go "off" as such - like bread goes mouldy but I guess the rubber molecules would change over time due to oxidation or the effects of heat cycles? I know feck all about chemistry though. Maybe someone else can explain that

Structurally -they do go "off". A very crude analogy...

Imagine you are painting a roughcast wall. You have a new long haired brush and an old brush with worn bristles. The long haired brush will flex more and get in the nooks and crannies. The short haired brush will have less flex and struggle to get into all the gaps.

Your tyres are a bit like this when new. After a few thousand miles there's a wee bit less flex in the rubber.

There's also heat retention and dissipation to think of. As the tyre wears heat will dissipate from the rubber - like at traffic lights.

I have a DVD about it somewhere. There was some aussie moto gp rider who figured out that if he spun up his tyres as much as possible during a race then there would be less chance of the tyres going off before the end. This lighting up made the surface very hot but kept the temperature nearer the carcase much cooler - prolonging the tyre.

[Biker Biggles]

Not sure about the chemistry,but it sounds plausible that grip gets worse with age,but what definitely happens is the shape changes with wear.We are all familiar with that sqared off rear tyre that is needing replacement,but the front will wear unevenly after a few thousand miles too,and this has a big effect on grip when tipping it in.

[DanAbnormal]

and this has a big effect on grip when tipping it in.

This may explain why I tipped my bike 'in'.........to a ditch. Twice. Damn Bridgestones! When fairly new my BT020's are great in teh wet, when worn a bit they aren't good at all, the back spins up a lot. Of course this could be attributed to the fact that I still ride as if it were dry........................:rolleyes:

[Alpinestarhero]

I dont think the heat etc as such would affect the chemistry too much; the tyre manufactures are aware of this sort of thing, so I guess that the (synthetic) rubber used is good against oxidative processes. After a good few year's they'll go bad, sorta...crumbly like I imagine. But i'm not a polymers expert and can only guess a bit, as much as you guys. There may be a physical process, such as tyre additives and lower molecular weight rubber molecules being brought to the outside (actualy, this would be due to heat, and also the rotating gyroscopic forces) which I gues could make the rubber near the carcass of the tyre a harder compound. But I'm guessing, and being over analytical and probably wrong.

My dad complained about his bridgestones, he also found that suddenly (over a few hundred miles) they just went "off". I'm not sure about other tyres, but bridgestones seem to be a bit notorious for this behaviour...

Matt

[stuartyboy]

But I'm guessing, and being over analytical and probably wrongMe too but you made it sound better than i did.

[Jdubya]

The tyres just seem to be "white-lining" a bit more than I think is necessary if you get my drift(no pun intended;) )