When to replace tyres
08-21-2014, 01:22 AM
#31
Going off current forum trends, like considering buying a new headlight when your bulbs snuffs it.... 
I guess that if the pressure drops by 1 psi you should immediately throw the tyre away?
I guess that if the pressure drops by 1 psi you should immediately throw the tyre away?
08-21-2014, 02:13 AM
#32
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OK. Some actual experience.
Having driven on both damp and dry tracks with fairly well-worn tyres (2-3mm left) and new-ish tyres, I can report that grip levels and cornering speeds were much better with the new-ish tyres, the effect being more pronounced in the damp of course.
Given bikky's track day is at Croft, which is oop norf, it's more than likely to be damp/wet, so newer tyres make a lot of sense.
Having driven on both damp and dry tracks with fairly well-worn tyres (2-3mm left) and new-ish tyres, I can report that grip levels and cornering speeds were much better with the new-ish tyres, the effect being more pronounced in the damp of course.
Given bikky's track day is at Croft, which is oop norf, it's more than likely to be damp/wet, so newer tyres make a lot of sense.
08-21-2014, 03:31 AM
#33
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not quite, because the tyre's WILL be replaced in the next month anyway, so it's more like saying, the headlight bulb flickered so will be going pop in the next week or two, so i'll spend money now on a replacement rather than in a week or two.
08-21-2014, 07:36 AM
#34
and for info bald tyres are not the same as slicks, ask plod.
08-28-2014, 11:14 AM
#35
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I agree with Si2k.
BUT
There is also the issue of heat cycling. By running the tyre hard on track or road, then allowing it to cool, you cause a change in the composition of the rubber. Each cycle has a minute effect, but over the lifetime of a tyre, the number of cycles adds up and the rubber becomes harder and less likely to grip.
Depth of tread has nothing to do with grip on a dry, smooth track. The mechanism by which the rubber grip the road is adhesion. Nothing else.
This is a function of the coefficient of friction between the rubber and the tarmac, the force acting to push the surfaces together and that's it.
When the tyres get old, the rubber gets less sticky and more shiny (think old chewing gum, just before you get rid of it) and the coefficient of friction is lower.
Now, as to whether you use old tyres or new tyres on the track... Your money, your car, your choice. Depends on how hard you plan on pushing the envelope.
BUT
There is also the issue of heat cycling. By running the tyre hard on track or road, then allowing it to cool, you cause a change in the composition of the rubber. Each cycle has a minute effect, but over the lifetime of a tyre, the number of cycles adds up and the rubber becomes harder and less likely to grip.
Depth of tread has nothing to do with grip on a dry, smooth track. The mechanism by which the rubber grip the road is adhesion. Nothing else.
This is a function of the coefficient of friction between the rubber and the tarmac, the force acting to push the surfaces together and that's it.
When the tyres get old, the rubber gets less sticky and more shiny (think old chewing gum, just before you get rid of it) and the coefficient of friction is lower.
Now, as to whether you use old tyres or new tyres on the track... Your money, your car, your choice. Depends on how hard you plan on pushing the envelope.
08-28-2014, 12:27 PM
#36
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Well thanks all for your input, however the last week or so has seen me "practicing" 
for "sketchy" 
cornering and recovery when the back end wants to go somewhere different to the front. So new tyres it is, and probably next week or 2.
for "sketchy" cornering and recovery when the back end wants to go somewhere different to the front. So new tyres it is, and probably next week or 2.
08-28-2014, 12:39 PM
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09-11-2014, 12:49 AM
#38
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Well for those of you still following, I've had them changed, and feel as though I have made a mistake.
There's now a fair bit of slippage starting to happen at the back on corners and roundabouts, where-as with near legal limit was no budging at all.
And yes, they're the same tyres, Goodyear Eagle F1 Assy2's. In fact even when warm, after a 30 minute drive I could feel slippage on a small roundabout, where 3 days ago on the old, on cold tyres (3 mins driving) there was non.
I suppose now it's a case of 29, 30, 31 or 32 PSI...
There's now a fair bit of slippage starting to happen at the back on corners and roundabouts, where-as with near legal limit was no budging at all.
And yes, they're the same tyres, Goodyear Eagle F1 Assy2's. In fact even when warm, after a 30 minute drive I could feel slippage on a small roundabout, where 3 days ago on the old, on cold tyres (3 mins driving) there was non.
I suppose now it's a case of 29, 30, 31 or 32 PSI...
09-11-2014, 12:57 AM
#40
I think read on here there are two different speed ratings/compounds in circulation you might check the right ones have been fitted, I'm sure someone who had experience of the Goodyear's will point you as what you should have. I can't help on this as I use Bridgestones.