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At Castle Combe yesterday, I noticed a distinct drop -off in traction towards the end of the day. When I came into the pits and looked at my tyres I could see why - all four were blistered.

We were doing 15 minute sessions with 15 minute pauses between, with only half a dozen cars on track at a time. The track was dry and the air temp about 20 degrees.

Has anybody on here got any ideas why they may have blistered like this?

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How many track days have you done on them and what pressures were you running? Looks like a tyre pressure problem. Saying that the Yokohamas tend not to be able to take too many heat cyles before the performance drops off and they become dustbin fodder.

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Is that blistering (ie a sub-surface problem)? That to me looks like a combination of surface melting and picking up baubles of used rubber from a dirty track. Mine always look like that - means you've been trying hard :D . Some of them will 'zing' off when you're driving around town.

Re. pressures. I have been using the 'hot' pressures as per the manual on track for 40min long, dry sessions. I then checked the temps at 3 places across the surface with a pyrometer and got a drop off of readings as you would expect for a tyre at the correct pressures, so, not that I would ever second guess the Lotus big brains, but I think the pressures given in the manual are good :lol:

g

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How many track days have you done on them and what pressures were you running? Looks like a tyre pressure problem. Saying that the Yokohamas tend not to be able to take too many heat cyles before the performance drops off and they become dustbin fodder.

This was their fourth track day (plus a couple of airfield activity days). As to tyre pressues, I have followed the manual and used 24 front and 26 rear (cold) - I haven't seen any hot pressures quoted. [EDIT - I have now found the bit where it says 28 front and rear hot]

I guess they have been through a few too many heat cycles. I was planning to replace them after yesterday anyway but was worried in case this was an inicator of something unusual.

Gavinp

I will try to get a better picture when I take the wheels off but I think it is a sub-surface problem. I may have picked up a few bits as the last session was red-flagged and I did all of 300 yards before pulling into the pit lane (not much of a cool-down lap).

Edited by DEL211
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This was their fourth track day (plus a couple of airfield activity days). As to tyre pressues, I have followed the manual and used 24 front and 26 rear (cold) - I haven't seen any hot pressures quoted. [EDIT - I have now found the bit where it says 28 front and rear hot]

I guess they have been through a few too many heat cycles. I was planning to replace them after yesterday anyway but was worried in case this was an inicator of something unusual.

Gavinp

I will try to get a better picture when I take the wheels off but I think it is a sub-surface problem. I may have picked up a few bits as the last session was red-flagged and I did all of 300 yards before pulling into the pit lane (not much of a cool-down lap).

Del,

If they have been through a number of heat cycles the rubber gets really hard and won't have anywhere near the originlal level of grip so they are worth replacing and maybe keeping the ones you have as a spare road pair.

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When you say you are using the 24 front and 26 pressures, cold, are you taking about 5psi out after your first session? If not, I bet they are about 33-35psi, which will be very oversteery and overheat the tyres. I take pressure out after at least the first 3 sessions of the day. Don't forget to pump them up for the drive home!

g

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When you say you are using the 24 front and 26 pressures, cold, are you taking about 5psi out after your first session? If not, I bet they are about 33-35psi, which will be very oversteery and overheat the tyres. I take pressure out after at least the first 3 sessions of the day. Don't forget to pump them up for the drive home!

g

AH erm no, haven't been taking out any pressure when they get hot - mainly because I hadn't previously spotted the 28psi when hot recommendation. So that would explain all the oversteer - I thought it was my lack of talent and heavy right foot :D

Thanks guys - I will treat the new set a lot better (although I was surprised to get so many track days from this set - thought it was something to do with my wimpish driving)

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AH erm no, haven't been taking out any pressure when they get hot - mainly because I hadn't previously spotted the 28psi when hot recommendation. So that would explain all the oversteer - I thought it was my lack of talent and heavy right foot :D

You are going to be seriously amazed at what a difference the correct pressures will make.

g

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  • 3 weeks later...

I tossed the Yokahamas away and replaced them with Dunlop Formula "R"s. 205/16 fronts and 245 /17 rears.

There was a noticable improvement in handling, partially I think due to the wider footprint, but I found the Dunlops came up to operating temperature quicker. This is ideal for hillclimbs where the tyres need to be working at the first corner (as opposed to a warm-up lap on the track).

Yokohamas cold are lethal.

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You are going to be seriously amazed at what a difference the correct pressures will make.

I adjusted the pressures to 28 psi after my first session on Friday and did notice an improvement - although not sure how much of this was due to having new rubber on the back.

Interestingly, an Exige at the same event had been running his A048s at about 38 psi (hot) - following discussion around the paddock that this seemed quite high, he lowered them to 32psi and promptly spun off !

D

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I can be a bit geeky with my tyres, using a laser thermometer to check the temp across the surface. Does seem to show that 28 is the right pressure. 38 would show the centre of the tyre a lot hotter than the edges, as the pressure makes the tyre balloon (less road contact at the eges, more at the centre line).

g

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I adjusted the pressures to 28 psi after my first session on Friday and did notice an improvement - although not sure how much of this was due to having new rubber on the back.

Interestingly, an Exige at the same event had been running his A048s at about 38 psi (hot) - following discussion around the paddock that this seemed quite high, he lowered them to 32psi and promptly spun off !

D

On speaking to the boffins at Lotus Sport 28 psi is the best pressure to run hot when on the track.

P

Edited by pgn340r
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The technicians at Ascari dropped mine to 1.35 front and 1.55 rear - it was +33 degrees so a hot old day. No complaints at all on the handling front with those pressures.

What's that in old money as was that cold or hot?

P

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The technicians at Ascari dropped mine to 1.35 front and 1.55 rear - it was +33 degrees so a hot old day. No complaints at all on the handling front with those pressures.

Bar is based upon atmospheric pressure at sea level (also known as Atmospheres) so 1 Bar is about 14.5 psi.

This means that they set your fronts to about 19.5psi and rears to 22.5psi. Seems soft compared to the Lotus recommendations - but if it works for you, then stick with it.

The nice man at Simply tyres inflated mine with nitrogen yesterday - apparently this significantly reduces the pressure difference between hot and cold. As mine didn't have much of a chance to get cold yesterday after he had done it, I haven't had a chance to see what effect this has.

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Bar is based upon atmospheric pressure at sea level (also known as Atmospheres) so 1 Bar is about 14.5 psi.

This means that they set your fronts to about 19.5psi and rears to 22.5psi. Seems soft compared to the Lotus recommendations - but if it works for you, then stick with it.

The nice man at Simply tyres inflated mine with nitrogen yesterday - apparently this significantly reduces the pressure difference between hot and cold. As mine didn't have much of a chance to get cold yesterday after he had done it, I haven't had a chance to see what effect this has.

Those pressures seem really low, but of course as they get hotter the pressure will go up (maybe 5psi) and if it works for you then cool.

I am not sure about Nitrogen. (Assuming there is some change in pressure with heat build up). What happens when you are at track and want to play around with pressures? You can't put Nitrogen back in at that point.

g

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