The Prism-er Posted June 2, 2008 Share Posted June 2, 2008 Running 195x45x15 CR500's on anthracites. 6 weeks ago pre MOT check revealed cracking of inside wall on rear tyre. Tyre replaced and fitted at Caterham Midlands who commented it was unusual to have problems perhaps it had been run at low pressure. Tyres always run at 16 with no loss of pressure. MOT passed and tyre pressures adjusted to 18 rear and 17 front for fully laden 2700 mile trip around Spain and France. On return, I have noticed both front tyres starting to show the same problem. Always inside wall and still plenty of tread left in the tyre. Anyone else experienced similar problem and if so what are the recommended alternatives? No track days, touring only. The Avons appear to be an expensive luxury! Thanks in advance. S7VRN - Chameleon 1.8 K Supersport. Link to comment Share on other sites More sharing options...
Ian B Posted June 2, 2008 Share Posted June 2, 2008 Anyone else experienced similar problemEr yes here They collected all 4 of mine, and then sent replacements without question , but haven't responded to my subsequent questions as to the cause Could be a faulty batch/compound but it is temperature (and therefore perhaps pressure) related as the inside wall runs quite a bit hotter than the outside as it 'flexes' more due to the camber. Ian - MI 5EVN - Slightly Vider SVelte model 😬 now repainted to match the Autocom headsets (and AA recovery truck 😳) Edited by - Ian B on 2 Jun 2008 21:16:44 Link to comment Share on other sites More sharing options...
Simon Owen Posted June 2, 2008 Share Posted June 2, 2008 Martin, Sorry to hear about the tyres, always run at the correct pressure when on my car and never seemed to leak air much. The only thing I can think of is perhaps age, if they were the original ones then they could be approaching 5yrs old ? How is the spare ? Do people run the 55 profile R888’s on the 15” rims, could be a good ‘sticky’ combination though I suspect not as good in the wet ? Hope you had a good trip 🤔 Cheers, Simon Link to comment Share on other sites More sharing options...
Simon Owen Posted June 2, 2008 Share Posted June 2, 2008 Blimey ...... just off to check my tyre pressures Link to comment Share on other sites More sharing options...
stevefoster Posted June 2, 2008 Share Posted June 2, 2008 I've not had the inner side wall problem but don't run much camber. I do have a line of small cracks in the tread about 1" from the centre - same side on both fronts. They repeat every 1" or so apart. Must read that original thread again... My rear tyres are fine. Add lightness, says the man with a VX :-) My 2002/2003 racing pics here General pics (mostly of 7's and cars). here Link to comment Share on other sites More sharing options...
Ian B Posted June 2, 2008 Share Posted June 2, 2008 Pics of cracks in mine here Ian - MI 5EVN - Slightly Vider SVelte model 😬 now repainted to match the Autocom headsets (and AA recovery truck 😳) Link to comment Share on other sites More sharing options...
rgrigsby Posted June 3, 2008 Share Posted June 3, 2008 I've not had the cracks but did have two blow outs on a 13" 205 rear and I know of at least one other person who had a 13" 175 tyre blow out. Having said that Avon where extremely helpful and replaced the tyre without question and I'm going to continue to run them as they are the best all round tyre IMHO. Cheers Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
stevefoster Posted June 3, 2008 Share Posted June 3, 2008 Here's a pic of one of my fronts - both have this thin crack / split - all the way around. here Should I be on to Avon? Add lightness, says the man with a VX :-) My 2002/2003 racing pics here General pics (mostly of 7's and cars). here Edited by - stevefoster on 3 Jun 2008 21:53:53 Link to comment Share on other sites More sharing options...
The Prism-er Posted June 4, 2008 Author Share Posted June 4, 2008 Steve, Damage in evidence on my tyres is on the side wall not on the tread. Out of interest, what is the batch number on the side of the tyre? This I assume to be the 5 digit number. Martin Link to comment Share on other sites More sharing options...
Mike Biddle Posted June 4, 2008 Share Posted June 4, 2008 What's the "correct pressure" I always run mine at somewhere between 12 and 15 PSI. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 4, 2008 Share Posted June 4, 2008 18psi for me on 15" wheels 7 related photos Link to comment Share on other sites More sharing options...
Bumble SV Posted June 4, 2008 Share Posted June 4, 2008 I run 18psi on CR500s 195/45/R15. After hearing a few horror stories, I check the pressures once a week on both the 7 and tin top - the variations (especially in Spring when the weather swaps from cold to hot frequently) always amaze me. Off to check the inner sidewalls too... Roadsport SV - Yellow/Black Stripe Link to comment Share on other sites More sharing options...
rgrigsby Posted June 4, 2008 Share Posted June 4, 2008 Hmm 12 and 15 seems a bit low, I tend to run 17 front 19 rear on 175/205's. Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
Mike Biddle Posted June 4, 2008 Share Posted June 4, 2008 I find I get more grip with those pressures, I used to run the ?????? (Avon crossplys that I can't remember the name of) at that pressure too with good results. Sevens are very light! Link to comment Share on other sites More sharing options...
TomB Posted June 4, 2008 Share Posted June 4, 2008 Im on 20 PSI cold with my 6 inch CR500. Link to comment Share on other sites More sharing options...
stevefoster Posted June 4, 2008 Share Posted June 4, 2008 I run 17-18psi cold for blatting and 20-22 at motorway speeds. I would not run 12-15 at motorway speeds seems way toooo low. I did run 13psi NSF slick on track and that heated up to 20psi hot on a hot day but that is another matter all together. Add lightness, says the man with a VX :-) My 2002/2003 racing pics here General pics (mostly of 7's and cars). here Link to comment Share on other sites More sharing options...
Ian B Posted June 4, 2008 Share Posted June 4, 2008 18 PSI cold Ian - MI 5EVN - Slightly Vider SVelte model 😬 now repainted to match the Autocom headsets (and AA recovery truck 😳) Link to comment Share on other sites More sharing options...
The Prism-er Posted June 12, 2008 Author Share Posted June 12, 2008 Update - After contacting Avon (Cooper tyres), they arranged collection by courier next day and after inspection are now sending 2 replacements. Excellent customer service. No explanation as to possible reason for the fault. S7VRN - Chameleon 1.8 K Supersport. Link to comment Share on other sites More sharing options...
johnpbransfield Posted June 12, 2008 Share Posted June 12, 2008 Good result Martin, you don't think the car was carrying too much weight then after all those meals and drinks in Spain and France? Link to comment Share on other sites More sharing options...
The Prism-er Posted June 12, 2008 Author Share Posted June 12, 2008 😬 😬 It has been suggested that damage was caused from petrol perishing the rubber, as a result of fuel spilt on garage forecourt when Yellow 7 was trying to fill fuel tank. S7VRN - Chameleon 1.8 K Supersport. Link to comment Share on other sites More sharing options...
Mike Biddle Posted June 12, 2008 Share Posted June 12, 2008 Steve, why is 15 PSI "way toooo low"? Not looking for an argument here, just interested to know if there is any hard evidence. I have run my seven for 10 years with these tyre presures including long high speed runs at up up to 120 MPH and (Breifly) at speeds up to 150 MPH with no problems at all. Link to comment Share on other sites More sharing options...
rgrigsby Posted June 12, 2008 Share Posted June 12, 2008 Mike I've been running CR500's for 5 or 6 years now with 17 front and 19rear pressures, I would have thought with 15psi the sidewall would flex a lot ultimatly leading to it overheating and failing. Clearly your experience suggests this doesn't happen but I can only think you are right at the lower end of the range of suitable pressures, it would be interesting to get Avon's opinion on this based on a 500KG car. I've had two un-explained sidewall failures and there is a train of thought that they might have been caused by low pressures and overheating although I'm not convinced by this. Do you get even wear across the tyre? just wondering as I get pretty even wear with the pressures I run and our cars are very similar in weight. Cheers Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
Mike Biddle Posted June 12, 2008 Share Posted June 12, 2008 I've not experienced uneven tyre wear Rob, even after some track day sessions at Castle Combe, in fact the fronts looked to be evenly affected all the way across the tread. Iguess the best way to find out is to take tyre temps after a hard run or track session. Would be interested to learn how you get on with the Khumo's. Your Car is looking great by the way. Edited by - Mike Biddle on 12 Jun 2008 23:18:49 Link to comment Share on other sites More sharing options...
6speedmanual Posted June 12, 2008 Share Posted June 12, 2008 Surely it is the pressure of the tyre at its operating temperature which is important. The cold pressure is only what they are set to when the car is standing in an undriven condition in the garage. After it has been driven, the tyre warms and pressure can rise by quite a few psi. On trackdays, I have started with cold tyres at 18psi, find them rise to over 22psi on first session. I then let them down to 22psi (fully warmed up) and so long as going on track sessions every 30 minutes or so,they stay near there for the rest of the day. In cold or wet conditions when heat build up is difficult to achieve, a cold pressure nearer to the required running pressure may be desirable. For sprinting, a lower pressure can induce more flex to help the tyre heat quicker. All a bit of a black art really.... and each to their own applied ideas of what they want the pressures to be. The only place for gaining really deep knowledge of what hot and cold tyre pressures to use is in competitive motorsport or test work where measured results are recorded under repeatable conditions. The CC recommended pressures are probably based on finding a good average (cold fill) point which suits most people in most conditions most of the time. 6SpeedManual *tongue*There's no such thing as too much BHP per Ton 😬 Link to comment Share on other sites More sharing options...
scooter Posted June 27, 2008 Share Posted June 27, 2008 I've had that on a CR500 that was never even run... just sat in the garage for 6 months (wrapped). Avon wouldn't have any of it! Link to comment Share on other sites More sharing options...
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