I'm not sure if the bead humps are on the large side on the Caterham 13" wheels or the fact that they are smaller circumference than most car wheels, so there is less stretch in the bead than on say a 17" wheel, but mine always require a high pressure to seat. With Pirelli slicks my specialist tyre fitter had to go to 120PSI to seat (inside a steel cage they use for safety purposes), rating them as about the most difficult tyres to fit they had come across. Never had any issue with the 15" wheels I use for the road, though.
Had ZZS 13" fitted about a month ago.
I go to a little traditional fitting outfit & know the staff well. The manager was honest with me & said that the tyres were a bit of a pig getting the beads over the rim & seating. Especially the 215/55. He inflated to 20 psi only, bounced them around the workshop then put in 40 psi, again bounced them around.
Reduced pressure back to 20 psi for transit. I did not spot anything untoward when I collected & ever since the running has been OK.
#11 Not sure how that might work. Inflating to 60 static wouldn't guarantee no failure later.
#12 I tend to think it's a peculiarity of the rim humps combined with a slightly stiffer tyre, James. It's in the front face of both rims and for a similar length of bead. No real evidence, only a sample of 2, it's just my hunch.
If I'd had a cage and my mate had been willing I might have gone further but we felt it was safer to check with Avon first.
I've done lots of 13" tyres over the years, never failed to get one to seat until now!
#13 We didn't have any problems in getting the tyres onto the rims, Geoff, though needed a bead depressor to keep it in the well. The rears went on easily and seated easily to, at around 30psi.
We did all the bouncing and pressure changing too, even broke the rear beads again, moved the tyres around a bit and refitted but no joy with the fronts. If I'd thought of it at the time I'd have taken the tyres off and fitted them the other way around; that might have been informative.
Which rims are you running Peter, 8 spoke or Apollo's..?
It's odd this hasn't raised it's head before unless Avon have recently altered the construction or there's a manufacturing change to the rim profile..?
Neil, to both your comments:
They were Apollos, a brand new set from DT I believe. Not my rims. I have two sets of Apollos from 2015 which have had ZZRs most of their life and never been a problem.
The tyres were marked RT7 which I believe is Race and Trackday. (For 7s?) Not sure if that's relevant or not.
Wondered if this was about those wooden bead seat covers loved by taxi drivers a few decades ago
#20. No they fit well in the composite seats. A bit of trimming but I wouldn't be without them now!
Them and the string gloves!