ZZS Bead seating.

[ScottR400D]

I've just been fitting and balancing a new set of ZZS to a new set of rims for a club member mate. 

All straight forward except we couldn't get the beads to fully seat on the front rims. 

He's off to ask Avon what the maximum pressure allowable for seating but just wondered if anyone has had the same issue?

Max pressure marked on the tyre is 44psi so we were loathe to go higher without Avon input  

 

 

[Beagler]

Ive seen tyre fitters use ratchet straps to wrap round the middle perimeter  to get them to seal. I expect youve tried this.

[ScottR400D]

Yes we tried that but no joy. Broke the bead several times, rotated the tyre, held down the opposite side but always the same part wouldn't seat. Loads of lube. Both front rims the same, rears no problem. 

Fitted lots of ZZRs and never had this issue though the S does seem a heavier tyre. 

[Benton]

Over a year ago had a set of ZZSs fitted by Caterham.  
Found out a couple of days later one of the rears had slightly dropped pressure and through using some soapy water I found it hadn't obviously seated/sealed properly in a couple of areas.

Caterham tried refitting but the problem persisted and so they ended up having to replace it with a new tyre. I assume the original tyre had some kind of manufacturing defect, must happen sometimes.

[ScottR400D]

Interesting. I think this maybe different. The tyres were 15mm off seating just hanging up on the edge of the seat. Front of the rims in both cases. 
 

 

[Dixa1225]

Not uncommon to need to put high PSI to get these to seat. Last set I fitted needed 80psi. 

[Dixa1225]

Not uncommon to need to put high PSI to get these to seat. Last set I fitted needed 80psi. 

[ScottR400D]

#7 that's what I was looking for! Presumably the tyres didn't explode, as you're still here!

As said I was loathe to go so high with someone else's tyres and rims and my body in the firing line!

I'll post what Avon say.   

 

[Dixa1225]

Yep, no issues. The side walls are so stiff on these. We leave them in our paint oven for a couple days before trying to fit.

[ScottR400D]

My impression was that they're a lot stiffer than the ZZR, though I thought they were the same construction. 

[rj]

I've been taught to test all new tyres at 4bar (60PSI-ish) to ensure they don't blow in use.

Never had issues with ZZSs though.

[aerobod - near CYYC]

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.

[Geoff Brown]

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.

[ScottR400D]

#11 Not sure how that might work. Inflating to 60 static wouldn't guarantee no failure later. 
 

 

[ScottR400D]

#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!

[ScottR400D]

#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. 
 

[7 wonders of the world]

Which rims are you running Peter, 8 spoke or Apollo's..?

 

[7 wonders of the world]

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..?

[ScottR400D]

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. 
 

 

[SM25T]

Wondered if this was about those wooden bead seat covers loved by taxi drivers a few decades ago 

[ScottR400D]

#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! 

[ScottR400D]

Avon have confirmed it's OK to go up to 6 bar to seat the beads. The tyres in question seated at 4 bar after resting under pressure for a few days. 

[Geoff Brown]

59psi as against 88psi seems a more reasonable resolution. As previously my anthracite eight spoke seated at 40psi (3 bar)

[ScottR400D]

Of course, Geoff, the lower the better! But it's possibly reassuring that Avon are happy for them to be inflated up 6 bar if necessary. 

When we were fitting the tyres on Wednesday we had got up to 55psi but I was reluctant to go higher with the max pressure rating indicating 44psi and them not being my tyres. Though I'm quite attached to my garage roof so that was a consideration too!!

My mate brought the two wheels back yesterday and I balanced them for him.

I also balanced his original set of Apollos and ZZRs. which was interesting. Brand new 420, 700 miles. None of the wheels were balanced properly.

One had no weights on at all, didn't appear to ever had any  on and was quite out of balance.

Another had 3 separate weights on the centre line which suggested to me that it had been statically balanced and they'd first stuck on a largish (50g) weight and then added small weights either side, possibly because they kept getting add 5g messages which may have been indicating that the original weight was just in the wrong place. 

The other rims had some weights on and tape marks showing some had already fallen off. All the remaining weights came off very easily.   

[aerobod - near CYYC]

One thing to consider when using high pressures to seat tyre beads is that a safety cage enclosing the tyres should be used, in case a latent defect causes the tyre to explode: