Tandem tyre failures: final analysis and next steps

[roubaixtuesday]

Those paying attention may recall tyre woes on our epic 8,500km tour, now successfully completed.

As background, a new to us tandem was acquired just three days in after a frame failure; we never had issues over 25 years with the old machine.

https://www.cyclechat.net/threads/tyre-blowout-advice.297265/#post-7191440

The new machine has "tubeless ready" rims, which may or may not be relevant. Disc brakes are fitted. Total weight is ~200kg.

There were further issues after that thread; attached is a full list of all 12 tyres which were used, of which 5 failed, 3 with catastrophic blowouts, together with their origin and fate.

All tyres were run at ~10% overpressure, checked religiously with an accurate separate gauge, not the pump gauge. This was the consensus of advice on pressure from both tandem shop and various contributors here and elsewhere, though I absolutely respect alternative views on that too, of which there were a few.

 

[roubaixtuesday]

My assessment:

1. Neither tyre size nor pressure made any difference to longevity; 28s and 32s lasted the same distances, and M+ (95psi) vs Randonneur (75) again made no difference.

2. GP5000s seem to be good for the setup, with no failures over significant distances.

3. I have no explanation for the gatorskin failure, which as I understand it have very similar construction to the GP5000

3. My best guess is that the issue is caused by tight radius and/or sharp edges on the tubeless ready rims. I guess that the GP5000 has either more flexibility or a higher resistant protective band at the bead than the others.

Overall I'm not confident I understand the causes at all well, and we need to change the setup.

 

[roubaixtuesday]

Next steps:

Either

1. Get different rims fitted or

2. Buy a new tandem which can take wider tyres.

The second option isn't as easy as it sounds, as regardless of expense, getting a tandem which fits a 6'4" pilot and 5'3" stoker is difficult if not near impossible.

I'll be seeing professional advice from probably more than one shop before deciding the way forward, but would appreciate all thoughts from those on here first!

 

[PedallingNowhereSlowly]

What are the rims?

 

[roubaixtuesday]

What are the rims?

Ambrosio P20 36H

 

[PedallingNowhereSlowly]

I was looking for a data sheet. I didn't find one.

But I did find several reports on many cycle flora of it being a struggle to mount tyres on them. Looks like the later version of the rim was revised so tyres were easier to fit.

I wonder what the cause of that is, an issue with the rim flanges? If the flanges are on the deeper side, could they be a contributory factor?

Totally speculating. I'm not sure it is necessarily helpful.

 

[Ajax Bay]

Rims:

 

[roubaixtuesday]

I was looking for a data sheet. I didn't find one.

But I did find several reports on many cycle flora of it being a struggle to mount tyres on them. Looks like the later version of the rim was revised so tyres were easier to fit.

I wonder what the cause of that is, an issue with the rim flanges? If the flanges are on the deeper side, could they be a contributory factor?

Totally speculating. I'm not sure it is necessarily helpful.

That's my theory too, though I'm not altogether convinced.

We found it very difficult to seat tyres too to start with, which is why we abandoned the original M+ tyres as we just couldn't seat them at all. A lubrication regime of shower gel on tyres and rims and the purchase of a mini track pump solved that, but they make a hell of a ping when they do seat.

This is my first experience of "tubeless ready" rims, so I'm not sure how normal this is.

 

[rogerzilla]

I have found that some modern tyres (Schwalbe Durano is one) blow off normal hook bead rims at a mere 10% overpressure. When this is 105psi, that leaves very little margin for error.

 

[roubaixtuesday]

I have found that some modern tyres (Schwalbe Durano is one) blow off normal hook bead rims at a mere 10% overpressure. When this is 105psi, that leaves very little margin for error.

This wasn't an issue with blowing off - the tyres were still (very) firmly attached to the rim. There was just a bloody great hole between bead and sidewall.

 

[rogerzilla]

That used to happen during the 90s MTB boom when people put wide tyres on narrow rims. But I agree it's a rim problem - I'm not impressed with many modern rims, with their weird dual-use profiles and their unusably low maximum spoke tensions. I would just rebuild onto standard cheap hook bead rims, especially if you can find an ERD match to save on new spokes. It's too dangerous a fault to mess about saving the cost of two rims.

Edit: the economics of this change if you don't build your own wheels, as most wheelbuilders, if you can find a good one, insist on new spokes.

 

[roubaixtuesday]

That used to happen during the 90s MTB boom when people put wide tyres on narrow rims. But I agree it's a rim problem - I'm not impressed with many modern rims, with their weird dual-use profiles and their unusably low maximum spoke tensions. I would just rebuild onto standard cheap hook bead rims, especially if you can find an ERD match to save on new spokes. It's too dangerous a fault to mess about saving the cost of two rims.

Yeah, it's not a cost issue, more trying to make sure we have the right solution.

 

[Jameshow]

Ambrosio P20 36H

I have a pair if these that spa were selling off cheap so I brought a pair 16/20h.
Nice rims but a real pig to get tyres off and in tbh.
I only use them for local rides for that reason.
Have you through about a bigger tyre diameter so it does less flexing. Perhaps 35/40mm?

 

[roubaixtuesday]

I have a pair if these that spa were selling off cheap so I brought a pair 16/20h.
Nice rims but a real pig to get tyres off and in tbh.
I only use them for local rides for that reason.
Have you through about a bigger tyre diameter so it does less flexing. Perhaps 35/40mm?

We don't have clearance for >32 (tried a 35)

 

[Ajax Bay]

Those rims are 20mm internal so 28/30/32mm tyres (as inflated) should be fine.
The issue is that you are forced (pinch flats) because of the complete load (200kg) and the max width tyre the frame's clearance allows, to inflate these tyres above their spec.
Edit: I can't see that the OP's Option 1 (new rims) solves this.
A solution is to embrace tubeless tyres (these rims are TR right) and thus run them at 'in spec' pressures.