Cycling UK Forum

thatsnotmyname wrote:

Marcus Aurelius wrote:The little dimples are wear markers. The ripples look like a tyre failure, the carcass has disintegrated and / or there’s a delamination.

You must be looking at a different picture to everyone else...

I must know what I’m talking about is more like it ( as per usual ).

Debs wrote:Does anyone know what the strange rippling is on my rear tyre?

It's a Conti GP5000 Tubeless, done about 2k miles, the ripples only appear near or on the tyre crown of the rear.No sign of it on the front tyre.

These dimples go around the circumference of the whole tyre, more noticeable one side and less the other but still there...

looks to me like its worn out and just thin, the rubber not able to hold its shape any more due to thinness and the stresses on it due to road contact?

Marcus Aurelius wrote:

thatsnotmyname wrote:

Marcus Aurelius wrote:The little dimples are wear markers. The ripples look like a tyre failure, the carcass has disintegrated and / or there’s a delamination.

You must be looking at a different picture to everyone else...

I must know what I’m talking about is more like it ( as per usual ).

mercalia wrote:looks to me like its worn out and just thin, the rubber not able to hold its shape any more due to thinness and the stresses on it due to road contact?

Tyre is self-evidently not worn out, as the dimples (the two holes you can see in one of the pics) are still clearly visible. The tyres appear to have had very little wear at the time the pic was taken. Even the central moulding seam down the middle is still just about visible...

re the possibility of delamination. If the carcass is falling to bits then the tyre would have gone out of shape. If the tread is not bonded to the carcass then the anomalous areas are very small. IME such delaminations, when they occur, are over larger areas than this appears to be. If the tread is lifting then it is happening in a way that I have never seen previously.

cheers

Using a fingertip, see if you can move the tread rubber relative to the carcass.

I don’t trust / won’t use tyres made by that particular manufacturer, because of things similar to what we see there having happened to me on several occasions in the past. It’s much worse when the tyre lets go in a downhill corner as well.

https://forum.bikeradar.com/discussion/ ... going-bang

https://forums.roadbikereview.com/gener ... 54603.html

https://tandemclub.org/continental-tire-failures/

https://forum.slowtwitch.com/forum/Slow ... _P5938842/

https://bicycletouringpro.com/warning-a ... try-tires/

It appears they may have form. These are just a selection of tales of woe, these seem to be mostly side wall issues, but I’ve personally had failures on the main body of the tyre as well as side walls. I’ve not had the same issues with any other tyre I’ve used from any other manufacturer.

Marcus Aurelius wrote:https://forum.bikeradar.com/discussion/13063233/continental-tire-going-bang

https://forums.roadbikereview.com/gener ... 54603.html

https://tandemclub.org/continental-tire-failures/

https://forum.slowtwitch.com/forum/Slow ... _P5938842/

https://bicycletouringpro.com/warning-a ... try-tires/

It appears they may have form. These are just a selection of tales of woe, these seem to be mostly side wall issues, but I’ve personally had failures on the main body of the tyre as well as side walls. I’ve not had the same issues with any other tyre I’ve used from any other manufacturer.

The 'newest' of those threads you linked to is from 2016, so at least four years ago. And none of them relate to the tyre in question. Plus your strange obsession with Continental is well known across multiple forums.

When this thread was active back in May I had a well worn Continental Gatorskin 32mm on the back wheel of my most used bike. It had then done 6600 miles on a front wheel, followed by 6700 miles on a rear wheel. I had never had a tyre last so long before, but it clearly still had a few miles left in it. Its shape had become a little irregular in places but I could find no evidence that its structure was compromised anywhere so I decided to keep using it as long as feasible while keeping a close eye on it; this forum thread had piqued my interest.

There was a cross-hatched wear pattern in the tread centre a bit like the "ripples" in the photos of the original post. This suggested that the tread rubber layer was near to wearing through, but the wear indicating dimples were still a good fraction of a millimetre deep. The minor bulges in a few places on the shoulders were not showing wear marks like those which develop after a non-trivial cut has penetrated the carcase of a tyre, so I kept it going, inspecting carefully every 50 or so miles. The bulges never grew and the carcase never looked as if was going to fail. After a further 3100 miles I got three punctures in a day (the first for over a year) and decided that it was time to replace the tyre and start the forensics.





In the first photo the wear indicating dimples are clearly visible on the right. The cross-hatched wear pattern had now become more marked and visible round the whole circumference of the wheel. It clearly matched the thread pattern of the anti-cut mesh, the outermost layer underneath the tread. Deflation caused another pattern to emerge, the shallow ripples roughly 15mm apart along the tread, visible on the left. It was time to apply the knife.



I found that the tread centre had delaminated round the whole circumference, over a width of up to about 20mm. The two most prominent small shoulder bulges were due to a discontinuity (end-to-end join or overlap?) in the PolyX breaker - no cause for concern. I think both the cross-hatch pattern and the 15mm ripples are caused by the delamination. There are longitudinal shear forces where the tyre deforms during contact with the road. Once the tread rubber is detached from the underlying layer, being more elastic it moves relative to the anti-cut mesh during this deformation and the cross-hatch pattern results. The tread was not about to wear through, being still at least 0.5mm thick everywhere.

During manufacture the tread is vulcanized by applying heat to the tyre in a mould where the tyre components are forced together by air pressure. Thereafter the tread 'wants' to be the size it was in the mould whereas the carcase 'wants' to be the size it was before mould air pressure stretched it. (This is not quite true because the different components 'want' to shrink by different amounts during the cooling from moulding temperature.) So long as the tread remains securely attached to the carcass the two components must stretch and shrink together, but after delamination I find it entirely credible that the 15mm ripples, puckering if you like, are the result of the carcase wanting to shrink more than the tread at low pressure.

That's my theory, but I'm not a professional tyre technologist. I don't expect to get, or attempt to get, over 16000 miles out of a tyre again.

Chris, thank you for taking the time to post your experience, very interesting.

The tyres are still going strong, no problems or punctures, total milage around 3k now.

Only the rear tyre is affected, and it remains looking the same.
I tend to wash my bike down at least once a week, and after examine the tyres close up very carefully.
So far just a couple of tiny cuts, probably caused by those specially sharpened flints thrown on the roads from the council rock salt truck.

Although i do wonder if the GP5000TL maybe a bit too fair-weathery for this time of year...

Are you sure about your tyre pressures ?
Sounds a bit low to me but my bikes are all in the 25 or lower tyre width, had many good miles on Conti Tyres .
I can absolutely confirm the tyres aren't worn out. In fact they look almost new to me.

Chris Jeggo wrote:... I don't expect to get, or attempt to get, over 16000 miles out of a tyre again.

Tyres commonly delaminate between tread plies and breaker plies and/or carcass plies. Some tyres are notorious for it (eg spesh armadillos). A large driving force for this is the way the tyre flexes in service; and there are two components to this;

1) the different stiffnesses of the various layers and
2) the way bias ply carcasses deform, in shear.

The latter effect means that no isotropic layer in a tyre will ever be able to match the way the carcass deforms, not without seeing some unusual stresses. The best you can hope for is that the other layers in the tyre have a low modulus which mitigates the magnitude of such stresses. However low modulus is largely incompatible with 'puncture proofness' or even hard-wearing tread rubber. Obviously if the original tyre manufacturing process was flawed, these layers are never properly integrated in the first place. In any event all tyres have some pretty horrible stresses between layers and sometimes they fail as a result.

I have never seen a gatorskin fail as comprehensively as yours has; mostly I've seen delamination around bad cuts. But then I have never seen one do that many miles on the back, either.

FWIW one thing which will encourage premature failure within the tyre is contamination with solvents and/or chain lube; rubber compounds can absorb such materials, and they often both cause swelling in the rubber and can then cause the bond integrity to adjacent layers to be compromised.

cheers

Brucey wrote:Tyres commonly delaminate between tread plies and breaker plies and/or carcass plies. Some tyres are notorious for it (eg spesh armadillos). ....

My first experience of delamination was of an Armadillo, many years ago.

Brucey wrote:.... I have never seen a gatorskin fail as comprehensively as yours has; mostly I've seen delamination around bad cuts. But then I have never seen one do that many miles on the back, either.

If I am right in attributing the cross-hatch wear pattern to delamination, then the latter only started at a fairly high mileage. I wanted to keep the tyre going as long as possible just to see what would happen. When, at the end, I discovered the true extent of delamination, I was amazed that the tread was intact, apart from one cut that had started to enlarge by tearing at its ends.

Incidentally, at the edge of the delaminated area, on the tyre shoulders, the tread was still very securely attached to the structure.

9494arnold wrote:Are you sure about your tyre pressures ?
Sounds a bit low to me but my bikes are all in the 25 or lower tyre width, had many good miles on Conti Tyres .
I can absolutely confirm the tyres aren't worn out. In fact they look almost new to me.

65 is the recommended psi by Conti for their GP5000 700x32 tubeless. This is what i keep them up to and it seems to work very well.