did low pressures kill my conti tires

[JoO]

My conti tires (GP 4000 S2 in 25 mm and 28 mm) have developped a 'wobble' (up and down movement).
Could it be that I damaged the carcass of the tires by running too low pressures? ( 4,13 - 4,33 bars = 60 - 62 PSI)?

I do not want to start a low pressure discussion. People who are interested can read all about that here
https://janheine.wordpress.com/2015/01/ ... evolution/

[Calnago]

Have you tried taking them off and remounting? It may be that they were able to move a bit around the rim while you were braking, creating a high spot.
This happened to me recently when I inadvertently went out for a ride on some mounted, but unglued tubulars (my bad, thought I had glued them previously, but they were just mounted, waiting for a proper glue job). The braking forces would over the course of the ride push the tire up against the valve creating a high spot just before the valve, where it was somewhat prevented from sliding. Near the end of the ride I was noticing a discernible hop and felt very lucky that something much worse didn’t happen.
In your case, “maybe” the low pressures allowed the tire to more easily slide along the rim with the opposing braking force, and slid more in one spot than another, effectively resulting in the same issue I had. Can’t really imagine running 60psi in a 25mm Conti 4000sii myself, but like you say, there another thread.

[dim]

if both tyres have the same problem, then it could be due to the low pressures that you use?

[Calnago]

Why? Many people brake very differently between front and rear, and even though the vast majority of braking effect is best applied to the front, some people just tend to use the rear more. Also, in a group of people in a paceline I may brake very differently than if I’m coming to a hard stop by myself. The former I may be just feathering the rear to just slightly scrub a bit of speed very gradually (you would never brake hard suddenly in a paceline), versus a hard stop all alone where I’d be using the front with much more force.
Just don’t see your logic that BOTH tires would have to be slipping in order for it to be related to low pressure.

[Delorre]

60psi on a 28mm gp4000s is just perfect, unless you weight like 100kg. 60 psi on the 25mm variant is on the very low side, but my guess it that your issue has nothing to do with the low pressures. Does it happen on the same rim, or on different ones? Like other said, try remove the tyre and start all over. On some rims, the bead 'pops' in. If you ride low pressure, the tyre could be 'unpoped' also. So, when you put the tyres on again, start with 80 or 100psi, to make sure the bead is really well settled!

[TobinHatesYou]

Could it be possible that low pressure causes the sidewall to collapse once per tire revolution, which then results in casing threads breaking/fraying?

[CallumRD1]

Could it be possible that low pressure causes the sidewall to collapse once per tire revolution, which then results in casing threads breaking/fraying?

Yes, but absolutely not at 60 psi!

[JoO]

60 psi is low but I only weigh 62 kg + 7 kg bike.
I mounted the tire on 3 different rims. I havent tried to pump them too 100 PSI though. Will give it a try in the coming weeks.

[Calnago]

I just went out on a little spin with a bike that I have Conti GP4000 S2’s on (25mm). Only put 60psi in the rear (older Campy Neutron rim). There’s no way I would ride that wheel with 60psi on purpose. It’s ridable, but I’d certainly be looking out for even the slightest bump or pothole. 60psi same tire on a much wider rim could be ok I suppose, depending on rider weight and use. And 60psi, light rider, wide rim, and 28mm... well, getting into Beach Cruiser territory.

[TobinHatesYou]

60 psi is low but I only weigh 62 kg + 7 kg bike.
I mounted the tire on 3 different rims. I havent tried to pump them too 100 PSI though. Will give it a try in the coming weeks.

We weigh about the same and I agree it shouldn’t be an issue especially since 25mm GP4Ks are closer to 28mm. However anecdotally GP4Ks are also known for their weak sidewalls.

[alcatraz]

62kg running 28mm is a bit excessive considering gp4k's are wider than specified. Do you ride on terrible roads? Up the pressure a bit on a new set of tires and see if you get the same result.

I think I read somewhere that when the tire is weight loaded the right pressure is when the height compresses by 15%. Maybe you are well over 15%.

Do you use 60psi in the rear aswell as the front? If the rear is showing stronger symptoms you can be sure it has to do with the pressure because that's where more of your weight is.

[TheKaiser]

My conti tires (GP 4000 S2 in 25 mm and 28 mm) have developped a 'wobble' (up and down movement).
Could it be that I damaged the carcass of the tires by running too low pressures? ( 4,13 - 4,33 bars = 60 - 62 PSI)?

I've had at least 1 if not 2 tire casings fail from riding on rollers at lower pressure. This bike was a winter trainer that I'd been running at around 60psi for grip. The bike happened to have a 50/12 high gear and on a snowy day I decided to ride the rollers on it but they had no resistance unit on them. I found that the low pressure in the tires actually made the rollers far more usable than on prior occaisions when I had 100psi, so I just went with it even though the small contact area of the roller was really deforming the casing far more than normal. After about 30min, the casing couldn't take it and got a nasty wobble and hop in it, but didn't give way entirely and still contained the tube. Looking closely, you could see where the threads were torn. I can't quite recall, but I may have chalked that up to it being a particularly old and cheap tire, leading to a 2nd occurance.

If you look on MTBR, you will find a number of threads on Continental MTB tire casing failures. Most of them seem to follow the theme of "I was riding my normal pressures and terrain, but suddenly found my tire had a wobble in it" and most of these people said that had never occurred in their prior experience with other brands. I've always had good luck with them, but maybe Conti has a problem going on with their production or something. I think many of these people successfully got their MTB tires warrantied, so you could give that a try.

[Beaver]

I am running 25mm 4000S II on 21C rims with 4 bars front, 4,5 bars rear at around 80kg weight (rider and bike) on bad roads - so far no wobble.

[bm0p700f]

no one can say if the tyre failure was pressure related.

[nycebo]

I am running 25mm 4000S II on 21C rims with 4 bars front, 4,5 bars rear at around 80kg weight (rider and bike) on bad roads - so far no wobble.

Same-ish here. 65 lbs front, 80 lbs rear. Rides like a dream compared to when I use to overinflate to 100+ lbs. No problems whatsoever on any corners or bumps. In fact, I wonder if it is better to go over seams and what not with a slightly lower pressure.