Pinch flats vs tubeless

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  • Pinch flats vs tubeless
  • DT78
    Member

    So, fixing my third pinch puncture in as many rides I was contemplating the move to tubeless. Reasons I haven’t done before is I was a serial tyre changer depending on conditions and just didn’t want all the faff.

    Now I’ve switched to 29er I have one set (Rocket Rons) which despite pumping up to 40psi on the rear (giving crap traction on the ups) I still pinched on cwmcarns descent.

    But a question, so I understand that being tubeless means you can run lower pressures so you don’t pinch a tube but, does that mean your actually more likely to damage rims? So if I pinch at 40psi with a tube in this scenario, if I’d been tubeless at 25psi would I be looking at replacing a rim?

    Am I talking nonsense?

    Premier Icon Garry_Lager
    Subscriber

    It must be true to some extent that lower pressures mean greater risk of rim-dinging, other things being equal. I would guess, though, that you’re looking at a very narrow range of impact between dinged-at-25-psi, and not-dinged-at-40-psi. So in practice I don’t think it would matter much.

    The other counter argument is that you run a lower pressure for greater control of the bicycle. So you’re already reducing the chances of a rim-dinger before you even start the descent.

    DT78
    Member

    Your probably right, greater control is a good point, but I mostly notice higher psi on climbs rather than descents. Its hard not to hit pointy rocks on cwmcarns descent whatever line you take…

    Surely if you pinch flat you’re in danger of dinging the rim as you slow down with a flat tyre so less likely to happen with tubeless?

    Premier Icon nuke
    Subscriber

    How narrow are your rims? When i ran tubes, I always found big tyres and narrow rims would up my chances of pinch flatting as the narrow rim didn’t support the tyre well.

    I was running a narrow rim with an Alfine…I converted the rim to tubeless with a rim strip making the internal rim width even narrower: it didn’t support the tyre very well and I ‘pinch punctured’ a few tyres 😳

    Premier Icon Northwind
    Subscriber

    It takes more of an impact to dent a rim than it does to pinch a tyre, mind.

    Tubeless are more resistant to pinch flats but you still get them, especially with low pressures. If you are riding hard then I find anything less than thirty psi will give me problems. IMHO and ime tubeless isn’t a path to running super low pressures, I run about 30 tubeless and about 35 with tubes. Of course with DH casings you can go lower without rolling, squirming or pinching problems and it will protect your rim more too.

    hexhamstu
    Member

    What width tyres are you running? Trying some wider and/or dual ply would definitely help out with the pinch flats. Another key bit of advice is to whack a load of talcom powder in the tyre with the tube, stops the tube from getting pinched as easy.

    Youll just end up splitting/pinching the tubeless tire or unseating it instead, tubeless is too fragile a system for square or sharp rock fests. I reckon your current tires are too fragile and/or small. Big downhill tires, DH inner tubes (at the back at least) plus green slime and the right pressure is the way to go for rocky descending.

    DT78
    Member

    Not a big bike – my race bike, scale in stock form with 2.1 R.Rons. So I know not designed for descending rock strewn descents (unless you’re a pro). I’ve always used light / small tyres on my old 26er anthem and rarely pinched so I didn’t think it would be such as issue on a 29er.

    Maybe tubeless isn’t the answer then, bigger tyres for a bit more give.

    Premier Icon kilo
    Subscriber

    Now on tubeless but before that used to use panaracers with tubes and, even as a big old lump, I found I could run them at stupid low pressures – people telling me I had a puncture low pressure – and not pinch them. Not massive rock fest riding but still found them to be very good in that respect

    jruk
    Member

    I’ve just moved to tubeless on the back of my Soul – Flow Ex, standard 2.35 60a High Roller, x2 turns of duck tape and Stan’s Fluid – as was always getting pinch flats.

    Only ridden it once but took it through a few rocky sections and no probs this morning. I’m ~95kg in my kit and reckon the pressure is about 30-35 psi (my pump has a crap dial so I go for the highly accurate thumbsquidge test).

    Not sure if that’s of any use to you though!

    Never had a problem with tubeless in the 1st 15 months of running them.

    Except for the time in Torridon when I had a big flat & couldn’t get the valve core out of the rim to put a tube in cos the lockring was SOLID….

    Cue, Torridon Mountain Rescue. 😥

    Premier Icon Northwind
    Subscriber

    esselgruntfuttock – Member

    Except for the time in Torridon when I had a big flat & couldn’t get the valve core out of the rim to put a tube in cos the lockring was SOLID….

    FWIW it’s worth having a crack at snapping the valve if this happens (I had a wee practice with some dodge valves, on one of them it worked, on the other it broke above the lockring which was no use but still, no worse off.

    I’m packing pliers now Northwind!

    Aah tubeless valves…. when they arent stuck they’re bloody leaking 😉

    Premier Icon johnhe
    Subscriber

    This sounds obvious, but when you’re riding a hard tail (especialy with 2.1 tyres) rather than a full susser, you have to lighten the rear end as you hit sharper edges. I run 2.35 tyres on my BFe at around 20-25PSI, but if you whack a sharp edge with your weight on the rear wheel/saddle, you definitely will pinch flat.

    That’s all part of the thrill of HT riding IMO – picking your lines to avoid flatting etc. However, I’ve never ridden Cwmcarns so perhaps this is all bollocks.

    DT78
    Member

    Yea I know to pick lines keep the rear light as much as you can. Not always that easy though on a track like twrch which is narrow and pretty rocky in places. According to strava I was around 23mph when I pinched so I kind of thought it was going to happen based on the last 2 pinches…. Reckon I’ll try tubeless for a bit…just hope I don’t start totalling rims. That’s more expensive than the odd tube.

    have run tubeless conversion on mountain bikes for the past 7 years on variety of rims including Mavic, Sun and Roval, and a variety of tires including Maxxis, Kenda, Syncros and Specialized Control.

    I’ve ridden these setups all over the UK, Europe and Canada on the most extreme terrain with no issues related to setup or failure of the tubeless conversion itself.

    can think of only 3 failures during these 7 years, all in the UK involving running over broken glass (broken wine bottle, broken beer bottle and broken pint glass) on the trail which literally cut the tire in 1/2

    @doug_basgueMTB

    how do you get a pinch flat on tubeless conversion? there is no inner tube to flat?

    however, could see this happening on Mavic UST as this relies on the rim/tire integrity to maintain pressure. If the rim or tire bead gets damaged it won’t hold air, hence the popularity of tubeless conversions which are much more tolerant of damage than Mavic UST.

    Hell, the UST guys often put some Stan’s sealent into the UST setup to try and minimize any damage leaks.

    bad setup is just bad setup. if the setup is good (holds pressure from initial inflation) and you check pressure before riding, you should not have any issues with a tubeless conversion

    Premier Icon Mugboo
    Subscriber

    My first ride out tubeless, new high roller 60a, plenty of fluid and I managed to flat on a sharp rock. Tyre went flat and eventually sealed. Just one more failure, similar incedent and my own fault because I hadn’t topped up the fluid from the first one.
    These are my only problems in 2 years.

    This year we had 3 very hard days riding around Glentress & Inners on very dry, trails. When I got home my tyres had numerous damp patches where the sealant had done its job.

    Only negative I can think of is I need to blow my tyres up a bit more regularly.

    @ esthershore the same way as with a tube except the tyre is pinched between the rim and a rock giving the classic snakebite two holes. You must have had that if you have been using tubeless, no? It’s my main form of failure with them. It is normally easy to fix with the sticky string tubeless repairs. I don’t like low pressures so hardly ever get burping. That’s using Stan’s and a variety of mavic rims with loads of different types of tyres.

    Premier Icon Mugboo
    Subscriber

    Where do you buy this sticky string stuff?

    Mugboo, you get kits of it from any bike shop now. I have a weldtite one which is good. Then on eBay you can buy the strings themselves separately. My lbs stocks just the strings. You can also get motorbike ones on eBay but I find the things you use to poke the strings and the file for opening up the hole are too big.

    Pinch-flatted a tubeless tyre this week and one hole is right on the edge of the bead. Would the string work in that location? Just assumed it was back to tubes for that tyre…

    Depends on the exact position but many times I’ve fixed holes like that with sticky string.

    cynic-al
    Member

    Try it.

    OP sounds like you are running the wrong tyre in terms of beefiness or volume.

    Anyone else thinking: “mtn rescue, for a puncture, eh?”

    Premier Icon Mugboo
    Subscriber

    Thanks Doug

    b r
    Member

    Except for the time in Torridon when I had a big flat & couldn’t get the valve core out of the rim to put a tube in cos the lockring was SOLID….

    Since that first happened years ago, I always carry a plier-based Leatherman.

    IME over about 3 years;

    95kg rider
    small variety of tyres
    small variety of rims
    all ghetto conversions
    30psi in everything except DH casings (then ~25psi)
    number of pinch flats = zero
    number of punctures = zero
    number of belch moments = zero

    actually, that’s a lie. I have had one failure, which was where I managed to fold over the ghetto’d tube, creating a crap seal which inevitably failed leading to “slow” (10 minutes) puncture. Easily sorted.

    YMMV, etc.

    Grum p
    Member

    esselgruntfuttock – Member
    Never had a problem with tubeless in the 1st 15 months of running them.

    Except for the time in Torridon when I had a big flat & couldn’t get the valve core out of the rim to put a tube in cos the lockring was SOLID….

    Cue, Torridon Mountain Rescue.

    Apologies if it’s been covered elsewhere, but I’m wondering why you had to call out MRT? It’s Torridon, couldn’t you have walked to the nearest road whilst a friend rode back to get the car? Riding solo, go to nearest road and hitch, or straightest line back to car. Stuff the tyre with grass and turf then ride home? You might trash the rim that way, but probably cheaper than pulling a few volunteers out of work/family time to go and pick you up.

    Or your friends with some of the MRT and you just gave them an excuse to go for a ride over to you with a leatherman 🙂

    To cover op’s qn, Of me and my assorted Chamonx based riding buddies there are far far less punctures on tubeless setups (Mavic UST and ghetto), and so far the only tubeless punctures that haven’t fixed themselves after leaving the bike with gunk have been when the tyre carcass has been slit wide open. You can still nick the tyre on rocks, though none of us have managed to snakebite the carcass. Our current thinking is slightly less pressure in a tubeless set up protects you more as the carcass is less taught when dealing with sharp rocks. Should also mention that we all run 2.3 to 2.5 wide rubber though.

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