Expanding on the title - after pinch flatting on Jacob's Ladder at 35psi yesterday, I'm thinking of going tubeless. The tyre is maxxis high roller folding, the rim 21mm internal measurement.
Never tried tubeless before, so the main question is, what's the lowest psi I could sensibly run with the above combo?
Would burping be a problem? (for the tyre obviously, for my own digestion that goes without saying). I read some articles that suggest it would.
Would a wider tyre help? Would a wider rim help? (Back wheel is nearly dead anyway so I could conceivably replace the rim at the moment).
21mm internal rim with 2.35"? HR should be miles from problematic in terms of pinching ime. XC717s around the limit for 2.35" (old tread) maxxis I reckon
What tubes though?
Not continental (upto 2.5") or bontrager (upto 2.35") were they? Both been a bit thin/small for me in the past
And what bike?
Hardtail and accidental heavy rear wheel weighting?
Full suss that doesn't ramp up much (or ramps up a lot very quickly) and not quite enough air that it could pinch partially due to the way the suspension 'works'
You can run the rear softer than the front, and once the tyres are well sealed (to the rim) then 20psi front / 15psi rear minimum - but tbh I usually run 25psi.
I find below 25 psi some tyres can feel a bit squirmy on the rim, even wide rims. I usually run 27 front, 29 rear or something similar
jacobs ladder eats tyres, tubes and wheels. it owes me loads of all 3, especially tubes.
you don't say your weight, but softer than you do now. there's a rough formula, from another thread, from Stan's:
To determine a starting tire pressure when running mountain bike tires tubeless on our ZTR mountain rims use this simple formula:Rider weight (with gear) in pounds divided by 7 = x
x - 1 = Front tire PSI
x + 2 = Rear tire PSI
i think wider rims help (think of it as pressing the rim through the tyre, rather than other way around - thin rim obviously to me goes through easier?) but Shiggy says no. wider rims def. make tyres more stable in corners though.
b r is on some craic running less on rear 😉
You can run the rear softer than the front
Interesting, I usually run the rear slightly firmer. My thinking being the front carries a little less weight, grip is more important at the front, and the rear has a tougher time.
What's the thinking behind running the rear softer?
he either endo's everywhere or he's worried about front end burping? dunno, don't recommend that.
I don't know how you guys run such low tyre pressures without it feeling horrible. When I go too low the tyres squirm around, the side knobs don't dig in and I get loads of dents in my rims. And that's running Maxxis Minion DHF dual plys on Stans Flow rims. I'm quite light at about 10 stone and I usually run 30psi rear and 25psi front.
easy
1) be light as a feather 😀
2) live without rocks 🙁
3) don't bash into stuff. if you were pinching at 35psi, you're now landing on the rim, esp. with Stan's you'll ding them, so learn to ride better. 😉
agree actually. i'd add about 4 psi to each of those stan's values? gets me about 21/24
27-30ish is about as low as I like out back (depends on the trail), 25 is as low as I go in the front. I also like the front softer than the back
If you bottom out a tubeless tire its still possible to "pinch flat". The rim just cuts through the tire..
Hmm lots of interesting things to consider here
@james (and others) it's a lightweight full suss - fsr xc with fairly soft tuning (for me) and I weigh about 85kg. So that stan's formula gives me 26/28. And yes it was conti tubes - what would you recommend instead?
@smiff (and others) learn to ride better - hmm I wish - not sure how I could have hit those rocks any less hard though really. On the point that I'll still be pinching, i.e. landing on the rim, whether there's a tube in there or not... good call. Maybe what I need is higher volume tyres, not tubeless? I've just switched from a 2.7 2-ply dh tyre (intense comp 60) which I used to run about 20psi but alas it was bloody heavy. Presumably higher volume can be run at lower pressure?
@everyone - so nobody thinks burping is an issue? I got the impression it might be on a 2.1 rim after reading this http://www.pinkbike.com/news/Tech-Tuesday--Wider-Rims-Are-Better-and-Why-Tubeless-Tires-Burp-.html
go tubeless, wide rim, stiffer sidewall tyre, maybe even dualply at back, and gradually drop pressure.
i'm not btw a great rider but i've talked to a few and the gist seems to be most pinching is caused by clumsy riding, not reading the ground properly etc. if you think you'll be doing that a lot, maybe go for mavic rim or something tougher than stans.
burping is an issue but less an issue than punctures imho 🙂
[i]he either endo's everywhere or he's worried about front end burping? dunno, don't recommend that.
[/i]
Because if its too soft at the front, it feels unstable - and if you lose the rear you slide, if you lose the front you fall off... 😯
@smiff - an expensive combination 🙁 I guess what I'd like to know is which of those four will have the greatest effect. i.e. is it worth going tubeless or should I look at the other three first. And why don't you mention wider tyre?
oh i thought you were getting new wheels.
yes a new bigger volume tyre is well worth trying. choose something with strong sidewall, not dualply if you ride uphill though!
the only time i've really had trouble with pinches was a worn out tyre in Afan that stretched (imagine a rubbery balloon, you press one place, the rest gets bigger, making it very easy to pinch flat). new tyre, no problems.
is your tyre worn? can you run your current rim tubeless? 21mm internal is not much different to a flow, it's not really narrow.
Might be replacing one wheel (a knackered cheap rear), though certainly not the other (nice new mavic front). My tyres are new as well - so it'll be a while before I go higher volume and light I reckon! I've always got the old 2.7 dh tyres for when I want them.
The current rim would need stan's kit to make it tubeless. But if tubeless doesn't really solve pinching then maybe I shouldn't be bothering.
Interested to see if james comes back and recommends a fatter tube.
"conti tubes - what would you recommend instead?"
Spesh 1.5-2.2" (Around 150g) I got on okay with 2.35" maxxis, could still pinch on occasion/stupid enough, but not like conti's
Kenda upto 2.125" Ive got onb better than contis, but still not great as far as I remember
bontrager upto 2.35" similarly disapointing to conti. Both being quite small a tube before strething and thin walled
For bigger tyres (maxxis 2.25"/2.5", michelin 2.15" etc) on Mavic XM719s I've tried raliegh upto 2.125" just because they're thicker, and a bit bigger volume before stretching (also heavier (about 210g) and cheaper feeling, ie dont feel quite as stretchy). They do okay, up front it takes quite a high speed rock pinch (think mount famine on jacobs loop) at 35ish psi to pinch, on the rear anywhere decently rocky and ridden with enough gusto they'll pinch (eg last bit of rushop edge before road)*
*Unless they were in Schwalbe Snakeskin tyres (2.25" alberts) which seem to do a good job at warding off pinches much better than folding maxxis/michelin
In the end I've given in and gone to FR/DHlite tubes. Maxxis Freeride (2.2-2.5") are okay and fit the tyre without stretching so much but are over 300g (about £9) and I reckon pinch more often than specialized 2.3-3" DH tubes (~280g) which are also cheaper. (£5-6 some places)
*all weights I'm only going off kitchen spring balance scales, so by no means accurate, just ball-park figures
Thick tubes not the best solution, I too would like to go tubeless, just no got round to looking into it properly yet
oh it solves pinch flatting, you just can't smash into everything and expect your rims to be fine 🙂 if your rims are ok and you just get the odd pinch, go for it (i run tubeless but to avoid thorn punctures and because it feels better).
Cheers all.
On reflection then I'm going to try some different tubes first and see how I get on - if only because it makes changing tyres less of a faff than tubeless.
Just ordered some spesh ones, both lighweight and downhill. Also remembered that talc powder inside the tyres is meant to help...
...and maybe change the cheap rear rim when I get around to it - compared to the mavic on the front it's actually got sharp edges which can't be a good thing!