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Tubeless Burping
NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.
I've got my shiny new Nobby Nics and thought I may lose my tubeless cherry by converting soon. However, after much forum reading, burping seems to be a problem for heavier blokes like myself (circa 90kg inc gear) when running anything below 30PSI.
My concern is, by having higher pressures to avoid burping does this not negate the benefits of running tubeless by benefiting from lower pressures?
As usual your combined wisdom would be greatly appreciated.
PS. I'm running Mavic EX729 (26").
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I've been riding tubeless for about four years now on both UST and non-UST wheel sets and have never had a problem with burping.
I ride mainly XC and run my tyres at anywhere between 25 and 30PSI and weigh about 3kg less than you.
I don't know if burping is also related to tyre selection, however, I always use UST tyres. Currently running Maxxis Crossmarks and Ardents.
I popped my tubeless cherry with a couple of Fat Albert tyres and it sucked, pumped the first one up and boom, blew off the rim and I was a sticky mess.
Tried it on the trail(100kg, Flow EX rims) tyres leaked goo so I pumped the pressure up as you have said and it rode far worse than tubes, then I sliced a tyre so I threw them both in the bin.
Moved to a Spesh Butcher SX casing, it had fantastic grip but the casing didn't seem to be able to keep up with the available grip, the tyre started gradually weeping goo in technical sections then it started leaking through the sidewalls. So now it has a DH tube and I have to run 28Psi in it as a front, for me a DH casing Minion works tubeless but any lighter tyre seems to suck and I lose traction over running in normal AM style casings.
I know I am an exception to the rule as 90% of people love tubeless, I probably should just lose some weight hahaha!
I think the rim profile is more important than the tyre. I have Stans Flow rims and the tyre locks into the rim and takes quite a bit of force to dislodge, even if fully deflated.
Running Hans Dampf tubeless ready (the cheapest version, not the proper tubeless one) at 18psi on the front and non tubeless Crossmark at 25-30 psi on the back. Also used proper tubeless rim strips that overlap the tyre bead. I am around 90kg with gear and have never had a burp or deflation. Had a couple of punctures that sealed pretty much instantly.
Used to buy tubes in boxes of 10 until i went tubeless and never had a puncture since (but have had the sides rip out of a tyre which was a walk home). Mine are tubeless ready (TR) rim and TR Nobby Nick / RR - and no more pinch flats!!!
As above I have also had a tubeless tyre pop off a rim under inflation and was vey scary.
Interestingly love to understand the desire to run low,low pressures - I run minimum 30 PSI for faster rolling and have had no probs with traction at trails like Manly Dam and Terry Hills - my only compliant is harshness on tracks like centre when you take a big hit.
If I race at the Fling I will have 38/40 in the rear and 35 at the front - Love to hear the benefits of low pressures from the forum...
I must be doing something wrong.
I currently weigh 93kg without the bike.
I have been running tubeless for 4 years and have only burped once in Glenrock. But I run 30psi front, 40psi rear on 29ers.
I think it is a fallacy to think you can run 29ers at really low pressures.
Grip, grip, grip and grip.
Make that 4 reasons.
~100kg with gear and I run 23 front, 28 rear. NEVER burp. Same pressures on the rigids, the hardtail and the dually. All 29ers.
I may occasionally run 2-3 psi higher all round if I'm going to say Perimeter & Long and want to roll a little easier, but that's the exception. Most of the time I don't bother.
I can really notice a couple of psi over inflation on a twisty, slippery track. Then I drop it down and attack with much more grip and confidence.
I'm around 83kg kitted up ready to ride. I've been running tubeless for 9 years and have burped only once when the front was somewhere around 10psi.
I routinely run my front tyre at 20psi, sometimes a bit less, and the rear at 23-26psi depending on conditions and traction. I use Stans rims on two wheelsets and Light Bicycles hookless on another. Prior to that, on the 26ers, Mavic UST rims.
My acquaintance Pierre is a big unit, weighs in well north of 100 kegs (120? loves his food, so he says
). He runs a dual ply 2.4 on the rear of his hardtail 29er at 25psi, and is the guy who inspired me to try lower pressures.
Watching him winch his way up the loose, steep pinch climb at the end of Long Trail in complete control and no fear of traction loss, nor of running out of legs, permanently re-wired my understanding of tyres, pressures and what a mountain bike rider's physique should look like!
My Goldfish is called Pierre, he's big for a Goldfish.
Suck it and see.
Depends on grip of surface, tyre size ( tight or loose) , tyre width, and most importantly, the rim.
It really depends on the skill of the rider, bike and track condition.
I have 3 bikes and set them all up slightly differently. I run them all tubeless
Rocky Mountain Element 100mm XC Bike, 24 front 30 rear
Intense Tracer 6inch all mountain, 26 front, 32 rear
Intense M16 DH bike, 28 front and 34 rear
You will notice as the travel increases so does the pressure. This is because the tracks get rougher and the chance of rim strikes goes up. I did 3 weeks riding some of the roughest tracks in Canada this year on the DH bike with carbon rims and never once had a problem. I am not slow either, I am the current NSW Vets DH Champion!
The faster you ride a bike the harder the hits your tyres/rims will take. The more pressure you will need.
I think sometimes people worry too much about running low pressure for grip, a skilled rider can generate grip just by body position on the bike! Set your pressures to suit your weight, bike and also track your riding!
"...a skilled rider can generate grip just by body position on the bike!..."
And therein lies the problem, DS. I don't have your mad skillz so I resort to tweaks.
I Run the NN snakeskin on the front. I weight about 85 kitted up.
I usually run 28-30 psi on the front at manly dam as below that I find I burp on the fast downhill section.Ive raced at Mt stromlo and use the same pressure there. It all depends on the trails your riding.
When on tubes I usually go 35 at the front 40 on the rear. But it may also depend on the geometry of your bike. I'm still riding a 26" anthem X where a lot of the weight gets transferred over the front wheel Its got a steeper head angle than the modern Anthems.
I would try it. If you do experience a burp. Upgrade to a propper tubless tyre.
I hardly get any flats these days. I prefer the feel of tubeless as well.
Whilst I agree that body weight does make a bit of a difference, most 'burping' incidents are just due to poor riding style. To load the tyre in such a manner that it would burp - unfortunately its rider error. If an inner tube is what is keeping your tyre aligned on a trail, you have bigger things to worry about than body weight (as per Hawkeyes post).
Different sidewalls will make a difference of a couple of PSI (ie you can run a stronger sidewall at lower pressure) - for me at 79g, I run a really racy tyre at 28psi but a stronger one at about 25psi (same width).
Take the plunge with the tubeless, make sure they are seated / beaded well, and dont go making 90 degree turns at the bottom of a drop-off with no weight on your back wheel. You'll be fine.
Poor rider technique is responsible for most burping incidents? If that was the case then I'd be having burping issues every time I rode.
Following is a link to a Pinbike article on the issue, it's a few years old but you might find it interesting anyway:
http://www.pinkbike.com/news/Tech-Tuesday--Wider...
I had burping with thin sidewall specialized eskar tyres on ghetto tubeless, but zero burping with stans flow ex and various maxxis tr and bontrager tr tyres. So I think it's about picking the right tyre sidewall for the job. Sometimes the same tyre tread pattern comes in a variety of casings. I won't win any XC races with all mountain style 800 to 900 gram single ply tyres, but they hold up well to 100kg rider doing bermy jumpy stuff with some rocks ie the type of riding I like. Tyre pressure 28 front 32 psi rear. Any lower and I can feel the tyre squirming.
As I've only just fitted these (with tubes) I'll see how I go for a while before shelling out the additional $130 - $150 for the Stan's kit. I'm running the front with 32PSI and rear with 35PSI. I may try experimenting with slightly decreasing pressures in the meantime.
Thanks again for all your input. It's been very useful.
Pfft, poor riding style causes burping.
Poor rim and tyre selection, maybe, too low a pressure for sure.
If my tyres burped it was when I was having one of my rare days where I'm feeling fast and the bike would be at decent angles in corners. A 42a Minion or similar can put a hell of a lot of load in to the sidewall and they will burp.
Get the Joe's conversion kit from CRC, under $50. Just make sure you get the correct kit for your rim width.
I wish I could as it's only $41!!!!! Unfortunately their biggest kit only suits rims up to 25mm wide. I'm using Mavic EX729 and they're 29mm...D'oh!!!
The 25mm is the inner rim width. My ZTR Flow rims are 28mm external but only 22mm inner width, and the AM kit fitted great.
They're big old rims so Stan's Downhill kit is my only option (and more than twice the price of Joe's).....bugger.
Yep had burping with nobby nic and i weigh less. But the snake skin version fixed that, but found the tyre pressures very sensitive to get the best grip.
The very best tubeless results come from proper tubeless rims with a proper tubeless tyre, with sealant. With that said, I've had excellent reliability, when faced with a wide rim, with ghetto tubeless conversions and wire bead Maxxis DH type tyres. I like Schwalbe BMX tubes for this. There's lots of tutorials on youtube. Then, remember to top the sealant up from time to time.
Your total mass won't effect reliability. Riding and turning and landing correctly does effect reliability. Your mass does effect required pressure. Don't get onto the low pressure bandwagon just because internet forum land says so. The tyre manufacturer knows best, and so does Stan. There is a body weight air pressure guide on Stan's website. Even if you're not using a Stan's product, read it, absorb it and experiment from there to find what works best.
You need to trial what works for you with your tyres on your bike on the trails you ride.
I spent a few rides experimenting when I found that the tyres I was using (Schwalbe) sucked with the pressures I had been used to running with Maxxis rubber.
I just kept going down until they got squirmy, and then came back to just before that point. I also change pressures depending on the terrain, going lower on loose sandy stuff and higher where there are sharp rocks and/or square-edged hits that might make me bottom out on my rims.
However, tyre manufacturers don't always get it right. The old Nobby Nics were nasty unpredictable mounted per the rotation arrow. Reversed, while not perfect, they were much more confidence inspiring when leaned over.
Wider rims give better sidewall support and less tyre squirm.