[kestrel242]

I'm in need of some advice from folks with more experience running a Quasi-Moto tubeless. I run a ZTR 355 650b front and rear on my Mojo SL, with a Neo 2.3 in front and a Quasi-Moto running tubeless with Stans on the rear.

Twice now, the Quasi-Moto "exploded" spectacularly. It basically blew off the rim with a loud bang. Once when I was doing a max-torque effort out of the saddle, and once last weekend while I was cruising downhill doing nothing particularly challenging for the tire. Between the first blowout and the second, I had applied a second layer of Stan's yellow tape, thinking that maybe I needed to build up the bed of rim a hair. Obviously that didn't work. Now I'm thinking of trying a roll of Velox or weatherstripping under the tape to hopefully help the rim get a tighter grip on the bead.

Anyone with prior experience with tubeless Quasi-Motos care to comment? Am I on the right track here?

(On a side-note, one thing that's kind of interesting is that so far the Neo-Moto is working just fine as is and never gave me an inch of fuss)

 

[laffeaux]

I've been running a Quasi tubeless on a 355 rim for about a year and a half without issue. I've not used any excess tape to build up the rim. I did have a bit of trouble getting a Neo Moto to initially seal - it had a slow leak for about a month (I had to pump it up before each ride) before it finally sealed properly.

I'm curious if anyone else has had issues.

 

[DekerfTeamST]

No issues here running Quasis front and rear on 355's. I've also ran Neo 2.1's front and rear on the same rims. Both set-ups are tubless with yellow tape. When you're mounting your tires are you inflating them with an air compressor until you hear the beads pop into place? It sounds like maybe your bead isn't fully hooked in the rim. How much air pressure are you running while riding?

 

[kestrel242]

No issues here running Quasis front and rear on 355's. I've also ran Neo 2.1's front and rear on the same rims. Both set-ups are tubless with yellow tape.

Hmm... that's interesting that the issues I'm having seem to be the exception to the rule so far.

When you're mounting your tires are you inflating them with an air compressor until you hear the beads pop into place? It sounds like maybe your bead isn't fully hooked in the rim.

I do use an air compressor and they do pop very audibly into place.

How much air pressure are you running while riding?

At the time of both events, I was running 38-40psi.

 

[coolhandluchs]

Too much pressure

Reading though the instructions, 40psi is the max pressure for seating the bead during installation. Just a guess, but you should probably be under 35 psi for riding. Most people I know running Stan's (on all sorts of wheel sizes), are at or under 30psi.

http://www.notubes.com/support_detailed.php

 

[DekerfTeamST]

Reading though the instructions, 40psi is the max pressure for seating the bead during installation. Just a guess, but you should probably be under 35 psi for riding. Most people I know running Stan's (on all sorts of wheel sizes), are at or under 30psi.

http://www.notubes.com/support_detailed.php

I agree. Seat the bead at the upper psi and then lower the psi to riding pressures. I'm running about 28psi. That's the advantage of running tubeless is to be able to run lower pressures for better traction and smoother ride.

 

[kestrel242]

Reading though the instructions, 40psi is the max pressure for seating the bead during installation. Just a guess, but you should probably be under 35 psi for riding. Most people I know running Stan's (on all sorts of wheel sizes), are at or under 30psi.

http://www.notubes.com/support_detailed.php

I appreciate the response. However, it would defy engineering common sense if the official max tire pressures listed on the rim are actually unsafe to use. There has to be a sensible safety margin to account for temperature changes, pump gauge error, and so on.

I've used various combinations of tires on my 26 or 29" ZTR 355 or ZTR Arch rims without ever experiencing anything like this, so I'm inclined to suspect that either something is wrong with my rear rim, or perhaps the bead on my particular Quasi-Moto is unusually loose.

 

[salimoneus]

at first it might not seem to make sense that higher pressures could be the reason, but it's possible. after a burp the tire would more violently try to re-seat itself, and the increased pressure could potentially blow it past the seal. most likely either the tire or rim is just slightly out of spec, and the higher pressures are just not agreeing with the combo.

it's a dangerous proposition to be testing different scenarios if blow-offs are occurring, but it might be worth a try to run ~30psi and see if the issues goes away. i think one of the great benefits of tubeless is being able to use lower pressures anyway and typically run ~25psi

as far as i know, the 355 as well as all of Pacenti's tires have very good success running tubeless.

 

[88 rex]

Hmm... that's interesting that the issues I'm having seem to be the exception to the rule so far.

I do use an air compressor and they do pop very audibly into place.

At the time of both events, I was running 38-40psi.

Too much PSI. I have been running a Quasi tubeless for about a year on a 355 without issue. I've also been running Neo's tubeless for something like 2-3 years and the ONLY time I had a tire blow off was a Neo with too much air. It was one of my first times setting it up tubeless and I let it sit in the garage with 40+ psi and it exploded. I re-seated it and never inflated it above 35 PSI and never had a problem again. I never ride over 30 PSI and find my sweet spot to be 25-28ish.

 

[ljsmith]

I have used many tires tubeless, but I just tried a Quasi on a Stans Crest and it did not go so well. I used a compressor and pumped it up and it seated with audible pops. I filled it to 40psi. Then I did the whole shaking routine. While laying in its side it would lose all air in about 5 minutes. So I refilled it several time and repeated and it kept losing air. So I decided to shake it for longer and while shaking the tire blew up (off) in my face. I guess 40 psi is too much to use with a Quasi. I decided to go with a Racing Ralph instead.

 

[650bee]

Air pressure depends on rider weight. Little guys can ride less air then big guys. I'm one of the later and I run mine 33/35 front/rear. No problems at all doing this. Stans has a chart on their site showing rider weights and air pressure.

The OP may have a loose tire. I had a Neo that burped a few times (on a Stans 355) and when I finally took it off, it almost fell off on its own. It was an old, well used tire so maybe it stretched out? Anyway, I mounted up a new one (which fit tight like you'd normally expect) and no more problems. I've had similar stretching a few times on road tires over the years - nice tight fit when new but loose, real loose, when old and worn out.

When you mount tubeless, wipe the bead down, both sides, with water. Just a bit of moisture helps the tire bead to slip into place and seat easily. I usually go up to about 25 pounds and inspect both sides to see how its starting, then pry it around a bit if its not looking good. Then I go up to 40-50 pounds to seat the bead completely. Wear glasses and gloves when you do this.

 

[gthcarolina]

No problems here.

I've got a quasi on a 355 rim with yellow tape and a ghetto valve. No issues. I also used a Neomoto on same rim with the same results. I have a 26 Crow tire on the rear on the same rim (smaller of course) and it was not easier to mount even though it's designed as tubeless tire.

I AM having trouble mounting -and blowing off- road tubeless tires, but that's a whole different thing.

Those blowoffs do scare the pi$$ out of you, don't they?

 

[JMac47]

Contrary

Air pressure depends on rider weight. Little guys can ride less air then big guys. I'm one of the later and I run mine 33/35 front/rear. No problems at all doing this. Stans has a chart on their site showing rider weights and air pressure.

The OP may have a loose tire. I had a Neo that burped a few times (on a Stans 355) and when I finally took it off, it almost fell off on its own. It was an old, well used tire so maybe it stretched out? Anyway, I mounted up a new one (which fit tight like you'd normally expect) and no more problems. I've had similar stretching a few times on road tires over the years - nice tight fit when new but loose, real loose, when old and worn out.

When you mount tubeless, wipe the bead down, both sides, with water. Just a bit of moisture helps the tire bead to slip into place and seat easily. I usually go up to about 25 pounds and inspect both sides to see how its starting, then pry it around a bit if its not looking good. Then I go up to 40-50 pounds to seat the bead completely. Wear glasses and gloves when you do this.

Reading the OP's post(s) it seems he's knowledged in tire mounting game.

And while we're at it, let's keep in mind these are not tubless or tubeless ready tires we're talking about here. From what I've seen over the years it's been pretty minimal the amount of "issues" people have had. Not a 650 specific comment here but I've had Neo's, Nev's, Wierwolf, Wolverines etc mounted tubeless and the ones that seemed to be the trouble(some) have been a couple different Spec 2Bliss tires. in both 26 and 29" versions. Not diss'n the Big S love their tires! :thumbsup:

Just say'n
And as for rider weight, as a "light" guy, I am quite often amazed at some of the psi's I've seen bigger riders run.