You are hereForums / By Discipline / Mountain (off road) / MTB Gear / Rear tyre almost rolling off rim.

Rear tyre almost rolling off rim.


Wavey's picture

By Wavey - Posted on 05 March 2017

I'm having problems with rear tyres coming close to rolling off the rim on my 27.5 Anthem.
I'm running Stans Arch EX rims, and used to run a snakeskin Racing Ralph 2.25, but due to this problem I've recently changed to an Ardent EXO TR 2.25 on the rear.
During high grip hard cornering off the brakes, the tyre rolls to the point where it is about to burp, but doesn't burp. All grip is lost for a second or so.
It happens most rides, tyre pressure is always between 30 to 35psi, running tubeless with stans sealant.

Any ideas?
More pressure?
Wider rim?

Cheers.

all74's picture

I see your rims are only 21mm internal which wouldn't help with 2.25mm tyres but that is almost just about exactly what I run (Spinergys and Nobby Nicks)and at much lower pressures. Unless your weight is getting up to 100kgs I would think the pressure is too high for tubeless, and maybe the round shape of the tyre is flopping around the rim rather than complying towards the rim when it gets sideways pressure.

Try with less pressure rather than more and see if it improves. Depending on you weight you should be able to go below 25psi.

all74's picture

dupe

Pete B's picture

It does seem a bit strange. I have the same rim with a crossmark on the rear and haven't had this problem. (82kg with 27ish psi)
Try a rear tyre with slightly less grip that may drift a bit but keep an Ardent on the front so you don't wash out.

hawkeye's picture

I've recently upgraded to the Stans Arch Mk3 rims on the Trigger and have found they are a significant improvement, being some 5mm wider on the inside width.

Mind that I'm comparing to 21mm i.w. Crests. Rear end flex (wheel or tyre) was noticeable with that setup and 2.4" tyres.

But the new wheels performed *really* well on the Thredbo all-mountain and flow trails last Thursday.

Wavey's picture

My weight is about 80kg, I originally used the stock non tubeless crossmarks setup tubeless, but these would burp during high grip conditions.
I then changed to the Racing Ralph, which was better, due to being a tubeless tyre, and now on the Ardent which I hoped would have more support with the stiffer sidewalls.

I've checked my pressure gauge against another, which was fine.
I've also tried running less pressure, but the squirming/rolling seems worse.

Maybe a wider rim is the answer..

Pants's picture

I've burped a double down maxxis aggressor with 28 psi. It was just down to cornering hard and getting a lot of grip = tyre completely folds and burp.

Solutions are:
corner slower (pfft!)
more pressure
huck norris / pro core

skipper_nz's picture

I am running 2.25 Racing Ralph, on a 19/21mm internal carbon 29er rim, 27-30psi at 90kg and have had the same experience, mostly at hornsby or stromlo, my only solution was to just back off a touch in the couple of places that i can feel it going.

MrMez's picture

You really only have 3 options.

-Higher pressure
-Smaller tyre
-Wider rims

Wider rims are the ultimate solution. I test rode a very capable enduro bike years ago with the usual narrow stans rims. Options were high pressure, low grip but stable and predictable, or drop the pressure and have the tyre collapse pumping berms or jumps. Made for some interesting landings.
As a comparison to the 21mm rims, I've been running 35mm internal width rims for the last 3 years or so, and people are now using 45mm internal width rims for the 'plus size' spec.

Wavey's picture

Rode 26km around Kalamunda yesterday, ran 32 front, 35psi rear.
I think it was slightly down on grip, but felt good as the rear end was consistent and didn't squirm around all over the place.

Keeping an eye out for some Stans Arch mk3 rims to come on special now...

pancakes's picture

Look, silly question, but it's not the pea gravel you're feeling is it?

I never had an issue there with tyre deformation/burping (or anywhere else for that matter) when running ~23/28.

100+kg
Hardtail 29er
Ardent Race 2.2 exo tr yadda yadda 23f/28r
Bontrager 23-24mm??? internal

I'm not a climber but I fang it down hill.

On a side note, I miss Horny Devil. How's it riding? And Flaccid Ashback, and Camakazi, and Feral Groove...and and and...

MrMez's picture

HT 29er. There's your answer.
Mountain biking is such a popular sport as there are a dozen ways to ride the same trail.
At 62kg i warped a brand new 26" (much stronger than a 29" wheel) in just two rides at Kalamunda. No mistakes, no rock strikes etc. That was while waiting for a carbon rim replacement I destroyed.

Riding hard with an under inflated tyre/narrow rim etc will definitely cause the tyre to collapse under load spikes.

fairy1's picture

If you go to a new tyre in the same model you may find that you can drop a Psi or two, I've found that after you get those fold lines in the sidewall that the tyre will no longer be as supportive as it once was. If I try a new tyre I'll start with a higher than normal pressure and drop pressure until it starts to squirm insyead of rolling it over then adding pressure.

As others have said your rim is narrow but it is still impressive that you are rolling an Ardent, as far as Maxxis tyres go they are one of the worst in the lineup.

A DH tube makes a pretty solid improvement to a weak carcass.

MrMez's picture

Good thinking on the DH tube!

Dee's picture

Can you run stans in the tube?

fairy1's picture

If you can take the valve core out I'd say yes.

I'm fairly sure I remember reading a couple of pro DH racers used to run tubes and sealant on the outside of the tube. That way if the tube went boom they'd have enough air to limp home, I guess it would act as a lube which may make pinch flats less likely...?

Simon's picture

I've run 2.4" on 21mm 26" and 2.4" on 31mm 650B.

I loved the low rolling resistance and ran 25PSI at 85kg. However I found they needed tacky dirt to hook up and they felt amzing. The high volume was also good. Never dinged a rim riding Bahai, Narra etc.

Any gravel, sand or slabs of sandstone and they skate out like hitting ice when pushed. Hence the hate. Felt like it was rolling, but not sure, may just be the soft flexy small side knobs. Also suffered from lack of grip on rock rolls, not great as a front tyre. At 35PSI I thought traction was worse.

Before you start messing around with rims, wheelsets or even Huck Norris, spend $50 on a Minion Semi Slick EXO if you want to stay with Maxxis. Or a Spec Slaughter (in GRID). Still a better tyre in my opinion than Ardent if you like climbing and descending and will suit 31mm internal no issue should you decide to go wider.

It rolls very fast and so long as you lean the bike the DH side knobs should give you massive traction. If you still have a problem then wider rims may be worth considering. It will have a bit less straight line braking but rolls fast and corners very well. Run a better grippy front tyre for braking.

fairy1's picture

Yep I agree with everything above, I currently have a 2.4" UST Ardent on the rear and I hate it, it's not Fat Albert bad but it's still pretty crap.

Wavey's picture

I can't see a wider tyre with more grip helping my situation. I've been rolling a 2.25 Racing Ralph nearly off the rim, and now an Ardent, both only in quick high grip situations.
I'm not prepared add the weight of a DH tube, or any tube for that matter, to the weight of my wheels. I can't see myself ever going back to tubes.
Looks like I will just run 35+ psi tubeless, until I can source a wider rim.

Cheers.

fairy1's picture

Yeah I tried that with a 2.35" Butcher up front, it was rolling and losing a couple of pounds on each short push run. It was no fault of the rim(Flow EX) it's just a weak carcass on the tyre and I find the Ardents I have tried acted in a similar fashion, only on the back though, I wouldn't trust them as a front tyre.

For me the loss in grip from running extra pressure was a much bigger disadvantage than a weight penalty that I didn't notice when I put a tube in, 28Psi and lots of grip for an AM tyre.

I used to have issues with 2 ply Minions rolling off rims and had a few punctures when the tyre goes in to the cassette, the rims were too narrow and slightly undersize in the radius department.

Running at higher than normal pressure will help you gain skills as it starts to feel normal, you'll later go to a proper rim and feel like everything is made from hero dirt.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
Best Mountain Bike