if it takes 50 psi to pop on the first side of the tyre bead and it comes off at 7psi there is someting wrong here other than the obvious.mine go on at that i run at 4.5 to 5 and weigh a fair bit more, cant remember the last time one came off without a puncture.

when do you measure 7?

I measured it as soon as I blew it back up...

so have you put the back wheel in water to see if its going down slowly? the famous leaking spokes?

Ya know what... No I haven't! I shall do that and see.

That is pretty odd, usually you need to work pretty hard to get a tire off the bead

If it was loose on the bead the tire would probably spin on the rim, try marking the tire at the valve stem

When you put it on what did you use for lube?

Some sealants become lubricants at high pressure, it puts a barrier between the rubber and the rim

I would remove, clean thoroughly with wire brush and pressure washer and reinstall with tire soap

The tyre was already fitted when I bought the bike so I'm not sure exactly how it was fitted. But I do know that it hadn't seated properly on the rim. I had to put 50-60 psi into it to get it to seat!

I'll try taking it off and cleaning it up like you suggest.

Ahhh, I always try to take out human error as a factor, people do stupid stuff, maybe they used grease or chain lube or whatever to seat the bead

Often the best way to diagnose is to decide what is NOT the problem and start at the simplest most obvious thing (Occams Razor)

#1 Installation issues

#2 Rim problems, bent rim, aftermarket parts etc

Still have problems it must be the tire, it's hard to tell visually if the tire bead has a problem

Does the tire come off the same side every time?

A good scrubbing and pressure wash of both the tire and the rim (along with a visual inspection) should eliminate 66.6% of the potential

Ahhh, I always try to take out human error as a factor, people do stupid stuff,

So a bent rim (with the very unusal ability to leak) is more likely than a leaking rim tape?

Edited September 23, 201213 yr by nigel dabster

Have you just purchased this bike with this Pirrelli already fitted?

Reason I ask is nobody runs a Pirrelli nowadays so possibly it's been put on to sell the bike and the tyre has been in stock for many years and is suffering from old age.

What bike is it? Some wheels do measure a bit too small. Some were stopped on warranty but I guess a lot slipped through the net.

Personally I would sell the Pirrelli or stick it in the back of the shed. Then buy a Michelin and see how you go with that.

Also I'm not telling you your business but to run 7 in the rear at your weight is hopeless. I weigh a fair bit more than you and will rarely go above 4 psi.

you do get pirelli tubeless trials tyres, i didnt think you did

http://www.trialsuk.co.uk/products/trials-rear-tyre-tubeless-40018-mt43

I'm still confused by this as I've never heard of Pirelli bringing out a tubeless version of the MT43 - their original MT73 tubeless was discontinued years ago as far as I know.

I had a look on their website out of curiosity and the product info for the MT43 doesn't mention whether the tyre is designed for tubed or tubeless, nor does it say that there are two versions, tubed and tubeless. There are dealers advertising them as tubeless but one tyre can't suit both surely, due to the bead design, unless Pirelli have found a way around it (I had heard talk that Michelin were going to bring out one tyre that would fit both tubed and tubeless rims - be good if they did as their tubed tyre is worse than a Pirelli in mud...)

Getting back to the original question, the fact that it seats onto the bead at only 40/50 psi suggests that it isn't tubeless as they normally take much more psi than that to seat. And the fact that it is being knocked off at 7psi simply from landing sideways suggests the same - look at the forces trials tyres face in WTC from some of their landings.

If you want to continue with the Pirelli, I think I'd phone Pilrreli themselves and get clarification on it due to the lack of product info on their website, because if it is a tubed tyre in construction, you aren't going to overcome the problem.

As reagrds a Pirelli for trials use, as said before, they are way off the effectiveness of a 'proper' trials tyre in terms of grip and performance, so it depends on what you're using the bike for as to whether a Pirelli is the correct choice of tyre. Trail riding yes, messing about playing on a trials bike yes, but trials competition no, unless you're not bothered about handicapping yourself compared to the rest of the field - they'll work, but nowhere near as good as the Michelin/IRC/Dunlop.

As Timp said, I'm not about to tell you your business, but with due respect, if you're running a tyre, especially a Pirelli at 7psi, grip is going to be non-existant. A Michelin X-lite at 7psi with one of the top lads isn't going to find that much grip. If you feel that the Pirelli is providing grip at 7psi, you're in for an eye opener if you run a Michelin/IRC/Dunlop at 2 or 3psi......

pirelli used to sell two types of mt43 rear's as TT (tubed) and TL (tubeless) - then about 4 years ago (can't remember now but i was working for watling tyres at the time) they stopped and issued the new ones as both TT and TL. ie they used to be physically stamped on the tyre wall as TT or TL, now it says TT & TL. now they've been like that for some time with no reports of greif (untill now...)

as above for competition use the everyone is using michelin x lights, x11, dunlops and IRCs (pro and cons to all re price and suitability tot he terrain your ridding). the pirrelli is cheaper and great for enduro bikes, trail bikes, pre 65, real cold weather and road use, etc. beyond there 5 tyres a variery of cheap buget trials patterns exist that are really uncompetive but cheap (and thus have their uses)

My friend had exactly the same problem , the side walls are that hard it was like he still had 50psi in it when he rode it. It also used to pop of the rim as well he ended up selling it and fitting a Michelin .

Ok so... Just to prove im not being a numpty i took a couple of pics of the sidewall.

But before i say anything else i think im gonna have to bite the bullet and get a different tyre for reasons i shall explain in a min..

If i keep the tyre inflated way past what it should be there is never a problem with it going flat.

However i attended the Westmorland Club trial at the weekend (as a spectator because my leg is broken) and rode around the course following my friends. I started the day with my tyre set at around 5-6psi because i wasn't doing the sections but i still needed some grip to get up over the fells.

Come the 3rd lap sure enough my tyre was like a damn pancake BUT still affixed to the bead!. Now here's the thing, because Ive tried it!

If i go ride some trails and keep the tyre semi hard it stays up no problem all day, every time without fail.

As soon as i let the pressure down to what its 'supposed' to be i end up with a flat.

The only conclusion i can come too is on a section say riding across the face of a hill the tyre is folding under and letting the air out of the bead. I cant see any other explanation! Because if i keep it hard it stays inflated!

Sounds like the IRC problem. They stay up without issue at high pressure but at normal riding pressure it deflates with use.

Anyway looking at that tyre tread its well worn so not a major loss if you fit a new one.