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IRC TR011 on CRF230

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hey all,

This is my first post on the 4-stroke trials forum. So please bare with me while I ask this question.

I just had an IRC TR011 trials tire installed on my CRF230. I do alot of trail and single-track type riding, and I must say I was quite surprised at how well this tire hooks up! I'm riding up stuff I couldn't make before! This is no doubt one of the best purchases I've ever made for a trail bike.

I had the bike shop install an MSR Ultra Heavy Duty tube. After my first run today, about an hours ride, I got back to camp and my son had noticed the valve stem had twisted, which means the tube has slipped.

I'm at home now looking at the valve stem right now. Here's the visual.. I rotated the tire so the valve stem is at the bottom of the wheel. The stem is angled forward, which means the tube had slid forward (?).

I was told that using this Ultra HD tube with the trials tire at such low pressure is the right combination. I am using a rim lock too.

I started out using about 11-12 lbs. of air pressure so I could get used to the feel of the tire. I _was_ going to lower the pressure later on, but I cannot get tire guage or pump on the stem.

Should this have happened so early on it's initial ride?

I'm going to bring the tire and wheel back to the shop tomorrow. I want to make sure they installed the right tube.

tia,

Bill

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A competion trials tyre has soft rubber like a road racing compound,with lower pressures it will mould to the surface and grip like no knob will.You'll tear it to shreads,but it'll be fun.Two rim locks are standard on a trials bike,one may not be enough,but tube creap is common - leave the stem nut loose to allow it to move without ripping it out.When using a trials tyre for non trials use we used to say your weight in stones is the pressure in pounds for a starting point.If you weight 9st,use 9lbs for a start.

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When using a trials tyre for non trials use we used to say your weight in stones is the pressure in pounds for a starting point.If you weight 9st,use 9lbs for a start.

Thanks Motu. The only thing I don't understand is the last part you wrote. I don't understand what "weight 9st, use 9lb." means. Can you explain?

I'll get another rim lock too.

Thanks

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Thanks Motu. The only thing I don't understand is the last part you wrote. I don't understand what "weight 9st, use 9lb." means. Can you explain?

I'll get another rim lock too.

Thanks

Looks like 'stone' is a U.K. weight measurement equal to 14 pounds.

From Ask Geeves:

14 pounds ( lbs) = 1 stone used in body weight = 6.35 kg...

All of my Trials Tire experience is on Trials Bikes. The standard starting pressure is 4 PSI (pounds per square inch) in the rear and 5 PSI in the front. A little higher by maybe 1 pound in dry rocks and up to 1 pound lower in mud and slick rocks. 1/2 PSI can make a big difference. Generally speaking, the radial tire does it's best when it can deform and shape itself to the irregular surfaces of the ground. Using one on a non-Trials Bike will require compromises. Carry a tire pump with you and a low pressure guage. Vary the pressure up and down to suit your speed and terrain and carry a spare tube. I would try to stay as near to 8 PSI as you can for starters.

All modern Trials Bikes that I know of use a tubeless RADIAL rear tire and a tube Bias Ply front tire. I haven't seen a tubeless front tire in many years.

I believe there is a difference in the tire bead between the tube and tubeless versions making it difficult to seat a tubeless tire on a tube wheel.

Some of the flat tires experienced during my early Trials years in tube tires was from the tube stem getting torn as the tube would "creep" around inside the tire under low pressures. The rim locks would also contribute to pinching the tube or chaffing. Most of my flats were actually caused this way AT the rim lock.

The newer tubeless Radial Trials Tires use no rim locks and of course no tube to get pinched. If the tires tries to 'walk' around the rim, it does no harm. On rare occaisions, the tire bead can be pushed in far enough to allow most of the air to escape. Usually, the tire bead reseats leaving you wondering what caused the flat when you look for the leak.

I'm not so sure that the super heavy tube under low pressures might have more of a tendency to squirm around in the tire and could be more prone to flats. We used to look for the lighter more flexible tubes but rim lock pinches and abraision was still a problem over time.

Good luck :thumbsup:

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I'm at home now looking at the valve stem right now. Here's the visual.. I rotated the tire so the valve stem is at the bottom of the wheel. The stem is angled forward, which means the tube had slid forward (?).

Believe it or not, that is the most common way the tube slips. But slipping might not be what's happening. There is a term called tube creep or crawl. Under the low pressure flexing, a stiff tube can work it's way around inside the tire much like a caterpillar walks.

However, under braking, the rear tire is light. If it locks up and then skips along slipping and then hooking up with little or no weight on the tire, the tire can slip in the braking direction. It is very rare to see one slip in the power direction as bike and body weight contribute to pressures to hold the tire tight.

Some old tricks to stop this were small sheet metal screws in the side of the rim at the tire bead to bite into the tire bead from the side and using a spray tire mounting lube/glue. Slippery until it dried and then it was like a glue. I have used the lube/glue but never tried the screws.

As Motu said, do not tighten the valve stem retaing screw, this will allow the stem room to tilt instead of tearing the tube. Loosen the rim lock as far as you can, let the air pressure out, Push the rim lock in to break it's grip, break the tire bead loose from the rim and then rotate the tire and tube until the stem is straight again. You may have to put the bike in gear and use quick jerks to get the tire to move. Then you should be able to use the tire gauge and pump again. :thumbsup:

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Looks like 'stone' is a U.K. weight measurement equal to 14 pounds.

From Ask Geeves:

14 pounds ( lbs) = 1 stone used in body weight = 6.35 kg...

I weigh about 185 lb. That's about 13.2 stones.. ? Guess I'm a pig! :thumbsup:

So that would be 13 lb in the tire?

---------

I'm not running a trials tire in the front. Only the rear.

Sounds like I'm in deeper than I imagined. I like the way this tire works. I understand it's better for the dirt than knobbies. So i want to keep it.

Guess I have some schooling to do, eh?

Bill

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We used that formula when running competition trials tyres on 1/4 mile dirt tracks,4.00x18 front and rear.You need more pressure for more weight,hence going by body weight - it will depend upon terrain too.If you ride in an open area with a hard surface you will need more pressure than slow going on a soft surface,to protect the tyre from damage.When running a competion trials tyre on the street I ran 20 - 25 psi,because of the compound you can set up slides like a motard.You can certainly use them for more than trials,a much better tyre than anyone gives them credit for.

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