[Yellow]

One of our members has some good pictures (I think it's Yellow) of exactly this kind of situation that he went through last year -- coming through the Eiffel forest around a high-speed turn, he caught a big chunk of metal debris from a truck(?) that left a 2" x 1/2" gash in his rear tire clean through the carcass -- he managed to bring the bike down to a full stop because the radial tire held it's shape even with the damages.

Not me, I think it's Kwebbel you are referring to.

[harrye]

So radial tires are a great advance in motorcycle safety. They give you a better chance of being able to ride out a sudden loss of pressure.

Ok, so if you run for a long period with too low tire pressure, the tire could be ruined by the time you have the tire failure (sudden loss of large amounts of air, or tire coming apart).

But I was thinking that with too low pressure, the tire could be more prone to sudden pressure loss by just hitting a pot hole, etc., that could break the tire bead momentarily and release the air. In such case there might be no tire or wheel damage, and you just have to re-inflate the tire. But this "best of the worst" situations may not happen in real life. I don't have the experience to know.

I was also thinking that nail punctures on a cycle are so rare that one might conclude that they just don't happen. Has anyone ever had one?

As I understand things, when you drive over a nail with a car, the nail is laying flat on the road and doesn't puncture the tire on first contact with the tire. But the pointed end to the nail gets caught a little ways in the tread of the car tire, and the nail goes right around for one revolution or more. Then centrifical force swings the head of the nail outward, leaving the pointed end facing directly into the tire, and on that rotation of the tire, the nail is driven into the car tire.

So to have a nail puncture, you have to have a tire tread that first picks up the nail. Motorcycle tires, especially the high speed tires on sportbike, just don't have that kind of tread. Sportbike tires are a lot like rain tires on a race car. Mostly slick, with curved rain grooves. The odds of a cycle catching and picking up a nail in those kind of grooves are very slim. And maybe, unlike with a car, the weight just isn't there to pick up the nail in the tread in the first place.

So, has anyone every had a nail puncture on a motorcycle? With a sportbike?

You can always drive over sharp scrap steel dropped from a truck, but then, the tire may not be susceptible to plugging.

[Mojoe]

So, has anyone every had a nail puncture on a motorcycle? With a sportbike?

yup....twice...but not nails. One was a screw and the other was one of those big staples you see in big cardboard boxes. Both time it was on relatively new tires and both times I noticed by checking tire pressure. They both game me slow leaks. In both cases my tire pressure would not hold so I examined all the tire and found the culprits. Nothing ever came from it that caused me any danger on the road.

The handbook goes on to state: "If a puncture should occur, maintain a firm hold of the handgrips, but do not fight the steering to correct any wobble or weave that can develop. Avoid downshifting and braking until speed is low and under control. If traffic permits, slow gradually and move off to the side of the road. If braking is necessary, use the brake on the wheel with the good tire."

I am not sure I would put that advice in my head as the only advice. I will go with keeping a firm grip and avoid braking or downshifting.....but you kinda have to fight the steering in some cases. If I didn't with the cbr and the 95mph flat, the bike would have went straight for the ditch and I would have hit it at about 75-80mph if I let the bike run it's course.

[The CyberPoet]

Not me, I think it's Kwebbel you are referring to.

You're right -- my bad. It's the desire for those emblems that had me confused :P

So to have a nail puncture, you have to have a tire tread that first picks up the nail. Motorcycle tires, especially the high speed tires on sportbike, just don't have that kind of tread...

Motorcycle tires tend to work in unison to pick-up nails and other debris, which is why nail/screw/tack punctures are so common on rear wheels and so rare on front wheels. In most circumstances, the sticky rubber of the front embeds the object slightly, setting it into a flipping trajectory that sometimes happens to leave it pointed in the right orientation when it hits the rear tire -- and the rear subsequently gets a point-on puncture from it, with the screw/nail/etc going in fairly straight. I have had more of these kinds of issues than I care to even imagine -- at least a dozen of them in 20 years of riding (many before I learned my lesson about never stopping in the emergency lane of a highway or the debris sweep area of roads with shoulders). Part of it, I'm sure, is also because Florida is a high volume construction center -- in areas with less construction, there would be less construction debris (which is usually what nails & screws are).

Cheers
=-= The CyberPoet