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Riding back to Atlanta at 90 MPH on GA 400 I suffered an instantaneous loss of air pressure in my front tire due to the failure of my stem valve. This became apparent when I couldn't turn the front wheel. After gradually slowing down ( no brakes) and very gradually angling to the side of the highway I pulled off into the grass at about 20 MPH (too fast) and almost lost the front end during violent head shaking.

The bike is in my garage and I have one observation and one question.

1.In the future I will carry a Canyon Dancer (or similar) harness under my seat. I was on the side of the road for four hours trying to get towed because my free AMA towing connection couldn't find a single tow company who could strap down a sport bike without damaging the front fairings. I ended up calling a motorcycle tow company from Atlanta to come get me.

2. The tire looks perfect. Would anyone simply replace the valve and continue using the tire. I'm worried that I may have caused internal cord damage that isn't readily apparent.

This time I think I'll put on all-metal 90 degree valves that tread on from the bottom.

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No worries about tire damage. If the failure was instantaneous, you didn't travel far enough to generate any damaging levels of flex and heat.

Go for the Bridgeport angled valve stems. Solid aluminum.

Glad to hear you kept 'Er upright!

http://kurveygirl.com/shop/index.php?cPath=169_237_233

BPVS001_01.jpg

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total flat from 90 mph? with the front? personally, i would change that tire.

what a terrifying experience, and good on ya for getting her stopped without any more drama. i had a rear go at similar speed, and by the time i stopped it was very hard to keep upright. couldn't imagine what it would have been like with a front.

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My last bike, a Multistrada, had very nice solid 90 degree valves. I asked my Honda dealer if he had any valves like that when they were mounting new tires for me. The pictures show the aftermarket pieces they had. I thought they looked cheap, but I was in a rush to get the wheels back to my bike, so I took them. I've attached photos. The rubber ripped where it passes through the rim, leaving about 50 percent of the remainder attached. The dealer now sells the Ducati valves.

post-21103-0-52652300-1348762268.jpg

post-21103-0-30915400-1348762288.jpg

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My VFR failed inspection for bad stems. I told the donkey that they were good. He insisted. I put new stems on and the rear one failed 5 miles later. Good thing you can replace them without taking the wheel off or I woulda been more pissed.

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The dealer now sells the Ducati valves.

What are ducati valves? A Ducati wheel needs a different size valve stem that does not fit a Japanese wheel.

A valve similar to the 90degree valve stem in your first pic is also used on Goldwings, but it comes with a support that prevents it from bending due to centrifugal force.

The Bridgeport valves are the way to go, good quality and low weight.

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Congrats on keeping her upright! :fing02: I had the same thing happen on my commuter last year but on the rear....Being on the freeway at 5:15am I just scooted forward on the tank & took the 1st offramp about 3 miles up the road, it was a little loose on the right turn off the ramp :huh: but got a cup of coffee waited for the tow truck :schla15: got home ordered another tire, took the vfr to work :tour: .

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The dealer now sells the Ducati valves.

... but it comes with a support that prevents it from bending due to centrifugal force.

Isn't the fact that it requires a support an admission that it's not sound engineering?

A vertical valve stem is a bit of a pain to fill or check but centrifugal force just tries to make it shorter.

A 90 Degree valve stem is easy to check and fill but centrifugal force, which is oscillating with the frequency of the tire RPM is causing the stem to flex back and forth thousands of times per minute.

The moral would seem to be, replace your valve stems more often if you are using 90 Deg stems. The only problem is knowing how often.

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The dealer now sells the Ducati valves.

... but it comes with a support that prevents it from bending due to centrifugal force.

Isn't the fact that it requires a support an admission that it's not sound engineering?

A vertical valve stem is a bit of a pain to fill or check but centrifugal force just tries to make it shorter.

A 90 Degree valve stem is easy to check and fill but centrifugal force, which is oscillating with the frequency of the tire RPM is causing the stem to flex back and forth thousands of times per minute.

The moral would seem to be, replace your valve stems more often if you are using 90 Deg stems. The only problem is knowing how often.

Only the rubber mounted ones, IMO.

That's why the OEM Honda 90 stems included the plastic support piece. But I'm sure they spec'ed a replacement interval regardless.

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snip

A 90 Degree valve stem is easy to check and fill but centrifugal force, which is oscillating with the frequency of the tire RPM is causing the stem to flex back and forth thousands of times per minute.

snip

Why would the centrifugal force oscillate?

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Not a fun thing at all. Loosing front air is a much different animal!!! :ohmy:

My front stem failed at 70 on Interstate 40 thur DT Nashville and it felt like the head bearing just froze solid and seemed like I had No steering input. Almost impossible to change direction, slowed as much as possible in a straight line and ended up against the inside wall waiting for a break in traffic to cross the hwy.

I think doing constant long duration wheelies (front wheel stops rotating) combined with running a chromed capped valve stem, thinking the extra weight on the stem caused major fatigue when the stopped wheel was instantly spun up to 70 mph or more when the tire touched earth again?

Haven't stopped the wheelies, but don't use those fancy chrome cap stems anymore.

BR

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snip

A 90 Degree valve stem is easy to check and fill but centrifugal force, which is oscillating with the frequency of the tire RPM is causing the stem to flex back and forth thousands of times per minute.

snip

Why would the centrifugal force oscillate?

Yes, you're absolutely right, the centrifugal force doesn't oscillate. I was thinking but failed to transfer to writing, that gravity will be oscillating with the RPM of the wheel. Much lower force but still probably a factor. The other force is, due to being unsprung weight, any road imperfections or even slight tire imbalance will also add to the forces/oscillation. Now we're really splitting hairs. :rolleyes:

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I had this happen a few years back coming down the mountain into Sunland.

Going into a sweeping left the front got real heavy, didn't want to turn.

I used my CO2 canisters to fill it partway a couple times, but once I got going it went flat pretty quick again.

Probably rode a couple miles or so on it flat. The shop said the tire should be OK, which I found hard to believe, having killed a car tire in a couple blocks.

The tire was fine and I got quite a few more miles from it. :smile:

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Sorry, I'm going off topic a bit, but I think still somewhat related.

On my last tire change, the guy who changed the tires threw in a new straight valve stem. When I put the rear tire back on, I noticed the cap was hitting the bottom of the break calipers housing. I took the cap off, and it cleared the calipers. I've gone throughabout 70-80% of the tread on that new tire. and the air holds. Anybody know if there's anything wrong with not using the cap?

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Cripes, am I lucky or what? I'll be riding motorcycles 61 years next month and have never had a tire valve stem or the valve itself fail. Could happen tomorrow I suppose. But it's a good idea to have metal caps with an O ring seal on valve stems. The caps keep crud out, which would blow into the tire when you add air and more importantly may block the very small sealing area of the valve core. The O ring in the cap is a back up to the valve sealing air in the tire. BTW: I would not trust a motorcycle tire that had run flat for any distance! There are very likely broken cords in the casing that you cannot see. Good fortune, R3~

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  1. Those real large 90 dgree stems , Ive seen loosen from centrifical force, Id use the Girl Gurl ones, or small as possible with double sealing on both sides. Some day I'll get those, but I havent had issue with the short rubber stems. Ive got a few left to use, then I'll probably spend the big buucks on those tiny angled stems.

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No worries about tire damage. If the failure was instantaneous, you didn't travel far enough to generate any damaging levels of flex and heat.

Go for the Bridgeport angled valve stems. Solid aluminum.

Glad to hear you kept 'Er upright!

http://kurveygirl.co...ath=169_237_233

BPVS001_01.jpg

I had one of these to fail a couple a weeks ago headed to meet Keb for a DRAGON run. The vavle itself broke inside the tire vavle.

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Sorry, I'm going off topic a bit, but I think still somewhat related.

On my last tire change, the guy who changed the tires threw in a new straight valve stem. When I put the rear tire back on, I noticed the cap was hitting the bottom of the break calipers housing. I took the cap off, and it cleared the calipers. I've gone throughabout 70-80% of the tread on that new tire. and the air holds. Anybody know if there's anything wrong with not using the cap?

At high speeds, centrifugal force could possibly cause the valve stem to compress its spring and crack open. I don't know how possible, nor how fast you'd need to be going, so take it for what it is.

As well, dirt and water will get into the valve stem.

I would have it changed out and use the proper shorty stem.

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No worries about tire damage. If the failure was instantaneous, you didn't travel far enough to generate any damaging levels of flex and heat.

Go for the Bridgeport angled valve stems. Solid aluminum.

Glad to hear you kept 'Er upright!

http://kurveygirl.co...ath=169_237_233

BPVS001_01.jpg

I had one of these to fail a couple a weeks ago headed to meet Keb for a DRAGON run. The vavle itself broke inside the tire vavle.

Well I guess anything can break, but I've had no problems with mine so far.

And I've had them on for probably 5 years I'm guessing?

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