90 degree valve stem is cause of flat?

Cameron

Joined
Nov 14, 2011
Messages
46
Location
Lafayette Hill, PA
Bike
'10 Silver NT700
I purchased and had installed, a 90 degree rear tire valve stem on 3/20 and have ridden without issue for the past 2 1/2 months. Today, on the commute home, after passing some slower vehicles at perhaps 50-60 mph, I slowed for an upcoming turn. The steering felt very strange - almost as if I was turning the opposite direction of normal. Took the corner very slowly - perhaps 10 mph and upon accelerating again, immediately noticed a strangeness in the steering again. At the first safe place, I pulled over onto the sidewalk and upon dismounting, looked at the front wheel, but noticed nothing unusual. A quick glance at the rear tire and it was obviously flat. Put the bike on the center stand and spun the rear wheel to locate the expected nail/screw, but found nothing. No cuts on the sidewall, so I was confused as to the cause of the sudden loss of pressure. Then I saw it - the rubber base of the 90 degree valve stem had pulled away from the rim - the obvious culprit. I'd been told previously not to attach any of the specialty stem caps - like dice, etc - as they can cause stem failure due to high centrifugal forces they create on the stem at high speeds, but I wasn't even going all that fast. Certainly, I'd ridden faster than that in the last 2 months, without previous incident.

Had the bike flat-bedded home - thank God for "AAA plus RV" which covers the bikes too. Now I'm looking at the NT700 owners manual and the replacement of a flat rear tire starts on page 187 and doesn't finish until 192. I'm amazed at how much they expect to be disassembled before you can get the tire off the rear spline. Does it really require remove of the exhaust system, wiring, etc?
 
Cameron said:
Does it really require remove of the exhaust system, wiring, etc?
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Well, no, but it is a PITA.

As to the cause of the flat, you've discovered why it's not a good idea to use a 90? valve stem mounted in a rubber base. You should replace it with an all metal 90? stem. And you may as well do the front one while you're at it.
 
One of the hazards of shaft drive bikes. Some can be a PITA to remove the rear tire, especially when you have all the plastic around them.

Of course, Honda made some design decisions that make it much worse. Like brake hoses that could have been an inch longer, or where they put the bolts for the muffler, and where they put the muffler, etc, etc.

Like any other bike, having a drop ramp makes it much easier, ie, you don't have to fool with the rear fender.
 
Cameron, There are a few shortcuts you can take -- others will chime in and tell you about them. I've never removed my own rear wheel, but I've had the kind of flat you've had.

Rubber 90-degree valve stems will inevitably fail, just like the straight rubber valve stem plus a light-weight 90-degree brass adapter that I bought from BMW and put on my '99 Kawasaki Concours back in about '02. It had been on the bike a little over two months. I pulled onto the interstate and engaged my Vista-Cruise throttle lock at 75mph and just as I took my right hand off the handlebar, I felt a quiver. I put the hand back on the grip and then ...WOW!... I pulled in the clutch and didn't touch the brakes. At about 35, I was very close to experiencing a tank slapper, but that eased as the bike slowed to a stop.

That little brass 90-degree adaptor didn't weigh much more than a cigarette, but it was enough to flex the rubber valve stem till it tore right at the rim. My hunch is that the weight of the valve part of the stem weighs enough to cause the rubber stem to flex.

What you need is something like this: http://www.motorcycle-superstore.co...L-Right-Angle-Valve-Stem.aspx?WT.ac=SLIsearch or this: http://bikeeffects.com/proddetail.asp?prod=119701

These are rigid and fixed to the wheel with a nut and a rubber washer. The do come in different sizes for different hole-sizes in the rims. Be sure you measure what size you need. They make a huge difference in checking tire pressures and adding air.
 
Why do they sell the rubber 90 deg stems if there are so prone to failing. Seems like a real safety issue. I would not think a dealer would even put them in.
 
Warren said:
Why do they sell the rubber 90 deg stems if there are so prone to failing. Seems like a real safety issue. I would not think a dealer would even put them in.
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Warren, I can guarantee that if I were a dealer, I wouldn't put them in! They could be killers.
 
I too had a 75 mph flat caused by a rubber stem. In my case it was a straight one, but each time I checked air pressure or added air, I had to bend it a bit to get access. Needless to say I don't use them any more.

This was on my last bike, a Vulcan 900, but on the NT, there seems to be a lot more room to get at the valve stem.
 
Gandalf said:
Just as a heads up: China has flooded the market with very weak and defective valve stems that deteriorate very quickly and leak. These are mostly used at automotive tire dealers. Most have learned their lesson due to the unhappy customers complaining. The problems have been discussed on tire forums and can be found on 'Google.'
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This is a big deal. A friend of mine had a sudden loss of air on his Harley that put him and his wife in the ditch at highway speed. He still takes meds to prevent seizures from the head injuries he received. The cause was the valve stems from China.
 
You guys are worrying me to death. I just had a tire mounted and I insisted on a 90 degree valvestem. And me about to take off on a 3500 mile trip.
Thanks a million
 
Honda has fitted 90-degree metal stems with a rubber base on certain models and on those models there is a lug on the rim that supports the stem against undue bending caused by centrifugal force. The metal stems I use have an O-ring seal and the horizontal portion of the stem is short so as to not create any bending forces at the mount. I bought them from No-Mar at an MSTA event but I believe they are really made by an outside company.
 
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Thanks for all the input. I'll do my best to remove the rear wheel today and see if I can get it to the shop before they close. Luckily, I still have another bike by which to commute, but don't want to be without the NT long as I really enjoy riding it. Just clicked to the odometer on my PC800 over 70K two days ago and am happy I still have it at the moment as the Yamaha FJ1200 continues to have a fuel leak issue. Ah, the wonders of multiple bike ownership.
 
Tattoo Paul said:
I think the minor inconvenience you sometimes incur trying to check your tire pressures, or adding air, is nothing next to a tire valve stem failure where you'd least want it.
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Especially when you consider that a Valve Stem Extension hose to make adjusting air pressure easier is only around $10....
 
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Or you can make your own almost for free.

Get one of the "give away" air press gauges. Cut off the barrel section. Get an old tire stem (metal such as on a tube) and use JBWeld to bond together. Not 90 deg but works great with the Slime compressor.
 
I had bought a set of 90 degree tire valve just before having new tires installed at my dealership. When I gave them to the tech, said he would check and see, but didn't think they might be safe on this bike.
When I picked up the bike, I didn't notice until I got home that they had not been installed, but were back in my side pocket. The tech didn't mention it, but apparently, he had a legit reason for not installing as I trust him with his motorcycle knowledge.
I guess he was doing me a favor not making the pressure checks easier.
I've had a different style of 90 degree valves on my Vmax and the same Tech installed the last tires with them ok.
 
Well, I got the wheel off - after removing the muffler and rear fender - but am concerned that the bearing grease I plan to use may not be equivalent to the Pro Honda Moly 60 Paste (molybdenum disulfide). I have NAPA multipurpose EP grease. "Particularly recommend for wheel bearings on most vehicles with disc brakes." The label says Lithum Complex NLGI #2 Consistency. I'm my stuff okay to use or do I have to wait until I can obtain some of the OEM grease?

dannyjo - I'm pretty sure I have a picture of my PC800 at the base of your avatar pic. I remember seeing the cross from miles away and couldn't resist the photo op during a cross-country ride several years ago.
 
Never mind on the issue of Moly grease. Found the other thread that seems to reiterate the desire to use the Honda Moly 60 paste. Just for reference though, am I putting it on the gear ring on the rear wheel or do I have to remove additional pieces from the wheel to get to the bearings? The installation guide indicates to "check that the wheel hub and final drive gear splines" be coasted with the stuff. I just want to be sure I'm using it correctly. Thanks.
 
Just put it on the splines (the 'gear' part). Do not disassemble any further or you'll have more of a mess to clean up :)

And yes on the molly grease. The splines do not move like gears and they need the really high pressure grease with moly suspended in it. Just spread it until all the grooves in the spline are filled up. Don't worry if you use more. Any excess will just make the wheel dirty :)
 
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