90 degree tyre valve stems

[garryc]

Any suggestions/comments about the use of 90 degree tyre valve stems.
Are they any use, worthwhile?
What size would i need to buy
thanks
garryc

[Howie]

They make access easier with modern large brake rotors, OEM on the front on your modern Ducati.

[carbmon]

Not the cheapest but good quality and tech support here at KurveyGirl - they get the size right for your bike, call 'em if in doubt.  No affiliation other than satisfied customer.

Just noticed your location so you're not likely to order from the US ... well, anyway, the KG site has size info for you.

[Bill in OKC]

I read another thread the other day about someone losing air pressure at high speed.  The solutions were to 1. use a metal stem cap with a rubber seal and 2. buy angled valve stems (also with a good cap).  The angled stems do make access easier but also add a safety factor if you are going high speeds - at track days of course.

[He Man]

how does an angled valve stem help with air leaking out?

[Slide Panda]

but also add a safety factor if you are going high speeds - at track days of course.

How's that?

[RBX QB]

Angled stems should be standard on bikes. My Duc has them. My Kawi doesn't. To make matters worse, the rotors on the front of the Kawi make it so I can't get a wand-style (rigid) inflator on them. Have replacements, but waiting until the tires go to minimize mount/balance costs.

I'm an advocate for putting 90s on your bike. The other half of that thought being to make sure they are pointing uphill when the bike is on sidestand. Obvious to some, but others may need that said out loud.

[battlecry]

"how does an angled valve stem help with air leaking out?"

Never had it happen to me, but the thinking is that the valve spring force can be overcome by the mass of the valve widget times the radial acceleration due to the tire's rotation.  The straight stems can leak at high speeds.  The angled ones are not susceptible to this. 

[carbmon]

"how does an angled valve stem help with air leaking out?"

Never had it happen to me, but the thinking is that the valve spring force can be overcome by the mass of the valve widget times the radial acceleration due to the tire's rotation.  The straight stems can leak at high speeds.  The angled ones are not susceptible to this. 

30 years in the racing paddock and I'd never heard that one 

But they sure are nice for access around big rotors, mufflers, luggage, etc

[Speeddog]

All the Duc wheels I've seen use the 8mm size.

IMO, riding around with no valve caps is like riding barefoot.

[Bill in OKC]

how does an angled valve stem help with air leaking out?

A straight valve stem with a plastic or no cap at all will open up at high speed and the tire goes flat quickly.  If you have metal caps with a good seal - no problem.  The angled stem will force the valve sideways instead of down so it is not relying on the cap so much to keep the air in.  At street legal speeds it is not a problem.

[He Man]

makes sense, but i never thought the valve spring would open so easily under centriptal force

[sgollapalle]

90s will definitely help when filling air.. Had situations where the end of the filler was a straight 8" metal pipe..

You'd have to reach some 'serious' speed to get the mass of valve widget times radial acceleration to get over 32 psi (or 2.1 bar or what ever that translates to) or your valve widget weighs a pound 

The other half of that thought being to make sure they are pointing uphill when the bike is on sidestand. Obvious to some, but others may need that said out loud

looks like I'm missing something here... whats the rationale?

[Bill in OKC]

I think most tech inspections will fail you if you do not have good caps - it is in the AMA rules.  I have a car that had bad rubber stems one time - too much carbon in the rubber or something.  They exit the wheels at about 45 degrees.  The force at speed bent them outwards until they cracked at the base and air would escape.  When sitting still you could air the tires up and they would hold air.  It was crazy for a bit.  I replaced the rubber stems with metal motorcycle stems.

[BastrdHK]

looks like I'm missing something here... whats the rationale?

Stems should be on right side of the wheel, so that when the bike is on the sidestand the angled valves point at more of a 120* angle aiding access filling, where if they were on the left side of the wheel, they would point down towards the ground when the bike is on the sidestand.