flat tire

I just placed my computer magnet in the middle of the spoke. I have had it at the end of the spoke in the past. It is pretty bulky and large and my biggest concern is if the spoke is at any increased risk of breaking (such as when you hit bumps at speed and get some rim flex)? I wouldn't think it would, but just wondering.

sailor

I couldnt see it being any problem at all. The thing is only touching the spoke at that tiny area, not like its gonna prevent the spoke from flexing right or anything...

55/Rad

Performance wise, it doesn't matter where you put it - though people have their opinions as to closer to hub or rim. I prefer closer to the hub for the simple reason that, since the magnet travels slower and less distance, it's a little less likely to come loose and fall off.

55/Rad

SSP

If you have a wireless unit, it's better to mount it high up on the fork (so the magnet will be located nearer to your tire). This shortens the distance between the transmitter and the receiver unit, which helps to avoid problems with interference with wireless cycle computers.

Whoodie

55/Rad said it all.

flat tire

That is my thinking as well. It would also have more time to across the transmitter since it is moving slower.

WorldWind

Thats a joke right?

leftnotracks

No, it's absolutely true. Also:

• The closer to the hub, the less energy required to complete a revolution.
• Further from the tire reduces the amount of road grim on the sensor.

-CM-

Placing the magnet (and therefore the sensor) closer to the hub has the advantage of removing the urge to perform the potential bonehead action of trying to adjust the sensor while you're riding.

(Those who have attempted this action understand the humor of this post.)

venga venga

I had to scratch my head and think about this for a bit.....in order to accurately reflect your speed, the computer calculates the frequency of the magnet passing the sensor. One revolution of your wheel = one "pass" across the sensor, no matter where the magnet is placed on your spoke....but, the closer to the hub the magnet is placed, the shorter distance it travels during each revolution of your wheel; therefore it is moving more slowly than if it were placed closer to the rim (where it would travel further during each revolution).....do i have this right?

WorldWind

Thank you

caloso

I mounted mine closer to the rim simply because the sensor fit better high on the fork. YMMV, but I haven't had any problems.

flat tire

Correct. Circumference is 2("pie")r where "pie" is something like 3.141 and r is radius. The radius is much shorter if the magnet is near the hub rather than the rim. Therefore it will travel a shorter distance (measured as circumference) in the same amount of time. Speed is distance/time. Since the distance the magnet travels is decreased, then so is the speed of the magnet. The sensor should be able to pick the magnet up better (when closer to the hub) since it may take twice as long for the magnet to pass the sensor.

LOL about the bonehead sensor adjustment comment. Been there and chickened out several times. Always pictured myself getting a finger stuck and tumbling over the handlebars.

venga venga

Thanks for the validation.....kick-started a few brain cells that had been dormant since college.....made my brain itch.

also can relate to the sensor adjustment comment...just like trying to disconnect a spark plug while the engine's still turning......

Guest

As close to the sensor as possible. I had problems when my LBS mounted the magnet too far away from the sensor. What a crappola tour that was when I couldn't figure out why my cyclocomputer wouldn't give me any readouts until the last week.

Koffee

NeoBinary

Wouldn't the readings be based on the magnet being a certain distance from the center of the circle (hub)? Deviating from the distance by which the calculation were made during programming would affect accuracy I would think.

caloso

No. It doesn't matter. All the computer does is count how many times the wheel goes around. Whether you mount next to the rim or right next to the hub, it still goes around once.

WorldWind

Throw away your spoke mounted pos and put a thin powerful magnet between your tube and tire. Then mount the sensor appropriately.

Using optical mouse technology a sensor that read the tire brand would be nice.

A GPS driven device that was imbedded in your helmet and had its display in a small rear view mirror. One mileage computer that worked for all your bikes, that would be nice.

pgreene

well Lance mounts it near the rim, as do all the posties. therefore i, too, shall mount it near the rim.



(ducking)

daratbastid

The instruction book tells you exactly where it needs to be mounted, and the location may be different from company to company or even model to model. It is not a preference issue here. One thing for sure if its mounted in the wrong place for your specific model, you will get incorrect data

leftnotracks

Untrue. All a sensor does is send a signal to your computer, telling it "One rev....One rev...One rev...". Your computer times those with it's built in clock and mutiplies by Circumference/revolution. No matter where you mound the magnet, so long as the sensor detects each revolution, your data will be consistently accurate, or inaccurate, depending on what circumference your computer things you have.

ManBearPig

Specifically on a Polar brand unit, for use with bladed spokes, do y'all use the magent type (A) rotate + metal cover, or (b) screw? The screw type looks big and bulky, and I'm leary of it being so far from the hub as installed at the shop, but sounds like you guys are saying that's typical setup, eh?

55/Rad

I'm sure Lance would tell you that the magnet needs to be mounted in that location in order to correctly balance the wheel to his personal specs. Probably to offset the weight of the tube valve.

No lie.

55/Rad

DigitalRJH

I too went back and forth on this issue. I mount the magnet close to the rim, only reason, every pro in the peleton I see has it mounted high on the fork, and the magnet close to the rim. Those guys hit speeds I'll never reach, so if there was "wheel balance" issues I'm sure they'd notice it and would mount it further down the wheel.

tanguy frame

Second that. Lance's wheels are perfectly balanced with valve stem, and spoke magnet. Rim manufacturers put a small weight in the rim opposite the valve to balance the wheel, but on Lance's rims, the weights are precicely calibrated to his exact valve and spoke magnet. He probably shaves a gram or 2 from the valve balance weight to compensate for the magnet.