j mazz

i lost 2 magnets and had one lose it's magnetics. The computers are still good. i stopped at 2 bike shops and they had broken ones.

anybody have any tricks to keep them on or a replacement?

HillRider

Hmmm, I've never had a magnet come off of a wheel or the magnet itself come off of it's mount. I'm using Cat-Eye's screw fastened metal cased type on conventional wire spoked wheels. What kind are you using and what type of wheel are they installed on?

casjr2171

That hasn't happened to me yet, but I would probably try using a drop of loctite red on the threads to keep it from unscrewing/loosening.

j mazz

it was on for a long time, part of the problem is it never fit right - made for a round blade and i have flat blade now. went to lbs and he had a box of them and gave me the best one in the box but part of the tab that keeps it closed was broke, lost that one too. gorilla glue sounds like a good idea, i see them for sale on amazon. made for round and flat spoke.

FBinNY 

I've found that the best place to mount magnets is as near the hub as possible, and just inside a cross, where it can nestle and be well supported against movement.

fietsbob

I

Quote:

've found that the best place to mount magnets is as near the hub as possible,
and just inside a cross, where it can nestle and be well supported against movement.

Some that I had used a setscrew .. ,

yea + closer to the hub, the magnet is not flung out with as much force.

Bingo Blingo

If all else fails, you can tape, glue, dental floss, or zip ties as a fail-safe, secondary attachment. I bet any other speed magnet would work as a replacement. Nashbar is selling $3 Catseye magnets that are quite secure.

jtolive

I use black epoxy coated Neodymium magnets from Ebay. They are very strong magnets. I got the small 3x3mm size. Small drop of silicone has it just held fine (flat spokes.) Can't hardly see it. Probably a YMMV type thing between different computers or spokes.

j mazz

cool idea! i don't see the 3x3 in black on ebay? did you have to buy 25 of them?
what is YMMV?

HillRider

Yep, good advice. Snug the magnet up against a spoke cross and it's supported on two sides and can't rotate out of alignment. That's not much use on radial spoked wheels but there are magnets designed for bladed spokes.

AlaskaStinson

I used a small neodynium magnet but placed it inside the rear tire. I used a small tire patch to hold it on the tire and to stop chaffing. It is sandwiched between the tire and the inner tube. I put the pick up on the bottom of the chainstay. No visable magnet or pick up. It's worked great for years both on my road and mountain bike. A bonus is my computer works when I put the bike on the trainer inside since it's on the rear tire. (geek alert) I put one on the front tire at the same time for a while just for fun, both tires at the same pressure. The front tire travels about 3% farther than the rear due to steering.

Chris_W

And also because your body weight compresses the rear tire more, making it's diameter smaller, which you should compensate for by programming a smaller wheel circumference. However, I'm surprised that the difference is as much as 3%.

Bezalel

If your rear wheel compresses more than your front wheel, you either have too much pressure in the front or too little pressure in the rear.

jtolive

Got 10 for around $6. Real small - they look like microdots.

YMMV = "Your mileage may vary". May not work with all computers/wheels. Mine were a Shimano Flight Deck computer with DA 9000 C24 wheels.

rpenmanparker 

I have been completely successful locating magnets at far end of spoke near the rim. See the cheap-as-dirt computer listed here: https://www.ebay.com/itm/Waterproof-B...item460ff9c0f3

You can afford to buy that just to get the magnet, but I have been using these simple computers for decades. Wireless, cheap as dirt, computer lasts forever. Cheap enough to buy extras just to get the mounting parts for my additional bicycles. Over the years I've paid between $5 and 10 for several of them. So after buying four or five of them over the years to get the extra mounting parts, I am just now only on my second computer. I still have some tucked away for the future. Anyway the various magnet designs they have offered over time have all been completely secure on round or flat spokes out near the nipple. Never lost one.

This computer model has evolved over the years, but is still more-or-less the same as always and has been offered under many brand names like dBase, Ascent, etc.

HillRider

Cat-Eye used to sell the "Astrale" a wired computer with a rear wheel pickup for speed/distance and a cadence pickup so it would work fine on a trainer. The pickups were fastened to the nds chainstay and the magnets mounted on a rear wheel spoke and non-drive side crank arm. I have had one on my trainer bike for several years. The Astrale is discontinued but Cat-Eye still shows the "Strada Cadence" on their web site that seems to be a newer version of the same thing.

I wonder if wireless computer heads will pick up the signal from a rear mounted magnet and pickup. Any body tried it?

Yes, I've noted the rear wheel pickup gives a slightly shorter distance reading than a front pickup but the deviation is about 0.5% by my measurements, certainly not 3%.

rpenmanparker 

I did try it once with the cheapie type computers I described above, and it was a flop. Could not get the signal from the rear chain stay to the handlebars. Bummer.

HillRider

Before I got the Astrale, I once mounted a standard wired computer crosswise on the top tube near the seat tube of an old dedicated trainer bike. That let the shorter connecting wire reach the chainstay where I mounted the pick up and magnet. It was awkward to read while "riding" but it did record the "distance", time and "average speed." The Astrale mounts normally on the handlebars and I can use the same bike both on the trainer and on the roads.

Wilfred Laurier

i think there is one type of magnet or another
on every adult size front wheel in my posession

some have literally been in place for decades
several of them have done thousnds of kms
over rough dirts roads and offroad trails

most of them are the single set screw type
but the oldest is the cateye two spoke clamp type

the only thing i can think of that might make magnets more
or less
likely to stay on is
shaped or bladed or aero spokes
as all my spokes are round

niuoka

agree with this one,

don't agree on the post suggesting red Loctite
at least in automotive and motorcycle work. Red is for bolts 1/2 inch and bigger, blue for smaller
on a car, if red does its job , it takes over 200 ft pounds of torque to break loose

so if your gonna go buy Loctite, you want blue
there have been threads about the pros and cons of Loctite on a bike, for me it is dependent on the application.
the only place I have used it on my bike is on the screws that hold the RD pulleys, a tail light mount that was too short for a lock washer, and one of the screws for my bell that kept coming loose

Flying Merkel

Silicone sealer. Stick that little f***er on.

bikeman715

HillRider , With most wireless computer the range for the transmitter is about 3-4 ft . That the reason they are mounted on the fork .

FBinNY 

You're riding his post backward. Tire compression would make a rear wheel mounted unit read high, not low. (wheel turns more often over the same distance).

The reason the front wheel computer reads higher is because the front wheel actually travels farther than the rear. The rear wheel takes a smaller radius on all turns, and if one is poor at riding straight lines, the rear travels almost straight with the front tracking a sine wave back and forth across the central line.

3% seems high, but it depends on bike handling skill, and course. I bet you could get a difference much larger doing small radius donuts in a parking lot.

AlaskaStinson

Clarification: 3% was the maximum difference on my mountain bike on single track with minimal skidding. When I tried it on my road bike, and concentrated on keeping as straight as possible, the difference was still there, but less than one tenth of 1%. Normal riding on the road was just below 1%. Tire pressure and weight distrubution was compensated for. It was a science project for my class 5th grade class.

CACycling

I've got the wired version of the Strada with Cadence on my road bike and it is great. Single wire runs to the back but there are separate pickups for wheel magnet and crank magnet. The Strada wireless has a single unit that mounts on the chain stay with both pickups in it. Haven't tried it but the reviews are positive. Probably go that way if the current one ever dies.