Garmin/Sigma magnet woes ?

kubatyszko

Speeding Up
Jul 29, 2012
79
24
38
Shinagawa, Tokyo
#1
Hi,

I have: Sigma STS 1609 ( 3 years ) and Garmin Edge 500 (new toy - just over a week),

I have installed the Garmin + Speed/Cadence sensor, but I just can't say goodbye to Sigma, so what I did - was to move the Sigma's speed sensor to the chainstay next to Garmin and tried to use the same magnet - and:

Garmin's magnet doesn't trigger sigma unless it's almost touching it

Sigma's magnet does trigger Garmin but the speed reading is intermittent (losing about 30-40% of the reading - when imported to Strava, 70km route became 40km, and 17km became 12km) - I noticed that late because for the whole day I had Course map on and didn't even look at speed readings.

Do you guys have any experiences with various magnets ? - I want to keep the Sigma (at least for some indefinite time), and ideally use single spoke magnet for both (not that's it's so important but you know - two magnets will mess up the centrifugal force of my wheel :D:D )

(I still have Sigma cadence magnet - and this one works fine with Garmin).

Cheers
 

FarEast

Maximum Pace
May 25, 2009
5,528
538
193
Yokohama
#3
Ok - siimple solution to this is scrap both magnets and go get some rare earth magnets. These are incredibly small yet a lot more powerful.

I use them on all my wheels and basically glue them to the spoke and crank arms for thee cadence sensor - you can get them in small flat strips or standard round/square types but you will require a very strong bond to keep them on!
 
Sep 2, 2009
5
0
0
#5
Ok - siimple solution to this is scrap both magnets and go get some rare earth magnets. These are incredibly small yet a lot more powerful.

I use them on all my wheels and basically glue them to the spoke and crank arms for thee cadence sensor - you can get them in small flat strips or standard round/square types but you will require a very strong bond to keep them on!
That is genius.
 

theBlob

Bokeh master
Sep 28, 2011
2,863
1,450
129
...
#6
I tried the rare earth magnets from Tokyo Hands, At first I thought a little one would be enough.... no. Basically the size I needed to buy made the whole process more expensive than if I'd just bought the one designed for garmin. Which is what I did in the end.

IMHO the cheapest and easiest solution unless you can be sure of the exact magnet you need to make it work.
 

FarEast

Maximum Pace
May 25, 2009
5,528
538
193
Yokohama
#7
It depends on the wheels - all my race wheels have blade/aero spokes so I use the then strips as they are obviously more aerodynamic (marginal gains and all) and more secure (larger contact area).

On my training wheels I used the round type and either used the original Garmin magnet holder or the Shimano one.

Also if you are using Steel spindles on your pedals then don't bother attaching the magnet to the crank arms - get one that will happily sit over the hex bolt insert on the pedal spindle - magnetic force will keep it happily in place regardless of terrain or speed then just pry off if you need to remove the pedals.
 

bird

Speeding Up
Nov 30, 2010
322
18
38
Kawasaki
#8
rare earth magnets
+1 for rare earth magnets. (neodymium being most popular)

I use epoxy adhesive to glue it on bladed stainless spoke. You can build up epoxy around the magnet/spoke as necessary if you want to make it more aero:)
I think it would be wise to choose an adhesive that resists against impacts/shocks and preferably allow some elasticity. Most general purpose instant adhesives ("Aron Alpha", "Super Glue"...) are not good at this.
 

GSAstuto

Maximum Pace
Oct 11, 2009
945
242
103
tokyo
www.roadfixie.com
#9
+1 for the neodymium magnets - you can get them in handy 12mm round as well. Just pop into the end of your crank arm at the pedal (unless of course you have Ti axles - then a little doubleback tape works). On the spoke side I'm using the Mavic ones. They fit all our Sapim and Pillar Aero spokes perfectly, as well the Mavic ones (of course). Another option is to do as FE says - and if you have deep dish wheels, you could even epoxy the small magnet directly on the rim. I've even thought of adding a small magnet recess on our next batch of rims just for this purpose.
 

FarEast

Maximum Pace
May 25, 2009
5,528
538
193
Yokohama
#10
Tim - Funny you should mention that as I actually bonded a magnet into one of the drainage holes on my Mavic Carbone wheels. All well and good until you drop it inside the rim - fortunately easy to get out once you worrk out that its a magnet - took me 5 minutes of shaking and twisting before I worked that one out :D
 

kubatyszko

Speeding Up
Jul 29, 2012
79
24
38
Shinagawa, Tokyo
#11
If you're so worried about having two magnets on one wheel, why not move one to the front wheel?

Not that I thought your worries made sense! :p
They don't :p

Ok - siimple solution to this is scrap both magnets and go get some rare earth magnets. These are incredibly small yet a lot more powerful.

I use them on all my wheels and basically glue them to the spoke and crank arms for thee cadence sensor - you can get them in small flat strips or standard round/square types but you will require a very strong bond to keep them on!
This is a great idea, what I would recommend (other than taping) instead of gluing - to use SUGRU - it's an air-cured rubber-like compound, you can attach things to other things and it holds really well - after curing for 24 hours it becomes like a hard rubber - possible to remove with a bit of knife, so it's not as permanent as glue - and let's not forget that glue penetrates the surface, so who really knows what is it's impact on the spoke...
SUGRU is mostly used by "hackers" for quick repairs, available in some electronic stores (but I got mine in the U.S.)

Now I just need to source some magnets.
 

FarEast

Maximum Pace
May 25, 2009
5,528
538
193
Yokohama
#12
I would suggest any hardware store that isn't Tokyu Hands - extremely expensive compared to Homes, Folea and other big hardware stores.
 

Yamabushi

Maximum Pace
Jun 1, 2010
2,335
188
1,083
Tokyo (Nezu)
fudoushin.com
#14
The nearest DIY for me is not far from Tokyo Dome. They have neodymium magnets in an assortment of sizes. The 12mm x 3mm round one fit my 7900 pedal spindle near perfectly. I was even able to get one with a small hole in the center so it's easy to remove when it's time for maintenance.