Speedometer hack for low speed resolution

[jeremy11]

I run Cateye Velo 5 and 7 speedometers, and both suffer the same frustrating flaw.  They don't register below about 2.7 mph. That's fine for most riding, but for bikepacking in the Colorado mountains, when you sometimes have to push, carry, or ride very slowly for hours on end, its a mental drain to be working your tail off and see 0 mph on there and no mileage increase.

I think the issue stems from the time between magnetic impulses into the speedometer, and if the time interval is too great it forgets about the previous impulse.

Speedometers work off a simple principle, speed = circumference / (time between impulses) and distance = sum of circumferences traveled

Now, if we add a second magnet (180 degrees from the first is best) and half the circumference input to the speedometer, the speed and distance readings are the same!

Simple, effective. Initial tests registered speeds as low as 1.2 mph, at which point I couldn't ride much slower without doing a track stand. It also appeared to be registering properly for speeds up to about 18 mph.

Now I need to find some awful hike a bike mission to test it on more thoroughly.

[RonK]

I run Cateye Velo 5 and 7 speedometers, and both suffer the same frustrating flaw.  They don't register below about 2.7 mph. That's fine for most riding, but for bikepacking in the Colorado mountains, when you sometimes have to push, carry, or ride very slowly for hours on end, its a mental drain to be working your tail off and see 0 mph on there and no mileage increase.

I think the issue stems from the time between magnetic impulses into the speedometer, and if the time interval is too great it forgets about the previous impulse.

Speedometers work off a simple principle, speed = circumference / (time between impulses) and distance = sum of circumferences traveled

Now, if we add a second magnet (180 degrees from the first is best) and half the circumference input to the speedometer, the speed and distance readings are the same!

Simple, effective. Initial tests registered speeds as low as 1.2 mph, at which point I couldn't ride much slower without doing a track stand. It also appeared to be registering properly for speeds up to about 18 mph.

Now I need to find some awful hike a bike mission to test it on more thoroughly.

And when you carry? No speed/distance will be registered.

This is where a GPS becomes worthwhile.

[jeremy11]

Of course nothing registers when the wheel isn't spinning. But I'm somewhat anti-tech (and cheap) so don't feel like going GPS, but do understand its benefits.

[AZTtripper]

You can't be any cheaper then me. Screw the speedo and get with gps.

Seems like many bikepacking routes require it. Good luck even staying on course on parts of the AZT, the Coco 250 uses so many different trails, thru Sedona ect..., a gps is the best if not the only way to roll.

Do you have a smart phone or is that too much as well? The apps are not that great in terms of staying on course at race pace, but for recording where you just were, they do work.

[KittyOnMyFoot]

That's actually pretty clever, but then if you get up to some high speed, you might be throwing impulses faster than the unit can handle? I guess it depends on the unit, and if it's actually an issue, you can just pick the lesser of the two evils.

[AugustWest]

I can appreciate being anti tech - but that speedo setup seems pretty techy to me.  A used smart phone off of ebay and a couple of cheap apps and you're set with amazing route finding abilities.  Between Ride With GPS and Gaia GPS apps I have routes all over the world at my disposal and you don't even need cell service. 

[dave]

Nice idea!  The speedometer turning off was always super demoralizing on the CT.