Cateye Micro Wireless

[JimK]

My new CatEye Micro Wireless CC-MC100W Bicycling Computer arrived in the mail today - just as I was headed out for a ride! So I had to delay the ride a bit while I hooked up the gadget.


My first time with any kind of device like this. I have Schwalbe Marathon Supreme 26" x 2" tires, i.e. 50-559 size. The Cateye chart says 2050 ought to be the circumference. But I tried rolling out the circumference and got more like 2008. That seems like a large discrepency! Of course, inflation, load, etc. are all factors. But I wonder what experiences others have had in this domain.

Thanks!
Jim

[JimK]

Even worse, Schwalbe says
http://www.schwalbe.co.uk/shopdata/files/TechInfo2-GB.pdf
the diameter is 2075. Must be all the useless junk I have in my handlebar bag, compressing the tire!

[julk]

Jim,
My previous bike had 26" Rhyno rims and Schwalbe XR 26x2" tyres.
Looking at my old computer it has 2005 as the circumference and worked from the front wheel.

I run the front tyre at 3 atmospheres and the rear at 4 atmospheres for my preferred comfort level.

My new bike has 26" Rigida Andra CSS rims and Schwalbe Hurricane 26x2" tyres.
Looking at my new computer it has 2044 (which surprises me as I remember it as 2005 as well) and works from the rear wheel.
I will run the rear wheel measurement again tomorrow in daylight and check what it really is.

I found the computer you have to give me unreliable results in cold & wet weather, losing around 10% of the journey. I hope yours works ok.
I moved to a cateye V3 and have had no problems with it yet, but I haven't run it for long in the cold and wet yet...
Julian.

[JimK]

I run the front tyre at 3 atmospheres

Thanks, Julian. I think I have the front at about 3.5 atmospheres. The discrepancy that has my attention is about 2%, i.e. about a quarter inch of radius. Between the thickness of tread and whatever bit of pneumatic compression, probably that isn't too much variation. Not all 50-559 tires are the same!

More than the useless stuff in my handlebar bag, I should probably look at that spare tire I carry around my waist!

Jim

[julk]

Jim,
I just tried measuring the circumference again.
I pumped the rear tyre to 4 atmospheres - checked on 2 gauges.
I rolled 4 wheel lengths sat on the bike - I weigh around 76 Kgs.
Repeated 3 times the distance rolled averaged 8.144 mtrs giving a circumference of 2036mm for me.

I will correct my computer, but am not worrying too much about it - the discrepancy is only around 4 miles in a thousand.
Julian.

[JimK]

My other fun recent toy is an altimeter, a High Gear Axis Wrist Computer. I decided not to get an altimeter integrated into my bike computer because a separate unit gives me some extra flexibility... though probably a bit less function.

What I am using mostly right now is the accumulated climbing function. It's a nice way to measure my ride: distance and accumulated climbing.

The changing barometric pressure throws off the accuracy, of course. I set the altitude to 600 feet as I am leaving. Today when I got back home the device read 530. My accumulated climbing read 390. So I figured I can add 70 back in to get a total of 460. Similarly, when the altitude reading on return is higher, I should subtract the increase from the accumulated climb to get a more accurate measurement. Sound right?

An experiment I haven't done yet, but have been thinking about. Suppose I ride from point A to point B, versus riding B to A. Suppose B is lower than A. Then the B to A accumulated climb will be greater than the A to B accumulated climb, by just the altitude difference between A and B.

Do others find these devices useful?
 

[julk]

Jim,
I don't have an altimeter, but it sounds like fun.

I reckon you have the adjustment right for the changing barometric pressure, but only if you are climbing/descending for all of the journey.

If say only part of the ride time the trip was hilly then the change in barometric pressure over the flat part of the trip should not be included in the overall adjustment.

e.g. assuming a steady change in barometric pressure and a 2/3 time hilly ride then only 2/3 the change should be used for the adjustment.

Does this make sense?
Julian.

[JimK]

I think my formula is just plain wrong.

Suppose I have a completely level ride. If the atmospheric pressure changes so my altimeter reading decreases, I will show no accumulated climbing at all. So I shouldn't correct the reading at all. If the altimeter reading steadily increases, then the device will show that I have accumulated some climbing, and indeed I should subtract off the gain to get the correct figure.

Suppose my ride is a long gradual decline, and then a short steep climb back to my starting point. Suppose the pressure is changing steadily, so a fixed altimeter would show an increasing elevation. My short steep climb is quick enough that the pressure doesn't change much, so the accumulated climb measured for that part of my ride would be accurate. But look at the measurement for my long slow decline. If the pressure is changing fast enough, that will actually look to the device like a climb, and a correction should be applied. If, on the other hand, the pressure change is slower, then it will look to the device like downhill movement and no climbing will be accumulated - thus, no correction should be applied.

Math is cruel!

[Andre Jute]

I think my formula is just plain wrong.
[...]
Math is cruel!

Nah, it's logic that is cruel. Math is merely precise.

I had a Ciclosport HAC4, bottom pic at http://coolmainpress.com/BICYCLINGgazelletoulouse.html It records the ride for playing back on the computer later. Because so few roads are not dangerous here, most days I take the same ride. After considerable effort measuring on maps and time wasted writing algorithms, I came to the same conclusion as Jim, that over time and distance elevation error evens out, in my case over a few months to within 0.0something per cent, well within measuring error on maps.

I did one day at the highest spot of my ride have a low reading of 23%, which brassed me off for underrating my effort, but by the time I reached home it read over for the day by about 3%.

After the expensive (300+ Euro) Ciclosport broke on the day after its guarantee ran out, I went to separate heart rate monitor/bike computer/altimeter but I don't carry the altimeter any more -- I know all the elevations off by heart, and I'm not subject to atmospheric pressure variations!

Andre Jute

[JimK]

I live in a tourist town. The local bike shop rents bikes, and lots of people bring bikes on their cars. There is a lot of beautiful riding around here, but also a lot of treacherous riding. The roads most people know, the roads they drive their cars on, are treacherous. Even the locals don't know the back roads very well, much less the tourists. One of my projects is to make a map of local bike routes, the back roads.

Since we are in the mountains - the local terrain varies from about 200 to 2000 feet in elevation - the amount of climbing is a key piece of information for any route. Some people come here just for the big hills. Most folks, I expect, would prefer something less rigorous. There are hills pretty much any way you go, but at least with a map folks can reassure themselves that, however much they're sweating, the alternatives are even worse!

Yeah, I think if I ride the routes enough times, the noise from pressure changes will average out pretty quickly. I hope to be exploring fresh territory for quite a while, but at least I will know the altitudes along the nearby roads soon enough.
http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=12498&sll=37.0625,-95.677068&sspn=33.984987,46.318359&ie=UTF8&hq=&hnear=Woodstock,+New+York+12498&ll=42.068665,-74.236679&spn=0.248746,0.623474&t=p&z=11

[Relayer]

Jim

This year I got a Garmin Edge 800, which is a sort of cycling computer but also a sat nav.  This is an expensive gadget, but personally I don't mind if it enhances my enjoymeny of getting out on the bike.

Anyway, because it uses satellites there are no issues with wheel circumference.  It also has an altimeter and can be customised to display a variety of data e.g. elevation, total ascent, total descent.  When you get home you can upload your ride data to your Garmin website which then gives a map and various data and charts, example of one from your area here:-

http://connect.garmin.com/activity/88286605

The website also gives you the option of 'elevation corrections' which adjusts your data against terrain data related to the maps.

[JimK]

example of one from your area here:-

I wonder if I saw the fellows out on that very ride. Just about that date, I saw a group of serious looking riders coming out onto Route 209 from an entrance ramp. That is not a common sight. But that's what's on the map you posted. They started from Bike Brothers bike shop in Kingston. They rode up Sawkill Road - I would never recommend that! Too twisty and busy! I have a different route to get to Woodstock from their starting point.

Yeah, I've been drooling over that Garmin device. Maybe in a couple years if I can really ride enough to justify it.

Ha, here is part of my crazy logic. A lot of how I justified buying a Thorn Nomad is my rather doomerish outlook. Collapsing economies, peak oil, global warming, all that. Dmitri Orlov recommends bicycles along with sailboats etc.:

http://cluborlov.blogspot.com/

An interesting question: how long will the GPS system last?

I am trying to use my bike as practical transportation, more and more. It's a vision, at least!