computer distance error

R@nsh! ran@~qfish.com said:

Hi. Could someone please point me to resources about popular bike computers distance
measurement error?

That seems hard to generalize ... tire pressure, riding surface, riding style ... if you are
measuring how fast the front tire is going around that will all affect the outcome.

FWIW, I use a GPS now. That's going to average things out, and give me the speed between sattelite
fixes, but that appeals to me. I can see my speed between map points (and elevations), and compare
Monday's loop to Thursday's loop. (Downloading to the computer now and then.)

I'm kind of shocked that Garmin sells a handlebar mount for the eTrex ... but other than the GPS
turning itself off on minor fall-downs (not really crashes), it's held up pretty well. Knock wood.

higb says:

Quoted message said:

I'm kind of shocked that Garmin sells a handlebar mount for the eTrex

Shocked? Surprised (and pleased), maybe.. ;-)

Quoted message said:

... but other than the GPS turning itself off on minor fall-downs (not really crashes), it's held
up pretty well.

Try not to fall down . My eTrex has put up with all kinds of cr*p, and still keeps going.

Steve

Stephen Baker said:

higb says:

Quoted message said:

I'm kind of shocked that Garmin sells a handlebar mount for the eTrex

Shocked? Surprised (and pleased), maybe.. ;-)

Quoted message said:

... but other than the GPS turning itself off on minor fall-downs (not really crashes), it's held
up pretty well.

Try not to fall down . My eTrex has put up with all kinds of cr*p, and still keeps going.

Steve

Had a 12-map for quite a while. Garmin's handlebar mount's not strong enough for a mountain bike
though -- After the 4th time that it went flying, it finally split at the seams (I had already
replace the lens with one that I carefully crafted out of lexan) -- still works, but I don't trust
it's ruggedness or waterproofness any more 🙂. Made my own mount and replaced it with a 76s (map,
altimeter and compass) -- sweet
🙂. Nice for mapping trails, not getting lost on new trails, long
distance wandering on the roads in areas that I've never been, seeing where I've been and keeping a
log of miles traveled. AND, it's accurate 🙂.

David

Stephen Baker said:

higb says:

Quoted message said:

I'm kind of shocked that Garmin sells a handlebar mount for the eTrex

Shocked? Surprised (and pleased), maybe.. ;-)

Quoted message said:

... but other than the GPS turning itself off on minor fall-downs (not really crashes), it's held
up pretty well.

Try not to fall down . My eTrex has put up with all kinds of cr*p, and still keeps going.

Steve

Forgot...

The battery turn-off on crashes (and any hard hits) are from the batteries momentarily losing
contact. Try pulling the springs a little longer or carefully bending the contacts out a little. If
you use rechargable batteries (like I do), make sure that the batteries terminals are clean. When a
set starts doing that, I rub the ends on a piece of wood -- acts like a fine emory.

David

"R@nsh!" <ran@~Qfish.com> wrote in message "]news:[email hidden]...

Quoted message said:

Hi. Could someone please point me to resources about popular bike computers distance
measurement error?

I imagine that a lot of 'error' if variation due to riding style, i.e. different riders will pick
different lines. The same rider will probably pick different lines on different bikes. While I can
imagine a group of roadies finishing a ride with identical distance measurements I wouldn't be
surprised if MTBer's distances varied by a couple of 'points'.

"higb" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

R@nsh! <ran@~qfish.com> wrote:

Quoted message said:

I'm kind of shocked that Garmin sells a handlebar mount for the eTrex ... but other than the GPS
turning itself off on minor fall-downs (not really crashes), it's held up pretty well. Knock wood.

I used the mount for a while (until I lost the little screw that holds the bracket to the back of
the GPS). On really rough stuff I probably would trust a jersey pocket more. I once heard from a
rider who used an external antenna mounted to his helmet.

R@nsh! said...

Quoted message said:

Hi. Could someone please point me to resources about popular bike computers distance
measurement error?

TnX

There is no error with my computer, because I program the tire roll-out.

higb said:

I'm kind of shocked that Garmin sells a handlebar mount for the eTrex ... but other than the GPS
turning itself off on minor fall-downs (not really crashes), it's held up pretty well. Knock wood.

Put a _thin_ slice of foam rubber inside the battery compartment, or wrap the batteries in tape, and
your gps will not longer shut itself off.

My foam is about 3/8" long by 1/4" wide by 1/16" thick. A strip of road bike handlebar cork of the
same dimensions would also work well.

Barry

(Stephen Baker) said:

Dave Kunz says:

Quoted message said:

Garmin's handlebar mount's not strong enough for a mountain bike though

Do tell? Mine has been on the bike for 2 years now, no breakage or battery turn-off. I admit i
don't mount the GPS on every ride (shuddup, Shaun....), but the mount survives - and this is with a
rigid fork, as I'm sure I've mentioned before. ;-)

Steve

Same here, and mine's sometimes even mounted to a road bike, the ultimate harsh ride.

The Garmin mounts that I've seen break were tightened gorrilla tight on the bars. I've seen some so
over tightened that they're cracked near the screw. The mount only needs to be tight enough for the
GPS to not move under normal riding, but loose enough to move in a crash. For extra insurance, I
wrap the hand lanyard around the bars and clip it to itself with a mini 'biner.

My eTrex Vista has survived several mountain bike crashes, and a *wild* 35 mph road bike vs. sandy,
wet railroad tracks melee.

The road bike wreck destroyed a shifter lever, a helmet, a handlebar, a fork, a pair of shorts, and
parts of me, but not the GPS.

Barry

Super Slinky said:

R@nsh! said...

Quoted message said:

Hi. Could someone please point me to resources about popular bike computers distance
measurement error?

TnX

There is no error with my computer, because I program the tire roll-out.

Bzzzt. Wrong! <G>

All bike computers have some sort of error tolerance. For example, the published error for a Shimano
Flight Deck is +/- 1% for speed, 30ppm for the clock, 50ppm for the stopwatch and ride time, and
.05% for trip and overall distance. This info is located in the manual.

Other units probably have similar tolerances, except they might not be published.

Barry

Stephen Baker <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Dave Kunz says:

Quoted message said:

Garmin's handlebar mount's not strong enough for a mountain bike though

Do tell? Mine has been on the bike for 2 years now, no breakage or

battery

Quoted message said:

turn-off. I admit i don't mount the GPS on every ride (shuddup,

Shaun....),

Uhhhmm, what? ',;~}~

Quoted message said:

but the mount survives - and this is with a rigid fork, as I'm sure I've mentioned before. ;-)

I'm rigid again for my commutes (details soon) ',;~}~

Shaun aRe

Stephen Baker <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Shaun says:

Quoted message said:

I'm rigid again for my commutes (details soon) ',;~}~

What, Kath got a job at Newtronics? ;-)

Heheheheheh - I freaking wish! ',;~}~

Shaun aRe

B a r r y B u r k e J r . said:

(Stephen Baker) said:

Dave Kunz says:

Quoted message said:

Garmin's handlebar mount's not strong enough for a mountain bike though

Do tell? Mine has been on the bike for 2 years now, no breakage or battery turn-off. I admit i
don't mount the GPS on every ride (shuddup, Shaun....), but the mount survives - and this is with
a rigid fork, as I'm sure I've mentioned before. ;-)

Steve

Same here, and mine's sometimes even mounted to a road bike, the ultimate harsh ride.

The Garmin mounts that I've seen break were tightened gorrilla tight on the bars. I've seen some
so over tightened that they're cracked near the screw. The mount only needs to be tight enough for
the GPS to not move under normal riding, but loose enough to move in a crash. For extra insurance,
I wrap the hand lanyard around the bars and clip it to itself with a mini 'biner.

My eTrex Vista has survived several mountain bike crashes, and a *wild* 35 mph road bike vs.
sandy, wet railroad tracks melee.

The road bike wreck destroyed a shifter lever, a helmet, a handlebar, a fork, a pair of shorts,
and parts of me, but not the GPS.

Barry

The bracket didn't break -- it kept losing the GPS. The screw combined with the double-sided tape
wouldn't hold a 4-battery unit. The screw ripped-out and I was afraid to put a bigger one in (I had
no idea what electronics I might total if it's even a little too long).

David

David Kunz said:

The bracket didn't break -- it kept losing the GPS. The screw combined with the double-sided tape
wouldn't hold a 4-battery unit. The screw ripped-out and I was afraid to put a bigger one in (I had
no idea what electronics I might total if it's even a little too long).

David

Oh! You had a II or III series unit!

I know what you mean about that mount. <G>

Barry

and that would help because...? "JD" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"R@nsh!" <ran@~Qfish.com> wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

Hi. Could someone please point me to resources about popular bike computers distance measurement
error?

Yeah, learn how to use a damn map and friggin compass.

JD

Stephen Baker said...

Quoted message said:

R@nsh says:

Quoted message said:

and that would help because...?

Because then the inherent inaccuracy of a piece of electronics wouldn't matter. You measure the
distance travelled on the map, having timed the ride, and there is your speed. Simple, efficient,
no batteries, etc.

HTH! Steve

I assume you are being sarcastic, but in case you aren't that would only work if you had a map for a
particular trail and you completely trusted the distances given, which would be stupid. For $30 and
a half hour of setup time you can get a damn nice computer which will give you accurate numbers. No
need to be a retro-grouch for something so useful. If you time the ride you still need a watch, but
if you have a computer, you can leave the watch at home and not get a tan line on your left wrist.

B a r r y B u r k e J r . <Keep it in the [email hidden]> said...

Quoted message said:

Bzzzt. Wrong! <G>

All bike computers have some sort of error tolerance. For example, the published error for a
Shimano Flight Deck is +/- 1% for speed, 30ppm for the clock, 50ppm for the stopwatch and ride
time, and .05% for trip and overall distance. This info is located in the manual.

Other units probably have similar tolerances, except they might not be published.

Well no [censored]. Damn near everything has 1% error. Those are some small numbers you posted. My point
to the OP was that there might be a way to program his computer for better accuracy. If he is
worried about 1% error, he should find something else to obsess about.

Super Slinky said:

Well no [censored]. Damn near everything has 1% error. Those are some small numbers you posted. My point
to the OP was that there might be a way to program his computer for better accuracy. If he is
worried about 1% error, he should find something else to obsess about.

How do you know what he wants to do with it? For instance, a consumer GPS can often be considered
extremely accurate for the outdoor enthusiast. For a surveyor, the same GPS might as well be
miles off.

You said, "No error", did you not? <G> The errors I posted are significant enough for Shimano to
include them in the manual.

Barry

Super Slinky <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

Stephen Baker said...

Quoted message said:

R@nsh says:

Quoted message said:

and that would help because...?

Because then the inherent inaccuracy of a piece of electronics wouldn't matter. You measure the
distance travelled on the map, having timed the ride, and there is your speed. Simple,
efficient, no batteries, etc.

HTH! Steve

I assume you are being sarcastic, but in case you aren't that would only work if you had a map for
a particular trail and you completely trusted the distances given, which would be stupid.

No, stupid is weighing down your bike with useless electronic [censored].

Quoted message said:

For $30 and a half hour of setup time you can get a damn nice computer which will give you
accurate numbers.

For $30, I can drive to the Monarch Crest and back. Riding one of the most epic rides in the country
sure beats the hell out of a piece of useless [censored] on my handlebars. Numbers, yeah that's important.

Quoted message said:

No need to be a retro-grouch for something so useful.

No need to listen to the hype and buy everything the media tells you that you need. Mindless drones
are exactly what they need to keep the machine oiled.

Quoted message said:

If you time the ride you still need a watch, but if you have a computer, you can leave the watch
at home and not get a tan line on your left wrist.

And that would give you higher style points with all of the other trendoids.

JD