Speedometer accuracy

[FJReady]

Finally got my Sigma bike wheel/trip computer gizmo installed. Pretty much followed www.FJRtech.com instructions. Thanks Warchild.

I was very accurate measuring my rear tire diameter/circumference so I am confident that the output is accurate.

Results:

when FJR speedo indicates 70mph, the Sigma shows 69.0 Pretty darn close. Maybe tonight I'll have a chance to explore some higher ranges.

Lots of fun to play with the data afterwards. just for ***** and giggles.

Rear bracket is the same stuff I make the helmet holders from: .032x.75 stainless.

Little magnet is held on with a drop of epoxy on the brake rotor. So far its seen 100mph. We'll have to wait and see how it holds up.

Handlebar bracket is a piece of 5052 Aluminum (3/16" thk) I had lying around. Bolted to the formerly unused mirror hole.

 

[BlueHammer]

Nice install. Very Sano.

@70 on the speedo, my Garmin reads 67.9.

 

[ionbeam]

Very nice install. I may be looking at my next winter project I'm going to have to check it out the next time we meet. When I ride with my brother, his ST will show a trip mileage of 350 miles while my FJR shows over 370 miles. Sigma should sort that out!

This week the town of Auburn, NH was kind enough to put up a speed board. My FJR speedo reading of 60.0mph resulted in a 57/58mph flicker on the speed board. I also picked up the speed board on my radar detector .4 miles before the speed board. The 'board didn't read out my speed until I was roughly 100' from the sign. Be warned, while I was within sight of the sign it always read the speed of the car behind me, not my speed. I would sure hate to get the cager's speeding ticket. :bigeyes:

 

[Ignacio]

Smooth install. You really took your time making it look finished.

I have my BC1600 "WS" set to 1189 and it's pretty close with my Avon through the median of it's life.

I went through a process to calibrate it using a battery operated GPS. I rode 9.98 miles with the GPS and then read the Sigma. From memory it showed 9.93 miles. Using some Algebra I then adjusted to the 1189 setting.

Rode another 9.96 mile stretch using GPS and the Sigma showed the same 9.96 miles.

Tried again with the tread toward the end of it's life and think the Sigma showed 0.02 miles higher on a similar loop.

You could drive yourself batty trying to keep it perpetually dialed in given tire tread, pressure, air temperature, loading, etc.

 

[FJRocket]

Using some Algebra I then adjusted to the 1189 setting.

(Nice Install!!!! Cool that the unit is THAT accurate! )

 

[Warchild]

Nice install, FJReady.

Link to the original install page for those who haven't seen this yet:

FJRTech: Sigma Cyclometer Installation

 

[Ignacio]

Using some Algebra I then adjusted to the 1189 setting.

You caught me.

More precisely.....I fumbled horribly and had to work the numbers in Excel and after adjusting once the wrong way I finally stumbled across the right combination.

Then, suddenly, I had a flashback and remembered the ratio thing from some high school algebra teacher I despised.

9.98 9.93

----- = -----

x 1183

Solved for x and came up with 1189....I think

 

[FJRocket]

Using some Algebra I then adjusted to the 1189 setting.

You caught me.

More precisely.....I fumbled horribly and had to work the numbers in Excel and after adjusting once the wrong way I finally stumbled across the right combination.

Then, suddenly, I had a flashback and remembered the ratio thing from some high school algebra teacher I despised.

9.98 9.93

----- = -----

x 1183

Solved for x and came up with 1189....I think

SQUARED

 

[Groo]

Just curious... if you've got a GPS, that can tell you average speed, top speed, and other various trip functions (i.e. a Garmin 2610) etc., what value does the Sigma add to that?

 

[twowheelnut]

It's the farkle factor, Groo. How much **** can we bolt on the bike, ya know?

 

[Groo]

Ah... thought there was some additional information to be gleaned... hey... I'm just about pushing maximum farkle density right now... trying to find space to cram in the PCIII at the moment... gotta move some stuff around under the seats.

 

[Warchild]

Just curious... if you've got a GPS, that can tell you average speed, top speed, and other various trip functions (i.e. a Garmin 2610) etc., what value does the Sigma add to that?

In the Iron Butt community, we used them for those times you drop the GPS signal when going through long tunnels, or a steep canyon/mountainous area where the signal comes and goes, etc, etc.

Also, the Sigma is an approved substitute for your bike's stock speedo, should the latter go **** up during the rally. The GPS is not an approved substitute.

 

[Ignacio]

Just curious... if you've got a GPS, that can tell you average speed, top speed, and other various trip functions (i.e. a Garmin 2610) etc., what value does the Sigma add to that?

I was waiting for that.

Pretty simple for me. Besides the tunnel thing Warchild points out, my GPS (Garmin Legend) is powered by two AA batteries that lasts between 6 to 10 hours depending on ambient temperature and probably other variables. When I'm riding I rarely have the sucker turn off when I'm stopped for gas. The Sigma keeps track of these things regardless of the GPS. It's about as bulletproof as the stock speedo and way more accurate.

Now, I just bought a 2730. I think the Sigma will now become more of a back-up system and I will use the 2730 since I plan to hardwire it. I also never, take it off the bike and often run without the GPS on day trips.

 

[Groo]

Well, one question begs another...

Dale, Why do they exclude the GPS info.? Less reliable? The signal dropout makes sense now that you mention it.

Iggy, that would make sense too... my GPS runs off the cycle supplied 12V, so I didn't think about the non-hardwired GPS losing power.

 

[twowheelnut]

I'll guess that because GPS's can be programmed, hence allowing riders to cheat?

 

[Shane]

Why do they exclude the GPS info.?  Less reliable?  The signal dropout makes sense now that you mention it.

Another possibility,

Not that anybody would actually want to try it, but on a rally it would be quite easy to just leave the GPS powered on and transfer it to a friend in a car or something. The Sigma keeps the honest people from cheating.

Kind of like the old saying, "locks keep the honest people out".

True dat,

Shane

 

[Ignacio]

Well, I don't know about all that, but if somebody wants to cheat I don't think there's something hugely magical about a Sigma that stops it. Sigmas can be moved around just as easily. Somebody in a car is still going to have to drive those miles and if they can do it better than you on the bike--well that rally is probably a waste of your time.

Far more important than one piece of componentry that is, at best, an ancilliary device to rallies--it's security is easily compensated for by attentive rallymasters, logs, photos with time and mileage, bonus site observers, and other methods we probably don't know about.

Maybe I'm naive, but I get the impression the number of cheating instances have been fairly low. Get caught and in this small circle of people you'd become a pariah pretty quickly.

 

[donaldb]

I had always believed that the GPS was more accurate w/respect to MPH than your speedo. The GPS always showed my actual speed at about 5 mph slower than what was showing on the speedo, that holds true for my feejer and my previous cruiser. Interstate speed I usually maintain 80 on the speedo and about 75-76 showing on the GPS. I don't have a GPS, but a couple of my buds have them and we have never had any LEO problems. So, what gives? is my assumption wrong? how much is one of these farkle Sigma doo hicky's

 

[twowheelnut]

Maybe I'm naive, but I get the impression the number of cheating instances have been fairly low. Get caught and in this small circle of people you'd become a pariah pretty quickly.

That's what I was thinking: It's not like there's a big check waiting for the winner or nuttin', either...