Help me understand gearing/speed.

[jphilipson]

K, so I was curious about how far off the speedo was on my 2k8 Busa. The other day when I was riding I took note of speeds at RPMs. At 4500 RPMs, my speedo reads @ 82.5 MPH. So I compared that to the chart on gearingcommander.com for stock gearing, an behold; they show 82.4 MPH for 4500 RPM's in 6th. Does that mean that my speedo is actually accurate?

[jsjdjn]

Use a GPS or radar to get a real speed. I have seen them up to 10% off. Most of the time indicating faster on the speedo then you are really going. I love speedo healers. 10% means you really have 10% less mileage on your bike then what it says.

[jphilipson]

Originally Posted by jsjdjn

Use a GPS or radar to get a real speed. I have seen them up to 10% off. Most of the time indicating faster on the speedo then you are really going. I love speedo healers. 10% means you really have 10% less mileage on your bike then what it says.

Yeah, I will get the gps on it soon.. I was just curious about it seeming accurate.

[StromBusa]

Does anyone know if the GPS corrects for elevation changes, Speed off a cliff for example. Wiley coyote style?

[jsjdjn]

The one I had from ACME did!

[jphilipson]

Originally Posted by StromBusa

Does anyone know if the GPS corrects for elevation changes, Speed off a cliff for example. Wiley coyote style?

There is only one way to find out..

[Mr Bogus]

it was posted here by a couple owners that the speedo was pretty accurate on the Gen2 bikes..

what do you mean by altitude correction? if you are falling you are moving.. GPS can read that..

now will it calculate your speed of "return to earth?" who cares?

if you are going fast enough to measure? you wont need the data...

[k03gsxr750]

Originally Posted by Mr Bogus

if you are going fast enough to measure? you wont need the data...

True story. I think with GPS speed is only measure speed horizontally meaning regardless of your decent speed it will just show the speed you are traveling left or right if you were looking from straight down.

[blusmbl]

Originally Posted by k03gsxr750

True story. I think with GPS speed is only measure speed horizontally meaning regardless of your decent speed it will just show the speed you are traveling left or right if you were looking from straight down.

Makes sense. So your speed isn't completely accurate, since it isn't calculating with the correct distance you've traveled due to elevation.

[Got-Busa?]

Originally Posted by jphilipson

K, so I was curious about how far off the speedo was on my 2k8 Busa. The other day when I was riding I took note of speeds at RPMs. At 4500 RPMs, my speedo reads @ 82.5 MPH. So I compared that to the chart on gearingcommander.com for stock gearing, an behold; they show 82.4 MPH for 4500 RPM's in 6th. Does that mean that my speedo is actually accurate?

The gearing chart on that site for the BUSA is ALL wrong. They are about 6-9mph optimistic...

[jphilipson]

Originally Posted by Got-Busa?

The gearing chart on that site for the BUSA is ALL wrong. They are about 6-9mph optimistic...

That's what I thought.. I've been comparing my speeds on the highway to what I know to be the average speeds that other cars drive on those roads, an also when I pass radar signs, it always reads a few MPH lower than what is on the bike. Guess I just need to get a GPS..

[slatroni]

Radar works best! just Blow buy your local LEO! He will tell you your speed!

[TruWrecks]

I posted a gear calc speadsheet a while ago. Do some searching. It's a bit more accurate than the gearing commander site.

GPS on a hill is pretty accurate. My Zumo has stayed within 1 or 2 MPH of same amount of my speedometer last year on my trip through Colorado. I went over a few very steep passes with very little variance.

Unless you live at the Bonneville Salt Flats or central Florida a GPS that doesn't account for elevation would be pretty useless.

[dadofthree]

I need to barrow a GPS, but my Gen II is looking pretty darn close.

[bpjones]

Speedohealer did the trick for me....the 99 was off 11%

Might not sound like much but 65 indicated was really 57.85 (off 7.15) and 180mph indicated (off 19.8mph) was really 160.2...all these were with a 43 rear sprocket.

Based on these numbers an uncorrected speedometer is the only way a unrestricted stock 99 or 2000 can do a indicated 220mph...because it's really +/-195.8mph!