About gearing and Speedo Error

[Guest]

Has anyone changed their final drive gearing (different size sprockets?)

Does this affect the speedo reading? What about the nileage count? If so, how much is it out...

[OB_DRAGBIKE_dot_COM]

Yes, it seems to be about +5mph with a -1 sprocket. Since these speedo's are not really accurate at high end speeds anyway (we had the bike at 180 radar speed, 196 speedo when it was unmodified), not sure what the real top speed is right now.

We're going to radar it again and check it at different speeds, when I return from Chicago in two weeks.

[OB_jeffw]

Yep you are screwed.... not really a good fix since the Busa is not a gear driven speedo.
It picks up magnetic pulses and computes from there.

[Guest]

To DRAGBIKE_DOT_COM, much thanks if you could post the results of your radar speed measuring...

I think a lot of people would be interested in that.

Won't tyre type/size/inflation be critical too? Even tyre wear can make a difference...

[Guest]

Is there any concensus on speedo error
at more "reasonable" speeds like 70-75-80mph?
Has anyone used something to verify the speedo error with stock factory setup?
It would be nice to know my actual speed without 'radar verification' if you know what
I mean

[OB_speed]

go to a dyno. It can tell you your actual speed. We did a top gear run on my bike and the speedo read like 215 @ the top of 6th which was acutally only 194 by the dyno calculations.

Next time I get on I will try to take some measurements on my bike at 10 mph increments. But would this vary from bike to bike .. yes/no/maybe ?

[Guest]

Trouble with using a dyno for speed measurements is that there is always SOME tyre slip when under power.

When using a lot of power like a dyno "run"
there will be quite a lot of slip... The most accurate type of speedo would be an electronic "bicycle" type attached to the front wheel, and calibrated exactly for that tyre size. There would nto be a lot of tyre slip on the road, but the tyre would still expand a bit at high speed...

Radar/laser anyone??

[OB_Slurpee]

What about these 'unmanned radar stations' Thats what I used to calculate how much over my bike was.
The city I live in puts them EVERYWHERE. They are suppost to be so you will know how fast you are going and slow down, but everyone I know uses them to see how fast they can go.
Take care..
Slurp

[OB_EXCLR8]

99TLR
If you run the dyno to speed and alow it to settle at each speed to be tested, this should not be a problem. It will not give you an accurate HP or tourqe rating though. The reason for the dyno not spipping at high speed after the speed has become stable, is that there is no wind resistance. The friction in the bearings on the dyno drum should not be enough to cause slip. If you do not agree please read info on dynojet dyno's theory and mode of calculation, before posting.

My 2 cents.

[Guest]

I agree totally! If you can get the dyno to stabilise there will be no real power needed to keep it turning and there should be little slip.

Don't forget that rear tyre wear is around 4.5mm from new to bald, and this is about 1.5% difference with the speedo too. I think Suzukis are calibrated with new tyre, as mine is quite worn now and reading almost 2% out (fast).

I measured it by using my trip meter on the freeway where there was a measured 5km with signs, put there for speedo checking.

[OB_Peregrine]

I assume the odometer is driven at the same inaccuracy as the speedometer (meaning, these bikes have less miles on them than they show), so I am going to go out at check it against the mile posts to see how far off it is.

If I had a GPS, I'd tape it next to the speedo and check it that way. Maybe one of you guys has one and can try this out.

[OB_speed]

Hey ! I am working on a GPS project developing a interface to a commercial GPS. I have one at my desk. I wil try to get it next weekend and go for a ride around Dallas and see what it gives me for a trip count.

Commerical gps has been degraded so it only accurate to 30ft. I guess thats close enough for our test. I doubt I would every really buy one because they seem to be expenisive toys.

[OB_jeffw]

I used a Garmin GPSIII on my GSXR1100 after installing new wheels (no front wheel speedo drive). It did work just great. Do remember that the US military will cause the GSP signals to "go fuzzy", or have pre-determined error inserted.

I did see my bike going 1-5 mph sitting still. Even so, it is still more accurate than your speedo.

[OB_speed]

yep. Garmin GPSIII. on my ride home from work today. it registered 10.8 miles and my speedo stated 11.3 miles.

I am gonna try to use it on a longer ride tonight to see if the ratio of error is similiar.

[rotts4u]

I have a Sigma bc800 bike computer on mine and I feel it is very accurate as you measure the circumference of the tire then the magnet just counts the revolutions of the front tire and use the distance you typed in to calculate the real speed.

At 100mph on the stock speedo the Sigma shows 89-90 mph.Making it about 10% with stock gearing. That means an indicated 200 is really 180. This also seems to support the people that have seen 220mph on speedo which would be a max of about 198 or so.Which also is about max therotical speed at redline (199 calculated based on final drive ratio.

The only problem is that the Sigma only reads to 169.9 mph

Don

[OB_KawAbuser]

rotts4u, are you useing a 41tooth rear sprocket from Dymag.

Could you post a table of corrected speeds for me so I will have at least an idea of how fast my speedo will be off with the Dymags.

Thank you.

[OB_Scoop]

Have a few friends with the Nevada Highway Patrol and will get some radar readings and post them relative to speedo output.

[OB_Peregrine]

Well, at least the odometer seems to be accurate. I checked it against the mileposts for two miles, and I'd have to have a 100ths mile decimal place to see any difference. Maybe two miles wasn't long enough, but that's all the freeway I have on the way to work.