I took my bike back to the dealership yesterday, cause i figured my speed was off by a little bit.

So the sell guys has a gps thingy in his car that tells you your exact speed. So off to the highway we go, When he gets to 55 he gives me a signal and my speedometer says 61 mph and then we bump the speed up to 70 and he gives me the signal that he is at 70 and i look down and mine reads 76.

When we got back to the shop he tells me that by law all the speedometers can be +_ 10% off and although mine is right there on the edge of 10% there is nothing that they can do about it :(.

Now i do know that speedometers will be slightly off but my almost 6mph? that seems kinda high. This bike is still stocked w/ nothing done on (so far :))

I quess my question is, Is this reasonable or should i tell them to fix it?

I quess my question is, Is this reasonable or should i tell them to fix it?

The dealer can't fix what is not broke. If it is a design flaw or purposely done by Suzuki, there is not much a dealerships service dept can do for you.

Their are a number of factors that can cause the speedo to be off even. Some people say the variance on speedo's is greater at higher speeds but i've tested the speedo in a few of my cars before using expensive GPS devices that measure speed and i've found even my cars speedo to be off by 1-2mph only at well over the speed limit. (Notgonnasayonefiftyish) Just remember how much it is off and ride that much faster. ;)

It is different though CSI jason on a bike.

They are off some... almost ALL of them read aout 5 MPH fast at 80 MPH or so...meaning if yo hang with a car at 80, your read 85 or so.

But they DO get off more and mroe on bikes as speed increases. This is due to wheel slipage, which can be upwards of 10-15 MPH at full speed 6th gear pinned. AMA factory superbikes have been shown to spin the rear even more than that at full speed (approaching 200)

The difference is a bike doesnt weigh enough to provide the traction needed to over come wind resitance (bikes Coeeficient of Drag actualy sucks compared to a car).. yet they DO make enough horsepower to spin the wheel up at that much resistance. a car wont do the same because of contact patch and wiehgt.. as well as superior aerodynamics over a bike.

Wow, well that explains a lot...

With my big ass on the bike, I shouldnt have a problem with traction. ;) At least i've lost 10 pounds since I got the bike so i'm happy.

i would just leave it. If you know it's off by 6 mph, just remember that.

There are two types or ways to have a speedometer calculate speed on a motorcycle...by a cable with a roller on the end which spins inside the front wheel's hub, or with a digital sensor, similar to a bicycle computer (if you are familiar with those) The cable type is actually the most accurate only 1-2 mph off because it is in direct contact with the wheel. The sensor type are typically 10% off because they measure off the front sprocket speed, not your wheel speed.Calibrating speed this way is hard because of the loss of power transferred to the rear wheel by the chain. Try this and you'll see...

Go an indicated 75mph in 3rd gear next to someone doing 75 and then do 75 mph in 6th gear next to someone doing 75. In 3rd gear, they slowly pull away from you.

Yeah, that's one of the first things I noticed about the bike; it seemed to read a little faster than I felt I was actually going. I went riding with a buddy who has a 2005 750 and our speedos were dead even at 55 mph. I think that's just the way they are.

U can always get a speedohealer SPL has one I was thinking of getting one also

Actually by law they are allowed to be off only +,- 3%. They test them at 30 and 60 MPH and the results can be found in most cycle mag tests in the spec's section.

Suzukipro

There are two types or ways to have a speedometer calculate speed on a motorcycle...by a cable with a roller on the end which spins inside the front wheel's hub, or with a digital sensor, similar to a bicycle computer (if you are familiar with those) The cable type is actually the most accurate only 1-2 mph off because it is in direct contact with the wheel. The sensor type are typically 10% off because they measure off the front sprocket speed, not your wheel speed.Calibrating speed this way is hard because of the loss of power transferred to the rear wheel by the chain. Try this and you'll see...

Go an indicated 75mph in 3rd gear next to someone doing 75 and then do 75 mph in 6th gear next to someone doing 75. In 3rd gear, they slowly pull away from you.

has nothing to do with the Sprockets or the way it is sensed.

It has to do witht he fact that the rear wheel slips, and the front does not.

There is some mechaninical variance but that is the most of it

thanks for the input and responce guys. I just wanted to see what everybody else thought.
Now that i know it is 6mph off I can just adjust the speed that i ride to make sure i'm going the speed limit:rolleyes

i just went by one of those police things that tells you your speed and it said i was goin 60 when my speedo said 65

Calibrating speed this way is hard because of the loss of power transferred to the rear wheel by the chain. Try this and you'll see...

Go an indicated 75mph in 3rd gear next to someone doing 75 and then do 75 mph in 6th gear next to someone doing 75. In 3rd gear, they slowly pull away from you.

:wtf Power transfer has absolutely nothing to do with it.

It's real simple. The speed is calculated, not measured. It starts at the rear tire. Is it 75" around or 74" around? Then you have your sprocket ratio. If it's 11 in the front and 44 in the back, then it's 4:1. Meaning that your front sprocket has to turn 4 times for the rear (and rear tire) to turn once. So speed is calculated by the computer sensing how many times the front sprocket has truned devided by the spocket ratio, times the rollout of the tire, all devided by the unit of time. There are error factors too. Tire swell, creepage, wear, and deflection. Tire profiles across manufacturers. Instead of pissing you off by getting a ticket when your speedo said 55, the engineers fudged the numbers so the computer thinks the rear tire is bigger than it really is. If your rear tire is smaller than what they hard coded into the computer, then your speedo will read fast. And it will read slow if your tire is bigger than what it programmed.

Take a good bicycle speedometer. The programming process is done by doing a wheel rollout. What does one full revolution measure on the ground to the nearest 5mm. I think motorcycle makers should give this ability to the owner. Perform a rollout. Input the distance and sprocket numbers. Speedo will be more accurate that way. Problem is that shady people will program it so the miles don't tick up as fast. But they can just disconnect or fool the sensor already, so why not?