[Jack Leis]

  my curiosity got the best of me today and decided to compare my speedometer against my trusty Garmin c330 streetpilot. I half ass-ed mounted the gps to the top of my tank and went for a spin. All the way from 15 to 75 mph the speedometer was reading exactly 5 mph over what the gps was reading. I have checked the gps on long trips in the past with mileage markers and it has always been spot on. Next time I have a cop behind me at least I know to subtract the 5mph.

[birdmove]

....and that is about industry standard for motorcycles and scooter.

    Jon

[GSS]

My C5 was off by about the same with OEM tires.

[Alan LaRue]

On previous bikes, it has seemed that the speedometer was about 10% high. When it said 60, it was really only doing 54. 70 was really 63. I had only ever done the math by looking at a clock and mile markers, which isn't easy to do while riding a motorcycle. But in typical freeway traffic my experience told me that at an indicated 77 I was doing about 70.

The B5 didn't seem to be that far off, so I finally rode with a GPS today. Interestingly, it is further off at low speeds. An indicated 40 mph is only 35. However, an indicated 70 mph is actually 67, about what I figured from the traffic flow. The odd thing to me is that it isn't a certain percentage off, but I guess that's the nature of the electro-mechanical speedometer.

I've never been on a motorcycle that read high, so following the indicated speed always puts you slower than traffic and safe from law enforcement, unless they wonder why you're going so slowly.

Both of my current cars and the last car I had matched the GPS exactly. I understand why the RE is imprecise, but for most modern motorcycles to read so high I think must be deliberate.

[barenekd]

Most of the bikes I've had in the last 20 years read about 10% high, mostly Hondas and Triumphs.
My Enfield reads like Alan's which, for me, is close enough for gum't work.
Bare

[bman734]

Allen, sounds like a conspiracy going on over at RE.

[Alan LaRue]

Conspiracy... It did sound like that's what I was saying. What I meant was that 1) the RE is unusually accurate and 2) maybe the Japanese manufacturers bend over backward to make sure their speedos don't read low.

[barenekd]

My RE is considerably more accurate than any Japanese bike I've owned. They were all about 10% off. I used to add that to the RE, then found I was running10% over the speed limit. That could be enough to get a ticket!

Bare

[GreenMachine]

60 still feels like 60 to me on my enfield...I would hate to get a speeding ticket on a enfield..I mean come on give me a break officer...Its not a crotch rocket...Never GPS mine but I'm sure its off by 3 - 5 MPH...

[bman734]

When going 65 mph according to the speedo, I don't want to go any faster on these damn things to achieve a REAL 65 mph. I already feel like I'm going to be blown off the bike and it is also a reminder that I must be on the wrong road because these bikes are meant for back road fun, not freeway cruising. At least in my humble opinion.

[Alan LaRue]

I understand that "made for back roads" thought, and I'm sure a lot of people would wonder why I didn't get a V-Strom 650 or some such, but I actually bought the B5 intending to commute on it. That means a 36-miles-each-way ride, 33 of which are on I-10 (right through downtown Houston). Other than not having found a windshield that really suits me, I've been very happy with it for that purpose! It was nice to get some confirmation as to the seat-of-my-pants feeling about my actual speed.

[tooseevee]

I understand that "made for back roads" thought, and I'm sure a lot of people would wonder why I didn't get a V-Strom 650 or some such, but I actually bought the B5 intending to commute on it. That means a 36-miles-each-way ride, 33 of which are on I-10 (right through downtown Houston). Other than not having found a windshield that really suits me, I've been very happy with it for that purpose! It was nice to get some confirmation as to the seat-of-my-pants feeling about my actual speed.

          Speedos are notoriously Wrong. On my last garage-built bike I hooked up an electronic speedo (Sigma Sport BC 800). It is VERY accurate. You set it by measuring the distance in inches that your tire travels in X number of revolutions. Using a formula, you then input this to the computer & it gives you MPH & a dozen other things if you care. All I want is MPH & total mileage.

           The sender is fastened on the rear frame. The trigger is J-B Welded adjacent to it on the rear sprocket. Totally unnoticeable.

            The readout is an inch square & barely noticeable on my handlebar right next to the riser.

[Alan LaRue]

I would use the trip odometer feature. I may eventually get one of those.

[Ducati Scotty]

Lots of guys who do long distance rides mount bicycle computers.  Just check the web and make sure to get one that's accurate at higher speeds.  Some don't work so well over 50mph.  I always thought I'd use one of these if I ever did a custom build, they're so small you don't even know they're there.

Scott

[Lwt Big Cheese]

FWIW my speedo cable was missing when I bought my bike.

I fitted a cycle speedo and when checked with a gps it's very accurate


My car is 10% high.