I've only had my Heritage for a couple of months now, and just recently started commuting on it. I live in SW Ohio, and frequent Interstates 71, 75, and 275. I try to adjust and maintain my speed based on the traffic around me. I don't hold to the speed limit (65) if all of the traffic around me is running 73, for example... The thing is, in my car, my typical commute has me running pretty consistently 68-72 with the flow of traffic. On the bike, I find myself running with traffic, but my speedo is indicating 80+. I find myself thinking that there is no way that all of the traffic around me is running 15+mph over the speed limit, so I'll find a truck to fall in behind, level off my speed, and pace him, invariably to find I'm indicating a dead on, perfectly legal 65 MPH. So the question arises; how accurate is this cable driven dial on my dash? Am I just more attuned to the actual pace of traffic when I'm not in the cage? Admittedly, I probably crank a little harder on the interstate on the bike, just because I fear getting run over from behind, but good grief, for every car I pass, I'm getting passed myself!

 

Your speedo may be a little off, but I am very familiar with those roads and yes, the drivers don't pay much attention to the speed limit. I prefer to outpace the traffic by a little bit, but at least never be the slowest.

 

in jersey on RT 80 - 287 - 78 - the turnpike ( 95 ) of the parkway if your going slower than 80 they will run you off the road to get in front of you all are 65 but thats the exit ramp

 

Got a GPS? Strap it on the bike and find out how fast you are really going.

 

Plenty of Phone apps out there as well....

Ds

 

I'm using a phone app right now for my mustang. Always shows .the same exact speed as the speed signs going north on 71/75 towards the cut in the hill.

From day to day the average speed moves a lot. I'd say maybe your gauge is getting a little off the higher you get past 65, but my guess is your instincts are causing you to twist that throttle just that bit more to flow with traffic better than you are in your car.

 

Funny you should mention the speedometer/GPS apps on a phone... My Sportster didn't have any guages at all, so I had a mount for my phone so I could run SpeedView Lite for a speed and odometer. When I broke the mount, I never bought another one, and just kinda got used to riding with out it. I think the windshield is probably the biggest factor... On the Sporty, when you get up around 80+ the wind let you know you were humming right along. My Heritage has a huge plastic billboard and lower deflectors, so there is practically no wind at all! I'm gonna have to see if I can figger up a way to check speed with my phone without dropping it. I wouldn't be surprised if it's off, it is 20 years old, after all. It just seems funny that it'd only be off over 65.

 

No vehicle speedo is exactly right, except by chance. As the tyre wears it's diameter slowly reduces, so there is a difference of around 2-3% just down to that, from new to worn out. Increased weight will make the tyre squash more, reducing it's rolling diameter by up to a similar amount. Manufacturers usually err on optimistic, making the speedo accurate to 0 to +5% (in other words tell you your speed is up to 5mph more than it really is). A GPS will get as close to accurate as any of us needs.

 

I know all that, I was just wondering if there was anything inherrant in the design that would make the speedo read incorrectly at speeds in excess of 65. For example, my old man had a Suzuki Volusia that would read pretty accurately below 35 MPH, but the faster he went, the more radically off his speedo was. On the highway, it was ridiculous, off by as much as 10-12%! I think that was an electronic speedo though, and is a well known and documented issue. I wouldn't think that the cable driven arrangement on my bike would suffer those ills, but I thought I'd check with the braintrust as I continue to learn about my evo. Thanks y'all!

 

The only thing inherent in speedo design and manufacture is that they are not very accurate! And they are different across vehicle brands, even across models of any given brand. What you describe is not unusual.