Speedmaster Speedometer Incorrect Reading

[t09spm]

I purchased a 2009 Speedmaster with 15,000 miles. I suspected the analog speedometer was reporting incorrectly and downloaded an app to my smartphone which seems to confirm this. The speedmeter appears to be reporting higher-than-actual speeds compared to the app, at an increasng inverval. At a speedometer speed of about 30 MPH the app is reporting an actual speed of 25 MPH . At a speedometer speed of about 65 MPH the app is reporting an actual speed of 55 MPH.

I checked the app versus the speed of my car, and it was within 1-2 MPH at all speeds.

I've read a few threads that suggest a slight overreporting of motorcspeed is normal, but this seems out of bounds. Is there any way to adjust the speedometer, or should I be considering a new one?

 

[Gavin1963]

I have a 2003 Bonneville America and mine is too far out too. When I'm going 70 it says I'm doing 80. This rate will depreciate the bike rapidly. I only have 6k on it now but when I only have 7k on it it will say 8k. If we could get an answer that would be greatly appreciated.

 

[CarlS]

On my two 2003 T100's and on my current 2012 800XC, the speedometers were/are about 7 to 8 percent optimistic. It seems this is deliberate and applies to other brands, too. However, the odometers on all three bikes were nearly spot on as determined by GPS and milepost markers. Apparently the optimistic speedometer does not affect the odometer. `

 

[t09spm]

Thanks for the responses. So it sounds like finding a replacement stock speedomenter on eBay or whatever wouldn't solve the issue. Too bad because I prefer analogue. Aside form the smartphone GPS solution, does anyone knoe of some other low-cost option to mount an accuate speedometer, say clamped to the handlebar? I think the motorists behind me are getting ticked off when I think I'm doing 52 in a 50 MPH zone but I'm really going 45.

 

[CarlS]

Thanks for the responses. So it sounds like finding a replacement stock speedomenter on eBay or whatever wouldn't solve the issue. Too bad because I prefer analogue. Aside form the smartphone GPS solution, does anyone knoe of some other low-cost option to mount an accuate speedometer, say clamped to the handlebar? I think the motorists behind me are getting ticked off when I think I'm doing 52 in a 50 MPH zone but I'm really going 45.

I was told by a certified motorcycle mechanic, that this "error" is dictated by lawyers. If one is speeding and causes an accident, the motorcycle manufacturer cannot be sued for a faulty speedometer reading. Legal CYA.

To answer your question, the cheapest solution is to ride 5 mph over the posted speed limit. I have been through enough radar to know what speed I am riding vs what my speedometer indicates. At 80 mph on my speedometer, I am actually doing 76 mph. The cops don't bother me at 75 mph in a 70 mph zone.

 

[markyoung286]

I've read on a number of sites that Triumph speedometers are purposefully 5-6% optimistic which is consistent with my observations of my own motorcycles (Speedmaster and America, both with 865 EFI engines).

On the EFI motorcycles, note that you can connect a laptop computer to the motorcycle's engine control unit (ECU) with a freeware program called "TuneECU" using a special USB cable that connects to the OBD-2 port under the seat.

Using TuneECU, you can select a percentage adjustment (down or up) for the speedometer. I've been able to fine tune the accuracy of my speedometer to exactly match the speed shown by my Garmin GPS and those "Your Speed Is" signs that measure your speed with radar.

A Triumph dealer should technically also be able to do this adjustment. Whether they would agree to do it, however, is probably another issue all together.

TuneECU has a lot of cool features and is easy to use. That said, users have experienced problems getting the computer to connect to the ECU. From what I've read, these problems typically result from using OBD-2 USB cables that do not include the FTDI chipset.