Most bikes and cars speedo's report about 5% too fast (i.e. you are actually going 5% slower than it says). If yours is dead on and you didn't change anything then I'd be surprised. Your Dad's Harley is broken though. 
This is the first choice I bought from RAM mounts but I returned it because I didn't know I had to buy the cradle that attaches to the mount. Take a look and see if it's what you want.Ayu can you link the handlebar mount where I can buy it please? I've got a Garmin Nuvi 205
Could you post a pic of the mount attached to your bike please?This is the first choice I bought from RAM mounts but I returned it because I didn't know I had to buy the cradle that attaches to the mount. Take a look and see if it's what you want.
http://www.ram-mount.com/CatalogRes...d/082065080045050055052045049085/Default.aspx
This is the second choice that I ended up keeping and I got it off Ebay for about the same price. The ball on the mount fits into the standard cradle that came with my Nuvi 205. My GPS hasn't fall off yet so I guess it's a keeper!!!
http://cgi.ebay.com/MOTORCYCLE-BIKE...-205-205W-/130421824656?pt=LH_DefaultDomain_0
The dealer should've just sold him a Speedo Healer at an inflated price. hehI just got back from the dealer after having them install the recalled "rear brake bracket" and there was a gentlemen before me that complained about his bike being way off. The service manager tried to explain that ALL motorcycles are a bit off on the speedometer readout but the guy just wouldn't have it. He wanted it fixed and was starting to get irrate so I jumped in and said "Mine is off too but that's why I put a GPS on mine. The GPS readout is more accurate than the speedometer readout." After that, he just looked at me and the service manager and zipped his lips. On freeways, my speedometer display 69-71MPH while my GPS displays 64-65mph.
Get a cheapo Nuvi GPS like I did. I bought one from Craigslist for $45.00 plus the $15.00 for the handlebar mount. Not a bad price for having an accurate speedometer readout plus much more!!!
I don't really know how accurate mine or any other GPS is in term of real speed calculation but it's a lot closer than the bike's speedometer display. I rode past a speed trap on a local street a few days ago and saw a roadside cop pointing a radar at me. Street posted limited was 40mph. A quick glance down at the GPS showed 45mph and the speedometer readout displayed 49mph.So, everyone is using GPS devices to check their speedometers. Does anyone know how accurate commercial GPS devices are?