MAX SPEED??????????

[zzuke10]

I know that our speedos do have a degree of error in them, and I am confident that my "9" is much faster after having my JSD=(TRE), FI 2000r, and then swapping it out for an Powerpro, modifying my exhaust and a few other performance mods, and I am convinced that it is much faster and pulls harder and is overall a vast improvement in the prerformance.I however am a realist and I am pretty sure my speedo is not telling me the truth.I just wanted to know if anyone has clocked their bike at a racetrack or, had their speed measured professionally, by getting their speedometer calibrated and have an accurate reading on the speed of their bike pre calibration and after.

[The HUFF]

GPS will give you your speed pretty accurately.

JSD won't make your bike any faster than it already was, just smooths it out a bit and removes the top speed limiter. Also the speedometer is an incremental error. Inother words. It's pretty accurate at slower speeds but as the speed increases the amount of error increases also.

[MATT'sADDICTION]

GPS will give you your speed pretty accurately.

JSD won't make your bike any faster than it already was, just smooths it out a bit and removes the top speed limiter. Also the speedometer is an incremental error. Inother words. It's pretty accurate at slower speeds but as the speed increases the amount of error increases also.

I agree with Huff, here. And, as Huff said, the speed limiter is removed in the top gear which will allow you to take it as fast as you have the nerve to go.

With mine, I discovered it is about 5 mph off at 75-80mph. Meaning at 80, I am actually going about 75. Not long after I acquired the bike, I decided to see what she would do on a mostly deserted four lane divided highway. I was on a slight uphill grade heading toward Globe AZ. I let off at 144 on the clock. It was fast enough. The bike had more, but I didn't. Quite impressive on a visible grade heading up the foothills. Not sure what that would equate to with the error I described earlier, but it felt (and I have done plenty of high speed runs in vehicles, both on the track and off) like I was definitely in the mid to high 130s.

Recently, I was returning home on I-80 east of Reno. I was clocking the mile markers with my watch and checking the speedo in relation. What I found surprised me, because it was closer than I though it would be. I was doing consistent 33-34 second miles. That equates to about 101-109 mph, give or take a second or two. My speedo read 112-115. So, I don't know. Without a GPS, who knows how far off they are at any given speed.

There is a device called Speedo Healer,by HealTech, which recalibrates the speedometer. I have been tempted to buy one, but not convinced I want to shell out $120. Anyone out there tried one of these? http://www.healtech-electronics.com/

One thing that will create a marginal, but significant difference is the diameter of you tire. Thus, from one manufacturer to another even the same stated size, may be taller or shorter than a competitors. And if you are running a fatter rear with the same 40 aspect ratio (250/40/1, which I do, 250 v 240, that will be a little taller tire, which will move the speedo in the right direction to correct for its over stated speed.

So, in a nutshell, they are off. You are not going as fast as the stated speed. The accuracy will change with the wear of your rear tire. Meaning you will be traveling a stated faster speed with a bald tire than you were with a fresh one. Try explaining that to the police officer. "Well, as you can see Mr. Officer, I just replaced my rear tire, and my speedometer was only reading 65. This tire must be taller with all that new tread, and now, thanks to your radar, I know at 65, I am actually doing 74. Thank you very much for helping me calibrate my speedo, Sir. I'll be more vigilent at keeping my eye on her with new tread."

If I have some more time this evening, I'll do the math to see what a half an inch in diameter will do percentage wise to the speedo. May not be much, but it is something.

[Mntsnow]

Way back awhile ago Lamonster posted a pic of his GPS reading 152mph. I posted my official time slip from out at the Bonneville Salt flats with my trap speed at 149.6mph and that was with the bike totally wrung out...and my speedo had been pegged way before the traps....

The M's speedo on average is 7 to 9 % off (reading High... meaning shows more speed than actual).

Thus 65 actually is 60.45mph at 7% off
85 is actually 79.05
100 is actually 93
120 is 111.6
140 is 130.2
150 is 139.5
160 is what my speedo would have need to be able to show when doing 149

[jimmy450r]

you can do a top speed run on the dyno and get an idea what you bike would do with no resistance from wind, grade etc.

give or take a few miles per hour @ 145-152 mph its all fast as hell on a cruiser

[antmor69]

I've seen it posted by a member on here in the past that he achieved 154 mph on GPS.

[fatboy99]

Sometimes talking about topspeed on our bikes is like telling fishing stories.....