What is the best speed to find out how off my speedo is

[scrapp]

I have a jim alhmans speedo healer (just so people know what version im using) and I also have a GPS

My question is...at what speed should I use for an example to find out how off my speedo is? from 10-50 my speedo is 5mph off, and then higher then that (I only went to 100) my speedo goes 10mph off. Trying to not "condone" speeding....lets say I find out how much the speedo is off at like, 130mph, will that give acurateness across the whole lower speedo, or will it be too great a change for the lower mph?

Right now last time I checked, when Im doing 60 it reads 70. so if I set it for 16.5% off (thats what I came to) will it me wrong for the lower gears?


Cliffnotes: I dont know what speed would give enough "information" to use as an example when doing the math to figure out how off my speedo it, to make my speedo read correct for lower mph, and higher mph. Trying to get it correct across the whole spectrum.

[Rigor]

Originally Posted by scrapp

I have a jim alhmans speedo healer (just so people know what version im using) and I also have a GPS

My question is...at what speed should I use for an example to find out how off my speedo is? from 10-50 my speedo is 5mph off, and then higher then that (I only went to 100) my speedo goes 10mph off.

If it's off 5mph at 50, and off 10mph by 100, then you're off by 10%.

5mph at 50 mph IS 10%.......

Do your testing at 50mph, and just double the difference to get your percentage.

[scrapp]

Would it also help if I told you Im one tooth down in the front, and also have a 180/55 tire? (seeing as how there have been RC people before me with the same mods, some kind of information I would assume be known)

cause using 70/60, I did the actual speed / shown speed - 1 x 100, and got 16.6%

[Eric04]

that is the correct formula.

[scrapp]

But im getting diffrent percentages. if I do the 70/60 I get 16.6 (16.7 on speedohealer calculator) and if I do 70/65 on the chance im wrong, its 8%
doing something like 100/90 gives me 11.1%

The speedohealer is in the mail, so I guess i will just have to wait till I get it, and experiment with the GPS and it, to see when the speedo goes off course again.

Speedohealers online calculator says this:
It is recommended to note the indicated speed at about (60mph) actual speed.

So I guess that means make the bike go 60mph and then see how off the speedo is?

[Eric04]

exactly... ride at 60mph on the GPS, and note the what the speedo says. Then apply your formula and adjust the speedo healer as necessary. You should be *around* 15% or so.

For the record - don't kill yourself trying to get it perfect cuz you never will. just get it close and call it good. I'd say 1-2 mph at 60 is close enough and better than most cars.

[scrapp]

So will my speedo start to get off again AFTER 60?
Also, im getting confused as to what im reading on speedohealer.com, it says that you can fix the speedo, but the odometer will still be off

[Eric04]

it's a ratio. The faster you go the bigger the error. That means that if you're off 1 mph at 50, you'll be off 2 mph at 100. If you get it dead perfect, it will be perfect everywhere, which is impossible because of so many variables. For example, as your rear tire wears, it's circumfurence (sp?) get's shorter, which throws off the speedo slightly. At high speeds, the circumfurence gets longer because the tire actually expands, throwing the speedo off. It'll NEVER be perfect!!!

The odometer must use a separate set of parameters that are not re-calc'd by the speedo healer. Your bike will accumulate mileage faster than if you left the stock gearing on. It's a small price to pay for the performance increase.

Don't over think this stuff

[dhdrider]

Originally Posted by scrapp

So will my speedo start to get off again AFTER 60?
Also, im getting confused as to what im reading on speedohealer.com, it says that you can fix the speedo, but the odometer will still be off

Nope, it doesn't matter whether your going 1 or 205, your speedo will always be off by the same error %. Just look up the percent error you calculated in the Ahlman instructions, and set the dip-switches to that setting. After that, you're good to go at all speeds. Also, after that, the odometer will be incrementing correctly as well.

[El Pozzinator]

dhdrider,

i believe you have erred slightly. while most (all) manufacturers set their speedo optomistic, it is illegal to set the odometer anything but as accurate as they can reasonably get it. if i recall ahlman's website correctly, the speedo and odo are receiving data pickup from the same sources but they compute values differently; as such, when you enter the correction factor the signal is applied to both the speedo AND odo, which will throw your odometer off as well. i recall seeing a table specifically addressing re-gearing the bike, and you can get either an accurate speedo (odo accumulates slower than actual), an accurate odo (speed reads higher than actual), or a "good compromise" (speed reads slightly higher and odo reads slightly lower than actual).

anyone feel free to correct me if i'm wrong here, as i may well be... but i don't think i am, unless i'm recalling mr ahlman's webiste details incorrectly. i cannot access the website from here to post justification, which is why i'm caveating with the phrase "as i recall". it's been a while since i've been on the site (about 10 months and counting) so like i said, i could be wrong. if so, some one please enlighten me.

-poz

[scrapp]

yes, speedohealer.com talks about that in their online calulator.

Im gonna set it for acurate speedo, since the bike should have 13k miles, but because of the previous owners joy of a new gear, I read 16k, BOOOOOOOOO

[Tech]

I am running a 15/40 sprocket setup.

I used the Jim Ahlman calculator to set the SpeedoHealer.

Total speedo error +12.5% Total ODO error + 6.7%

SpeedoHealer calibration value

Optimize Speedo -11.1% Optimize ODO -6.2%

I used the Best Compromise of -8.8%

I am satisfied with this setting.

[johnny929]

Speedo healer is the best way and best price to fix the problem, it's super easy to set up and works like a champ.

[scrapp]

well right now its set ON THE DOT, at 14% ....I dont get why 14, that throws all my math and speedohealers math, out the window.

Im considering going lower to maybe help compensate for the odo, but I dunno how low, seeing as how my math didnt prove shit.

[scrapp]

Ok Im still a little confused, if anyone can give me some imput it could help.

i set the healer (remember its really a jim alhmans) to 16%, and that did not fix my speedo. I ended up putting it at 14% and its ON THE DOT correct. (apparently I didint look at the GPS correct, and was doing 68mph at 60, not 70mph)
I did some math on the speedo calibrator, and if I put that at 60mph im reading 68.5mph then it gives me +14.2% (suprise!)
THEN I did the other calculator and got my reading based on my gearing change and the +5.5 factory error (it pre-determinend the +5.5 so I left that)
with my gearing change it gave me +13.8%

So I see my mistake, and my correct SPEEDOMETER fix is 14%

Question is, how off is my ODOMETER then? I want a best compromise and it gave me this information:
Best compromise = -9.8% (so basically 10%)

So do I subtract 10 from 14, meaning, on the ahlmans calibrator, do I set the value to 4%?


BTW, if this helps anyone, which would you rather choose?

a) Optimize for Speedo:
- Use this if you want to compensate both for the sprocket conversion and factory speedo error.
- Speedo will be 100% accurate
- Odo will register LESS kilometers/miles than actual (by about 5.2% usually)

b) Optimize for Odo:
- This is the default condition on a stock bike. Use this if you want to compensate only for the sprocket conversion.
- Speedo will read higher (by about 5.5% usually)
- Odo will be 100% accurate

c) Best compromise:
- Speedo will read slightly higher (by about 2.8% usually)
- Odo will read slightly lower (by about 2.7% usually)

[Ozzie TJ]

ok, well.... now that your sorted it wont matter much, but.............


just to make u lose sleep again pondering variables....

how long did you measure the speed for??? i.e. over what distance. Cause just going down the road @ x speed for 10 secs or so is going to be WAAAY in accurate with a GPS. You have to remember GPS accuracy depends on availability of satelites... and before you jump up and down and say "but i got a you beaut crap shit finder 5000 model"...... unless you are SF or other applicable military unit with MILSPEC GPS, your accuracy is reduced to 5m radius whilst MILSPEC is down to 50cm..... so you would need to measure this over a long distance for better accuracy by mainitaining a constant speed for say an hour and use the avg. function. THEN you'll be able to compute it better..... but... thats riding on a billiard table with no traffic and rock steady throttle hand.......


sorry to be a prick, but it always seems to be my job to annoy anal retentive types (myself included!)

bye from Aus!

[scrapp]

we strapped the GPS to my bike, and went riding, total time with the GPS? prolly a total or two days, I horded that thing hardcore, and watched my varried speeds at all times. Im more then sure I got it acurate