Speedo Heeler

[Skywalker]

I have been to the speedo web site and set my unit about three weeks ago. Don't have a GPS and such and I just don't feel I'm on the money yet. Hope someone out there can help me out that did have the same tires/sproket and did a GPS to get the exact or very close percentage. I'm running stock size tires and changed rear sprocket only from 40 to 43. I took the 5.5% factory error and when from there. With my setup can you tell me what percentage to set this at. I was running her hard last night and pulled only 140 and pucker factor was up. I'm thinking my -11.7 percent is to much? Please help a shade tree machanic out.... with some better settings for this thing! Thahks much.....

 

[Spudley]

I had mine set on a dyno, exactly 10% off, now it's tight. $30 bucks, worth every penny as I pace Metro-motos on the freeways...

 

[Skywalker]

I had mine set on a dyno, exactly 10% off, now it's tight.  $30 bucks, worth every penny as I pace Metro-motos on the freeways...

So, did you have stock tires and a 43t and I could assume I could us this percentage as well?

 

[proud dad]

17/42 gearing came in at -11.[check with GPS].I set it at -10.Speed reads real good.This was checked with a new tire.

 

[proud dad]

FWIW also checked the odometer with GPS.In 110 miles it was within 1.5 miles.Maybe I should go ahead and add the other percent.

 

[Vic_E55_2001]

I have been to the speedo web site and set my unit about three weeks ago. Don't have a GPS and such and I just don't feel I'm on the money yet. Hope someone out there can help me out that did have the same tires/sproket and did a GPS to get the exact or very close percentage. I'm running stock size tires and changed rear sprocket only from 40 to 43. I took the 5.5% factory error and when from there. With my setup can you tell me what percentage to set this at. I was running her hard last night and pulled only 140 and pucker factor was up. I'm thinking my -11.7 percent is to much? Please help a shade tree machanic out.... with some better settings for this thing! Thahks much.....

I have exactly the same setup 17/43 and I do have GPS. I was holding steady speeds 50-70-90 and calculated -13.7% error.
Now my speedo is dead on.

 

[SpeedGeek]

I have been to the speedo web site and set my unit about three weeks ago.  Don't have a GPS and such and I just don't feel I'm on the money yet.  Hope someone out there can help me out that did have the same tires/sproket and did a GPS to get the exact or very close percentage.  I'm running stock size tires and changed rear sprocket only from 40 to 43.  I took the 5.5% factory error and when from there.  With my setup can you tell me what percentage to set this at.  I was running her hard last night and pulled only 140 and pucker factor was up.  I'm thinking my -11.7 percent is to much?  Please help a shade tree machanic out.... with some better settings for this thing!  Thahks much.....  

I have exactly the same setup 17/43 and I do have GPS.  I was holding steady speeds 50-70-90 and calculated -13.7% error.
Now my speedo is dead on.

That sounds closer to a correct adjustment to me. I was thinking Skywalker's 11.7 wasn't going to be enough.

Factory error tends to be closer to -7.5% for most people (myself included). Mine is dead on at -16.7% with 16/42 and 190/55 tires. By dead on I mean I checked it with GPS and it is exactly 2 mph off no matter what speed I'm going. 65 indicated is 67. 100 indicated is 102 etc. So the percentage of adjustment by ratio is correct.

Also, remember that the speedo is off from the factory, but the ODOMETER is NOT. If you have the speedo set perfect, the odometer will will read about 7% lower miles than what what you are actually driving.

 

[Skywalker]

Thanks VIC and Speedgeek... I'll make the change and since you did this with a GPS and same setup it must be right! I felt like my speedo is reading slow now and would have thought the percentage would have went lower instead of higher.... what do I know... I'm just a shade tree machanic. I'll know this out this evening and very much appreciate it!

 

[Skywalker]

FWIW also checked the odometer with GPS.In 110 miles it was within 1.5 miles.Maybe I should go ahead and add the other percent.

Thanks for the inputs proud dad!

 

[busastrom]

This might have already been taken care of but I had the same issue. No GPS.
I took a stop watch and went at an indicated speed of 70 MPH for about 15 miles. With some number crunching, that gave me how fast I was actually going. So if I was actually going like 63 and it indicated 70, that gave me the percentage to compensate for. It worked great.
Have to run at least 10 miles though because even if you are off your indicated speed a bit, it makes a difference in your final calcs.