Author Topic: 17" front wheel conversion/speedo gear drive  (Read 149 times)

0 Members and 1 Guest are viewing this topic.

Offline The Dude

  • Training Wheels
  • *
  • Posts: 91
  • AREA: South Central Area
  • COG#: 11820
  • Membership Level: Active
17" front wheel conversion/speedo gear drive
« on: October 12, 2017, 01:10:56 pm »
I converted to 17" wheels, front and back, about 2 years ago.  In the changeover, I installed the recommended speedometer gear drive from a ZX6D.  With this setup, my indicated speed was about 10% lower than actual speed (as shown on my GPS).  This bought me a speeding ticket early on - no big deal, as I knew it was my miscalculation, or lack of any calculation that got me that ticket.  But the speedometer being off has continued to bothered me.

I just got new tires (PR4 front, PR4GT rear), and I decided to reinstall the original speedo gear drive. My reasoning was that it would be better to be reading slightly higher than actual, and I'm not concerned about the odometer showing more miles than is true.

Well, I just took a test drive, and the speedometer matches the GPS almost exactly.  Speedo is just 1MPH higher than what the GPS says! 

How is this possible?  What have other folks in my shoes experienced?  It's as if I got the two gear drives confused and just NOW installed the ZX6D unit.  But I know that I didn't because it was a new unit, whereas my original was well scuffed and dirty!

My understanding is that there is no adjustment procedure available for the speedo itself, aside from the gear drive.  If this is true, why is the ZX6D gear drive recommended?
Past: '84 KZ700, '91 VFR750
Current: '02 CONCOURS (Smooooth Project #3)
Torque cams, 7th gear, SiSF carb treatment, 2MM, free power upgrade, 17" wheels, Sonic 1.1kg with GVEs, Spiegler brake lines.

Offline RWulf

  • Crotch Rocket
  • ****
  • Posts: 1491
  • AREA: North Central Area
  • COG#: 7122
  • Membership Level: Active
Re: 17" front wheel conversion/speedo gear drive
« Reply #1 on: October 12, 2017, 01:31:59 pm »
It's all due to the total circumference of the front tire on the rim.
All tires are somewhat differant, even tire pressure can and does
have an effect.
Speedometer heads can be calibrated to match your tire but it's
not cheap.
Just use your GPS for speed.

Offline Pbfoot

  • Crotch Rocket
  • ****
  • Posts: 1184
  • AREA: South Central Area
  • COG#: 10807
  • Membership Level: Active
Re: 17" front wheel conversion/speedo gear drive
« Reply #2 on: October 12, 2017, 02:14:14 pm »
I used the ZX6D drive and my mph is within 1mph of my GPS. Could you have received the wrong drive or gotten them mixed up?
If you don't have time to do it right, when do you have time to do it over.                                                                17" wheels, Nissin 4 piston calipers.1kg Sonic Springs.Cartridge Fork Emulators. KB Brace. Galfer brake lines  Free power mod.

Offline The Dude

  • Training Wheels
  • *
  • Posts: 91
  • AREA: South Central Area
  • COG#: 11820
  • Membership Level: Active
Re: 17" front wheel conversion/speedo gear drive
« Reply #3 on: October 12, 2017, 02:38:45 pm »
Could you have received the wrong drive or gotten them mixed up?

That seems like the most logical answer to this riddle.  So I can't rule it out.  But like I said, it was easy to see the difference between the two, and I made sure to put one away so I didn't get them mixed, or myself confused.  All's well that ends well, I guess.
Past: '84 KZ700, '91 VFR750
Current: '02 CONCOURS (Smooooth Project #3)
Torque cams, 7th gear, SiSF carb treatment, 2MM, free power upgrade, 17" wheels, Sonic 1.1kg with GVEs, Spiegler brake lines.

Offline Sport Rider

  • Two wheel addict!
  • I Need a Life
  • ******
  • Posts: 6604
  • 100,000 or Bust!
    • BikePics Site
  • AREA: Southeast Area
  • COG#: 8603
  • Membership Level: Asst. Area Director
Re: 17" front wheel conversion/speedo gear drive
« Reply #4 on: October 12, 2017, 03:00:51 pm »
I used my original one along with my ZRX front end/wheel.  it's pretty much spot on with the GPS.
North Carolina AAD
COG, VROC, VBA, IBA, USCA and other TLAs
05 C10, 94 C10, 06 Nomad, 15 CB
https://www.bikepics.com/members/ncdave/

Offline Bob_C_CT

  • Crotch Rocket
  • ****
  • Posts: 1859
  • AREA: Northeast Area
  • COG#: 9544
  • Membership Level: Active
Re: 17" front wheel conversion/speedo gear drive
« Reply #5 on: October 12, 2017, 06:51:54 pm »
^ Ditto
97 C10,ZRX Front, Meanie Rear

Offline Jim Snyder

  • Crotch Rocket
  • ****
  • Posts: 1165
  • The Connie Rocks !!!
  • AREA: South Central Area
  • COG#: 7055
  • Membership Level: Asst. Area Director
Re: 17" front wheel conversion/speedo gear drive
« Reply #6 on: October 12, 2017, 07:00:50 pm »
I discovered that the ZX6 gear drive was not the only choice as well.  When I did my conversion I used a ZR7 front wheel. The wheel came with the axle and Speedo drive from the ZR7. It worked fine, speed was within 1 mph. Not sure how the "ZX6 only thing got started but it's not the only choice available.
"Some days you're the windshield, and some days you're the bug" Get used to it cause thats life !!!