Speedometer discrepency queshun
 

OK, So debut ride for the Phoenix Project was yesterday. Seat of the pants says about 55-60, and the clock says70 to 75. My buddy was riding my old GSXR and he said I was doing 70 most of the time, but it felt slower.
The GSXR is probably inaccurate, and the hawk has a 15/43 set on it.
So, What is norm for this bike w/ the stock gears or the 15/43?
Respondents will be awarded free ice cream at the poor farmers country store in Meadows of Dan Va.
Thanks, Rob

I figure the 15/43 sprockets lower the effective gearing by about 11%. Indicated 70mph. with 15/43 would be about 63 mph. with the stock sprockets.

The stock VTRs were reported by magazine testers to have spot on speedos at indicated 60 mph. Don't know if that held for other speeds.

Well that is a bit of a news flash to me! I'm always counting on the speedo reading high whereever I ride. 60mph feels like 30 on these things, and I tend to ride alittle "spirited" whereever I go!:eek:

I've got stock sprockets & according to GPS & local radar mine reads about 3mph higher than actual speed at 60mph.

I put the 15/43 gears on and a speedohealer. Checked with GPS and right on. Speedohealer is worth the money. Easy to install. Good luck

I think you're off a little bit 15\43 is a little over a 15% change. I run a 16\43 and my set up is right at 10% off but then YMMV :cool:

I'll admit I don't know exactly how the speedohealer works because I don't have one yet. this winter I'm planning on doing a 520 conversion w/ 15/43 gearing and a speedohealer. I'm just wondering where you set yours to be spot on with your GPS since I don't have easy access to a GPS to check mine. Thanks.

Here's how I figure it;

One tooth out of 16 = 6.25% up front.

2 teeth out of 41 = 4.878% at rear.

6.25% + 4.878% =11.128%

To expand on my post #8, I think it through this way;

When you go minus one on the 16 tooth front sprocket, you are increasing engine speed at any given road speed by 1/16th right? 1/16th expressed as a percentage is (100 divided by 16) is 6.25% increase in rpm.

Each tooth up on the 41 rear is a 1/41st increase in rpm, or (100 divided by 41) = a 2.439% increase in rpm. Two teeth up is (2.439 X 2) = a 4.878% increase in rpm.

Total increase in engine rpm at given road speed with 15/43 sprockets is (6.25 + 4.878) 11.128%

The VTR with stock sprockets turns 3100 rpm at 60mph in 6th gear.

A VTR with 15/43 would be showing 3500 rpm in 6th at 60mph.