180 mph on speedo is only around 155mph ...
13.9% error...I don't think so..seems a little excessive. Before I changed the gearing and tire, I was at about 8% error.
150 on the speedo....... was 143 on the Lidar
4.7% error...more like it...maybe a little low.
i don't have faith in gps readings no more .. i don't think they are reliable for mph no more.. reason being 3 of us were at the race track and our GPS were not matching the ticket mph on run ticket .. i know your gonna say bad clock ..but i was running my 125 mph 1/8 mile passes the other guys were on their mph ..but gps was off by 20 to 40 mph lower .
I had my shift light set at 10k, and I saw it blinking, must have been a few ticks over 10k when I let off. (? tach accuracy)
According to http://www.gearingcommander.com with 16/43 gearing and a 55 series rear tire I should have been at about 175.
I have a speedohealer set at about -12.5% to compensate for the gearing, tire size & speedo error.
Speedo & gps are dead nuts @ 60 & 100, when I hold it steady for several seconds and have time to look.
Speedohealer Recall & GPS - Same Run
If you goggle "gps latency", you'll find a lot articles addressing this. Basically, the time(delay) it takes the signals to travel to & from the satellites. This can be significant depending on conditions, terrain and how many satellites your locked on to.
The gps uses previously gathered info to calculate present info. At 175 your moving roughly 250 ft/second. The gps only updates once per second and latency can be +1 second. If you run up to a high speed and slow down quickly, I don't think the gps sees it. You need to hold that speed for several seconds at least, for the calculations to average out.
Just my $0.02
Anybody else with a speedohealer and gps notice this
Let's see some pics of those runs on your gps or speedohealer recall
I'm not trying to be an a$$, it just helps eliminate the "I did this", "your full of crap" responses.
Chris
* Last updated by: CycleJunkie on 5/29/2009 @ 12:55 PM *
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