GPS speedometers
Thread Starter
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
GPS speedometers
I'm not saying that this is the best option. I really wanted a 200 mph. But I have two rear ends ratios and I kind of gave up on calibrating. I was always used the tach and a small printed card from the calculations of RPM, Tire diameter, Gear ratio, and rear end ratio. Because as is my 4.11 rear reads 140 on the factory speedo and it is actually going 154 mph on a GPS. My 3.55 with a change of gear teeth in the TKO600 was closer 134 at an indicated 140 mph. Out at the track with 3.55 it was wrapped clear around past 140 and the radar gun was 156 mph before braking for a 40 ish mph turn
GPS speedos are the best alternative.
GPS speedos are the best alternative.
Last edited by gkull; Apr 2, 2019 at 01:31 PM.
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Out at the track with 3.55 it was wrapped clear around past 140 and the radar gun was 156 mph before braking for a 40 ish mph turn
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
George... this is the way to do it... I did not do GPS as it is not as fast at updating speed...
This unit is programable
https://www.corvetteforum.com/forums...ight-70-a.html
This unit is programable
https://www.corvetteforum.com/forums...ight-70-a.html
Thread Starter
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I have front GT1 wilwood brakes. aluminum hat type 13.10 X 1.25 width big SQ inch calipers for heavy lapping cars. I was kinda stupid at first and I was using an Wilwood "H" compound pads and a set of front rotors was destroyed about every 2- 3 hours of track time. but I was also trying to see if I could fail them. The H you have to take off riding the brakes to get them to work. Then you get glowing rotors coming into every turn even with my big air ducting. That's about two weekends of SCCA racing.
the pads were fine and the rotors were gone. So I finally arrived on Wilwood BP-20 pads. and now the pads are two sets to a rotor replacement. rotors last probably 12 hours of track time and you have less front lockups on the unweighted side rolling into a turn. Set of slicks was about every two day event. the saving grace was winning the championship and getting the next years free slicks sponsorship from TireRack. If you keep winning tires are free and all you have to do is run their stickers across your front window.
https://www.wilwood.com/BrakePads/Br...compound=BP-20
https://www.wilwood.com/BrakePads/Br...PolyMatrix%20H
the pads were fine and the rotors were gone. So I finally arrived on Wilwood BP-20 pads. and now the pads are two sets to a rotor replacement. rotors last probably 12 hours of track time and you have less front lockups on the unweighted side rolling into a turn. Set of slicks was about every two day event. the saving grace was winning the championship and getting the next years free slicks sponsorship from TireRack. If you keep winning tires are free and all you have to do is run their stickers across your front window.
https://www.wilwood.com/BrakePads/Br...compound=BP-20
https://www.wilwood.com/BrakePads/Br...PolyMatrix%20H
Thread Starter
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Thread Starter
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Paul this seems to keep up on pretty well. Where did all the years go. I'm going to be a 20 year CF member in a few days?
https://www.speedhut.com/gauge/GR338...dometer-160mph
https://www.speedhut.com/gauge/GR338...dometer-160mph
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Paul this seems to keep up on pretty well. Where did all the years go. I'm going to be a 20 year CF member in a few days?
https://www.speedhut.com/gauge/GR338...dometer-160mph
https://www.speedhut.com/gauge/GR338...dometer-160mph
I'm only a year or so behind you... all it means is were old.. lol.. Oxana and I are having another baby... didn't see that one coming.. lol..
next time I'm up in Vegas we need to meet up at the raceway there.. never been on that track, but have seen it from the road.. looks nice.. Well see what Baby can do, see if she can keep up with you:-)
putting on the inverse trailing arms in a few week,, they have been in the garage for a few months.. look forward to the increases of speeds in the corners..
going out of the last turn at willow it like that150... then smack down to 40,,,, it killer!! :-).
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Burning Brakes
Joined: Apr 2013
Posts: 1,194
Likes: 109
From: Las Vegas NV
I have a full speedhut gauge set with the GPS speedo. Works great. You guys talking about how it doesn't keep up must have much faster cards than mine because it keeps up fine for me. I'm under 400hp.
it does drop down to zero when going through tunnels and on occasion doesn't start reading a speed for a minute or so after being parked indoors for an extended period of time.
it does drop down to zero when going through tunnels and on occasion doesn't start reading a speed for a minute or so after being parked indoors for an extended period of time.
Race Director
Joined: Mar 2017
Posts: 11,840
Likes: 4,457
From: Virginia
The GPS does some complex math, so better receivers are faster. I have a bench top Arduino based unit that has a remote antenna and will do updates at 2 Hz, display to an LED array, and (when I get one) drive a square wave for a digital speedo. I'll try again with a Teensy to see if I can get a better update rate. I think my total investment was about $100- so far. 2Hz is fine for me. I need to 3D print an enclosure, but it will replace one of the center dash vents.
There are $1000- units out there, too. Jeremy Clarkson used on of these on the Grand Tour.
http://www.racelogic.co.uk/index.php/us/
There are $1000- units out there, too. Jeremy Clarkson used on of these on the Grand Tour.
http://www.racelogic.co.uk/index.php/us/
Last edited by Bikespace; Apr 3, 2019 at 09:37 AM.