GPS Speedo

Magician16 · 04-22-2022, 04:53 PM

I've been thinking about putting a new speedo on my Magician. Has anyone ever used a gps speedo. They're great on boats.https://www.ebay.com/itm/334051808621

Ol,fart · 04-22-2022, 11:05 PM

I haven't used one ,only hand held.
They are accurate on level ground, but hills throw them off as far as road speed.
I'm using a zannella digital cluster on my hawk(from ebay) it's accurate, but only when set for a 2 inch smaller front wheel.

Magician16 · 04-23-2022, 08:52 AM

The current speedo is off by about 10%. Guys who have put the Zanella on a bike with the 19" front wheel, like the Magician say it's off by 10%. That's the main reason I'd like a gps speedo. My phone gps reads very accurate, but where I ride I'm not comfortable having my phone out there.

2LZ · 04-23-2022, 01:03 PM

I've never had a bike with an accurate speedo, ever. If it was close to accurate, I changed something to throw it off. Even when I ride past the two CHP signs in my county, at the exact same speeds, both signs show two different speeds.

The problem is the speedos aren't inaccurate at the same rate per speed, usually thanks to cable drive. Some can be close from 0-30 mph, but then as you go faster, it throws further off as you accelerate. It's hard where I live to know exactly how fast you're going because there's no real traffic to speak of, unless I go into town and there's a general flow of traffic.

General rule is though, if it says 50, you're going about 45, give or take.

Ol,fart · 04-23-2022, 01:40 PM

Quote:

Originally Posted by Magician16

The current speedo is off by about 10%. Guys who have put the Zanella on a bike with the 19" front wheel, like the Magician say it's off by 10%. That's the main reason I'd like a gps speedo. My phone gps reads very accurate, but where I ride I'm not comfortable having my phone out there.

The zannella should have a 17inch setting.that should be close to accurate for the 19 inch wheel. I'm using the 19 setting for my 21 inch . It's within 1mph.

Magician16 · 04-23-2022, 05:36 PM

I don't think the Zanella will work. Sending units on the Hawk and Magician are on opposite sides of the hub.

Ol,fart · 04-24-2022, 05:27 AM

Quote:

Originally Posted by Magician16

I don't think the Zanella will work. Sending units on the Hawk and Magician are on opposite sides of the hub.

I don't know, I assume the sending unit is an AC generator. If so turning backwards should not matter,but will it physically fit ???

Magician16 · 04-24-2022, 07:46 AM

After a little research I determined that the Magician has a larger front axle bolt than the Hawk, so it will not fit.

ChillRider · 04-28-2022, 10:15 AM

All factory-fitted speedos have a designed-in error of at least +10 speed units (overestimation) by law -in fact, it's illegal in some jurisdictions to have a speedo underestimate the speed you're moving at. Now, whether that's a constant +10 units in all speed ranges, a maximum value or an average over various speeds, that's another matter.

With a GPS speedo you'll get an accurate -if slightly delayed- reading with no law-imposed overestimate built-in, but as it has already been mentioned they work purely by "ground speed" in aviation parlance -any vertical vector and they'll be off.

The closest you can get to your "true airspeed" is to use an uncertified aftermarket unit (many bicycle speedos would fit the bill, and most can work at the speeds those bikes can reach). They can also be installed together with your existing cluster, if you wish to draw comparisons. Mounting their sensors/magnets can be tricky though -usually, sensors will go on the lower fork leg, and magnets on the disk brake or hub.

Pick your poison :-)

04-22-2022, 04:53 PM	#1
Magician16 Join Date: Aug 2019 Posts: 468	GPS Speedo I've been thinking about putting a new speedo on my Magician. Has anyone ever used a gps speedo. They're great on boats.https://www.ebay.com/itm/334051808621 __________________ 2018 Bashan Storm(sold) 2016 Magician 250
	0

04-22-2022, 11:05 PM	#2
Ol,fart Join Date: Jan 2022 Location: Gatesville Texas Posts: 161	I haven't used one ,only hand held. They are accurate on level ground, but hills throw them off as far as road speed. I'm using a zannella digital cluster on my hawk(from ebay) it's accurate, but only when set for a 2 inch smaller front wheel. __________________ 2021 RPS Hawk "IKEA" (Came in a box with no instructions) 110 main jet 1washer,2.5 sprockets and the cat fell off( with a little help) 1984 Honda V65 Magna "Daddy's Little Monster" To whoever stole my anti-depressants. I Hope Your Happy !
	1

04-23-2022, 08:52 AM	#3
Magician16 Join Date: Aug 2019 Posts: 468	The current speedo is off by about 10%. Guys who have put the Zanella on a bike with the 19" front wheel, like the Magician say it's off by 10%. That's the main reason I'd like a gps speedo. My phone gps reads very accurate, but where I ride I'm not comfortable having my phone out there. __________________ 2018 Bashan Storm(sold) 2016 Magician 250
	0

04-23-2022, 01:03 PM	#4
2LZ Join Date: Mar 2010 Location: Volcano, Ca Posts: 7,094	I've never had a bike with an accurate speedo, ever. If it was close to accurate, I changed something to throw it off. Even when I ride past the two CHP signs in my county, at the exact same speeds, both signs show two different speeds. The problem is the speedos aren't inaccurate at the same rate per speed, usually thanks to cable drive. Some can be close from 0-30 mph, but then as you go faster, it throws further off as you accelerate. It's hard where I live to know exactly how fast you're going because there's no real traffic to speak of, unless I go into town and there's a general flow of traffic. General rule is though, if it says 50, you're going about 45, give or take. __________________ "Light a fire for a man, and you heat him for a day. Light a man on fire, and you heat him for the rest of his life." 2007 Suzuki DRZ400S (SM convert) 2009 Q Link XP 200 1967 BSA B25 250cc Starfire 2022 Royal Enfield Interceptor 650 2023 Royal Enfield Scram 411 1948 Royal Enfield Model G 350
	1

04-23-2022, 05:36 PM	#6
Magician16 Join Date: Aug 2019 Posts: 468	I don't think the Zanella will work. Sending units on the Hawk and Magician are on opposite sides of the hub. __________________ 2018 Bashan Storm(sold) 2016 Magician 250
	0

04-24-2022, 07:46 AM	#8
Magician16 Join Date: Aug 2019 Posts: 468	After a little research I determined that the Magician has a larger front axle bolt than the Hawk, so it will not fit. __________________ 2018 Bashan Storm(sold) 2016 Magician 250
	0

04-28-2022, 10:15 AM	#9
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	All factory-fitted speedos have a designed-in error of at least +10 speed units (overestimation) by law -in fact, it's illegal in some jurisdictions to have a speedo underestimate the speed you're moving at. Now, whether that's a constant +10 units in all speed ranges, a maximum value or an average over various speeds, that's another matter. With a GPS speedo you'll get an accurate -if slightly delayed- reading with no law-imposed overestimate built-in, but as it has already been mentioned they work purely by "ground speed" in aviation parlance -any vertical vector and they'll be off. The closest you can get to your "true airspeed" is to use an uncertified aftermarket unit (many bicycle speedos would fit the bill, and most can work at the speeds those bikes can reach). They can also be installed together with your existing cluster, if you wish to draw comparisons. Mounting their sensors/magnets can be tricky though -usually, sensors will go on the lower fork leg, and magnets on the disk brake or hub. Pick your poison :-)
	0