SuzukiSavage.com - Speedometer

emeraldcopnj YaBB Newbies Offline SuzukiSavage.com Rocks! Posts: 10 New Jersey Gender:	Speedometer 09/24/14 at 08:32:34 I am looking to do a mini speedo on my bobber project. What ratio would I need? Thanks !
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mpescatori Serious Thumper Offline Romanum Thumperium Cavalco, yeaaah !!! Posts: 3547 Rome, Italy Gender:	Re: Speedometer Reply #1 - 09/25/14 at 01:27:22 +1 I need to know myself. Many aftermarket speedos are geared for anything from the ubiquitous harley Sportster to "younameit" but I have obviously shoppet at "Murphy's", 2 speedos, 2 diferent ratios, still reads wrong...
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Speedometer Reply #2 - 09/25/14 at 02:01:59 So,knowing those ratios,which way and how much,,bingo..
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PinkHelmet YaBB Newbies Offline SuzukiSavage.com Rocks! Posts: 16 Mangalia, Romania, Europe. Gender:	Re: Speedometer Reply #3 - 09/25/14 at 02:19:43 see if you can find anything from here: http://suzukisavage.com/cgi-bin/YaBB.pl?num=1345772898
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Re: Speedometer
Reply #4 - 09/25/14 at 05:18:22

There is a ratio for this.This is in the Dime City info:

60MPH @ 2240RPM...This is based on a Harley engine though,so don't be alarmed.

Here is one on Flea bay.

http://www.ebay.com/itm/New-Small-Drag-Specialties-Speedometer-2-1-2-Custom-C...

I run a 2:1 but I think it might be off.I also run a 150/90 rear tire. I have been thinking about getting this ratio and comparing.

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Arnold Serious Thumper Offline The dude abides... Posts: 896 Westchester, NY Gender:	Re: Speedometer Reply #5 - 09/25/14 at 06:07:04 I have a 2:1 also, seems fairly accurate enough next to the side road speed radars.
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Kris01 Serious Thumper Offline Eat, sleep, RIDE! Posts: 3767 Tennessee Gender:	Re: Speedometer Reply #6 - 09/25/14 at 18:28:17 2240:60 means the speedo cable must spin 2240 times for the gauge to read 60 mph. Stock 140/80-15 = 74.829" circumference 846.731 rpms (of the tire) at 60 mph 2240/846.731 = 2.645 The stock speedo has a ratio of 2.645:1. I doubt the 2:1 ratio speedo is anywhere close to being accurate.
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Re: Speedometer
Reply #7 - 09/26/14 at 03:16:29

Kris01 wrote on 09/25/14 at 18:28:17:

2240:60 means the speedo cable must spin 2240 times for the gauge to read 60 mph.

Stock 140/80-15 = 74.829" circumference
846.731 rpms (of the tire) at 60 mph
2240/846.731 = 2.645

The stock speedo has a ratio of 2.645:1. I doubt the 2:1 ratio speedo is anywhere close to being accurate.

Sorry, I don't agree.

2240/60 means an assumed 2240rpm (turns per minute) to read 60 mph.

By your own calculations, the Savage needs:
- 846.73 revolutions of the tire
- multiplied by 2.94 (belt drive ratio)
to read the same speed.

846.73 x 2.94 = 2489/60 (let's round this off to 2490/60 or even 2500/60)

So a 2240/60 speedo should read 2490/2240 = 1.11 11% faster than you are actually going.

The sppedo I fitted reads 10% slower than I am actually going, even though I now have a 2.88:1 chain drive and a 150/90x15 rear tire.

Had I a stock bike, it'd be reading 15% slower !!!

Explain THAT to a cop !!! Lips Sealed

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Re: Speedometer
Reply #8 - 09/26/14 at 04:42:07

Mechanical speedometers are so........yesterday! Roll Eyes

There are a whole new batch of electronic speedometers that not only offer the ability to get accurate speed information, you can get accurate odometer readings, trip odometer(s), engine and ambient air temperatures, time logs, altitude readings, turn signal and high beam indicators, shift and engine red line lights, etc. They are not too hard to install, and as time passes they are getting more affordable Entry level one are about $ 200 to install and some really fancy ones go for over $ 400. Some of the more recent ones even have conventional looking cases and swing needles for the tachometer. If accuracy is important and and money issue are not.....the GPS ones are really nice.

A few years ago all the electronic speedometers looked like lab equipment and did not look good on a bike - but the new ones look more like gauges we are used to seeing on motorcycles.

The fact is that s $ 60 mechanical speedometer is not going to read accurately on the wide range of bikes....maybe once in a while someone will get lucky and have the right gear ratio and tires size and it will read close enough.....and if you are building a simple bobber/rat bike and want a small speedo to check speed once in a while....they might read close enough. But if you want something useful and do a lot of riding.....by the time you buy a mechanical speedo, tach, and the cable to get them to work on the Savage - you will have spent about as much as an entry lever electronic speedo/tach will cost.

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Kris01 Serious Thumper Offline Eat, sleep, RIDE! Posts: 3767 Tennessee Gender:	Re: Speedometer Reply #9 - 09/26/14 at 18:18:30 Mpescatori: Check your calculations. That 846 tire revolutions per minute at 60 mph will have nothing to do with gearing. You can gear the bike anyway you want and you will still spin the tire the same exact RPM at 60 mph. Remember, we are talking about tire rpms, not engine rpms. Obviously regearing will affect engine rpms.
Back to top	There's no problem that a full tank of gas and a sunny day can't fix! 2008 S40, Rotella T 15W-40 w/ZDDP added, Dyna, 140/90-15, Battery Tender Jr., Seat lift, #52.5/150/3 washers, Raptor IP Logged

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Re: Speedometer
Reply #10 - 09/26/14 at 18:31:21

Kris01 wrote on 09/26/14 at 18:18:30:

Mpescatori:
Check your calculations. That 846 tire revolutions per minute at 60 mph will have nothing to do with gearing. You can gear the bike anyway you want and you will still spin the tire the same exact RPM at 60 mph.

Remember, we are talking about tire rpms, not engine rpms. Obviously regearing will affect engine rpms.

The reason that gearing affects our speedometer - is that the cable that drives the speedometer is driven from the transmission output shaft. Therefore when you change the gearing by changing the front or rear pulley/sprocket size...you change the number of revolutions of the rear wheel in comparison to the output shaft revolutions. That (and rear wheel spin) is one reason a lot of motorcycles use the front wheel to drive the speedometer.

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Kris01 Serious Thumper Offline Eat, sleep, RIDE! Posts: 3767 Tennessee Gender:	Re: Speedometer Reply #11 - 09/26/14 at 18:49:37 Correct
Back to top	There's no problem that a full tank of gas and a sunny day can't fix! 2008 S40, Rotella T 15W-40 w/ZDDP added, Dyna, 140/90-15, Battery Tender Jr., Seat lift, #52.5/150/3 washers, Raptor IP Logged

verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 28886 L.A. California Gender:	Re: Speedometer Reply #12 - 09/26/14 at 19:35:06 AND... neither one of you have accounted for the worm drive in the speedo gear.
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ToesNose Serious Thumper Offline Pardon me, do you have Hot Sauce? Posts: 1993 Mooresville, NC Gender:	Re: Speedometer Reply #13 - 09/27/14 at 13:59:55 I got the 60MPH @ 2240RPM one from Dime City along with a tach cable from the 73-77 GT550 and it corrected my speedo.
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Re: Speedometer
Reply #14 - 09/28/14 at 18:22:57

This is only slightly off topic. Yesterday I saw a 1948 HRD...which later got the name Vincent. This was a Rapide, kind of the early model Black Shadow. (I may have some of that wrong....but that is the was I remember it being told to me). Anyhow....this is a speedometer and headlight set up that I believe looks really nice (no tach).

So.....I am tempted to look at electronic speedos with the tach integrated....to look a bit like this HRD.

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