FlyB0y Posted June 25, 2005 Share Posted June 25, 2005 Heya all, anyone have a suggestion for a inexpensive GPS that would make an accuate Speedo? I am going to make the conversion to 26.1" tires on my brat and want to avoid having to guess my actual speed with the bigger tires. Thanks Quote Link to comment Share on other sites More sharing options...
subie94 Posted June 25, 2005 Share Posted June 25, 2005 Heya all, anyone have a suggestion for a inexpensive GPS that would make an accuate Speedo? I am going to make the conversion to 26.1" tires on my brat and want to avoid having to guess my actual speed with the bigger tires. Thanks if you go to http://www.tyres1.com and check out the interactive calculators and click on speedometer check.you can find out how much your new tires will throw off you speedo an do what i did,just remember to add that extra mph when you look at the speedo Quote Link to comment Share on other sites More sharing options...
Numbchux Posted June 25, 2005 Share Posted June 25, 2005 I have a Garmin GPS 45 mounted (velcro!!) on my dash for a automatically recalibrating speedo. It's kind of a beast, with a big external antenna, but it works very nicely. it just so happened that my uncle had bought a new one recently and had his old one sitting around, so I managed to get it for free. But try ebay, or a pawn shop, I bet you could find a good deal. After a couple weeks of driving with it, I only find that it's worth waiting for it to start up when I'm making a long freeway trip, I drove with it for awhile, and I've become very used to the adjustment, and don't bother turning it on. Quote Link to comment Share on other sites More sharing options...
Vanislru Posted June 25, 2005 Share Posted June 25, 2005 I used a tire calc. and then put little stickers with the correction on the speedo. Works well and cost me 99 cents for the sticker pack. Quote Link to comment Share on other sites More sharing options...
soobmater Posted June 25, 2005 Share Posted June 25, 2005 I used a tire calc. and then put little stickers with the correction on the speedo. Works well and cost me 99 cents for the sticker pack. that is exactly what i want to do. Thats what a guy in town did with his lifted roo. i just cant find the stickers:-\ Quote Link to comment Share on other sites More sharing options...
calebz Posted June 25, 2005 Share Posted June 25, 2005 I have a magellan 315..Its kinda old, fairly compact and reasonably cheap on ebay. Tire calculators are cool too, but given the differences between manufacturers and the inherent inaccuracy I have found in subaru speedos, I wouldn't really trust them much. Quote Link to comment Share on other sites More sharing options...
FlyB0y Posted June 25, 2005 Author Share Posted June 25, 2005 Lots of great ideas, thx! I looked up a tire calc, but it's not a constant through-out the speed range, at lower speeds it shows a correction of +5 mph, and above 45, it's something closer to +10, so I figured I should just get a GPS that is accurate for a speedo, but otherwise cheap ... gonna check some pawn shops Quote Link to comment Share on other sites More sharing options...
ktperry Posted June 25, 2005 Share Posted June 25, 2005 If you go with the GPS get one that has WAAS technology. Its more accurate. Kevin Quote Link to comment Share on other sites More sharing options...
FlyB0y Posted June 25, 2005 Author Share Posted June 25, 2005 If you go with the GPS get one that has WAAS technology. Its more accurate. Kevin Good to know thx is that something an older GPS I might find at a pawn shop/garage sale or just very recient ones? Quote Link to comment Share on other sites More sharing options...
ktperry Posted June 25, 2005 Share Posted June 25, 2005 If its only two or three years old it may have it, but just about all of the new ones have it. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted June 27, 2005 Share Posted June 27, 2005 Lots of great ideas, thx! I looked up a tire calc, but it's not a constant through-out the speed range, at lower speeds it shows a correction of +5 mph, and above 45, it's something closer to +10, so I figured I should just get a GPS that is accurate for a speedo, but otherwise cheap ... gonna check some pawn shops nope, it's a percentage thing, mines off by almost 20 @ 80! that's why I like my GPS, the prob with that is, the refresh rate makes it a bit tough. Quote Link to comment Share on other sites More sharing options...
RallyJusty Posted June 28, 2005 Share Posted June 28, 2005 The tire calculator shows a variation in speed throughout the range, because the relationship is not linear. The change in speed is releative to the speed , not the tire size, as a result, as the speed increases so does the adjustment. As an example, the average speedo has an inherent error of about plus or minus 5 to 8 percent lets say. Five to eight percent of 5 miles an hour is very small on over-all terms of speed compared to 5 to 8 percent of 80 miles an hour. As for the GPS. It will give speed of travel, and can be very accurate. But it is subject to the constelation and over head obstructions. The speed shown may not always be real time, and maybe based on old data. If you travel 300 yards and in that distance speed up, but the satelites are obscured, it will use data 300 yards old, and give speed calculated on that, and not your current position and speed. Food for thought if you want to avoid real time tickets with not so real time data. You can use the GPS, as well as a stop watch to calibrate your speedo and use the stickers to be accurate all of the time. I have gotten out of a ticket showing my notes for speedo calibration to a highway patrolman. I had done it for every 5 miles an hour up to 80 using 5 mile long baselines and my hp48 calculator. More than anything I think he was impressed that I even cared that my speedo was cranked. Quote Link to comment Share on other sites More sharing options...
Forester_Ranger Posted June 28, 2005 Share Posted June 28, 2005 look at a garmin gps V Quote Link to comment Share on other sites More sharing options...
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