Error is not linear. More mph is more % error. I’ve seen this on a dyno with no tire slip. Dyno mph and rpm correlated directly, speedo got worse as mph increased.
Would that mean the tire is ‘growing’?
Error is not linear. More mph is more % error. I’ve seen this on a dyno with no tire slip. Dyno mph and rpm correlated directly, speedo got worse as mph increased.
From memory it was something like 8% at 70 and 13% at 150 mph. Both over reporting speed.Is there a relationship to that error? Does the speedo consistently UNDER-report actual speed, or is the error nonlinear in the sense that it can both under and over report actual speeds?
It means it didn’t grow radially on the drum. Dyno speed vs engine rpm was a straight line. Speedo vs dyno mph error was not linear.Would that mean the tire is ‘growing’?
Thanks for that clarification. I'll just have to keep under 150 ... for nowFrom memory it was something like 8% at 70 and 13% at 150 mph. Both over reporting speed.
I learn something new everyday. I was under the impression the Busa read off the counter shaft sprocket....then again, you have to consider tire wear too. That throws off the speedo too at least if the speed is read off the sprocket or the wheel. The busa doesn't read off the sprocket or the wheel so I so don't know how or if tire wear or expansion effect the speedo.
Actually,the 1-20 error,can only be applied once,and its not a percentage. The satellites could still be inaccurate on any distance thou. First pinpointed on one side of the street you could then walk to the other side and GPS could pinpoint you being 1-20 feet from the actual spot. Same margin for error if point A was Los Angeles and point B was New York.Say for instance you ran your speed test over a mile.5,280 feet. Your variable then becomes 264 feet according to the U.S. military.
Meh....IDK.
Rubb.
I learn something new everyday. I was under the impression the Busa read off the counter shaft sprocket.
Rubb.
Actually,the 1-20 error,can only be applied once,and its not a percentage. The satellites could still be inaccurate on any distance thou. First pinpointed on one side of the street you could then walk to the other side and GPS could pinpoint you being 1-20 feet from the actual spot. Same margin for error if point A was Los Angeles and point B was New York.
O well. Somebody who is actually smart would have to work out how it works for speed.1320 ft in a 1/4 mile.Satellite could mark you having traveled 1300 or 1340 ft.
Rubb.
To riders and street racers like us...Yer right,who cares. I got chatting with a physics guru buddy of mine,thats why I looked into all aspects of it.Apparently, the speed sensor is bolted to the end of the countershaft sprocket so it would be effected by tire size. Come to think of it, any speed sensor would be effected by tire size/wear No matter what it reads off of. Thats what I said earlier about the countershaft sprocket,U disagreed,I didn't wanna be rude. Weird huh. LOL. Its where u plug in a speedo healer.
Ti Sprocket Nut--Possible? | Busa Mods
I had planned to draw up a CAD file of an OEM countershaft sprocket nut and submit it to emachineshop.com. I'd like the nut to be made from Ti steel to drop a little weight. I did some research and found info indicating that Ti is nonmagnetic or "paramagnetic" at best. If so, Ti is not going...www.hayabusa.org
About analog gauges v digital, yes, the needle is not as exact as a digital display. I still prefer analog for a quick glance and that's the kind of glance I normally do when looking at the instruments.
Totally.
If this 1-20 foot formula is to compensate for variation off of a straight line, I assume a straight road is perfectly straight if they had some civil engineers out there with transits. Asphalt is too expensive to not have a perfectly straight road if a straight road is what they intend to build. Hopefully you don't vary more than 10 feet when you're doing 190 on a straight road!
Nothing to do with a straight line. It's earth physics stuff.
We're talking about splitting hairs with a few feet variation off of a straight line. They can't tell the exact speed of a fighter jet if they're that particular about it.
I just used a speedo app on my 2017, and it is stock. The speedometer is dead on at 30 mph. At 65 mph the bike reports 5-6 mph fast. I hate calibrated instruments that do not work correctly, how counterproductive. Bah.
I don't know what tire size is recommended to replace the stock 180. If it's a 190, that will just about correct your speedo for normal street speed...at least until it wears down a bit.I just used a speedo app on my 2017, and it is stock. The speedometer is dead on at 30 mph. At 65 mph the bike reports 5-6 mph fast. I hate calibrated instruments that do not work correctly, how counterproductive. Bah.
180 or 190 would be no difference in speed/speedo reading. On reading tire size the 180 or 190 relates to the tire width. No change in speed or speedo reading. The Gen II busa sports(stock) a 190/50R17 . The "50" is the height of the tire. Going from that stock size to a 190/55R17 would affect speed and speedo reading.The difference in tire height(depending on tire brand as well) is about 8MM approx. So if I got out my calculator you get a difference of 2.5% meaning the 55 would be going faster 2.5% faster than indicated by the speedometer. And of course also increasing the Busa top speed,but again not actual speed exhibited.I don't know what tire size is recommended to replace the stock 180. If it's a 190, that will just about correct your speedo for normal street speed...at least until it wears down a bit.
180 or 190 would be no difference in speed/speedo reading. On reading tire size the 180 or 190 relates to the tire width. No change in speed or speedo reading. The Gen II busa sports(stock) a 190/50R17 . The "50" is the height of the tire. Going from that stock size to a 190/55R17 would affect speed and speedo reading.The difference in tire height(depending on tire brand as well) is about 8MM approx. So if I got out my calculator you get a difference of 2.5% meaning the 55 would be going faster 2.5% faster than indicated by the speedometer. And of course also increasing the Busa top speed,but again not actual speed exhibited.
A whole can of worms could be opened discussing the pro's/con's of changing tire size from stock. A lot of riders change to a bigger tire claiming better traction and/or handling. If you consider the physics and physical characteristics of a tires profile ie width X height X contact patch X useable sidewall etc. you get a great debate.
This is fun. I'm gonna add you to that following thingy a mijig feature.You got me again, Rubb. Thanks for the correction. Going from a 50 aspect ratio to a 55 should pretty much correct the speedo---the tire is larger in diameter on center. I've never checked my busa but a 55 on my ZX-14 seems to correct that speedo by comparing to speed of other traffic. I think the tire width can also contribute to height. If the rim is meant to have a 180 on it and you put a 190 on it, that's 10 mm of extra width that has to get squashed between the bead surfaces of the rim. If the width gets squashed, it probably causes the height to increase a little.
180 or 190 would be no difference in speed/speedo reading. The "50" is the height of the tire.
I think the tire width can also contribute to height. If the rim is meant to have a 180 on it and you put a 190 on it, that's 10 mm of extra width that has to get squashed between the bead surfaces of the rim. If the width gets squashed, it probably causes the height to increase a little.