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Discussion Starter · #1 ·
Seen much on rear tire width, not on overall diameter. I would think a 260 should be slightly larger circumfirence, upping final gearing SLIGHTLY & getting speedo' closer to true reading.Anyone delved into such deep matters? Tried 'search', not there. Don't really care for about 3500-4000 miles, but THEN I gotz to know!P.S. This bike & this board, I am TOTALLY ''ATE-UP'' with!( Could'nt be happier)! :D :bigthumbsup: :hot: :2cool:
 

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zookmon said:
Seen much on rear tire width, not on overall diameter. I would think a 260 should be slightly larger circumfirence, upping final gearing SLIGHTLY & getting speedo' closer to true reading.Anyone delved into such deep matters? Tried 'search', not there. Don't really care for about 3500-4000 miles, but THEN I gotz to know!P.S. This bike & this board, I am TOTALLY ''ATE-UP'' with!( Could'nt be happier)! :D :bigthumbsup: :hot: :2cool:
The 109 uses a pulse pickup sensor located on the "Secondary Gear Case" which sends a signal to the ECM/Speedometer. Although the tire may have some very small impact on velocity of the bike, it has no impact on the indicated speed. If you raise the bike completely off the ground and ran it through the gears you will still have a speed indicated/registering on the speedometer! You will find the info on tire diameters at each tire manufacturers WEB. I believe that all the 40 series tires are within 1/8 to 3/8 inches in total diameter. Additionally the 109 speedo has a error of approximately 5-6 mph...indicated speed 65 mph, actual speed 59/60 mph.
 

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Discussion Starter · #3 ·
I know off the ground, it'll still show speed,all trans& final-drive based vehicle speedo pick-ups will. Go to extremes; a 30''diameter wheel/tire compared to a 10'' will definetly show different speedometer readings in relation to actual road speed. I was hoping SOMEONE who used a larger tire may have observed a tweak in speedo' accuracy. It HAS to on ground, even if minor.I'm not trying to be a  :edit:  head, just thought might see 2-3 mph closer w/ a260. :dontknow:
 

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bob109 said:
The 109 uses a pulse pickup sensor located on the "Secondary Gear Case" which sends a signal to the ECM/Speedometer. Although the tire may have some very small impact on velocity of the bike, it has no impact on the indicated speed. If you raise the bike completely off the ground and ran it through the gears you will still have a speed indicated/registering on the speedometer! You will find the info on tire diameters at each tire manufacturers WEB. I believe that all the 40 series tires are within 1/8 to 3/8 inches in total diameter. Additionally the 109 speedo has a error of approximately 5-6 mph...indicated speed 65 mph, actual speed 59/60 mph.
Of course it will still show a speed. The question is weather it will change your "actual" speed while on the ground. In which case it will change it, however I'm no genius so I couldn't tell you how much. :dontknow:
 

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Discussion Starter · #5 ·
I know we can't 'guess' this answer, but with ALL the informatin we have cumulatively, I ''imagined'' one of us crazed 109'ers would've installed a larger tire, maybe passed a "SPEED-YOUR SPEED'' apparratis, & noticed his speedometer a little closer to actual. Or I got an overactive imagination. Maybe the difference is imperceptible, I'll check 'er when my 260 goes on. Bustin' out laughin' at 7000+ shifts, this wonderment & ALL other ''schtuff'' in the world evaporate FAST, anyway.What a machine!  :bow: :bigthumbsup:
 

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well a couple of week ends ago I took my first ride on the new 260 and when I got on the freeway and it seeemed to show a slower speed at the normal flow speed of trafic 75 vs 80.
 

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bob109 said:
Additionally the 109 speedo has a error of approximately 5-6 mph...indicated speed 65 mph, actual speed 59/60 mph.
It's actually not a fixed 5-6mph error, but instead a percentage of indicated speed. It's somewhere around 8% off... meaning the faster you go, the bigger the mph difference. It's only 5-6mph off at 60mph or so.... If you go to an indicated 145mph, the error is around 11mph making your actual speed about 134. :bigthumbsup:
 

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Joshua_109 said:
Of course it will still show a speed. The question is weather it will change your "actual" speed while on the ground. In which case it will change it, however I'm no genius so I couldn't tell you how much. :dontknow:
"Actual speed"......."Velocity the bike is traveling" are one in the same :bigthumbsup: :bigthumbsup: With the small variations in diameters of 40 and 35 series tires the difference in speed would be almost negligible :bigthumbsup: There is definitely a change....the larger the tire the faster the actual speed/velocity.....the smaller the tire the slower the speed/velocity produced for each revolution of the tire with the assumption rearend gear ratios remain same.
 

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Is the second number on a tire size the % of the width?? Not certain on this but I think I read it somewhere...

In other words a 260x35 has a 260mm width and the sidewall is 35% of that, or 91mm??
Then a 240x40 would be 240mm x 96mm  :dontknow: If this is the case  then it would appear they are pretty close in diameter.
 
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