Assume I have an accurate speedometer and mileometer. If I fit a larger diameter front wheel, the speedo shows a lower mph reading......... .....so.......... ......would the mileometer show less miles than before?.......... I assume it would so, if the smaller front wheel meant mileometer was accurate over a 100mile distance say, and it read 100 miles.......... ..........would the larger front wheel mean that it would show less than 100 miles covered?? Or, conversely, when the mileometer indicates 100 miles, have I actually covered less then 100 or more?? AL
The laws of physics can never be quantifiedly denied by the counterclockwise rotational forces exerted ,when laid down in a straight line, however P.J's law of bollocks state "the over exertion of liquid grey matter is not to be reasoned or dismissed by somebody/one who has no qualifications other than googlisation at his behest .
Hi. If you have a front wheel speed sensor then yes, larger diameter wheel will mean the speedo shows less speed and lower mileage for the same actual speed and distance as the original wheel. If however your speed sensor is off the gearbox or front sprocket then it wont make a bit of difference. But changing sprocket size would bugger it all up completely.
Thanks......Yep, front wheel speedo drive........and a faulty fuel level sensor, so I do the 100 mile tripmeter thingy......... I have changed from the 60 profile tyre to the 70 profile tyre which actually makes at least 20mm more in diameter. (an aside is that with the 750 and 900 Carb SS; the 750 has a 60 profile and the 900 a 70 profile) The OEM speedo (used for both 750 & 900) which I always thought was quite ambitious at 30mph when using the 60 profile, is now dead-on at 30mph when using the 70 profile. So.....bearing in mind I use the tripmeter as my fuel gauge, I have been wondering whether I should fill up at 80 miles or 120 miles!! AL
Ah right, well the profile is actually a percentage of the width, not a specific height. So a 120/60 would be 72mm high, and a 120/70 would be 84mm high. But these numbers are just a guide and don't relate much to reality. Indeed no two manufacturers making the same size tyre will have the same rolling circumference so it's all bollocks really. I had trouble with my 748 tank sensor. Short term, when i was getting low, i had a mate ride with me with a full tank and some hose pipe. When i ran dry, 136miles! i just sucked some fuel from my mates bike and went a petrol station. Long term, i pulled the pump unit out the tank, found the sensor, which was just a float in a tube with a small hole in the top and bottom, gave it a clean, blew some crap out the lower hole and it worked fine after that. I'm guessing the fuel wasn't leaving the sensor tube due to the blocked hole so kept thinking it was full.
Back to the beginning, with the larger diameter wheel you would defiantly cover a greater distance when showing 100 miles on the trip meter, but would it be enough to make much difference ? Steve
Al, you can use Pi x D to work out the circumference of the tyres which is the distance you travel for one rotation of the wheel. Therefore assuming you have a 17 inch rim (if not replace 17 with whatever wheel size you have) (17” x 25.4 + (72 x 2)) x 3.142 = 575.8mm/revolution (17” x 25.4 + (84 x 2)) x 3.142 = 599.8mm/revolution For any mathematicians the extra brackets are added to ensure the correct order of operation by us non mathematicians Or the higher profile tyre will make the speedo read 4% less than it did before and probably make it more accurate. FWIW Tyre wear can easily make a bike speedo lose 2% over the life of a tyre
Thanks all....I can't be a*sed to sod about with the fuel level sensor, so I will stick to the 100 miles trip meter trick..........but I'll fill up at say, 90 because I will have gone further than 100...........or will I.......... AL
LOL. Yes, you will have travelled further. To simplify things. Imagine the orignal front tyre circumference was 1 mile, (big i know), but one rotation would turn the speedo drive one revolution and show 1 mile on the odometer. So now you increase the tyre size, keeping it simple, to 2 miles circumference. Now one rotation of the wheel will take you 2 miles, but your speedo drive will still only turn once, so odometer would still only show 1 mile. What bike is it actually for? You can always check what you put in the tank against what it's supposed to hold. 100 miles might only be using 3/4 of a tank anyway.
See? I knew I was right to fill up earlier...............The bike is a carb 750SS........their sensors pack up even if they are new, so I'm buggered if I'm going to wrestle with a rubber doughnut for a couple of hours only for it to pack up again next week. AL
Al, I say you need to fill up at 96 miles if that makes the maths any easier, try it and see if you get the same number of litres as before.
Ok. Well been having a quick look on the interweb. Looks like you should have a 17 litre tank, and be good for 140 odd miles to a tank. Might want to do your own research but next time you fill up, keep a note of how many miles you've done since last fill up. Divide the mileage by the litres used and you get miles per litre, sorry if this bit basic. Check how much your tank should hold in your manual or ducati dealers, then multiply the litres in the tank by your miles per litre. Should give you a better guide to how far to travel before you start the find a petrol station panic. I ride a TL1000 on the road every day which does about 80 miles before fuel light goes mad. Makes long rides something to plan rather than enjoy cos i hate stopping for fuel.
