Well with the price of gas pushing $1.40 a litter ($5.20 US Gallon) here in the great white north I was thinking about dropping a tooth in the rear. 95+% of my weekly riding is on the slab to and from work (300km /200miles) a day, 4 days a week. I know there would be some fall off on the low end but I'm wondering if the gain in fuel range would be enougth to make me feel better.
If I did want to do some weekend fun stuff, its only about 20mins work to lossen off the rear end and swap out the rear sprocket back to the OEM size.
I guess the question is, am I going to see much of a range increase by just one tooth? Is my 110 link chain now going to be too long, and if I do deside to hot swap between the two sprockets on the odd weekend, am I going to abnormally wear my chain, which in the long run would cost more to replace early then I would ever save in gas?
Any mathematicians out there, that know how much of an engine RPM drop I'd see by going down one tooth in the rear? If its only a hundred or so RPM, I don't think it would be worth it..
A little bit of basic math from
http://www.gearingcommander.com/ it doesn't seem like it's worth it at all.
In 6th gear, at 5250rpm, you're traveling at 123.9km/h with your stock 43 tooth sprocket.
In 6th gear, at 5250rpm, you're travelling at 126.9km/h with your minus-one 42 tooth sprocket.
That's a difference of 3km/h, which if you get 300km a gas tank, you'll get an additional 9km distance.
At $1.40/litre, and 22L gas tank, it costs $30.80 to fill up. That's about $0.1026 cents a kilometer. So you're roughly saving $1 each fill up.
Have you considered going up a tooth on the front sprocket as an alternative? Believe I've read how this would make about as much difference as if you dropped three teeth on the rear sprocket. I could be wrong however. Of course changing the front sprocket may require more time and effort.
A one tooth drop at the rear sprocket would not make enough difference to be worth the $$ and effort-at least for me.
The problem with regearing is you'll probably go by the speedometer anyhow, and just be commuting 3% faster with the new higher gearing.
Maybe buy a CBR250?
[image: View Post]smoothsailin, on 17 April 2012 - 11:29 AM, said:
Have you considered going up a tooth on the front sprocket as an alternative? Believe I've read how this would make about as much difference as if you dropped three teeth on the rear sprocket. I could be wrong however. Of course changing the front sprocket may require more time and effort.
A one tooth drop at the rear sprocket would not make enough difference to be worth the $$ and effort-at least for me.
This is the way to go IMO as it's much cheaper($25) and easier and faster and if your trying to drop hwy rpms a much better choice. BTW a stock 5th gen front sprocket will do the trick.
BR
I went the +1 tooth in the front, an OEM 5th Gen sprocket. I am not worried about the "weekend" blitzing stuff, you can always shift down if needed, but more long distance driving anyway. The plus side is that the speedometer now reads properly according to GPS readings. I believe the RPM difference is about 500 rpms at road going speeds.
So did you see a real improvement in mileage?
"Any" savings would be offset by the cost of the sprocket and the time to put it on. That is my .02 If you wanna worry about gas mileage get a scooter.
[image: View Post]VFR-SPORT, on 17 April 2012 - 02:38 PM, said:
I went the +1 tooth in the front, an OEM 5th Gen sprocket. I am not worried about the "weekend" blitzing stuff, you can always shift down if needed, but more long distance driving anyway. The plus side is that the speedometer now reads properly according to GPS readings. I believe the RPM difference is about 500 rpms at road going speeds.
I'd like to see what it does to the speedo to go one tooth less in the rear(I might do it to get the speedo correct, and I'd like it to be a little taller in 2nd and 1st)>>>>I don't want a speed healer.>>>>Thx any way!
[image: View Post]VFR-SPORT, on 17 April 2012 - 02:38 PM, said:
I went the +1 tooth in the front, an OEM 5th Gen sprocket. I am not worried about the "weekend" blitzing stuff, you can always shift down if needed, but more long distance driving anyway. The plus side is that the speedometer now reads properly according to GPS readings. I believe the RPM difference is about 500 rpms at road going speeds.
Speedo is out about 9km/h at 100km/h hwy speed, so I'm going the same speed but using a fuel flow of 9km/h less, as the engine is turning slower. My VFR will run about 350km to a tank or 3.5 hours of riding. So if my dumb math works that's about 30km extra per tank. Since I fill the bike daily at 4-5 tanks a week if those are real numbers thats 120-150km a week in fuel savings. Bike uses around 5liters for every 100km traveled so that turns in to around 7 liters a week saved or about $10 a week.
if those numbers are real, that could be some real savings, last year I rode around 12,000kms which if all my math works thats over $250 in savings..
This might be something I may have to think about a little harder. Even half that in savings would be worth it..
To take the cost of the sprocket out of the equation wait and change it when you're due a new replacement anyway. (same goes for cars with better gas milage....PER: Clark Howard(radio talk show economist).