Triumphrat

yipes_stripes

OK. - I am currently running 15/45 (came stock that way) and had to replace my rub strip after 5500 miles. After another 2000 miles, I am well on my way to another replacement. I have seen a few of you go 47 in the back, but, I don't want to replace my chain and was thinking about just upping it one tooth in the front to lift the chain a little higher. Bad idea? Anyone have any opinions? I am all ears...

BombFactory

It depends on what you require from the engine when riding. A 15/45 sprocket gives a 3:1 ratio, while a 16/45 will give you a higher ration at 2.81:1. This means you will have less torque at the rear wheel, and the engine will turn at a slower rpm for the same speed as a 15/45 setup. This may mean you will spend more time in lower gears to get up to speed or when cruising around, but it doesn't hurt anything. You may see slightly better fuel economy if you do a lot of highway riding. Technically speaking, you will be able to hit a higher top speed before bouncing off the rev limiter, but it will take more time and a longer stretch of road to get there than a lower gear ratio (assuming aerodynamics are not overpowering).

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Will

I actually doubt a taller gear ratio (meaning a 16 tooth front sprocket) will get you better fuel mileage. I saw no change going from the stock ratios to shorter gearing, making it unlikely the relatively small change in rpm at any given speed will have a noticeable impact. It's how heavy your right hoof is on the throttle which makes all the difference for fuel economy.

If anything, I would expect the fuel mileage to go down, since you will have to use more throttle at any given speed due to engine's torque curve and the lower engine speed. The other problem you will have going to an even taller setup is bogging off the line. You will have to slip the clutch more, and a slipping clutch isn't a happy clutch.

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Will
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yipes_stripes

Thanks for the replies. Yeah - I guess I will just have to see what I think. Really, the biggest issue I may have is what Will pointed out - when commuting, starting from stop at all the lights, what will it feel like from a complete stop. I will give it a shot and post what I think. If 16/45 is not my think, I will just spring for a new chain and a 47 or 48 rear (16/48 is same ratio as stock).

Bomb Factory and Will - you both contribute a ton here. Thanks!

yipes_stripes

Thought I would report back. I don't have to slip the clutch at all, and my low rpm jerkiness (that annoying drive train lash at ~2500 rpm, or ~20mph) is no longer an annoyance with the new gearing. I actually like it. I do think that when my chain is worn out I will up the rear and run 16-47, but the 16-45 works fine.

Will

Good news. We all learned something. Thank for telling us how your experiment worked.

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Will
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Go soothingly on the grease mud, as there lurks the skid demon.