XF125GY stupid question

**Rodders** · 01-28-2011, 09:50 PM

if you change to a 16T on the front, is there enough movement on the rear axel to allow for it without having to get a longer chain?

Im 6'4 and 16stone, hahaha, so its never gonna be fast. Though i did overtake a bus up a hill today, LOL!!

**jape** · 01-28-2011, 11:00 PM

That is interesting. I should think the adjustment would allow for that but you aren't going to know for sure unless you do it. Is there enough room in the case to do that sprocket change? I know most say a change on the front is better than on the rear but I wonder whether at your weight it may be a very small gain anyway. I reckon that on my bike, a 200cc, I have a small percentage top speed advantage with the rear sprocket change I made but I weigh 15 stone and that absorbs much of the gearing advantage.

I am becoming quite convinced that most of the speed gains people see are when the power-plant to overall weight ratio is better than in our weight range! These small engines just don't have it and gearing doesn't make much difference at the heavy mass end of the scale. You do get some advantage, but a hill or a wind does lose that quickly and most of the difference in my case is a smoothness through the gears, more length in each gear. The bottom end 'slow-down' is noticeable but even with ratio changes of 3.5 down to 2.75 it is not enough to cause problems, that includes off-road on muddy slopes in my experience. It is just a juggle of need and reasons against advantage gained and lost in different areas. I would try it, but a chain isn't that expensive and many here say always change the chain when you change a sprocket.

**Rodders** · 01-29-2011, 04:23 PM

thats why im not too fussed, I know at my weight and being a 125 its never gonna be great. Should have got a 400 or 600cc single, lol, but all costs go up and im trying to get around as cheap as possible.

Though, for a few quid, could be worth a shot. If anything it should improve my mpg as im mostly on the flat, so crusing revs will be lower.