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72 CT70 Lifan Build
- Thread starter wsurf4me
- Start date
I suggest ordering 16 & 17t C/S sprockets and a 35t for the wheel. The bigger C/S sprockets extend chain life and add swingarm-to-chain clearance. If it turns out that 17/35 is still too short, the next step would 33t out back...and you'll already have 15,16 & 17t cogs to test.
Optimal gearing will give somewhere close to 55mph @ 8000rpm, maybe a little more. Any less, the gearing is shorter than it needs to be and that's not a good thing.
Optimal gearing will give somewhere close to 55mph @ 8000rpm, maybe a little more. Any less, the gearing is shorter than it needs to be and that's not a good thing.
IMO, a road bike should be geared as tall as is practical. Seemingly tiny differences in final drive ratio have bigger effects than you might realize...for the moment. A 1-tooth change at the countershaft sprocket might translate to 400-500rpm difference, at 50mph+. If you're out there, enjoying some breeze and accumulating road mileage, higher-than-optimal rpm will really get on your nerves. Consider the wear index, with the engine spinning 600 revolutions more than it needs to, per mile(!). OTOH, gearing that is too tall will result in weak performance and you'll soon tire of having to feather the clutch and downshift for the slightest incline. There is room for rider preference, i.e. an optimal range. In my experience, that's going to fall within a 7-8% range, as in +3/-5% (taller/shorter) from truly optimal.
An L125 should be capable of exceeding 50mph, with ease. You may need to give it some break-in miles...and come up with a reliable test track, i.e. a specific section of road that allows full speed, in both directions...to negate the effects of wind & incline.
An L125 should be capable of exceeding 50mph, with ease. You may need to give it some break-in miles...and come up with a reliable test track, i.e. a specific section of road that allows full speed, in both directions...to negate the effects of wind & incline.
Yep, that's what I've seen with these, since the first L125s hit the market circa 2003-04. The variable is transmission + primary drive ratio, there have been at least 3 different flavors and we don't know which one you have. That's why I suggested sourcing a 33t cog, from the get-go.Thanks racerx, good point about the break-in, I'll give the 17 another try. Did some searching and it seems like 17/35 or 17/33 seem to be the most common setups.
As a rule of thumb, a 1t change at the C/S sprocket equals 2t at the wheel. It comes in handy, especially if you don't like number-crunching. Find the point where going up 1t at the C/S makes the engine fall on its face...from there optimal road gearing will either be the smaller C/S sprocket...or going one tooth larger at the wheel. Think of this as "getting close" vs fine-tuning. One tooth, at the wheel, "splits the difference"...approximately a 3% change, in this size range. Believe it, or not, a brand-new Trailwing is about 3% taller than the same tire will be once the center of the tread is ~65% worn. IOW, seemingly small changes in tire diameter can have a substantial effect...the circumference changes by a factor of 3.14.
All of this may seem a little persnickety and, to some extent it is. However, getting the gearing optimized is like "free horsepower" (more accurately, it's not leaving any power on the proverbial table) and, it only has to be done once. After you get it right the first time, you've scienced-out your gearing.