Sidewinder Jerry
Well-Known Member
What kind of engine do you have and what size tires do you use?
Is this a fat tire bike or is the outside diameter 26"48cc 2-stroke and Hookworms 26”.
I'm going to explain how shifting works with a shift kit. It's based more on full throttle than it is on cadence assist. You have two primary rpms to be concerned with at full throttle; they're max horsepower rpm and max torque rpm.I’m sad. But happy I got shifty today, my bike is fully operational.
I do need to bring my engine gearing ratio matched to cadence, I’m pedaling over 90rpm at less than mid-throttle, need that down to 60?
Me too. This hobby is my thing. I have plans for bikes, and I want the best. I have a SBP shift kit on my "Green Bean" that has been on for years. Never had any problems with it once I got it aligned and tensioned properly. Just changed out the bearing in the crank freewheel after thousands of miles. An after a hundred or so builds of 2t kits in the last half a decade, now I wanted to start on 4 strokers with gears.To be honest hearing SBP is shutting down is breaking my heart.
I run the normal SBP kit, to a 44 on the crank, then from a 40 to the back. The back goes 32, 26, 22, 18, 14. I mix up the back cogs sometimes. I just found my go to cog set for the back a few months ago. Turns out they are all vintage cog sets, and becoming rare. lol. I run 24" on that bike. It pulls from a stop, I can creep as slow as I wish. It has a top speed of about 47-48 miles an hour with this set up. I run around 18-30 mph usually. Id I was to do the same setup on a 26" I would use a 48 or 50 tooth for my crank drive cog. An I would go up to a 44-46 on the cog that feeds the rear. It's my trail bike, good for street speed, but also pulls me through all the muddy trails no problems.If I’m in lowest gear climbing a hill, and engine rpm is less than mid-range, and starts to lug, my cadence is too fast to bump it up into torque range.
But...now I see my problem. If I match cadence to throttle range...I’ll never be able to start it.
Hmmmm...
I got spoiled with my etrike. 7x3 gearing, and max torque at low RPM, it will climb 30 degrees for a mile at 5mph.
Can’t climb like that on a DF you wobble and fall down
If I’m in lowest gear climbing a hill, and engine rpm is less than mid-range, and starts to lug, my cadence is too fast to bump it up into torque range.
But...now I see my problem. If I match cadence to throttle range...I’ll never be able to start it.
Hmmmm...
I got spoiled with my etrike. 7x3 gearing, and max torque at low RPM, it will climb 30 degrees for a mile at 5mph.
Can’t climb like that on a DF you wobble and fall down
The final setup I had on the LandRider reduction range was 49.21:1 to 18.82:1. In the lowest gear I had to pedal assist on hills that were more than a 20% grade. I had found in the past a 55:1 reduction could get me up 25% grade hills with minimal assist. However, 30% grade hills are common here and require a good bit of assist at a 55:1 reduction.
My engine, a Robin Subaru 35 produces 1.6 hp at 7000 rpm and 1.6 ft/lb of torque at 5000 rpm. Total weight is 350 lbs. Now a bigger engine that produces more torque and a lower total weight won't need as much of a bottom end reduction that I needed. With the triple chainring shift kit and custom built 7 speed 34-13 freewheel my reduction range is now 66.79:1 to 16.25:1. I can now pull an added 200 lbs up 30% grade hills with very little pedal assist in my lowest gear.
Your situation sounds like the reduction range isn't low enough. Your choices then become put a bigger cog in the back and/or add a second smaller chainring up front.
Custom Built Freewheel
As I'm currently building a Schwinn Sidewinder to replace the LandRider, I decided to replace the old sprockets on my custom built 7 speed freewheel (34,28,24,21,18,15,13). What's needed to build this 7 speed freewheel is an 8 speed SunRace 34-13 freewheel and a SunRace 7 speed 28-14 freewheel...motoredbikes.com
If you don't do these things then you'll have to sacrifice top end speed to get a lower bottom reduction by lowering the input reduction coming into your shift kit.