Smallest chainring / largest cassette installed on RipCurrent S?

[tyyoda]

I

I bought a 38 tooth chainring from Bikeinn to replace the stock 52 tooth. Took 40 days to arrive because it was not in stock at the time. Installation was easy with Allan key and the chain breaking tool to remove 4 links. I re-used the original chain ring guard plates. I put one chain ring guard on first, and the chain ring behind the 5 crank "fingers", then the other chain ring guard in front of the crank fingers. Then I put all 5 bolts in very loose to hold everything temporarily in place. Then I removed one bolt at a time and inserted the sleeves and tightened up. The chain does not rub on the guards even in the lowest or highest gear. The chain just touches the ends of the 5 fingers but does not cause a problem. Eventually I'll get smaller guard plates to give me a bit more clearance, such as when I walk the bike across a railroad track where there is no crossing. I might get a guard slightly bigger than 38, maybe 40 which may protect the chain ring a bit more. They have them at Aliexpress for about $40 for two. Search for "Folding Bike Chain Guard 130 BCD Aluminum Alloy 38T". I notice a slight improvement on hills from the 52 to 38 tooth chain ring but it is not as much of a difference as I expected. With 52 tooth, I could barely struggle up a 6% grade without any assist, now I can barely get up 8%. With assist, it feels like the sensor is getting more torque from my pedalling so it boosts the power more on hills. I haven't had a chance to ride in the highest gear but I expect it will still be plenty fast without spinning out.

Glad you are having a good experience. I don't use the factory chain ring guards on my bike. I keep the outside one on my wife's bike.

 

[Earl Furman]

Sorry for the delayed response. This is what I bought. https://www.amazon.com/gp/product/B0BBG9VKRL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1&psc=1

https://www.amazon.com/gp/product/B083NHXQHD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Easy to change the ring yourself. Buy steel chainring bolts. One one of my bikes, I used the OEM chainring bolts and added stainless washer for shims.

If you don't plan on riding on single track trails, a 42T would probably work better. To be honest, I still can go 28 mph + at 92 cadence. It's is pretty rare that I feel I wish I had anything higher than the 38T ring.

Thanks for your help and encouragement. Am now using the 38T YBEKI chain ring you are using. The low grades are easier on my RCS, steep grades are still hard for me in ECO mode. I purchased "42T Bash Rings" from Chain Reaction Cycles in England -- two for 3.18 pounds shipped. Painted outside one with Rust-oleum Gloss Protective Enamel. Used 3mm spacers instead of the stock 5mm ones, but reused the stock bolts. Bent the inner protective ring a small amount with a wood block and hammer as it was close to rubbing on the chain when on the lowest cassette gear.

Hopefully final update: When the pantograph bearings in my stock derailleur failed at 900 mi, it wore out the stock 9-speed 11-34t cassette and chain. The newish 38t aftermarket chainring was worn enough that I took the opportunity to redesign the entire drivetrain. Went to a 10-speed Shimano Deore 11-42t cassette, a much better Deore derailleur, an SRAM EX-1 chain, and a DECKAS 40t narrow-wide aluminum chainring.

Result: 26.2 to 100.0 inch 10-speed gearing — perfect for my hilly local terrain, current level of fitness, and 500W hub-drive.

Moral of the story: It can take several tries to get gearing just right.

I am now using the 38T chain ring with the stock cassette on my RCS. What do you think of using this as a replacement for the stock RCS cassette? https://www.amazon.com/dp/B07T89FMH...p?_encoding=UTF8&*Version*=1&*entries*=0&th=1

 

[Jeremy McCreary]

Thanks for your help and encouragement. Am now using the 38T YBEKI chain ring you are using. The low grades are easier on my RCS, steep grades are still hard for me in ECO mode. I purchased "42T Bash Rings" from Chain Reaction Cycles in England -- two for 3.18 pounds shipped. Painted outside one with Rust-oleum Gloss Protective Enamel. Used 3mm spacers instead of the stock 5mm ones, but reused the stock bolts. Bent the inner protective ring a small amount with a wood block and hammer as it was close to rubbing on the chain when on the lowest cassette gear.
View attachment 161745

I am now using the 38T chain ring with the stock cassette on my RCS. What do you think of using this as a replacement for the stock RCS cassette? https://www.amazon.com/dp/B07T89FMH...p?_encoding=UTF8&*Version*=1&*entries*=0&th=1

I rely on my LBS mechanic to sort out cassette-derailleur compatibility and potential chainline issues.

Only you can determine if a given cassette or chainring will meet your gearing needs. My approach:

1. Use an online gearing calculator or spreadsheet to calculate your current top and bottom gears in gear-inches (which take rear wheel diameter into account).

For example, my current gearing is 26.2 to 100 gear-inches, the latter being top gear.

2. Keep these 2 numbers in mind as you ride your terrain and take note of which feels too low, too high, or just right.

3. Estimate the next bottom and top gear to try in gear-inches. Two to three gear-inches can make a noticeable difference at the bottom end, 4-5 gear-inches at the top.

4. Go back to the gearing calculator or spreadsheet to see if you can reach these new bottom and top gear targets with a chainring change alone. If not, play with the cassette as well.

5. If the cassette needs to change to hit your targets, rely on the cassette manufacturer to figure out the proper (exponential) spacing of the intermediate cogs. Then consult your mechanic, as the new cassette might require a different derailleur or chain length.

You might rethink your assist strategy as well. Looks like we both have hub-drives and both prefer low assist. You say that your bottom gear is still too high for steep grades in Eco mode.

But on a hub-drive, my mechanic advises upping the assist on steep hills to keep chain tension at more reasonable levels. This uses more battery but has several advantages: (1) Bottom gear can be higher. (2) Drivetrain stress and wear are reduced. (3) The risk of dropping your chain is also reduced.

Works well.

 

[Earl Furman]

I rely on my LBS mechanic to sort out cassette-derailleur compatibility and potential chainline issues.

Only you can determine if a given cassette or chainring will meet your gearing needs. My approach:

1. Use an online gearing calculator or spreadsheet to calculate your current top and bottom gears in gear-inches (which take rear wheel diameter into account).

For example, my current gearing is 26.2 to 100 gear-inches, the latter being top gear.

2. Keep these 2 numbers in mind as you ride your terrain and take note of which feels too low, too high, or just right.

3. Estimate the next bottom and top gear to try in gear-inches. Two to three gear-inches can make a noticeable difference at the bottom end, 4-5 gear-inches at the top.

4. Go back to the gearing calculator or spreadsheet to see if you can reach these new bottom and top gear targets with a chainring change alone. If not, play with the cassette as well.

5. If the cassette needs to change to hit your targets, rely on the cassette manufacturer to figure out the proper (exponential) spacing of the intermediate cogs. Then consult your mechanic, as the new cassette might require a different derailleur or chain length.

You might rethink your assist strategy as well. Looks like we both have hub-drives and both prefer low assist. You say that your bottom gear is still too high for steep grades in Eco mode.

But on a hub-drive, my mechanic advises upping the assist on steep hills to keep chain tension at more reasonable levels. This uses more battery but has several advantages: (1) Bottom gear can be higher. (2) Drivetrain stress and wear are reduced. (3) The risk of dropping your chain is also reduced.

Works well.

Just a quick report after 150+ miles with the 38T chainring on my RCS, all with "eco" assist. Was able to to a 1900ft rise on a dirt road (moon pass just south of the Route of the Couer D'Aline) without resting -- a year ago with the 52T chainring it took several rest stops. Much easier this time. Thinking about I realized that the smaller chainring requires about 75% of the peddle force to generate the same chain tension on the cassette, which in turn means that the torque-assist now gives more assist for a given peddle push which gives quicker starts and more motor assist for given effort on hills.

 

[Mark_SF]

I just put a 38mm front chainring and 11-42t cassette on my RCS. Had to add a derailleur mount extender to get the cage to clear the biggest rear cog. Works fine and looks like about 28 mph is top speed with reasonable cadence.

 

[Mark_SF]

 

[Earl Furman]

View attachment 165587

Thanks for the information. I have the 38 in front, but still the original 11-32 in rear and am wondering what is the upper limit of the stock derailleur. Specifically, could I use an 11-40 without making any changes to the derailleur? If not that, how about an 11-38

BTW I found that the smaller chain ring made a big difference, partly because, for a given force on the peddles it increased the tension on the chain which in turn made more force on the Torque Sensor which in turn increased the motor's assist.

 

[Mark_SF]

My impression is that at 34 teeth the L5 derailleur is maxed out. I didn’t change the derailleur per se, rather I installed the extender mount. It is the black part to which the derailleur is mounted, the other end is fastened to the frame. $9 from Amazon.