Smallest chainring / largest cassette installed on RipCurrent S?

Thanks for that link -- very informative and nicely written. Gravel gearing seems like a good starting point for a 60-pound ebike that you might have to ride home on a dead battery -- especially if you live in a hilly place, run hybrid to fat/knobby tires, and prefer lower PAS levels when you still have juice.

Just one small niggle: Judging from some of the jaw-dropping ocean-view mansions and $500,000+ cars I see around San Diego -- especially in La Jolla and Del Mar -- I think some of these folks could afford to have roads repaved before their rides.
I read a little more elsewhere and apparently the very small rear cogs do have a few watts more drivetrain friction - which is enough to sway races, and maybe hard road riding, but it seems well below 5% for a class 3 hub motor e-bike like ours. Given that we are already limited to a 1x drivetrain, the net loss may be negligible, given the smaller steps between gears enabled by a smaller chainrings. Like gravel, we are not riding in optimal conditions (uninterrupted perfect roads, no traffic, peloton, etc)

Also the 38t is the lowest you can go without changing the crankset on a juiced, and I'm not sure there's much net benefit to going lower anyway.

 
Finally got my bike back from the shop and tested a hill near me. It's a hill with an incline that's just moderate enough you'd pedal on the way down. Bike is stock with a 52t chainring. Went to near safe max pedal effort, and still didn't use the two highest gears/smallest cogs, 11t and 12t, and was definitely at a lower than ideal cadence on the 14t, maybe 80 rpm, vs my preferred 90-100. The 52t x 14t x 80 rpm is very similar in speed to 38t x 11t x 85-90rpm.

I'm in pretty good shape, decently strong, so i think the swap would be good for most, at least those not looking to go 30+ mph. As you guys have said, the stock choice of the 52t seems pretty indefensible. I kinda hesitate to discard perfectly good parts and I just had a bunch of part swaps so I'll hold off for now, maybe keep as a later gift to myself.
 

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Finally got my bike back from the shop and tested a hill near me. It's a hill with an incline that's just moderate enough you'd pedal on the way down. Went to near safe max pedal effort, and still didn't use the two highest gears/smallest cogs, 11t and 12t, and was definitely at a lower than ideal cadence on the 14t, maybe 80 rpm, vs my preferred 90-100. The 52t x 14t x 80 rpm is very similar in speed to 38t x 11t x 85-90rpm.

I'm in pretty good shape, decently strong, so i think the swap would be good for most, at least those not looking to go 30+ mph. As you guys have said, the stock choice of the 52t seems pretty indefensible. I kinda hesitate to discard perfectly good parts and I just had a bunch of part swaps so I'll hold off for now, maybe keep as a later gift to myself.
Just to be clear, which chainring did you test here, 38t or 52t?

You're probaby a stronger rider than I am. Overall, keeping my 11-34t cassette and reducing the chainring from 42t to 38t has been a big win at this stage in my return to cycling. Occasionally miss the 105-inch top gear I gave up but pat myself on the back daily for the 30-inch low gear I gained.

The new aluminum chainring, all of $12 from Amazon, seems to be holding up well with my rear hub motor. Time will tell.
 
Just to be clear, which chainring did you test here, 38t or 52t?

You're probaby a stronger rider than I am. Overall, keeping my 11-34t cassette and reducing the chainring from 42t to 38t has been a big win at this stage in my return to cycling. Occasionally miss the 105-inch top gear I gave up but pat myself on the back daily for the 30-inch low gear I gained.

The new aluminum chainring, all of $12 from Amazon, seems to be holding up well with my rear hub motor. Time will tell.
Ah, edited to add that I have the 52t stock chainring.
 
I find 52x11 on my new CCX overkill but I thought 52x12 was fine for 28mph cruising on flat ground on my CC. Back in my road cycling days I could spin out 50x11 descending hill at >30mph but I don’t like spinning at a cadence of over 90rpm. I thought about putting a 48T chain ring on my older CC but never got around to it. I’ve thought about putting an 11sp mountain bike setup on my new CCX but I don’t need super wide cassette gearing.
 
Curious, @Asher and @Dunbar , what diameter wheels are you running? (Actual diameter, please. Somebody changed tire size designations while I wasn't looking.)
I am running the stock IA-2209 innova that came with the bike, 622-47 in the back. I am going to attempt a 622-55 schwalbe I bought, but only after I wear down the stock tire, in 1000+ miles.

In the front I have a 584-60 schwalbe efficiency with a proterra light i25 wheel. But the front wheel doesn't affect the drivetrain speed.
 
I am running the stock IA-2209 innova that came with the bike, 622-47 in the back. I am going to attempt a 622-55 schwalbe I bought, but only after I wear down the stock tire, in 1000+ miles.

In the front I have a 584-60 schwalbe efficiency with a proterra light i25 wheel. But the front wheel doesn't affect the drivetrain speed.
So your actual rear wheel diameter is 622 mm = 24.5 inches?

If so, your top 52/11 gear comes out to 116 gear-inches -- 11" bigger than my stock top gear (105") and 21" bigger than my current top gear (95"). The 52/12 is 106", and the 52/14 is 91".

With a preferred cadence of 70-80 RPM, I'd get a good bit of use out of the 52/14 in the terrain I ride, but not the other two.
 
So your actual rear wheel diameter is 622 mm = 24.5 inches?
Yes but it's the wheel + tire diameter that matters, with tire width and height about equal. 622+ 47 +47 = 716mm = 28.2 inches.

I get ~133 gear inches for the 11t x 52t
 

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Yes but it's the wheel + tire diameter that matters, with tire width and height about equal. 622+ 47 +47 = 716mm = 28.2 inches.

I get ~133 gear inches for the 11t x 52t
Wow, 133" is one big gear!

Last time I was an avid cyclist, way back in the Late Bronze Age, tire and wheel size designations were a lot easier to decipher. Too bad, because as you point out, diameter at the tire contact patch is the key parameter in both gearing and angle of attack.
 
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Declaring my chainring downsize from 42t to 38t a rousing success. With the stock 27.5" wheels and 11-34t 9-speed cassette, that left me with gears from 30.7" to 95.0".

Using RideWithGPS, planned out a nearby 4.1 mi test loop with 355' of climbing on grades up to 10.6%. The loop is typical of half the terrain I ride near my house.

Rode the loop 4 times as a final test on known grades. Wouldn't have minded a lower 1st gear on the 10% pitch, but the 30.7" low gear worked well enough. (Kept cadence above 55-60 rpm, and that kept my knees from mutiny.) Never once wished for a bigger top gear, though wouldn't want to go smaller than 95" there.
 
That's great news. I have 103.5 to 35.7 gear inches on my RipCurrent S with the 38T chainring and the stock 11-32 cassette.

My next decision will be when do I upgrade the cassette and possibly the derailleur (if I want to go lower than 31.8 gear inches). The LTWOO A5 derailleur is rated for a max of 36 teeth on the cassette. I definitely wish for less than the 35.7 gear inches I have now. Question is whether I will be satisfied with a 36t max cassette at 31.8 gear inches or do I just go ahead and replace the A5 with an A7 (like $20 on Amazon) along with a 11-42t cassette to get to 27 gear inches.

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That's great news. I have 103.5 to 35.7 gear inches on my RipCurrent S with the 38T chainring and the stock 11-32 cassette.

My next decision will be when do I upgrade the cassette and possibly the derailleur (if I want to go lower than 31.8 gear inches). The LTWOO A5 derailleur is rated for a max of 36 teeth on the cassette. I definitely wish for less than the 35.7 gear inches I have now. Question is whether I will be satisfied with a 36t max cassette at 31.8 gear inches or do I just go ahead and replace the A5 with an A7 (like $20 on Amazon) along with a 11-42t cassette to get to 27 gear inches.
How about a 36t chainring? Do you get much use out of the 103.5" top gear?

Forgot to mention that my new gearing allowed me to do the aforementioned test loop 3 times at PAS 1/9. Wouldn't say comfortably, but tolerably. And I'm not a strong rider (though getting stronger).
 
A throttled, 76 lb, 1000w rear hub propelled RipCurrent S with beyond Class 3 speed cap on "blue and black" MTB singletrack trails? Assuming you're referring to Trailforks color-coded "trail difficulty" ratings, this seems extremely dangerous and highly illegal.

It's also one of the reasons a lot of land managers still won't allow ANY ebikes on trails they're responsible for - they don't want to constantly check bikes for Class 1 compliance, nor do they want to haul riders with broken bones or worse out of the woods.

Please keep your "Class 4" ebike on ATV and other motorized trails. And wear a full-face helmet when doing so, even if you change the OE gearing.
How about saying speed limits instead of “class 4” im lazy and stupid if I’m gonna do some tracks at speeds above 20mph. That’s pushing it anyway. Thanks for the heads up. Lol
 
How about a 36t chainring? Do you get much use out of the 103.5" top gear?

Forgot to mention that my new gearing allowed me to do the aforementioned test loop 3 times at PAS 1/9. Wouldn't say comfortably, but tolerably. And I'm not a strong rider (though getting stronger).
I do enough mixed riding that I do use the max 103.5 top gear when I commute to work. So far the low gearing is working even on the single tracks. At this time, I'm not seeing the need to change the rear cassette. If and when the derailleur or cassette wears out/breaks then I'm adjust the gearing further.
 
That's great news. I have 103.5 to 35.7 gear inches on my RipCurrent S with the 38T chainring and the stock 11-32 cassette.
Thank you for the information.
If I am correct, it looks like your 9th gear is about the same as 7th with the 52T chainring.

Suggestions for buying the 38T chainring for my 2021 model RipCurrent S ?
(manufacturer, model, or additional parts needed besides the chainring)

Any ideas or warning for me doing the chainring swap by myself?
Did you consider a 42T chainring?

(I have never wanted a higher gear on my RipCurrent S, but want lower gearing for some (to me) difficult hills)
 
Thank you for the information.
If I am correct, it looks like your 9th gear is about the same as 7th with the 52T chainring.

Suggestions for buying the 38T chainring for my 2021 model RipCurrent S ?
(manufacturer, model, or additional parts needed besides the chainring)

Any ideas or warning for me doing the chainring swap by myself?
Did you consider a 42T chainring?

(I have never wanted a higher gear on my RipCurrent S, but want lower gearing for some (to me) difficult hills)
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

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.
 
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

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.
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.
 
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

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. Think I will go to the 38T and try it for a while, maybe up to 42 later.
Did you use the two stock round plates on each side of the chainring, or did you get smaller ones?
 
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.
 
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