Multi-speed to Single speed conversion

[JohnnyReb]

Im looking to convert my ebike from a multi-speed to a single speed. Pictured below is some of the stuff i wanna use.

I dont know about that chain/bash guard deal though. Comes with a BSA adapter, but only allows up to a 38T chainring. I've got a 52T atm. Kinda doesn't make sense for me to go that small a chainring. I use pedal power to assist the bike in either an uphill struggle or to get the bike up to full speed quicker. Full speed for this bike is about 28.5mph. I could do with a 48T fine, but still wouldn't fit them chain guards.

I assume the single speed 14T spacer deal will work.?

And about the chainrings... I've not dove into the crank set area of things, but wats up with some cranks attaching to the chainring with four bolts but my bsa deal looks like the chainring might spline on?
There any benefit for one or the other?
Seems a bit difficult to find chainrings with inner splines.

 

[RunForTheHills]

I can't see the attached photos. Pictures and details of the bike would help. Is it the Ridstar thing from your controller thread with the rear hub motor? Does it use a freewheel or cassette? If it is the Ridstar, why replace the crank/chainring when it is already a single speed in the front? You just need to replace the freewheel/cassette and maybe install a chain tensioner. If the bike has horizontal dropouts, you may be able to tension the chain without a tensioner. You will need a tool to remove the freewheel/cassette and you will need a chainbreaker to remove any extra links you don't need in the chain.

With 20" wheels at 100 RPM (most people spin their pedals between 60-80RPM) the 52T chainring with a 14T in the back will go 20.6 mph.

Sheldon Brown's Bicycle Gear Calculator



https://www.amazon.com/HERCHR-Conversion-Freewheel-Accessory-Mountain/dp/B09YRSDW3K

https://www.amazon.com/Tensioner-Si...MIx6Cv4rOQhQMVpBmtBh2rPwu3EAQYASABEgLWTPD_BwE

 

[lnanek]

I tried a chain tensioner like in the OP's attachments when I went single gear, but the little loop of metal eventually got loose and would pull toward the chain and rattle:


Eventually I had to upgrade to the Shimano equivalent:

Shimano Alfine CT-S500 Chain Tensioner (Silver)

Shimano Alfine CT-S500 Chain Tensioner Features: Not for use with coaster brake or fixed gear hubs 20 tooth max rear sprocket 16 tooth chainwrap... ICTS500

www.performancebike.com

 

[JohnnyReb]

Correct, this is the RidStar rear hub motor ebike thing.
I dont knw why them pics didnt work.
It does have a cheap shimano cassette and derailleur.

The only reason to reduce chainring diameter would be to fit a chain guide/bash guard deal on there. For what i use the pedals for, it doesnt make sense to change to smaller chainring.

 

[RunForTheHills]

A 38T in the front with a 14T in the back would result in a pedaling speed of about 15 mph at 100 rpm. Most people are comfortable pedaling around 60-80 rpm. I like a higher cadence of around 90. You will feel like you are spinning out around 100-110 rpm. So you will spin out around 15-17 mph with a 38T chainring. You don't really need a chain guard. I use a metal clip to keep my pants out of the chain when I wear long pants.

 

[lnanek]

I use 75t in front so I can pedal fast enough to contribute at 30mph:

https://a.co/d/9uiU2FQ

That said, I've never found a guard big enough for it, so it does smudge my legs with grease sometimes. Also took joining links from two chains to reach all the way around it.

https://www.amazon.com/gp/aw/d/B01N3RBJL1/ref=ox_sc_act_image_3?smid=A1C9T7ACO5T769&psc=1

Yeah, that's the sort I tried where the buckle got loose and rattled. If you already have a cheap Shimano derailleur, just leave it on as a chain tensioner. You can cut and tie off the shift cable if needed.

 

[JohnnyReb]

Sweet Mary a 75T!
Yeah see this bike generally be traveling @ 28.5mph on throttle, then i'll start pedaling on an incline to keep the speed up. I'm pedaling like hell though. Or i can get it going a little faster then the motor can pull but again, pedaling like hell.

That metal strap on the derailleur/tensioner bothers me mental. I just ordered the tensioner and single speed conversion cassette replacement deal. The tensioner i ordered doesn't come with that little metal doodad.

I really don't have a problem with pant-legs getting caught in/or grease flying off of the chainring. I just got excited about the cool stuff that's available.

 

[MoneyPit]

Don't use that 14T freewheel. Here's mine after about 2 miles. Different name stamped on it but its the same $2 product.



I would also use a better tensioner. I've used something real similar to the one you linked originally but the thing I would worry about is the pulley. The alloy ones I used got worn down fast. I ended up going thru a couple of them before I went to a Surly Singleator and that was the last one I needed to replace. Here it is in service along with a 60T front chainring. This was back in 2017 before I started building mid drives and 2wd mid+hub bikes.


I used the stainless with-wrench-flats singlespeed adapter on that motor. I forget who sells it at the moment. You REALLY want one with wrench flats or that freewheel is going to be a permanent resident.

This was a 30mph bike on throttle and 34 mph on pedal assist working my ass off. 60T in front and a Shimano 16T in back. As you can see above I tried the 14T step-down and it didn't work out. The Shimano was a durable product.

To clear the stays with that big ring, I needed a longer bottom bracket. 176mm IIRC. Another way I did it on another bike was to use a triple chainring crankset and just remove the two inner rings. That style of crank puts the big ring out pretty far so it cleared a fat bike stay. Not sure if that will help you in your project or not.

 

[MoneyPit]

...wats up with some cranks attaching to the chainring with four bolts but my bsa deal looks like the chainring might spline on?

Thats a special type of chainring that is a different standard from say a 4-bolt 104 BCD which may be what you are looking at on your bike now. Forget about it its only used for teeny tiny mtb rings. This was 50T front chainring and 104 BCD SRAM triple crankset.


If I were you I'd forget about a bash guard. Nobody makes them for big road-bike-sized chainrings because nobody uses big rings on emtb's

 

[lnanek]

The nice thing about the dual wheel chain tensioners vs. the single wheel ones is that they increase chain wrap as well, not just chain tension. The chain makes more contact around the rear sprocket, so slips less.

 

[JohnnyReb]

MoneyPit...If you would be so kind, i have a few questions for ya:

What freewheel is decent?

"If I were you I'd forget about a bash guard. Nobody makes them for big road-bike-sized chainrings because nobody uses big rings on emtb's "
Is the joke that we both use large chainrings on emtb's? 'Cuz both of us use big ass chainrings.

"To clear the stays with that big ring, I needed a longer bottom bracket. 176mm IIRC."
What are "stays?" Also, i searched for 176mm IIRC and could find anything.

"Thats a special type of chainring that is a different standard from say a 4-bolt 104 BCD which may be what you are looking at on your bike now."
Mine is prolly splined on. Im not looking at 4 bolts connecting the cranks to the chainring.

Inanek:
Yeah, i was getting all butt-happy about the front chain tensioner set-up.

 

[RunForTheHills]

"To clear the stays with that big ring, I needed a longer bottom bracket. 176mm IIRC."
What are "stays?" Also, i searched for 176mm IIRC and could find anything.

The chainstays are the tubes on the bicycle frame that run from the bottom bracket to the rear dropouts. A wider bottom bracket spindle would push the chainring further out away from the chainstay, but it will also mess up the chainline (the rear sprocket and chainring should be in a straight line) and the Q-Factor (crank width, you will have to pedal bow-legged if it is too wide).

 

[RunForTheHills]

Also note that a freewheel is not the same as a cassette. You have to know which type of cogs your rear hub uses so that you can order the correct part.

 

[2old]

FME, White Industries makes the best SS freewheels, but they're expensive.