Has anyone increased their front sprocket size? Any concerns or issues?

ck1224

Member
IMHO, get rid of the bike and get something more appropriate.

Maybe, one day I can sell the bike and upgrade to a faster, bigger bike. or keep both for different purposes (use this bike for slower trails/areas, and use the faster bike for faster areas)?
 

ck1224

Member
The OP might want to take a look at Sheldon Brown's GEAR CALCULATOR. You can input your wheel size, crank arm length, chainring tooth count, preferred cadence, etc to see how changes in the chainring and free wheel gearing impact your speed.

For example with 20x1.25 tires, a cadence of 90rpm, a 52t chainring, and a 14t small cog on the free wheel your speed would be 18.3mph. Going with an 11t cog gets you to 23.3mph.


I did it using my brain and google calculator, and just calculated 110 cadence at 28 mph using 23" (fat tire) diameter wheels and 14/52 gear ratio. With the 80T, it would be about 72.
 

ck1224

Member
Could it be that you bought the wrong eBike for high speed? Based on wheel size, crank length, and a 7 speed freewheel, it might have been obvious it would not be a high speed bike. No idea why a LBS would not be able to change the chainring and cranks. It's just the right bolt circle for the chainring, width for a 7 speed chain, and correct length of chain. Simple bicycle stuff, but an 80t has to be tough to find.

well, on my limited income, it is a good starter bike for a 1200 bike budget (just to buy bike without all the accessories, insurance, etc.) up to 2k already.

It is: I think this might work: https://www.jackssmallengines.com/j...7uvxkq2bk7nkrbusdpi7uauij9lwbfw8tpmjmtkj9cy8u
 

Nova Haibike

Well-Known Member
The chainring linked to by Timpo would also require you to replace the crankset as well, because those rings are meant for bikes with replaceable rings, which is not what your bke has. Also as mentioned, there is a good possibility an 80T ring would not even fit onto the bike; it may not clear the chainstays.
 

ck1224

Member
Not sure which model you have but I'm guessing that all the 20" wheel models have the same 14-28 rear cassette, which would be a much easier modification to reduce your cadence at 28mph. A rough calculation from me suggests that you should hit 28mph at just below a cadence of 90 with 52T on the front and 12 on the rear, whereas you are looking at almost 100 cadence for 52x14. A lot cheaper than having an 80T chainring cast (which would actually need less than a lazy 70 cadence to hit 28mph with 14T on the rear).

I calculated 110 cadence with 23" inch wheels, 72 with new chain ring.
 

ck1224

Member
The chainring linked to by Timpo would also require you to replace the crankset as well, because those rings are meant for bikes with replaceable rings, which is not what your bke has. Also as mentioned, there is a good possibility an 80T ring would not even fit onto the bike; it may not clear the chainstays.

Ok, I can't tell what type of chain ring is on there. I thought it was possibly a type A (chain ring), but the bolt is really tight, so I didn't want to try to take it off unless I had to and see what it is. Rattan's tech. support doesn't know or won't help me with what kind of chain ring specifications are on the bike. However, it is a Prowheel (Prowheel stamp is on the crank arm, and I emailed them to find out more info about their products).

So,, you are saying that my bike doesn't use a type A chain ring, so ebikes use other types of chain ring types? I measured the chainstay to middle of crankset clearance and it would accommodate up to an 80T.
 
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Nova Haibike

Well-Known Member
So,, you are saying that my bike doesn't use a type A chain ring, so ebikes use other types of chain ring types? I measured the chainstay to middle of crankset clearance and it would accommodate up to an 80T.

Your bike does not have a separate chainring at all; the ring is swaged (press fit) to the crank and is not removable. So if you want an 80T ring, you need a whole new crank that allows the use of removable rings.
 

Timpo

Well-Known Member
Ok, I can't tell what type of chain ring is on there. I thought it was possibly a type A (chain ring), but the bolt is really tight, so I didn't want to try to take it off unless I had to and see what it is. Rattan's tech. support doesn't know or won't help me with what kind of chain ring specifications are on the bike. However, it is a Prowheel (Prowheel stamp is on the crank arm, and I emailed them to find out more info about their products).

So,, you are saying that my bike doesn't use a type A chain ring, so ebikes use other types of chain ring types? I measured the chainstay to middle of crankset clearance and it would accommodate up to an 80T.
I had exact same chain ring as well, yes, identical one to yours.
Your crankarm and chain ring are NOT separable.
They do not come apart.
 

Timpo

Well-Known Member
Ok so, here's the link again, it says 130BCD

You just need to find a crankset with 130BCD

Make sure get the bolts as well
 

Papadevo

New Member
The cheapest way to approach this is to change the rear freewheel to as small of a cog as you can fit, then up the chainrings/crankset if you can push harder at 70-90 cadence. I see some 7 speed free wheels available on Amazon that go to 11, but you will also need specialized tools to do the job yourself. Changing the crankset and chainrings could also involve a bottom bracket, FYI.
A decent bike shop will do this all for you for a small labor fee plus parts. They may be COVID busy, and annoyed by the last customer, but generally like folks that have some idea of what they want to do and are willing to pay for expertise. Reputable shops will get you an estimate before any work is done.
It’s possible to push 30+ mph with a 20” wheel and standard bike parts. Your bike will need some modifications. I have a no motor 20” folder and it is awesome in cites and navigating crowds by bike. May be best to enjoy what you have for what it is.
But have fun! One of the joys of cycling is experimentation so choose an option and go, go, go!
 

Timpo

Well-Known Member
The cheapest way to approach this is to change the rear freewheel to as small of a cog as you can fit, then up the chainrings/crankset if you can push harder at 70-90 cadence. I see some 7 speed free wheels available on Amazon that go to 11, but you will also need specialized tools to do the job yourself. Changing the crankset and chainrings could also involve a bottom bracket, FYI.
A decent bike shop will do this all for you for a small labor fee plus parts. They may be COVID busy, and annoyed by the last customer, but generally like folks that have some idea of what they want to do and are willing to pay for expertise. Reputable shops will get you an estimate before any work is done.
It’s possible to push 30+ mph with a 20” wheel and standard bike parts. Your bike will need some modifications. I have a no motor 20” folder and it is awesome in cites and navigating crowds by bike. May be best to enjoy what you have for what it is.
But have fun! One of the joys of cycling is experimentation so choose an option and go, go, go!
I don't think it does.

The current crankset has square tapered version.

So, as long as the OP gets another square tapered crankarm, it should be fine.
 

ck1224

Member
I would recommend trying a new 11-28 or 11-32 rear cassette before changing the front ring or cranks.

You will also appreciate the increased gear range with the larger cassette and will not need a new chain. ;)

yeah, I think that might be the best choice for now. I don't know if the rear cassette is standard or non-standard as some articles have mentioned that some ebikes have skinnier cassettes due to wider hub motors It is 1 1/4 inch spacing between the highest and lowest gears.

maybe that and bumping up to a 56 to 62T chain ring (not sure if I could find this, and what would be needed crankset and bottom bracket change).
 
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FlatSix911

Well-Known Member
yeah, I think that might be the best choice for now.

I don't know if the rear cassette is standard or non-standard as some articles have mentioned that some ebikes have skinnier cassettes due to wider hub motors It is 1 1/4 inch spacing between the highest and lowest gears.

Good call. ;)

The Shimano 7-speed cassette is a standard dimension and should be interchangeable... check with your local bike shop for a 11-28T freewheel.

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