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Simple folding bike chainring upgrade turns into a mess

Anonymous Sun 20 Oct 2019 08:55:06 No.1406936 View View Reply Original Report

Quoted By: >>1406937 >>1407042 >>1407479 >>1407615

Hey /n/

I have a cheap folding bike and I wanted to change the front chainring to one bigger in order to make the gear higher, since i have to pedal a lot in order to get to a comfortable speed.

The problem is that my bike has the chainring and the pedal in the same piece, and I don't even know what to buy or what to look for.

Do I have to buy both the chainring and the pedals, as one piece, or as two separate pieces? Can I reuse the pedals?
How to know if the chainring and pedals are compatible with my bike?

Anonymous

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Anonymous Sun 20 Oct 2019 08:55:24 No.1406937 Report

Quoted By:

>>1406936

Anonymous

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Anonymous Sun 20 Oct 2019 09:14:05 No.1406944 Report

Quoted By: >>1406978

You can reuse the pedals, you'll need to find the spanner that fits.
Keep one thing in mind, the left pedal is reverse threaded, I usualy remove both from the same side of the bike, that way the motion I have to do is the same.
You could try looking for a 2x 50/* crankset with replaceable rings and remove the small one, that way you'll have a 50 teeth chainring.
You'll have to look for square taper cranks.
Something like this.

Anonymous

Anonymous Sun 20 Oct 2019 09:17:09 No.1406947 Report

Quoted By: >>1406978 >>1407171

you can unscrew the pedal from the crank with a 15mm spanner

the chainring and the crank are 1 piece

so you need a new crank

not all cranks will fit on your current bottom bracket (the bearing in the frame) (nearly all won't). But nearly all cranks will fit a bearing which will fit in your frame and different bottom brackets are quite cheap.

So you find the new crank and chainring you want, and then find the right bottom bracket for it, and your pedals and your frame will almost certainly work with that.

Anonymous

Anonymous Sun 20 Oct 2019 09:18:12 No.1406948 Report

Quoted By: >>1406978

to remove pedals just remember they unscrew towards the back of the bike

Anonymous

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Anonymous Sun 20 Oct 2019 10:29:48 No.1406978 Report

Quoted By: >>1407018

>>1406944
>>1406947
>>1406948

Hi, thanks for your answers. Looking on Aliexpress I found one I quite like, matches my bike's colour (silver), has 52 teeth and only one ring. .

What do you think ?

https://www.aliexpress.com/item/32848898231.html

Anonymous

Anonymous Sun 20 Oct 2019 12:32:42 No.1407018 Report

Quoted By: >>1407133

>>1406978
your problem arises initially from having a crank with a non-removeable chainring and so you want to replace it with another crank with a non-removeable chainring?

Anonymous

Anonymous Sun 20 Oct 2019 14:15:37 No.1407042 Report

Quoted By: >>1407135 >>1407647

>>1406936
The only compatibility question is how long are the crank arms. They are usually 170mm, but best to measure

Then just Google "170mm single speed crank set 48t" under shopping, sorted by price. You should find some very cheap ones meant for fixie.

https://www.amazon.com/dolphin1986-Crankset-Crankarms-Mountain-Sprocket/dp/B074QH1MYY

Link related is $23 on Amazon
There is a chance your current pedals won't fit. There is regular and bmx threading. These in pic will be regular.
Finally, different crank arms will give you a different chainline. Look up "Sheldon Brown chainline" to see more. You may need to buy a new bottom bracket to get the line correct, unless you can measure ahead and compare to the product info on your chosen crank set. Otherwise you'll have to do extra math and but new bottom bracket and bottom bracket tools

The 48t is the tooth count, replace with whichever number you want.
I'm not sure I believe you though. You obviously have a crank arm puller... How do you own a crank arm puller but not know how to replace a crankset?

Anonymous

Anonymous Sun 20 Oct 2019 18:20:04 No.1407133 Report

Quoted By:

>>1407018
my initial problem was the gear was very low and I had to pedal a lot, but I see your point :^)

Anonymous

Anonymous Sun 20 Oct 2019 18:23:18 No.1407135 Report

Quoted By: >>1407190

>>1407042
>I'm not sure I believe you though. You obviously have a crank arm puller... How do you own a crank arm puller but not know how to replace a crankset?

I just went to a car workshop whose owner is a bike aficionado and asked for help.

HE also told me that I should change the chain too, since the current one will be too tight for something bigger

Anonymous

Anonymous Sun 20 Oct 2019 19:37:05 No.1407171 Report

Quoted By: >>1407315

>>1406947
that's a square taper bb, they're a dime a dozen anywhere
i got lbs around that gives used steel ones away for free, no need to upgrade the bb

Anonymous

Anonymous Sun 20 Oct 2019 20:01:38 No.1407190 Report

Quoted By: >>1407465

>>1407135
Oh, he's right about the chain

Anonymous

Anonymous Mon 21 Oct 2019 00:51:20 No.1407315 Report

Quoted By:

>>1407171
I never said upgrade, I said change. Different cranks often require different spindle lengths. And I said they're cheap.

Anonymous

Anonymous Mon 21 Oct 2019 08:55:39 No.1407465 Report

Quoted By: >>1407473 >>1407516

>>1407190

Do I just buy one like this one?

https://www.aliexpress.com/item/4000169426353.html

They also sell individual links but I don't know if it's worth it, or even if they'll fit with my current chain.

https://www.aliexpress.com/item/32849625574.html

Anonymous

Anonymous Mon 21 Oct 2019 09:20:53 No.1407473 Report

Quoted By:

>>1407465
If you're buying a shimano chain, you better go to a bike shop, or at least a webpage that can ship it to you in less than a week, and those "single links" are for closing the chain, you'll need one too, all you need is a chain that matches your cassette speeds.

Anonymous

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Anonymous Mon 21 Oct 2019 09:35:09 No.1407479 Report

Quoted By: >>1407514

>>1406936
whats the chain line on that bad boi ?
for single speed bikes the chain ring may be closer to the seat pole and chain stays than with a double or triple crank

Anonymous

Anonymous Mon 21 Oct 2019 12:24:43 No.1407514 Report

Quoted By: >>1407553

>>1407479
>shimano chain
I'll buy the crankset from China too, I don't mind the wait, I have another bike.

>>1407479
It has six gears in the rear wheel and only one in the front, I'll measure it anyway this evening and tell you.

Anonymous

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Anonymous Mon 21 Oct 2019 12:32:22 No.1407516 Report

Quoted By: >>1407520

>>1407465
>fake chink shimano chain

lol real kmc chains are like $10

Anonymous

Anonymous Mon 21 Oct 2019 12:53:58 No.1407520 Report

Quoted By: >>1407529

>>1407516

KMC chains in Amazon Spain are like €27.

will this shimano be long enough?

https://www.amazon.es/SHIMANO-8V-116-ESL-HG-40-QLINK-Cadenas/dp/B000NOPPTE

Anonymous

Anonymous Mon 21 Oct 2019 13:21:19 No.1407529 Report

Quoted By: >>1407538

>>1407520
try buying from wiggle

Anonymous

Anonymous Mon 21 Oct 2019 13:47:32 No.1407538 Report

Quoted By: >>1407540 >>1407568

>>1407529
ok

https://www.wiggle.es/kmc-z1-wide-ept-single-speed-chain/

This one is good enough i suppose? The thing is the Aliexpress one came with extra links in order to adjust the chain to the desired lenght, this one will come with them too?

Anonymous

Anonymous Mon 21 Oct 2019 13:50:22 No.1407540 Report

Quoted By: >>1407647

>>1407538
don't get a singlespeed chain if you have 6 cogs in the back. Get a 7 speed chain.

And it will be longer than you need, what you do is remove links with a chain tool to the right length, then connect it with the quick link

Anonymous

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Anonymous Mon 21 Oct 2019 14:21:14 No.1407553 Report

Quoted By: >>1407579 >>1407647

>>1407514
its not really significant to the performance of the drive train
but the front chain ring should line up roughly with the middle of the rear cogset / freewheel / free hub

for a six speed cogset the space between each cog should be 5 mm and each cog roughly 2.5 mm thick
2.5x6=15 5x6=30
15+30=45
45/2=22.5

assume hub spacing of 126 mm
divide by 2 = 63
+ 22.5=85.5
126-85.5=40.5
>distance from lock nut to lock nut not accounted for

so the front chain ring (might) be somewhere around 40.5 mm from the center line of the bottom bracket
of course every bike is slightly different
but I only really bought it up because of chain stay clearance
a larger chain ring may get quite close to the chain stay
and crank arms also have different offsets that affect how close the pedals will be to the chain stay

to have a guess at chain ring size
tooth count x chain pitch = circumference divided by π = diameter /2 = radius
.eg you current chain ring is 40x12.7=508 /3.14=161 /2=80mm radius

ways to alter this are
chaining spacers
Bottom Bracket spindle length to get the right off set (116.5?)
hollow tech bottom bracket (bb width becomes 90mm)(crank moved left or right with spacers)
putting dents in your chain stay with a broom handle and a hammer

what size are your wheels anyway ?
iirc in terms of gear ratio every three teeth added to the chain ring is the equivalent to removing one tooth at the rear
.eg 40x13 and 43x14 would be almost the same gear ratio

Anonymous

Anonymous Mon 21 Oct 2019 14:39:30 No.1407568 Report

Quoted By: >>1407647

>>1407538
here is a six speed chain
https://www.wiggle.es/kmc-z6-6-speed-chain/
https://www.parktool.com/blog/repair-help/chain-compatibility

the chains for bikes with less gears are slightly thicker and will last longer
also due to obsolescence they are sometimes cheaper

the reason for there being so many chain widths is that the newer cog sets will often have more cogs
that are spaced closer together in order to limit the width of the hub and the amount of spoke dishing required
along with this hub spacing has also been getting wider over time

such small changes and differences makes it frustrating to fix bikes

Anonymous

Anonymous Mon 21 Oct 2019 14:46:24 No.1407579 Report

Quoted By: >>1407599

>>1407553
>what size are your wheels anyway ?
The average folding bike size, I suppose. 22"?

Anonymous

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Anonymous Mon 21 Oct 2019 16:03:29 No.1407599 Report

Quoted By: >>1407647

>>1407579
in that case 30 kph should be farely easy on your bike
and if you want to go 40 kph 53x14 should be fine
or 48x13 if your willing to slightly exceed 100 rpm
46x13 will only just work

of note however is that 6 speed free hubs with a 13 tooth gear are rare
and 60 tooth chain rings are more for velodrome bike's
where as chain rings closer to 50 teeth are in common use on older style road bikes

Anonymous

Anonymous Mon 21 Oct 2019 16:42:28 No.1407615 Report

Quoted By:

>>1406936
>buy non shit square taper cranks
>buy chainring that matches crank's bcd
>???
>gottagofast

Anonymous

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Anonymous Mon 21 Oct 2019 17:45:44 No.1407647 Report

Quoted By: >>1407695

>>1407553
>>1407540
>>1407042
>>1407568
>>1407599
My wheels are 49 cm diameter, 19".

5.5 cm distance friom crankset (untightened, without bolt) to middle, 5 cm around 3rd biggest cogwheel.

Anonymous

Anonymous Mon 21 Oct 2019 19:21:30 No.1407695 Report

Quoted By:

>>1407647
>19"
wew lad just go for the largest chain ring that will not collide with your chain stay
50 tooth or more chain ring, the bigger the better really
as going for less than 14 tooth at the rear will cost more and wear out quickly

and if that's not enough you may want 12 tooth at the rear
http://www.velobase.com/ViewComponent.aspx?ID=0ff361bc-8eef-4845-ac11-5ac2756c95d4&Enum=110

Shimano FH-7403 / HB-7400 can fit in 130 or 126 hub spaced frames
is six or seven speed compatible
and fits the 12 tooth sprocket
where as many freewheels can fit 13 as a minimum

>5 cm around 3rd biggest cogwheel
interesting
but this is fairly close to the measurements I have taken of 18 and 21 speed bikes
seems your kit is standard enough

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Simple folding bike chainring upgrade turns into a mess