Chain sizing help

hixyhicks

On saturday i will be fitting my bafang motor.The motor will have a 42 tooth lekkie bling ring with a 8 gear cassette.Do i fit the chain like this.

I take the new chain around the big chain ring on rear cassette miss the derailler, then around the bling ring.Then connect the chain together adding an extra 4 links .

If you understand,does that seem correct.

hixyhicks

Its 2 links not 4 my bad.

Charlie_Croker

No
you don't miss the rear derailleur out

watch a video or two, here's one if your unsure

JBA

You DO miss out the rear derailleur if using the largest chain ring - largest sprocket method to size a chain.

steve_sordy

I know of about six different ways to size a chain. I prefer this one.

Thread the chain around the biggest front ring and the biggest rear ring, through the derailleur as normal. Adjust the chain so that the mech arm points forward at 45 degrees.

Before you cast the chain length in stone, there is one more step if the bike is a full suspension bike.
Let the air out of the shock and fully compress it, or get a very heavy mate to compress it. It is important that the suspension is fully compressed. Why do this? Many full suss bikes have rear suspension that makes the rear wheel go backwards for some of its travel. This will put extra pressure on your chain. If it is too short then your bike could be quite badly damaged, including having the mech ripped off.

hixyhicks

Thank you all.

N0bodyOfTheGoat

http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html helps for some bike types too.

According to above, when I change from 11-32 to 11-34 cassette on my Cube sometime very soon, I won't require any more links.

steve_sordy

N0bodyOfTheGoat said:

..................
According to above, when I change from 11-32 to 11-34 cassette on my Cube sometime very soon, I won't require any more links.

That implies to me that the 32T set up could have been 1" shorter, ie one complete link, comprising one inner and one outer (and still safe).

That is only of value if you have not already got your chain as short as possible, either by calculation or experimentation. Once it is as short as possible (and still safe), then increasing the size of the front ring or the largest ring on the cassette will over-stress the mech.

I once sized my chain correctly, and then later on added a Bionicon chain device. Its a dangler type and it supports the lower strand of chain by lifting it a bit. It stops the chain from whipping up and down and it was before clutch mechs and narrow-wide teeth on chain rings were available. That extra tension on the chain in my opinion did not over-stress the mech, but it did mean the the chain guide wore out very rapidly. Correct chain length is important.

N0bodyOfTheGoat

Just going on what the calc says with 415mm chainstay, 50T large chainring, unrounded result is ~54.30 vs ~54.77 inches. As you say, I'd expect 11-32 to probably be fine with 54 links, given 50/32 shouldn't be selected by choice.

steve_sordy

N0bodyOfTheGoat said:

Just going on what the calc says with 415mm chainstay, 50T large chainring, unrounded result is ~54.30 vs ~54.77 inches. As you say, I'd expect 11-32 to probably be fine with 54 links, given 50/32 shouldn't be selected by choice.

I'm assuming from the above, you have a 1x set up. So why wouldn't you choose a 32 driving a 50t for the steepest climbs - that is what it's there for. If you never need it then fit a 34 on the front and then you can use the whole range of your cassette, and go faster!

N0bodyOfTheGoat

steve_sordy said:

N0bodyOfTheGoat said:

Just going on what the calc says with 415mm chainstay, 50T large chainring, unrounded result is ~54.30 vs ~54.77 inches. As you say, I'd expect 11-32 to probably be fine with 54 links, given 50/32 shouldn't be selected by choice.

I'm assuming from the above, you have a 1x set up. So why wouldn't you choose a 32 driving a 50t for the steepest climbs - that is what it's there for. If you never need it then fit a 34 on the front and then you can use the whole range of your cassette, and go faster!

You've not clicked the link, have you?

It asks for largest chainring, my Cube has a compact double 34/50. I'll hapily use 50/28 if I'm on a climb I think I can stay in the 50T the whole way up and I'll happily use 34/12 on a steep climb that briefly becomes a lot easier. But I won't actively choose 50/32 or 34/11, besides anything else, lots of nasty chain grinding that trim won't fix.

steve_sordy

N0bodyOfTheGoat said:

..............my Cube has a compact double 34/50. I'll hapily use 50/28 if I'm on a climb I think I can stay in the 50T the whole way up and I'll happily use 34/12 on a steep climb that briefly becomes a lot easier. But I won't actively choose 50/32 or 34/11, besides anything else, lots of nasty chain grinding that trim won't fix.

WOW! You must have thighs of steel!!

JBA

He's talking about a road bike by the sound of it, @steve_sordy.

N0bodyOfTheGoat

Yes, Cube road bike rather than my Voodoo fatbike commuter, didn't realise until just now than signatures don't show on mobile version.

steve_sordy

JBA said:

He's talking about a road bike by the sound of it, @steve_sordy.

With this being the Mountain Biking Forum, it never occurred to me he was referring to a road bike. I did wonder about the size of the chain rings though.

I used to ride with a 10-50 cassette and a 30t on the front and I still couldn't get up some climbs! Hence my expression of admiration.