Changing rear cassette query

Danville · 11-06-2020 08:25PM #1

I am presently using Shimano 52-36 with 11-28 cassette.
Can I change the rear cassette to a 12-34 with a simple swap or will it be necessary to change the chain length?
Thanks in advance.

paddydriver · 11-06-2020 08:29PM

Think longer chain may be needed and you'll likely need to change the cage on rear derailleur or new derailleur - have a look at below link and might help:

https://guides.wiggle.co.uk/rear-derailleurs-buying-guide#:~:text=The%20distance%20between%20the%20upper,move%20to%20the%20smaller%20rings.

Cee-Jay-Cee · 11-06-2020 08:30PM

Danville wrote: »

I am presently using Shimano 52-36 with 11-28 cassette.
Can I change the rear cassette to a 12-34 with a simple swap or will it be necessary to change the chain length?
Thanks in advance.

You’ll need add two links to your current chain or buy a new one and split it two links longer than current chain.

Carawaystick · 11-06-2020 08:53PM

Will he not need it 6 links longer to go from 28 - 34 on the back?

Also check the deraileur, if the cage isnt long enough to allow the extra range

magicbastarder · 11-06-2020 09:09PM

Carawaystick wrote: »

Will he not need it 6 links longer to go from 28 - 34 on the back?

the chain only wraps halfway around the cassette, rather than all six extra teeth being used by the chain.

Danville · 11-06-2020 11:29PM

paddydriver wrote: »

Think longer chain may be needed and you'll likely need to change the cage on rear derailleur or new derailleur - have a look at below link and might help:

https://guides.wiggle.co.uk/rear-derailleurs-buying-guide#:~:text=The%20distance%20between%20the%20upper,move%20to%20the%20smaller%20rings.

Thanks for this, very informative.
I see that with a Medium Cage the state’s;
Max Cassette is 34 and
Max Capacity is 37

My capacity as per formula given is 38.
Q. Would I ‘get away with’ being out by one?

Cee-Jay-Cee · 11-06-2020 11:42PM

Shimano generally understate the max capacity. I have used a 32T cassette with a short cage 6800 RD and had no problems, I didn’t even need to screw in the B screw.

If you already have a medium cage RD then you’ll be fine with a 34T cassette so long as you lengthen your chain by 2 links.

martyc5674 · 11-06-2020 11:53PM

Danville wrote: »

Thanks for this, very informative.
I see that with a Medium Cage the state’s;
Max Cassette is 34 and
Max Capacity is 37

My capacity as per formula given is 38.
Q. Would I ‘get away with’ being out by one?

You’ll be fine- that capacity figure also assumes you’ll be cross chaining which I assume you don’t.

Wishbone Ash · 12-06-2020 08:33AM

martyc5674 wrote: »

You’ll be fine- that capacity figure also assumes you’ll be cross chaining which I assume you don’t.

Even if a rider doesn't typically cross chain, it can happen. I'd rather allow for it even if it never happens rather than be stranded in the middle of nowhere with a broken chain.

Type 17 · 12-06-2020 09:37AM

...broken chain if you’re lucky - I’ve seen a carbon frame with a shattered chainstay because the chain was too short, the rider shifted to big/big whilst pushing hard on a hill :eek:

Changing rear cassette query

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