Changing from 11-28 to either 11-32 or 11-34 cassette...

[Mazz]

Current cassette is Shimano Tiagra 10 speed 11-28.
I want to get some lower gears for hill climbs. Is there much difference between Shimano HG500 11-32 and 11-34? Pros and cons of either?
Thanks

 

[roubaixtuesday]

One has a slightly lower gear but a couple of changes with a bigger ratio difference. FWIW I'd say if you're going to change at all you might as well go for the bigger change.

You need to check if your current derailleur can cope, both (1) maximum cog size and (2) capacity. It's imperative to make sure your chain is long enough to cope with big/big - if not it'll tear your drive chain apart if you inadvertently select it.

 

[Mazz]

Cancel this question, I just found this other thread...

https://www.cyclechat.net/threads/11-32-cassette-v-11-34.256314/page-2

 

[Mazz]

One has a slightly lower gear but a couple of changes with a bigger ratio difference. FWIW I'd say if you're going to change at all you might as well go for the bigger change.

You need to check if your current derailleur can cope, both (1) maximum cog size and (2) capacity. It's imperative to make sure your chain is long enough to cope with big/big - if not it'll tear your drive chain apart if you inadvertently select it.

Cheers, to answer your question, current derailleur is Shimano Tiagra. And yes I had to wipe the crud off it to reveal the name.

P.s. I don't know what you mean by capacity. If you mean the number of rings, the old and new will both be 10 speed.

P.p.s. this is for a road bike Allez with a compact chainset, if it makes a difference

 

[roubaixtuesday]

Cheers, to answer your question, current derailleur is Shimano Tiagra. And yes I had to wipe the crud off it to reveal the name.

P.s. I don't know what you mean by capacity. If you mean the number of rings, the old and new will both be 10 speed.

P.p.s. this is for a road bike Allez with a compact chainset, if it makes a difference
View attachment 722662

Capacity = (Difference in front chainrings) + (difference across cassette).

So if you have 50/34 and 11-28 that's
(50-34) + (28-11)
=16 + 17
= 33

Not all tiagra dérailleurs are the same, even within 10 speed there might be more than one, with different capacity.

You need the actual model number to check; it'll be stamped on somewhere.

If you've insufficient capacity, it's not the end of the world, but your chain may be slack in smaller combinations.

 

[Mazz]

Capacity = (Difference in front chainrings) + (difference across cassette).

So if you have 50/34 and 11-28 that's
(50-34) + (28-11)
=16 + 17
= 33

Not all tiagra dérailleurs are the same, even within 10 speed there might be more than one, with different capacity.

You need the actual model number to check; it'll be stamped on somewhere.

If you've insufficient capacity, it's not the end of the world, but your chain may be slack in smaller combinations.

Thank for the explanation.
It's an RD-4700 rear derailleur. Cheers
P.s. I plan to put on a new chain when replacing the cassette.

 

[roubaixtuesday]

Thank for the explanation.
It's an RD-4700 rear derailleur. Cheers
P.s. I plan to put on a new chain when replacing the cassette.

View attachment 722671

4700 seems to have a short and medium length ("GS" and "SS")

SS has capacity 33

https://bike.shimano.com/en-EU/product/component/tiagra-4700/RD-4700-SS.html

GS has 41

https://bike.shimano.com/en-EU/product/component/tiagra-4700/RD-4700-GS.html

The SS is also only rated to 28T maximum cassette.

You need a GS for the larger cassette (SS might work but you're a long way from the spec range).

It's likely if the bike came with a 28 you have the SS, so you probably need a new derailleur.

 

[Mazz]

4700 seems to have a short and medium length ("GS" and "SS")

SS has capacity 33

https://bike.shimano.com/en-EU/product/component/tiagra-4700/RD-4700-SS.html

GS has 41

https://bike.shimano.com/en-EU/product/component/tiagra-4700/RD-4700-GS.html

The SS is also only rated to 28T maximum cassette.

You need a GS for the larger cassette (SS might work but you're a long way from the spec range).

It's likely if the bike came with a 28 you have the SS, so you probably need a new derailleur.

Thanks for this.
From the pictures in your links, I'd say my derailleur below is probably a medium (GS).

I need to do a count of the teeth on the chainset (i think it's 50/34 but I'm not sure), then i can find out the capacity.

 

[fossyant]

The cage on that isn't as long as the one I have on my CX bike (105 though - but 10 speed and similar age) - I bought it last year and the owner had changed the mech from the medium to the long as he needed an increase in gears from the 28 to 32 for hills around Ribble Valley.

I could probably fit a 34T top to mine, but, looking at gear inch charts, it's very little difference. You'd notice 28 switch to 32 but there is a high chance the top jockey will catch the cassette - other bodges include replacing the B screw, but the cage might not be long enough to cope.

 

[Mazz]

I need to do a count of the teeth on the chainset (i think it's 50/34 but I'm not sure), then i can find out the capacity.

Yes chainset is 50/34 as I thought it was.
So the capacity is (50-34)+(34-11)=39, so if my rear derailleur is a "GS" then it should be okay 👍.

 

[si_c]

Looks to be a short cage derailleur, might be OK with a 32 but I reckon 34 is pushing it.

Swapping the derailleur for a long cage version is fairly straightforward, but it depends how much you are willing to spend - they're around £40 I think.

 

[T4tomo]

defo a short cage SS. its not just capacity its low sprocket max restriction (28T).

SS wont work with 32 or 34, a GS will.

Also wins this weeks prize for filthiest drive-chain.....

 

[Mazz]

Looks to be a short cage derailleur, might be OK with a 32 but I reckon 34 is pushing it.

Swapping the derailleur for a long cage version is fairly straightforward, but it depends how much you are willing to spend - they're around £40 I think.

Yes, it looks like a short cage unfortunately.

The exploded diagram doesn't show dimensions, but looking at the "shape" of part #10, mine looks like a short cage.

https://dassets.shimano.com/content/dam/global/cg1SHICCycling/final/ev/ev/EV-RD-4700-3889B.pdf

 

[roubaixtuesday]

Also wins this weeks prize for filthiest drive-chain.....

I'll see @Mazz and raise you my commuter (pre fettling).

A pristine drive train is the sign of someone who prefers cleaning to riding!

 

[jessand]

Mazz, get yourself over to the 'for sale' section of this forum and you'll find a nice person in Countesthorpe selling a new 4700 GS rear derailleur for £10. Just a short ride away!