34 front 28 rear should that be enough?

[lutonloony]

As per the title really. Haven't been beaten by any hills yet, but feel I would like an "emergency" spin gear. Trouble as I see it is that shimano 105 5800 ss has max 28 with 33 capacity. I sort of understand 28 max but not sure I fully grasp the 33. Get the fact that it is difference between small small and bg big, but if I never run full cross chain is this number relevant? So I guess the question is can the 28 max be squeezed any higher?

Not sure if this should be in maintenance ?

 

[Spiderweb]

Presuming you have a short cage rear mech then the max you can fit is a 30T without swapping the derailleur.

 

[lutonloony]

Presuming you have a short cage rear mech then the max you can fit is a 30T without swapping the derailleur.

Yes it is short cage
not sure that 1.21 vs 1.13 is really going to be that noticeable..

 

[doog]

Increase the cassette to a 30T should be enough to get you anything, just adjust the B screw.

You will notice the difference, trust me.

 

[huwsparky]

Yes, there is a noticeable difference for sure. I thought with a compact chainset you could get away with a 32t cassette just about?

I've used a 32t with a medium cage personally. It makes long hilly rides a lot easier having an easier gear to spin. Personally I don't keep the 32t on normally as it does negatively impact the rest of the cassette IMO.

 

[lutonloony]

Increase the cassette to a 30T should be enough to get you anything, just adjust the B screw.

You will notice the difference, trust me.

Next dumbass question, do I need new cassette, or can I just buy single sprocket, and swap out? Apologies for being a lazy git and not hunting answer on tinternet

 

[goody]

If you haven't been "beaten by any hills" yet then stick with what you have if you fit a smaller gear you'll end up using it. Are 11-30 11 speed cassettes readily available?
FWIW I was out Sunday with a mate riding next to each other on the same climb he was on 34-32 I was on 36-28 riding next to each other same speed his cadence was a bit higher than mine but not massively. I think the steepest bit was 15%.

 

[Dogtrousers]

As per the title really. Haven't been beaten by any hills yet, but feel I would like an "emergency" spin gear. Trouble as I see it is that shimano 105 5800 ss has max 28 with 33 capacity. I sort of understand 28 max but not sure I fully grasp the 33. Get the fact that it is difference between small small and bg big, but if I never run full cross chain is this number relevant? So I guess the question is can the 28 max be squeezed any higher?

Not sure if this should be in maintenance ?

Yes it is relevant. Because you could run big-big. "Oh but I don't" you may say. Yes, but you could. You could just forget. If you had, say, a 32T big sprocket, your mistake would push your RD beyond its capacity and could damage it. (I don't suppose it would as the stated capacity probably has a margin for error). So your setup is potentially dangerous.

If, however, you had a long cage RD your "mistake" would cost nothing whatsoever, it would work perfectly fine in big-big.

Edit - and if you had your chain too short, your "mistake" could have really serious consequences.

As to your other question, can you push the max sprocket size? Yes, or so I've read, but I've never done it as I always run long cage RDs.with high max sprocket

The solution is: Run the right mech for the job. Get yourself a 32T max and a long cage RD. You know you want to.

 

[huwsparky]

There's a big difference between the two gears you have mentioned @goody. The difference is massive just having a 32t on a compact vs a 28t let alone a semi compact.

 

[Dogtrousers]

There's a big difference between the two gears you have mentioned @goody. The difference is massive just having a 32t on a compact vs a 28t let alone a semi compact.

Indeed. 34/32 is 28" and 36/28 is 34" That's a lot.

We had a big discussion about the difference between 32T and 28T sprockets recently here.

 

[Lee_M]

well for a start the 105 5800 can run to 32 on the cassette, as I have it on my synapse winter bike - and that comes as the default configuration.

also the different sizes do make a difference but it depends on your physique and capability. I'm nearly 55 , and reasonably fit, but I'm also 6' 3" tall and weigh 15 stone so what I can get up on a 28 is much less than a 10 stone 20 year old!

I put a 30 on my summer bike last year as I was struggling up some of the hills in north wales and it made a huge difference between getting up and walking. This year I can do a lot more, but I still use it occasionally.

So I suppose the answer is do what you want, and don't be put off by anyone who starts willy waving about how anyone can get up anything on a 25 with a standard crankset as it just ain't true, as they'll find out when they get older :-)

 

[lutonloony]

Indeed. 34/32 is 28" and 36/28 is 34" That's a lot.

We had a big discussion about the difference between 32T and 28T sprockets recently here.

thanks for the link

 

[lutonloony]

well for a start the 105 5800 can run to 32 on the cassette, as I have it on my synapse winter bike - and that comes as the default configuration.

also the different sizes do make a difference but it depends on your physique and capability. I'm nearly 55 , and reasonably fit, but I'm also 6' 3" tall and weigh 15 stone so what I can get up on a 28 is much less than a 10 stone 20 year old!

I put a 30 on my summer bike last year as I was struggling up some of the hills in north wales and it made a huge difference between getting up and walking. This year I can do a lot more, but I still use it occasionally.

So I suppose the answer is do what you want, and don't be put off by anyone who starts willy waving about how anyone can get up anything on a 25 with a standard crankset as it just ain't true, as they'll find out when they get older :-)

32 is sounding good

 

[si_c]

There are two 5800 rear derailleurs, the SS which has a maximum sprocket size of 28 and the GS which has 32. It's worth double checking which one you have, it should be safe to go 30 on the SS and 34 on the GS.

 

[lutonloony]

There are two 5800 rear derailleurs, the SS which has a maximum sprocket size of 28 and the GS which has 32. It's worth double checking which one you have, it should be safe to go 30 on the SS and 34 on the GS.

Guessing you missed it in OP but it is the ss according to bike spec, although I must admit I haven't checked the actual mech