Shimano rear cassette.

[Doug.]

Hello,one of my road bikes has a Shimano 105 group set.
The problem is the rear cassette has a ratio of 26 x12,the 26 tooth I find not low enough for some of the hills where I live.
I have been recommended to change to a 11 to 28 cassette,will I find the extra 2 teeth makes a substantial difference for my hill climbing ?
(The higher gear, 1 tooth less does not matter it seems that it is one of the Shimano cassette combinations readily available, 11 to 28)
Or is it possible just to change the lower gear cogs ,I seem to remember ( ? ) the lower 2 gears being joined together.
I shall be most appreciative of any advise.
Yours
Doug.

 

[RecordAceFromNew]

28T is not very different to 26T. It is less than 8%, so whether it is enough/worthwhile depends on how far you are from being able to tackle your hills.

You can find out what is the largest rear sprocket the existing rear mech/frame combination can accept by a ruler and adjusting the B screw. See this and the link for more details. With a larger rear cog you might also need a new, longer, chain, which you can assess by using a chain length calculator.

 

[Doug.]

28T is not very different to 26T. It is less than 8%, so whether it is enough/worthwhile depends on how far you are from being able to tackle your hills.

You can find out what is the largest rear sprocket the existing rear mech/frame combination can accept by a ruler and adjusting the B screw. See this and the link for more details. With a larger rear cog you might also need a new, longer, chain, which you can assess by using a chain length calculator.

 

[Doug.]

Thank you for the reply.
I can get up the hills with the existing cassette..........it's just upon reaching the brow of the hill I feel that a heart attack is about to happen !
Thinking that with a more "sympathetic" bottom gear I may be able delay my ticker "conking out".
Warmest regards
Doug.

 

[accountantpete]

I think a 28 would certainly help on an individual hill but if there are a lot of climbs in a ride then you may need to look at changing the chainset to give you a bigger comfort margin.

 

[Norry1]

I have 105 and I went from 12-27 to 11-28 and I thought the difference was worth having. I changed when the cassette needed changing anyway - so no real cost of change.

 

[Doug.]

Thank you all for the replies I am most grateful for the advise and guidance
Based upon the "home work and readers advise" I shall change to a 28 tooth bottom gear cassette.
It might well be more advantageous to have even more teeth on the cassette but I am informed that I would then have to change the mechanism from a short to a medium/ long mech.
Once again thank you all.
Yours
Doug.
.

 

[Peteaud]

Thank you all for the replies I am most grateful for the advise and guidance
Based upon the "home work and readers advise" I shall change to a 28 tooth bottom gear cassette.
It might well be more advantageous to have even more teeth on the cassette but I am informed that I would then have to change the mechanism from a short to a medium/ long mech.
Once again thank you all.
Yours
Doug.
.

Going to a 28 should mean you can leave the chain length as it is, but be wary of it until you know its ok.

The actual max tooth has more to do with the rear mech position rather than the cage, for instance i am running a 12-30 cassette on a Tiagra rear mech (9 speed) and it works well, ive even managed to get a 32 on and working but was right at the limit, (Giant defy) but it depends on the hanger.

28 should give you an easier time, so go for it.

 

[Banjo]

I have Shimano 105 changed rear cassette from 11/25 to 11/28 made a noticeable difference on big hills .All works fine but I did fit a new (longer) chain at the same time .

Severe damage can be done If the chain is too short and you accidently go into a large chain ring/large rear cog combination (I know you shouldnt but who hasnt at least once? )

 

[SteveJoe]

Go for it Doug! I swapped my Tiagra 10-speed 12-28 for a 12-30 with no problems at all, and the benefit to climbing was noticeable. Last weekend slipped on an 11-32 ready for a particularly hilly Sportive coming up, again with no problems. I think that's probably the outer limit though!

 

[Doug.]

Thank you all for the replies.
Doug.

 

[Peteaud]

Go for it Doug! I swapped my Tiagra 10-speed 12-28 for a 12-30 with no problems at all, and the benefit to climbing was noticeable. Last weekend slipped on an 11-32 ready for a particularly hilly Sportive coming up, again with no problems. I think that's probably the outer limit though!

9 or 10 speed?

 

[Doug.]

10 Speed.

 

[Peteaud]

Giant Defy 2 2012 model came with 10 speed 12-30 cassette as standard.

So do a few other makes / models.

 

[HLaB]

My bike came with a 105 (12-25) cassette and I swapped that for a SRAM (11-26) and found the extra gears at either end (even though just one tooth) pretty noticeable. I've just had an Ultegra (11-28) delivered (it was on offer) for if I do any longer/ steeper stuff next year.