Gear Ratios and Chain Sizing

[Norry1]

I've just bought a new (to me) cyclocross bike and would like to put a bigger cassette on to help me up the steep bits. The chain rings are currently 46 and 36 and the cassette is 12-28 (10 speed)

If I get a 12-30 cassette, will I need a longer chain?

Cheers

 

[festival]

Probably.
36/28 is pretty damn low and unless you are planning a tour through the alps or similar journey you wouldn't normally need lower gears.
You may also need a new rear mech as well.

 

[Norry1]

I'm planning to try cyclocross racing next year and thought I might need some easier gears.

 

[RecordAceFromNew]

If I get a 12-30 cassette, will I need a longer chain?

You don't have to guess. Use a chain length calculator. The best way to determine, imho.

 

[Norry1]

You don't have to guess. Use a chain length calculator. The best way to determine, imho.

Brilliant thank - just what I needed. This tells me the number of links is the same.

Anything else I need to watch out for? The bike is the 2012 CAADX 105

 

[RecordAceFromNew]

Anything else I need to watch out for? The bike is the 2012 CAADX 105

I think you are good to go. After swapping the cassette just make sure the top jockey still clears the 30T when shifting onto it. I think it will. If there is any doubt you can increase the clearance by turning the B screw in (clockwise). I always do this only after having taken off the spring pressure on the screw first by rotating the mech clockwise well back when it is on the small cog - else it is real easy to ruin the top of the screw since it would not only be under pressure but is usually threadlocked.

 

[festival]

If your worried 36/28 is not low enough to get you round a CX course, I think you will be best served getting some miles in ( and some cx specific training)

 

[Norry1]

Yep I could definitely do with some CX specific training - but not sure where to get it. I don't know if I need lower gears but I know steep hills in mud is pretty hard work.

 

[boydj]

You could always get a 34 inner chainring (or slightly smaller), along with the bigger rear cogs to give you even lower gearing if you have a lot of tough hills in your area. Your front mech should be able to cope with this. I don't think you'll need a new chain to go from a 28 to 30 max at the rear - as long as you avoid using the 30 with the big chainring.

 

[Peteaud]

You should be able to fit that without any issue.

 

[Rickshaw Phil]

I would replace the chain coz I don't like putting an old chain on a new cassette. Then using the big to big + 2 links method will give the correct size.