Cassette Question

[Nyimbo]

Hey all,I bought an 11-34 cassette for my touring bike only to discover I purchased a 9-speed and not a 10-speed.  Rather than return it I decided to put it on my hybrid bike that is a 9-speed 11-26.  (I'm sure you can see where this is going).


I live in a VERY hilly area and enjoyed the extra gears but unfortunately the lowest gear 34 tooth locks up my chain if I happen to forget to move down to a smaller ring in the front.  I try to remember but it still seems to happen once almost every ride.


Rather than just putting back on my 11-26 cassette I thought I would order a 11-30 but see the 11-32 are the most common. [size=78%]BTW [/size][/size][size=78%][/size]The second sprocket down is a 30 tooth so I know that is ok.  [size=78%][/size][size=78%][/size][size=78%] [/size]


Ok, my question is how can I determine if a 30 or 32 tooth is the largest sprocket on the cassete I can use???


Thanks, Keith

[John Nettles]

The only way I know how to determine what is the largest rear cog is to review the rear derailleur's specs.  It should say what the max rear size is AND what the amount of difference between the front chain ring and the rear cog.  If your rear derailleur can handle the 34t, I would first add a couple of links to the chain to see how that works.
Also, I have found it is a very good idea to may just enough chain so if I accidentally do a big/big front/rear combo, I do not break the derailleur which can easily happen if there is not enough chain.  Chain is a lot less expensive than a derailleur.
Finally, since you live in a very hilly area, consider reducing your high (biggest) gear to an easier gear.  For instance, most of my bikes have a max of mid-80s gear inches as the high as once I am spun out pedaling, I am doing 22+ mph which is fine or I just coast.  This gives me much more usable gears and also doesn't require as much work for the rear derailleur to take up if I have a large chain ring.

Hope it works out for you!  John

[Pat Lamb]

I think John makes a good point; you may need a longer chain.  Going from a 26 to 34 cog is a big jump; you might just try putting a new chain (with 4-6 more links in it) and see if that works.  I'm guessing this is the problem since you can ride the bike in the big cog with a smaller chainring up front.

[RonK]

Most likely you have exceed the derailleur capacity and probably need one with a longer cage.

There is a useful article about derailleur capacity here: Derailleur capacity – what is the max my derailleur can handle?

[Nyimbo]

Thanks Guys,


With your helpful answers I understood enough to do a bit of searcing. I looked up my bikes rear derailer specs and then got the max capacity. I have a shimano Deore LX - Maximum Cassette Cog is 34 and Total Capacity is 45.
My current is setup is exactly that 34 and 45.  So perhaps since I haven't exceeded the maximum capacity I can most easily go ahead and increase the chain length and be done.

Or as an to answer my original question I can confidently use a 11-32 cassette without problem.

Anyway, I feel like I've learned something, Thanks again.