Bigbus

I currently have 11-32 cassette and 22-32-42 chain-ring. I'm swapping out the front chain ring for 28-38-48 to give me a higher top end. My concern is that I'll be losing my granny gear. To maintain my bottom gear, I will have to swap out the 32 for a 36 if I'm not mistaken. My question is: What problems (if any) will I encounter jumping up 8 teeth without changing any others on the cassette? My plan will create a 28T to 36T jump on the rear cassette.
Thanks in advance for your knowledgeable replies.

Kontact 

It might not shift. Does your derailleur have 36t capacity?

Bill Kapaun

Wouldn't it be easier to just use a bigger largest ring? 44-46T

dsbrantjr

Many cassettes have the largest 3 or 4 cogs on a common carrier so you cannot change them.

Here is a good gear calculator tohelp you work the numbers: kstoerz.com | visual drivetrain comparison tool

Bigbus

That's a good question. Since they only offer up to a 34T cassette that I can find pre-manufactured, I'm thinking it won't. Thanks for bringing that to my attention.

Bigbus

Yes, that would probably be easiest, but I already have a complete crank assembly (28-38-48) off a bike I got for parts and plan to use it. The crank is kind of a freebie since I already got my money back on other parts off the bike.

rhenning

My wifes Bike Friday with 20 inch wheels and uses a Shimano long cage mt bike derailleur and it has never hit anything in the 10 years she has owned it. I am sure it is closer to the ground than your set up will be. Roger

Leisesturm

Those 28-38-48 cranks are a dime a dozen. Quality (and weight) can be all over the place. Are you sure the one you have is worth the trouble? I agree with the other poster, unless your present crank is a one piece pinned unit the thing to do is just change the big ring. You probably won't even have to pull the crank. You will miss the low gears more than you will miss the high ones in any case. Keep that in mind.

base2 

What is the capacity of you're derailleur? An 11-32 cassette with a 22-42 crankset is 41 tooth capacity. What you are proposing is a system needing a 47 tooth capacity. I'm not sure your current rear derailleur will work with out being severely out of tolerance.

Also front derailleurs have limitations too. I don't know of any designed to operate with a 26 tooth differential between small & big rings.

You might want to gain a second opinion before continuing.

Edit: Sorry, I misread. I was thinking about the suggestion to just swap the big ring. You SHOULD be just fine with a crank swap providing the front derailleur is moved up a bit and the new crank has the same (or nearly same) off set. You should budget a new chain into the equation. The 28 tooth small chainring will mean your current chain may be too short.

You are right, you will lose your granny gear. But Ixd ride it as is to determine if you really needed a gear so low to begin with. My guess is you won't miss it 99% of the time

fietsbob

reads like you are swapping whole cranksets rather than just buying more chainrings, for what you own. Y/N?

factories buy truckloads of whole cranksets so there is that cost advantage (even at retail) vs 3 chainrings .

I have a crank made with a 58 110 spider, fitted it with a 22 36 48 combo..
you could do similar with a 64-104 4 bolt MTB crank , If the chainrings are not riveted on.

I use friction shifters so have no Mismatch issues indexed Shimano STI seems to create.





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Bigbus

Yes, I have to swap the entire crankset as one is 5 hole mount and the other is 4 hole mount in the rings. The BB's are interchangeable though. Like Base2 suggests, I will try it with the new crank and see if I really need the lower gear or not. I've pushed my bikes up hills in the past so it won't be a first time. It is Shimano indexed shifting. The higher geared crankset is better quality than the existing one on it now and with much less wear.