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11-30 cassette to 11-34
#1
Ciao.
1. My road bike currently has 11-30t CS-HG31 8 speed cassette, but I'd like to have one that is a tiny bit better for biking up the hills. Would 11-34t do the work? Can I go with the same cassette model CS-HG31 and its 11-34 version or is there a better option? Are there any concerns in terms of compatibility? I know that these are simple questions, but I'm simply exhausted from studies and can't go through with the research Confused Thanks.

2. How difficult is the cassette swapping process considering that I'm a bike repair newbie?
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#2
(05-14-2020, 09:41 AM)ManBearPig Wrote:  Ciao.
1. My road bike currently has 11-30t CS-HG31 8 speed cassette, but I'd like to have one that is a tiny bit better for biking up the hills. Would 11-34t do the work? Can I go with the same cassette model CS-HG31 and its 11-34 version or is there a better option? Are there any concerns in terms of compatibility? I know that these are simple questions, but I'm simply exhausted from studies and can't go through with the research Confused Thanks.

2. How difficult is the cassette swapping process considering that I'm a bike repair newbie?
I know of no reason why you can't use the same model with the larger cog. A 34T cog will certainly make it easier to go uphill. Apart from a wrench to remove the axle nuts, you'll need a cassette removal tool and a chain whip. The chain whip is necessary because you can't unscrew the retaining ring with the removal tool without the whole cassette turning. I turn the bike upside-down, remove the axle nuts and then, pulling the derailleur cage backward, lift the wheel out. You could remove the chain but I prefer to simply pull the cage of the derailleur back so the cassette is free to be lifted out with the wheel.

I recently changed a Megarange freewheel on my cruiser that had 34 teeth. The cogs jumped from 24 to 34, a huge jump. It's okay if you like pedaling at speed and hardly getting anywhere, or if you intend to climb hills, but I ride on the flat all the time. So I swapped it for a 14-28T freewheel. The thing is, the chain length was made to work with the 34T cog, but now I was reducing to 28T, six teeth less. This meant shortening the chain by two links. In your case, you may have to lengthen the chain to accommodate the larger cog, but you may get away with your chain as is. There are videos to help you calculate the chain length.

It's probably best to put the bike up on a work stand if you try your chain as is, so when you turn the pedals and operate the shifter to change to the next bigger cog, you can watch the chain as it moves up, and won't damage the derailleur at the largest cog by forcing it if the chain is a bit short.

Incidentally, cassettes don't usually come in one piece like a freewheel. They come in pieces such as three cogs, two cogs, two cogs and one cog, and a spacer. If you haven't done one, before, make sure you get the spacer in the right place. New cassettes usually come on a plastic peg. Cut the zip ties and carefully remove the sets of cogs and spacer, so that you assemble it on the freehub with the spacer in the right place. When it's done, you'll know it's done right by the spaces between the cogs; they will all be equal.
If I knew how to ride a bike properly, I'd do it every time.
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#3
@CharleyFarley very useful information, highly appreciated! I am not a top level athlete yet and need those extra teeth for hills that we have around here. 11-32 and 11-34 ... would two teeth make a big difference? I am afraid that after few months, once my legs are super duper fit, 34t will be pointless.

Will this work with my cassette?
https://www.parktool.com/product/cassette-lockring-tool-fr-5-2
  Reply
#4
(05-18-2020, 08:30 AM)ManBearPig Wrote:  @CharleyFarley very useful information, highly appreciated! I am not a top level athlete yet and need those extra teeth for hills that we have around here. 11-32 and 11-34 ... would two teeth make a big difference? I am afraid that after few months, once my legs are super duper fit, 34t will be pointless.

Will this work with my cassette?
https://www.parktool.com/product/cassette-lockring-tool-fr-5-2

Hi "MBP",

It would make a difference from 32 to 34 (you can do the ratio math), but if you are going to do any real amount of biking, you will certainly build up the muscle and be able to crank up hills with the 32. You may have to get out of the saddle for the first week or two but I think you'll be okay thereafter. If you have chronic pain from an injury, then I would suggest the larger gear just to reduce the stress on the body. I have no idea what it's like to use gears that big; mostly go up to 28t on my rear, and on my last very steep, albeit short climb (1/3 mile, approx. 900ft of elev.), I stayed in the 52t on the front. Yeah, hurt like a son-of-a-gun, but I wanted to do it the way I did it as a kid just to see if I had it in me. Also, I didn't have a front derailleur mounted so I would have had to dismount to change to the smaller ring when I hit the hill; could've done it while riding while going downhill before the climb, but I wanted the big gear to be able to keep my speed up for the ascent. I'm too old to care, I'd have gotten off and walked up if needed.
Good luck with it!

Take care,
Jesper
Take care,
Jesper

"I am become Death, the destroyer of bicycles." NJS
  Reply
#5
(05-18-2020, 08:30 AM)ManBearPig Wrote:  @CharleyFarley very useful information, highly appreciated! I am not a top level athlete yet and need those extra teeth for hills that we have around here. 11-32 and 11-34 ... would two teeth make a big difference? I am afraid that after few months, once my legs are super duper fit, 34t will be pointless.

Will this work with my cassette?
https://www.parktool.com/product/cassette-lockring-tool-fr-5-2
You was talking about going from a 30T to a 34T. That might be a bit of a stretch for your existing chain, that's why I said to put it on a bike work stand where you can turn the pedals and watch the chain as it moves to each larger cog. Or if you can support the back wheel in some other way to get it off the ground and turn the pedals to watch the chain. You might get away with two extra teeth but four could cause a problem. Personally, I wouldn't put the 34T cog on, and then ride the bike to try it out because the force of turning the pedals could do damage. I'd want to watch the chain to see what happens when it gets to the large cog.

You can calculate the difference two extra teeth, or four extra teeth would make over your 30T cog. Here is how to calculate the gear inches, plus an example of my own Elektra cruiser:

CALCULATE GEAR INCHES
Divide chain ring teeth by rear cog teeth. Multiply by tire diameter.

Example: My Elektra Cruiser - 44 chain ring teeth, divide by 28 sprocket teeth. = 40.85 gear inches. That's the distance in inches traveled by the bike for each revolution of the pedals.

So count the teeth on your chain ring and then go from there. It will tell you how far the bike will travel with the gears you are using. It's not as difficult as it may look.

Let's say you have 44 teeth on your chain ring, and you have 26" wheels. Your calculation for the current 30T will be:

Chain ring: 44 teeth
Rear cog teeth: 30
Divide 44 by 30. Multiply by 26 = 38 gear inches of travel. The bike will move 38" with each revolution of the pedals.

Now try it with 34T cog.
Divide 44 by 34 = 1.29. Multiply by 26. That's 33.6 gear inches of travel for each revolution of the pedals.


The lock ring tool should do the job you want. As far as I know, cassettes are standard mounting on the freehub, as long as you match the brand of cassette to the freehub - Shimano for Shimano. Or you might get an equivalent other brand that will fit the freehub. The splines on the freehub can be different between the brands. If you currently have a Shimano cassette on the bike, then another Shimano cassette will fit.

Let us know how you get along with your project.

EDIT: I don't know where my head was when it came to the gear inches calculation. I have now corrected it. It was way out!
If I knew how to ride a bike properly, I'd do it every time.
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#6
Thanks a million! You will hear from me later.
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#7
(05-23-2020, 07:03 PM)ManBearPig Wrote:  Thanks a million! You will hear from me later.
I don't know where my head was when I gave you the gear inches calculation. The result was nothing near the truth. I was out on my bike, just now, and it hit me that something was wrong with my calculation. I have corrected the post where I gave you the wrong calculation, and I give you the correct one here. Sorry about that.

CALCULATE GEAR INCHES
Divide chain ring teeth by rear cog teeth. Multiply by tire diameter.

Example: My Elektra Cruiser - 44 chain ring teeth, divide by 28 sprocket teeth. = 40.85 gear inches. That's the distance in inches traveled by the bike for each revolution of the pedals.

So count the teeth on your chain ring and then go from there. It will tell you how far the bike will travel with the gears you are using. It's not as difficult as it may look.

Let's say you have 44 teeth on your chain ring, and you have 26" wheels. Your calculation for the current 30T will be:

Chain ring: 44 teeth
Rear cog teeth: 30
Divide 44 by 30. Multiply by 26 = 38 gear inches of travel. The bike will move 38" with each revolution of the pedals.

Now try it with 34T cog.
Divide 44 by 34 = 1.29. Multiply by 26. That's 33.6 gear inches of travel for each revolution of the pedals.
If I knew how to ride a bike properly, I'd do it every time.
  Reply


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