Cassettes

Shimano 9-voudige cassette 11-34

This Shimano cassette has 9 sprockets and an 11 to 34 tooth range. The original title lists the item as I-CSHG4009134.

What you get

Shimano cassette with 9 sprockets
11-34 tooth range
Item code I-CSHG4009134

Why change your cassette?

The cassette is a wear part. Together with the chain it carries every pedal stroke. A worn chain wears the teeth, and a new chain will skip on a worn cassette. That is why you normally replace the cassette after two or three chains, or sooner if the chain was changed too late.

A different tooth range changes how your bike feels. An 11-28 has close steps and suits fast road riding. An 11-34 or 11-36 gives you more room to keep turning the pedals on steep climbs. On a gravel bike or MTB, ranges such as 10-44 or 10-52 are common, with a single chainring up front.

The number of sprockets (8 to 12) has to match your chain, derailleur and shifter. An 11-speed cassette with a 12-speed chain does not work well. The cassette must also fit your wheel’s freehub body: Shimano HG for 8 to 11 speed (and 12-speed road), SRAM XD or XDR for a smallest sprocket of 10 teeth, and Micro Spline for Shimano 12-speed MTB.

How the systems compare

The number of sprockets sets the range you can get and the freehub body you need.

System	Common ranges	Freehub body	Watch for
8 or 9 speed	11-28 to 11-36	HG, also on newer body with a spacer	Parts are getting harder to find
10 speed	11-25 to 11-36	HG, spacer on an 11-speed body	Still common on older bikes
11 speed	11-25 to 11-34 road, 11-42 and up MTB	HG (road and MTB), XD for 10 teeth	Chain and shifter must be 11 speed
12 speed road and gravel	11-30, 11-34, 10-36 and up	HG 12-speed (Shimano) or XDR (SRAM)	Do not mix brands
12 speed MTB	10-45, 10-51, 10-52	XD (SRAM) or Micro Spline (Shimano)	A 10-tooth sprocket needs XD or Micro Spline

Your wheel’s freehub body decides whether a cassette fits. Check which system your wheel has and swap the body if needed.

Choose it if

You run 9 speed and want a Shimano cassette with a wide climbing range
You want a straightforward swap for a cassette with the same 11-34 spread
Your cassette is worn, the chain skips or the drivetrain no longer runs smoothly.
Your easiest gear is too hard and you want a wider range, for example 11-34 instead of 11-28.

Choose something else if

You want one specific model from the HG range: the title only gives the item code
You do not know which freehub body your wheel has. Check first, because a wrong cassette will not fit.
Your derailleur cannot take the larger range. An 11-36 needs a medium-cage derailleur.

How to fit a cassette

Remove the wheel
Take the rear wheel off the bike. Put the chain on the small chainring to give yourself room.
Take off the old cassette
Put the chain whip on a sprocket and the lockring tool on the lockring. Turn the lockring anticlockwise and slide the sprockets off.
Clean the body
Wipe the body clean and put a little grease on the splines. Check for deep grooves left by the old sprockets.
Slide on the new cassette
The splines have one wide groove, so the cassette only fits one way. With 8, 9 or 10 speed on an 11-speed body, fit the supplied spacer first.
Tighten the lockring
Tighten the lockring with the tool to about 40 Nm. Refit the wheel and check shifting by running through all the gears.

Good to know

The exact model number is not in the title, so compare the code on the product page with what you need
You need a matching freehub and a new chain if yours is worn
Measure your chain with a chain checker. Replace it at about 0.5 percent wear (11 and 12 speed) or 0.75 percent (fewer sprockets), or you will wear the cassette too.
The number of sprockets, the chain and the shifter must match. A different count does not work well.
A wide range needs a derailleur with enough capacity. Check the largest sprocket it accepts before you buy.
With a bigger cassette you sometimes need a longer chain and a fresh B-screw adjustment on the derailleur.

What you get

Why change your cassette?

How the systems compare

Choose it if

Choose something else if

How to fit a cassette

Remove the wheel

Take off the old cassette

Clean the body

Slide on the new cassette

Tighten the lockring

Good to know

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