01 · Bike drivetrain parts

Drivetrain parts matched to your speed count, measured in tenths of a millimetre.

Chains for 8 to 12 speed, cassettes and freewheels, rear derailleurs and hangers, bottom brackets and bearings for road, city and kids' bikes. Chains start at $24 with a quick link, cassettes at $35. Derailleurs and bottom brackets are quoted once we have the photo or the measurement that decides them.

Chains from $24Cassettes from $35Reply within 1 business day, Mon to Fri

Send your bike's details Work out chain length

Four lines

What we source for the drivetrain.

Three bicycle chains of different speed widths laid side by side

Chains, 8 to 12 speed

An 11 speed road bike chain is the single most asked-for line on this desk, and the one most often ordered wrong. Chains are matched by inner width, not by the name on the box: 12-speed runs 5.2 mm, 11-speed 5.5 mm, 10-speed 5.9 mm, and 8 and 9-speed sit between 6.5 and 7.1 mm. A narrower chain on a wider cassette shifts badly. A wider chain on an 11-speed cassette rubs the next cog and skips under load, usually about a week after it goes on.

Every chain ships with a matching quick link and a length we have worked out from your chainstay and gearing. We will not send one without that check. Nickel-plated steel for most road and city use; a coated chain is worth it on a bike that lives outside.

Speeds8, 9, 10, 11, 12
Matched byinner width, mm
Includesquick link
Lengthchecked before dispatch

Per chain with quick link; indicative from $24, confirmed in our reply

Two road bike cassettes on a dark wooden surface

Cassettes and freewheels

Sorted by freehub standard first, range second. A Shimano HG compatible cassette in 11-32 is the default replacement on most 2x11 road bikes we see, and it needs the HG 11-speed road freehub, which is 1.85 mm longer than the 8 to 10-speed HG body. Fit an 11-speed road cassette on the shorter body and it will not tighten. SRAM XDR and Shimano Microspline have their own splines and do not take an HG cassette at all.

For kids' bikes and older city bikes with thread-on freewheels we stock 6 and 7-speed freewheels and single-speed freewheels in 16 to 18T. Before quoting a bigger range we check the derailleur's max cog, because an 11-34 on a derailleur rated for 30T will not shift onto the big cog.

FreehubsHG, HG 11 road, XDR, Microspline
Common road ranges11-28, 11-30, 11-32, 11-34
Thread-on6/7-speed, single 16–18T
Checked againstderailleur max cog

Per cassette; indicative from $35, confirmed in our reply

Rear derailleur beside three replacement derailleur hangers

Rear derailleurs and hangers

A replacement rear derailleur for a road bike is chosen by two numbers: the largest cog it can wrap and the pull ratio of your shifters. Shimano 11-speed road and Shimano 10-speed road pull different amounts of cable, so a derailleur that bolts on fine can still miss every second gear. We read your shifter model and cassette, then quote.

Hangers are worse. There are hundreds of shapes, and a frame's model name is not enough because makers change them mid-run. We match hangers from a photo of the dropout, both sides, with a ruler in shot if you have one. No photo, no hanger quote. Aluminium hangers bend so the frame does not; carry a spare if you travel with the bike.

Matched bymax cog, pull ratio
Cageshort or medium by capacity
Hangersfrom dropout photo only

Per derailleur or hanger; quoted after the dropout photo

Threaded and square-taper bottom brackets with sealed bearings

Bottom brackets and bearings

Three standards cover most of what comes across the desk. BSA threaded, 68 mm shell, on most steel and many aluminium road bikes. BB86 press-fit on a lot of carbon road frames from the last decade. And square-taper cartridges on kids' bikes and older city bikes, where the spindle length matters as much as the shell.

We identify a bottom bracket by shell width and spindle, measured, not guessed from the crank name. Measure the shell across the outside faces with calipers and tell us whether it has threads. For square-taper, the spindle length is usually stamped on the cartridge body. Creaks are often a dry thread, not a dead bearing, so we will say so if that is the likelier answer.

ThreadedBSA 68 mm
Press-fitBB86
Cartridgesquare-taper by spindle
Bearingssealed, by pair

Per bottom bracket or bearing pair; quoted after shell measurement

Chain speed and width

An 11-speed chain is 5.5 mm. A 10-speed is 5.9. Not the same part.

Chain inner width by speed count
Speed count	Inner width	Typical use	Replace at
12-speed	5.2 mm	Current road groups, 1x gravel	0.5%
11-speed	5.5 mm	Most 2x road bikes since the mid-2010s	0.5%
10-speed	5.9 mm	Older road, many touring bikes	0.5%
9-speed	6.5–6.8 mm	Entry road, hybrids, commuters	0.75%
8-speed	7.1 mm	City bikes, older road, kids' geared bikes	0.75%
Single / internal hub	1/8 or 3/32 in	Coaster brakes, IGH city bikes, BMX-style kids' bikes	0.75%

Widths are the commonly published inner figures; individual makers vary by a tenth either way.

Freehub standards

Shimano HG, SRAM XDR and Microspline do not interchange.

This is the second most common wrong order. Pull the cassette or look at the bare body in a photo. The spline pattern and the body length tell us which column you are in.

Freehub body standards we stock cassettes for
Standard	Speeds	Smallest cog	How to spot it	Takes
Shimano HG (8/9/10)	8–10, some 11 MTB	11T	Splines with one wide key, body about 35 mm long	8 to 10-speed HG cassettes; an 11-speed road cassette will not fit
Shimano HG 11 road	11, many 12 road	11T	Same splines, body 1.85 mm longer	11-speed road cassettes; 8–10 speed with a 1.85 mm spacer
SRAM XDR	12 road	10T	Short threaded body, cassette screws on	XDR cassettes only; XD with a 1.85 mm spacer
Shimano Microspline	12, some 11	10T	Many fine splines, aluminium body	Microspline cassettes only
Thread-on freewheel	1, 5–7	13–16T	No freehub; whole cluster threads onto the hub	Freewheels only, removed with a splined tool

If a freewheel tool fits splines inside the smallest cog and the whole cluster unscrews from the hub, it is a thread-on freewheel, not a freehub.

How a drivetrain quote runs

From cog count to tagged bag in four steps.

Most drivetrain inquiries are answered in one reply. The ones that take two are missing a photo.

You send speeds, cassette range and chainring sizes. Count the rear cogs, read the tooth counts stamped on the biggest cog and the big chainring. Add your chainstay length if you know it, or a side photo of the bike.
We check width, freehub and capacity. Chain width against speed count, cassette against freehub, derailleur max cog and wrap against the range you want.
You get one reply within a business day. Each part with its check, an indicative price, and a hold of seven days on the number we give you.
You confirm, we ship. The chain goes out with the length written on its tag and the quick link in the bag. Nothing is charged on this site.

Drivetrain questions

What buyers ask before ordering a chain or cassette.

Can I put a new chain on an old cassette?

If the old chain was under 0.5% wear, usually yes. If it was well past that, the cassette has worn to match it and a new chain will skip on the cogs you use most. Tell us the wear reading if you have one. If you don't, we will quote both and say which we would change.

Will an 11-speed chain work on my 10-speed bike?

It will go on and it will feel fine in the stand. On the road it shifts late and skips under load. We will not quote it. Match the chain to the cassette.

Can I go from 11-28 to 11-32 without changing anything else?

Depends on the derailleur. Many short-cage road derailleurs are rated to 30T and some to 28T. You will also need two to four more links of chain. Send the derailleur model and we will tell you if it handles the range or what replaces it. Common road gearing is laid out on the road bikes page.

Who is this page not for?

Electronic groupset parts, e-bike drive units and belt drives are outside what we source. Internal gear hub parts for city bikes live on the city bikes page. Wheels and freehub bodies are on wheels.

Tell us the speed count. We'll do the rest.

Rear cogs, cassette range, chainrings, and a photo of the rear dropout. Reply within one business day, Mon to Fri, with the price held seven days.

Send your bike's details