Mountain bike rear derailleur Black Friday on sale

After a fall: what to replace, and with what?

A bent or broken rear derailleur is easiest to replace with the same model, usually marked on its body: RD-M5100, RD-M7120 or GX Eagle, for example. If it is missing, pick a model from the same brand, with the same number of speeds and for the same chainring setup. First, check the hanger that holds it: if it’s bent from the impact, it could misalign the new derailleur as well.

The page MTB derailleurs explains all year about adjustments, cages, and compatibilities. A new derailleur doesn’t work well with worn parts: take a look at the pulleys, the MTB chains, and the MTB cassettes involved. The MTB transmission this Black Friday also includes front derailleurs, and the page all practical covers road and gravel. A replaced model in its range can also be found in clearance, and a recent model in new arrivals.

Single chainring, double chainring or downhill: the right version

The same range often contains several derailleurs. At Shimano, the Deore comes in RD-M5100 for 11 speeds and in RD-M5120, compatible with 10 and 11 speeds, which accepts a large sprocket of 42 teeth in double chainring and 46 teeth in 10-speed single chainring. Sram has its GX in 1x11 and 2x11, with medium or long cage. The downhill has models with short cage and few speeds, such as the Sram X01 DH in 7 speeds or the Shimano Saint RD-M820 in 10.

Derailleur on sale: cage, generation, content

Before comparing two struck-out prices, check the cage, which determines the capacity, then the generation: Type 2.1, Eagle or T-Type from Sram. Look at the control, whether cable or electronic, like the XT RD-M8050 Di2 or the Sram AXS, and the content: several T-Type Eagle AXS are sold without battery and can only be mounted on a UDH frame, so a battery will be needed if you don’t have one. On an MTB, a clutch, Shadow RD+ from Shimano, keeps the chain in place on rough terrain.

Popular MTB derailleur brands from the operation

Shimano ranges from the Tourney RD-TY200 in 6 and 7 speeds to the XTR RD-M9100 in 12, including the Cues family, from RD-U4000 to RD-U6070, and the Saint RD-M820 for downhill.

Sram covers the 9 speeds with the X5, the 11 speeds with the GX, X01 and XX1 Type 2.1, and the 12 speeds with the Eagle, either cable or AXS, up to the T-Type.

Sunrace offers derailleurs with medium cage that screw onto the hanger, MX600, MZ600 and MS100 in 10 speeds.

TRP, a premium brand from brake manufacturer Tektro, presents its Evo derailleur here.

Frequently asked questions

How do I know which rear derailleur to buy?

Note down the reference of the old one, the number of sprockets, the number of chainrings, and the largest sprocket. The derailleur you choose must accept this sprocket and work with your shifter.

Switching to a single chainring, is it just a matter of changing the derailleur?

No. You also need an appropriate single chainring, often a more layered cassette, usually a new chain, and to remove the shifter and front derailleur.

Does the Black Friday for derailleurs last just one day?

No. Its name refers to the Friday after Thanksgiving, but at Vélo-Store, discounts on rear MTB derailleurs run throughout November. To assess one, compare the same reference: same number of speeds, same cage, same generation, with or without battery for an electronic model.

Does an AXS derailleur sold without a battery work?

It needs a Sram AXS battery, purchased separately or transferred from the old derailleur. Pairing with the controller follows the Sram instructions.

What is the small lever on the side of some derailleurs for?

It activates or disengages the clutch. When disengaged, the cage moves freely, making it easier to remove the wheel; make sure to switch it on before riding.