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Shimano 2013 SLX Groupset - RD+ Mech

by Phil on 18th April 2012

Shimano held a recent press conference in Feb and sent out the subsequent press release early March. I couldn't make it to the event but having just put together a spec sheet for my new build, have had time to mull over the details rather than repost the information I'm sure you've seen already.
When I were a lad looking to get my first bike, a 10 speed had two chainrings and only 5 cogs out back. We wondered how on earth anyone could need that many gears, but still added a 10 speed to our list to Santa!

Roll on more years than I care to mention and collars might be smaller and trousers tighter at the ankles but some things don't change - 10 speed is all the rage again! Except this time we're only talking about what's going on out back. Adding one more cog to the sprocket opens up some interesting options and choices for trail riders out there.

SLX has gone 10 speed and brings a few interesting developments to the market.

Shimano Shadow RD+

The biggest improvement is the addition of the clutch as see on the XTR trail mech. The mechanics are pretty simple. On a usual mech, the lower arm is held under spring tension. When you hit a bump, the chain tries to flap and the inertia of the chain often overcomes the spring tension in the mech, leading to noisy (and paint damaging) chain slap, jumping and possibly dropping.

Shimano added a clutch to their RD+ mechs. Flicking a lever moves a cam and engages a band clutch, which effectively damps the cage movement, holding the lower jockey wheel still and keeping the chain tight at all times, making chain slap a thing of the past and giving you a truly quiet ride.



Unfortunately, Shadow RD+ is only available as 10 speed - the mechs are not compatible with 9 speed cassettes and shifters. A new cable pull ratio means you need a new cassette, mech, chain and shifter to go from 9 speed to 10 and take advantage of the RD+ clutch.

The other big decision with 10 speed is how many chainrings to run. 10 speed at the back has a couple of benefits - either a close ratio for smoother shifts or a larger ultimate gear. While the spread of gears is much improved, if you live somewhere hilly you are going to have to compromise.

Lots of DH and 4X riders are running road blocks - less weight, closer ratios and shorter chains so less slap. For 'AM' duties the option of a 36T rear opens up 1x10 with a chainring around 34 or 36T.

The big disadvantage of that is that if you live near big hills, a 34 is still quite large at the front but not very big for spinning down the road back home. However, many riders still like to run a double. For my riding in the Peaks with big hills and a few decent roads back home, a dual setup is still the one. SLX introduces a 24/38 ratio over the previous 22/26 double.

The new chainring setup makes sense - coupled with a 11-34 or even an 11-36 out back and you have a really big range of usable gears that will climb anything, no matter what weight your bike, but still get the speed up on the fire roads or tarmac.

The only problem now is that a lot of frame builders have focussed on getting the pivot optimised for 36T for the last for years. Suddenly a switch to a clutch mech needs not only a new cassette, shifter, mech, cranks but could possibly affect the pivot action of your frame!

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