Both Shimano and SRAM are out to fix an issue that has plagued the mountain biking community since the beginning…chain slap. Their answer? The new rear derailleur offerings from each side of the shifting camp are now clutched/damped versions with the ability to run a tighter chainline with a flick of a switch or push of a button.
As suspension designs have changed over the years and more travel has come to XC oriented bikes, the issue of chain slap and dropping while riding has become a hot button issue for a lot of riders. While this could be fixed with a roller install like you see on almost all downhill bikes, the trail and XC crowds were not keen on the additional drag this added to chain lines. While I can see their point as increased drag equals great power output required per revolution, I always ended up just adding a bashguard and roller to my bikes for the increased protection and tighter chain line.
However, things have changed in the mountain biking industry. As carbon frames have increased in popularity, so have BB30 and similar bottom bracket setups that do not allow for the external cup/sandwich style roller setups. To get a roller setup like the MRP we have reviewed in the past, you had to have ISCG tabs on your bottom bracket which most bikes do not have. Additionally, most of the 2x cranksets do not allow for a bashguard.
Enter SRAM Type 2 and Shimano Shadow Plus…
Now with these new rear derailleur designs, you can tighten up the chain line while riding to prevent that annoying chain slap and help keep the chain on the rings while riding in technical terrain. Each of these manufacturers have implemented their own technology and the ability to turn the feature on and off at will.
SRAM clutch mechanism is a one way, needle bearing roller clutch that requires no maintenance as it is self lubricating and basically sealed. Shimano uses an adjustable friction clutch where the rider can actually dial in how much he wants the rear derailleur to not allow the chain to pull the cage forward. Either way…SRAM and Shimano are trying to help the rear derailleur from being pulled forward by the chain in technical riding situations where the suspension is as active as the chain moving.
Will this be enough to replace roller systems? We’ll see. Both technologies from SRAM and Shimano are in first gen releases to the public and from what we are hearing around the world…they work great but aren’t quite on par with a true roller setup yet. The good news – those riders that wouldn’t run a roller setup to begin with now have a viable option to get rid of chain slap, have more consistent shifting through suspension travel and prevent the chain from dropping off the rings.