Shimano Dyna-sys, 10 speed XT and SLX

[UPDATE: Shimano XT Dyna-Sys 10-speed review here]

10 speed on mainstream MTBs has been on the cards for a while. First it was SRAM with XX being 2x10, then they announced X7 would 10 speed. Now Shimano has finally entered the ring, electing to go 3x10 with its ubiquitous SLX and XT groupsets. Called Dyna-sys technology, let's take a look to see if there's anything more to it than just adding an extra cog to the cassette.

SLX and XT are going 3x10

As of June 2010, XT and SLX will be offered as 3x10 speed groupsets, retaining triple chainsets and moving to a 10 speed cassette - the new system has been called Dyna-sys. Don't fret though, 9 speed will continue to be offered alongside the 10 speed variety, for now at least.

Dyna-sys Technology

So what does Dyna-sys and 10 speed mean to you?

Shimano are claiming to have reduced shifting friction, made closer shifting ratios and increased power transfer. They are talking about reduced chain tension, reduced power loss in rear suspension bikes, and a reduction in cadence change and pedalling shock (those very big, uncomfortable jumps in gear you sometimes make such as 32/32 down to 22/32).

As well as adding an extra cog to the cassette, ratios across the whole cassette and chainset have been tweaked. Cassettes are now being offered 11-34 and 11-36 (11-32 will be offered eventually), chainsets are coming with more compact ratios of 42-32-24. So what we're looking at here is a wider range of gears on the cassette, with the extra cog minimising the gap in ratios - but then decreasing the jump in ratios on the chainset. Obviously when you suddenly drop a cog on the front before a climb, it should be a smoother transition in cadence - and the bigger cassette will offset the increase in granny ring size. Sounds good so far!

In addition to this, there is the idea that the new range of gears on offer will allow for similar ratios but with less tension on the chain. The example they give shows a 9 speed rider riding in 22/25 (a ratio of 0.88) and a 10 speed rider pushing the same ratio of 0.88 using 32/36 - they're turning the same gear but the 10 speed rider has less tension on the chain.

Benefits to full suspension bikes come in the form of the more compact chainset. Many suspension bikes are optimised for one chain ring, usually the middle, with pedal feed back and chain growth usually exhibited more strongly in the inner chain ring. By offering a more compact crankset, the outer and inner rings are close in ratio to the middle ring, hopefully offering less of a compromise in performance when using those chainrings.

The 10 speed MTB chains now inherit the directional technology from the top end 10 speed road chains - each of the four plates being optimised for front and rear shifting.

When will we see it?

As mentioned, it should be hitting the shops around June. We're hoping to get an SLX or XT Dyna-sys group around late May and will report back our early thoughts.