Enduro 2020 Long Chainstay Kit
Updated 03-07-2026
I made a long-chainstay kit for a 2020 specialized enduro. The kit was assembled and tested on bike trails in Santa Cruz, California
Please email me if you would like to purchase a kit
Reverse engineering + Mechanical Design
The existing carbon fiber composite part geometry was measured using simple hand tools and paper templates. A few iterations of 3d printed assemblies were used to check fit of my design
A 3D CAD model is shown below of the chainstay assembly with 470RC/29 config. Using multiple bolted together components enables custom chainstay lengths and 27.5 or 29 wheel size at low cost. All the Specialized OEM spacers, bushings, screws, etc... all fit like stock--again to reduce cost. UDH is used, I bought a cheap aluminum version from China instead of SRAM plastic.
Rigidity was a risk, as a machined open section is less structurally efficient than a closed tube. I kept in mind that I always have the option of gluing high modulus carbon fiber fabric on top of the aluminum if I need more rigidity. The stock mass is 921g (2lb)
Linkage Kinematics and Bike Geometry Impact (for 470RC, Medium (S3) frame size)
Front center is unchanged from stock. Only rear-center is changed (for these parts to 470mm). Therefore new wheelbase is 1.276m
The front center/rear center ratio impacts bike handling. Stock is 806/440 = 1.83/1 and with 470 is 806/470 = 1.71/1 (6.6% change)
LinkageX3 was used to compute a baseline and new leverage curves, anti squat/rise, etc..
For 470mm rear-center parts, leverage ratio at sag increases +3.6%. To maintain same wheel spring/damping rates, increase shock spring rate by 7.3% and re-check your damper clickers. Increased leverage reduces the effect of shock friction which is good for light riders. There is also free +6mm travel increase
You should expect to need a longer chain, although the bike will be rideable with the stock specialized chain length
Parts + Assembly
CNC machined and 3d printed aluminum alloy parts were used. The quality is good and tolerances were as expected
Full complement 6801 bearings are glued in using loctite 680 glue. The 4 screws that hold on each dropout are glued with loctite 272
Riding Notes
The two notable effects of this part are less front wheel wander when climbing and very noticable cornering balance change, front wheel grip in a more centered position is much better
Feel no different in terms of stiffness to the OEM parts
Dirt may accumulate in the pocketing of the seat-stay :-)
