Fox's brand-new 2021 Transfer SL dropper seatpost has been designed to be as light as possible, shaving up to 128g off the standard Fox Transfer seatpost.
Fox claims this makes it "the lightest mainstream dropper post on the market" and suitable for cross-country mountain and gravel bikes.
In its lightest guise, Fox claims it weighs 327g and will cost $399 for the Factory version and $329 for the Performance Elite model.
It's available with 50mm, 70mm, 75mm, or 100mm of travel, and in 27.2mm, 30.9mm and 31.6mm diameters.
Unlike the standard Transfer dropper – and most other MTB dropper posts on the market – the Transfer SL has two fixed travel positions rather than 'infinite' adjustment.
Fox says it uses a two-position system to help save weight – less material is required – and that it sees no benefits for infinite drop positions in XC or gravel, where the seat is usually fully up for pedalling or fully down for technical descents.
Fox also claims the Transfer SL's mechanical actuation – where its internals are devoid of any hydraulic components – saves weight over a hydraulic system, as seen on RockShox' Reverb dropper. Also, the remote and post are joined with a cable rather than a hydraulic hose, also seen on the Reverb.
Not only does removing the need for hydraulic internals reduce weight – there's now "empty space where oil would exist" – it also does away with tight-tolerance sealing, required to keep the oil where it needs to be.
The seals also increase a post's weight and add to the amount of friction required for it to raise and compress, which is where the next weight-saving trick from Fox comes in.
A coil spring provides the force required to return the seatpost to its original height. Fox says using a highly preloaded, low-rate coil spring provides enough force to return the post at a quick rate. Had it used a hydraulic system this wouldn't have been possible.
Although the brand admits air springs are lighter than coil, it says this is limited to suspension applications where heavier coil springs – in both weight and rate – are required to support rider weight.
This has also allowed Fox to reduce the amount of sealing required even further.
The post's seat clamp is compatible with both 7mm seat rails and 7x9 Ob-round rails.
The post is compatible with Shimano's GRX-style dropper levers for drop-bar bikes thanks to a window in the post's body that allows for cable adjustment.
It's also available with a 1x mountain bike lever that's SRAM Matchmaker, Shimano GRX and I-Spec EV compatible.
