A good portion of Fox's success in the high end fork market can be contributed to its FIT damper. Lighter riders and those of us who like supple suspension tunes, however, have complained that Fox's FIT4 dampers are too heavily damped in the initial stroke. Fox has addressed this with a running change that includes a smaller diameter, eight-millimeter shaft, a lighter shim stack, modifications to the rebound circuit and a reconfigured FIT bladder. Reportedly, the new damper assembly also saves 35 grams and Fox assures us that their new tune retains the mid-stroke support that we have come to depend upon.
Fox plans to upgrade all of its non step-cast forks (36, 34 and 32 FIT4 forks) with the new cartridge as a running change and will also offer it, along with the roller bearing shock eyelet kit, as aftermarket options. It's a positive step for Fox and an opportunity for existing FIT4 fork owners to stay current without having to pony up for new ones.
The aftermarket roller bearing kit came on the heels of that announcement and should make a lot of riders happy. Technically, roller bearings are the best option for highly loaded, slowly rotating applications - and they take up very little real estate compared with ball bearings. Sealing slender-profile roller bearings from the elements, however, has been problematic.
Fox seemed to have solved the sealing issue with eyelet inserts that look like tiny headset cups. They house larger diameter bearings with full contact seals. Fox says that no special tools are needed to install the roller bearing kit, but you'll probably need their extractor tools to remove it. The kit retains for $30 and the extractor tools cost $110 USD.
Roller bearings are housed in machined, press-in cups.
Official Fox Press release:FIT4 Damper Upgrade & Roller-Bearing Shock Hardware Kit
Fox has implemented an important update to model year 2020 forks equipped with the FIT4 damper, and also introduces a new, low-friction roller bearing shock mounting hardware kit. Read on for more details....
2020 FIT4 Damper Update On the compression side, all 2020 FIT4-equipped forks now feature an 8mm damper shaft, new bladder construction, and a reconfigured shim stack. The 8mm damper shaft has a smaller cross-sectional area, therefore it pushes less oil through the base valve, allowing for less damping. The updated FIT4 damper provides more sensitivity while also maintaining low-speed compression support during aggressive riding, giving riders the ability to tune their fork to feel playful, aggressive—or both.
The rebound side implements Fox's latest tuning improvements through a wider opening check valve and a reconfigured shim stack. The new FIT4 damper assembly construction is lighter as well, with an average weight savings of 35 grams.
This update is implemented on all 2020 FOX 32, 34, and 36 non-Step Cast fork models featuring FIT4 dampers. Step Cast fork models received this damper makeover in MY19.
In its fourth generation, the patented FIT4 closed cartridge system provides three on-the-fly compression damping positions—Open, Medium, and Firm—to adapt to varying trail conditions. Factory Series forks feature 22 clicks of low-speed compression adjust in the Open mode, allowing riders to fine-tune their exact damping preferences. FIT4 is the damper of choice for riders looking for a lightweight fork with lockout and loads of performance.
The roller bearing kit (right) can be installed without special tools, but Fox says you'll need their tool kit (left) to remove it correctly.
Roller Bearing Shock Hardware Kit Also new for 2020 is an 8mm x 30mm roller bearing shock mounting kit (part# 812-06-096-KIT). Deploying outboard-mounted full complement roller bearings—as opposed to standard bushings—allowing the shock to move more freely as the frame cycles through its travel. Roller bearings reduce friction and improve performance to such a degree that, in some cases, more rebound damping and/or low-speed compression damping may be needed in order to compensate for the decrease in friction.
The roller bearing shock mounting kit is compatible all current Fox shock models and it is also compatible with many popular brands such as Santa Cruz, Transition, and many others. A special tool is needed to remove the bearing kit from the shock—Mounting Hardware Bearing Assy Install and Removal (part# 803-01-406). For installation instructions, click
HERE.
To verify compatibility of this kit with your bike, please visit your local bike shop or call FOX customer service for additional assistance.
Fox Service West
38 Isidor Court Suite 120
Sparks, NV 89441
800.369.7469
Fox Service East
95 Underwood Rd
Fletcher, NC 28732
800.369.7469
It came out so gloriously and right away FOX was gone from all stock bikes with CaneCreek DB's replacing them... lol
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Fox: Yeah let's introduce a couple of extra proprietary tools that if NOT used, voids all warranty.
Deep groove ball bearing 6900-LLU-MAX-ENDURO - 10x22x6 mm
It's about time to stop confusing the customers!
Speed sensitive has nothing to do with your riding speed, if that's what you meant.
"Technically, roller bearings are the best option for highly loaded, slowly rotating applications - and they take up very little real estate compared with ball bearings".
Perhaps they are thinking of needle bearings in that last sentence?
A 6900 is definitely not a roller bearing. But probably still a good choice for the application since they're using the MAX version.
en.m.wikipedia.org/wiki/Rolling-element_bearing
However, only bearings which use rollers can be called “roller bearings”. It’s that whole adjective vs noun thing.
Grip2 is available in 40's.
But yes Fit4 is lighter. Would you choose a Grip2 34 if it was available? Personally... the MRP is ugly AF and what exactly does assembled and tested in the USA mean? The FOX stuff is all tested in the USA... and assembly here doesn't really mean what it used to. Especially if you're still sourcing all your parts from overseas. The sourced parts are just as important if not more so.
I'd be curious if compared directly if the MRP ribbon SL is really any stiffer than the 34. It's a 35 so in theory it should be. At 120 it's 3.94 lbs. The Factory 34 with Fit4 at 130 is 3.92 pounds... so it's not really lighter... especially if you compare 130 to 130. Believe the Fox is over 1/3rd pound lighter. And that's without a kabolt. And that's with the old Fit4 in it.....
It is cheaper though.
Suntour, Manitou, and even Fox's own GRIP has proven you don't need to spend a ton of money, or have a gazillion adjustments in order to have a great damper.
The fact that Vorsprung and Push are selling out of their coil conversion kits also shows how much air spring technology is lagging behind damper tech.
I weighed my Fit 34 with kabolt and mudguard that the ribbon SL replaced. Travel doesn't matter since the stanchion is there regardless of travel. THe weight difference is negligible, the stiffness gain is real, and the MRP performance blows the 34 out of the water. Not a fan boy, just an engineer that has ridden and understands both subjectively.
The aftermarket (ie vorsrprung et all) have taken fox’s stuff and turned decent forks into what they should be for the $$$ for reasonable money.
The rwc kit is a proper roller bearing and also works very well, but you have to be sure to use the correct size hardware in it or it can and will wear out prematurely.
A bushing deals far better with the sudden high loads (if you bottom out a 3" shock w/ 450lb spring you get roughly 3000N of load on each bearing, without counting the peak when hitting the end of travel and damping forces) and if you choose the right fit, it runs very smoothly too. For looser fit, you'll obviously have to change them more often compared to tighter ones, but realistically you buy a pack of 10 for 20€ and you're happy for years to go, changing them is a matter of a few minutes.
I put the RWS kit on two bikes and honestly didn't feel a lick of difference.
I would imagine fox have tested these a little more than a back-of-a-napkin load guesstimate like you have done, no disrespect.
The article mentions full-complement bearings, which are most often cageless. The linked service manual shows ENDURO MAX bearings, which are full-complement.
Cue the down votes
patent pending!!!
Also, good job reminding us you are an engineer in the first sentence. You can keep your certs.
nsmb.com/articles/cold-weather-mountain-bike-suspension
The piston and shim stack are still "processing" the same volume of oil past - just now, a smaller shaft takes up less space in the system and displaces less of that total oil volume.
When the shaft volume is displacing oil, it's not adding any benefit. It's only moving it to a different place - in this case, the expanded space of the bladder. You very much want as little possible bladder expansion being dedicated to something that isn't providing a performance benefit.
I used to help build shocks for a custom manufacturer and we went with a 1/2" shaft over a 5/8" shaft because we could produce a more sensitive shock this way. Marketing was very much in the other camp --- you know, the old "bigger is better, look at my shaft" story...
It is a balance though. The bigger the shaft diameter, the better the seal and bushing can be, given the same materials and stack height.... Also, you do need some connecting strength usually to keep the system together. We were building mini coil over shocks so the shaft had to support the lower eye and any minor fore/aft forces due to control arm flex, frame flex, bushing wear, etc.
Suspension is a balancing act.
What they're probably TRYING to say here is - a smaller diameter shaft forces less accessory oil around in the system. Since that volume drops, damping used to control those volume spikes isn't needed to be as aggressive.
Think of a tiny little man jumping into a bath tub vs a big fat man. Except the bath tub is sealed with a flexible cover. That cover has to do a whole lot more work to keep the water contained when the fat man jumps in.
(yes - I realize my analogy is impossible if the cover is truly sealing. So instead, the tiny man and fat man must now slide in through a tube of which they are the perfect diameter to seal themselves off as they pass through)
lol this just got weird....
youtu.be/ohz8_IafGwE
Maybe it's just another case of - Pass.
I highly doubt it.
Now saving 35g on an 1800+ g fork, finally.