Trek FX 2

Tim's new bike is a Trek FX 2 Disc Gen 3. The frame was manufactured July 8, 2022, and we purchased the bike new August 3, 2024.

Model 5258273
Size: Medium
Color: Satin Viper Red
S/N: WTU189XC1606S

Chainring46/30t
Cassette11-36t
Ratio0.833 to 4.182
Gear Inches23 to 114

Tires

Michelin Protek Cross
Labeled 700x35mm, but the ETRTO size is 37-622. These are the same times that were on the Sirrus the whole time Tim rode it. After wiping out with the H2 Comp tires, Tim wanted to go back to these. They have an aggressive "city" tread, with a 1mm anti-puncture layer. Weight: 740g. Michelin has stopped making tubes for this, so I have stocked up on Bontrager 700x35-44mm tubes with 36mm Schrader valve. Weight: 140 grams.
Bontrager H2 Comp 700x35mm
These are the tires that the bike came with. The are basically thick center slicks with a little more texture on the sides. Tim seemed to like them until he wiped out on a paved trail coated with mud.

Brakes

This bike did not come with the Tektro HD-R280 brakes the web site lists. Instead, it came with Promax F1 brakes. They work okay, but they aren't great. They keep going out of alignment and rubbing.

Shimano BR-M8110: I suspect Tim will like brakes that have a prominant initial "bite", so the Shimano X series is probably a good fit for him. The XT is quite popular. The SLX is less adjustable and doesn't have a knurled lever. The XTR is lighter and silvery. Unfortunately, the 4-piston BR-M8120 won't fit this frame. However, the BR-M8110 2-Piston XT calipers use the same lever, and they come in both sizes.

Front: The front fork must be 70mm center-to-center flat mount. The distance to the axle center must be 23.5mm, so it is a 140mm flat mount.

Front Upgrade: I will need the Y8N230000 mount adapter for the front. The BR-M8110 is not available as a kit, so I need to buy the caliper, lever, and hose kit separately.

Update (Dec 4, 2025): The BR-M8100 arrived. It is 74mm Post Mount, not 70mm Flat Mount. It definitely won't work. But, it came with some of the screws I need. I have ordered another SM-MA-R160D/D mounting kit because it should come with the last screws I need to get this done.

Rear: The rear brake mount is 34mm center-to-center flat mount (through mount). The distance to the axle center must be 36.5mm, therefore the frame is designed for a 140mm rotor. To retain the 160mm rotors, I will need an adapter. The frame thickness is 21.77mm, so I will need caliper fixing screws for a 25mm frame, and install some spacers. Where do I get the spacers?

Rear Upgrade: The BR-M8110 isn't available in a kit. I will need the BR-M8110 caliper, the BL-M8100 lever, the SM-BH90-SS hose kit, and the SM-MA-R160D/D mounting kit. Screw C: 38 mm (Y8PU08020), C2: 34 mm (Y2HW08020), plus spacers.

Hmm. Related to the BR-M8120 4-Piston caliper are 2-Piston calipers. The BR-M8100 is a 2-piston caliper in what appears to be the 70mm flat mount, and the BR-M8110 appears to be the 34mm through-mount version of the same thing. Size (S) is compatible with 160mm rotors. It is quite a bit more affordable. The front BR-M8100 is on sale at Jenson for $120, but they don't have the BR-M8110. (Maybe I should call Jenson and see if their item for the rear is mis-labeled, and is actually a M8110.) The M8100 gets great reviews. I can only find the BR-M8110 as a stand-alone caliper, so I would have to get the lever, hose, separately. The reviews for the BR-M8100 are really good, even for 2-Piston. This seems to be the slam dunk set of brakes to get, if I can part it out. For the rear, do I need to get mounting kit SM-MA-R160D/D? It depends on what kind of flat mount the frame has. If it is "Ø140 / 160", then yes. If it is "Ø160 / 180", then no. So, how to identify? Oh, that's the reason for measuring the distance from the "bottom slot" to the centerline of the axle. Shit, there are different length fixing screws, too.
Brake hose (kit): SM-BH90-SS
Recommended brake lever: BL-M8100
Recommended disc brake rotor: RT-MT80

Tools: I will also need a Shimano brake bleed kit and some mineral spirit.

Update (Dec 5, 2025): I need ~15mm M5 screws to bolt the front adapter to the fork. I thought the post mount caliper came with some, but those are a different diameter. I'm also short one "screw fixing pin".

Screw fixing pin: Y8N207000
(2) Caliper Fixing Screw: Y8N204000
Snap Ring: Y8N205000

Geometry

Wheelbase: 106cm
Bike Stand-over Height: 73.8cm
Seat Tube Length: 44.5cm

Computer

The bike has a Garmin bike computer mount, which can be used with Tim's Garmin Edge 130 Plus bike computer.

Upcoming Purchases

Trek/Bontrager Tail Light & Mounts
I'd like to get Tim a tail light that can be mounted on his rack and also his bag.
Better Brakes
As of this moment (Aug 29, 2024), the brakes are adjusted well, and they aren't rubbing. We shall see how long that continues. In the meantime, I want to buy the parts to upgrade this bike to Shimano BR-M8100/8110 brakes. They should be much better brakes, and I hope they will stay in alignment.

Maintenance Issues

Broken Spoke
One of the spokes in the rear wheel is broken. I have ordered a replacement spoke and nipple.
Spoke: 2.0mm straight gauge stainless steel J-Bend, 292mm long
Nipple: 12mm silver plated brass
Tape: Intact, not needed
cycling - fitness - st. louis