I never really thought I’d have a fast XC bike again, but, I was wrong. And I’m glad. And impressed at just how capable a “modern” XC race bike is.
For almost three years I’ve had the amazing Pivot Trail 429 (v3) as my main mountain bike. It’s an incredibly capable trail bike that I’ve ridden all over the midwest, from Arkansas to Copper Harbor to Tennessee, and it’s been wonderful. But, being a longer, slacker bike the one place I wasn’t super-keen on it was our standard Lower Peninsula classic XC trails, especially those with fast, tight, twisty sections. It’s fun, but just not ideal for that stuff and felt like I had to dump the front end into the really tight corners.
In late 2022 I unexpectedly found myself buying a used-but-like-new super-well-equipped Pivot LES hardtail from a buddy (price I couldn’t pass up) which once again gave me a taste of a proper XC bike. While I used it for lots of local rides, and both Ore to Shore, and Lumberjack 100 in 2023, it never quite clicked. I had an absolute blast riding it, especially on the smooth sandy trails in the northern LP, but maybe due to the lack of dropper or the 100mm fork or my weird body proportions, it was fun and fast but never quite felt like mine. I liked having it around, and it was fun, but I was routinely eyeing other XC bikes.
When Pivot announced the v3 of the Mach 4 SL in 2023 it looked really appealing, but I couldn’t justify it. I put thoughts of a new bike aside… Until now. After a lot of thinking and basically coinciding with my birthday, a brand new Pivot Mach 4 SL v3, Pro XT/XTR build with carbon wheels, in the eye-catching Seafoam Green, found it’s way home. (And away went the LES, passing on the good deal to a buddy who was looking for a superlight XC race bike.)
Unlike normal for me, the build is almost completely stock. It’s incredibly well equipped as shipped, so outside of contact points (saddle, grips) the only changes I made were for fit, swapping in a shorter crank and a lower-rise bar.
The bike shipped with a really nice Race Face Aeffect crankset and a 34t ring, but had 175mm arms. I’ve been riding 170mm cranks on the Trail 429 for years, rather liking it, and wanted the same on here. Pleasantly surprised to see the frame fitted with a Shimano bottom bracket, I was able to swap in an XT crankset with no extra work. After confirming with Pivot that the bike is spec’d with a 53mm chainline crank I ended up going with the 52mm FC-M8100-1 which Shimano spec’s for both Boost (148mm) and standard (142mm) rear ends. The other option was the Boost-only 55mm FC-M8120-1, but sticking with the narrower chainline improves big-cog performance, so it’s preferable if possible. The narrower FC-M8100-1 fits the Mach 4 SL v3 perfectly, with plenty of clearance around the ring and arms, works wonderfully, and was a great choice.
Chainring-wise I wanted to stay with a 34t, but being (weirdly) cheap I opted for the SLX-level SM-CRM75. It’s only ~10 grams more than the XT-level SM-CRM85 but can be found for around half the price ($33 vs. $59). Both have steel teeth and an aluminum carrier, and upgrading to the XT only gets an anodized spider (vs. painted) and carbon fiber (vs. glass fiber) non-load-bearing plastic bits. Thus, performance is effectively identical. Due to series colors the center spider is a little bit of a blueish grey and doesn’t match the other parts, but in the overall scheme of the bike it looks fine, and even the smallest amount of dust obscures the variance.
Where I didn’t go cheap was on the pedals… My go-to pedals are typically XT-level PD-M8100 (regular) or PD-M8120 (trail), but finding XTR PD-M9100 on sale at the price XTs would normally sell for I figured I’d give them a go. They are only marginally lighter (28g/pair), but have a smaller center that should clear dirt and debris better, and a slightly shorter stack height. But mostly, I liked how they looked, wanted to see how they felt, and wanted new pedals for a new bike. Thus far they seem good, and I don’t regret purchasing them.
Grip-wise I put aside the stock Pivot Phoenix Factory Lock-On Grips and fitted ESI Extra Chunky grips in black with generic BMX-ish screw-in bar plugs. The narrow bar plugs are only slightly larger than the bar diameter, meaning they don’t press on my hand when my hand sits at the outer edge of the bar. While the Pivot grips are excellent I prefer foam ESIs on my mountain bikes. Kristen really likes the Pivot grips, so these’ll end up set aside for her.
The stock saddle is a fairly narrow Pivot-branded WTB which just doesn’t work for me, so the 143mm-wide Specialized Power saddle (conveniently with titanium rails) from the LES is now on the Mach 4 SL.
The bike also originally shipped with a 760mm wide, 20mm rise, 5° upsweep, and 9° backsweep bar. I swapped this out for another Pivot-branded bar I’d bought from a friend earlier in the year. After cutting 5mm off of each end it’s now 750mm wide, 6mm of rise, no upsweep, and 9° of backsweep. This is in line with what I have on my trail bike and so far feels good, although I may go down to 740mm or maybe even 730mm after I ride it more.
Fitted with everything including a bell (but no bike computer), the bike is a smidge over 26 pounds. While I wasn’t focused on weight with this build, I did pay attention as this level of bike implies it’ll be fairly light, and this impresses me. While it’s obstensibly an XC bike, and my previous (the LES) was under 21 pounds, this is far more capable: 120mm / 105mm of travel, dw-link suspension, 51t cassette, dropper, etc. Not long ago this would have been called a trail bike, and I think I’d ride it on anything that I personally am willing to do.
My first ride was at Stony Creek and thus far I’m incredibly happy. The redeveloped trails here have everything from lumpy rocks to smooth trails, small drops and wood features to semi-steep rock rolls, perfect for a bike shakedown and demo. The Mach 4 SL felt amazingly fast and comfortable on everything without really trying; just simply composed. It handles the tight/twisty stuff the way I was looking for, yet still feels really good on technical features and small drops. It’s clearly not as burly and squishy as the Trail 429, but that’s the point.
Pedaling firms up the rear end while still absorbing little bumps and keeping the tire in contact with the ground. Rolling over rough spots or dropping off things just feels right. The factory tire choice of a Rekon in the front and Rekon Race in the rear is a good one, as it both rolls nicely yet still has plenty of traction to handle aggressive steering. I also think a 34t ring coupled with the 10-51 cassette will be right. (On the LES I had a 34t, but with the 46t cassette it was a bit too tall for longer climbs. This should be much better.)
I have a bit more suspension setup to do, as in the factory-recommended settings the fork’s damper is a bit noisy and feeling not-quite-right, but dialing that in will just take a bit of time. I may toss the ShockWiz on there as I typically do to try and dial things in further. But, one thing at a time.
Initial build details are as follows:
Frame: Pivot Mach 4 SL v3 (Large, Seafoam Green)
Fork: Fox 34 Factory Step-Cast GRIP SL (2025, 34, K, FLOAT SC, 29in, F-S SC, 120, Grip SL, 3Pos-Adj, Matte Blk, No Logo, Kabolt 110, BLK, 1.5 T, 44mm Rake, N/M OE – Part: 910-31-870)
Fork Axle: Fox Kabolt
Rear Shock: Fox Float Factory (2025_24, FLOAT, F-S, K, 2pos-Adj, Evol LV, Pivot, Mach 4 SL MD-XL, 190, 45, 0.5 Spacer, CM, RM, CMM, No Logo, OE – Part: 972-05-949)
Headset: Pivot Integrated Race Headset
Crankset: Shimano XT FC-M8100-1
Crank Arm Protectors: PRO Crank Protector (PRAC0144)
Bottom Bracket: Shimano BB-MT800-PA
Chainring: Shimano SLX SM-CRM75 (34t)
Chain: Shimano CN-M8100
Derailleur: Shimano XTR RD-M9100-SGS
Shifter: Shimano XT SL-M8100-IR
Shift Cables / Housing: Jagwire / Shimano OE
Cassette: Shimano XT CS-M8100-12 (10-51)
Brakes Calipers: Shimano XT BR-M8100
Brake Levers: Shimano XT BL-M8100
Brake Pads: Shimano J04C-MF (Metal w/ Fin)
Brake Rotors: Shimano RT-MT800-S (160mm)
Stem: Pivot OE Aluminum (60mm x -6°)
Bar: Pivot OE Carbon (Diameter 35mm, Width 760mm, Rise 6mm, Sweep 9° – Cut to 750mm)
Wheels: Reynolds Blacklabel 309/289 XC
Tires: Front: Maxxis Rekon 29 x 2.4WT 3C/EXO/TR (TB00017500), Rear: Maxxis Rekon Race 29 x 2.40WT EXO/TR (TB00211100)
Seatpost: Fox Transfer (31.6mm x 150mm, Original Version)
Dropper Lever: Fox Transfer Post Lever (I-SPEC EV Mount)
Seatpost Collar: Pivot OE
Saddle: Specialized Power Expert (143mm)
Pedals: Shimano XTR PD-M9100
Grips: ESI Extra Chunky (Black)
Bar End Plugs: Generic Aluminum BMX-Type (Black)
Bottle Cages:Specialized Zee Cage II (Black Gloss, 1x Left)
Computer: Garmin Edge 840
Speed/Cadence Sensors: Garmin Bike Speed and Cadence Sensor
Computer Mount: Best Tek Garmin Stem Mount, Stem Mount for Garmin Computer, Adjustable Black
Bell: ROCKBROS Bike Classic Bicycle Bell (Black)
Derailleur Hanger: SRAM Universal Derailleur Hanger
Frame Protection Tape: McMaster-Carr UHMW PE