Review: FSA SL-K 148 wideR boost XC Wheelset

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Designing with an asymmetrical rim (around 4mm) allowed FSA to increase spoke tension by 20%, thereby cutting the number of spokes down to 24 to save weight.

What is it

A wheelset built for the mountains and more, FSA SL-K components are a mainstay in the elite and grassroots racing. That’s because the SL-K line is light enough for serious racing and durable for the abuse of day-to-day training. For 2019 the FSA SL-K wheelset received a makeover with wider, redesigned rims and boost spacing. Coming in at a reasonable $1530 and weighing in at 1500 grams, they are a serious upgrade for many cross-country riders, trail, and cyclocross applications.

  • Stiff, yet not harsh in rumble sections of trail
  • 26.1mm rim width creates an excellent footprint
  • Asymmetrical valve sculpted into the rim
  • Multiple end caps included for compatibility
  • Wheels do not come tubeless taped on arrival
  • Rear wheel needed bearing preload adjusted
  • Gloss coating scratches on rocks easily

A very cool flat valve surface is sculpted into the asymmetrical rim.

MTBRs take:

The boost floodgates opened over at Full Speed Ahead (FSA) and their most popular wheels are now boost ready, with updated rims. The popular SL-K wheelset was only available in “standard MTB” spacing using end caps to work with 135mm to 142mm rear spacing. FSA introduced the SL-K 148 wideR earlier this year, and the wheelset has quietly gained popularity amongst racers and trail riders.

The SL-K wideRs come in at 1,500g a pair with an asymmetrical 26.1mm wide and 25mm deep rim. The rim is round, yet square, giving it superb strength and compliance when in the thick of it. Designing with an asymmetrical rim (around 4mm) allows FSA to increase spoke tension by 20%, thereby cutting the number of spokes down to 24 to save weight while still maintaining stiffness. The hubs are very similar to the K-Force straight pull from last season and offer the same smooth bearing performance. Both hubs are laced with 24 straight-pull spokes in a two-cross pattern. The rear hub dons a 6-pawl aluminum freehub for quick engagement and runs on a double row of bearings. The freehub has six pawls, three of which are engaged at any given time, offering 54 points of engagement. It’s nice to see preload adjustment on the hubs as most manufacturers have cut this out and as bearing wear, the hub can become sloppy. The SL-K also arrives with “hub ends” similar to DT-Swiss that allows the user to adapt the wheels to fit many different spacing configurations.

The hubs are very similar to the K-Force straight pull from last season
and offer the same smooth bearing performance.

The wheelset required taping and setting of the valves but the process let me get more familiar with the wheels, so for that, I’m okay with it. Some riders though may prefer pre-taped and valved wheels. The rim is a gloss finish and has a beautiful flat valve platform, something that is lacking on most asymmetrical rims today. The SL-K wideR are a hooked bead style rim, something that seems to be present in more cross country designs, though many companies are going full hookless across the line. I cleaned the rim with isopropyl and tapped with the provided FSA house tubeless tape provided. The tape went on very smooth and required little stretching or maneuvering to get a solid seat. I installed a pair of Vittoria Mezcals with a basic floor pump and zero need for compressor assistance. The profile of the tire on the 26.1mm rim is narrower than my Bontrager Kovvee XXX wheelset (29mm internal), but I noticed no difference in traction or required air pressure for a comfortable experience. The SL-Ks ate up the rocky West Virginia single track and the rims put up with miles of abuse. The gloss coating on the rims allows for small scratches to appear more visible, but after hitting rim many of times, they never cracked or chipped. After a wreck on my hardtail in the rocks I decided to check the trueness of the wheel, and to my surprise, they were both nearly perfect. I did have to adjust the rear hub bearing preload early in the review for some small play. After that initial fix, the wheel has required zero maintenance or truing.

Though there are lighter wheelsets out there, for the price and durability, you really can’t go wrong with the SL-K wideR. It’s rare to find a wheelset that is race weight ready, that you can huck off some small cliffs. Highly recommended if you’re a cross-country rider that likes to hit enduro trails and take the fun line.

Rating: 4 out of 5
Price: $1530
More Info:

About the author: Jordan Villella

Jordan comes from the steep streets of Pittsburgh PA, where he learned to dodge cars and rip single track. He has been involved in nearly every aspect of the cycling industry: from turning wrenches, store design, clothing production and bike park creation. Jordan spends his free time racing cross country and cyclocross around North America, though he has been know to enduro every now and then. His love of cycling is only second to his love of his family and punk rock.

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