It’s always nice to shave a few grams off your bike, but there is definitely a strategic way to go about saving weight while maintaining strength in the right places. For the weight weenies among us, Wren Sports (not to be confused with the UK’s Wren Bicycles) has produced one seriously lightweight stem, which they recommend for anything from road to MTB riding.
We received a selection of the new stems in the shortest sizes, and I volunteered to try out their 50mm model on my all-mountain bike while Zach used one for his recent Otso build. When it arrived I got a bit nervous. This thing is paper thin, uses tiny hardware and felt about as heavy as an empty soda can. Despite those initial concerns I hit the trails and after some apprehensive test laps I gained the confidence to ride full-tilt.
At the end of the test period both stems are still in one piece, though Wren did make one small (but much appreciated) change. Check out the full review and actual weights below…
Wren Sports’ alloy stems feature a 1-1/8″ steerer clamp, 31.8mm bar clamp, and come in seven lengths ranging from 40-100mm. They are available with either a 6° or 17° rise (all of ours were the 6° models). With a 50mm stem weighing just 75g, you’re probably wondering if there’s something special about its construction. Wren Sports’ stems are made from AL7050 aluminum, and are 3-D forged in specially designed molds to strengthen the metal by enhancing its grain structure. The company claims this process is superior to CNC machining.
Upon installation, I found out the stem’s tiny hardware requires a T-20 torx bit. Since I’m running a carbon handlebar, I was at my local shop borrowing their torque wrench and finding a T-20 bit and the necessary adapters was a hassle. Obviously weight was the primary concern, but I think it would have been worth a few extra grams to stick with the far more commonly used T-25.
The good news – Wren has already decided to make a running change to T25 torx bolts instead of the tiny T20s.
I would be lying if I said I didn’t worry about the strength of the stem. Saving weight is great, but a stem is not where you want to take chances with durability. Since my local trails (Whistler and Pemberton) are a lot more ‘enduro’ than XC, I was concerned enough to ride with a T-20 and a spare stem in my pack.
After installation the only adjustment I had to make was tightening the steer tube bolts before my first descent. With such thin aluminum I was afraid to over tighten these bolts at the shop, but a short climb confirmed they weren’t tight enough. With my trailside tools I can’t tell you how much torque I put on the bolts but once snugged up they held the stem tight for the rest of my test period.
This is an odd review to write, because the bottom line is that I had no issues whatsoever with the stem aside from the impending fear that it might fail – but it’s been holding strong since mid-June! Despite this, I’m still removing it from my AM bike because I can’t shake the feeling that I’m tempting fate. The stem isn’t going into retirement, however – I think I’ll enjoy the weight savings on my commuter bike.
For those riding less technical, mellower terrain this stem could be a great way to drop some weight off your 100mm XC bike. For charging down rougher trails on 160mm enduro machines it seems a bit too light-duty, and even if it’s all in my head I’d rather not take the chance of overriding this ultralight stem. The Wren Sports alloy stems come in gloss black and sell for $59.99 USD.
Zach’s Take:
When the Wren Stems came in, I was in the middle of piecing together my recent Otso Voytek build. I wasn’t quite sure what length stem I needed, so it was nice to have a selection to pull from. Ultimately, I ended up going with the 50mm (center) rather than the 40mm that I started with or the 60mm. That combined with the longer reach of the medium Voytek proved to be the magic number. For what it’s worth, all of the stems measured within 1-2g of the claimed weights on the Wren site. Not bad.
To get right to the point, in my opinion T20 bolts just don’t cut it. Fortunately, Wren seems to agree. Before I had even voiced my concerns, they (claimed) they had already made a running change to T25 Torx bolts. However, their website still lists the stems as having a T20 Torx bolt.
I will say though, that once I got the stem settled in it performed admirably for such a light weight. It never felt flexy, though I probably never pushed it past the “aggressive trail” segment in terms of riding. I’d agree that riders really pushing the limits of enduro may want to go with something more burly (though they are certified for Mountain/Enduro use for ISO purposes), but for XC, Trail, and other users looking for a super light stem that is also super affordable, the Wren is worth a look broken.
Update: After a two seasons of use, the Wren stem I was using on the Otso above failed after one of the steerer clamp bolts pulled out the threads. This did not happen while tightening the bolt, it just popped while riding the bike allowing the stem to rotate. Fortunately, it was while riding the bike in a parking lot at the trailhead, so I didn’t have far to walk (and I just happened to have a replacement stem in the car).
This was still with the T20 Torx bolts, but as noted Wren still lists the stem with T20 hardware on their site. But based on my experience with this stem, I cannot recommend it. More so, if you have one on your bike currently, I’d recommend replacing it with something else as soon as possible.
