Lightweight Fernweg Review

Let me just state it for the record, and get it out of the way now. These are one of the coolest pieces of bike equipment that I’ve ever had my hands on. Having been in the industry for quite some time, and being a bike geek even longer than that, bikes get boring. They don’t excite me like they used to. It’s almost as though the required stimulus to get a “wow” response gets larger and larger. As a jaded bike guy, these things got my attention.

What am I talking about? None other than the new Lightweight Fernweg wheel set:

These beauties are a big departure for Lightweight. For those not familiar, Lightweight started in the early 1990’s as the garage-shop operation of Heinz Obermayer. His specialty was exactly what you see – a full carbon wheel. That means not only a carbon rim, but also carbon spokes and hubs. When I was growing up and really getting in to cycling, I remember seeing original Lightweight wheels under the likes of ProTour legend, Jan Ullrich. They were the coolest things ever. He would thrash these things at 70 rpm (using 177.5 cranks) and absolutely diesel his way up the mountain passes. It didn’t hurt that he had some of the lightest wheels on the planet.

Lightweight was purchased by Carbonsports in 2003, and has grown to the brand you see today. They now have a wide variety of wheel models to suit different sports and needs. What they were clearly lacking on in the past was a true aerodynamic option. Yes, their standard 53mm depth rim is undoubtedly more aerodynamic than your training wheel – but it is a narrow V-shaped rim, which we now know isn’t the fastest shape for higher wind angles or wider tires.

Enter the Fernweg:

What you have here is an 81mm depth full-carbon run. The published rim width is 19.5mm, but my calipers measured 20.4mm at the braking surface (so I suspect a typo on their part). The widest point of the rim is at rim’s inner diameter (where the spokes attach), and measured 22.4mm with my calipers. While not as wide as, say, a Zipp 808 Firecrest, it is a very similar shape. You could call this type of rim a “reverse V”, due to the fact that it is completely opposite of a traditional rim.

You see, normally a “V” rim has the widest point at the braking surface, and then it gets narrower as you travel towards the spokes. This rim is opposite – it is widest at the spokes, and narrowest at the braking surface. Sound a little odd? Well, put a tire on top of that rim, and you have a complete system that looks very symmetrical. No matter what direction the wind comes from or what part of the wheel it hits first, you can expect the rim/tire system to deal with it predictably. Not only are they optimizing the leading edge of the wheel (the tire side), but also the trailing edge (spoke side). Think of it this way: that air has to first hit the tire, attach itself to the wheel, come off the trailing rim edge and in to the spokes – and then start all over again on the rear half of the wheel. As Hed, Trek, Zipp, and others have shown us, a blunt shaped object often does better than a sharp edge, at least when it comes to keeping airflow attached and laminar. In order to roughly match the rim’s widest point of 22.4mm, I chose to use a 22mm width tubular tire – the Schwalbe Ultremo HT 700x22.

And they sure do look good together.

There are 16 spokes front and 20 rear. Ever wonder how they attach to the rim?

The rear spokes are bound together at the crossing points with extra carbon wrap. Old-school bike guys: think of it like tying and soldering spokes, only with carbon. The idea is to reinforce and strengthen the wheel.

Both the front and rear hubs are carbon.

The wheels include an accessory kit including quick release skewers, valve extenders, carbon-specific brake pads, and a nice embroidered Lightweight wheel bag. The valve extenders are the type that require a removable-core valve stem. You end up replacing the valve stem at the end of the extender, so you retain its full function. As with all valve extenders, be sure to use plenty of Teflon tape at the junctions.

The skewers look to be made by KCNC, but with a molded-in carbon lever. The action was smooth and surprisingly secure-feeling.

One of the coolest features of the wheels: both front and rear rims have a magnet molded inside. No more ugly spoke magnets for your bike computer.

So, how do the wheels work? How do they ride? I was expecting the full carbon construction to feel dead. As well, Lightweight is always touting wheel stiffness, so I expected them to be harsh over bumps. Much to my surprise, however, the wheels rode great. This is always a subjective topic, and tough to describe, so bear with me. Having ridden a lot of different wheels, I can only describe these as “very smooth”. Rough pavement was no problem, and cornering felt secure and confident. This could also be due in part to the very nice Schwalbe Ultremo HT tires; they have latex inner tubes and seemed to contribute to the great ride quality.

Braking was outstanding for a carbon rim – perhaps the best I’ve ever experienced. Lightweight includes their own special compound of pad, and I also tested the wheels with the Zipp platinum pad. Either way, you get great braking. Fortunately for me – but unfortunately for this test – I did not get a chance to test the braking in rain, so I cannot speak for the wet performance.

Acceleration was what you’d expect – fast. These wheels are light. Astoundingly light, given their depth of 81mm. Total weight is 1,355 grams per pair - 640 front and 715 rear. The first time you pick them up, your brain does a momentary double-take as it calculates the math of what you’re holding.

My personal race/travel bike has S&S Couplers, so it isn’t the lightest bike around. These wheels sure helped with that, and spruced up the looks to boot.

And what of the mechanical side of things? Tubular tire installation was uneventful. The Schwalbe Ultremos went on perfectly round and straight. The skewers worked fine. Hubs turned.

There was one problem, however. When I put a larger cassette on for a hilly race I planned to do, the inner cage of my SRAM Red derailleur brushed the spokes of the wheel while in the gear combination of big chainring and big cog. For a while, I couldn’t figure it out. What was going on? With the 11-23 cassette I had originally, the derailleur didn’t rub. With the 11-27 I put on, however, it rubbed. Derailleur hanger was straight. Chain sized properly. Nothing awry with the cassette. What was going on? While difficult to capture in photo simply due to the location of the problem, this is what I’m talking about:

A big part of your rear derailleur’s job is to manage chain capacity. The more teeth the chain has to wrap around, the more your derailleur’s springs have to wind up to manage that capacity. The most chain you will ever need is in the combination of big chainring and big cog. You’ll notice that the rear derailleur cage swings far forward in this gear. The larger the cassette and/or chainring, the more it has to swing.

It looked like the derailleur was swinging just a bit too much with that big cassette. So what was going on? Was it the wheel, was it the derailleur… maybe a bit of both? Lightweight told me that while this is not a common problem at all, they have seen a few cases of it. They simply told me that because the wheels are entirely hand-made, there is always a small amount of variability in the end product. In this case, my spokes must have gotten wrapped with just a little bit too much extra carbon. According to them, it is not a safety concern, as the spokes are much stronger than steel – but that in the case of a consumer, they would replace the entire wheel at no charge. I’ll buy that. While we can’t expect every company to have perfect product, we can expect that their customer service deals with problems honestly and quickly.

Just out of curiosity, I put a different wheel in the bike – a Zipp 808 Firecrest. On this wheel, the spokes cleared by about .5mm. This had me curious, then, about the derailleur. Shouldn’t there be more clearance than half a millimeter? Perhaps I had a derailleur cage that got over-painted in the clear-coating process? I compared to my other tri bike, which has both a SRAM rear derailleur and Zipp wheel, and it had about 2mm of clearance in the big/big combination. I inquired with SRAM, whose representative told me that they thought it was only a problem with the Lightweight wheel.

Would a Shimano derailleur clear the spokes with a large cassette? Fortunately for this test, I was actually planning to change the bike to Di2 around the same time. After the components swap, I reinstalled the Fernweg wheel with the same 11-27 cassette. In the big/big combination, the spokes and derailleur did clear each other, by about 3mm.

The take-home for this story is to check clearance of this on any combination of frame, wheel, and derailleur. With the advent of 9, 10, and 11-speed cassettes, there is not much extra room hanging out on the drive-side of our bikes. Wheel manufacturers want to put the drive-side spokes as far to the right as possible to retain wheel stiffness. What this means, however, is our spokes and derailleurs are getting very cozy with each other. Be sure your derailleur hanger is straight, as this is one quick way to ensure maximum clearance and safety. Also be sure your chain is sized properly. If it is too short, that makes the derailleur’s cage have to swing further forward when in gear combinations such as big/big. You could argue that we really ought not to cross-chain our bikes that severely, and I agree. However, the racer and athlete in me knows that in race situations, we don’t always have the time or mental capacity to think through our gear choice – so I want every possible gear combination to work safely.

What happens if you do damage your Lightweight wheel? Say, you slam a huge pothole or accidentally drive your car in to the garage while your bike is still on top (I’m sure none of you have ever done THAT). Lightweight does have a crash replacement program that offers a 30% discount for replacements. They also told me that repairs are often possible in the event of a broken spoke or similar damage.

And what about price? To be frank, the information provided to me about the wheels didn’t even mention it. I think we can all agree that the general rule applies here: you get what you pay for. Or – if you have to ask…

Lightweight’s “standard” set of road wheels starts at around $4,500, depending on the exchange rate at the time. I wouldn’t count on getting a pair of Fernwegs in the US for anything less than five grand. Now, are these wheels necessarily more aerodynamic than other high end wheels? I doubt it, but they are certainly among them. That is a big statement for Lightweight, and a big step forward for them. In the past, Lightweight always had the cool factor and (obviously) light weight going for them. Now that they’ve added legitimate aero technology to the mix, they are a serious contender for all-around performance. And – for the clincher-lovers out there, Lightweight tells me that they “are working on” a carbon clincher version of this wheel set, for launch in the next year or two…

Lightweight sure are proud of the new wheels. According to them, it was a three year R&D process that included many tests in the wind tunnel, on the track, and on the road. They tell me: “With FERNWEG, we have remained true to our LIGHTWEIGHT motto: build the best wheels in the world that combine the three key performance factors of low aerodynamic drag, low weight and maximum stiffness.” After having the pleasure of putting these wheels through their paces, I think they’ve delivered a knock-out.