FORKS
If there is one thing Tom Kellogg loves to test and write about, its bicycle forks.

General Carbon Fork Information

• Carbon blades: All of the early carbon forks and many carbon forks today use this general design.  They usually are built with a steel steerer and aluminum crown, in the case of the Kestrel - EMS fork, a steel steerer and steel crown. Other forks in this category; All of the early Time carbon forks, many Profile, Look, Wound-Up, etc.
• Carbon blades and steerer, aluminum crown:  This category of carbon forks is mostly confined to private label forks.  Early in the carbon steerer days, this was a popular approach to lighter forks until it was found that this design is quite difficult to make reliable forks with.  One exception to this rule is the carbon WoundUp fork.  With the exception of the WoundUp, this design usually results in "mid priced" forks.
• Full carbon; Usually with aluminum or stainless crown race except for Look HSC models and some Mizuno forks.
• Carbon rooting: developed by Dr. Kyu Lee in the early days of his AlphaQ fork development.  Essentially, it involves a carbon "crown" whose fibers run continuously from well up inside a steerer tube to well down inside the fork blades.  Similar to the process developed by Kestrel for their EMS fork, this type of construction uses carbon lay-ups which go from the dropout all the way up to the crown race to make the fork look of all one piece.
• Monococue; Or single piece moulding. Monocoque fork building is very dificult and time consuming. Only a few forks are built this way. The entire fork is moulded at once from the bottom of the blades to the top of the steerer. Any internal reinforcement must be moulded at the same time as the body of the fork and the steerer. Potentially, this method can produce the best combination of light weight, stiffness and ride qualities, but at considerably higher costs.

History
The development of carbon forks has taken many fits and starts over the years.  The first widely distributed carbon fork was the Kestrel EMS designed by John Mouritsen.  It used a steel steerer and crown (brazed together) bonded to a lay-up of carbon blades that fully surround the crown.  The process of overlapping carbon blade material to bond to and cover the crown continues to be used in the majority of high-end carbon forks today. Obvious exceptions include the WoundUp fork and those lower priced forks, which use pre-fabricated carbon blades glued onto aluminum crowns.

As carbon forks became more popular, a number of different fabrication techniques were developed and in some cases dropped.  Time's Equipe Pro, for example, started with a steel steerer bonded to an aluminum crown.  Then pre woven carbon and polypropylene "socks" were drawn over flexible foam blade cores up onto the aluminum crown.  Before the assembly was placed in the mold for resin injection and curing, a small piece of carbon cloth was wrapped down the front of the crown, underneath and up the back, very clean.

WoundUp continues today using a wound blade design bonded into a machined aluminum crown.  This design gives WoundUp a great deal of control over the ride and performance characteristics of their forks, more than other forks we have tested. It also makes it relatively easy for them to make up custom forks with differing brake clearances, etc.

The most popular high-end forks today use either "Full Carbon" or "Carbon Rooting" technology.  Properly manufactured carbon rooted forks give the most reliable ultra-light weight forks.  The AlphaQ "Sub3" fork in the 1" size tips the scales at 289 grams and they now offer a "2.7" version. The lightest forks, those under about 330 grams do all suffer one way or another in the control department.

Time Fork Ride and History
When Time first began to market a carbon fork in Europe years ago, we were very excited about testing it. Both Spectrum and Merlin was interested in getting another fork supplier in addition to Kinesis at the time and the Time option was exciting. After reading some good reports about the Time fork, I began testing it for possible use on Spectrum an Merlin road frames. As soon as I got on the original fork I found that it was too harsh for my tastes. It had good control characteristics, but I was able to feel every bit of the road surface. We contacted Time with our concerns and had a new prototype on my bike in less than two weeks.  (yes Time is a very responsive and responsible company).

The new version was a remarkable improvement. In talking with Jean Pierre from Time/France I found out that the "fix" was actually quite simple for Time to accomplish. The fork is made up of fiber "Socks" pulled up over a foam core. The original fork used only carbon socks while the new one had some "vectran" fiber built in. Vectran is a form of Polypropylene similar to Kestrel's "Spectra" fiber. In any case, the new Merlin/Time version did a wonderful job of insulating much of the harsh characteristics of the original fork.'As time continues to develop new forks, we’ll keep testing them.

The Alpha Q

The Alpha-Q fork, developed by Dr. Kyu Lee, was the first of the "Carbon Rooted" forks. Dr. Lee's design enabled him to reduce the weight of his forks further than others could at the time and still retain the strength and rigidity required in a high end fork. The other distinctive characteristic of the Alpha-Q line of forks is their hand workmanship. The lay-ups of their forks are simply the most beautiful in the business, period. In addition, Alpha-Q forks have become known for their superior rigidity. They are available with a variety of steerer materials, diameters and blade shapes. The standard straight bladed, 1.125" full carbon version is a very rigid, high performance fork. AlphaQ offers both heavier and lighter forks for riders of different needs along with versions designed for tandems and Cyclo-X..

The REAL DESIGN SIGNATURE HP fork

Manufacturerd for Merlin by Taiwan's leading carbon fiber fabricator, the Signature HP is NOT just another knock-off, Asian carbon fork. Merlin's engineers spent months and a long run of prototypes getting the ride and performance characteristics that we wanted designed into these forks. While they aren't a superlight fork at about 340gr, they perform a lot better than the superlight forks. I have put hundreds of training and racing miles on this all carbon fork and plan to stick with it until Merlin sends me another prototype to test. Available in four rakes, we are not limited in our frame designs by this fork.

 

 

 

 

Reynolds UL:
The Reynolds UL was developed by Tom Kellogg and Mike Lopez at Reynolds as the "new generation" of forks to come out of Reynolds over the winter of '06-'07. Tom and Mike spent about 16 months between the first concept discussions and final production. Those intervening months were spent in ID work (industrial design), process development, materials decisions, and a lot of prototype testing. Again, Tom became known to ride the "fork of the week" by the other riders in his area. During one especially intense testing period, Tom rode four different prototypes over a two week period.

The result? The UL is by far, the highest high performance Hyper Light fork ever made. With the steerer cut to 200mm, the UL weighs in at 270gr. The lightest fork which can match all of its stiffness characteristics weighs over 100gr. more. The other forks in its weight calss are MUCH more flexable both laterally and torsionally.

 

Wound up for WoundUp
The excitement at Spectrum and Merlin over the WoundUp fork is both real and well founded. It took me a few hundred meters into my first ride on the WoundUp a number of years ago to figure out that we had something special here. It took a couple hundred miles to fully appreciate the fork though. Of course my first reaction to the fork was, UGLY! In any case, it is pretty odd looking at best and downright unattractive at worst. Once on the bike though it doesn't look too bad.

Now to what the fork does. Ultimately, the single biggest advancement by WoundUp over other after market forks is the torsional rigidity of the blades and fork as a whole. Most people assume that fork stiffness is most important in resistance to lateral forces. Actually, this is not the case.  Torsional rigidity is considerably more important because sufficient lateral stiffness is very easily built into a fork while torsional rigidity is not. Try to picture what lateral forces do to a fork in the real world.  There, you have a front hub clamped onto the front drops keeping them parallel.  With that hub in there, lateral deflections will, by definition, force the blades to deflect in a "S" shape curve, not a "C" shape curve. What this means is that forks (in the real world) are about twice as laterally stiff as you feel when you squeeze the drops together. Torsional stiffness is tougher though. The front hub, as a part of the fork structure, only helps by forcing the two blades to work in tandem as they resist torsional stresses.

You might ask "what torsional stresses?" Actually, torsional stresses are not all that great, but they can really cause a fork to feel vague if not addressed. Take the Time Club fork as an example. Although it is very light and eminently comfortable, it is torsionally quite flexible.  It is a great fork for putting on the miles. The problems develop when you put it in stressful situations. For example, hairy descents and hard criterium cornering can really stress the Club. Under these situations, the Club fork will make you feel as though you are not connected to the front wheel. Indeed, it seems as though there is actually a lag time between handlebar input and bike reaction. You loose the immediacy if input.

With a good competition fork like the Reynoldsl or Real fork, this is not the case. The WoundUp is the next step. While the Real and Reynolds forks are great forks and I would not have expected anything more, the WoundUp is clearly a better high performance fork when the going gets "on the edge."

One thing to note though, Avocet type sender rings do not clear the WoundUp fork blades when used with hubs that have flanges that are far apart. A Zipp hub would be an example of one of these. You need to use a Cateye type sender (on the spokes). The dimensions for the WoundUp fall right in the middle of the standard numbers, so you can use it on pretty much any road frame. You should note that on ordering a WoundUp fork, they are now available in three different rakes, blade lengths, brake configurations, etc. If your head angle is 73 or less, I suggest the 45-degree rake version.'If its 74 or over, you should get the 40-degree rake.