Wednesday, November 07, 2007

More Than You Really Want To Know: Inline Speed Skates

I did a bit of inline speed skating in 2001 and 2002, when I lived in Atlanta, with the local skate club. (This is the club that puts on the famous Athens-to-Atlanta (A2A) road skate.) I grew re-excited about skating in 2004 and 2005, when I lived just outside Washington, DC, so I took to skating with a couple of clubs in that area. I'm sure you can see where this is going. Yes, the skating bug has struck again, despite the fact that weather is about to turn too cold for skating.

In speed skating, the boots---the parts of the skates that looks like shoes---are low-cut, reaching just above the ankle. This height gives good ankle mobility, but it also means that the fit must be nearly perfect to allow the skater to control each skate without developing painful and slow-healing blisters. Because the fit is so important, most boots are heat moldable; the epoxy that holds together the carbon or glass fibers that make up the stiff parts of the boots is thermoplatstic. The boots can be warmed in an oven or with a heat gun until they are pliable, then reshaped using some combination of the foot, the hands, and boot stretchers. The molding process can be repeated as needed. All this carbon fiber and heat moldability makes the boots are the most expensive part of a pair of skates. The frames are the next most costly. The bearings and wheels tend to be about equal, though the wheels need to be replaced more frequently.

Anyway, I've never been completely happy with the way my boots fit, and there are limits to what can be done with heat molding. My Verducci V-Tek boots have forefoot areas that are too narrow for my feet and ankle cuffs that are too loose; no amount of heat molding can fix that.

Once again, you can see where this is going. I bought new boots: Bont Apaches. The Apaches, which are the mid-level boots in Bont's line-up have wide, square toeboxes and, since I can therefore wear a smaller size, tighter ankle cuffs. Additionally, they have small pads, one on each side of the Achilles tendon, that really lock the heal in place, preventing heal lift. They already fit much better than the Verduccis, and I haven't really heat molded them yet.

The thing is, inline-skate technology has come quite some distance since I bought my last boots in 2002, so I broke down and bought an entirely new boot/frame/wheel/bearing package:

Perhaps I should explain. This will take a little time, so please feel free to skip the rest of this post---except perhaps for the photos---and come back later, when Alison has put something up.

Here is a partial list of the parameters that determine how a skate feels and performs.
  • Wheel size. Larger wheels have lower rolling resistance. This effect makes a noticeable difference on smooth surfaces, and an even larger one on rough roads. Unfortunately larger wheels have higher moments of inertia and are thus harder to accelerate. Additionally, larger wheels inevitably increase the height of the foot above the ground.
  • Heel height. The height of the foot above the ground is usually measured to the bottom of the skater's heel. Lower heights provide more stability and require much less ankle strength. Greater heights effectively make the skater's leg longer, which can be advantageous for leverage, but, as we'll see, modern skates put the heal higher than is optimal for most skaters, so a lower height is usually desirable.
  • Wheelbase. This parameter is measured from the front axle to the rear axle and is determined by the wheel diameters and the sizes of the inter-wheel gaps. Longer wheelbases provide more stability at speed and a larger platform to push against. Shorter wheelbases are more maneuverable, but maneuverability isn't usually an issue in speed skating.
  • Overall length. The length is also determined by wheel and gap size. Longer skates can be difficult handle, especially in crossover turns.
Way back in the early days of inline speed skating, the boots where adapted from those used in ice speed skating: they had two mounting points spaced 165 mm apart. Thus, the frames also have 165-mm spacing. The standard setup was 5 wheels 76 mm in diameter with gaps of about 1 mm. With this wheel size, it was possible to more-or-less emulate the height of an ice speed skate. By the time I joined the scene in 2001-ish, the standard setup had moved from 5x76 to 5x80. My first speed skates had a heel height of about 105 mm, which seemed adequate.

Soon thereafter, people were moving to 5x84. These skates rolled better, but the height and overall length were starting to be issues for some smaller or less burly-ankled skaters.

About this same time, skaters began experimenting with 100-mm wheels designed for kick scooters. 5 wheels of this size would be way too much skate, so 4 wheels was required. With the mounting bolts spaced 165 mm apart, the front bolt was right over the second wheel, so to keep the height semi-reasonable, that wheel was made to be 80 or 84 mm. (The rear mounting bolt is usually 12 mm higher than the front.) Because there were only 4 wheels, the gaps were quite a bit larger than those of 5-wheel skates, which meant that obstacles could "fall" in between the wheels, increasing resistance on rough surfaces. These 100-80-100-100 and 100-84-100-100 setups met with enough success that lighter, speed-skate-specific 100-mm wheels reached the market.

Soon, in about 2004, 90-mm wheels became available, and various combinations like 4x90, 100-90-100-100, and even 5x90 showed up. The 5x90 skates, meanwhile, where only ever used by the biggest, strongest skaters; they were simply way to long and heavy for anyone else. My second pair of frames where 4x90, and they had uneven spacing to move the center wheel out from under the from mounting bolt. With my boots mounted on them, the heel height was 110 mm, only 5 mm higher than my old setup with a 10-mm increase in wheel size.

Around the same time, boots and frames with 195-mm bolt spacings arrived. On some wheel combinations, like 4x90 and 4x100, this spacing moved the front bolt away from directly over the second wheel, which reduced the heel height considerably. (I didn't want to buy new boots at the time, which is why I went with the irregularly spaced 4x90). With these frames, 4x100 setups became more common.

You can guess what happened next, I'll wager: 110-mm wheels hit the market.* 4x110 setups began to crop up. Eddy Matzger won A2A on a 100-100-110-110 setup that year. (I know because I was visiting Alison in Atlanta that weekend, so we skated in Piedmont Park that Sunday morning and hung around to see the finish.)

So, by 2004, almost every possible combination of wheels up to 110 mm was in use. It was mayhem. Mayhem, I tell you.

By 2005 or 2006, things had shaken out a bit. Many smaller skaters were running 4x90. Medium-sized skaters were on 4x100. Some bigger skaters were using 100-100-110-110. The biggest skaters were on 4x100. As you can guess, the heel heights on these skates were pretty substantial. People just tried to cope with it.

In 2005, Bont introduced their 3-point mounting system. This system was designed for frames with 4 wheels 90 mm and above. The system added a third mounting point between the inner wheels and pushed the other 2 mounting points out to 202 or 216 mm, depending on boot size. This move not let the boot drop down---drape down, really---over the wheels, it also reduced the amount of material and thus weight---required to give the boot the required stiffness. One other, smaller advantage to this scheme was that it moved the pitch (the difference in height between the front and rear mounts) off of the frame and into the boot: the frame's three mounting points are all at the same height, so the boot can be designed with any amount of heel lift. Incidentally, I should mention that Bont calls their 3-point frame the Space Frame or S-Frame.

I was sold on the 3-point concept the first time I saw it, but the rather significant downsides associated with it where (a) I'd have to pony up the dough for boots and frames and (b) my choices of boots and frames would be limited to a single brand.**

Recently, 2 years later, when I decided to get back into skating, I came to the conclusion that, since I've gotten 6 and 5 years out of my previous boots, I could go ahead and get a complete 3-point package. The Apache is the middle-of-the-range boot, as I said, but the Apache package comes with the range-topping S-Frame, the one made from magnesium alloy.*** The frame I have is has a 12.5-inch wheelbase. (Yes, I know I'm mixing units here, but wheelbases are usually Imperial for some reason.) The package also comes with some grippy-but-heavy Hyper Stripe 100-mm wheels.

Here's a photo comparing my schmancy new 4x100 setup next to my older 4x90 and 5x80 skates. This photo gives some idea of the difference in wheels size between these skates. The pic also shows the difference between the new 3-point mounting system and the traditional 2-point, 165-mm mounting. (Well, it doesn't show the contrast too clearly. I need to take a better photograph.) Sharp-eyed cyclists will notice that all 3 boots use Sidi Ultra SL buckles. Hey, why re-invent the wheel?

To better illustrate the contrast between these wheels sizes, here's a photo of wheels with diameters of 80, 90, and 100 mm. I must say, those 100s seemed huge when I first put them on. Especially since my feat are only 242 mm long.

Speaking of those ginormous wheels, they are a bit of a, footfull? The heel height is about 116 mm, 6 mm higher than my last setup with 10-mm larger wheels. I think my ankles will eventually be able to cope with that height, but it will take some time and practice. My double-push technique---good slow-motion sequence halfway through this video---has never been great, and I'm going to have to work to make it as strong on 100s as on 90s. Let's just hope I can adapt before I start skating with the club in Baltimore next Spring.

I think 100 mm is as far as I can really go. I don't think I'm large or strong enough to push 4x110, and even if I where, the minimum wheelbase is 13.2 inches, and the minimum overall length is 403 mm, both of which are very long for a guy who wears 29x28 or 29-30 pants. I might try 4x104, since it appears that I can fit Hyper's 104-mm wheels on my current boot/frame combo; there's at least 2 mm between wheel and boot and 4 mm between wheels. I suspect I will return to 100 mm, though. I won't rule out trying 110 mm if I ever feel comfortable with 100 mm, but I'd have to spring for a 110-mm-specific frame to do it, so it won't happen soon.

Meanwhile, some skaters are already talking about 3x120 or 3x125 as the next step. Perhaps the 165-mm spacing will return, triumphant. Who knows?

Wow, that was a much longer post than I originally intended. I do tend to run off at the fingers, don't I?

* Actually Hyper makes at least one model of 104-mm wheel, but they are the only brand to offer one, as far as I know.

** Bont has offered to license the 3-point system to other manufactures, so others could make compatible boots or frames, but I don't think any of those products have reached the market yet.

*** The vast majority of speed-skate frames are made from aluminum (or aluminium, if you prefer) alloy.

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