A fellow triathlete recently asked for a better idea than messy wetsuit glue for fixing fingernail tears.
The "better idea" is to never let fingernails anywhere near the outside
of a wetsuit! This is extremely easy to accomplish, and we teach it to
every first-timer at the Thursday Open Water Bay Swim clinics.
The first thing to remember is that there is no race to put on a
wetsuit! Take your time, and focus on proper handling of the wetsuit.
The exterior of a wetsuit is quite delicate, but the inside has a fabric lining and is very
rugged. The key concept is to touch the inside as much as possible, and
avoid touching the outside.
1. We normally dry our wetsuits inside-out, so the first step is to turn it right-side-out.
2. Next, peel down the top until the openings for both legs are visible.
3. Sit down. Trying to put a wetsuit on standing up is asking for trouble.
4. Grabbing on each side of a leg hole, insert one leg until it hits firm resistance. When doing this, do NOT pull hard on the leg of the wetsuit. A firm tug should be all that's needed.
Tip: New wetsuits can be very stiff, and it takes hours of use for
the elasticity to increase. This means it can be quite difficult to get the foot
out the bottom of the leg hole. One way to ease this is to spray the
foot and ankle with lots of expensive Tri-Slide. Another way is to use a
free plastic shopping bag: Fast and easy, and it's something I never run
out of and never have to buy.
5. Push the other foot in the other leg hole until it also hits
resistance. At this point, you'll have both legs in the wetsuit, with
perhaps ten inches of wetsuit leg extending beyond the foot. This is
why sitting down is important.
6. On each leg, roll the wetsuit leg down while pulling the foot up
(along with the wetsuit). If the foot slides free, give another tug to
set it snugly. Keep rolling each leg down until you are about six
inches away from your foot.
7. Grab the rolled edge and pull until the foot pops out the end hole.
Then roll it down further and pull more until the leg hole rides over your ankle and some way
up your calf. (This extra pull is important - I'll explain why later.) Repeat for
the other leg.
At this point, you are sitting down with both feet through the leg
holes, but with lots of wetsuit around and over your legs and feet. Looking
down, the part of the wetsuit closest to you should be the rolls you were
tugging on to get your foot through the leg holes. If it isn't this way, in the words of Picard, "Make it so!"
8. On one leg, reach about 2-3 inches below the roll on each side of
your leg, pinch the loose wetsuit material, and pull just those few
inches up your leg. It should be very easy. Repeat on the other leg.
9. Go back and forth between each of your the legs, pulling 2-3 inches
on each leg, until it either becomes awkward to grab the roll and pull,
or your feet become visible.
10. If you used plastic shopping bags, reach down and pull them off your feet.
11. Now stand up, being sure not to stand on the top or arms of your wetsuit.
12. Keep doing alternating short roll-pulls on each leg until you run out of leg.
Note: As you pull the wetsuit upward, pulling may become unexpectedly difficult. No, it's not a comment on the tightness of the wetsuit or the shape of your body: It simply means the outer wetsuit is rubbing against and sticking to the inner wetsuit. Create some slack by pulling up the outer portion.
Tip: One of the most important factors in putting on a wetsuit (and
selecting one that fits) is to have it fit snug in the crotch without
being either too tight or too loose. While too tight will certainly
announce itself, you may not notice too loose until you are swimming in
cold water, and realize your wetsuit isn't keeping you warm. This is
due to the loose crotch material acting as a reservoir and serving as a
pump, forcing the warm water from your wetsuit and exchanging it with
cold, something that will happen due to incidental leg motion even if
you don't kick while swimming.
13. At this point, you should be able to see if you have too little
material available for the crotch of the wetsuit to fit snugly. If this
is the case, peel the wetsuit down each leg and repeat all the above
steps starting at Step 7. (This is why that extra tug during Step 7
can be important!)
Now it is time to get the wetsuit over the hips, something that can be a
challenge for all but the skinniest of us. Again, this gets easier as a
new wetsuit gains elasticity and conforms to your body.
14. Keep doing the same pinch-and-pull operation just below the edge of
the roll. Some may be able to make progress pinching on each side of
the hips, but others will need to use both hands on each side,
alternating back and forth, and maybe adding some Body-English.
15. It can sometimes be difficult to get the suit over the butt. Worry
not, there's a trick for that! Put both hands behind your back and
grab the wetsuit roll. Then squat down and pull HARD as you stand back
up. I've never seen that technique fail to get the job done.
16. Keep going until the wetsuit is near the middle of the ribs, or until you can't pull it any higher.
Before we
start on the arms, take a moment to check the snugness of the crotch.
It will either be just right, or there will be some extra material
gathered there. To move the extra down toward the ankles, just push
your palms against each side of each leg, and smooth the excess down to
your ankles. No pulling or fingernails are required, and this is the only time it should be necessary to touch the outside of your wetsuit.
17. The arms can go much like the legs, but if you are lucky, a plastic
bag on each hand will permit it to go completely through on the first
try. If not, you'll need to do a one-handed pinch-and-pull on each side
of your arm until the wetsuit is up to the elbow on each side. If
there is someone nearby who knows this technique, they can help you get
the arms up much more quickly.
18. Getting the shoulder into the wetsuit comes next, and there are a
few ways to do this. The lucky folks just extend both arms straight up
in the air, and everything just pops into place. Other folks will need
to roll the collar down, then grab above the shoulder and pull it over.
Then there will be a few who need assistance, where a helper reaches
between the wetsuit and your arm to stretch it slightly, then will pull
it up over your shoulder. And some will need to do all the above, in whatever order works best.
As with the crotch, it is important to get the wetsuit snug against the armpit,
without having folds of material there when you arms are at your side.
If you can't get snugness without folds, then add a minimal amount of
gap by smoothing the wetsuit down your arm (like you may have done with
the legs) until the folds go away.
19. Next comes the zipper. While some folks can do this on their own, don't even consider it until your wetsuit has lots of hours on it (and elasticity): Pulling too hard on the zipper is the #1 cause of wetsuit damage. Pinch your shoulders backward, and get a bystander to pull the zipper up.
20. Finally, the collar. If it is too loose, it will permit cold water to flow into your wetsuit. If it is too tight, it will be acutely uncomfortable. The best is to have it barely tight enough to keep the water out. It may take a few test swims and adjustments to find where this point is. And if you are new to swimming with a wetsuit, it will always feel too tight for your first several swims. Don't worry: You will adapt, and the right collar adjustment will eventually feel right as well.
I know this sounds like it is a very long procedure, but believe me, it gets faster and faster with practice, and as the wetsuit gains elasticity.
Eventually, you will be in a situation where you will need to put on a wet wetsuit. Most will tell you this is simply not possible, or is more hassle than it is worth. But they'd b e wrong! The above technique even works when the wetsuit is soaked! It may take slightly more time, but if you are patient, it will work even then.
It is very likely that the above verbal description has left some you absolutely confused. If you'd like to help me either take some photos to add here, or even to make a video, please let me know!
Friday, June 29, 2012
Friday, June 1, 2012
TitanFlex Di2 & Bike Math
I did another 30 mile ride on my TitanFlex Ultegra Di2, and with better preparation I saw better performance. I still rode hard and fatigued myself, but there was no bonking this time. I rode up that last rise into Del Mar at an average of 11 mph, almost a 50% improvement, and finished only 3 minutes behind the group leaders. (Many thanks to the stop signs and lights that slowed them down to closer to my speed.)
My goal for this ride (aside from finishing with less embarrassment) was to see how best to take full advantage of the Di2 capabilities. I leaned one Big Thing, and one Little Thing.
First the Little Thing: It is so fast and easy to pick up or drop lots of gears with Di2! I practiced simultaneous shifts, and never came close to a bad shift. I clicked the buttons as fast as possible to select the front and rear gears without waiting for the shift to complete, then relieved pedal pressure for a moment until the derailleurs became quiet. I can press buttons far faster than I can twist a lever, and the time to shift was amazingly short, significantly faster than I had expected, or even hoped for. I'd estimate multi-gear shifts happen nearly twice as fast as before.
Now the Big Thing: Front shifts are now the same as rear shifts! This means there is absolutely no need to stay on the current chainring and use a gear ratio that's "close enough" if there's a slightly better gear ratio available on the other chainring. This means that it is now well-worth knowing the order of the gear ratios across all chainring/sprocket combinations, and knowing how to get from one to the next.
And that leads us to the Bike Math portion of this post. Let's look at what one pedal stroke does: One rotation of the crank causes the chain to pass through the number of teeth on the current chainring. Since the chain isn't elastic, that means the same number of teeth must pass over the currently selected sprocket in the rear cassette, which in turn causes the rear wheel to rotate.
Let's take the example of my granny gear: 34 teeth in front, and 28 in the rear. How many times will the rear wheel rotate due to one full pedal stroke (one full crank revolution)? We know that the chain will have been pulled forward by 34 teeth after one revolution of the crank. When the chain moves 34 links forward, the first 28 links will cause one rear wheel revolution, and the remaining 6 links will cause just under 1/4 of a revolution of the rear wheel. The precise number of revolutions is 34/28 = 1.21 revolutions.
And that's our formula to convert front strokes to rear wheel revolutions: Divide the number of teeth in the front chainring by the number of teeth in the rear sprocket. This number is called the gear ratio.
But how far will that one full turn of the crank make us move? We know that each full rear wheel rotation moves us forward by an amount equal to the circumference of the rear wheel. But what is the circumference of our rear wheel?
Don't worry: There's no need to measure the diameter of the rear wheel then use trigonometry or equations with Pi in them! Every tire has its "ISO size" on it, which consists of 2 numbers separated by a dash, or it may be written as a fraction. My tires have an ISO size of "23/622". And the ISO specification gives the circumference for each size, which in my case is 214 cm, or 2.14 meters, which is a hair over 7 feet. I got this number from one of Sheldon Brown's excellent web pages.
So how far forward do I go for one turn of the crank in my granny gear? We know the rear wheel rotated 1.21 revolutions, which means I moved forward 7 x 1.21 = 8.47 feet. (It sure didn't feel like that much on that last hill into Del Mar!)
And that's another formula: Distance forward per crank rotation is the gear ratio times the tire circumference.
That's all fine and everything, but what I really want to know is: How fast was I going? I know I was pedaling with a cadence of about 90 RPM, which means my crank turned 90 times every minute, which means that during that minute the rear wheel turned 90 multiplied by the gear ratio times the wheel circumference of 7 feet to give us our forward motion. So our speed was 90 crank revolutions per minute x 1.21 rear wheel revolutions per crank revolution x 7 feet per rear wheel revolution.
This is getting too hard to say in words! Let's try using an equation to restate all the above in a more condensed form:
Well, a value of 762.3 feet/minute is what comes out of the equation, given the units we've been using. Let's convert it to the more familiar units of miles per hour:
A speed of 8.66 miles per hour is very close to what my Garmin reports, so it seems the math actually works! We can't expect an exact match, since things like tire wear and inflation pressure affect the effective circumference of the tire. But this value is certainly useful as-is.
Now that we've calculated the speed we expect to see for a given cadence when using a specific chainring and sprocket, what about the other gear ratios associated with all possible combinations of front chainrings and rear sprockets? With 2 in the front and 10 in the rear, that's 20 total combinations. Let's figure them all out!
I have a compact crankset that has front chainrings with 34 and 50 teeth. My rear cassette is an 11-28, which contains 10 sprockets with the following tooth counts: 11, 12, 13, 14, 15, 17 19, 21, 24 and 28. The speeds listed assume a 90 cadence.
Hmmm... It seems that there is some redundancy in my system of gears! The combinations of 34/19 and 50/28 have nearly the same ratio, and the combinations of 34/13 and 50/19 have ratios differing by half a percent. That means that out of our 20 gear combinations, only 18 of them are truly unique.
It gets worse: The range of ratios on the large chain ring have substantial overlap with the range of ratios on the small chain ring: The upper 7 ratios on the small ring overlap with the lower 5 ratios on the large ring! With the overlap removed, we are left with no more than 15 non-overlapping gear combinations!
However, this overlap is to be expected, given the wide tooth range on my rear cassette. A cassette with a minimal tooth range, such as 12-23, is called a "corncob", and will have much less overlap, sometimes none at all, depending on the front chainring selection.
Fortunately, not all the gear combinations in the overlap zone are wasted: Several of the overlap ratios on the large chainring fit nicely between those on the small chainring. Let's sort the above table by ratio and see how it looks. I'll also add the sprocket number for later use.
This list shows why I picked the chainrings and cassette I did: I get to have a great granny gear (34/28) while still having one top-end gear above 30 mph (50/11). Well, I didn't quite pick them that way: That's just how they turned out, since I picked the widest front and rear tooth-count ranges that the Ultegra Di2 derailleurs can accommodate. There are wider cassette and chainring ranges available, but they aren't Di2-compatible.
Sorting the list places the redundant ratios next to each other, making their similarity easier to see. Notice too that, except near the redundant ratios, the overlapped ratios ping-pong back and forth between the front and rear chainrings.
The overlap zone ranges from a speed of 14.91 mph up to 22.13 mph. This happens to be the speed range I spend the vast majority of my time in. Let's see what it would take to use these gears.
Let's say I'm hammering at nearly 24 mph in gear 50/15. (Hey, that is hammering for me!) I'm starting to tire, and I'd like to ease up just a bit. The next lower ratio is 34/11, which is on the other chainring, and 4 rear shifts away. And if I tire a bit more, the next ratio down has me switching chainrings again, then doing 5 rear shifts.
With a manual shift system, that would certainly be way too much shifting for way too little gain, but with the Di2 it is just a total of 5 button clicks for the first and 6 clicks for the second. And that's as bad as it gets: The other gears within the overlap are fewer shifts apart. Let's make a table of the front and rear shifts needed to get through all the ratios in-order,skipping whichever redundant ratio makes for less shifting:
50 19 (7) 2.63 18.84
50 28 (10) 1.79 12.78
It is interesting to see that minimal shifting is obtained by dropping the redundant ratios on the large chainring.
So, I now have a shift list, and since it looks pretty random and hard to memorize, I'll want to have it with me while riding, which means I'd probably want to tape it to my handlebars or wear it on my wrist. A small hassle, but certainly do-able.
But there is one other factor to consider: I always need to know which rear sprocket is in use! Since there is no gear indicator, that means I'll either have to remember, or more likely I'll have to take a look back before deciding which shift is needed.
I'll give it a try to see if it is worth the effort.
My goal for this ride (aside from finishing with less embarrassment) was to see how best to take full advantage of the Di2 capabilities. I leaned one Big Thing, and one Little Thing.
First the Little Thing: It is so fast and easy to pick up or drop lots of gears with Di2! I practiced simultaneous shifts, and never came close to a bad shift. I clicked the buttons as fast as possible to select the front and rear gears without waiting for the shift to complete, then relieved pedal pressure for a moment until the derailleurs became quiet. I can press buttons far faster than I can twist a lever, and the time to shift was amazingly short, significantly faster than I had expected, or even hoped for. I'd estimate multi-gear shifts happen nearly twice as fast as before.
Now the Big Thing: Front shifts are now the same as rear shifts! This means there is absolutely no need to stay on the current chainring and use a gear ratio that's "close enough" if there's a slightly better gear ratio available on the other chainring. This means that it is now well-worth knowing the order of the gear ratios across all chainring/sprocket combinations, and knowing how to get from one to the next.
And that leads us to the Bike Math portion of this post. Let's look at what one pedal stroke does: One rotation of the crank causes the chain to pass through the number of teeth on the current chainring. Since the chain isn't elastic, that means the same number of teeth must pass over the currently selected sprocket in the rear cassette, which in turn causes the rear wheel to rotate.
Let's take the example of my granny gear: 34 teeth in front, and 28 in the rear. How many times will the rear wheel rotate due to one full pedal stroke (one full crank revolution)? We know that the chain will have been pulled forward by 34 teeth after one revolution of the crank. When the chain moves 34 links forward, the first 28 links will cause one rear wheel revolution, and the remaining 6 links will cause just under 1/4 of a revolution of the rear wheel. The precise number of revolutions is 34/28 = 1.21 revolutions.
And that's our formula to convert front strokes to rear wheel revolutions: Divide the number of teeth in the front chainring by the number of teeth in the rear sprocket. This number is called the gear ratio.
But how far will that one full turn of the crank make us move? We know that each full rear wheel rotation moves us forward by an amount equal to the circumference of the rear wheel. But what is the circumference of our rear wheel?
Don't worry: There's no need to measure the diameter of the rear wheel then use trigonometry or equations with Pi in them! Every tire has its "ISO size" on it, which consists of 2 numbers separated by a dash, or it may be written as a fraction. My tires have an ISO size of "23/622". And the ISO specification gives the circumference for each size, which in my case is 214 cm, or 2.14 meters, which is a hair over 7 feet. I got this number from one of Sheldon Brown's excellent web pages.
So how far forward do I go for one turn of the crank in my granny gear? We know the rear wheel rotated 1.21 revolutions, which means I moved forward 7 x 1.21 = 8.47 feet. (It sure didn't feel like that much on that last hill into Del Mar!)
And that's another formula: Distance forward per crank rotation is the gear ratio times the tire circumference.
That's all fine and everything, but what I really want to know is: How fast was I going? I know I was pedaling with a cadence of about 90 RPM, which means my crank turned 90 times every minute, which means that during that minute the rear wheel turned 90 multiplied by the gear ratio times the wheel circumference of 7 feet to give us our forward motion. So our speed was 90 crank revolutions per minute x 1.21 rear wheel revolutions per crank revolution x 7 feet per rear wheel revolution.
This is getting too hard to say in words! Let's try using an equation to restate all the above in a more condensed form:
Well, a value of 762.3 feet/minute is what comes out of the equation, given the units we've been using. Let's convert it to the more familiar units of miles per hour:
A speed of 8.66 miles per hour is very close to what my Garmin reports, so it seems the math actually works! We can't expect an exact match, since things like tire wear and inflation pressure affect the effective circumference of the tire. But this value is certainly useful as-is.
Now that we've calculated the speed we expect to see for a given cadence when using a specific chainring and sprocket, what about the other gear ratios associated with all possible combinations of front chainrings and rear sprockets? With 2 in the front and 10 in the rear, that's 20 total combinations. Let's figure them all out!
I have a compact crankset that has front chainrings with 34 and 50 teeth. My rear cassette is an 11-28, which contains 10 sprockets with the following tooth counts: 11, 12, 13, 14, 15, 17 19, 21, 24 and 28. The speeds listed assume a 90 cadence.
Chainring Sprocket Ratio Speed
50 11 4.55 32.54
50 12 4.17 29.83
50 13 3.85 27.53
50 14 3.57 25.57
50 15 3.33 23.86
50 17 2.94 21.06
50 19 2.63 18.84
50 21 2.38 17.05
50 24 2.08 14.91
50 28 1.79 12.78
34 11 3.09 22.13
34 12 2.83 20.28
34 13
2.62 18.72
34 14
2.43 17.39
34 15
2.28 16.23
34 17
2.00 14.32
34 19
1.79 12.81
34 21
1.62 11.59
34 24
1.42 10.14
34 28
1.21 8.66
Hmmm... It seems that there is some redundancy in my system of gears! The combinations of 34/19 and 50/28 have nearly the same ratio, and the combinations of 34/13 and 50/19 have ratios differing by half a percent. That means that out of our 20 gear combinations, only 18 of them are truly unique.
It gets worse: The range of ratios on the large chain ring have substantial overlap with the range of ratios on the small chain ring: The upper 7 ratios on the small ring overlap with the lower 5 ratios on the large ring! With the overlap removed, we are left with no more than 15 non-overlapping gear combinations!
However, this overlap is to be expected, given the wide tooth range on my rear cassette. A cassette with a minimal tooth range, such as 12-23, is called a "corncob", and will have much less overlap, sometimes none at all, depending on the front chainring selection.
Fortunately, not all the gear combinations in the overlap zone are wasted: Several of the overlap ratios on the large chainring fit nicely between those on the small chainring. Let's sort the above table by ratio and see how it looks. I'll also add the sprocket number for later use.
Chainring Sprocket Ratio Speed
50 11 (1) 4.55 32.54
50 12 (2) 4.17 29.83
50 13 (3) 3.85 27.53
50 14 (4) 3.57 25.57
50 15 (5) 3.33 23.86
34 11 (1) 3.09 22.13
50 17 (6) 2.94 21.06
34 12 (2) 2.83 20.28
50 19 (7) 2.63 18.84
34 13 (3)
2.62 18.72
34 14 (4)
2.43 17.39
50 21 (8) 2.38 17.05
34 15 (5)
2.28 16.23
50 24 (9) 2.08 14.91
34 17 (6)
2.00 14.32
34 19 (7)
1.79 12.81
50 28 (10) 1.79 12.78
34 21 (8)
1.62 11.59
34 24 (9)
1.42 10.14
34 28 (10)
1.21 8.66
This list shows why I picked the chainrings and cassette I did: I get to have a great granny gear (34/28) while still having one top-end gear above 30 mph (50/11). Well, I didn't quite pick them that way: That's just how they turned out, since I picked the widest front and rear tooth-count ranges that the Ultegra Di2 derailleurs can accommodate. There are wider cassette and chainring ranges available, but they aren't Di2-compatible.
Sorting the list places the redundant ratios next to each other, making their similarity easier to see. Notice too that, except near the redundant ratios, the overlapped ratios ping-pong back and forth between the front and rear chainrings.
The overlap zone ranges from a speed of 14.91 mph up to 22.13 mph. This happens to be the speed range I spend the vast majority of my time in. Let's see what it would take to use these gears.
Let's say I'm hammering at nearly 24 mph in gear 50/15. (Hey, that is hammering for me!) I'm starting to tire, and I'd like to ease up just a bit. The next lower ratio is 34/11, which is on the other chainring, and 4 rear shifts away. And if I tire a bit more, the next ratio down has me switching chainrings again, then doing 5 rear shifts.
With a manual shift system, that would certainly be way too much shifting for way too little gain, but with the Di2 it is just a total of 5 button clicks for the first and 6 clicks for the second. And that's as bad as it gets: The other gears within the overlap are fewer shifts apart. Let's make a table of the front and rear shifts needed to get through all the ratios in-order,skipping whichever redundant ratio makes for less shifting:
Chainring Sprocket Ratio Speed
50 11 (1) 4.55 32.54
Shift: 0 1
50 12 (2) 4.17 29.83
Shift: 0 1
50 13 (3) 3.85 27.53
Shift: 0 1
50 14 (4) 3.57 25.57
Shift: 0 1
50 15 (5) 3.33 23.86
Shift: 1 4
34 11 (1) 3.09 22.13
Shift: 1 5
50 17 (6) 2.94 21.06
Shift: 1 4
34 12 (2) 2.83 20.28
Shift: 0 1
34 13 (3)
2.62 18.72
Shift: 0 1
34 14 (4)
2.43 17.39
Shift: 1 4
50 21 (8) 2.38 17.05
Shift: 1 3
34 15 (5)
2.28 16.23
Shift: 1 4
50 24 (9) 2.08 14.91
Shift: 1 3
34 17 (6)
2.00 14.32
Shift: 0 1
34 19 (7)
1.79 12.81
Shift: 0 1
34 21 (8)
1.62 11.59
Shift: 0 1
34 24 (9)
1.42 10.14
Shift: 0 1
34 28 (10)
1.21 8.66
It is interesting to see that minimal shifting is obtained by dropping the redundant ratios on the large chainring.
So, I now have a shift list, and since it looks pretty random and hard to memorize, I'll want to have it with me while riding, which means I'd probably want to tape it to my handlebars or wear it on my wrist. A small hassle, but certainly do-able.
But there is one other factor to consider: I always need to know which rear sprocket is in use! Since there is no gear indicator, that means I'll either have to remember, or more likely I'll have to take a look back before deciding which shift is needed.
I'll give it a try to see if it is worth the effort.
Subscribe to:
Posts (Atom)