Monday, December 19, 2011

Why Penn Loves His Brooks B17 (Pt 1)

This Might Play a Role
Penn threw a challenge at me last week, one that I'm going to take up here.  My task is to explain why he likes his new Brooks so much more than the generously padded saddles he used to ride.  That is to say, I am to explain the counter-intuitive truth that a thinner saddle is, as a general rule, more comfortable than a thicker, more cushy one.  This is a challenging task, especially if my reader has experience both with an ass left sore by hours in the saddle and with the inviting appearance of those giant, couch-style saddles hanging around the fringes of the bike shop.  Still, I think I'm man enough to succeed here.

I will start, though, by narrowing my general rule.  Thin saddles are preferable for serious riders who log long hours and plentiful kilometers.  If your uncle just rides down to the bar and back two or three nights a week, those wide-added and thickly upholstered seats are probably just what he needs.  He'll find them equal parts comfortable and functional; they're the appropriate tool for his job.  If, however, you want to ride over to the next county and back, this type of saddle will actually work against you.

There are two reasons that the long-distance/duration cyclist should favor the thinner saddle: compression and leg-movement.  I'll tackle them in the order I've listed, but while the second depends somewhat on the first--and tends to go entirely unconsidered by the average cyclist--both are probably of equal importance to the average rider's comfort and efficiency.

The word compression suggests why the appeal of the thinner saddle is so counterintuitive.  Most people are worried about the compression of their ass.  Left sore after their early rides, the thought of straddling a board-like wedge of plastic only seems likely to exacerbated their injuries.  This, however, is not the compression we're concerned about here; your caboose will toughen with time and mileage.  No, the problematic compression is the compression of the saddle itself.

This is a Map of Your Insides
First, a detour into anatomy.  That's your pelvis over there.  The important parts of it for this discussion are the ischial tuberosities--better known as the "sit bones."  These protuberances bear most of your weight when you sit on a narrow surface like a bike saddle, and they do a pretty good job of it.  Aside from being sturdy, they also create a tunnel for your midline soft-tissues.  I'm speaking here of all the stuff that's not bone or muscle, and not just the obvious stuff like your taint and your junk.  More importantly, sitting on your "sit bones" keeps pressure off of internal structures like veins, arteries, and nerves.  This prevents obvious discomforts like numbness and pain, but also protects against more serious problems down the road. 

More padding might seem like more protection, but this is not actually the case.  Sitting on a bony protrusions concentrates a lot of force on a small surface area.  Now, by way of illustration, take your thumb and press into something soft--the seat-cushion or pillow next to you or your flabby gut if need be.  See how the thumb sinks ever deeper, compressing what's directly underneath it while the rest of the fabric comes up to the knuckle or higher?  This is what happens with a cushy saddle, except instead of your thumb, you're pressing down with 50% or more of your body weight.   This forces all of that comfy, cushy material you thought would help you up into your soft tissues, increasing pressure not only on your otherwise-engaged muscles, but negating that nice protective tunnel created by your sit bones.

Now, press your thumb against the surface of your desk.  Mushes the skin between your bone and the desk a little more, but there's nothing up around the knuckle to compress it or impair its motion.  This is the key difference.  Imagine you're at the gym doing curls with a barbell; if someone came along and sat on your bicep while you attempted the lift, you would not do very well.  If they stayed there long enough to numb your hand, you'd be angry and concerned.  The soft material of the thick saddle is a guy sitting on your leg muscles.  Literally.  The guy is you.   

The Other Guy is Your Perineum
This brings us to leg movement, our second concern.  Riding a bicycle well requires swinging your upper leg through something like 90 degrees of motion.  This is why a bike saddle doesn't look like a tractor seat.  While a tractor seat is more comfortable for sitting in, you can't swing your leg through the necessary range of motion in one.  Thicker saddles are also generally wider, something that makes them more like tractor seats and impairs leg movement.  This leads to less power, lower efficiency, and problems with rubbing and chafing.  All of these are obviously bad if you're trying to go more than a few miles or miles per hour.

But even if your thick saddle keeps to a narrower profile, it still impairs your leg motion.  This is because towards the bottom of the pedal stroke, your upper leg will have to compress all that material at the leading edge of your saddle.  Again, this can lead to problems with chafing, but it's also a bear for efficiency.  As though gravity and wind resistance didn't impair forward progress enough, having to compress a chunk of high-density foam at the end of every pedalstroke adds a totally unwelcome bit of additional resistance.  A tiny, tiny amount of resistance, to be sure, but if you're rolling out with a cadence in the mid-90s, that's a lot of cumulative effort.  And a lot of opportunity for chafing, too.  The thinner, narrower cut of the enthusiast's saddle goes a long way towards alleviating these problems.

Follow all that?  Thinner saddles:
  • Keep material from compressing your working muscles.
  • Keep material from compressing your soft and sensitive tissues.
  • Keep material from interfering with your leg's range of motion.
  • Prevent chafing.

So what happens if you remain sensitive to the vibration of the road?  Different saddles do provide different levels of compensation for vibration.  Look into saddles with titanium or carbon fiber rails.  Look for a saddle with a more flexible shell under it's thin layer of fabric.  Look for a saddle with a thin gel pad.  Try a suspended-leather hammock like a Brooks.  Saddle selection requires a lot of trial, error, and cashflow

If you are having problems with the jarring impacts of cycling, there are gear-based solutions.  Mountain bikers can look at seatposts like the Thudbuster.  Roadies can look at the sprung saddles in the Brooks line.  Everyone can look at running bigger tires and getting out of the saddle more.
Note The THIN Saddle

This Must Solve Some Kind of Problem

And still, amazingly, after all of that, I find I still have more to say about why Penn so loves his new Brooks.  Come back next week and we'll talk about saddle width. 

BONUS EXPLANATION:  The same thing that leads cyclists to search out thick saddles similarly leads them to seek thick chamois in their shorts.   You will not find a high-end, pro-style pair of shorts or bibs with a thick chamois, though, for the same reason to the absence of thick saddles in the peloton: too much material causes more problems than it solves.

The point of the chamois in your shorts is not to provide cushioning, but to manage moisture, friction, and heat.  (An expensive chamois  will also claim to help with microbes, but I remain suspicious of those claims after the third time through the wash.)


  1. Thanks Val, most informative. So, why not ride on a piece of wood, as was the practice in the 1890s?

  2. This post is a winner, Val: entertaining and informative. Good work!

  3. Ahhh! It all make sense now. Thanks for the enlightening explanation, Val. My ass feels better already.


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