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Old 09-04-05, 12:14 PM   #1
FarHorizon
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Why fat folks can't get a comfortable saddle

Having tried just about every saddle on the market ("Easy Seat," comfort saddles, Specialized Body-Geometry, Brooks B-17, Brooks B-69, etc.) I still haven't found one that is comfortable for more than about 1.5 hours at a time. I think I've finally figured out why:

A typical bicycle racer weighs about 150 pounds. A typical bicycle seat has only a few square inches of seat area, of which only the three square inches under the sit-bones are pressured to any extent. With a 150 pound racer, the three square inches of saddle being used are seeing a pressure of 50 pounds per square inch (the 150 pound total weight divided by the three square inches of sit area).

If we assume that 50 pounds per square inch is close to the maximum comfortable pressure for longer periods of riding, consider what happens when a 250 pound person sits on the same bicycle seat: The "loaded" part of the seat (and of the behind) are now seeing more than 83 pounds per square inch (the 250 pound total weight divided by the three square inches of sit area). This is 166% of the maximum comfortable pressure!

Note that these weights per area are static weights and do NOT take into account the acceleration forces that happen when the bike hits bumps or potholes.

What this means is that no matter what saddle you get - the more you weigh, the sooner you'll become sore.

In fact, the maximum time for comfortable riding can probably be quantified as well:

150 pound rider X max comfortable ride time = 250 pound rider X 1.5 hours (personal estimate)

Using this formula, even a 150 pound rider would get saddle sore after about 2.5 hours of continuous riding. There may be some acclimitization and other "booger factors" to take into account, but it seems roughly right.

How does this estimate correlate with your experience, and what do you think of this theory?
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Old 09-04-05, 12:21 PM   #2
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- spent several hours on a Brooks saddle this morning, but no problems... (i use a B17 and B17 Special; the stock B17 is 'softer' out of the box, IMO, but the Special is comfortable to me w/no break in)...

- some folks are built differently and may require a prescription seat?

- one could also try some of the larger seats?
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Old 09-04-05, 01:22 PM   #3
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Quote:
Originally Posted by FarHorizon
the more you weigh, the sooner you'll become sore.
The more you weigh the sooner you'll become a number of things -- sore is only one of them.

Of course this theory presumes 'fat' people have the same surface inches as less 'fat' people, and that the entire body weight is centered on the seat, rather than distributed between the seat, bars, and pedals.
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Old 09-04-05, 01:47 PM   #4
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Try a cruiser saddle by Giant. They make a real nice one.
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Old 09-04-05, 02:55 PM   #5
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I think you're probably "more or less" right. (As some old professor I once had said, "it's a zeroth order approximation"). I've heard pro's say that every year they have to get re-acclimated to the saddle. Everyone is sore for a while.

Over the years, I've found that I like a thinner saddle rather than a thicker gel saddle. I think the gel spreads the pressure over a larger area, while the thinner saddle gives me more intense pressure on my sit bones. It may be that 80 psi on the sit bones is preferrable to 60 psi on the taint. I may be able to handle higher pressure than 50 psi (I think I've weighed between 200 and 230 my entire cycling "life") and maybe personal pressure tolerance is the big variable.

My new bike (the Airborne) has a thicker saddle with a cutout. My trek has a Selle Italia Flite that is pretty thin and hard. Not quite like riding a 2x4, but compared to the Airborne's it is.



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Old 09-04-05, 11:41 PM   #6
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Ya, I hear what you're saying. Assuming your figure of 3 square inches is right, I'm putting 100 lbs on each inch - at least at the beginnings of a cross-country marathon. My biggest problem wasn't the sit bones, as much as it was chafing - I would actually bleed at times and could hardly walk at the end of a day. My second summer of riding I solved my problem pragmatically (I don't care what it looks like, as long as it works) - I simply added a 3" very solid foam pad to the sit bones area (another good use for duct tape!), then covered it with a stuff sack to keep it from soaking up rain water. Not only did my chafing stop, it was downright comfortable -- in fact in the morning when I get on for another long day, I've caught myself saying, "Ahhh, this actually feels good!"

So good in fact that I've been able to put on 12,000 kms (solo) in the past 3 summers -- not too shabby for a big ole fat guy!
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Old 09-05-05, 12:23 AM   #7
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FarHorizon, your logic seems a little off to me. Yeah much equipment is geared for light guys, but not all is.

Further, you are forgetting that some of your weight is supported by your feet and your hands. If you have good position, and you move aroung, ride standing up occasionally, things should go better.

If you've had troube with seats, try some really good shorts with extra padded chamois. I've found they make a difference.
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Old 09-05-05, 04:13 AM   #8
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I think that your presumption that fat people can't get a comfortable saddle is wrong. I have spent many hours in a saddle without a problem. I remember in past days when people would complain about sitting in a wooden pew on Sunday morning. In both cases, you just have to work up to it.
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Old 09-05-05, 06:24 AM   #9
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Quote:
Originally Posted by jabike
I think that your presumption that fat people can't get a comfortable saddle is wrong. I have spent many hours in a saddle without a problem. I remember in past days when people would complain about sitting in a wooden pew on Sunday morning. In both cases, you just have to work up to it.
I agree. I rode the stock saddle on my Giant Sedona DX for 3 years now, 1900 miles. It has done fine. I have had occasional chafing, especially after breaks, but I have heard that the pofessionals have chafing as well. I have weighed between 300 and 365 pounds during that time. I have also been riding a bike with a relatively upright position which should accentuate any problems with the saddle.

I would fear issues with any attempt to increase area that is exposed to pressure on the seat, since it could inhibit movement which would probably actually lead to more pain and/or less efficiency. But if someone finds something that works for them, then I think it is great.

However, I recently wore cycling shorts for the first time on my Giant dual-density foam saddle, and felt even better than usual.

BTW, as far as the earlier estimates of time comfortable in the saddle. I ride up to 3 hours (at 300 pounds) and any issues after a ride tend to be oncentrated in the legs and shoulders, not sit bones (although on a long ride there is some tenderness)
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Old 09-05-05, 11:05 AM   #10
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Interesting theory. But shouldn't you take into account the fact that heavier people also have more "padding" over their sit bones? Assuming sit bone size is a constant, then the rider's weight is distributed over an "effective area" which is more or less proportional to the thickness of the fat layer over the sit bones.
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Old 09-05-05, 12:32 PM   #11
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Quote:
Originally Posted by JavaMan
Interesting theory. But shouldn't you take into account the fact that heavier people also have more "padding" over their sit bones? Assuming sit bone size is a constant, then the rider's weight is distributed over an "effective area" which is more or less proportional to the thickness of the fat layer over the sit bones.
Not to forget the phrase "so thin it hurts to sit down."

I'd imagine one could argue that fat people have more surface area so maybe they have more places to get sore.
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Old 09-05-05, 12:33 PM   #12
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Quote:
Originally Posted by jabike
I think that your presumption that fat people can't get a comfortable saddle is wrong. I have spent many hours in a saddle without a problem. I remember in past days when people would complain about sitting in a wooden pew on Sunday morning. In both cases, you just have to work up to it.
You could also let the preacher know that a shorter sermon might get a bigger offering.
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Old 09-05-05, 02:19 PM   #13
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Originally Posted by Wind 'N Snow
FarHorizon, your logic seems a little off to me...
My wife agrees completely!
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Old 09-05-05, 02:21 PM   #14
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Quote:
Originally Posted by JavaMan
Interesting theory. But shouldn't you take into account the fact that heavier people also have more "padding" over their sit bones?
Perhaps, but the stress isn't necessarily absorbed by the fat. The sit bones are still the sole support.
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Old 09-05-05, 02:27 PM   #15
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Quote:
Originally Posted by jabike
I think that your presumption that fat people can't get a comfortable saddle is wrong...
Since you claim to be both heavy and comfortable, jabike, I must conclude that I **AM** wrong. I've been trying since January to find a comfortable saddle. Some are better than others, but ALL become profoundly uncomfortable after 1.5 hours whether I wear cycling shorts (with padding) or not. Would fellow forum-dwellers be so kind as to recommend saddles that you have found comfortable for y'all's (overweight-only, please) physiques?

Please note that I've already tried the Brooks line and others purported to be comfortable. I'm also aware that individual physiological variation may make a saddle supremely comfortable for you but not for me. I'm further aware that all of us have varying pain thresholds.

Sooner or later, I'm confident that I'll find a saddle that provides the booty-bliss that y'all talk about here. I just haven't found that particular saddle yet...

Thanks!
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Old 09-05-05, 02:36 PM   #16
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I feel your pain! Take a look at this. www.spongywonder.com
Its different and might work.
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Old 09-05-05, 06:07 PM   #17
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Agree with FarHorizon......."comfortable saddle" is an oxymoron. Some saddles, after "x" amount of time in the saddle, are less irritating than others, but I've
never found one that was "aaahhhhh, comfy". There can be quite a range, however, from sitting-naked-on-a-pinecone discomfort to my Regal which only starts to make itself known after 40-50 miles. Even my Rans recumbent used to get me in the tail bone on a long ride.
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Old 09-05-05, 07:20 PM   #18
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Originally Posted by FarHorizon
My wife agrees completely!
At least she agrees that there is some logic going on! One can't ask for more!
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Old 09-05-05, 08:05 PM   #19
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Hello Far-I assume you have tried all sorts of tilt angles with all the saddles you have used so far, I have found out by changing the angle just a little that it can have a profound effect on how the seat feels.
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Old 09-05-05, 08:20 PM   #20
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Why did you get a recumbent?
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Old 09-05-05, 08:49 PM   #21
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Quote:
Originally Posted by oldspark
...I assume you have tried all sorts of tilt angles with all the saddles you have used so far...
You're entirely correctt, oldspark - tilt makes LOTS of difference in how a saddle sits. With my Brooks saddles (and, curiously, ONLY with the Brooks) a very slight "nose-up" position seems most comfortable. Every other saddle I've tried was best completely level. Also, the mounting point - front to rear - even though only an inch or two, seems to make a difference. Would that someone made a "power saddle," much like the "power seat" in an auto, that could be easily modified "on-the-fly" for tilt, fore-aft placement, and height. Such a seat could be programmed to continuously modify its position on the bike for an ever-changing seating position! Of course, the thing with its motors, etc. would weigh more than the bike itself! Ah well...
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Old 09-05-05, 08:51 PM   #22
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Quote:
Originally Posted by Dchiefransom
Thanks, Dchiefransom - I suspect I'll eventually try a recumbent, but for now I'm trying to build a fixed-gear a**-hauler for pure exercise. My following project will be my first bent.

Thanks again for reminding me of what is supposed to be the penultimate in both function and comfort.
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Old 09-07-05, 04:52 PM   #23
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Far-have you measured your sit bones to see how far apart they are, I believe a heavier person would need more padding but it needs to be firm so you don't smash it down and put pressure on your fun parts. The San Marco Arami has firm padding and is listed at 140 mm wide which is a little wider than some of the other saddles.
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Old 09-07-05, 06:04 PM   #24
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How does one measure sit bone distance? Is this to be a "private and personal" type of experience?
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Old 09-07-05, 06:34 PM   #25
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Get a piece of that "memory" foam that doesn't spring right back out after you sit on it. About 1/4" thick. Sit on it on a hard surface, like a bench or wooden chair/stool. Get up quickly, and measure the distance between each of the round depressions you left, center to center. You could always go to a Specialized dealer and have them do it with the "Ass-O-Meter". Convert your mearuement to millimetres.
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