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Old 06-20-10, 06:22 PM   #1
cyclinfool
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Friction

Ever since Hermes posted several times on the effective cost of weight when climbing in terms of watts needed to maintain an equivalent speed, it has put things in a different perspective.
How can we make this whole machine more efficient. I have been cycling with some regularity since I was a little one. Some times I'd take a year of two off but I would always come back. I never cared about racing, my thing was always solo distance. When I became an adult I used cycling as a fitness tool so I never cared about efficiency, if the bike was heavy just meant I had to work harder. It was not until I started riding in a group in the mid 90's when I started to change. The real switch for me was when I sprung for my Tarmac 3 years ago. Now I am looking for ways not only to improve me but also the machine I ride.

I posted a tire thread, relating rolling resistance to watts. On my race experience this weekend while I was climbing to think about friction. What came to mind was that there are probably two big sources of friction on a major hill climb, the chain and the bottom bracket. I have not seen any major improvements in the chain, but with ceramic bearings - the BB has improved. With 4% of your output being lost to friction in the BB according to this article http://autobus.cyclingnews.com/tech/...ws/FSA_MegaExo one cna make a simple albeit expensive upgrade fairly easily.

When I was climbing the bike was creaking and I heard a noise with each pedal stroke, I was wondering if my BB was about to go, turns out on further after race inspection that my seat had loosened a little - not the BB going, but it got me thinking.

A 4% power gain form a new BB - worth considering.
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Old 06-20-10, 06:31 PM   #2
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Anything you can do to reduce friction would seem to me to be worth doing. My derailluer pulleys weren't running very smoothly on my SRAM Force rear derailluer so I put aside my Scots dna (don't spend money!) and bought ceramic bearing rear derailuer pulleys (also SRAM), and wow . . . huge difference.

That's just by feel and spinning them as I have no way to measure the difference accurately. Still, 4% seems like a lot for changing bottom bracket bearings but hey, even if it's only 2% it would be worth doing.

All that said, of course, wind (air) movement (a different kind of friction) is still your biggest enemy. Not that I would ever spend the money for wind-tunnel testing, just saying that is where the huge improvements can be made.

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Old 06-20-10, 07:07 PM   #3
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\ wind (air) movement (a different kind of friction) is still your biggest enemy. Not that I would ever spend the money for wind-tunnel testing, just saying that is where the huge improvements can be made.

Rick / OCRR
Agreed - but during a hill climb tire rolling resistance & wind resistance are not big factors, friction where power is being transferred under load is. Derailluer pulleys are another place to look, rear wheel bearings would be another. But since the BB is at the power source, any loss there will be felt first. I may but a new FSA mega-expo ceramic BB on my xmas list.
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Old 06-20-10, 07:14 PM   #4
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I thought this was going to be a thread about shifters.
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Old 06-20-10, 07:57 PM   #5
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FYI: Here's a fairly affordable ceramic BB alternative for Shimano users:

http://www.competitivecyclist.com/ro...5981.19.1.html

Subjectively, this has been effective and trouble free on one of my bikes.
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Old 06-20-10, 08:52 PM   #6
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I thought 4% was the total drive train loss for a bike (under ideal conditions, but probably worse in real life).

You can spin the crank with your pinky when the chain is off. See this unit conversion pdf. One watt is 8.8 inch-lbs/sec. That's a 1 pound weight at about the length of the crank arm, applied every second. For just one watt. You aren't going to save 10-20 watts by changing to a ceramic bottom bracket, since your current old, worn, dirty bottom bracket isn't using anything near that much.

In a race, saving even 1-2 seconds over the whole race would be worth it. But I don't think a rider could tell the difference between bottom brackets while riding.

And, there was the group ride a couple years ago, where the rider with a new ceramic bottom bracket locked up his cranks with a crunchy sound coming from the bottom bracket. The cranks were jammed in place. Maybe the ceramics are stronger now.

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Old 06-20-10, 08:57 PM   #7
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On climbs, I see and hear riders grinding their tires from the side-to-side motions, and the out of saddle force driving the rear tire. That's got to use energy, too. A smoother pedal stroke and a straighter line up the hill would help.

Some tires have less rolling resistance. They lose less power to flexing at the bottom where it contacts the road. Of course, most of the testing is done by rolling the wheel on a fairly small metal cylinder, and measuring the power needed. This isn't very close to the real world of a flat road with varying roughness.

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Old 06-20-10, 09:06 PM   #8
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I think if one is racing at the highest levels of the sport then swapping bearings and pulleys might make sense to capture that last minute edge. But for guys at our level, I really think it is more placebo effect than anything else. Of course if your equipment is worn or broken, any change can be a big improvement.
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Old 06-20-10, 09:43 PM   #9
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Seems like you'd be better off springing for a frame w/ the BB90 or BB30 (fat, in other words) bottom brackets that would effectively stiffen up the power transmission area?
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Old 06-20-10, 10:22 PM   #10
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I have been converting my BB to ceramic as well as wheel bearings. I think it is a lot of bang for the buck compared to other ways to spend money to improve performance.
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Old 06-20-10, 11:36 PM   #11
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too much thinking. TOO MUCH THINKING!
For me, anyway...
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Old 06-20-10, 11:54 PM   #12
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When climbing wonder how much riding position has to do with delivered power, of which friction is a component? It seems to me if a person has a postion where the tires hop, or at least don't provide maximum traction and power transfer that will have a far greater impact than friction. Go for the big things first before worrying about the nitnoy.
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Old 06-21-10, 05:44 AM   #13
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So I guess I am blowing it by carrying a 15 pound trunk bag with a lock and chain, tools, tubes, inflator, towels, money, plus my wife's stuff?
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Old 06-21-10, 08:15 AM   #14
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So I guess I am blowing it by carrying a 15 pound trunk bag with a lock and chain, tools, tubes, inflator, towels, money, plus my wife's stuff?
Depends on your goals - if your carrying your wife's stuff it sounds to me like your in the correct place.

The reality of the situation is - during a race this weekend I had time to spend over an hour thinking about how slow I was moving up that 3500' elevation climb at a measly 5mph. For approximately 90 minutes the increase in potential energy required to raise myself, my cloths and the bike meant I had to put out an average of 176W and given I was fighting a head wind and other losses in the system I probably averaged about 200W. Now considering the fastest climber in that race I heard got across in like 50 min - assuming rider + bike weighed 50lbs less than me + bike, he was putting out close to 280W - WOW! - about the max a person should be able to sustain over a long duration is about 300W.

Now if I loose 20 lbs of ugly fat and keep my same strength level I shave 10 minutes off that climb (maybe a little less because wind, tire and other resistances goes up a bit) - I would be traveling 5.5MPH rather than 5MPH. If I reduce friction by 4% of the 200W (est) I am putting out that gets me 5% reduction of the 176W it took to raise my fat a$$ up the hill or about a 5min reduction in time. If I do both than that saves me close to 13min of time. When the results come out I can see just what all that would mean, maybe from DFL to middle of the pack of the over 50 age group.

Now if you are not racing, not worried about getting dropped on a club ride (when climbing a hill) or not a gear head in general all this means squat. But if your spending your Sat evening climbing up a 3500' mountain being timed and watching every Tom, Dick and Mary as well as a few stray torteses pass by like your standing still you have time to think about these things.

I may come to my senses and just be happy with where I am at - reasonably healthy, a good recreational cyclist and let it go at that.
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Old 06-21-10, 08:30 AM   #15
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^^^ I think you are underestimating your power output. Knowing your weight and speed I think your power is higher because we are (or were similar). I ride with a PT so I'm going on my observations.
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Old 06-21-10, 08:54 AM   #16
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^^^ I think you are underestimating your power output. Knowing your weight and speed I think your power is higher because we are (or were similar). I ride with a PT so I'm going on my observations.
It is indeed possible. I have read that the best human output on a bike for an hour is 300W. I certainly am not "the best" so 200W would pass the sniff test.
I calculated the 176W from mgh/t = (91Kg * 9.81m/s^2 * 1067m)/(90*60) = 176.4W and just guesstimated the system losses. At 5MPH there is not a lot of wind resistance, but with the head wind there might have been more. Then there are all the friction looses in the bike. this was a constant climb of 8.5% with no down hill or flat so I think the 90 minute average should be close. I can probably charge a short hill at much more power - but for 1.5hrs you sort of peter out after awhile. If you think I can put out more that's great - I like the way you think...
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Old 06-21-10, 09:15 AM   #17
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FYI: Here's a fairly affordable ceramic BB alternative for Shimano users:

http://www.competitivecyclist.com/ro...5981.19.1.html

Subjectively, this has been effective and trouble free on one of my bikes.
Thanks - they CC was the first place I looked.
Biketiresdirect has the Mega-expo which is specifically made for my crankset: http://www.biketiresdirect.com/pfscb...bracket/pp.htm
$30 more but it's made for the FSA-mega expo crank which is what I have.
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Old 06-21-10, 09:16 AM   #18
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Four percent?? From just the BB?? That strikes me as more than a little improbable. I seriously doubt that hubs, bb, pulleys and chain together account for that much energy loss. Sounds to me like somebody's trying to sell you something.

SP
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Old 06-21-10, 09:42 AM   #19
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Four percent?? From just the BB?? That strikes me as more than a little improbable. I seriously doubt that hubs, bb, pulleys and chain together account for that much energy loss. Sounds to me like somebody's trying to sell you something.

SP
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Yes - I was a little concerned about that too but the data for the article cam from Bike testing inc. Although they get a lot of industry support they claim to be independent. I alos know there is an article out there that was published in 2006 by Velonews that has some test results but I have not been able to find it. If anyone has it please post it. It may show some conflicting information. Like with all things - it really depends on how the testing was done. In a BB test I would insist on a fully loaded test that has been run for at least on hour so that all the components are at operating temperature and the balls are undergoing full deformation.
So in any event, 4% is the only data I have and until someone posts some other data - I/m sticking with that number. BTW - the Mega expo is only supposed to loose 0.5%.
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Old 06-21-10, 10:00 AM   #20
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Top professionals: Magic number to win the TdF is 6.7 watts/kg of sustained one hour power or functional threshold power or FTP. Lance = 487 watts. We had a guy who competed in professional Ironman competitions give a talk at our club. He could sustain 315 watts for the 112 mile bike section at 26 XX miles per hour average speed.

Not so top professionals: One of our elite (under 30) cat 1 guys averaged 315 watts in a road race and our guys average 285 watts for 70 miles on our group A ride. I do not go on those.

In our Low Key Hill Climb Series, the climb up Diablo, which is similar in elevation to White face but less steep, the winning time was 51:12 last year with an estimated average power of 335 Watts, 12.66 mph and 4192 fph.

On the Mount Hamilton climb, one of our cat 3 guys was with the lead pack for the first climb but got dropped when he could not maintain 400 watts.

We (me) are pathetically weak compared to the top pros and the local strong guys kick my ass all over the road.

With 200 watts of average power, you would climb Mount Diablo in 1:28 @2183 fph and finish near the bottom of the field which is not horrible. There are just a lot of very strong hill climbers. However, 200 watts for 1 1/2 hours is not FTP. It is z3!

If I were to race White Face and I would probably not do it (too hard, steep and long), I would target high z3 power. And I would start out easy z3 and save some for the top. I would use z4/z5 on shorter steeper sections. Pacing in long hill climbs and TTs is critical to achieving a good time.

I have a bad feeling you used your Gatorskin tires to race White Face. Tell me it ain't so.

Last edited by Hermes; 06-21-10 at 11:05 AM.
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Old 06-21-10, 10:05 AM   #21
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When climbing, I hear creaking and grinding sounds coming from my knees that drown out all other bike noises. Will ceramic bearing help me?
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Old 06-21-10, 10:19 AM   #22
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When climbing, I hear creaking and grinding sounds coming from my knees that drown out all other bike noises. Will ceramic bearing help me?
Maybe in a knee replacement
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Old 06-21-10, 10:48 AM   #23
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Well, I thought this was all about posting demeanour on the forum

But, it's not

So, ride with your brakes on. What doesn't kill you makes you stronger, and his Merckxness didn't think that bike parts should be made of pottery
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Old 06-21-10, 11:06 AM   #24
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Hermes,
Yes, sorry (tail between legs) - I used the Gatorskins, it was all I had. But I figured rolling resistance was not an issue at 5mph. They were pumped up to 125 though.

as far as where my heart rate was - if I went down to Z3 I would have fallen over. At Z4 on my practice run in May I felt OK - it was the right effort and I was able to maintain it. This time - starting out at Z5 was way too much too soon. Now my estimate for max heart rate could be off - 195 is the highest I have been able to push myself but that's not to say if I were hooked up to a machine I may not even be at VO2max there. Another factor was I downed a 20oz diet mountain dew about 2 hours before the race to get caffinated (PED) and kept myself well lubricated with hammer gel - that may have elevated my HR. Now even at that point I was breathing hard and deep but not panting like a dog and had the occasional reflux burp, but still not tossing cookies. After mile 4 I was able to get the HR back to Z4 (174). According to this calculator http://www.heartmonitors.com/zone_calc.htm anyway - the zones are correctly calculated. The data I used:
age 54
resting HR 60
max 195

Your point about Functional Threshold Power (FTP) is correct and I had not considered that, I should not be able to keep up a HR of 184 for 45 minutes (about 1/2 way through the effort) if it was indeed VO2max - so obviously it wasn' t- which means my max heart rate may be more than 195. Now is it Z3, according to this article maybe it was Z4 http://www.flammerouge.je/content/3_...functhresh.htm.

In any event - it was pretty damn painful! Now I know I am a weakling but I set a low threshold for next year

Oh - and to your strategy " I would use z4/z5 on shorter steeper sections." If you could lay out a road with a constant grade - this is it, 8.5% +/- 0.5% - 8 miles. It's 8 miles of steep section - have at it!

And to your point"With 200 watts of average power, you would climb Mount Diablo in 1:28 @2183 fph and finish near the bottom of the field which is not horrible. "
On this race as I stated in my report - pretty close if not DFL - so what's you point again Bud

At least I was able to stay ahead of the black flys and didn't need the deep woods off.
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Old 06-21-10, 11:17 AM   #25
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I did a fast google. Most articles I found on "friction" and cycling worried most about air resistance. I found an article that talked about loss in the bicycle's transmission and they actually did measurements. They thought that friction losses in the drive train were 2%-4% and that was with a dirty transmission. They found that a clean transmission was about 1% more efficient. I even found a reference in another place which talked about friction losses in the knee joints! I wonder how the thought they were going to mearsure that one.

Now as I recall, years ago there was an article in Scientific American and they said that the total friction losses were modest like 1%-2% but I don't recall them measuring anything.

There were even some articles talking about friction losses from the tires from rolling resistance. I did not see anything on bottom brackets.

I think that friction losses in bicycles are probably pretty dern small. They can almost be ignored because other things have greater effects. At any kind of speed (over 12 mph), reducing wind resistance will have a greater effect.

Even on hill climbs, I think other things would have a greater effect. On hill climbing, the biggest effect on speed is power to weight ratio. So the lighter you can get the bike and you without losing power the faster you will go. If I assume that I weight 180 lbs and my bike weighs 20 lbs (not true but close enough because the figures are round), that means I am dealing with a 200 lb object. Well, how light can a road bike go? I think 14 lbs is the limit for extreme weight weenies. So that gives me a 3.5% improvement just by reducing weight. That improvement alone is just about as great as the total friction losses. Now, the big place to remove weight is the engine. I am reasonably fit and not over weight, but I bet I could lose 20 lbs if I wanted to get really light. So that is another 10% improvement. So by weight loss I can improve my performance by about 14%. Now the other thing I could do is get stronger and add more power to the power to weight ratio. I would think that I could increase power by 20% and possibly more but I do ride a fair bit so this is not really that feasible. So with everything at max, I could probably increase by 34% and maybe even more.

But total friction is probably something like 2%-5%. How much CAN we decrease friction by? Wouldn't drastically decreasing friction require a substantial redesign of the drive train and bearings? That really is not something that I can undertake. It isn't something that even professional cycling teams can do. I would think that if such a thing were possible that Shimano and Campy would have done it years ago. Bikes have been around for some time now and they have not changed much except for the materials used. I would think given the existing equipment, we can control friction only marginally by keeping our bikes well maintained and by riding on well inflated tires. That is about it. Doing that might decrease total power losses by a percent or two. But a 1 or 2 percent reduction pales with the much larger improvements we can see by weight loss or getting fitter.
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