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Technical performance conundrum!

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Technical performance conundrum!

Old 10-07-15, 05:03 AM
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Adam Ross
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Technical performance conundrum!

Hi, I'm new here, but have a baffling situation I am wondering if anyone can shed some light on:

I have two bikes - my special good weather bike, and my every day commuter - both steel with modern gear, although of very different age, quality and stiffness.

I maintain & clean both about equally (a little less than I should probably) and both get roughly the same mileage, although the commuter usually in short stints as I make the same short flat commute to work every day. The commuter is a slightly larger frame too, which means I am more stretched out, but have tried to keep the pedal stroke/saddle position feeling the same on both.

My question concerns a performance drop on my commuter. Let's focus on specifically my top speed on this commute. As it is so flat it is usually comparable on both the out and return journeys, and I generally ride all out on the same section, so effort is also comparable aside from a few off days where I am aware I am fatigued etc...
When I first got the commuter I was achieving 27/28 mph top speed quite regularly, and now has steadily started dropping day by day to 25 or even 24. I know this is a small difference, and would just put it down to a loss of strength, except that the top speeds on my good bike have not changed at all! In fact I put some performance tyres on recently and can reliably hit 30, even 31/32 on a good day on the flat compared to around 28/29 previously. It seems like I can rule out any phyical or fitness changes in myself, and everything still seems to spin as freely as it did originally, so am pretty lost as to a reason.
My only thought is something to do with tyre wear, or possibly a hardening of the rubber compound resulting in higher rolling resistance, but the effect seems too pronounced for this to be the only reason.

Any thoughts welcome, I am truly baffled!
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Old 10-07-15, 06:11 AM
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You'll need a power meter to determine whether or not it's you. Take a few days off and see if things change.
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Old 10-07-15, 07:19 AM
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Does it get you to work on time? If "yes," no worries.
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Old 10-07-15, 07:23 AM
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Could your warm ups be different between the two bikes? I find that the stronger I get (as the season progresses from winter to summer) it takes me longer to feel fully at easy/comfy/warmed up on a bike. My commute is about 20 minutes (give or take). In spring I feel pretty well warmed up by work. In late summer not so. On my weekend bikes and in mid summer it can take an hour or more before I feel fully "there". Andy.
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Old 10-07-15, 07:27 AM
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Brakes rubbing? Hubs need to be rebuilt?
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Old 10-07-15, 07:31 AM
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You didn't mention how long a period of time is involved. The bikes have different frame geometry and possibly other differences. You mention tire condition, but there could also be saddle comfort, handlebar position, etc.

You may find one bike more comfortable under certain weather conditions and, therefore, more conducive to faster riding. This relationship could change when the weather changes. The important thing to remember is that a few days do not a scientific study make. If you continue tracking these differences over an entire year, you may find some interesting variations related to temperature, humidity, wet vs. dry roads, etc. So take note of dates and weather as well.

Incidentally, the traditional wisdom is that stretched-out frames are more cushy (thus, more suitable for long distance) while stiffer frames let you put more power to the wheel (thus, preferred for racing).

Last edited by habilis; 10-07-15 at 07:45 AM.
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Old 10-07-15, 07:43 AM
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Yeah a power meter would be fantastic to diagnose this (and generally) but a bit out of my price range atm. Will see if I can borrow one for a while!
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Old 10-07-15, 07:45 AM
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Haha I rarely get to work on time, but that's never the fault of the bike ; )
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Old 10-07-15, 07:48 AM
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The seasons thing is very interesting - my warm ups are non existent for my commute, whereas I generally have at least 15 mins before going all out on my longer rides. Maybe I am starting off less warm as the weather changes. I will watch this carefully!
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Old 10-07-15, 07:59 AM
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The note about bike fit and comfort is something I had thought about, but not connected to the weather - I plan to measure up and copy my set up precisely from my no. 1 bike, by but suspect this will need a new seat post and stem to compensate for the difference in size and geometry. I am slightly thrown by this though as it has still only been noticed on the commuter bike, through the changing weather etc, and is over a period of just over 3 months.
I am very tempted now to put all my data into a spreadsheet with incidental info like climate, degree of fatigue, warm up etc, and look for some correlation over a longer period.
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Old 10-07-15, 08:12 AM
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Also apologies to everyone for the format of my replies - phone is a bit clunky for my fat thumbs!
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Old 10-07-15, 08:35 AM
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Originally Posted by Adam Ross View Post
The note about bike fit and comfort is something I had thought about, but not connected to the weather - I plan to measure up and copy my set up precisely from my no. 1 bike, by but suspect this will need a new seat post and stem to compensate for the difference in size and geometry. I am slightly thrown by this though as it has still only been noticed on the commuter bike, through the changing weather etc, and is over a period of just over 3 months.
I am very tempted now to put all my data into a spreadsheet with incidental info like climate, degree of fatigue, warm up etc, and look for some correlation over a longer period.
+1 on the spreadsheet, if you really want an answer to the puzzle. Also, make notes as to changes in things like saddle comfort. I find that warm weather and high humidity increase chafing, and it varies according to the saddle. (I used to do data gathering and analysis for a living, and it's more fun than most people would imagine.)
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Old 10-07-15, 08:50 AM
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Rolling resistance is far, far too small a factor to produce the difference you are reporting. If your bearings aren't near lockup it's something about your body or warmup that is causing the difference. Fit, temp, wind are all irrelevant, as you presumably have not changed that, and you report that your speed is reducing consistently on the commuter.
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Old 10-07-15, 08:57 AM
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Originally Posted by cny-bikeman View Post
Rolling resistance is far, far too small a factor to produce the difference you are reporting. If your bearings aren't near lockup it's something about your body or warmup that is causing the difference. Fit, temp, wind are all irrelevant, as you presumably have not changed that, and you report that your speed is reducing consistently on the commuter.
How about this: plastic-covered saddle vs. leather Brooks with perforations in hot weather. No difference? Best to take notes and rule nothing out yet.
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Old 10-07-15, 09:20 AM
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Here's another weird weather-related performance mystery: There are race horses called "mudders," who lead the pack on a wet day. They are unspectacular in dry weather. Why? Who knows. One bike could be having such a climate-related effect on the OP.
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Old 10-07-15, 09:55 AM
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Originally Posted by habilis View Post
Here's another weird weather-related performance mystery: There are race horses called "mudders," who lead the pack on a wet day. They are unspectacular in dry weather. Why? Who knows. One bike could be having such a climate-related effect on the OP.
I know riders who slow down in bad conditions and others who try harder in the same conditions. I tend to push more when it rains. Whether (bad pun, I know) I am actually going faster is impossible to ever know as to do so would require going back in time and changing the weather. Andy.
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Old 10-07-15, 09:56 AM
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Since you are seeing a difference on your commuter but not your nice bike, something has changed. And it's not the hardness or wear of your tires...

Tire pressure? Brake rubbing? Bearings got bunged up somehow? Inspect the bike carefully to see if anything's gone wrong.

Is it starting to get colder where you live? Colder air is thicker and takes more effort therefore takes more effort to cut through. Are you wearing different clothes? Possibly, your body is not performing the same at a lower temperature.
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Old 10-07-15, 10:01 AM
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An interesting story about the value of data-gathering:

Before there was indoor plumbing in London, people drew water from public pumps. There were periodic outbreaks of cholera and nobody knew why. Someone took a city map and marked where the reported deaths occurred (the first known use of a scatter-diagram). He saw that the deaths were concentrated around a particular pump that was near the Thames River, which at the time was full of raw sewage. He informed the authorities, who removed the pump handle. The deaths immediately tapered off, and the epidemic ended. This all took place before the germ-theory of disease even existed.
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Old 10-07-15, 10:12 AM
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If you're like me, you take the nicer bike out on nicer days, and the other one when there is some weather condition. I am always faster on glorious days than miserable ones.

Try switching your bike preferences, and see if the slower speeds follows the bike or the weather.
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Old 10-07-15, 10:44 AM
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Originally Posted by wphamilton View Post
If you're like me, you take the nicer bike out on nicer days, and the other one when there is some weather condition. I am always faster on glorious days than miserable ones.

Try switching your bike preferences, and see if the slower speeds follows the bike or the weather.
Good point. That's the kind of thing people do unconsciously. Keeping track which bike was used on what kind of day could reveal this.
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Old 10-07-15, 10:57 AM
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get started earlier in the morning then it will matter less..
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