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Old 12-06-06, 10:23 PM   #1
cooker
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Define relaxed?

Hi all. I don't know about all of you, but I can't get a fix on what "relaxed geometry" actually means.

Is it about body position? Most bikes, of all ilks, seem to have about a 73 degree seat tube angle which means they all put your butt in approximately the same position relative to your feet (subject to you tweaking the seat position on its rails). The only other factor affecting body position is handlebar placement...ie long or short top tube and/or stem, steerer height, stem angle. So if your handlbars are low or far forward you lean more forward and perhaps stretch your arms. If your handlbars are close or high you can sit a bit more upright.

So does relaxed geometry refer to those factors that affect handlebar position?

Or does it refer to things that affect bike handling like steerer angle, trail, rake, wheelbase, chainstay length etc? Anyone understand and can explain the concept? A search was not helpful. Thanks
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Old 12-06-06, 11:26 PM   #2
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Yeah, I don't think seat-tube angle makes that much of a difference as setting the seat for KOPS will give you the same position relative to the crank regardless of seat-tube angle. I think "relaxed" refers more to the front-end. A shorter stem with higher-rise & tall handlebars give a more upright seating position. Lower head-tube angles of 72-73 degrees along with +60mm trail makes for a stable bike. Longer chainstays to accomodate larger touring-type tyres results in longer-wheelbases and more comfortable ride.
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Old 12-07-06, 02:28 AM   #3
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On a touring bike, it's true about the angles relative to the human body. One small exception. Not all seats have much built in rail for adjustment, so that can push the seat tube position around a bit.

Seat stays/rear ends can get real long, an example being bikes like the Sakkit, or the Xtracycle. Front ends can get as low as 68. Standard Motorcycle head tube angles at the normal end of things are 60 degree, though one never sees that in road bikes. I think it's there in the bikes of my youth and modern low riders, and I sometimes wondered what it would be like on a touring bike. Overall though performance bikes including most touring bikes want steeper front ends. Front paniers quiet the touring bikes down and the handling is a bonus in most cases, anyway.

As you get in to comfort geometry the seat tubes, and all the rest of it can get pretty slack.

At the other end of the spectrum, one might say that the cyclo cross frames that occasionally get used for paris roubaix coblestone races are an example of relaxed geometry being pulled into the racing game.
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Old 12-07-06, 06:55 AM   #4
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Quote:
Originally Posted by Peterpan1

As you get in to comfort geometry the seat tubes, and all the rest of it can get pretty slack.
I looked at a bunch of comfort bikes specs and they still seem to have the 73 degree seat tube, so I'm not sure what mean by "the seat tubes, and all the rest of it can get pretty slack". What is slack?
Thanks
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Old 12-07-06, 08:46 AM   #5
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As you have discovered, "relaxed geometry" is an undefined term. For the most part though it refers to a bike that steers slowly and has a lot of stability.

Old time thinking was a bike with more kicked back seat and head angles - 72 degrees seat and 71-72 degree head angle. Add in some long chain stays – 43 - 45 cm or so, and you have a “relaxed” bike. One interesting thing about these older bikes is that while they often had shallow head angles, they almost always had lots of rake in the forks, 50+ mm, so the trail numbers were fairly conventional by modern standards.
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Old 12-08-06, 01:00 AM   #6
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Slack and relaxed are roughly speaking the same thing.


We may be looking at different comfort bikes. Sadly it seems like a lot of those companies use flash sites that screw up my computer, but meauring by hand out of the electra bike company add in last month's Bicycling, I got 67 degrees for the seat tube, and 69.5 degrees for the head tube. I call that slack.

Update, I found a townie image for my cad program, and the seat tube came out at 65.5, and the headtube is 69.2.
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Old 12-08-06, 10:36 AM   #7
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Yeah, the electras have that seat back, flat foot design, but a lot of other "comfort" bikes have the 73 degree seat tube.
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Old 12-10-06, 08:25 PM   #8
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Calling a geometry "relaxed" is almost a big a misnomer as calling geometry "compact". It's pretty meaningless when you consider with the right fork, you can make a bike with a 72 deg HTA steer quicker than one with a 73 degree!
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