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Author Topic: Seatpost set back?  (Read 2464 times)

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scooter

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Seatpost set back?
« on: August 09, 2007, 10:11:46 PM »
After taking some advice about the Thompson line of products, I am looking at thier elite seatpost. My current post, an Easton EA50 on my Giant Anthem 1 has minimal setback, that is the pivot for the saddle mount is slightly behind the center of the post. Thompson offers a setback as well as a zero setback where the pivot is directly above the center of the post. I noticed on the two Anthem models above mine, a zero set back post is used. How will this setback or lack there of affect handleing and power transmission during pedaling?

Offline BeerCan

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Re: Seatpost set back?
« Reply #1 on: August 09, 2007, 11:53:25 PM »
Wow  had a long reply and it disappeared.  Anyway there are a lot of factors that come into play with the seat post.  One of them is your bio mechanical structure, upper vs lower leg length, and leg vs torso length.  Bike geometry comes into play also and seat tube angle will have an affect on your overall position.  For me on my current bike I am aiming for between 2-3 cm behind KOPS (knee over pedal spindle).  That means a seat post with 16 - 20 mm setback.  So what it really comes down to is that there is no simple answer.  You have to use what is comfortable for you.  BTW I am not a huge believer in the KOPS method.  It just works out on this frame that I can use that measurement to get my bike close to where I need to be if I change an item that affects my fit.

Here is a pretty good article blasting KOPS  :D
http://www.sheldonbrown.com/kops.html
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Offline slowfatguy

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Re: Seatpost set back?
« Reply #2 on: August 10, 2007, 07:40:43 AM »
IMO if you are running your seat set way back on the seatpost to get the fit right I'd get the setback post. But if you are running it pretty much in the middle, then the zero setback will work. Basically get the one you will need to help get your bike fit the way you want it.
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Offline Alan

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Re: Seatpost set back?
« Reply #3 on: August 10, 2007, 08:02:59 PM »
Odd thread.  Today I just ordered my 410mm Thompson post for my Anthem 2.  Decided not to go with the setback post.  The bike already had a big stretch for me and I went with a 90mm stem to make it a bit more comfortable for the "all mountain" stuff found at Alafia and Boyette.  Figured the setback post would be too uncomfortable. 

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Re: Seatpost set back?
« Reply #4 on: August 10, 2007, 08:49:13 PM »
IMO the last thing you should do is use seat position to adjust *pit feel.  Adjust your seat first and then change everything else till it is comfortable.  If not knee / leg and/or back pain will surely ensue.
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Offline slowfatguy

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Re: Seatpost set back?
« Reply #5 on: August 10, 2007, 09:51:00 PM »
Let's discuss this then. I move the seat around until I feel real comfortable pedaling, but can also get behind the seat without difficulty. I've never run a setback post, don't need to. But I've seen alot of guys that have the seat jammed all the way back. IMO they would be better off with a setback post as it would allow them to mount the seat in the middle of the rails, which is probably less stressful on the seat. But I also know pretty well how my body likes to be on the bike. I've set up a few bikes and took a quick guess on seat position and nailed it, never had to move it fore/aft or change the height. Maybe for newer riders getting a fit done would be a better idea? But then what principle do you follow for seat position, KOPS or make your own up like I did?
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scooter

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Re: Seatpost set back?
« Reply #6 on: August 10, 2007, 10:37:11 PM »
I have deceided on the set back post for a couple of reasons. After looking at the 2008 Anthem comp I see they are running about a 1/2" set back(Raceface post) as is my stock post on my 2007 anthem 1 (Easton EA50). Secondly I already feel like the front end is a little light so the last thing I want to do is move my CG farther forward. In looking at the Thompson it looks like a lot of setback but according to their site it is only 5/8" about an 1/8" more than what I have now.

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Re: Seatpost set back?
« Reply #7 on: August 14, 2007, 05:18:22 PM »
Apparently I have shorter than average legs for a 5'10" person. That means that I fit a medium frame in regards to stand-over height, but it also means that my torso is longer than average and thus the top-tube length isn't quite long enough for me. I already have my seat back as far as it can go and I'm constantly sitting on the tail end of it. I feel as though I have too much weight on my hands and arms as well, and when cruising down a hill if I get back off the seat and stretch out I have soo much more control.

I'm hoping to get a fitment first, but I'm planning on a set-back Thompson Masterpiece.
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scooter

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Re: Seatpost set back?
« Reply #8 on: August 14, 2007, 06:27:29 PM »
Ditto!

Offline BeerCan

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Re: Seatpost set back?
« Reply #9 on: August 14, 2007, 10:03:14 PM »
Apparently I have shorter than average legs for a 5'10" person. That means that I fit a medium frame in regards to stand-over height, but it also means that my torso is longer than average and thus the top-tube length isn't quite long enough for me. I already have my seat back as far as it can go and I'm constantly sitting on the tail end of it. I feel as though I have too much weight on my hands and arms as well, and when cruising down a hill if I get back off the seat and stretch out I have soo much more control.

I'm hoping to get a fitment first, but I'm planning on a set-back Thompson Masterpiece.

Thats why, in my personal opinion, stand over height should not even be a consideration when fiting a bike.  TT length is probably the most important factor, then geometry then seat tube.  After all you gonna ride your bike or stand around with it?  I know I went through about 4 frames until I finally figured this out.
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