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 Post subject: Re: Kai-ming's seatpost
PostPosted: Thu Aug 30, 2012 11:49 am 
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Joined: Sat Mar 17, 2007 10:49 am
Posts: 787
Location: Mallorca, Spain
best way to control the flex may be with different elastomers a la look seatpost.


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 Post subject: Re: Kai-ming's seatpost
PostPosted: Thu Aug 30, 2012 8:26 pm 
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Joined: Mon Dec 03, 2007 12:53 pm
Posts: 94
You probably don't need that much of movement from the seatpost, especially heavy weight rider.

thisisatest - I think you guys arent realising how much movement a seatpost gets in a frame. If one were to imagine the seat tube having a much larger bore than the post's shims, and the post clamp pinching down on the upper shim, it's easier to see that the seat tube in fact "gives" more locally and less uniformly. Reality is similar to this, but on a smaller scale.
Many, many frames get "creaking" from excess seatpost hanging out inside the frame moving around slightly, even frames with a constistent interior shape all the way down.

cervelo - http://www.youtube.com/watch?v=ipjuWSTM ... ure=relmfu 4:08 - 4:14


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 Post subject: Re: Kai-ming's seatpost
Posted: Thu Aug 30, 2012 8:26 pm 


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PostPosted: Sun Sep 02, 2012 11:17 pm 
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Joined: Mon Dec 03, 2007 12:53 pm
Posts: 94
Has anybody experienced this? The Colnago seatpost/saddle bottomed on me, a 130lbs rider. :oops:
Below are pictures before saw/Dremel, the bolt at the rear had been removed for cutting in the second picture.
ImageImage

Below are pictures after saw/Dremel.
ImageImageImageImage


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PostPosted: Mon Sep 03, 2012 12:55 am 
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Joined: Mon Jun 14, 2010 2:32 am
Posts: 91
It doesn't surprise me being the aspide saddle was one of the most flexible saddles I've ever ridden (then again I'm 180lbs).
'


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PostPosted: Tue Sep 04, 2012 10:49 am 
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Joined: Mon Dec 03, 2007 12:53 pm
Posts: 94
Yes, it is Aspide FX made for Colnago.Image

No, no body experienced that? I am surprised.


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PostPosted: Tue Sep 04, 2012 11:14 am 
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Joined: Sun Oct 26, 2008 3:12 pm
Posts: 164
I use SSM Aspide Arrowhead and when using the type of seatpost clamp as the OP, I have to cut the bolts to size, so they don't stick out the top. This way, the base of the saddle never touches the clamp. I weight 135 lbs (69 kg).

If you cut the saddle base, you'll have even more flex, so I think sooner or later the bolts will start to "eat" the leather cover.


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PostPosted: Tue Sep 04, 2012 11:39 am 
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Joined: Mon Dec 03, 2007 12:53 pm
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69kg = 69x2.2lb = 151.8lb :mrgreen:
You are right, cutting the saddle base would make it more flexible. When I ride on the saddle I always feel that the saddle is a little too stiff compare to my other saddles, I was willing to give it a try anyway. If it bottom because of the cutting, I can always swap the saddle of my other bikes with a different seatpost. :beerchug:


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PostPosted: Tue Sep 04, 2012 7:36 pm 
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Joined: Sun May 16, 2010 7:28 pm
Posts: 605
Use shorter bolts? :noidea:


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PostPosted: Wed Sep 05, 2012 9:40 am 
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Joined: Sat Nov 29, 2008 8:00 pm
Posts: 1735
Location: Sydney, 'straylia
That's an old saddle - I wouldn't be surprised if it's just knackered.


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PostPosted: Wed Sep 05, 2012 10:40 am 
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Joined: Wed Mar 28, 2007 12:49 pm
Posts: 1576
Location: Near Horgen, Switzerland
+1 on all points above. The problem is not unusual.

- Cut the bolts not the saddle - you don't want a bold embedding itself in your lower regions
- Try a new non bananaed saddle
- Switch to a saddle with more clearance
- Switch to a Campag seatpost or one with a with traditional or sideways clamp (and shim if it's a 28mm frame)


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PostPosted: Fri Sep 07, 2012 12:31 pm 
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Joined: Mon Dec 03, 2007 12:53 pm
Posts: 94
kulivontot wrote:
Use shorter bolts? :noidea:

Half correct, the bolt at the front is difficult to replace if not impossible. :mrgreen:


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PostPosted: Fri Sep 07, 2012 12:42 pm 
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Joined: Mon Dec 03, 2007 12:53 pm
Posts: 94
BikeTart wrote:
That's an old saddle - I wouldn't be surprised if it's just knackered.

That sounds like comment from a bike shop. :roll:


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PostPosted: Mon Sep 10, 2012 12:54 am 
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Joined: Mon Dec 03, 2007 12:53 pm
Posts: 94
Image
This is a TranzX 31.6 setback seatpost. The heavy bit is really at the mounting head. I have cut short the post at the head end, removed the head, drilled it including drilling the socket bit that is glued to the post (no photos was taken at the time it was done) and epoxyed it back to the shortened post. I think there is a saving of around 100g as far as I remember.
Image
This is how it look when installed to a bike.


Image
Image
Tuning of a Shimano R600 crank arms.

Image
This is the ugly un-finish bit. The weight of the tuned R600 crank is about the same as a 7800 DuraA.
Image
It is strong enough to be my travel bike.


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 Post subject: Re: Kai-ming's kitchen
PostPosted: Mon Sep 10, 2012 1:44 am 
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Joined: Mon Dec 03, 2007 12:53 pm
Posts: 94
Kai-ming's kitchen! I like the caption. :mrgreen:


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 Post subject: Re: Kai-ming's kitchen
PostPosted: Mon Sep 10, 2012 1:46 am 
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Joined: Wed Oct 31, 2007 10:32 pm
Posts: 7520
Location: Los Angeles / Glendale, California
A true tinker-er!
It's great to have a forum member looking to experiment. Great work!

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 Post subject: Re: Kai-ming's kitchen
Posted: Mon Sep 10, 2012 1:46 am 


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