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help with asymmetrical seat post clamp to QR conversion?

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help with asymmetrical seat post clamp to QR conversion?

Old 04-04-21, 07:52 AM
  #1  
el forestero
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help with asymmetrical seat post clamp to QR conversion?

I frequently have to adjust the seat post of a 2019 Giant Escape RX Disc hybrid bike to accommodate the varying heights of visiting riders who've never used the bike before. The seat post clamp has two bolts that have to be loosened and tightened to adjust the seat post, so the process can be time consuming. That isn't convenient when our group of cyclists is waiting for the rider of this bike to be ready. A quick release clamp would work out much better.

The back sides of the seat post and seat tube of this bike are flat, as shown in the photo below. Giant calls this design "D-Fuse". My local Giant store (in Japan) says they don't make a QR clamp for it.

I couldn't find a QR clamp of this shape for sale online, so I tried using a round QR clamp on the seat tube. That didn't work out because there was a lot of play in the seat post even when the clamp was very tight.

Anybody know of a source for a QR clamp designed for this type of seat tube? Or can anybody suggest a way of making a round QR clamp work with this seat tube?

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Old 04-04-21, 08:07 AM
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It says in your OP that there are two bolts. I see only one. You could take it out and replace it with one of these.

https://www.performancebike.com/kall...RoCSQgQAvD_BwE


Dan
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Old 04-04-21, 08:41 AM
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el forestero
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Originally Posted by _ForceD_
It says in your OP that there are two bolts. I see only one. You could take it out and replace it with one of these.

https://www.performancebike.com/kall...RoCSQgQAvD_BwE


Dan
Here's a better angle for seeing the two bolts. They screw in on opposite sides of the clamp.

The QR lever is a good idea, and it's too bad it won't align properly with a two-bolt clamp.


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Old 04-04-21, 09:29 AM
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Oh...so there are two holes going through the clamp...one above the other. Well...I’d still think you could use a QR clamp like the one I posed. You may need to drill out which ever hole you use for it.

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Old 04-04-21, 10:05 AM
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That may be the best bet. I was also thinking it could be possible to use a circular clamp and stuff something solid into the space between the clamp and the back of the seat tube so the clamp can exert force on the seat tube from all sides. May try poking around in a hardware store for a random piece of metal or rubber of about the right shape.
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Old 04-04-21, 10:44 AM
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Yeah...it ‘probably’ wouldn’t make much difference (using a circular clamp). But I think I’d try to stick with the existing clamp since it’s already the correct shape.
Good luck.

Dan
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Old 04-04-21, 02:03 PM
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Before I went and did a modification to the clamp, I'd make sure a replacement was available if things go wrong.
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Old 04-04-21, 04:46 PM
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Originally Posted by _ForceD_
Oh...so there are two holes going through the clamp...one above the other. Well...I’d still think you could use a QR clamp like the one I posed. You may need to drill out which ever hole you use for it.

Dan
Might not have to drill out anything.

If the threaded part of that binder matched the threads in the clamp, then he could lose the nut on the end of the binder and thread it right into the clamp.

Then there is the issue of the cam end not sitting flat against the clamp (look how the clamp is shaped). I would use washers that fit in the hole that is countersunk for the current bolt head, and stack them up so that the cam is pushing on those and cleaing the outside of the clamp.

I hope that makes sense.
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Old 04-04-21, 05:10 PM
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Originally Posted by dedhed
Before I went and did a modification to the clamp, I'd make sure a replacement was available if things go wrong.
THIS!!!
It would seem fairly simple (but not actually easy) to modify the clamp to accept a QR. perhaps filing (don't grind Al please with my bench grinder) a flat for the over center cam's base to seat against.
Interesting is my first thought of two "wing nutted bolt heads". Is there an over the counter one out there? Ypu'd have to do the searching, likely outside of the bike industry and within the general industrial world.

Some understanding of the goal might help one figure out what won't work. Are you hoping to adjust the seat height frequently? Or only a few times a year, as example. Andy
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Old 04-04-21, 07:15 PM
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You could basically mold a wedge for the flat side to use with a round seat clamp. Get some "JB Weld Steel Stik" epoxy putty. Has a fairly high crush resistance when fully cured and would be easy to form a perfect wedge using the seat clamp in place while it cures. You'll have to cut a slot in the wedge where the seat tube slot is while it's still soft or cut it with a file, dremel, etc. after it cures. It's similar to working with clay so easy to work with. From the looks of your original clamp it doesn't look like it's putting much pressure on the flat side to begin with.

Last edited by Crankycrank; 04-12-21 at 08:25 AM.
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Old 04-11-21, 07:14 PM
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el forestero
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Originally Posted by Andrew R Stewart
THIS!!!
...
Some understanding of the goal might help one figure out what won't work. Are you hoping to adjust the seat height frequently? Or only a few times a year, as example. Andy
Frequently. Every day on busy weeks.
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Old 04-11-21, 09:14 PM
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And now I see that you started this thread with that data, as in first sentence. I should have picked up on that. My concerns that the OEM clamp really wasn't designed/made with such frequent tightening and loosening in mind, generally road bikes don't see anywhere near the same number of cycles of use that MtBs do. And enough MtB clamps become problematic so they're available in the aftermarket and often stocked at your LBS (we have maybe a dozen on our shelves right now). But as mentioned that non round post isn't any help with all this. I hope that the OEM post is a tight fit with no slop. I guess i would try building up a round clamp and findout if it holds up. Both the post better and the filler material you use to fit the clamp to the non round seat tube. Andy
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Old 07-19-21, 03:37 AM
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Hi there, just wondering if you had any luck with any of the options?
Having the same issue with my wife's bike - it's annoying having to take out an allen key all of the time!
Thanks in advance
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Old 07-25-21, 07:27 PM
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Unfortunately my bike tour biz has been dead in the water during the pandemic, so this has been a back-burner project. Haven't worked on it since spring. Will post here if/when I get back to it. Good luck!
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Old 10-04-21, 07:58 AM
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Found a solution!

Originally Posted by el forestero
Unfortunately my bike tour biz has been dead in the water during the pandemic, so this has been a back-burner project. Haven't worked on it since spring. Will post here if/when I get back to it. Good luck!
Finally got round to fixing my wife’s seat!
I replaced it with a generic round 31.8mm one. It was a bit stiff getting it on at the start, but it fits snugly around the top - the gap at the back doesn’t seem to be a big issue at the moment (I tried a bigger size and it just rotated round - I was getting ready to buy some of the metal putty mentioned above, but seems to be ok with this smaller size).
Overall a cheap and simple solution that is working well so far..
Sorry don’t seem to be able to post pictures as a newbie, but happy to share details
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Old 10-04-21, 08:00 AM
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Found a solution

Originally Posted by el forestero
I frequently have to adjust the seat post of a 2019 Giant Escape RX Disc hybrid bike to accommodate the varying heights of visiting riders who've never used the bike before. The seat post clamp has two bolts that have to be loosened and tightened to adjust the seat post, so the process can be time consuming. That isn't convenient when our group of cyclists is waiting for the rider of this bike to be ready. A quick release clamp would work out much better.

The back sides of the seat post and seat tube of this bike are flat, as shown in the photo below. Giant calls this design "D-Fuse". My local Giant store (in Japan) says they don't make a QR clamp for it.

I couldn't find a QR clamp of this shape for sale online, so I tried using a round QR clamp on the seat tube. That didn't work out because there was a lot of play in the seat post even when the clamp was very tight.

Anybody know of a source for a QR clamp designed for this type of seat tube? Or can anybody suggest a way of making a round QR clamp work with this seat tube?
see below for my work around
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Old 10-10-21, 07:20 PM
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Originally Posted by TomKing
Finally got round to fixing my wife’s seat!
I replaced it with a generic round 31.8mm one. It was a bit stiff getting it on at the start, but it fits snugly around the top - the gap at the back doesn’t seem to be a big issue at the moment (I tried a bigger size and it just rotated round - I was getting ready to buy some of the metal putty mentioned above, but seems to be ok with this smaller size).
Overall a cheap and simple solution that is working well so far..
Sorry don’t seem to be able to post pictures as a newbie, but happy to share details
Good to hear that worked for you. Thanks for sharing the info!
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Old 10-12-21, 09:30 AM
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The stock nuts/bolts must have flat, parallel faces recessed in the clamp that they seat against. But a quick-release skewer won't be narrow enough to sit against those faces, so you need spacers that will slide over the skewer and sit against the flats to essentially translate the flats outward. McMaster Carr is a good place to find this kind of thing, although shipping to Japan might make it uneconomical.
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Old 10-17-21, 06:37 PM
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el forestero
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Originally Posted by adamrice
The stock nuts/bolts must have flat, parallel faces recessed in the clamp that they seat against. But a quick-release skewer won't be narrow enough to sit against those faces, so you need spacers that will slide over the skewer and sit against the flats to essentially translate the flats outward. McMaster Carr is a good place to find this kind of thing, although shipping to Japan might make it uneconomical.
Thanks for the advice!
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