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Slipping seatpost, HELP!

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Slipping seatpost, HELP!

Old 07-13-20, 01:34 PM
  #1  
alij2018
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Slipping seatpost, HELP!

So, I have the Cannondale Trail 5 2020 bike, alloy frame and alloy 31.6mm seatpost with a standard quick release seat clamp. I am having a big issue recently, which is slipping seatpost.

Well, everything was OK since I bought the bike in February. I adjusted the height of seatpost after buying and all good. Recently, last week, it was the first time I completely removed the seatpost and cleaned it with a cloth as it had dirt. And the seatpost had scratches too.

I put a very thin of lithium grease so that next time it does not stuck in the frame. i applied the grease below the label of minimum insertion. I put it back, tightened the quick release with a normal force which I used to do before.

While riding, I noticed it slipped gradually after some time by 2 or 3 centimeters. I put it up again, and tightened a bit harder. It was OK but slipped by 1 centimeter only.

I retightened it again and rode some offtrack, and it slipped by 2 centimeters after some time. This was frustrating. So, I overtightened it more and it slipped by just 1 or 2 millimeters instead of centimeters.

I came back home, removed the seatpost and seat clamp as well. I inspected the frame and all good. No sign of defect etc. I sprayed the quick release with penetrating oil from Abro to eliminate corrosion or whatever. I removed the lithium grease and applied standard grease. Yes, a thin layer. I cleaned the seat tube inside a bit with a cloth. I put it back again and this time, almost overtightened the quick release. I did not test it yet. Maybe it will work or not, soon will know.

So, what are the solutions I can apply if it slips again?

1/ Should I change clamp to a bolt one?
2/ Is it slipping because of the scratches on the seatpost?
3/ Should I tighten it with more amount of force?

I am afraid to overtight it. Maybe overtightening it will work too. But I still want to use normal pressure. I'm considering buying a seat clamp with bolt. Maybe that quick release is crap.
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Old 07-13-20, 01:37 PM
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I have clean and slightly roughened the first inch of seat tube with sandpaper. They sell some seat post lube with grit in it also.

A friend of mine used a second collar that used an allen key on top of the first.
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Old 07-13-20, 02:45 PM
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Originally Posted by stevel610 View Post
A friend of mine used a second collar that used an allen key on top of the first.
I did this on 2 bikes 27.2 clamp , non QR .. 31.8mm (My Brompton) with a QR lever a frame band with a lip I had to remove..




..
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Old 07-13-20, 02:49 PM
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Good advice^^
I have also 'knurled' the seatpost with a punch where I think the clamp grabs the most. I bunch of punch marks around the post. Also clean out all the grease, degrease and use carbon fiber assembly paste... has grit in the paste. Also... get a better clamp... I like Salsa brand clamps.
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Old 07-13-20, 02:49 PM
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Try using anti-seize instead of grease. Available at your local auto parts store or good hardware store.
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Old 07-13-20, 02:52 PM
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I highly recommend: https://www.parktool.com/product/sup...compound-sac-2
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Old 07-13-20, 03:07 PM
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Owner's Manual

Please read your owner's manual (especially p. 26, and p. 75, but the rest too) and/or contact your dealer.

Excerpts:

Originally Posted by Cannondale
1. Ask your dealer to help you make sure you
know how to correctly clamp your seat post.
2. Understand and apply the correct technique
for clamping your seat post
Originally Posted by Cannondale
If you can fully close the cam lever without
wrapping your fingers around the seat post or a
frame tube for leverage, and the lever does not
leave a clear imprint in the palm of your hand,
the tension is insufficient. Open the lever; turn
the tension adjusting nut clockwise a quarter
turn; then try again.
Originally Posted by Cannondale
■ Seat Post Lubrication Clean and apply the following to a seat post before inserting into the frame.
  • Alloy Seat Tube & Alloy Seat Post = Grease
  • Alloy Seat Tube & Carbon Post = Carbon Gel
  • Carbon Seat Tube & Alloy Seat Post = Carbon Gel
  • Carbon Seat Tube & Carbon Seat Post = Carbon Gel
- A high-quality bicycle bearing grease CARBON GEL
- Is a gel like lubricant formulated for use with carbon fiber components (Cannondale p/n KF115/).
-mr. bill

Last edited by mr_bill; 07-13-20 at 03:15 PM.
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Old 07-13-20, 03:33 PM
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Change to a bolt on seat post clamp. Quick release clamps are awful.
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Old 07-13-20, 03:52 PM
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I have a folding bike, seat post pushed down locks the fold, so It has to be QR, in my case they're stacked so I open both levers @ once..
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Old 07-13-20, 09:00 PM
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alij2018
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Originally Posted by fietsbob View Post
I did this on 2 bikes 27.2 clamp , non QR .. 31.8mm (My Brompton) with a QR lever a frame band with a lip I had to remove..




..
Can you post a pic how you did it?
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Old 07-13-20, 09:03 PM
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alij2018
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Originally Posted by mr_bill View Post
Owner's Manual

Please read your owner's manual (especially p. 26, and p. 75, but the rest too) and/or contact your dealer.

Excerpts:







-mr. bill
Done all the procedures. I used grease, tightened fully abd harder, and seat clamp is correctly positioned, did that several times in life.
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Old 07-13-20, 09:03 PM
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alij2018
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Originally Posted by dsaul View Post
Change to a bolt on seat post clamp. Quick release clamps are awful.
I will do that yes
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Old 07-13-20, 09:05 PM
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alij2018
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Originally Posted by stevel610 View Post
I have clean and slightly roughened the first inch of seat tube with sandpaper. They sell some seat post lube with grit in it also.

A friend of mine used a second collar that used an allen key on top of the first.
You sandpaper last inch at the bottom fully until the entire paint came off? What this will do?
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Old 07-13-20, 09:43 PM
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fietsbob
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Originally Posted by alij2018 View Post
Can you post a pic how you did it?
A file .. 1/2 round on one side flat on the other.. 12 " long including tang..




Nicholson a good brand of files



...

Last edited by fietsbob; 07-13-20 at 09:50 PM.
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Old 07-13-20, 09:58 PM
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alij2018
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Originally Posted by fietsbob View Post
A file .. 1/2 round on one side flat on the other.. 12 " long including tang..




Nicholson a good brand of files



...
I did not understand bro
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Old 07-13-20, 10:09 PM
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fietsbob
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sorry, read more .. educate yourself...
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Old 07-14-20, 07:48 AM
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Good advice here but really the bike is under warranty and this shouldn't be your problem to fix. You shouldn't have to purchase a new seat post clamp or anti-seize or knurled the seat post. It is fine if you want to but I would be taking the bike back to the bicycle shop where you bought it and have them deal with it.
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Old 07-14-20, 02:00 PM
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Clean the goop off from both areas & smear some extra hold hair gel on the post. Tighten it down & let it sit for 30 minutes while you clean your chain, wheels, & check psi while also getting the mail. After 30 minutes, your seat should stay at height. To remove the seat post, loosen the flange of all its tension, & with a rapid twisting motion while lifting up, it should remove freely. Cleaning & Reapplying gel is needed when the hardware tension has been released.
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Old 07-14-20, 03:04 PM
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Crazy thought. Are you actually riding down trails now that the weather is nice? Get out of the saddle. (I would think this is self teaching on hard-tails, hell, self teaching on any tails, but....)

-mr. bill
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Old 07-14-20, 05:45 PM
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As is so often the case, the answer may be beer. Drink a can, then cut a strip of the aluminum can approx. 1/2" wide and 2' long. Use this as a shim to firm up the clamp's grip on the post.
Good luck
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Old 07-14-20, 10:38 PM
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frogman
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Originally Posted by stevel610 View Post
I have clean and slightly roughened the first inch of seat tube with sandpaper. They sell some seat post lube with grit in it also.

A friend of mine used a second collar that used an allen key on top of the first.


I use the second collar on top of the seatpost clamp also. Works great, easy, and looks good.
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Old 07-15-20, 05:39 AM
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Originally Posted by alij2018 View Post
I put a very thin of lithium grease so that next time it does not stuck in the frame. i applied the grease below the label of minimum insertion. I put it back, tightened the quick release with a normal force which I used to do before.
I am also using regular lithium complex EP grease. No problems so far.

Although I have adjusted my quick release seat post clamp that it takes both my thumbs (from the left and right hands) to lock it. The quick release is a little bit tight if you ask me.

1/ Should I change clamp to a bolt one?
I've done this recently as saddle anti-theft measure. No problems with this too.

2/ Is it slipping because of the scratches on the seatpost?
I have some scratches on mine too and it's perfectly fine

3/ Should I tighten it with more amount of force?
Assuming the seatpost width is correctly sized for the frame, Then you probably need to tighten it with more force. I use both thumbs on mine to lock the quick release.
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Old 07-15-20, 06:08 AM
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Originally Posted by Boerd View Post
+1 It's basically the whole point of this stuff.
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Old 07-15-20, 11:11 AM
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Frame's seat tube 31.8? , seat post 27.2?

these look excellent : https://www.sjscycles.co.uk/seat-pos...18-mm/?geoc=US

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Old 07-15-20, 11:31 AM
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Can we just file this as yet another “Everything worked great until I 'fixed' it” thread?

-mr. bill

Last edited by mr_bill; 07-15-20 at 12:08 PM.
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