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Old 02-25-09, 11:32 AM   #1
kamtsa
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Vitesse seat post slides down

My son got recently a Dahon Vitesse D7HG from a LBS. Overall he is very happy with it and it look really good after removing fenders and rack.

The main issue he has with the bike is that the seat post slides down a inch or two every few miles (he is a big guy).

The seat post does not seem to be lubricated and we tried to tighten the QR as much as possible.

Any suggestion how to secure the seat post?

Thanks,

Kam
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Old 02-25-09, 11:36 AM   #2
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One ugly way is to adjust the seat to the right height, then wrap a round or two of good quality duct tape at the seam where the QR is. Note: you don't wrap the QR, rather, you tape the section of seat post just above where the QR receives the seatpost.

There is also a special friction lube that bike shops use to lube seat posts that slide.
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Old 02-25-09, 01:13 PM   #3
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Grease the Q/R and lightly grease the contact area between frame and shim, and make sure the seat post and shim interior is clean. That more or less worked for me.

Though too much grease between shim and frame can mean that the shim slides out when pulling up the seat post, so it's a balancing act.


I've recently switched to a I-beam seat post which is very slightly ridged on the outside and I have zero slippage problems with it. Seems that all Dahon seat posts should be that way.
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Old 02-26-09, 10:05 AM   #4
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Quote:
Originally Posted by puppypilgrim View Post
One ugly way is to adjust the seat to the right height, then wrap a round or two of good quality duct tape at the seam where the QR is. Note: you don't wrap the QR, rather, you tape the section of seat post just above where the QR receives the seatpost.

There is also a special friction lube that bike shops use to lube seat posts that slide.
Thanks. I will give it a try.

Any other suggestion? (roughing up the seat post? sparying abrasive material? stronger QR?)

Kam
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Old 02-26-09, 10:29 AM   #5
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I have the same problem. I got a post long enough to hit bottom.
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Old 02-26-09, 10:31 AM   #6
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If this is a new bike, I would go back to the LBS and trade out the seatpost. They seem to vary a tiny amount in size. I have had two on my DT mini and they fit differently.
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Old 02-26-09, 10:48 AM   #7
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Grease between shim and frame will allow pressure to be evenly distributed around the seat post.
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Old 02-26-09, 02:58 PM   #8
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This is what I would do...

1. Clean shim and seatpost as well as you can so there is not the slightest chance of any greasiness.

2. If this does not work, put a drop of oil or better Boeshield T-9 on the QR sliding interfaces; this will dramatically reduce the force needed to close the QR and allow more clamping force with hardly extra force. Do this step anyway.

3. If this does not work get some Ritchey Liquid Torque and apply a SMALL amount on the shim at the top only where the clamp clamps. This will certainly cure it. Some clean fine sand in grease will do the same. Hopefully the grit will become embedded in the shim and be permanent.

4. If this does not work, cut a square of plastic or aluminium from a drink bottle/can and use that as additional shim between shim and seat tube.

5. If this doesn't work, it is time to visit the LBS for a guarantee issue. Posts must not slide down, period.
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Old 02-26-09, 04:18 PM   #9
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I just had the same exact problem with my folder. The seat post slides down little by little every few miles and before I knew it, my knees were in my chest, LOL!

I used rubbing alcohol on a clean cloth and cleaned the seat post really well. Then I used rubbing alcohol to clean the inside where you insert the seat post. Also, I placed a few drops of lubricant into the Quick Release lever and worked it in by opening and closing the QR lever.

Amazingly, this fixed the problem! I no longer have a slippage problem and can now comfortably ride my bike. You should try it.

Good luck!

Last edited by KitN; 02-26-09 at 04:22 PM.
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Old 02-27-09, 10:49 AM   #10
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Thanks everybody for the good suggestions. I will start implementing them this weekend.

Kam
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Old 03-03-09, 09:55 PM   #11
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Quote:
Originally Posted by jur View Post
This is what I would do...

1. Clean shim and seatpost as well as you can so there is not the slightest chance of any greasiness.

2. If this does not work, put a drop of oil or better Boeshield T-9 on the QR sliding interfaces; this will dramatically reduce the force needed to close the QR and allow more clamping force with hardly extra force. Do this step anyway.
A quick update, we tried last weekend Jur's steps 1 and 2 (using Triflow). The lube definitely made the QR easier to tighten but the seat still keeps sliding down.

I will order today the Ritchey anti grease stuff so we can try step 3.

When my son folds his bike he always take out the seat post (as opposed to inserting it all the way in) so I wonder if some well tighten clamp on the seat post, with some loctite, is a good solution. It will not let the seat to slide in and since the clamp does not need to be remove for each fold, the loctite can keep it in place very hard.

Kam
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Old 03-05-09, 10:27 PM   #12
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Did you use rubbing alcohol? Because if you used normal soap and water the soap can leave a film that can make the seat slide down. So please use rubbing alcohol to clean the seat post thoroughly as well as the "shim" and the inside of where you will insert the seat post.

Good luck.
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Old 03-06-09, 08:13 AM   #13
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Another thing: inspect the clamped post and see if the shim is making contact all the way round, or whether there's any visible gap.
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Old 03-06-09, 08:57 AM   #14
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I am still tipping on a too loose quick release... those buggers need to be clamped down pretty good
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Old 03-08-09, 04:39 AM   #15
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Has any body tried hairspray on their seatpost to making it tacky as its great for sticking grips on?
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Old 03-27-09, 12:04 PM   #16
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Another update, after few weeks of riding, it seems that Jur's #1, #2 suggestions stopped the sliding. I also got the Ritchey stuff but have not had a chance to apply it. Recently we installed on that bike a thudbuster (for suspension reasons, not for solving the sliding issue). The thudbuster post is machined to be rough so now the seat holds even better.

Problem solved.

Thanks,

Kam
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Old 03-27-09, 03:15 PM   #17
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Thanks for the feedback - this is valuable.
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Old 03-28-09, 07:36 PM   #18
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Quote:
Originally Posted by Ohno Notyou View Post
Didn't you buy a seatpost that hit the bottom?
Why not?
Ohno
With the vitesse, the bottom means the road so this is not an option.

May work with other bikes, don't know. It will also limit the adjustability of the seat height.

Kam
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Old 03-29-09, 05:24 AM   #19
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KiTN, I just worked out what that pic was on your signature... OMG !!!
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Old 03-29-09, 08:22 AM   #20
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Clean the post and inside of the seat tube with 91% isopropyl alcohol. Mark the seat post at the desired seat height. Rub some chalk (plain, white chalk...not the colored/artsy stuff) starting from the mark you made on the seat post to 3 inches down the post. Insert post and tighten quick release.
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Old 03-29-09, 08:49 AM   #21
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KiTN, I just worked out what that pic was on your signature... OMG !!!
It shows the time of day, like a sun dial.
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Old 03-29-09, 12:02 PM   #22
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Next time you have a seatpost sliding issue - do NOT tighten the QR more than reasonable. The D7's QR is of the external cam type e.g garbage. Overtightening will wear the plastic cam interface out. Your shop probably does not stock this part!
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Old 03-29-09, 09:49 PM   #23
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Quote:
Originally Posted by late View Post
I have the same problem. I got a post long enough to hit bottom.
LOL! Dahon seat tubes don't have a bottom. The bottom is the ground. You lower the seat so you can fold the bike.
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Old 03-29-09, 10:02 PM   #24
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Quote:
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KiTN, I just worked out what that pic was on your signature... OMG !!!
OMG is right! Also, "WTF" came to mind, too! Spandex + Men = Just Plain Wrong! Eww!

Kam, I'm glad you got the situation sorted out. Sliding seat posts are worse than spandex moose-knuckle.

Last edited by KitN; 03-29-09 at 10:05 PM.
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Old 03-29-09, 10:52 PM   #25
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Quote:
Originally Posted by james_swift View Post
... Rub some chalk (plain, white chalk...not the colored/artsy stuff) ..
Chalk as a way to increase friction. Interesting, I will try to remember this trick.
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