Advertise on Bikeforums.net



User Tag List

Results 1 to 19 of 19
  1. #1
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)

    Gouge on my seatpost.

    So I have a huge scratch on my seatpost and was wondering if anyone had any ideas what might have cause it. It looks like this:


    I felt inside the seattube and it didn't feel abnormally rough. Is this something I can fix (or at least prevent from happening again/getting worse)? Also, will the current scratch cause some problems down the road?

  2. #2
    Senior Member
    Join Date
    Aug 2010
    Location
    Washington
    My Bikes
    Serotta Davis Phinney, 1992 Serotta T Max,1984 Specialized Allez, Olmo, 1974 Strawberry,Redline bmx, ect.,
    Posts
    472
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I would hit the frame with a cylinder hone or a file down the back of the frame to eliminate the bur of the slit. If this is an aluminum post it will be fine. If it is carbon then I would say that you are over tightening the post with the QR. Most carbon posts on the newer carbon frames are only tightened 5 newton meters or about 60 in lbs.

  3. #3
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    yeah, it's just an aluminum post, so I thought at first the scrape was due to it sliding down since I'd under tightened it. Even though I have it tightened as far as I can by hand, It dropped about an inch yesterday when I rode it for an hour. Should I be using a wrench on the nut? As it is I have a hard time closing the QR. The seatpost is fairly new (and I've always had this sliding problem even though it's supposedly the same size as what came out of there. I guess I should get the calipers out and check, though I don't have the old one to compare to. How much bigger should the tube be than the seatpost when not compressed by the bolt?
    Last edited by himespau; 03-13-11 at 07:16 AM.

  4. #4
    Constant tinkerer FastJake's Avatar
    Join Date
    May 2010
    Location
    Madison, Wisconsin
    Posts
    6,014
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by himespau View Post
    I have it tightened as far as I can by hand, It dropped about an inch yesterday when I rode it for an hour. Should I be using a wrench on the nut? As it is I have a hard time closing the QR.

    How much bigger should the tube be than the seatpost when not compressed by the bolt?
    The seatpost should not slide when riding the bike. Looks like you have two possible causes:

    1. QR skewer. Exposed cam skewers like the one on your bike require more hand force to achieve the same amount of clamping force. An enclosed cam skewer will help, or just get an allen bolt. Not as convenient, but possibly less chance of getting your seatpost stolen.

    2. The seatpost shouldn't be any smaller than the inside diameter of the seat tube. Of course it has to be slightly smaller to fit, but there should be a little friction when sliding it down. If there's not any friction it can still be ok, but there should definitely not be a big amount of wobble without the QR tightened. You should not be able to see or feel a gap between the post and tube. If you can, you bought a seatpost that's too small.
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

  5. #5
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    At first it's a bit of a challenge getting the post in, but then it slides with just a little friction. Don't have visible open space. I put some grease in there (Park Polylube), because the lubricant I'd had in there wasn't visible. Hope that might help with tightness too. I think I'll stop by the lbs about getting an allen bolt for the that location as I am partial to my new (to me) saddle and would hate to lose it while my bike's parked outside while I'm at work.

  6. #6
    Constant tinkerer FastJake's Avatar
    Join Date
    May 2010
    Location
    Madison, Wisconsin
    Posts
    6,014
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Sounds like the post is the correct size. If there's an excessive amount of grease in there at the clamping area it may be more difficult to lock it down. I suspect changing to an allen bolt will solve your problem.
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

  7. #7
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    18,066
    Mentioned
    20 Post(s)
    Tagged
    1 Thread(s)
    You might want to double check for a burr at the top inside corner, but since it slipped while clamped, I'm not surprised at the scratch. You want to clamp it harder, but sometimes it's hard to get a good grip on carbon posts which are slipperier than alloy posts.

    Carbon posts need grease or anti-seize in alloy frames to avoid galvanic corrosion, but the grease lessens gripping so you're in sort of a catch 22. Here's a way to get both anti seize protection and grip at the same time.

    Don't grease the post, apply a smear of grease to the frame below the clamping area, and rotate the post as you insert it to get even coverage. Don't go below the desire height, then straighten the post and clamp the dry area. If you want still better hold, do the same but first apply a band of coarse lapping compound or carbon assembly paste to the part of the post that will be at the clamping area.
    Last edited by FBinNY; 03-13-11 at 04:13 PM.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  8. #8
    Certified Bike Brat Burton's Avatar
    Join Date
    Jan 2011
    Location
    Montreal, Quebec
    Posts
    4,203
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Do some double checking

    Suggest you get the verniers out and check both the seatpost and the inside diameter of the tube. Thats not a bare tube - its been anodized black and for steel to gouge aluminum oxide like that - something has to be seriously out of round.

    So check for maximum and minimum dimensions. You`ll still have to get rid of that metal thats causing the gouge, but quantifying your starting point is a good idea. You can ream it if you want to but if your good with your hands a dowel and wet sandpaper may be all you need and will remove less material.

    On another note, accepting that FB may have missed your post about this being an alloy post - whats all this talk about galvanic corrosion? I`ll buy lunch for the first person that can get a continuity reading off a carbon seatpost that hasn`t been so badly damaged that the carbon fibers have been exposed. At which point it might be a good idea to look for another seat post anyway!

  9. #9
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Given where the gouge is and the fact that I'm a clyde (probably 230-240#) and that there's maybe 6-8" of post exposed with the saddle as far back as it'll go on the rails (and that I squirm a lot on the saddle going up hills - and am not in the greatest shape in general so there's more weight on the saddle than there should be) I wonder if I'm just pushing the post back as it slides down and it's scraping on top where the frame raises up almost to a point right before the gap. I don't know if all frames sweep up to such a point as it looks like mine does in the picture or not. I'll definitely try feeling around in there again for any burrs, but I just didn't feel anything the last time, though I'll be the first to admit my fingers aren't super soft and sensitive.

  10. #10
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    I'm not sure I did come out and say it, but this is an alloy seatpost (el cheapo something or other 26.0 by 400 mm job from jenson) and a steel frame. I didn't pull the calipers out when I was greasing the seatpost on Sunday, but I'll recheck that it isn't supposed to be a 26.2 or something.

    Is this gouge going to affect the long term integrity of the post as long as I can stop it from getting worse? Should I buy a new post even if I can fix it?

  11. #11
    Certified Bike Brat Burton's Avatar
    Join Date
    Jan 2011
    Location
    Montreal, Quebec
    Posts
    4,203
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Doesn`t matter how much you weigh, some things aren`t supposed to move if secured properly. That includes the handlebars, gooseneck or steering stem, wheels and seatpost. Those are all safety related. I`ve heard of riders bending seatposts so that should give you some idea.

    The damage is cosmetic and you don`t need to replace the post (unless its actually the wrong size), but you really need too resolve that slipping situation. I suspect a size issue because thats the only thing I can think of that would distort the pinch bolt clamp area enough to cause gouging and still let it slip.

    Which is why I suggested the vernier. If the seat tube clamp area has been distorted you`ll need to measure in several directions to get an idea of the real situation.

    Since thats a cheepo post - it may be as simple as a QC issue too. The actual dimension may not match whats stamped on the post.

  12. #12
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,703
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    Do you need to remove the seat post? this a theft of saddle worry?

    lower wear and tear if you set it and use a regular bolt, instead of the QR.

  13. #13
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Oh once I get it set and dialed in, I have no desire to remove it. Well it is a leather saddle (selle san marco regal) and I hope to do more commuting with it so I probably don't want to leave it outside at work if it's raining, but really there's no reason for the QR once I get the height set where I want it. Just trying clipless pedals for the first time this weekend so there might be a period where I go through some height adjustments yet. Yeah, it's a cheapo seatpost (less than $20, so there might be a QC issue), so replacing it isn't a huge investment (might go with one that's not quite so long next time).

  14. #14
    Low car diet JiveTurkey's Avatar
    Join Date
    Aug 2007
    Location
    Corvallis, OR, USA
    My Bikes
    2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.
    Posts
    2,359
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Use a cover or plastic bag when leaving it out in the rain, and you'll have little reason to want to remove the post once you've got a regular bolt in there.
    Quote Originally Posted by slopvehicle View Post
    Not wearing a helmet makes me more aware of my surroundings. I find myself anticipating the hardness of concrete 50 or 100 feet in front of me, it's almost a zen-like connection between my face and the pavement.

  15. #15
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,703
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    Well it is a leather saddle (selle san marco regal)
    FWIW, Rather deluded on that, look underneath, it's a Nylon base,
    there's some dense padding sandwiched between it and the leather cover,
    there is leather but its thin, and the rivets are for style not structure
    Unlike Brooks, Ideale and some of the leather newcomers ..
    Last edited by fietsbob; 03-15-11 at 10:07 AM.

  16. #16
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Yeah I know it's plastic at the base, but I just thought that the leather cover could be damaged by rain. If that's not a worry, I'll just throw a plastic bag over it to keep my butt from getting wet the way I did my last vinyl-ish saddle.

  17. #17
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Looking at seatposts online, I'm not seeing much in 26.0. Is that not a common size?

  18. #18
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    35,703
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    Yea, A plastic bag will do .. personal fave: the Plastic Bladder out of a 5L box of wine.

    I have ridden days with a couple layers of plastic bags over even my Brooks saddle .

    Kalloy is one source of seatposts in all diameters..

  19. #19
    Senior Member himespau's Avatar
    Join Date
    Jun 2008
    Location
    Louisville, KY
    Posts
    7,176
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by fietsbob View Post
    Kalloy is one source of seatposts in all diameters..
    That's the one I have. If it turns out that the post is narrower than desired due to poor QC, I'd be looking for an alternative to them, though I suppose a shim might do the trick.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •