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  1. #1
    g3h6o3
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    HOXPLATST5 seat post end size

    Hello,
    does anybody have experience with True Temper HOXPLATST5 seat tubes and could tell me the external diameter at the seat post? I think it should be 29.8mm given it takes 30.0mm collars but I measured otherwise (at 29.2mm). I'm looknig for a confirmation.

    Thanks
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  2. #2
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    Should be 29.4mm

    That tube is notoriously often out of spec, but it *should* be about 29.4mm (meaning you'll need a 29.6 or 29.8 collar, depending on how thick the finish is). A 30.0 collar probably also works in most cases.

    -Walt

    Quote Originally Posted by PissedOffCil View Post
    Hello,
    does anybody have experience with True Temper HOXPLATST5 seat tubes and could tell me the external diameter at the seat post? I think it should be 29.8mm given it takes 30.0mm collars but I measured otherwise (at 29.2mm). I'm looknig for a confirmation.

    Thanks
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  3. #3
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    I got 29.4- 29.6mm on my two at that end. Wish I would have known about its reputation a while ago. It was alarming when I got to them to make my fork last week, and measured. Wide variance in wall thickness!

  4. #4
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    I have the same experience as you, I only have one thankfully. It's totally off spec and un-useable as a ST. I think on average mine was 9/6/9...? I couldn't tell which end was the external butt.
    It's weird!

  5. #5
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    Don't use it for forks!

    You can still find pics on the interwebs of at least one of the forks I built with those seat tubes 7 or 8 years ago. Learned an important lesson about checking butts for every tube before using them...

    Honestly the 1.1 wall is IMO too thin for most people for a fork blade unless you're sleeving it somehow. The Nova 1.2mm wall seat tubes are a better choice (though big/aggro people will break those too).

    -Walt

    Quote Originally Posted by LemonFool View Post
    I got 29.4- 29.6mm on my two at that end. Wish I would have known about its reputation a while ago. It was alarming when I got to them to make my fork last week, and measured. Wide variance in wall thickness!
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  6. #6
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    Good to know

    I was pretty sketched out after measuring the tubing. I actually called, thinking I had been sent the wrong tubes. It wasn't the only one either, which was disappointing. I'll have to find some different options.

  7. #7
    dru
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    I used that tube on my frame and yes it was way out of spec. I ended up flipping it after changing my design slightly. Once I inverted it a 26.8 seat post fit perfectly on the finished frame.

    Drew
    occasional cyclist

  8. #8
    g3h6o3
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    Thanks for the answers guys. The frame builder refuses to admit the tube is out of spec and insists that my Thomson Elite seatpost is too small and that is what causes the problems I'm having.

    I can for sure forget about using non steel seat post collars as the deformation puts too much pressure on the bolt and it snaps. I don't really know what to do about all this... thanks for helping anyways.
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  9. #9
    g3h6o3
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    Hello again,
    There has been some development and I wanted your guys advice on this issue once more. It turns out my Masterpiece seat post has been crushed at the seatpost clamp, most probably by over tightening it because of reccuring seatpost slippage. Thomson are being amazing on this issue and are offering to replace the post regardless that it is not their fault but I first want to set thing straight with the builder as I believe they should take responsibility.

    Therefore, my question is the following: How does using a too big clamp on a tube affect the seat post? I believe that the deformation on the clamp caused by the gap between it and the seat tube will produce a non-uniform clamping force on the seatpost which will in turn force you to over tighten the clamp for the post to hold in place. Am I right about this assumption? I'm not a mechanical engineer so I can't back it up this deduction with theory but all carbon parts warn you against this situation so it sounds reasonable to me.

    Thanks again folks
    Check out my SportTracks plugins for some training aid software.

  10. #10
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    The bottom line

    IMO if the post is slipping and you just keep cranking harder on the bolt to stop it, you are 100% at fault, even if the collar supplied with the frame wasn't quite the right size. Torque specs exist for a reason and it takes a LOT of force to crush a seatpost. If you went bananas on the bolt, you destroyed the post, full stop.

    IMO you should ask the builder for the correct size collar or a few bucks to buy one. Beyond that, I don't think they are responsible for the post, unless they specifically told you to just keep cranking the bolt down, or the post doesn't fit the frame correctly.

    I guess the other part of this is that until you've presented all this to the builder and sorted it that way, I'm not sure what good it does to ask us here.

    -Walt


    Quote Originally Posted by PissedOffCil View Post
    Hello again,
    There has been some development and I wanted your guys advice on this issue once more. It turns out my Masterpiece seat post has been crushed at the seatpost clamp, most probably by over tightening it because of reccuring seatpost slippage. Thomson are being amazing on this issue and are offering to replace the post regardless that it is not their fault but I first want to set thing straight with the builder as I believe they should take responsibility.

    Therefore, my question is the following: How does using a too big clamp on a tube affect the seat post? I believe that the deformation on the clamp caused by the gap between it and the seat tube will produce a non-uniform clamping force on the seatpost which will in turn force you to over tighten the clamp for the post to hold in place. Am I right about this assumption? I'm not a mechanical engineer so I can't back it up this deduction with theory but all carbon parts warn you against this situation so it sounds reasonable to me.

    Thanks again folks
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  11. #11
    g3h6o3
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    Well not exactly. Thomson accuses the builder becasue of the tube size and says that using a 30mm clamp on the frame will always "crush" the seatpost. On the other hand, the builder says that the collar has no effect and that the problem is the seatpost that is too small. I'm in the middle trying to resolve the issue...

    With that said, I haven't torqued the collar more than required to hold the post in place, even with friction paste, yet it has worn prematurely... It hasn't really crushed although Thomson used that word. What I see is that the post got thinner at the clamp, the grooves slowly got "sanded" down.
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  12. #12
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    Do other 27.2 posts fit?

    If the frame ST inside diameter is too large, that's your problem, not the collar. Try some other 27.2 posts and see if they fit looser/tighter than the Thomson, and there is your answer. You can also just whip out the calipers and measure the post. In my experience Thomson stuff is pretty dead on, and in my experience the ST5 seat tube is the opposite, so my suspicion would be a seat tube that is a little too big. But the only way to find out is to measure.

    -Walt

    Quote Originally Posted by PissedOffCil View Post
    Well not exactly. Thomson accuses the builder becasue of the tube size and says that using a 30mm clamp on the frame will always "crush" the seatpost. On the other hand, the builder says that the collar has no effect and that the problem is the seatpost that is too small. I'm in the middle trying to resolve the issue...

    With that said, I haven't torqued the collar more than required to hold the post in place, even with friction paste, yet it has worn prematurely... It hasn't really crushed although Thomson used that word. What I see is that the post got thinner at the clamp, the grooves slowly got "sanded" down.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  13. #13
    g3h6o3
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    The ST inner diameter is 27.25 and the post is dead on except where it used to clamp.

    Quote Originally Posted by Walt View Post
    If the frame ST inside diameter is too large, that's your problem, not the collar. Try some other 27.2 posts and see if they fit looser/tighter than the Thomson, and there is your answer. You can also just whip out the calipers and measure the post. In my experience Thomson stuff is pretty dead on, and in my experience the ST5 seat tube is the opposite, so my suspicion would be a seat tube that is a little too big. But the only way to find out is to measure.

    -Walt
    Check out my SportTracks plugins for some training aid software.

  14. #14
    Nemophilist
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    Hey;

    I am not sure what you used to make your measurements. To bolster your position in terms of accuracy and veracity, I might offer that any ID measurement that is anywhere near critical is best made with something other than a caliper, as they are not very accurate for that task. At the least, a telescoping gauge, then measured with a mic would be far superior. Even then, several readings taken to form a consensus on the spec would be best.

    Calipers are more suited to OD measurements. Short of a dial bore gauge or hole mic, the above method is a more accurate method for ID measuring. In the case of a seat post, I'd say that thousandths matter, and particularly so when you are trying to prove a point.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  15. #15
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    bore gauges are cheap and well worth having around

    I usually wouldn't recommend buying Chinese measuring tools, but as long as a telescoping gauge expands properly it's hard to screw it up too bad. Shars is giving this set away at $26

    If you buy a Starrett, make sure it works before you hand over your money.

  16. #16
    Nemophilist
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    Quote Originally Posted by unterhausen View Post
    Shars is giving this set away at $26. If you buy a Starrett, make sure it works before you hand over your money.
    Ha!

    No kidding. From what I hear, they might be the same thing!!
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  17. #17
    Harrumph
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    Unless I missed it you didn't say what type of clamp you were using. If you should have been using something smaller than 30.0 you may have been clamping the post not the seat tube. And probably clamping with just the lip at the top of the collar. And if you then went Hulk on the bolt it's no surprise the post came out on the poop end of the stick. I'd Suggest something like a Salsa Lip Lock where the threaded portion is in a barrel so the bolt isn't doing strange things as it's tightened.

    I'd say step down a size on a clamp and try that. A little pop can shim under the collar could be used with your 30.0 clamp to test if that's the problem.



    I've used 30.0 clamps on the frames I've built and had an OHF*&K moment a few times when slapping them together before powdercoat because the clamp was nearly bottoming out before clamping the post.
    Slowly slipping to retrogrouchyness

  18. #18
    g3h6o3
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    I've used the clamp that came with the frame, which is a basic no name steel clamp. I tried using a Hope and since the tube is so out of tolerance the bolt snapped before I could get my seatpost to stop slipping. That is when I started beleiving something was out of whack and I started investigating from then.

    When I replaced the bolt on the Hope collar, I noticed that deformation on the collar was so big it could in no way hold the post in place. In fact, only about 20 degrees of the bolt was still touching the collar which is probably why the first one snapped, the "side load" was probably too much.

    P.S. The 29.2mm I measured is with paint. I used a vernier for all my calculations and given I'm not a frame builder, it's plenty for my usual needs.

    Quote Originally Posted by G-reg View Post
    Unless I missed it you didn't say what type of clamp you were using. If you should have been using something smaller than 30.0 you may have been clamping the post not the seat tube. And probably clamping with just the lip at the top of the collar. And if you then went Hulk on the bolt it's no surprise the post came out on the poop end of the stick. I'd Suggest something like a Salsa Lip Lock where the threaded portion is in a barrel so the bolt isn't doing strange things as it's tightened.

    I'd say step down a size on a clamp and try that. A little pop can shim under the collar could be used with your 30.0 clamp to test if that's the problem.



    I've used 30.0 clamps on the frames I've built and had an OHF*&K moment a few times when slapping them together before powdercoat because the clamp was nearly bottoming out before clamping the post.
    Check out my SportTracks plugins for some training aid software.

  19. #19
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    At this point

    If you're at 29.2mm WITH paint, something is very wrong with the seat tube. That is ~.9mm wall thickness (maybe a bit less depending on how thick the paint is) which is going to mean problems down the road with the seat tube cracking (at least in my experience - don't ask how I know this...) at the seatstays.

    But that's in the future, and it might be fine. For now you just need a collar that fits and a new post. Sounds like the post is taken care of. The collar will be harder - IRD used to make a 29.4 or 29.6 but I don't know if they still do. You could shim with coke can material (easier than it sounds) or ask the manufacturer to add a brazed-on binder bolt. You could have someone take a little material off of a 28.6, too.

    -Walt



    Quote Originally Posted by PissedOffCil View Post
    P.S. The 29.2mm I measured is with paint. I used a vernier for all my calculations and given I'm not a frame builder, it's plenty for my usual needs.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  20. #20
    dru
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    Quote Originally Posted by Walt View Post
    If you're at 29.2mm WITH paint, something is very wrong with the seat tube. That is ~.9mm wall thickness (maybe a bit less depending on how thick the paint is) which is going to mean problems down the road with the seat tube cracking (at least in my experience - don't ask how I know this...) at the seatstays.

    -Walt
    My tube was that thickness 0.9 mm on one side and maybe 1 mm on the other, which is precisely why I didn't use it as intended. I'm a total hack and noticed the tube was out of spec. It wasn't hard to see.

    Drew
    occasional cyclist

  21. #21
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    Always gotta measure

    I am actually repairing a frame right now that I built ~8 years ago with an ST5 seat tube. I learned a lot of lessons the hard way about measuring butts when I started out!

    True Temper makes awesome stuff but their external butt seat tubes are a joke. It's like they never figured out how to do it right but just kept selling them anyway. Weird.

    -Walt

    Quote Originally Posted by dru View Post
    My tube was that thickness 0.9 mm on one side and maybe 1 mm on the other, which is precisely why I didn't use it as intended. I'm a total hack and noticed the tube was out of spec. It wasn't hard to see.

    Drew
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  22. #22
    dru
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    28.6 mm (1.125") External Butted Seat Tubes - SEAT POST DIAMETER = 27.2 mm

    .9\.6\1.22^ S3 SALST1 $21.60

    Walt, any info/experience on this one? I've been talking about building an S3 road frame for a few years now, and finally drew up a blueprint and selected my tubing. Haven't ordered yet.

    Thanks, Drew
    occasional cyclist

  23. #23
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    Just sleeve something

    .9/.6 is nothing special. Why spend $22 for that? Just put a sleeve at the top and you can control the thickness yourself!

    As an aside, S3 is dumb. It's just OX Platinum with really short, thin butts. Probably only saves 50-100 for the whole frame and it's scary, scary thin at the joints.

    -Walt

    Quote Originally Posted by dru View Post
    28.6 mm (1.125") External Butted Seat Tubes - SEAT POST DIAMETER = 27.2 mm

    .9\.6\1.22^ S3 SALST1 $21.60

    Walt, any info/experience on this one? I've been talking about building an S3 road frame for a few years now, and finally drew up a blueprint and selected my tubing. Haven't ordered yet.

    Thanks, Drew
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  24. #24
    g3h6o3
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    Thanks Walt and the others. I'll try to settle this with the manufacturer based on your opinions and the feedback from Thomson. When I spoke to the president a coupel of weeks ago he wasn't looking to replace the frame but I think I have a better understanding and confirmation of my doubts by various knowledgable sources now.

    Needless to say I'm not buying or reccomending the brand to anyone from now on. I won't name them until it's over though, they still have a chance to settle this but as far as brand trust, it's over for my part.
    Last edited by PissedOffCil; 12-20-2012 at 10:33 AM.
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