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Discussion Starter · #1 ·
What size seatpost does a 2003 Razorback 4.0 take? I thought it was 31.6 but the post I bought is just barely too big.:madman:
 

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That should be correct...

31.6mm is the correct size post to fit that bike. I have a Razorback 3.0 from the same year, and recently swapped from Ritchey to Truvativ posts lately to scoot myself a little further forward on the bike. Both posts were marked as 31.6mm and slid in fine.

I assume that your frame, as mine was, was used before you owned it, and that there isn't any paint overspray inside or on top of the seat tube which is causing the problem.

Here's what I would suggest:

  • Take the seat post clamp completely off the bike.
  • With no clamp, try inserting the post again. It could be that particular clamp is a tight fit over the paint and metal, slightly squeezing the slot closed without much help from the allen bolt or QR.
  • With the clamp off, look carefully and/or measure the width of the slot at the top of the seat tube and close to the bottom, just before the slot ends in a round keyhole. If it's significantly narrower on top, something has happened to close up the hole.
  • Measure the inner diameter of the seat tube in a couple of different orientations, preferably with calipers. If it's not roughly equal all the way around, something has happened to ovalize the hole.

It's hard to diagnose the exact nature, degree or cause of the problem in words. If it is just "barely" too big, then flex honing or lightly reaming the seat tube should restore the intended inner diameter.

A good bike shop should have the tools and expertise to do this well. Bring them the seat post that you want to use, so they can test it to make sure there's a good fit. Not all posts that are marked as the same size actually measure out the same actual diameter.

Good luck, and tell us what you find!

T.K. Malone
K2 Bike
 

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Discussion Starter · #3 ·
thekid said:
31.6mm is the correct size post to fit that bike. I have a Razorback 3.0 from the same year, and recently swapped from Ritchey to Truvativ posts lately to scoot myself a little further forward on the bike. Both posts were marked as 31.6mm and slid in fine.

I assume that your frame, as mine was, was used before you owned it, and that there isn't any paint overspray inside or on top of the seat tube which is causing the problem.

Here's what I would suggest:

  • Take the seat post clamp completely off the bike.
  • With no clamp, try inserting the post again. It could be that particular clamp is a tight fit over the paint and metal, slightly squeezing the slot closed without much help from the allen bolt or QR.
  • With the clamp off, look carefully and/or measure the width of the slot at the top of the seat tube and close to the bottom, just before the slot ends in a round keyhole. If it's significantly narrower on top, something has happened to close up the hole.
  • Measure the inner diameter of the seat tube in a couple of different orientations, preferably with calipers. If it's not roughly equal all the way around, something has happened to ovalize the hole.

It's hard to diagnose the exact nature, degree or cause of the problem in words. If it is just "barely" too big, then flex honing or lightly reaming the seat tube should restore the intended inner diameter.

A good bike shop should have the tools and expertise to do this well. Bring them the seat post that you want to use, so they can test it to make sure there's a good fit. Not all posts that are marked as the same size actually measure out the same actual diameter.

Good luck, and tell us what you find!

T.K. Malone
K2 Bike
Thanks for your help. I put the seatpost in another bike with a seat tube the same size and it went in okay. I'm thinking the previous owner just had the seatpost clamp done up too tight without a tube in it. I'll take it to the bike shop today and see what they can do about it.

Just got my final part for the build today. Hopefully I'll have it ready to ride before the weekend.
 

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No problem. Hope it all works out, and that you have fun riding this weekend. Let us know how it went.

T.K.
 
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