seatpost slipping: suggestions?

[Climb01742]

so here's my situation: aluminum post in a steel frame. and it's slipping.

originally it was just post in frame. after having it slip considerably, i applied grease inside the top of the seat tube. this mitigated the slippage but it still loses a few mm's each ride.

any suggestions for further fixes to keep the alu post from slipping?

one option, adam hansen uses a second seat collar. thoughts?

http://www.cyclingnews.com/features/photos/pro-bike-adam-hansens-ridley-helium-sl/297688

another option is to try another post. but it's a 31.6 post and only other one i have is carbon. if i try the carbon, i assume i should clean out the grease from the seat tube and apply carbon paste? any downside to residual grease mixing with carbon paste?

to sum up my situation in a word: help!

thanks!

[oldpotatoe]

so here's my situation: aluminum post in a steel frame. and it's slipping.

originally it was just post in frame. after having it slip considerably, i applied grease inside the top of the seat tube. this mitigated the slippage but it still loses a few mm's each ride.

any suggestions for further fixes to keep the alu post from slipping?

one option, adam hansen uses a second seat collar. thoughts?

http://www.cyclingnews.com/features/photos/pro-bike-adam-hansens-ridley-helium-sl/297688

another option is to try another post. but it's a 31.6 post and only other one i have is carbon. if i try the carbon, i assume i should clean out the grease from the seat tube and apply carbon paste? any downside to residual grease mixing with carbon paste?

to sum up my situation in a word: help!

thanks!

Good bike shop will have a knurling tool...makes ridges in post, no slip no mas.

[Ken C]

I had the same problem with a cheap steel commuter frame a Pake C'Mute.

I use carbon paste on an aluminum post and now it does not slip without having to result in excessive torque on the binder bolt.

[Grant McLean]

The very smooth and polished Easton Dura-Ace post used to slip in my Kirk,
and i put some of the Finish Line fiber grip on it, which seems to have solved
the problem.

http://www.finishlineusa.com/products/specialty-products/fiber-grip-

-g

[Ken C]

The very smooth and polished Easton Dura-Ace post used to slip in my Kirk,
and i put some of the Finish Line fiber grip on it, which seems to have solved
the problem.

http://www.finishlineusa.com/products/specialty-products/fiber-grip-

-g

That is the same stuff I use.

[vqdriver]

Doesn't have to be carbon to use carbon paste.

[shovelhd]

That is the same stuff I use.

Me too. Cheap and effective.

[RobJ]

Another cheap, simple solution is a piece of tape wrapped around the post at the position where it would meet the top of the seat tube. Some type of tape that has a cloth/fabric backing.

[Tony T]

I had this problem and it was the fastening nut that was not staying tight (5nm).
A little loc-tite on the threads solved it.

[Peter P.]

Make sure the clamp bolt is not bottoming out at the coincidental torque to give you SOME clamping force but not ENOUGH.

I've read that grease on carbon posts does something bad like penetrate the epoxy, making the post slip even more and after that, difficult to remove the grease's effect.

Measure your 31.6 post to verify it's not undersized.

According to my Sutherland's manual, the seat tube for your particular mating of steel frame to aluminum post, the seat TUBE can be as large as 31.8mm and still work with your post. Ideally, the seat TUBE would be no larger than 31.65mm.

You could have the "perfect storm" of an oversized seat tube AND undersized seat post.

My only concern with using carbon past is, will it prevent rust in the seat tube and impair seizing of the seat post.

[shovelhd]

My only concern with using carbon past is, will it prevent rust in the seat tube and impair seizing of the seat post.

That's what it is designed to do. It's just grease with grit in it.

[Dead Man]

I had this problem.... I finally realized my seatpost clamp had a crack in it. I used my tail light clamp as a brace of sorts to try to get me the last 50 miles, but it finally broke all the way through and I had to low-rider it to a bike shop for a temp clamp. Fortunately, I was a few miles from a shop- 'cause I probably looked like an idiot

But I obviously rode around with it cracked for some time- I hadn't had any problems, then one day I noticed it had slipped and from that point on I never could get it tight.

[fogrider]

A buddy had this problem and had the post knurled. It was fine until the post snapped. Go with paste. Check tube diameter, steel can stretch.

[Boar]

I had the same problems with my steel and carbon frames, solved with this:
http://www.effettomariposa.eu/en/products/carbogrip/

[p nut]

I have an aluminum EBB in a steel frame. I use this stuff called Oatey's Joint Compound (from Home Depot). No slip and works great. Manufacturer suggests Carbogrip if this doesn't work, but no issues for me. And only $2 for a tube.

[mike p]

Ck your seat post, not uncommon for them to be under and oversized.

I see this all the time and it always looks like such a engineering band-aid especially on a high end bike!

"one option, adam hansen uses a second seat collar. thoughts?"

[oliver1850]

I would measure the post and look for a slightly bigger one if the paste doesn't work. They can vary quite a bit with the same nominal size.

Another option is the double clamp if the frame uses a collar. Origin8 sold them, they clamp on the frame and the post.

http://www.ebay.com/itm/Origin-8-CLAMP-OR8-SAVER-31-6-34-9-BK-Black-Bicycle-Pro-Pulsion-Post-Saver-/320978301420?pt=US_Saddles_Seats&hash=item4abbcc31ec

[Anarchist]

A beer can shim on the inside of the post works really well.

Have one on my Pegoretti for years now.

[linger]

Buy a thomson seat clamp.

[victoryfactory]

Assuming the sizes are all good and the bolt is not bottoming out
as mentioned by Peter, clean all the grease out and surface the inside
of the clamp/seat tube with sandpaper. That works for me cause you don't have to
do anything to the post itself.

VF

ps: try every one of these fixes and let us know the results. It shouldn't
take more than 6 or 8 months!

[Climb01742]

Partial update: I tried a different seatpost and it slipped too. My next two steps are to buy some calipers to confirm that the seat tube is, as appears, larger than stated and track down some Tacx carbon assembly paste. Fingers crossed. Frustrating.

And thank you everyone for all of your suggestions. The help is very appreciated.

[azrider]

Partial update: I tried a different seatpost and it slipped too. My next two steps are to buy some calipers to confirm that the seat tube is, as appears, larger than stated and track down some Tacx carbon assembly paste. Fingers crossed. Frustrating.

And thank you everyone for all of your suggestions. The help is very appreciated.

Hey Climb.....what ever ended up happening with your slippage issue?

I'm obviously bumping because I'm having same issue with my CSI.

:crap::crap::crap:

[oldpotatoe]

Hey Climb.....what ever ended up happening with your slippage issue?

I'm obviously bumping because I'm having same issue with my CSI.

:crap::crap::crap:

Find a decent lbs that has a knurling tool, knurl it dear liazza, knurl it.

[azrider]

Find a decent lbs that has a knurling tool, knurl it dear liazza, knurl it.

Thanks for chiming in here OP. Unfortunately, the post I have is already knurled (that a word?) so that aint an option.

Background: I over-tightened seatpost bolt and broke it off in the seatpost cluster and had to have it backed out. :mad::mad::mad:

My shop lubbed it up really well and put stainless steel screw in there and now I'm too much of a wuss to tighten it too much. So i took it BACK to the shop and they tightened it down to "little more than 7Nm" and sure as sh*t it slipped about 2mm after 2 hour ride last night.

Can steel stretch over time ??

[Black Dog]

Thanks for chiming in here OP. Unfortunately, the post I have is already knurled (that a word?) so that aint an option.

Background: I over-tightened seatpost bolt and broke it off in the seatpost cluster and had to have it backed out. :mad::mad::mad:

My shop lubbed it up really well and put stainless steel screw in there and now I'm too much of a wuss to tighten it too much. So i took it BACK to the shop and they tightened it down to "little more than 7Nm" and sure as sh*t it slipped about 2mm after 2 hour ride last night.

Can steel stretch over time ??

Yes. Steel is ductile. Try some carbon paste or drink a beer from a can and make a shim. Pop cans (Soda/Cola for my American Cousins) work well too.

[oldpotatoe]

Thanks for chiming in here OP. Unfortunately, the post I have is already knurled (that a word?) so that aint an option.

Background: I over-tightened seatpost bolt and broke it off in the seatpost cluster and had to have it backed out. :mad::mad::mad:

My shop lubbed it up really well and put stainless steel screw in there and now I'm too much of a wuss to tighten it too much. So i took it BACK to the shop and they tightened it down to "little more than 7Nm" and sure as sh*t it slipped about 2mm after 2 hour ride last night.

Can steel stretch over time ??

Yes it can and the SP may be undersized to boot...if it still slips after being knurled.

[azrider]

Yes it can and the SP may be undersized to boot...if it still slips after being knurled.

Well the post came knurled from factory so it wasn't done by shop.

I think next steps are to wipe down and clean off grease, put some grit paste in there, and buy a torque wrench

if that doesn't work i spose i could try the beer can shim :(

[oldpotatoe]

Well the post came knurled from factory so it wasn't done by shop.

I think next steps are to wipe down and clean off grease, put some grit paste in there, and buy a torque wrench

if that doesn't work i spose i could try the beer can shim :(

Is it knurled or just couple of lines showing limit line? Being ‘knurled’ by shop is pretty aggressive and much deeper.

[azrider]

Is it knurled or just couple of lines showing limit line? Being ‘knurled’ by shop is pretty aggressive and much deeper.



Guessing mine is more......ribbed than knurled :p:p

https://uploads.tapatalk-cdn.com/20171013/c99a9656e52b122c6ce0ac8b40eded1f.jpg


Sent from my iPhone using Tapatalk

[oldpotatoe]

Guessing mine is more......ribbed than knurled :p:p

https://uploads.tapatalk-cdn.com/20171013/c99a9656e52b122c6ce0ac8b40eded1f.jpg


Sent from my iPhone using Tapatalk

Whomever ribbed it, may have made it smaller as well...I think a smooth SP, then knurled, would fix you up.

[cmbicycles]

Guessing mine is more......ribbed than knurled :p:p

https://uploads.tapatalk-cdn.com/20171013/c99a9656e52b122c6ce0ac8b40eded1f.jpg


Sent from my iPhone using Tapatalk
Those probably are machining marks from when the post was made. Knurling marks would usually be perpendicular to those marks, depending on the knurling tool. What is the seat post you are using?

[moobikes]

That looks like a Thomson post. They are sometimes a little undersized. Also, they have very little material in the column and will be crushed slightly when you crank the seatclamp down, going nowhere with the slipping problem.

At this point you should get a new post or try a different seatpost. Measure the diameter with a pair of verniers if you can and try to get a post fatter than the current one. A small difference in diameter should be all you need.

[moobikes]

And Thomson posts can crack along those tiny machining marks so I would advise not knurling it. Those cracks are really hard to spot.

[David Kirk]

Two quick things -

First is that your post is toast. You need to replace it with a new post that is not a thomson.

Second - can you post a photo taken from the rear showing the binder area and the slot?

dave

[azrider]

Wow thanks for chiming in fellas. So it's not a Thomson. Some cheapo a buddy had in his parts bin. Not sure if that's any consolation unfortunately

Here are pics David. See anything odd?

https://uploads.tapatalk-cdn.com/20171013/eba71fc01969e81b9551dd25b5bc6657.jpg

https://uploads.tapatalk-cdn.com/20171013/fd1305f442693e4885dec85a9ce5b179.jpg


Sent from my iPhone using Tapatalk

[David Kirk]

The binder looks good.

Do you have any calipers to measure the diameter of that post?

dave

[azrider]

The binder looks good.

Do you have any calipers to measure the diameter of that post?

dave

Negative.

If you don't mind sharing your expertise, what Nm would you be tightening this to?

[FlashUNC]

What're the chances thats a cheapo 27.0 post in a 27.2 hole?

[David Kirk]

Negative.

If you don't mind sharing your expertise, what Nm would you be tightening this to?

The torque value matters little if the post is too small....which is my guess.

I'd find a friend with some calipers and see what size that post actually is.


dave

[David Kirk]

Here's what I'd do -

With the post in place in the frame put a sharpie mark at the top of the seat lug point. Now remove the post and measure the O.D. of the post just below the head up top and make a note of it. Next measure the O.D. about 1" below the sharpie mark and make a note of that.

Both should be in the 27.15 - 27.17 range for a proper fit. If it's right up top but small in the clamped area the post is all done. It's been compressed. The post looks like it's a LaPrade which were made out of butter and necking down was common.

Without those numbers you are shooting in the dark.

The grooves that were made in this post no doubt didn't help. You may have made the effective OD very slightly larger but you also cut the surface area where the frame and post meet by a large percentage. For this reason alone, even if the post is the right size, I'd toss it and put a new post in place.....and I'd measure it before installing it.


dave

[cmbicycles]

Since you don't have a way to measure at the moment... that would be the best way to figure out what is going on with this seatpost. Are you sure this one is 27.2 (at least what it says on the post)? Have you tried using carbon/assembly paste with this seat post? Can you swap a seat post from another bike to see if it does the same thing?

[azrider]

So prior to last couple of posts/suggestions I went with removing excess grease, added carbon paste and after 2hr ride no movement.

I'm certain seatpost is 27.2. But now I'm thinking I should be in market for replacement....

Also interesting to hear regards towards Thomson, always thought durability was their biggest draw.

Thanks again for Info DK and others

[zmudshark]

Doug, head over to Harbor Frieght and get their digital calipers.

[David Kirk]

So prior to last couple of posts/suggestions I went with removing excess grease, added carbon paste and after 2hr ride no movement.

I'm certain seatpost is 27.2. But now I'm thinking I should be in market for replacement....

Also interesting to hear regards towards Thomson, always thought durability was their biggest draw.

Thanks again for Info DK and others


Cool - FWIW.....what a post is stamped and what it is are rarely the same. gt your hands on some calipers and you'll know the actual size.

dave

[Doug Fattic]

Azrider, another frame builder chiming in, how long is the binder slot? I couldn't tell from your picture. If it is not longer than more than an inch it can be too short and won't hold your seatpost.

[Climb01742]

Hey Climb.....what ever ended up happening with your slippage issue?

I'm obviously bumping because I'm having same issue with my CSI.

:crap::crap::crap:

I believe I found a post that didn't slip. Which highlights how much variance there is in seatposts and seattubes. I'm now dealing with a seattube that's too tight. Aaaargh!! I find that Fizik carbon posts have an annoying habit of being larger than 31.6 or 27.2.

[azrider]

Another 2hr ride an no slip!!

https://uploads.tapatalk-cdn.com/20171015/ad3c6508b7397e2431b5da0e3efe14cb.jpg


Sent from my iPhone using Tapatalk

[azrider]

Azrider, another frame builder chiming in, how long is the binder slot? I couldn't tell from your picture. If it is not longer than more than an inch it can be too short and won't hold your seatpost.



Hey Doug. Funny that's my name in real world.....No binder slot to speak of......its steel lug on my CSI

Or am I not understanding your question?

https://uploads.tapatalk-cdn.com/20171015/92940b8e116a1dd2e4796dcf1da8d55e.jpg


Sent from my iPhone using Tapatalk

[Doug Fattic]

Hey Doug. Funny that's my name in real world.....No binder slot to speak of......its steel lug on my CSI

Or am I not understanding your question?

https://uploads.tapatalk-cdn.com/20171015/92940b8e116a1dd2e4796dcf1da8d55e.jpg

Sorry I didn't make my question clear enough. I wanted to know how long the slot is on the seat lug. I was referring to the slot between binder on the seat lug. In my experience if it is only 1" or less it may not be able to grip the seat post properly. Let me explain with an example.

Many years ago when I made one of my own frames I used an investment cast seat lug. For some reason I thought a short slot would look good so I only made it 1" long. I was careful to ream the hone the seat tube so it exactly fit my chosen seatpost. It had a tendency to slip under some circumstances. I asked a framebuilding friend of mine and he said a seat lug binder slot should be at least 1 1/8th inch long (28mm). So I extended my slot just those few mm and my slipping problem totally stopped.

[Steve in SLO]

OP, I'm glad it sounds like your problem is solved.
I was half tempted earlier in the thread to tell you to place the seatpost at the proper height and drill a hole through your seattube/seatpost from the side and stick a bolt thru it and tighten. Call it a direct binder bolt. I have seen it done, but on a bike that was so rusty I don't think slippage could have occurred.

[azrider]

Doug, head over to Harbor Frieght and get their digital calipers.

Thanks Z. I'll do that. You back yet? Switch was flipped yesterday and temps are pretty amazing.....

OP, I'm glad it sounds like your problem is solved.
I was half tempted earlier in the thread to tell you to place the seatpost at the proper height and drill a hole through your seattube/seatpost from the side and stick a bolt thru it and tighten. Call it a direct binder bolt. I have seen it done, but on a bike that was so rusty I don't think slippage could have occurred.

So unfortunately while on a 'bumpy' ride yesterday, my seatpost has indeed decided to slip yet again :crap::crap::crap::crap::crap:

Instead of drilling into my CSI, do you think i could drill into the seatpost only a few millimeters above the lug and have the screw 'head' act as stoppage point......like Alessandro Ballan did to his seatpost for Roubaix circa 2007

[David Kirk]

I wouldn't do anything until you know the actual measured size of that post.

dave

[azrider]

I wouldn't do anything until you know the actual measured size of that post.

dave

Yay homework!

Thanks DK. That's a much more rational approach.




(deep breaths....deep breaths)

[Doug Fattic]

Doug, I am repeating myself but there is one thing I think you should try that will not hurt your frame and may solve the problem and that is to lengthen the slot on the back of the seat lug. It looks like they used a Henry James investment cast seat lug. They are cast with a built in slot. I just measured the slot length on a HJ lug in my inventory and it is just a bit short of 1". The slot length should be extended with a round file until it is at least 1 1/8" or more long. This is measured from the top of the lug to the bottom of the slot. My guess is that after the frame was brazed (so the seat tube now has to be slit to match the slot in the lug) the worker did not extend the slot any lower than the slot already in the lug.

Extending the slot will not hurt your frame in any way and is a lot more logical and easy to do than about any other more extreme remedy being suggested. I'll remind you again that I've found too short of a seat lug slot to be the source of seatpost slipping problems including the case on my personal frame that I mentioned before.

[azrider]

Here's what I'd do -



With the post in place in the frame put a sharpie mark at the top of the seat lug point. Now remove the post and measure the O.D. of the post just below the head up top and make a note of it. Next measure the O.D. about 1" below the sharpie mark and make a note of that.



Both should be in the 27.15 - 27.17 range for a proper fit. If it's right up top but small in the clamped area the post is all done. It's been compressed. The post looks like it's a LaPrade which were made out of butter and necking down was common.



Without those numbers you are shooting in the dark.



The grooves that were made in this post no doubt didn't help. You may have made the effective OD very slightly larger but you also cut the surface area where the frame and post meet by a large percentage. For this reason alone, even if the post is the right size, I'd toss it and put a new post in place.....and I'd measure it before installing it.





dave



OD at top of sea lug

https://uploads.tapatalk-cdn.com/20171030/7cde2b3e6e2d4bf90126432a19394c98.jpg

And 1” below that

https://uploads.tapatalk-cdn.com/20171030/8929436422f21bfa9794b1f3041dc610.jpg


Sent from my iPhone using Tapatalk

[FlashUNC]

So its either a big 27.0 post or an undersized 27.2 post.

[azrider]

So its either a big 27.0 post or an undersized 27.2 post.

:mad::crap:

Any seatpost's or oem's you metallurgists would recommend?

Should I avoid used?

[David Kirk]

very good. Now we are getting somewhere.

A post labeled "27.2" is meant to fit into a seat tube that is 27.2 I.D. and it is not supposed to actually measure 27.2.....it is a nominal measurement. A 27.2 post will not fit into a 27.2 hole and it needs to be just a bit smaller.

The actual diameter of a 27.2 post should be 27.15 so it looks like your post is right on.

This is of course good to know but it doesn't answer the problem of your properly sized post moving in your frame and this leads me to my follow up question - when you slip the post in does it take some work to get it in? Do you need to push and twist a bit to get it in or does it just slip or fall in?

dave

[Peter P.]

Doug, I am repeating myself but there is one thing I think you should try that will not hurt your frame and may solve the problem and that is to lengthen the slot on the back of the seat lug...

I agree with Doug.

I had a Salsa Ala Carte ATB frame with a slipping 27.2 seatpost. It had what I considered a short slot in the seat lug, as compared to my 2 other bikes. I extended the slot by drilling a strain relief hole 5-10mm below the existing slot, then using a doubled up hacksaw blade to cut the existing slot to reach my drilled hole. Worked like a charm.

[azrider]

Extending the slot.

Hey DFattic. Sorry for not responding earlier, and I appreciate what you had recommended, but once I read the part about taking a file to the frame I got a little too nervous. I have since measured the slot and it's rougly 1.10"

soooo......................

[azrider]

very good. Now we are getting somewhere.

A post labeled "27.2" is meant to fit into a seat tube that is 27.2 I.D. and it is not supposed to actually measure 27.2.....it is a nominal measurement. A 27.2 post will not fit into a 27.2 hole and it needs to be just a bit smaller.

The actual diameter of a 27.2 post should be 27.15 so it looks like your post is right on.

This is of course good to know but it doesn't answer the problem of your properly sized post moving in your frame and this leads me to my follow up question - when you slip the post in does it take some work to get it in? Do you need to push and twist a bit to get it in or does it just slip or fall in?

dave

Oh I definitely have to work it side to side to get it to fit.

[Black Dog]

Oh I definitely have to work it side to side to get it to fit.

How far in does the post slip in before it meets some resistance? You need to get your calipers on the ID of the seat tube.

[David Kirk]

Oh I definitely have to work it side to side to get it to fit.

Cool - so it sounds like the seat post is the right size and that the fit to the seat tube is certainly in the ballpark. I don't suspect the length of the slot being the issue as Serotta built many thousands of those bikes and slipping posts are not in any way common.

So in my mind it boils down to two possibilities -

- I would check that the M6 bolt has clean threads and that it's straight. Remove the bolt and wipe it clean to be sure that the threads look good and the same from right under the head to the end. If it is any way suspect put a new one in. Also give it a spin to be sure that it's straight. Many of the original quality bolts were lost and replaced with bolts that have the hardness of butter and these bolts will bend when fully tightened. If it's bent it will not clamp as it should. After typing all of this I think the best plan would be to go to your local Ace Hardware and spend 75 cents on a new M6 stainless bolt. It can't hurt. Grease the threads and the underside of the head well and try it.

- the other possibility is is that you are simply not tightening it enough. We never spec'd a torque value back in the day and I have no idea just how to tell you just how tight it should be. That said i would try it a bit tighter and see what you get.


dave

[Fatty]

If the post has grease at this point pull it out, throw some sand on the greased post and reinsert. Bet a dollar to a donut it won't slip.

[cmbicycles]

If you pull the bolt all the way out, do the bolt's threads run the full length of the bolt or do they stop short of the bolt head? Is the bolt itself, and under the head greased?

[Doug Fattic]

Hey DFattic. Sorry for not responding earlier, and I appreciate what you had recommended, but once I read the part about taking a file to the frame I got a little too nervous. I have since measured the slot and it's rougly 1.10"

soooo......................Well you are right on the edge of having the slot too short. In my 40+ years of building and painting frames, I've repaired a number of classic European frames made poorly but loved by their owners. Some of them had sloopily done seat lug slots that often resulted in damage to the seat lug ears (trying to tighten the lug enough to hold a slipping post) and perhaps the seat tube cracking below the slot. Sometimes this problem was related to the use of cheap stamped lugs that did not have enough material for a long enough slot. Just last week I brazed a short section of tube below the slot on a quickly made (but sentimental to the owner) bike boom era frame. By extending the slot and reaming and honing to the right size, a seatpost will now hold in the frame with less bolt tightening force. These experiences are what has led me to check slot length if there is some slipping problem. On my personal frame I only extended the length of my slot 1/8 of an inch and it made all the difference in the world. No matter how hard I tightened my seat lug when it was an inch long, it would still slip. After the surgery it held solid with much less force. This knowledge is why I kept insisting on checking your slot length. Of course there are all sorts of variables that contribute to what is the necessary slot length.

The file you would want to use is an American Pattern 4" round file with either a bastard or 2nd cut. They probably don't have it at your local hardware store. A
6" round file is pretty commonly available and you can use just the tip of it to extend the slot. Of course you can take it to your local frame builder too if this kind of work makes you nervous.

[T-Crush]

My CSi had the same issue. Gradual slip over a 100 mile ride. I tried three different posts, all measured between 27.14 and 27.16 at the relevant points (using Helios dial calipers - I put myself through college and grad school as a machinist). I tried paste, grit and even rock climber's chalk. Some helped, but none solved the issue. This solved the problem once and for all.

http://landlordscycling.com/2012/01/american-classic-framesaver-quill-seatpost/

Between the clamp and the quill, both tightened to spec, it's been rock solid for years.

[Peter P.]

Interesting thing I found while on the forum, reading another thread.

Doug Fattic and Dave Kirk have already suggested the length of the seat tube slot can be too short, inhibiting clamping force.

Well, Tom Ritchey mentions (https://www.youtube.com/watch?v=Zhu3tsZTzmU&feature=youtu.be&t=7m50s) in a display of the Road Logic frame that the seat tube slot is longer, to deal with carbon seatposts.

Can anyone measure the slot on their recent vintage Road Logic and tell us what the length is?

[azrider]

My CSi had the same issue. Gradual slip over a 100 mile ride. I tried three different posts, all measured between 27.14 and 27.16 at the relevant points (using Helios dial calipers - I put myself through college and grad school as a machinist). I tried paste, grit and even rock climber's chalk. Some helped, but none solved the issue. This solved the problem once and for all.

http://landlordscycling.com/2012/01/american-classic-framesaver-quill-seatpost/

Between the clamp and the quill, both tightened to spec, it's been rock solid for years.

THat thing is genius.....how the heck do you order one?

[Kontact]

THat thing is genius.....how the heck do you order one?

A time machine. You'll have to find a used one.

[Kontact]

A 1 1/8" slot minimum is an observation from another frame. But the OP bike has a fastback seat cluster, which locates the bolt lower from the top than a more classic cluster:

http://farm5.static.flickr.com/4063/4217687432_76ec40e773_o.jpg

So 1 1/8" might not be sufficient given that the bolt is 1/4" lower on the OP bike.

I'd lower the slot.

[bikingshearer]

I had the same problem with a cheap steel commuter frame a Pake C'Mute.

I use carbon paste on an aluminum post and now it does not slip without having to result in excessive torque on the binder bolt.

I had the same problem with my old (1967) Schwinn Paramount frame (now the baddest ass commuter ever). Carbon paste plus a very small soda can shim did the trick for me. I tried the shim first, and added the paste when the shim alone didn't quiiiiiite get it done.

With the benefit of hindsight, I'd say try the paste first. If that doesn't work, add the shim (and you'll be surprised by how narrow the shim will be, but using snips on a soda can is easy-peasy-lemon-squeasy). If that doesn't work, do Old Spud's knurling thing. If that doesn't work, get a different bike.

[Kontact]

I had the same problem with my old (1967) Schwinn Paramount frame (now the baddest ass commuter ever). Carbon paste plus a very small soda can shim did the trick for me. I tried the shim first, and added the paste when the shim alone didn't quiiiiiite get it done.

With the benefit of hindsight, I'd say try the paste first. If that doesn't work, add the shim (and you'll be surprised by how narrow the shim will be, but using snips on a soda can is easy-peasy-lemon-squeasy). If that doesn't work, do Old Spud's knurling thing. If that doesn't work, get a different bike.

I can't speak for 1967, but many later Paramounts used 27.4 seat posts.

[bikingshearer]

I can't speak for 1967, but many later Paramounts used 27.4 seat posts.

Good thought, and I tried a 27.4 - no chance. I even found and tried a 27.3 - again, no chance, at least not without an unacceptable amount of grinding. So I was left with paste-plus-shim. Not exactly the most elegant solution, but it's working.

I think 27.4's didn't come in for at least another 10 years, maybe more, but I'm not certain. I do know that any Paramount I have seen and could check from the late 60s to mid 70s had a 27.2 post.