[DeeEight]

the solution is to change to the actual seatpost size the seattube was sized for, which is 27.0... NOT the 26.8 size post they spec'ed with the bikes. I tried a variety of 26.8 posts figuring maybe just the stock supplied post was manufactured slightly too small but even precision made posts like Thomson would slip with the seatpost clamp seriously over-tightened. This weekend I switched to a 27.0 post... no more slippage.

 

[nato_the_greato]

Nice! I wonder why I never figured that out.
I ended up using fiber prep instead of grease and it held alright.

 

[EJ]

Interesting.
I ended up buying a Surly Constrictor seat clamp, which at $15 is still cheaper than a new post. It's holding tight.

If my seatpost is the wrong size, does that make it defective??

 

[chumbox]

I just tighten the seatpost with an allen key instead of the quick release and sprayed the tube with hairspray, no problems ever since. I'd be suprised if they spec'd it wrong for so long, 27.0 may just work for you.

 

[Oldnslow]

I measured the seattube clamp area as 29.8mm, but it was spec'd with a 30mm clamp. Replaced with Woodman Deathgrip 29.8mm seatpost clamp, no more problems. I think it was $10 or so from universalcycles

 

[DeeEight]

I measured the seattube ID as 27.0 myself... I'm sure the combination of the wrong clamp and wrong post explains why you basically need to resort to monster effort clamps distorting the seattube, or effectively bonding the tubes together to keep them in place.

As to continuiing to spec the wrong parts for so long.... this is a bicycle company we're talking about, not Boeing. They spec the parts they do because of what prices they got when ordering them. If using a slightly smaller post saved them thousands of dollars over the model run of the bike, they'd do it. On one GT road bike I setup at the store last year, I pulled this ridiculously short FSA out of the frame... like 200mm length post. It belonged basically on a TT bike or something where you didn't need much extension. Instead they put it in a series 3 road bike, size 56cm as I recall. Why? The usual reason is they got a lot of them cheap, so since they needed a 31.6 diameter, they didn't much care what length they used.

We often have to cut down the seatposts on the smaller MTB frame sizes because they ordered nothing but 400mm length seatposts for the model. But with the smaller size frames, you can't lower the seatpost far enough to fit all the riders the frame is designed for without smacking into the bottlecage bolts.

 

[dog.gone]

GT Peace 9r Multi Seatpost Slip

Count me as another GT Peace 9r Multi owner who loves his bike but hates the seatpost slippage.

I have my QR scary tight and still experience slippage. Unfortunately, I don't have calipers to effectively measure the ID and OD of the seatpost tube, so I'll have to try a couple of post/clamp combos to see how things work... or try the old Coke can shim method. :skep:

Thanks to GT_guy for pointing me to this thread! :thumbsup:

 

[dog.gone]

Because I'm a clyde (and have already bent my [email protected]#% seatpost), I've been looking at getting a Thomson seatpost - and I need a setback post. After looking at the Thomson website, the don't even appear to manufacture a setback post in 27mm/410mm flavor. Damn.

http://www.lhthomson.com/elite_sizes.asp

I'm willing to bet the 27.2mm post will be too big, huh?

 

[dog.gone]

Sorry to beat a dead horse, but...

I'm wondering whether anyone has successfully tried a 27.2mm seatpost? I don't have the proper tools to accurately measure the inner or outer diameter of my seat tube, nor do I have ready access to various sizes seatpost sizes to test.

Alternatively, since Thomson doesn't seem to have a 27.0mm setback seatpost, is there another manufacturer that produces a heavy-duty, clyde-worthy setback seatpost in 27.2mm?

Thanks!

EDIT:
After searching the clyde section, here are a few posts that have been suggested as alternatives to the Thomson:

• Titec El Norte
• Truvativ Team
• Easton Vice
• Easton Havoc

Anyone here have experience with any of these posts? Off to check which posts have a setback in 27mm flavor...

 

[Oldnslow]

I couldn't get a 27.2 to work. Got the Woodman 29.8mm clamp from www.universalcycles.com. and no problems since then. Way cheaper than a new post, solved the problem.

 

[dog.gone]

I couldn't get a 27.2 to work. Got the Woodman 29.8mm clamp from www.universalcycles.com. and no problems since then. Way cheaper than a new post, solved the problem.

Thanks Oldnslow. I use Universal Cycles extensively since they are in my hometown. They're a good group of enthusiasts who have been very helpful with every question and every transaction.

That being said, I finally got frustrated enough on my ride today that I stopped by the new LBS just a mile or so from my place. Phillip of Cayuse Cycles *really* helped me out.

Not only did he stop what he was doing to address my problem, he took the extra time to break out his digital calipers, measure the seat tube ID and OD *and* let me borrow a new Interloc clamp until the Thomson clamp is finally in stock. The new/borrowed clamp made all the difference.

 

[dog.gone]

Thanks Oldnslow. I use Universal Cycles extensively since they are in my hometown. They're a good group of enthusiasts who have been very helpful with every question and every transaction.

That being said, I finally got frustrated enough on my ride today that I stopped by the new LBS just a mile or so from my place. Phillip of Cayuse Cycles *really* helped me out.

Not only did he stop what he was doing to address my problem, he took the extra time to break out his digital calipers, measure the seat tube ID and OD *and* let me borrow a new Interloc clamp until the Thomson clamp is finally in stock. The new/borrowed clamp made all the difference.

I just wanted to follow-up on my solution:

• Race Face Diabolus DH post 26.8mm/350mm/.75" setback
  
• Woodman Death Grip 28.6mm seat clamp

The post has just enough length that I don't have to worry about the minimum insertion point and the Death Grip locks the post in place nicely. The extra setback was a nice bonus and has helped fine-tune my cockpit position.

 

[utarch00]

Are you guys using Quick Release clamps or bolted clamps?

 

[dog.gone]

The Woodman Death Grip is a bolted clamp. Since upgrading the seatpost and seat clamp, I've had no further problems with slippage.

 

[utarch00]

OK. Thanks. According to your link, they do make a Quick Release version. Is the clamp fix more of a going to a bolt clamp or just getting a better fit clamp.

 

[dog.gone]

Yes, Woodman does make a QR version of the Death Grip. I went with the bolt on because I've never released it when doing any downhill actions and only needed a QR when trying to prevent someone from stealing my seat.

My LBS (Cayuse Cycles in West Linn, OR), measured the OD of the seatpost, as well as the ID and OD of the seat tube. In my particular case, it appeared that the seat tube was correct, but the seatpost was ever so slightly too small. The Race Face Diabolus, along with the Death Grip and a tiny bit of carbon paste have create a rock-solid fit for my 290# butt.

I hope that kinda answers your question. If not, just let me know.

 

[fos'l]

GT Slipper

Measured seat tube diam. at 27.0, and changed the post accordingly with an Easton from CBO. Cost $15.00 (20% off until 5/31).

 

[hoogie]

I just wanted to follow-up on my solution:

• Race Face Diabolus DH post 26.8mm/350mm/.75" setback
  
• Woodman Death Grip 28.6mm seat clamp

The post has just enough length that I don't have to worry about the minimum insertion point and the Death Grip locks the post in place nicely. The extra setback was a nice bonus and has helped fine-tune my cockpit position.

how on earth did you manage to get the 28.6mm seatclamp to fit? i bought one and all i suceeded in doing with it was to peel off some paint around the seat tube lip area :sad:

trying to find a 29.8mm seatpost clamp and a reasonable quality 27.0mm seatpost locally is proving to be a tad difficult, so will most likely have to bite the bullet and mail order one from the usa ... postage rates are so high even for ordering little bits!

would a 30.0mm work as well, just tightened a little bit more?

on the plus side, have managed to slow the slippage for now with a piece cut from a soda can, even though i broke the lever on the orignal seatpost binder ... have a bolt holding it tight at present, not pretty but works enough for a temporary fix ...

on the plus side, spent an awesome afternoon riding through the forest trails on sunday ... have a peace 9r multi set up as a 1x9 :thumbsup:

 

[dog.gone]

29.8mm Woodman Death Grip for the Peace 9r

how on earth did you manage to get the 28.6mm seatclamp to fit? i bought one and all i suceeded in doing with it was to peel off some paint around the seat tube lip area :sad:

Hoogie,

Funny you should ask that.

I spent much of the last week trying desperately to find a mysterious creak that I had been certain was my bottom bracket. Well, after replacing the bottom bracket, what do you know... the creak was still there.

So, in the process of tightening everything, I went ahead and tightened the bolts holding my seat and attempted to tighten the seat collar as well. Half a turn later, I stripped the whole thing. This time I ordered a 29.8mm Death Grip. Creak gone. Damn. :skep:

So, I apologize if my earlier solution mislead you. My LBS installed the 28.6mm seat collar by using spreaders. It worked fine for about a month with absolutely zero slippage of the seat post. Based on my recent experience, I think the 29.8mm collar is the right solution. :madman:

 

[hoogie]

Hoogie,

Funny you should ask that.

I spent much of the last week trying desperately to find a mysterious creak that I had been certain was my bottom bracket. Well, after replacing the bottom bracket, what do you know... the creak was still there.

So, in the process of tightening everything, I went ahead and tightened the bolts holding my seat and attempted to tighten the seat collar as well. Half a turn later, I stripped the whole thing. This time I ordered a 29.8mm Death Grip. Creak gone. Damn. :skep:

So, I apologize if my earlier solution mislead you. My LBS installed the 28.6mm seat collar by using spreaders. It worked fine for about a month with absolutely zero slippage of the seat post. Based on my recent experience, I think the 29.8mm collar is the right solution. :madman:

gotcha ... that all makes sense now!

i tried to prize apart the 28.6mm clamp al little with a flat bladed screwdriver and i think all i achieved is nicking my palm [and scratching the seat tube] ...

had a quick squizzo at universal cycles ... their minimum shipping charge is USD$28 for international postage, even for a single solitary woodman death grip ... will try and see what i can get here before i resort to super-expensive measures! although, i could use it as an excuse to order more bits to make the postage worthwhile???

might also try a few other mail order stores to see if the rates are better ...

thanks for your help!

hoogie