trek seatpost break

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Cheap Suspension Seatposts - Worth it or Worse than nothing?

• Thread starter vita10gy
• Start date Jun 2, 2021

• Jun 2, 2021

Amazon.com : DJC Bike Suspension Seatpost Shock Absorber Damper Post 27.2 30.9 31.6 mm, Lightweight Aluminum Body : Sports & Outdoors

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Trek Pavement Suspension Seatpost - Trek Bikes

m@Robertson

The Satori Animaris is an excellent budget post. I got one when they were $49. Now they are like $85. But a solid product. I have seen cheapo piston-type suspension seatposts fail and I would categorize them as worse than nothing. @vita10gy the post you linked, in the reviews there are multiple reports of it screeching on every bump. Sounds like a spring rubbing against the interior? Not something I would live with.  

m@Robertson said: The Satori Animaris is an excellent budget post. I got one when they were $49. Now they are like $85. But a solid product. I have seen cheapo piston-type suspension seatposts fail and I would categorize them as worse than nothing. @vita10gy the post you linked, in the reviews there are multiple reports of it screeching on every bump. Sounds like a spring rubbing against the interior? Not something I would live with. Click to expand...

Follow up question, I saw to check my current seat post for sizing information. I expected a straight forward something but it says 308 350 20 11 It's a 2021 espin flow. Assuming the website is up to date and I got all parts as listed it's a 30.4MM Do I need that and only that, or would a 30.9 just be a little more snug and a tiny bit smaller just needs to be clamped tighter?  

vita10gy said: Follow up question, I saw to check my current seat post for sizing information. I expected a straight forward something but it says 300 350 20 11 It's a 2021 espin flow. Assuming the website is up to date and I got all parts as listed it's a 30.4MM I presume the 300/350 are lengths, but I don't see any obvious way to turn "20 11" into the common MM options offered. Do I need that and only that, or would a 30.9 just be a little more snug and a tiny bit smaller just needs to be clamped tighter? Click to expand...

Amazon.com : Cane Creek .ST25260 Seatpost Shim, 25.4 I.D. TO 26.0 O.D. : Bike Seat Posts And Parts : Sports & Outdoors

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What diameter seatpost does a 1994 Trek 970 take?

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What diameter seatpost does a 1994 Trek 970 take? There's a 27.2 seized in there right now, I'm going to dissolve it with lye next week, and I'm worried that it might be the wrong size: I've seen 26.8 and 27.2 listed for various mid-90s 970s. I got this at a police auction and am worried that someone pounded a 27.2 into a 26.8… I'll be grateful for a definitive answer.  

Doubt very much that it was pounded in. It just seized. And if a 27.2 was pounded into a 26.8 seat tube and by some miracle didn't break stuff, your seat tube is now 27.2 anyway. You could check BikePedia website. There's a Vintage, retro, classic forum on here maybe someone can help. BTW, ammonia will dissolve aluminum rust/oxidation. Be sure to grease the new post.  

Bikepedia lists the '94 components, but not the diameter. I'm hoping it's just seized, but you're probably right that in any case it's now a 27.2.  

Yup, they do list a 27.2 for 95' thou. If it's an aluminum post and a chromoly frame, which I think it is, you prolly have both rust and oxidation. Flip the bike over and take out a water bottle cage bolt and squirt some ammonia in there, let sit overnight. If that doesn't work, get some PB Blaster, or the likes, and do the same. A bench vise will surely help, leave the wheels on and twist the frame with the post secured. Aluminum (post) will expand 2x as fast, and 2x as much as the chromoly (frame), so some heat from a heat gun or hair drier directed onto the frame, but not too much for too long as not to effect the aluminum post, can surely help some too. Good luck.  

I'm assuming a decade or so of galvanic corrosion, and PB-Blaster did nothing. Heat is counterproductive, but if I had some liquid N2 I'd try that. Ammonia probably won't dissolve the Al oxide any further than the penetrant. So I'm going to bite the bullet and dissolve the f'er with some NaOH. My concern about the diameter is that between '94 and '95 they went from OX-II to OX-III tubing, and this wouldn't be the first bike I've encountered with the wrong seatpost pounded in. Love the bike though. Best $100 bike I've ever bought.  

Ammonia works like magic for aluminim oxidation, and you'll have to tell all the mechanics that have been succesfully using heat, including myself, that heat is counter productive. I once had a stuck seat post that just wouldn't come loose. I left it outside overnight with a wet towel wrapped around the post just for some cold. If it fit in the freezer I woulda done that. Applied some heat to the frame first thing in the morn. I actually herd the noise of when it broke free and then pulled it out with my hands. Don't see how you could pound an aluminum, bigger than seat tube post in, without some heat and/or breaking something. It's not like a sock that doesn't fit. If the post don't fit it just don't fit. It would take a retard to take a hammer to it, and a genius to make that work while still having a post and frame intact but whatever, not sayin' it can't be, or hasn't been done. Enjoy the ride and check out this link. 14 Ways to Unstick a Seatpost  

In high school and college I wrenched in the summer and saw all sorts of stupidity. Heat works for steel seatpost / steel frame, or Al / Al, but unless the timing is perfect, heat will further press the Al into the steel given the relative thermal expansion rates. I'm a little surprised it worked for you. Filling the seat tube with liquid nitrogen or crumbled dry ice might do the trick. But NaOH (Lye) in water + time works with certainty. Flush with vinegar and then a baking soda solution and then (as you suggested) liberally grease the new post.  

When you get the seatpost out, measure the ID of the tube with a micrometer. I've seen 26.8 on some early 90's 9xx series bikes but my '96 970 was 27.2 so I'm not sure what year they changed.  

I'm not sure a micrometer will work - as the Meat said, whatever the original dimension was, the top few inches of the seat tube may have been expanded to 27.2. I have a spare road 27.2, so after I dissolve the old one and clean the seat tube I'll see if it fits easily. The seat that came with the bike was the perfect height for me. I swapped it out for a WTB SST2K (very flat seat), and now it's 15 or so mm too low. The temptation to put that old seat back on…  

It should be a 27.2 mm. In my experience if a Coke soak doesn't break it lose, a propane or MAPP gas torch and a table vice on the post head takes it out. Heat the post. I haven't lost one yet.  

Tryed wiggling in a bench vice? Ive undone an Giant alu seatpost that way.  

Let us know how you make out.  

Will do. Though it will be a week or so until I have the replacement post.  

OK - so today's the day. I just cut through the seatpost about an inch above the frame. It's 22.5 cm long, about 4mm thick with an average diameter of 2.5 cm = 67.5 cc x 2.7 g/ cc = 182 grams, or just under 7 moles. 2Al + 2OH- + 6H2O --> 2[Al(OH)4]2- + 3H2 So 7 moles of NaOH = 280 g in at least 108ml water. I have 16oz of NaOH, so that should be sufficient. Time to cook. Update 1: Used a French Press beaker in an ice bath to dissolve the NaOH, but mixed the NaOH too thick. I fed it in through a water bottle bolt hole, and after a few minutes it bubbled out through both bottle holes due to the viscosity. When I added water it started to steam and boil, and I heard a few cracking noises. At this point I'll add 20cc of the more dilute mixture every 20 minutes or so - it bubbles out. At one point the seat tube was too hot to touch, and a BBQ lighter held up to the hole was shooting / popping out 5 inch flames.  

Hope it's not cooking your bb. Did you flip the bike, or did you cut off the post and can't?  

theMeat said: Hope it's not cooking your bb. Click to expand...

Update 2: I was hoping to get this done without stripping all the components off the frame, as I don't have my bike tools here, and they won't arrive for a couple of weeks. Specifically the splined BB cup tool. Unfortunately, during the night the viscous bubbly NaOH solution bubbled its way into the top tube, leaked through the head tube, and has corroded the top headset cup and brake hanger. With cartridge bearings, not a big deal. If the bubbly goo made its way to the BB there might be some minor issues. I was planning on rebuilding the bike in a few weeks, and was hoping to ride it in the interim, but that's looking unlikely.  

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