Carbon seatpost cracked straight off at 5 Nm

Manc33

"I better not go to 6 Nm with this" I thought. Thats about the absolute limit. "Best only do it to 5 Nm" I thought. Didn't even hear it crack when it went. I guess it started cracking around 3 Nm to 4 Nm. The crack is about 3 inches and goes right through to the inside.

I might just use it as it is, if it falls off it falls off. Don't care anymore.

diy

post a pic - might be a fake, so many around.

Manc33

diy wrote:

post a pic - might be a fake, so many around.

I already knew it was before I got it (why pay £60 if you can pay £25) but so is all my other carbon stuff and its all been fine. I knew it looked too thin as soon as I got it, but cracking before or at 5 Nm is a bit ridiculous. Can't even flog the clamp because its a fake.

The only reason I got another post was because my Ragley one has that silly clamp where it slips no matter how tight it is. I just tightened each one of those up to 12 Nm each and it isn't slipping now, but I only went out for 5 miles. Thats on carbon rails - yes, a cheap fake saddle. Who knows what carbon rails can take, way over 6 Nm because mine are at double that.

So the cheapo "Toupe" and cheapo "SMP" both aren't cracking! The SMP has 12 Nm per rail and is fine.

All I want is a seatpost with these four key features:

- 31.6mm
- 25mm setback (ones with any less are gonna definitely be no use)
- It absolutely must have a bolt front and back (not side to side bolts, or side clamps, or "one bolt")
- It has to be metal :roll:

Well that's put me off carbon fiber handlebars pretty much for life. I don't care if they are fake or real.

It isn't just fake ones that crack, £90 Eason ones have cracked, a guy even cracked his Thomson Elite and that's metal... is it more likely to break if its a knock off? Probably. Is it a certainty? No way.

Plus - how many manufacturers get all their carbon bike parts made in China, put a sticker on and triple the price?

I don't jump to blame it so quick just because it is a fake. :P

Torque wrench used was a genuine one. The £42 Cyclo one (set exactly between 4 Nm and 6 Nm)

Honestly its no wonder people constantly talk about carbon paste all the time, just put a metal seatpost in. Or make the things with thicker tubing around the parts likely to get clamped. After all my carbon frame has a metal tube in the seat tube for this reason. They could just as easily put a metal tube in the carbon seatpost, so what if it adds 50g.

I only got a carbon one because on AliExpress they don't even sell anything BUT carbon ones. Plus it was about the cost of a cheap metal one (£25).

Pics of it anyway:









The crack extends about half an inch beyond the visible crack in the pic. That is more of a "crumple".

I might just put it back on again as it is my water bottle bolts will stop it slipping all the way down... just kidding. If it would hold the thing in place I would be putting it back on.

Next time I will have to remember to wedge a metal tube inside the seatpost, that would work, had I known it would crack at 5 Nm that is. You live and learn.

Anonymous

Manc33 wrote:

why pay £60 if you can pay £25

So it does not crack and waste the £25 perhaps

eddiefiola

The real ones crack too, my FSA K Force carbon is back with them now to see if they'll replace it or deem it user error...

Manc33

Carbonator wrote:

Manc33 wrote:

why pay £60 if you can pay £25

So it does not crack and waste the £25 perhaps

Genuine ones crack. Thats because they are made from carbon fiber.

So I lost £25 instead of £60. (See post above this one).

FSA however could possibly honor the warranty (if it was a genuine), but on something like this, I don't think so. All they would say, well all they do have to say, is "You must have torqued it too much". You can't prove anything unless you can prove your torque wrench is correct, which isn't possible without a certificate.

Sending a £25 seatpost back to China would cost me £25 so that's out.

I still think if I could wedge a metal tube inside this it would work, but it would have to be wedged tight.

letap73

You got a cheap carbon fake and it failed.

Don't fu@k about it with it for a botch job, if it fails, you may risk serious injury. Put it down to experience and buy a good quality seat post.

nicklouse

Bet the clamp was the wrong way around.

dilatory

Is 5nm not a bit too tight? My carbon seatposts say 3nm max. Max meaning you don't need to be at 3nm.

Manc33

nicklouse wrote:

Bet the clamp was the wrong way around.

That would be funny were it not for the fact that the clamp being on wrong wouldn't cause what happened to happen. Besides, it says "Front" on the clamp with an arrow, you could only have it the wrong way if you were blindfolded or had the IQ of an orangutan.

dilatory wrote:

Is 5nm not a bit too tight? My carbon seatposts say 3nm max. Max meaning you don't need to be at 3nm.

3 Nm wouldn't even hold your weight, they slip as it is at 5 Nm.

Does anyone know if anything like this is available but in metal? It has to have that bolt system (the whole reason for buying this post). Has to be setback. This post being carbon was at the end of the list of reasons why I bought it. I wanted a metal one from the off.

EDIT: Just put "seatpost -carbon -clamp" in the search on AliExpress and got nearly 16,000 results. :oops: Maybe I should have done that last time. At least it will be super cheap lol. If their carbon ones are £25 their metal ones have to be about £8 or £10 posted.

EDIT 2: Oh, I just added "31.6" to the search and now get "293 Results" :evil:

dilatory

At not even 3nm they hold me perfectly fine...

Manc33

Dude are you 90lb? :P

Show me any pic of any carbon seatpost that says 3 Nm on it and I will believe it. Hell I'll even believe an 8 is a 3 if its rubbed off.

Might not be back to reply because I'm looking for a metal seatpost... no setback, one bolt, no setback, no setback, one bolt, carbon, too thin, one bolt, no setback... no one makes one in metal.

Manc33

This would be ideal were the postage not more than the item.

http://www.ebay.co.uk/itm/Aerus-AL-Elit ... 565f841a9e

I don't need to find a niche in a market, I just go looking for the bike components I need.

I want a 29.8mm to 31.6mm shim - they don't exist.
I want a 36.6mm quick release seatpost clamp - they don't exist.
I want a metal seatpost with 2 bolts thats 31.6mm with a 25mm offset, they don't exist.

All through my life I go to do something and I can't do that because this isn't done, so I go to do this and this cannot be done because something else needs to be done, so I go to do that and can't because something else needs to be done for that to be done.

What I am saying is if they just made a bloody shim none of this would be applicable, I would just buy the shim and put my old seatpost in I always had. Yes it is a 1-bolt but it doesn't matter because it has the notches on (aka non-infinite adjustment). Infinite adjustment ones with bolts going horizontally just slide back, the saddle didn't slide on the rails, the whole clamp arches back on the curved bit until the saddle nose is pointing up. Who designs these things honestly.

Decathlon had it right on their cheap bikes. Both the Rockrider and Triban have the same seatpost and I never had a problem with them. Always hated them because of those notches and wanted infinite adjustment all the time until I got one and realized they slip on certain saddles. No wonder since its 6061 aluminium. The bolts just eat into it. It might be nice and tight when you set off but you rocking side to side on it just presses the notches in and you'd have to tighten it back up to the same tension. Then you're screwed, the notches have flattened and it will slip no matter how tight it is or how lightweight you are. I mean slipping backwards not the seatpost tube.

Anonymous

Some BMC carbon seat posts are 3nm, but think they may be 2 bolt and/or not round ones.

Bobbinogs

Manc33 wrote:

...

I don't need to find a niche in a market, I just go looking for the bike components I need.

I want a 29.8mm to 31.6mm shim - they don't exist.
I want a 36.6mm quick release seatpost clamp - they don't exist.
I want a metal seatpost with 2 bolts thats 31.6mm with a 25mm offset, they don't exist.

...

To be fair, you may not be looking for a niche in the market but your list of requirements is pretty bespoke by any standard.

darkhairedlord

What you want to do is chuck all your fake carbon death trap ebay "I can't believe it's so cheap" tat in the nearest skip. Then take the bike to your LBS, hand them a wad of cash and get it sorted.
OR, just buy a deda aaluminium seat post of correct size and set back from ribble (about £15-20) and a new saddle to go with it. stop kidding yourself ebay can save you money, it won't.
With your demonstrable lack of competence behind a spanner you will just send yourself to casualty.

MountainMonster

Bobbinogs wrote:

Manc33 wrote:

...

I don't need to find a niche in a market, I just go looking for the bike components I need.

I want a 29.8mm to 31.6mm shim - they don't exist.
I want a 36.6mm quick release seatpost clamp - they don't exist.
I want a metal seatpost with 2 bolts thats 31.6mm with a 25mm offset, they don't exist.

...

To be fair, you may not be looking for a niche in the market but your list of requirements is pretty bespoke by any standard.

That is exactly what I was thinking. You can't expect companies to mass produce something that is going to be bought by you once. If it is that worrying that it is not available, then get it made bespoke, or learn to deal with existing designs.

Bar Shaker

Surely this thread is a wind up.

darkhairedlord

Have you thought of writing a blog?

imposter2.0

Bar Shaker wrote:

Surely this thread is a wind up.

Sadly, I think not...

ballysmate

Am I missing something?

Op knowingly buys a fake product. On examining said fake, he notes that it appears inferior. Attempts to fit said fake and it fails.

Lesson appears to be don't buy fake but buy the best genuine part you can afford.

iPete

Ballysmate wrote:

Am I missing something?

Op knowingly buys a fake product. On examining said fake, he notes that it appears inferior. Attempts to fit said fake and it fails.

Lesson appears to be don't buy fake but buy the best genuine part you can afford.

but the plot thickens, OP thinks all carbon is the same, surely his fake is exactly the same as the more expensive ones that the 'brands' just stick a sticker on, right?

veronese68

I'm going to make a radical suggestion here. Perhaps the OP should go into an actual bike shop and look at some seatposts then buy the one that fits his criteria. If they don't have what he wants in stock they could order one in then he can examine it before completing the purchase.
I realise this doesn't meet the criteria of being cheap shoot, but apart from that it could work.

ballysmate

Op stated "I knew it looked too thin as soon as I got it". He fitted it and guess what? He was right.

iron-clover

Why risk it with something like a seatpost? They can be put under a fair amount of strain from the clamping and then acting as a lever with your weight on it- imagine it shattering when you hit a pothole on a fast descent- that would be a big accident waiting to happen.

You completely wasted your £25 and now have to buy the real deal. Frankly I'd be embarressed enough without posting on a public forum- what did you honestly expect if you knowingly bought fake and even commeneted that it's way too thin?

Personally with your massive list of requirements I'd be inclined to throw the lot away (esp. if it's ALL dodgy stuff) and start again with reputable alloy bits- cheap, light ish and won't crack if you look at it the wrong way.

As a side point, I have an old Deda Drittissimo carbon seatpost (round) that is clamped at 9nm without any issues.

iPete

iron-clover wrote:

As a side point, I have an old Deda Drittissimo carbon seatpost (round) that is clamped at 9nm without any issues.

This! I have three, solid, reliable and certainly not the same as the OPs fake.

Colinthecop

iron-clover wrote:

You completely wasted your £25 and now have to buy the real deal. Frankly I'd be embarressed enough without posting on a public forum-

NO NO NO....!!!!

Forums need posts like this. 8)

defride

My 18 month old Fizik Cyrano cracked at the pinch point of the seat tube, I've a torque wrench so was confident it'd been tightened correctly. I didn't have the receipt so sent Fizik a message and pics, just to say I was disappointed. Had a message back within 24 hrs asking for my address so that they could send a new post, it arrived within a week.

I'd not have bought Fizik again but with that sort of back up I'd have no hesitation.

Fizik, good company imo and worth the premium price

mugensi

I see people saying they torque their seat posts to 3Nm, isnt that far too little? I have mine torqued to 6-7Nm and TBH i think that its not enough (although I have never tightened it any further) Once i tighten it with a torque wrenc, I loosen it again with an allen key and tighten it back up again to the same point to get an idea how tight it is and 6Nm isnt very tight IMO.

dodgy

That's good of Fizik to provide the support. But I'd still be worried about a post that cracked, all very well getting a replacement, but that's no help if you've been plonked from the bike on a descent.

I had a similar experience with X-Lite way back in 2001 (just checked my emails), seatpost #1 failed, I complained and they sent a replacement. Seatpost #2 also failed.

mr_evil

Manc33 wrote:

nicklouse wrote:

Bet the clamp was the wrong way around.

That would be funny were it not for the fact that the clamp being on wrong wouldn't cause what happened to happen...

When a seatpost clamp is tightened, the edges by the gap are pulled inwards. If they line up with the slot in the seat tube, all the clamping force will be concentrated along those two edges, potentially crushing the post.