Seat post what am I doing wrong

[wjwren]

Just purchased from Decathlon and this seems the lowest it goes. I cant tell if the seat post is carbon or not. If it was steel id just cut it. Any ideas please.
[url]|https://thumbsnap.com/vchbERhY[/url

[WinstonWolf]

Get a thin rule, slide it down the inside of the seat tube and measure how far it goes before you hit an obstruction. You might need to work around the whole inner diameter to see if you find anything.

Torches are good for inspection too...

[dontlookdown]

Take those two cage screws in the seat tube out and try again.

[gazza285]

dontlookdown said:

Take those two cage screws in the seat tube out and try again.

The post will still hit the rivnut that the screw is threaded into, so don't bother.

[GOATever]

Take the bottle cage bolts, on the seat post out, and then get the riv nuts out as well, it’s actually not that hard to do. You just need a flat head screw driver to get the flanges away from the seat post, then grip them with a pair of pliers and wiggle them until they pop out. Or alternatively dremel the flanges away, and the nuts will drop into the seat post.

[The_Jackal]

Just looked at the advert and it is a carbon post.

[gazza285]

GOATever said:

Take the bottle cage bolts, on the seat post out, and then get the riv nuts out as well, it’s actually not that hard to do. You just need a flat head screw driver to get the flanges away from the seat post, then grip them with a pair of pliers and wiggle them until they pop out. Or alternatively dremel the flanges away, and the nuts will drop into the seat post.

You are advocating taking a brand new frame and either prising or grinding out the rivnuts, thus rendering the warranty invalid? What do you then suggest to do with the two 7mm holes now in the seat tube?

OP, have you contacted Decathlon? They might be willing to send you a shorter seat post. If not, then seat posts can be cut down, just ensure that you still have at least the minimum insertion depth, and that you clean up the cut end.

Do not take a screwdriver to the rivnuts.

Is the saddle too high? Perhaps a smaller frame would be better for you.

Edited by gazza285 on Thursday 27th February 16:55

[Willow1212]

I wouldn't go hacking away at stuff if you can avoid it.
If the post is fouling on the bottle cage mounts, or there is another obstruction in the frame stopping it from dropping, then I'd go back to the shop. If there's a manufacturing defect then that's their problem to resolve, and if not then I'd like to think they would trim the post for you to make the bike they sold you actually fit you.

[anonymous-user]

First, make sure you are setting your saddle at the right height. No point cutting anything if all that does is set the saddle too low.

Next, does that seatpost come in shorter lengths? If it does, go back to Decathlon and ask them to swap it for a shorter one.

If it doesn’t, either cut it or buy a shorter one.

If you’re going to cut it, check the seatpost for a min insertion mark. This will show you how much post you have to have in the frame. Can you still cut it and meet this requirement? If this bike is for someone who is still growing, bear in mind that the saddle may need to be raised over time, and you might end up close to the minimum insertion mark.

Cutting it requires a hacksaw with a fine tooth blade (google for how fine), a mitre box and a clamp or two. It’s not difficult: cutting a carbon steerer is the same. Or get Decathlon to do it for you.

If you need a shorter one, either look yourself or ask Decathlon to source one for you.

[anonymous-user]

You can cut it, no problem. Hacksaw or similar. Mind the dust

Be sure that there is sufficient left so there is plenty in the frame when the saddle is at the right height

[GOATever]

gazza285 said:

You are advocating taking a brand new frame and either prising or grinding out the rivnuts, thus rendering the warranty invalid? What do you then suggest to do with the two 7mm holes now in the seat tube?

Yes, if you then insert the seatpost where you want it, and replace the riv nuts with new nuts ( they’ll be M5s) that will sort the holes out.

gazza285 said:

OP, have you contacted Decathlon? They might be willing to send you a shorter seat post. If not, then seat posts can be cut down, just ensure that you still have at least the minimum insertion depth, and that you clean up the cut end.

That’s the ‘proper’ thing to do. But I like hitting stuff with hammers / dremmeling them / cutting things off.

gazza285 said:

Do not take a screwdriver to the rivnuts.

Meh.

gazza285 said:

Is the saddle too high? Perhaps a smaller frame would be better for you.

That’s a bit like getting a new house because you don’t like the colour of the doors. I’m sure Decathlon would sort out a shorter seat post.

[gazza285]

GOATever said:

gazza285 said:

You are advocating taking a brand new frame and either prising or grinding out the rivnuts, thus rendering the warranty invalid? What do you then suggest to do with the two 7mm holes now in the seat tube?

Yes, if you then insert the seatpost where you want it, and replace the riv nuts with new nuts ( they’ll be M5s) that will sort the holes out.

How can you replace the rivnuts with the seat post in the way?

Edited by gazza285 on Friday 28th February 08:28

[lufbramatt]

Agree with Gazza no need to start hacking the frame around. Especially as I think this is a carbon framed bike and removing the nuts could do damage.

Few questions- how long is the seat post- how far is it getting stuck in the frame? Any burrs, carbon strands sticking out etc down the seat tube?

Is the seat clamp a conventional clamp or an expanding wedge arrangement which might be getting jammed?

Have they definitely given you the right diameter seat post for the frame?

[GOATever]

gazza285 said:

How can you replace the rivnuts with the seat post in the way?

Edited by gazza285 on Friday 28th February 08:28

You mark the point at which the post is at the correct height, through the holes, then cut the post accordingly, when you then put the new riv nuts in, there’s no problem. Given it is in fact a Carbon frame, I actually would be a bit cautious about removing the original nuts too, I didn’t notice it was CF frame. You could still trim the seat post though.

Edited by GOATever on Friday 28th February 12:00

[gazza285]

GOATever said:

gazza285 said:

How can you replace the rivnuts with the seat post in the way?

Edited by gazza285 on Friday 28th February 08:28

You mark the point at which the post is at the correct height, through the holes, then cut the post accordingly, when you then put the new riv nuts in, there’s no problem. Given it is in fact a Carbon frame, I actually would be a bit cautious about removing the original nuts too, I didn’t notice it was CF frame. You could still trim the seat post though.

At what point is any of this easier than just putting the seat post in as far as it will go, deciding how much lower you want it, and then cutting that amount off the post? You are making a simple job into something far more complicated than it needs to be.

Carbon, aluminium or steel, it doesn't matter what material the frame is made from, I'd still not be prising out the rivnut with a screwdriver, or taking a grinder to it, when there is absolutely no need.

[waynecyclist]

Just get a shorter seatpost.

If you do need a shorter seatpost maybe the frame is too large.