‘Grinding’ a ledge ...
 

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[Closed] ‘Grinding’ a ledge out of the seattube of a carbon frame

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I have a Norco Range Carbon in XL. It has a ‘ledge’ of about 4mm at 200mm into the seat tube for approx 1/4 if it’s diameter (coming off one side). It’s about 4mm thick too.

I want to fit a bigger drop post than the 125mm I have now. So I want to remove the stopper. I’m not sure if it’s meant to be there or just left over from making the frame shape. I see no reason why it can’t be removed (no different than frames with the post hanging out the bottom of a tower). It just needs to be done without damaging the rest of the tube.

The question is how?! I was thinking about trying to get a real long rotory burr/file...but I can’t find any.

i tried a normal ‘dome’ file but it was slow progress and I’m not sure if it would risk rubbing the tube beyond the lip.

Any ideas gents?


 
Posted : 03/05/2018 9:35 pm
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I have done similar..... If you have an old seat tube of a smaller size, get some sandpaper / wet and dry fairly coarse to start and wrap around the post. I used double sided tape to stop it slipping. Then wind the post down grinding away the ridge (apply side load as you turn obviously to ensure lip is getting worn away)

<span style="font-size: 0.8rem;">My frame had a similar lip to one side just before the bottle holder eyelets which prevented my post from sliding all the way down. Worked a treat and not dead yet 🙂 </span>


 
Posted : 03/05/2018 10:50 pm
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I’m not sure if it’s meant to be there or just left over from making the frame shape.

In which case I would not grind it out. At the very least, you'll void the warranty. If it is meant to be there, you might want to find out why.


 
Posted : 04/05/2018 12:20 am
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Likely a stop to prevent you ramming the seat post into the main pivot.. or where they stopped reaming the seat tube to clean up the top tube to seat post junction.

I reamed out a 26.8mm alloy seat tube to 27.2 but wouldn't fancy doing it with carbon.

Looking at Norcos spec, the xl comes with a 150 reverb.. looks like the reverb has the lowest/smallest insertion of all 150mm posts at 215mm, 235 for the 170.
Oneup 225@150, 243@170
Transfer 245@150


 
Posted : 04/05/2018 6:24 am
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Cheers gents. My bike is a 2016 and has a 125mm dropper (420mm total) from new.

I run it 40mm out of the tube. So a 150mm MIGHT just fit. Probably not ideal though.

Ideally i I want a 170mm but need that to go deeper into the tube.

I can technically see no reason why this is there unless it’s to stop the post going too far down and damaging something (it opens out past this stopper).

i’ll have a think, I reckon a dremel with a flexy extension on would do it fine.

cheers


 
Posted : 04/05/2018 7:57 am
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125mm dropper (420mm total) from new.I run it 40mm out of the tube. So a 150mm MIGHT just fit. Probably not ideal though. Ideally i I want a 170mm

Err 125 + 40 = 165mm ... are you sure you want a 170mm dropper?


 
Posted : 04/05/2018 8:48 am
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Yes, but run it further down the tube- so I get the same ‘seat up’ ride height but get it lower to the frane when it’s down. My 125mm remains too high as it is.

cheers


 
Posted : 04/05/2018 9:25 am
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revive should fit and give you 160mm drop

https://www.bikeyoke.de/en/seatpost-revive-160-30-9.html

could try mine if you wanted to check first.


 
Posted : 04/05/2018 9:54 am
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Yes, but run it further down the tube- so I get the same ‘seat up’ ride height but get it lower to the frane when it’s down. My 125mm remains too high as it is.

Yeah but you've only got 40mm to play with, as you said you ran your current 125 post 40mm out of the seat tube. Anyway, crack on.


 
Posted : 04/05/2018 10:02 am
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Yes, but run it further down the tube

I thunk what Steve is getting at is that a 170mm dropper, fit flush to the frame, will be 5mm* higher at full extension than your current 125. This is irrespective of the point to which you can get the bottom of the post as the collar will bottom out on the top of the seat tube, so you'll need to cut down the seat tube too or you'll need a smaller stack** height post.

*this assumes you've got 40mm from the underside of your collar to the top of the seat post clamp. If that 40mm includes your collar then it'll be significantly more than 5mm.

**i guess there's a proper term for this but i mean the total underside of collar to underside of rail height.


 
Posted : 04/05/2018 10:11 am
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You can limit the return height on the OneUp (and some others?) so if the 170 can be made to fit inside then the height can be tweaked exactly to chosen length (within limits).


 
Posted : 04/05/2018 10:57 am
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something similar in my pivot, my 150mm transfer was very nearly slammed against this "stop" but had a load of post sticking out the frame still. fortunately it did just fit for my riding height, but i wanted to be able to drop the post all the way into the frame for really steep stuff and couldn't....

I emailed Pivot, who are generally really good about stuff like this, for instance they said yeah go ahead a drill a drain hole in you BB, and we will still honor any warranty issues.... and for this they said not to do it, and to leave it there, it would weaken the frame if i reemed out the seat tube. so didnt.

I have just fitted the oneup 170 though, and that fits.

of course, just cos i was told to not do it on my pivot doesn't mean you cant on yours....


 
Posted : 04/05/2018 12:45 pm
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Cheers gents. Got a wicked deal on a Vyron and it is just the right height with the stopper in. I’d prefer the seat to drop lower but that isn’t possible on this frame.

cheers all


 
Posted : 05/05/2018 10:49 pm

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