# Shortening a gusseted seat tube



## nbrennan (Oct 31, 2006)

I've seen a couple MTBR threads about shortening the seat tube of an Ice Cream truck. I know it can be done, but I've been unable to find a frame builder local to me to do the work. I get the impression its too small a job for someone to make room in their schedule. If that changes I'm happy to support a pro plying their trade. If this experiment pans out I'll likely pursue a similar custom build with a shorter wheelbase.

That said, I'm considering doing it myself with an angle grinder, hack saw, cutting guide, and drill. I have a pretty good idea of how to remove the necessary material but I dont have a strategy to close the vent hole that I expect to find inside the gusset tubing. Would leaving an open vent hole create a stress riser or any issue aside from exposure to the elements?

I'm interested in removing to gusset to make room for a dropper post. At the moment I can't quite fit a 125 mm dropper given my saddle height. An extra 1.5" off the ST length should do the trick.

Happy to post more pictures if that helps.


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## m-gineering (Feb 5, 2012)

nbrennan said:


> I've seen a couple MTBR threads about shortening the seat tube of an Ice Cream truck. I know it can be done, but I've been unable to find a frame builder local to me to do the work. I get the impression its too small a job for someone to make room in their schedule. If that changes I'm happy to support a pro plying their trade. If this experiment pans out I'll likely pursue a similar custom build with a shorter wheelbase.
> 
> That said, I'm considering doing it myself with an angle grinder, hack saw, cutting guide, and drill. I have a pretty good idea of how to remove the necessary material but I dont have a strategy to close the vent hole that I expect to find inside the gusset tubing. Would leaving an open vent hole create a stress riser or any issue aside from exposure to the elements?
> 
> ...


Angle grinders and frames often end in tears

Can't you get away with lopping of the ST at the top of the gusset, and brazing on a collar?


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## nbrennan (Oct 31, 2006)

m-gineering said:


> Angle grinders and frames often end in tears
> 
> Can't you get away with lopping of the ST at the top of the gusset, and brazing on a collar?


Yeah, an angle grinder seems like a bit of a hack job so I'm wary of doing it. I think I could render it usable but I imagine I'd create a few more problems along the way.

Taking it to the top of the gusset makes sense, but I dont have the skills to add an integrated collar.


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## life behind bars (May 24, 2014)

If you are confident that you can wield a hacksaw and a couple of files successfully you can do this. Carefully hacksaw the gusset leaving a bit of it. It'll take a couple of different cuts to get it close. Do not cut into the top or seat tube. Carefully finish with a sharp flat file. Shorten seat tube to desired length and square it up with the flat file. Take your time, don't get in a hurry. Since you're going to be touching up paint, a dab of body filler to close up the vent hole. Finish it, prime it with good quality primer and paint it.


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## GrayJay (May 16, 2011)

In my opinion, cleanly removing the gusset from the TT is probably a more challenging job than the alternative of leaving the brace in place and brazing or TIG welding a new seatpost binder.

Get an old junk frame and practice with a hacksaw until you are confident with cutting up tubing.

Example of the binder that you would then need is;
SEAT BINDER AND BOLT - PREMITERED :: SMALL PARTS :: BRAZON/SMALL PARTS :: Nova Cycles Supply Inc.

You don't necessarily need a skilled framebuilder to help with adding the binder, most any non-bike welding/machine shop could easily braze or TIG weld the binder for you for minimal cost if you have it all prepped for them.


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## nbrennan (Oct 31, 2006)

Thanks for the info guys. There are some good threads about this here on MTBR. Below are the two most helpful links... I think I'll have to DIY this project and post back with results.

http://forums.mtbr.com/fat-bikes/shortening-surly-fatbike-seat-tube-834786.html

https://bikingtoplay.blogspot.com/2017/12/karate-monkey-surgery.html


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## abrooks (Feb 1, 2015)

I managed to cut my seat tube down on my Boardman FS Pro using a jubilee clip and a hacksaw. Re-slotted the tube and drilled the bottom of it as stress relief. No problem,,


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## nbrennan (Oct 31, 2006)

did you use a hack saw to re-slot the seat tube? did you drill the stress relief hole and then cut towards it? i was thinking about using a punch to center the drill bit. I've never done any frame modification so i'm trying to be pretty circumspect about it. Thanks for your input.


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## scottzg (Sep 27, 2006)

nbrennan said:


> did you use a hack saw to re-slot the seat tube? did you drill the stress relief hole and then cut towards it? i was thinking about using a punch to center the drill bit.


That's how i do it. I use 2 hacksaw blades in the saw and saw towards the stress hole. Clean it up with a file.


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## abrooks (Feb 1, 2015)

scottzg said:


> That's how i do it. I use 2 hacksaw blades in the saw and saw towards the stress hole. Clean it up with a file.


That's how I did mine. I cut around 18mm from the length of the seat tube.

First I marked the tube with a fine sharpie pen, then placed a jubilee aligned with the pen mark. Once tightened up, used as an edge guide for the hacksaw.

I didn't have enough tube left to extend the original slot, so I added a slot directly opposite the original. Slotted using a hacksaw and followed up with a needle file to increase the slot width. 
You must drill the relief hole first, use a punch to centre the drill.

I can now use a 125mm dropper.

Looking at your picture, I don't think that you'll be able to lose much more than 15mm, or you won't be able to use a seatclamp


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## nbrennan (Oct 31, 2006)

I plan on removing the gusset as well, so the seat tube will be trimmed to just below where the gusset currently is.


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