Seatmast Cutting Strategy

[bikerboy337]

First go around cutting a seat mast so sorry for the basic question, but wanted some reassurance before I actually cut.

I’ve got all my measurements correct so no questions about that, my question is… seatmast has the topper whereby I can add spacers inside to get to my correct seat height (up to 35mm of adjustment up). My original plan was to cut to the exact height I need, but my concern becomes if I need to lower it after I dial everything in by like 1-2mm… my feeling is cutting such a small amount off the tube will not be easy, even with the proper guide…

Would I be better served cutting it like 5mm lower than needed and planning to add 5mm spacer to get my height. This would allow me to lower in 1mm increments if needed, while still being able to raise 25mm if needed as well (won’t need that much at all)….

Does it make sense to cut it a few mm lower than needed to ensure I don’t need a 1-2mm cut after to get it just right? Or is a 1-2mm cut not a big deal with a guide tool and I would be fine trimming it a bit if needed after the first cut.

Would love to hear thoughts from those that have set up seatmasts before…

[gospastic]

I've had to take a mm off a steerer tube to get it to sit correctly with an expander plug installed. I used a rotary tool with sanding discs parallel to the top surface. I marked around the tube with some painters tape to the point I needed to sand down to. You could try this if needed if you cut to the exact height but then eventually need to go a bit lower.

[AngryScientist]

Yes, I would leave yourself some room to go both up or down. Even if you are dialed right now, changing a saddle, or shoes or pedals or something in the future may necessitate a slight move up or down.

[echelon_john]

Leave room, and for 1-2mm it’s sanding/grinding not cutting.

And don’t forget to debut the edges inside and out.

[aaronffs]

tangentially related question... are seatmast toppers supposed to be a total pain to put on? bought a ritchey one for my interclub, thoroughly covered the thing with carbon paste, but I pretty much have to whack it with a mallet to get it all the way on, leaves me a little concerned...

[jds108]

Originally Posted by aaronffs

tangentially related question... are seatmast toppers supposed to be a total pain to put on? bought a ritchey one for my interclub, thoroughly covered the thing with carbon paste, but I pretty much have to whack it with a mallet to get it all the way on, leaves me a little concerned...

I don't own a bike with a seatmast, but reading this I have to ask: why not use grease if the fit is so tight? Carbon paste is only going to make it more difficult to fit.

[prototoast]

Originally Posted by aaronffs

tangentially related question... are seatmast toppers supposed to be a total pain to put on? bought a ritchey one for my interclub, thoroughly covered the thing with carbon paste, but I pretty much have to whack it with a mallet to get it all the way on, leaves me a little concerned...

Tight fitting is probably based on paint thickness. Otherwise, no, it's not supposed to be hard to put on. I would clean off the carbon paste if it's that tight.

[aaronffs]

Originally Posted by jds108

I don't own a bike with a seatmast, but reading this I have to ask: why not use grease if the fit is so tight? Carbon paste is only going to make it more difficult to fit.

first time ever dealing with one, the ritchey manual mentions carbon paste so just went that direction

Originally Posted by prototoast

Tight fitting is probably based on paint thickness. Otherwise, no, it's not supposed to be hard to put on. I would clean off the carbon paste if it's that tight.

frame showed up with the paint already chipped off at the top of the seatmast, so that sounds like the likely issue to me then, thanks


edit: switching from carbon paste to grease helped significantly, cheers mates

[bikerboy337]

My painter mentioned I may need to do some light sanding of the paint for the seat mast… mines been fine but if painted, a light sanding under the mast should work fine. Mine is a tight fit but nothing that needs sanding at this point….

[dustyrider]

Any chance you’ve explored a shorter “seatpost” saddle combo already? I’d be trying everything under the sun before cutting, so I’m sure you have too!

[bikerboy337]

It’s an uncut seatmast from a new frame so needs close to 3” taken off… the cap I’m using only adds a few cm above the mast, so definitely needs to come down a bit….

Thanks all, got my answer now and I’ll measure about 5 times before I cut, but add 5mm to my cut to allow some slight adjustment of a few mm without a recut of the mast….

Thanks again all! Just like to confirm my thoughts before proceeding with something that can’t be undone….

[FriarQuade]

Depends on what saddle you like. A SLR is one of the lowest stack heights (rail center to seating surface) and if you happen to like that one, I wouldn't cut it more than 3mm shorter than need be. If your saddle tastes are more in the middle of the stack range, 5mm seems about right.

Pedal choice could be a factor as well. Most road pedals are pretty close but if you wanted to go to or from a MTB style pedal that's a pretty big variable.

[bikerboy337]

Well, thanks for the thoughts all, measured and remeasured about 15 times and finally taped it up and made the cut this afternoon. All went well.

Used 4mm of spacers in the top cap, cut was clean and when installed, my saddle is right at the 74.5cm seat height that I use on all my bikes. I’ve got the 4mm of spacers so I can go down a mm or 2 if needed as I dial in fit on this new bike and can go up an additional 30mm if needed down the line… although can’t imagine I’d grow any more as I’m late 40s….

Anyways thanks again, always great to bounce my thoughts off this crew before I do something that I can’t undo….

[AngryScientist]

Wow, that looks like a great color, and the matching topper really looks seamless.

Are there photos of this full bike somewhere?

If not, there should be!

[tootall]

Looks clean. You did what I was thinking on the cut, leave as much mast as possible remaining while still using just a few spacers to give yourself a little adjustment without having to cut. The advantage I see to that strategy is that the next person can take mast off if necessary, but much harder (or impossible ?) to add mast.