# Cutting seat post topper



## kingpin (Jul 5, 2005)

Anyone ever cut a Trek madone seatpost topper? I have one thats to long and is colour matched to my bike. The only issue I can see is re-doing the slot for the clamp.


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## cxwrench (Nov 9, 2004)

You DO NOT cut Trek seat masts or frames.


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## kingpin (Jul 5, 2005)

Not talking about the mast. The topper. It was cut at some point.


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## crit_boy (Aug 6, 2013)

kingpin said:


> Not talking about the mast. The topper. It was cut at some point.


What is a seat post topper? 
A picture or link would be great.


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## kingpin (Jul 5, 2005)




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## crit_boy (Aug 6, 2013)

So, the thing that you have decided to call a "topper" is actually called a "Seat Mast Cap" (link). 

CX has said, you don't cut them. 

If you look at the link, Trek sells two sizes. If the small one is too big, you bought a bike that is too big for you.


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## cxwrench (Nov 9, 2004)

As I posted previously and as is clearly written on the seat tube "This is a no-cut system, DO NOT cut'. 

Do NOT cut any part of the system.


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## kingpin (Jul 5, 2005)

Right. It makes no sense. Is it cause I'll end up with an unsafe length? Both pieces are the same thickness as my Scott Addict and I have a 3" Ritchie topper on it. Trek would not recommend you cut them so they can sell you a $200 shorter version that ends up being the same length as if I cut mine! I want to look at this logically or have a valid reason why not.


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## cxwrench (Nov 9, 2004)

kingpin said:


> Right. It makes no sense. Is it cause I'll end up with an unsafe length? Both pieces are the same thickness as my Scott Addict and I have a 3" Ritchie topper on it. Trek would not recommend you cut them so they can sell you a $200 shorter version that ends up being the same length as if I cut mine! I want to look at this logically or have a valid reason why not.


Because the manufacturer _specifically states DO NOT CUT. _ If that's not good enough for you, good luck on making it work and not getting killed.


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## kingpin (Jul 5, 2005)

Thanks.You just follow the rest of the sheep blindly.


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## cxwrench (Nov 9, 2004)

kingpin said:


> Thanks.You just follow the rest of the sheep blindly.


Listen tool-time, I follow what the engineers that designed the system say. If they say don't cut it, I'm not going to cut it because I believe they have a good reason for making it that way. If you think you're smarter than the engineers that designed this stuff, have at it. But don't ever accuse me of being a sheep that's following anyone blindly. You've already admitted that this will involve not only cutting the cap but re-cutting the expansion groove. I'm willing to be you won't get this right and you'll have cracking issues w/ the cap. Which of course won't be covered by warranty. If it's been cut already it's not an issue, go for it.


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## Peter P. (Dec 30, 2006)

Here's why I think you shouldn't cut it: The wall thickness further up the mast may not be the same as at the current clamp area. This may be done for flex-tuning or to save weight.
There could be some layered material beneath the carbon weave such as metal, to strengthen the clamp area. While you may not see it, it's possible it's there. Re-cutting the slot could cause stress risers in the clamp area; I'll assume the original slot area is molded rather than cut into the raw mast material. Cutting the mast, because it's not a simple square cut such as on a carbon steerer tube, brings up a whole set of new concerns. You COULD cut it, then check it before every ride. However, carbon has a fast failure mode in leveraged locations such as on your seat mast. It could fail in the course of a single ride. If you can't make the cut then put it on a test machine to see how many cycles of force to failure it can withstand, you'll just have to ride it to find out. If you're willing to do that, go ahead and cut. I wouldn't do it, but if you choose to do so, I'd recommend one of those carbon specific hacksaw blades, probably double up the blades on the hacksaw when cutting the slot to make the slot wide enough.


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## crit_boy (Aug 6, 2013)

I think you should cut it. 

Forcing you to buy a shorter one is just a means to rip you off. Clearly, the frame designers and materials people are just tricking you. Their fancy college degrees, computer design programs, and years of experience are simply marketing BS. They can't possible know more than you - you have Google and youtube to tell you everything you need to know about carbon fiber design and modification. 

Trek must make millions of dollars each year on that scam. Stick it to the "man".


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## MMsRepBike (Apr 1, 2014)

Well... if you're going to cut carbon stuff up, use a diamond cutting wheel and let the wheel do the cutting. Don't use a hacksaw or whatever.


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## cxwrench (Nov 9, 2004)

crit_boy said:


> I think you should cut it.
> 
> Forcing you to buy a shorter one is just a means to rip you off. Clearly, the frame designers and materials people are just tricking you. Their fancy college degrees, computer design programs, and years of experience are simply marketing BS. They can't possible know more than you - you have Google and youtube to tell you everything you need to know about carbon fiber design and modification.
> 
> Trek must make millions of dollars each year on that scam. Stick it to the "man".


'You must spread some Reputation around before giving it to crit_boy again'. I tried, sorry


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## Tachycardic (Mar 31, 2013)

kingpin said:


> Thanks.You just follow the rest of the sheep blindly.


Ugh. That's such an ignorant reply. Do you wear a helmet while riding your bike? Yes? You're a sheep. Do you wear socks on your rides? Yeah? Bam! You're a sheep. Does your Madone still have a chain, or have you converted to belt drive? Uh oh...looks like we have another sheep here...

All joking aside, you CAN cut the cap/topper. You CAN try to reinstall the clamp. You CAN fasten it to your bike and ride it. It's 'Murica baby! You CAN do all these things, but if you crash because it fails and you injure, or kill, yourself or others, then it's yo a$$.


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## velodog (Sep 26, 2007)

Tachycardic said:


> Ugh. That's such an ignorant reply. Do you wear a helmet while riding your bike? Yes? You're a sheep. Do you wear socks on your rides? Yeah? Bam! You're a sheep. Does your Madone still have a chain, or have you converted to belt drive? Uh oh...looks like we have another sheep here...
> 
> All joking aside, you CAN cut the cap/topper. You CAN try to reinstall the clamp. You CAN fasten it to your bike and ride it. It's 'Murica baby! You CAN do all these things, but if you crash because it fails and you injure, or kill, yourself or others, then it's yo a$$.


Aw hell, a failure in that area probably won't kill him, but he'll probably have to remove the seat mast from his...well, you know.


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## crit_boy (Aug 6, 2013)

Tachycardic said:


> if you crash because it fails and you injure, or kill, yourself or others, then it's yo a$$.


The seat post failures I have seen did not result in a$$ injury. They result in a heinous bleeding wound originating from just outside the taint up along the inner thigh. Granted, I have never seen the injury from failed and splintering carbon. I can only imagine that it is better than failed aluminum. 

OP quit being a sheeple: "Cut that post" "Cut that post" "Cut that post"


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## cxwrench (Nov 9, 2004)

crit_boy said:


> The seat post failures I have seen did not result in a$$ injury. They result in a heinous bleeding wound originating from just outside the taint up along the inner thigh. Granted, I have never seen the injury from failed and splintering carbon. I can only imagine that it is better than failed aluminum.
> 
> OP quit being a sheeple: "Cut that post" "Cut that post" "Cut that post"


I hope the OP has a YouTube channel...not that I'd want to see his injuries, but just the carbon carnage.


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## duriel (Oct 10, 2013)

Just cut it, he can wear a cup when he rides.


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## Lombard (May 8, 2014)

Kingpin, before you cut it, can you put me in your will? I'm not saying cutting it will kill you, I just like the idea of being in your will.


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