Mountain Bike Reviews Forum banner

2007 Stumpjumper FSR Seatpost travel

5K views 8 replies 5 participants last post by  JonathanGennick 
#1 ·
Is four-inches the minimum insertion for a Stumpjumper FSR seatpost? If I keep to the minimum insertion, how much room do I have in that interrupted seat-tube to drop the post when I get to a downhill? Will I have at least four extra inches to maneuver the post up and down as needed?

Same question for the Enduro SL, if anyone happens to know the answer there.
 
#2 ·
It depends on the size of the frame....

but generally 4" is the minimum. Minimum for a Small or Medium frame is 2 3/4". For an XL or an L you'd have another 4" + or - of seat tube left to drop the seat. That is IF Specialized is no longer putting the seat post stop in the seat tube. I have an 05 Stumpy in XL that has a dimple inside the seat tube that prevents the seat post from dropping beyond a set point, it stops the seat post about 1 1/2" above the opening in the bottom of the seat tube. Not a bad thing as it prevents protrusion of the seat post below the tube and eliminates the possibility of contact with the shock under full compression. But it does limit how far you can drop the seat post. I'm not sure if newer Stumpy frames have a stop or not.

So let's do the math. Minimum insertion on an XL frame is 4 inches. Total length of seat tube 8 inches. That leaves you 4 inches below the minimum insertion. If the frame has the seat post stop in it, subtract approximately 1 1/2 inches from the 4 inches of leftover seat tube. You get 2 1/2 inches of free seat tube for a drop. So, no you won't get 4 inches of drop from the minimum insertion point. That is assuming a stock lenght seat post of 400mm. This is also assuming that your seat tube has the stop in it.

Now what you can do that will get you at least a 4 inch drop is cut the stock seat post! A friend of mine did this with his Stumpy. First thing to do is find your ideal trail position, i.e. knee slightly bent at the bottom of the pedal stroke, or whatever works for you. Then go to the minimum insertion hole at the back of the seat tube and with a scratch awl of similar instrument make a mark on the seat post, just enough to take the ano off that spot. Now remove the seat post and measure 1/4 to 1/2" below the mark and cut the post at that point. The stock 400mm seat post usually sits a good 1 1/2 to 2 inches below the minimum for most riders. You've now gained drop room! You should be able to get your 4 inch drop, possibly a little more if your frame doesn't have the stop in the seat tube. But you do have to be careful when running the seat post back up after the down hill. I have marked my seat post (removed a little ano from the post) so that I can quickly return to regular ride height without going past minimum insertion. Just run the post up until the shinny silver spot is just above the seat collar, clamp the qr and go. You won't be able to slam the post to the head with this method, but it should get you enough drop to be comfortable on the down hills.

This is all assuming an XL or L frame of course. Smaller frames won't see as much gain from cutting the post, but then with a smaller frame you usually don't need to drop the post as much either.

Good Dirt
 
#3 ·
Fantastic explanation Squash, thank you.

I'm wanting to get into full suspension this year. I like their bikes, and I have a very, very accommodating Specialized dealer about an hour away from my house. But that interrupted seat tube has always concerned me.

I am looking at a medium bike, btw. It sounds like I won't get all that much of a drop even after I cut the tube.

I'm headed to the dealer this evening. I can measure then. I'm sort of wanting to make up my mind on what to get first though. I am leaning towards three different bikes right now, and am stuck in the Valley of Indecision. Tried to sell my wife on buying all three over breakfast this morning, but, uh, that idea didn't fly.
 
#4 ·
Fantastic explanation Squash, thank you.

I'm wanting to get into full suspension this year. I like their bikes, and I have a very, very accommodating Specialized dealer about an hour away from my house. But that interrupted seat tube has always concerned me.

I am looking at a medium bike, btw. It sounds like I won't get all that much of a drop even after I cut the tube.

I'm headed to the dealer this evening. I can measure then. I'm sort of wanting to make up my mind on what to get first though. I am leaning towards three different bikes right now, and am stuck in the Valley of Indecision. Tried to sell my wife on buying all three over breakfast this morning, but, uh, that idea didn't fly.
 
#6 ·
I have a 2007 SJ FSR Comp in the medium size. There is a "stop" built into the seat tube. You will not be able to get a satisfactory drop without cutting the post. I haven't personally measured or done any cutting on mine, but I don't think you'd be able to cut very much off without getting into "minimum insertion" issues.
 
#7 ·
Use what Squash said: seat at maximum height for XC, mark with awl, and cut below. The only thing I would recommend is to add an extra inch to your mark. This will not only insure you won't have a problem in the future, but it keeps more of the seatpost in the frame to prevent creaks and additional wear and tear from having the seat at the minimum insertion point.

I just hacked off an inch off the bottom of my seatpost and that was all I needed.
 
#9 ·
Student Driver said:
Hooray for a good response! Now just buy the bike, or any bike, already! :)
Done! Went in tonight to have another look, to try and sort out which bike to buy. Sat on the Enduro SL Expert again. Should not have done that. Took it for a ride up and down the bike path. Shouldn't have let temptation suck me in like that. Took it up and down the hill near the shop. Oops! Really shouldn't have done that. Spent another 15-20 minutes with both the SL and the Stumpy together in the parking lot, swapping back and forth to see how they compared. Both are darn good bikes, and it was a really tough call, but my heart went to the Enduro SL. So I bought it.

And now I have to get up early tomorrow and go out of town until late Sunday night. I won't be able to get the bike out in some dirt until Monday. Sigh...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top