[FlipSide]

My friend just got his new bike (Gary Fisher Sugar+) and he's running his seat post very high. I told him to make sure he never rides his bike with the bottom of the seat post above the bottom of the top-tube...and preferably 1" lower than the bottom of the top-tube.

Would it be safe to run it at, for example, just .25" or .5" below the bottom of the top tube?

Thanks!

 

[SwisSlesS]

Isn't there a minimum insertion marking on the seat tube. I think that's a pretty accurate thing to go by.

 

[jet]

3.5" to 4" is good, most minimums are about that much.

 

[FlipSide]

I don't know if we're talking about the same thing... I'm talking about the insertion minimum so that it doesn't damage the frame...is that what you're talking about when you say 3.5"-4"?

Thanks for your answers!

 

[Serial Midget]

The minimum insertion point varies with the length of the seat post, the longer the post the higher the minimum insertion point. Most seat posts are marked with such information.

 

[sub6]

Originally posted by swiss_less ...

Originally posted by jet ...

Originally posted by Serial Midget ...

No, no, and no.

People are talking about two different things. Obviously all seatposts have a mark on them that you're not supposed to go above.

Flipside isn't talking about that. You can't run your seatpost such that the bottom edge of it is above the bottom edge of your top tube weld, otherwise you can rip the seat tube off the top tube. See Babar's thread in the Lounge a few weeks ago for a shining example of what happens when you do that.

That height is entirely unrelated to the max seatpost height.



Flip - I'd say you're probably safe with going .25-.5" below that weld, the lower the better obviously but I think that would be alright.

 

[Silver]

Originally posted by swiss_less
Isn't there a minimum insertion marking on the seat tube. I think that's a pretty accurate thing to go by.

That's so you don't snap the post, not the frame.

You should have it below the bottom of the top tube in the frame, otherwise you're asking for trouble.

 

[FlipSide]

Good! Thanks a lot!

I'll inform my friend about that.

 

[indieboy]

make sure you have the guy at the right seat post height if he's running it that high. you should have it high enough that when your cranks are at the 12 o'clock / 6 o'clock positon that when you put your heel out at the 6 o'clock position that your heel makes a flat line w/ the middle of the pedal spindle. bein over extended isn't a good thing but neither is having a frame that is to small for you, which it might be if he has the seat post run that long.

 

[Rustmouse]

Keep in mind, a human body taking a 6foot straight drop to flat can produce 1000 lbs of force...

the more seatpost the better. At a minimum, 1/2 inch below the bottom of the top tube (to allow for the weakened spot from the weld and the heat affected area)