[ewl]

I'm wondering how much exposed seatpost people are generally running on their Burners or Five Spots.

I'm still doing final adjustments on my new burner and am finding myself with between 9-10 inches of seatpost (from stem clamp to base of post head) showing. Is this too much? I've been looking at posted images and have seen the full spectrum from just a few inches to what looks to be well over a foot. Is there an average or good guideline for what the norm is? I'm really just curious at this point if I should be on a medium rather than a small.

Aside from this worry, the couple of rides I've been on with the new bike have been awesome! Now I'm thinking I should have gotten a 5 spot, as I am having a hard time staying on the ground - catching air is soooo much fun with full suspension. I already want more travel!

 

[endo verendo]

Just as long as there's at least 4" of post in the frame, then you're ok. There are threads about this. The Turner seat tubes flare out after that and make no contact with the post.

I think he was more worried about his frame size, not about how much post is in his seat tube. I've got 25cm or 9-3/4" from my rails to my collar on my small XCE.

 

[Bikezilla]

As Steve3 said, you don't need more than 4" of insertion. Be sure to have a long post and shoot for getting the post down to the seat tube - top tube junction, preferably midway or to the base of the junction.

A few of us run a lot of post. Myself included. I used to run as much as 9"+ I need it for XC'ish extention. But the technical riding forced me to keep it down around 8-ish. Even at 9"+ I was still getting down to near the base of the junction.

 

[ewl]

Thanks for the responses.

As Endo noted I'm most concerned about my overall frame size. I've read the posts detailing the minimum insertion point etc., I'm now just worried about being on too small of a frame and trying to determine if a medium wouldn't be a better fit based on the fact that I need to have 9+ inches of seatpost for general xc type riding. Again I'm just wondering if this length is in the 'norm' for turner geometry.

Also seems to start to get a little funky looking with so much seatpost exposed - as my wife said when I finished building up the bike - "what's with the seatpost?"

 

[Blue Shorts]

I'm running around 9.5 inches of post above the collar. It sems to be pretty normal for Turner bikes. The slanting top tube requires more post. No big deal.

 

[Bikezilla]

I just ran down to measure it. I'm running 9.5" from the post clamp to the point where post just begins to widen beneath the seat clamp (nearly 10" clamp to rails)...and that's in my low technical terrain mode. In an all out grinding XC mode I like it a an inch higher, for leg extention. But it's a PITA to get on and off the seat then.

JMO-I'm the farthest thing from an expert:

Size wise, you should consider where you want your center of mass, your arm extention, and how much foward lean vs. uprightness you want. Of course it all can be compensated for with components and adjustments.

A smaller frame is more manuverable in technical terrain. A larger frame will be more stable and also lends itself to optimise XC efforts. (ex. up and down fire roads) If you are a backwoods kind of guy go for the smaller size. If you are a open and maintained trail type of person go larger.

Personally I'm on the size cusp as well. By nature I prefer a larger more streched out feel, but I ride very tight technical terrain and deep down inside I know I'd hate myself the first time I couldn't clear something b/c of a bigger bike. I'm out there for the tecnical challenge. for me the XC stuff can be refreshing but for the most part it's just a means to get to the fun.

 

[SSINGA]

As Steve3 said, you don't need more than 4" of insertion. Be sure to have a long post and shoot for getting the post down to the seat tube - top tube junction, preferably midway or to the base of the junction.

FYI..A 410mm post is approx 16" long which would give you much more than the required 4" with 9 inches showing

 

[ewl]

Wow, thanks everyone for the advice and the measurements! This definitely helps me feel that I'm not freakishly off the mark here with a 9 inch seatpost. I'm feeling a bit better about the small size.

Now if the rain would stop so I could get out for a ride...

 

[marzz]

I'm no engineer but is this true?

Just as long as there's at least 4" of post in the frame, then you're ok. There are threads about this. The Turner seat tubes flare out after that and make no contact with the post.

Why would the seat tube flare out after only 4inches?
Wouldn't it be stronger if the seat tube be straight gage so that when your seat post goes down over 4" theres constant contact with the seat post throughout its entire length? Is there a reason for this?....it seems to me that the seat tube/ top tube junction is a high stress area from the leverage on the seat tube from your weight on the saddle. Less flex, and less stress on that area I'd figure.. Just curious

 

[Bulldog]

9" for XC here. No worries.

 

[incubus]

Ideally you'd not only want 4" of insertion length but for the post to come to the toptube/seattube junction as well. However, with Turners, you get that seattube brace that might not necessitate it going down that far.

In any case, provided you meet the seatposts min insertion length, that insertion intersects the toptube junction or the below the upper weld of the brace and your top-tube length is comfortable, the frame fits. Don't worry about how much exposed seattube.

 

[Flying Wombat]

Marzz, "Why would the seat tube flare out after only 4inches?
Wouldn't it be stronger if the seat tube be straight gage so that when your seat post goes down over 4" theres constant contact with the seat post throughout its entire length? Is there a reason for this?....it seems to me that the seat tube/ top tube junction is a high stress area from the leverage on the seat tube from your weight on the saddle. Less flex, and less stress on that area I'd figure.. Just curious"

I think that is so there can be more surface area to weld to the bottom bracket machining. That is probably the most stressed area of the bike so many bikes flare out the seatpost in that region.
I run about 10 inches in XC mode on my small 5-spot and have had no problems. I like the standover and maneuverability of the small frame, it feels kinda like a squishy BMX bike. Good for the tech bits at South Mountain.

 

[marzz]

I think that is so there can be more surface area to weld to the bottom bracket machining. That is probably the most stressed area of the bike so many bikes flare out the seatpost in that region.

Why not use bigger diameter seat tube in that case, and omit the extra step and cost of making the tubing flare out. I think 27.2 seat tube is kinda small for a bike like the 5-spot anyway.

 

[Bulldog]

Why not use bigger diameter seat tube in that case, and omit the extra step and cost of making the tubing flare out. I think 27.2 seat tube is kinda small for a bike like the 5-spot anyway.

I think every aggressive-use bike should use a 31.6 seatpost.

 

[incubus]

Isn't 27.2 unofficially the 'standard size' for mountain bikes? Maybe Turner don't know that there are other sizes available?

Knowing full well that there isn't really a standard size.

 

[Orangerider]

Isn't 27.2 unofficially the 'standard size' for mountain bikes? Maybe Turner don't know that there are other sizes available?

Knowing full well that there isn't really a standard size.

My Cherry had a 28.6 seatpost dia. Until I found Thompson, I bent quite a few, and everytime I went into the bike shop they would try to tell me I was crazy, it had to be a 26.8 because "no one uses 28.6".

 

[slowrider]

How much post?

As long as you have the minimum amount of post below the top of the seat tube your probably ok, except that some frames I've seen have quite a lot of seat tube above the top tube and with a longer seatpose and when riding in the saddle you can over time stress the frame at the top of the seat tube. I was just reminded last week of that when I saw a guy riding an Azonic Saber with the seat tube above the seatpost ripped open like a flower. He had the whole mess Magivered together with a hase clamp! He was riding a bike way too small for him and had a 410mm post sticking way up.

 

[Slacker]

Seat tube flaring

A couple of people have queried why the seat tube flares out after the initial 4" or so.

This will be because a larger diameter tube is stronger than a smaller diameter tube of the same weight, or conversly, can be made lighter for the required strength.

It is also true that the seat tube would be even stronger if the seat post were to extend down further inside a non-flared seat tube.

However, once you've achieved sufficient design strength there is no point in making the component even stronger. You will make it heavier than it needs to be and you will also transfer stress to another part of the frame making that other part more likely to fail.

Hope that helps.

 

[Monte]

A couple of people have queried why the seat tube flares out after the initial 4" or so.

This will be because a larger diameter tube is stronger than a smaller diameter tube of the same weight, or conversly, can be made lighter for the required strength.

It is also true that the seat tube would be even stronger if the seat post were to extend down further inside a non-flared seat tube.

However, once you've achieved sufficient design strength there is no point in making the component even stronger. You will make it heavier than it needs to be and you will also transfer stress to another part of the frame making that other part more likely to fail.

Hope that helps.

The "flare out" people are mentioning is internal, not external. The tubing outside diameter doesn't change, it's double butted tubing. Common to lots of bikes these days.

Monte

 

[Slacker]

Oops

The "flare out" people are mentioning is internal, not external. The tubing outside diameter doesn't change, it's double butted tubing. Common to lots of bikes these days.

Monte

Think I'll double butt out then