Please school me on setback seatposts...
 

I just want to make sure I have this correct:

1. Typical seat posts can have no setback (just a straight post with maybe some tilt adjustment at the clamp)

2. or they can have some setback at the clamp (actual clamp slide fore & aft along goose neck shape at top of post)

3. or they can have a bend along the post itself, as with the Thompson Elite. which doesn't mean the clamp area will have additional setback play...

Am I correct in saying a Thompson will have setback from the angled post bend, but NOT additional setback play at the clamp? (in other words, a straight post Thompson has NO setback?)

I currently need to move back further. Nice as they may look, I don't want to spend $75 on a Thompson if it only gives me the same setback as my current post (a Performance forte with the curved goose neck, perhaps a re-branded Kalloy Uno or something similar?).

does anyone know of a seat post that has both set back along the shaft and the clamp?
I've seen those wavy rounded bend models - not sure about those....this is for a road bike, I am staying away from really heavy suspension designs.

Just to be clear I have a short inseam, hence need a small frame and the seat tube angles are always around 75 degrees - I am much more comfortable on a 72 or 73, but cannot seem to find a 49cm frame with that geometry.....:mad:

I have a Thomson Elite on my Prophet and it allows you to slide the seat fore and aft on the rails. I use the setback seatpost because I didn't feel right with my knees essentially lined up over the pedals but I was out of adjustment space and couldn't move my seat any further back. Now, I'm able to set my seat so that my knees are just aft of the pedal spindle and all is well.

For my money, Thomson may make the best seatposts on the market.

Mike

Most seatpost have some kind of set back. Very few are straight posts with only tilt adjustment. The amount of set back varies from post to post and finding out how much set back a seat post has is a hit or miss affair. Most are probably in the 0.5" to 1" range.


Titec makes the El Norte Bent post with 1.5" of setback but be careful with it. It puts a lot of stress on the seat tube and can cause it to fail. Other then that you just have to dig to find the setback numbers.

Thomson's setback post has about the same amount of setback as your average $10 Kalloy post. Nothing additional. The regular Thomson has 0 setback, as you deduced. As mentioned above, the Titec post is pretty much your only option if you need more setback.

Titec gives you almost 1.5" of setback ...

take your normal seat on a normal offset post .. and slide it as far back on the rails as possible ... and that will be where the seat is located on the Titec El Norte setback post if you have a seat on it, and have it slid forward on the rails ...

http://www.silenzzzz.net/bike/current_003.jpg

it is more of a setback then the thomspon ... it still lets you adjust the angle of the seat ... has 2 bolts to clamp the seat in place instead of the normal 1 ...

i was split between the thomspon or the titec ... glad i went with the titec.

I believe this is correct. With the Thomson you still at best can only get "regular" setback. Not only that, but the Thomson seat clamp is longer than many other seatposts, so you may actually end up worse off by not being able to slide the saddle back as far.

Also you have to be careful with the setback post if you have a long seat tube since you can't lower it past the bend, but you'd have to run your post pretty low to get to that point. I vaguely remember measuring the bend at something like 8-10cm down from the rails. That should get the saddle low enough for old school "fistful of post" setups but not much lower than that.

The Thomsons are primarily designed for strength, so that's probably why they favor having the clamp directly centered over the post instead of cantilevered off the end like most setback posts. I have 3 Thomsons and really like them, by the way, so I hope I'm not coming across as bashing the product.

I'm not too jazzed about the looks of the Titec but my main concern is getting my butt back further and my knees behind the BB.

But what about this stress - what fails? The seatpost or the frame?
I should mention I'm a fatso - 220 lbs. The bikes are ridden on the road, not mtb.

eh, the titec will work for you then .. i am 235 ... and i ride MTB mostly ... my setback is on my MTB ... and i have taken 1 foot+ drop off's with it and hit the seat on the landing ... with no issue ...

less you have the seatpost pulled way out of the frame you are more likely going to bend / break the seat before you damage the frame ...

on my picture above .. over 80% of the seapost is inside the frame ... now if i had it to where it was above the min height reccomended for the post then there is a chance of damage to the frame .. but if someone has it that high, they likely need a larger frame anyways.

Hmm...doing searches on BF I see Titec's post is actually 35mm of setback; Oval Concepts' R910 says 50mm. I sure think that will look better on my road bikes. I'm afraid to look for the price - and CF at 170g also worries me at my weight...should I be afraid of that?

the Titec El Norte Bent is 50mm of setback not 35 ... 35 is their normal one ...

http://www.pricepoint.com/detail/167...e-Seatpost.htm

it is used mostly for downhill racing ... if it can handle that, it can handle being on a bike that is going down a paved road.

It says 1.5" - that's 38mm

My performance seatpost has 30mm

If I'm gonna plunk down any money for another seatpost it may as well give me what I'm buying it for - the Oval concepts is looking better...any feedback on those?

I broke the frame with it. My frame had an extended seat tube (the metal came up a long way past the seattube/top tube junction) that cracked. Just be careful with them.

"Just to be clear I have a short inseam, hence need a small frame and the seat tube angles are always around 75 degrees - I am much more comfortable on a 72 or 73, but cannot seem to find a 49cm frame with that geometry"

The reason for this is because u cant make a frame a 49 cms frame with that geometry. Well probably u can but u need a super long chain stays, so long that you probably will be able to put a motorcycle wheel in there. There are other reasons related with small bike geometry that i wont detail because are pretty obvious (years ago i found a triat girl asking for a frame in 45, 72 degrees and like 51 in lenght becasue that was what the tables and frame calculation formulas were saying it was the best match for her, took us like 2 months make her understan what was wrong) The same happen with super big frames. Im asuming that you are talking about road frames.

Regarding the seat back, u have them with seat back and with no seat back, even though u can slide the seat over the rails a non seat back seat wont give you the play u are looking for. Probably the bike you need is a xtra small compact configuration/geometry frameset. and use it with a regular seat tube (with seat back) and sort of a 12 cms stem. With a regular steel frame u wont be able to play that much with the position since u have short legs apparently. Sorry dude u are one of those cases that will always have problems with the position, so basically u have to look for what is comfortable for you and forget the standar or rules (tables and stuff), even if you want to look like lemond probably it wont happen ever. Just a touch of reality.

Good luck :)

I actually found one bike in my size specd with 73 degree ST - Cervelo ...

I've yet to test ride one but that may be my next bike.

The most comfortable bike I ever owned was a Miyata 110 - 1981 model. Smallest frame in that model, it was a 19.5" and had 72 or 73 degree parallel (same as HT). The chainstays were just over 17" (435mm). It was a typical sport tourer of that era (and a straight gauge entry level one to boot), so not the zippiest ride on earth, but as LeMond used to preach, better to have a frame you feel comfortable and 'fresh' on than something aggressive that beats you up.

Have you done your homework with regard to the proper saddle position on your bike? Have you checked your knee over pedal position using a plumbob? Do you have the saddle slid all the way back in the seat post cradle? Only after you answer these questions can you make an informed decision regarding the need for a more offset seat post.

FTI, the Thompson offset seat post does not have very much offset. A run of the mill Ritchey has more and is far cheaper.

Good luck.

I thought that vein of bike fitting has been debunked?

No one said you have to set the KOP exactly, but anyone more than 1.5 cm or so away is most likely off course.

Yes I have - done the plumb line, etc.

I know I don't really like the feel when I am kops-correct, and my bikes all place me pretty much there with the saddle centered in the post clamp. I currently have all my saddles jammed back as far as they will go, and I still find myself hanging my butt back over the saddle edge for power and comfort a lot.

I have been using Brooks saddles, but even with other plastic sadles I feel the need for more set back.

My current seatposts are a Performance Forte 27.2 road stem ($20) with 30mm setback, a Marin mtb post with a clamp that looks almost the same, and a Dura Ace 27.2 road with what looks like a bit less (20mm?).

I am not looking for excuses to spend money, and certainly not on carbon fiber stuff, but the only one I am seeing online is the Oval Concepts 910 - I can get it online for $139. It would give me about 15-20mm more setback than the Performance.


My concerns are:
1. would this 15-20 mm make a huge difference?
2. am I safe on a carbon fiber post at 220 lbs. with the saddle & clamp pushed all the way back?

Am I understanding correctly:

- you achieve KOP with the saddle in the middle of the rails and your current seat post?

- you don't like the feel of KOP so you pushed your saddle all the way back?

- you still don't like the way this feels so now you want an even more setback seat post?

If this is all correct, I think you are nuts!:notamused: - no disrespect of course.:love:

You are already way behind the bottom bracket and want to go even farther. Sounds like a great way to tear up your knees. Also, no way to spin circles so forget about that.

Maybe you just need a longer top tube so you can stretch out some more, or try a longer stem. Slamming your seat back into the next zip code is not an answer for anything.

I understand your reaction; all I know is what feels right. I know I can spin better scooting forward; but I reckon I can do that with my seat pushed further back by just sliding forward ...

I should add I have relatively large feet for my height (I take a 47 bike shoe). My wife has the same inseam as me, or just a bit longer but runs her saddle a good inch or more lower than mine. We couldn't figure that one out for the longest time and then it dawned on me - I have a lot more extension at the lower extremity (She takes a mens size 36 shoe). She not only likes her seat lower, she runs it more forward in the seatpost clamp. and, yes, her bikes already have shorter top tubes than mine.

So I am going by feel and experience (I didn't just start riding yesterday)...but then again maybe I am nuts!:o

I'm also thinking with more set back I can center the saddle in the rails rather than have it jammed all the way back. so a seat post with more setback might help, yes?

I just measured the set back on my current posts and also measured an additional 15-20mm off the back of my saddles - I think it would def. make a difference.

I decided to perhaps pass on the Oval concepts carbon fiber post...I saw a nice old photo of Jens Voigt with the similar Look Ergopower carbon fiber seat post, with his saddle jammed all the way back. Looked tres cool....then I remembered him riding into Paris on the final day of this year's TdF with a broken seat post....WWJD, indeed!! Thanks for the heads up, mein herr!

nevertheless, was just tootling along on my old Trek this morning...my butt hanging way over the back of the addle as usual. Put it this way - on my most used leather Brooks saddle, my sitbone divots are just starting to show up. They are basically in between the metal rivets at very back edge of the saddle.....

He could be making up for a too-low saddle by scooting back so far.

do you mean Voight? I'm sure that's it - he's a big guy, and 75% legs!

If you meant me, no, I have my seat set up at a good height when sitting squarely on the saddle with the current seatposts. And just to be clear, I am judging this exclusive of the top tube/stem reach. I'm not trying to get more upper body extension, I am strictly looking at my pedaling from the hips down. It just feels like I need to be back further.

This makes sense, and hence my mentioning I think the bike for me is the Cervelo soloist in 48 or the next size up (for a 53cm top tube - the 48 might be too cramped unless I use a 13 or 4 cm stem). Those bikes have a 73 degree seat tube angle regardless of size...this is pretty hard to find indeed.