# Thomson seatpost decisions and questions...



## Ventruck (Mar 9, 2009)

Can't make up my mind to whether I'd want a setback set forward, or non-setback model. My current situations is as follows:

-I favor a "middle" saddle position that's not too far back or forward, and like working with the "rivet" of the saddle.
-OEM (Giant Carbon) post I have has setback (~23mm from what some sites say), and a bit much as I push the saddle all the way forward. Due to angle limitations and improper aesthetics, this seatpost can't be reversed.
-I also have a Profile Design Fast Forward which was on my hybrid bike to make up for a very aft position. Swapped that it into the road bike, only to find an opposite scenario where I slam the saddle as far back as possible.


Would perhaps be a no-brainer to go for a zero offset seatpost (inevitably considering Thomson), but I'm second guessing things.... 

The PD FF has 38mm forward offset whereas the Thomson Setback has 16mm. If I were to opt for a Thomson Setback (in the forward position), I have 2cm of clearance/leeway to the front the saddle rails compared to the PD FF. With the zero offset, I'd have <1cm of clearance to the back of the saddle rails compared to the OEM Giant post I got.

So in short, I'm thinking that the Thomson Setback might be more ideal with the amount of leeway it can offer if my butt and jewels morph down the road. Would appreciate other's opinions.


As far as aesthetics are concerned, I've seen one pic of a reverse/forward-mounted Thomson setback. Kinda ugly, but I doubt I'll have that much post exposed and my saddle would help in that department.


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## coasterbrake (Jun 10, 2006)

As long as you don't mind people telling you your seatpost is on backwards, everytime you talk to another cyclist.....then I say do what you've got to do to make your bike work for you.


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## Mark Kelly (Oct 27, 2009)

It sounds like you are riding the wrong frame.


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## Ventruck (Mar 9, 2009)

Mark Kelly said:


> It sounds like you are riding the wrong frame.


Favored saddle fore/aft position can be independent of whether or not the frame fits. I have no torso or each issues, I simply want to be in a certain position in relation to the pedals/cranks. Sorry if my OP somehow gave off the impression I was having such issues.


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## backinthesaddle (Nov 22, 2006)

Ventruck said:


> Favored saddle fore/aft position can be independent of whether or not the frame fits. I have no torso or each issues, I simply want to be in a certain position in relation to the pedals/cranks. Sorry if my OP somehow gave off the impression I was having such issues.


No...
If you are forced to put a Thomson on the bike, mounted backwards to make the bike fit properly, the bike does not fit you!

If it's a TT bike, then maybe...road bike...no go!


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## Dinosaur (Jan 29, 2004)

Whatever works. A Thomson setback mounted backwards would put me in my doctors office.


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## Mel Erickson (Feb 3, 2004)

If you've got a post with 23mm of setback and your saddle all the way forward and it works, I think a straight post would work better. You've already concluded that. I can't see where a Thomson setback post would work better. However, it's pretty easy to find out. I'm sure your LBS has a straight post they would lend you for a trial. Try it out and see. Personally, I couldn't stand to look at my bike with a Thomson post turned around. I also agree with other posters that there's something wrong. Either your bike or your preferred position is farked. However, to each his own.


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## FatTireFred (Jan 31, 2005)

backinthesaddle said:


> No...
> If you are forced to put a Thomson on the bike, mounted backwards to make the bike fit properly, the bike does not fit you!
> 
> If it's a TT bike, then maybe...road bike...no go!




sure he's a candidate for custom, but it apparently fits w/ that set up. this is def one where the balance of the bike is messed up


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## medimond (Apr 26, 2009)

My knees hurt just reading this thread. My knees couldn't handle being that far forward over my pedals. 

Honestly, why is this the favored position?


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## Ventruck (Mar 9, 2009)

medimond said:


> My knees hurt just reading this thread. My knees couldn't handle being that far forward over my pedals.
> 
> Honestly, why is this the favored position?


Is it that extreme? I'm lost (not necessarily trying to argue) to why my favored saddle position is seemingly a taboo. 

Ultimately, I'm still ~3cm behind the BB spindle (from the tip of the saddle) with the Fast Forward, and with a reverse'd Thomson Setback, I'll be a bit over 5cm behind the BB which is where I'm aiming to be - is that actually still too forward for people? Neither of my own seatposts (the PD FF and Giant OEM) are allowing me to do that. 

In short, I'm opting (or at least I thought I was....) for a relative "middle" position between what my two current posts offer, and the Thomson Setback can actually do that as well as the non-Setback model.

The reverse'd Thomson Setback will likely not look centered on the saddle's rails, but I'm thinking that in theory, it would offer the widest range of adjustment up flipping the seatpost either way for future cases, and my original dilemma (if it wasn't clear in the OP) is whether or not this is good rationale to opt for the Setback model. 

I will admit to things being seemingly uncertain about frame fit as I'm unable to achieve that favored 5-5.5cm position of the tip of the saddle behind the BB with the OEM Giant post and the saddle slammed forward. However, there no problems with reach (even if the saddle resided more rearward) and my seatpost/saddle height isn't at any "extremes" either. Was suggested that I may have a case of short femurs, but that is yet to be confirmed.


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## wim (Feb 28, 2005)

Ventruck said:


> Ultimately, I'm still ~3cm behind the BB spindle (from the tip of the saddle) with the Fast Forward, and with a reverse'd Thomson Setback, I'll be a bit over 5cm behind the BB which is where I'm aiming to be - is that actually still too forward for people?


I wouldn't say so. But what's puzzling me (and perhaps others as well) is why it takes a reversed Thomson setback to put the tip of the saddle 5 cm behind the center of the bottom bracket. Or do your 3 cm and 5 cm references refer to some other dimension?


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## Ventruck (Mar 9, 2009)

*Warning: bit wordy...*



wim said:


> I wouldn't say so. But what's puzzling me (and perhaps others as well) is why it takes a reversed Thomson setback to put the tip of the saddle 5 cm behind the center of the bottom bracket.


Judging by how my saddle mounted on the Giant OEM (which has ~25mm offset) post looks like to get close to that 5cm (behind the BB) position, it's very un-centered, so I figure that the Thomson Setback would be best set in the reverse position so the saddle is more centered on the clamp. I could maybe get away with the Setback in the original position, but the clamp will still be near the back end of the saddle rails. 

And again, the general idea of having the Setback post despite the need to take such a measure (reversing it) is that it would offer larger ranges of adjustment for whenever/if-ever down the road than the non-setback post. And that's what I was proposing for original debate, whether that's reasonable or not.


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## wim (Feb 28, 2005)

Not saying you don't have a valid point in there somewhere, but I just can't follow your explanation. Every frame I ever rode allowed me to put the saddle tip 5 cm behind the bottom bracket with the saddle rails more or less centered on the seat post clamp. Unless you have a specialty frame, I don't understand why it would take a turned-around seat post to get that 5 cm saddle setback with the rails centered.


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## ukbloke (Sep 1, 2007)

From an aesthetics-only point of view, the Thomson set-back post is fairly unappealing IMHO because of the bend. To have it in a reverse position, on a standard road bike, is just about the worst of all possible worlds, again purely judging on aesthetics (with apologies to the owner of that bike you posted). If you have to do this to make your fit work, then fair enough, but if you have any other options that can be made to work I would certainly do something different. The straight Thomson master-piece post on the other hand is a piece of art and would grace any bike. Having the saddle rails off-center is a much lesser evil, again all aesthetically speaking.

Just my 2c.


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## Ventruck (Mar 9, 2009)

wim said:


> Not saying you don't have a valid point in there somewhere, but I just can't follow your explanation. Every frame I ever rode allowed me to put the saddle tip 5 cm behind the bottom bracket with the saddle rails more or less centered on the seat post clamp. Unless you have a specialty frame, I don't understand why it would take a turned-around seat post to get that 5 cm saddle setback with the rails centered.


I could get things to work with a non-setback also, but as I said, the setback would give me that leeway for larger adjustments whenever/if-ever needed.

On a non-bitter note, I've come to the conclusion that the "perk" that I've been describing with the non-setback isn't really hot amongst any of the replies in general (whether it could be followed or not), leaving me to shoot for the non-setback. I do appreciate everyone's input. The number of disagreeing posts regarding the setback pretty much gives me an answer.


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## srracer (Sep 14, 2008)

Ventruck said:


> Is it that extreme? I'm lost (not necessarily trying to argue) to why my favored saddle position is seemingly a taboo.
> 
> Ultimately, I'm still ~3cm behind the BB spindle (from the tip of the saddle) with the Fast Forward, and with a reverse'd Thomson Setback, I'll be a bit over 5cm behind the BB which is where I'm aiming to be - is that actually still too forward for people? Neither of my own seatposts (the PD FF and Giant OEM) are allowing me to do that.


Hi Ventruck,

I realize I don't have many posts to my name (and indeed an relatively new to the sport myself) and so feel free to take my advice with a grain of salt (though my degree is in biomechanical engineering and bike setup was something I did a bit of research on when I started), but I wouldn't so much recommend setting your seat to where it is relative to the BB but instead to pay attention to where your knees are relative to your pedals.

As I look at your setup, my first reactions are:
- For a forward seat post like that with it so high above the TT, that your femurs would have to be relatively short and your calves relatively long to seem to make sense.

Then when I look at your bars and the stem that you have I would think you'd need a relatively long torso/arms for that forward seat post setting to make sense.

It's just that the combination of high seatpost extension combined with forward seat position and a long stem are a bit counter-active for a traditional fit.

There is fair debate over whether your knees should be directly over your pedals or slightly offset, but starting with knee-over-pedals is a reasonable launching point and then tweaking from there.

I always point friends that are new to bike setup to here:

http://www.jimlangley.net/crank/bikefit.html

Hope this helps,
-Chris


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## Ventruck (Mar 9, 2009)

*Post count =/= knowledge. *



srracer said:


> Hi Ventruck,
> 
> I realize I don't have many posts to my name (and indeed an relatively new to the sport myself) and so feel free to take my advice with a grain of salt (though my degree is in biomechanical engineering and bike setup was something I did a bit of research on when I started), but I wouldn't so much recommend setting your seat to where it is relative to the BB but instead to pay attention to where your knees are relative to your pedals.
> 
> ...


Already drew a conclusion to opting for the non-setback, but I do appreciate the input. My note of fore/aft position in relation to the BB is simply my way of reference for whenever I get on any non-setup bike.

Current position was produced by no other than trial and error on another bike (hybrid on the trainer) where I could get that setting. Nothing "exceptional" about the in question's stem length (100mm), but your take on my arms is seemingly true. I'm 5'10.5 on a Size L Giant TCR. It's recommended for slightly taller people on their chart, but it does fit for me


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