# Zero setback vs correct weight distribution



## bbulmann (Aug 22, 2012)

Here's a question, in short, about if my zero offset seatpost & very little setback moves my weight distribution too far forward on a road bike, and if so, is a better solution to go with a steeper seat tube angle and a normal amount of offset, effectively giving me the same contact points but bringing the rear wheel closer to where it should be for weight bearing purposes.

I've read many articles & comments that correct weight distribution (55% rear/45% front) is as important as a good fit, at least for optimal performance. (Keith Bontrager argued in the past that 55/45 was actually more important than KOPS.)

I'm in the long legs/short torso club. I've been fit, using both a pro BG fit and KOPS, with a very forward saddle position & very little setback, requiring a zero offset seatpost. (I guess Lemond got the long femurs and I got the short ones.) I'm pretty flexible and have high saddle to bar drop, although I usually need a short top tube (or short stem) and short reach bars- currently liking my Dedas- so that I'm not too stretched out.

I recently rode an older TT bike with a 77 degree STA but converted to road bars and zero offset seatpost. A little weird of a setup, but, it felt good and got my 3 points of contact right where they needed to be. It made me wonder about the more relaxed geometry of my racing frames- with their slack seat tube angles and longer top tubes- and if my push forward to get the same fit is taking too much weight off my back wheel.

Any thoughts? Other than yes, I would benefit from a custom frame, and I wish I had taken physics in high school?

Thanks!


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## cxwrench (Nov 9, 2004)

bbulmann said:


> Here's a question, in short, about _if my zero offset seatpost & very little setback moves my weight distribution too far forward on a road bike, and if so, is a better solution to go with a steeper seat tube angle and a normal amount of offset,_ effectively giving me the same contact points but bringing the rear wheel closer to where it should be for weight bearing purposes.


Who knows? We can't see how you fit on anything w/o photos. 



> I've read many articles & comments that correct weight distribution (55% rear/45% front) is as important as a good fit, at least for optimal performance. (Keith Bontrager argued in the past that 55/45 was actually more important than KOPS.)
> 
> I'm in the _long legs/short torso club_. I've been fit, using both a pro BG fit and KOPS, with a_ very forward saddle position & very little setback_, requiring a zero offset seatpost. (I guess Lemond got the long femurs and I got the short ones.) I'm pretty flexible and have high saddle to bar drop, although I usually need a short top tube (or short stem) and short reach bars- currently liking my Dedas- so that I'm not too stretched out.


So...long legs _but_ short femurs/short torso/short arms?



> I recently rode an older TT bike with a 77 degree STA but converted to road bars and zero offset seatpost. A little weird of a setup, but, it felt good and got my 3 points of contact right where they needed to be. It made me wonder about the more relaxed geometry of my racing frames- with their slack seat tube angles and longer top tubes- _and if my push forward to get the same fit is taking too much weight off my back wheel._
> 
> Any thoughts? Other than yes, I would benefit from a custom frame, and I wish I had taken physics in high school?
> 
> Thanks!


You don't push yourself forward to make the reach work, you bring the front end back to whatever position you need to be over the bottom bracket. What you'd end up doing would be taking weight off the front end, not moving it away from the rear end...even if your position is forward biased you probably wouldn't take much weight off the rear end.


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## bbulmann (Aug 22, 2012)

I'm not asking about my fit... This question could apply to anyone. Hypothetically, if someone places their saddle on a zero offset seatpost on a steep (TT style) frame vs using a setback seatpost on a slack frame, more of their body weight is hanging over the back wheel in the latter setup than the former, unless I'm wrong. Maybe I'll set these two up using my required saddle to BB setback and see how big the difference is in saddle to rear axle.

I guess the bigger question is, how important is weight distribution after finding the right fit? The same 3 points of contact can be arranged in the same proportions to each other for the same fit on 3 different bikes, but your positioning over the wheels could be completely different. Many people say that the old rule of thumb of placing the bars in line of sight with the front axle had as much to do with proper reach adjustmeant as it did with correct weight distribution over the front wheel. I mean, mountain bikers are all about weight distribution- looking at how much of their weight is on the back wheel depending on what kind of riding they do. Seems to reason that there'd be an optimal ratio for road riding, and in the past it was always 55/45.

As for fit, I never said short arms... I'm not an albatross, but my latest fitter simply recommended short reach bars as a better alternative to regular bars on short stems. I like it so far.

Fit is simply the relationship between the three points of contact between the bike and the rider, and for me, according to my fitter, the main thing that is different about me vs a "normal" proportioned rider is that given my optimal seatpost height and saddle setback, if I use a normal offset seatpost, I'm not even able to clamp on a saddle where it needs to be for optimal placement. Thus, the zero offset seatpost, and even still with the saddle clamped pretty far forward. (This was true on my Tarmac, my Merckx, and my Sampson... anything with less than 75 degree STA or so put my saddle contact point too far back behind the BB.)

As for "You don't push yourself forward to make the reach work, you bring the front end back to whatever position you need to be over the bottom bracket..." 
Maybe I understand it differently from my experience being fitted on different bikes.
Correct positioning over the BB is determined by knee angle at maximum extension, position of knee over spindle, and hip angle, the first two of which are determed by saddle placement, not bar placement. Hip angle is better achieved by adjusting drop up or down than by bringing reach in or out, although reach can be changed to help achieve optimal elbow angle, balance, etc. If you're bringing the front end back to affect positioning over BB, a rider's elbows could come out too far; or, if moving it back in conjunction with saddle offset, their hip angle increases. Reach was the last part of the equation in every fit I've had done. Either way, if reach is adjusted back, weight is taken off the front wheel. likewise, if saddle placement is moved forward 2cm and reach kept the same but drop increased, weight is taken off the rear wheel. I'm reminded of the extreme of this situation: the fast forward seatpost, and its claimed intent to help tranform a traditional bike into a tri bike by bringing your saddle placement forward and putting your elbows over the bars for use with extensions. While a rider might even achieve the right tri fit with one, that rear wheel is still way back there and hasn't been brought forward to be under the saddle like it is in TT/tri specific frames with the steeper STA. So, you just put the majority of your body weight on your front axle.


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## Jay Strongbow (May 8, 2010)

Just move your seat back 25mm and go for a ride and you'll have your answer. (I think, I'm only guessing at the question because I started to glaze over and stopped reading)

If you're assuming all bikes are designed to handle best with x amount of set back you'd be wrong. Storck for one are designed for not. And set back doesn't necessarily determine weight distribution. You could have set forward and if you're sitting straight up there's not going to be any weight over the front whee. And by the same token you could be set way back but be super aggressive and have plenty of weight over the front.


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## GlobalGuy (Jun 9, 2015)

bbulmann said:


> Here's a question, in short, about if my zero offset seatpost & very little setback moves my weight distribution too far forward on a road bike, and if so, is a better solution to go with a steeper seat tube angle and a normal amount of offset, effectively giving me the same contact points but bringing the rear wheel closer to where it should be for weight bearing purposes.
> 
> I've read many articles & comments that correct weight distribution (55% rear/45% front) is as important as a good fit, at least for optimal performance. (Keith Bontrager argued in the past that 55/45 was actually more important than KOPS.)
> 
> Thanks!


Here is an excellent written or very readable article that touches on what you ask. Despite the title what the article's main point is about having the correct balance or weight distribution on the bike and how to get it. 

If you haven't read it give it a perusal and let me know what you think. 

https://www.stevehoggbikefitting.com/bikefit/2011/05/seat-set-back-for-road-bikes/

Good luck in your search and bike setup.


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## bvber (Apr 23, 2011)

bbulmann said:


> Here's a question, in short, about *if* my zero offset seatpost & very little setback moves my weight distribution too far forward on a road bike, and *if* so,


Looks like you will have to try it first and see if it does. By the way, what do you consider very little move, 1mm, 2mm, 3mm or 1cm?


> is a better solution to go with a steeper seat tube angle and a normal amount of offset, effectively giving me the same contact points but bringing the rear wheel closer to where it should be for weight bearing purposes.


Will you be racing? If not, just enjoy your ride as long as it's not causing pain or other limiting factor.


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## Gregory Taylor (Mar 29, 2002)

Do you actually know whether your current position with the zero setback seatpost is giving you a skewed weight distribution? Without actually measuring this, it seems to me that you're just shooting in the dark. 

Get a bathroom scale, and hop on holding your bike. That's your total weight. 

Put the bike in a stationary trainer that holds the rear wheel, put the scale under the front wheel (get the bike as level as possible) and hop on. Get into your position on the bike. Read the scale - that gives you the weight on the front wheel. 

Subtract weight on front wheel from the total weight - that should give you the weight on the rear wheel.


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## tvad (Aug 31, 2003)

Gregory Taylor said:


> Do you actually know whether your current position with the zero setback seatpost is giving you a skewed weight distribution? Without actually measuring this, it seems to me that you're just shooting in the dark.
> 
> Get a bathroom scale, and hop on holding your bike. That's your total weight.
> 
> ...


Excellent advice!


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## cxwrench (Nov 9, 2004)

Gregory Taylor said:


> Do you actually know whether your current position with the zero setback seatpost is giving you a skewed weight distribution? Without actually measuring this, it seems to me that you're just shooting in the dark.
> 
> Get a bathroom scale, and hop on holding your bike. That's your total weight.
> 
> ...


This should tell the OP all he needs to know. Great advice.


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## joeinchi (Sep 24, 2010)

I think you have a good theoretical understanding of the dynamics and rationale for your current position. What you really need to determine, bbulmann, is *How YOU like the way your bike feels?*

If you wonder if your bike would corner better if you pushed the saddle back, then I'd suggest you go for a ride and see for yourself. Comfort, efficiency, residual soreness ... it's all about trial and error.

Grab your multi-tool, head out for a ride and make 5mm fore aft adjustments until your find the sweet spot. And if you still have your offset seatpost, put that on so you can experience the full range.


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## bbulmann (Aug 22, 2012)

I have done so and found the sweet spot of my fit. My question is, since that sweet spot puts my saddle position very far forward (on a frame with traditional racing geometry), am I compromising efficiency by also moving weight distribution forward and taking weight off the rear wheel. A G3 powermeter will tell me how many watts the rear hub is receiving, but if not enought weight is on the rear axle, a portion of that power is not transferred to the ground contact and is thus lost.


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## bbulmann (Aug 22, 2012)

cxwrench said:


> This should tell the OP all he needs to know. Great advice.


I shall conduct this experiment and post the results here when available- in case anyone else besides me is interested. I appreciate everyone's advice.


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## MerlinAma (Oct 11, 2005)

bbulmann said:


> ?.... but if not enought weight is on the rear axle, a portion of that power is not transferred to the ground contact and is thus lost.


Really? Is the rear wheel slipping? 

If not where is the power lost? How would it not be transferred to the ground?


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## bbulmann (Aug 22, 2012)

MerlinAma said:


> Really? Is the rear wheel slipping?
> 
> If not where is the power lost? How would it not be transferred to the ground?


If I hypothetically create 325 watts of power as transferred through the drivetrain, and a sub-optimal proportion of rider weight is on the back wheel, then perhaps- I don't know, maybe 300 watts worth (or its equivalent) is actually utilized in pushing the machine forward due to increased rolling resistance on the front wheel. It's not slipping, that would be major. It's about efficiency. I could be mistaken in my understanding of the transfer of power to the rear tire contact point, and why so many in the past have emphasized 55% of weight distribution resting on that spot. If weight distribution does not affect performance, is it an outdated concept?


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## Jay Strongbow (May 8, 2010)

bbulmann said:


> If I hypothetically create 325 watts of power as transferred through the drivetrain, and a sub-optimal proportion of rider weight is on the back wheel, then perhaps- I don't know, maybe 300 watts worth (or its equivalent) is actually utilized in pushing the machine forward due to increased rolling resistance on the front wheel. It's not slipping, that would be major. It's about efficiency. I could be mistaken in my understanding of the transfer of power to the rear tire contact point, and why so many in the past have emphasized 55% of weight distribution resting on that spot. If weight distribution does not affect performance, is it an outdated concept?


oh my. People who talk about weight distribution mattering are talking with regard to bike handling and splitting the load between your hands and butt not power. Position relative to the pedals matters a lot for power but the resulting weight distributions doesn't.


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## Drew Eckhardt (Nov 11, 2009)

bbulmann said:


> If I hypothetically create 325 watts of power as transferred through the drivetrain, and a sub-optimal proportion of rider weight is on the back wheel, then perhaps- I don't know, maybe 300 watts worth (or its equivalent) is actually utilized in pushing the machine forward due to increased rolling resistance on the front wheel.


No.

Rolling resistance is the product of weight and the Coefficient of Rolling Resistance.

With the same Crr on both ends any weight you move forwards will decrease rolling ressitance in back by the same amount it increases in front.


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## jkc (Jun 23, 2014)

I believe Keith Bontrager's argument against KOPS was more inline with proper fit based on leg's mechanics to maximize power delivery rather than adjusting the seat placement as a after thought. A form and function thing.

Were you fitted to a bike that was not an ideal in the first place? Made do with what's on hand? Did the fitter give you an indication of the "ideal" range and does that match your steed? Sound like you have too big of a bike but that just a stab in the dark.


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## ibericb (Oct 28, 2014)

You are confusing rolling resistance with traction. They are completely different effects, and arise from different origins.

If you have sufficient weight on the rear so that the tire is not slipping under any power you supply to it, that is traction of the tire on the surface is sufficient for the power supplied, then increasing the weight on the rear wheel further is not going to increase the acceleration of the bike. Unless you're a beast, you shouldn't have to worry about sufficient weight on the rear to prevent wheel slipping during acceleration.

The reason TT bikes are designed with steep seat tube angles is to distribute the weight increasingly to the front wheel for better handling stability when stretched out on the aerobars.

You're right - high school physics would have helped. I suggest you look at the Wikipedia articles on rolling resistance and then on traction.


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## kiwisimon (Oct 30, 2002)

ibericb said:


> The reason TT bikes are designed with steep seat tube angles is to distribute the weight increasingly to the front wheel for better handling stability when stretched out on the aerobars.
> .


I thought the steeper ST angles set forward position were to make the transition to running more smoothly. but the stretched out aero thing works as well.


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## ibericb (Oct 28, 2014)

kiwisimon said:


> I thought the steeper ST angles set forward position were to make the transition to running more smoothly. but the stretched out aero thing works as well.


That too, at least something like that for triathletes.

Those who get into ergonomics and efficiency, and fitting bikes for triathletes, point to the hip/leg angle on a TT bike preserving the hamstring muscles for running in tri's. The bike OEM's I've seen comment about the steeper seat tube angles point to better handling stability when out on the aero bars. Both would be beneficial for tri's, the handling for pure time trials.


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## robt57 (Jul 23, 2011)

Consider that as opposed to weight distribution fr/rr, one considers fore-aft CG [Center of Gravity] in terms of a window. If you compromise setback without lengthening the front center of a bike you push your fore/aft CG weight to the front edge of said window. Past the front edge?? Sure you can slide you cleats back on the shoe to negate some setback issue as it pertains to your joints in relation to the BB. But to what extent will you be pushing to the front of said CG window on the bike?

I will answer that question by saying to the point of instability quite possibly. perhaps especially when your back wheel hits a whoop?


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## ibericb (Oct 28, 2014)

robt57 said:


> Consider that as opposed to weight distribution fr/rr, one considers fore-aft CG [Center of Gravity] in terms of a window. If you compromise setback without lengthening the front center of a bike you push your fore/aft CG weight to the front edge of said window. Past the front edge?? Sure you can slide you cleats back on the shoe to negate some setback issue as it pertains to your joints in relation to the BB. But to what extent will you be pushing to the front of said CG window on the bike?
> 
> I will answer that question by saying to the point of instability quite possibly. perhaps especially when your back wheel hits a whoop?


It's a great point, and a good way of thinking about it.

Returning to the steep seat tube angle of the TT bike, there is much more to a TT bike geometry than just a steep seat tube angle. Using Trek's Speed Concept (Large) and Emonda SL (58cm) frames as two reference points (because I can easily look up and compare the current frame geometry specs), the Speed Concept has the steep seat tube angle (78° vs 73°), but it also has a more relaxed head angle (72° vs 73.8°), more offset in the fork (4.5 vs 4.0 cm), more trail (6.0 vs 5.6 cm), a shorter chainstay length (40.0 vs 41.1 cm), and a resultant longer wheelbase (101 vs 99.2 cm). So while the seat tube becomes more upright, the other elements of geometry combine to position the CG back in it's proper range for overall stability, preserving a rational weight distribution. 

I should backtrack on my previous statement about steep seat tube angle for handling, whipped out in haste, as I didn't state it well. The seat tube angle, when coupled with the other geometry elements preserves handling when in the low, forward position on the aero bars. The goal is to get down and long (stretched out) for aerodynamic advantage. As the upper body comes down that would close the torso-hip-leg angle to a difficult acute angle. On a conventional road bike geometry (e.g., Emonda) that change alone would make both breathing and pedaling with power difficult. The steeper seat tube allows the critical body geometry to be preserved while in that desirable aero position. Along with that rider position change then must come the other frame geometry changes, which together work to keep CG and weight distribution in the needed range to preserve stability and handling.


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## woodys737 (Dec 31, 2005)

kiwisimon said:


> I thought the steeper ST angles set forward position were to make the transition to running more smoothly. but the stretched out aero thing works as well.


The reason a time trial bike has a steeper STA than a road bike is to allow the rider to move fwd (relative to the BB) which allows them to reduce their frontal area while preserving (keeping open) the hip angle. This all contributes to two huge advantages: less frontal area (flat back, low head position, etc...) means less drag; and preserving the hip angle means more power. 

Triathlon bikes have steeper STA's than TT bikes to lessen the stress on the hamstrings which is important for the run after the bike split.

If you've ever spent any time on a TT or tri bike you understand they don't handle well at all so I'm not entirely clear what ibericb is getting at.


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## Jay Strongbow (May 8, 2010)

ibericb said:


> I should backtrack on my previous statement about steep seat tube angle for handling, whipped out in haste, as I didn't state it well. The seat tube angle, when coupled with the other geometry elements preserves handling when in the low, forward position on the aero bars. The goal is to get down and long (stretched out) for aerodynamic advantage. As the upper body comes down that would close the torso-hip-leg angle to a difficult acute angle. On a conventional road bike geometry (e.g., Emonda) that change alone would make both breathing and pedaling with power difficult. The steeper seat tube allows the critical body geometry to be preserved while in that desirable aero position. Along with that rider position change then must come the other frame geometry changes, which together work to keep CG and weight distribution in the needed range to preserve stability and handling.


You would have been better off just retracting the statement instead of making it worse. Steep seat tubes on those bikes has nothing to do with handling. End of story.


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## ibericb (Oct 28, 2014)

Jay Strongbow said:


> You would have been better off just retracting the statement instead of making it worse. Steep seat tubes on those bikes has nothing to do with handling. End of story.


Yep - I fumbled it completely (got sidetracked by kids crisis last night).


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## robt57 (Jul 23, 2011)

Jay Strongbow said:


> You would have been better off just retracting the statement instead of making it worse. Steep seat tubes on those bikes has nothing to do with handling. End of story.



I can say my bike with the steepest STA has the longest front Center of all my non off road bikes. The shortest chainstay and out of my 'road' frames, the longest WB. A TT bike that has geometry for a forward fore/aft CG riding position. And low bars for a rider rotated forward to get out of the air. Yes, a Time Trial bike. ;0


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