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  1. #1
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    fore/aft saddle position

    Just curious as to how the rest of you are positioned on your saddles. All the books tell you to make sure that when plum bobbed you bisect the spindle. I prefer to be about a centimeter behind. Does anyone have any pro/con info on the the best fore/aft and knee placement especially for performance and racing. And also is there any advantage to having a setback seatpost on a mt bike?

  2. #2
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    Attmept at some answers

    1. Does anyone have any pro/con info on the the best fore/aft and knee placement especially for performance and racing.

    The positioning of you knee for/aft of the pedals affects amount of flextion and extension at the knee joint. The further forward you are the less your knee is going to flex and extend. Less motion at the knee means less activation of the Quadaceps muscle group, and more of the pedaling force is generated by the Glutes. Thats why tri bikes have such forward positions. Its deseriable for a triathlete to save his quads for the run and use the glutes to pedal as much as possible. A fore position generally is thought to lend its self to spinning, while a behind the spindle position lens its self to low rpm grinding.I have never seen an actual data on the topic but that seems to be the general consensus. So I would say the Pros of being over the spindle are
    1. Effective contribution of all muscle groups to power production.
    2. Better high speed cornering due to more weight on the front wheel. (So long as its not steep)
    3. Spin dont mash
    Cons.
    1. More weight on front wheel = more endos on steep technical stuff.
    2. Necessitates the use of a longer stem which is heavier and does not (IMHO) steer as well.

    The advantages of a setback post are that they move your weight back which is desirable for steep techy stuff.

    Remember that the reccomdations in books regarding bike fit are meant to be a starting point. From there you need to adjust to riding style and feel. 1 cm behind the cranks is not drastic at all. Its probably more common to be a little behind the cranks than right on top. My advice would be experiment and find a position that you like.
    Hope that answers something
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  3. #3
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    ...that is great info. Thanks much. I still feel a little cramped so I think I will slap on a little longer stem which I have laying around. See how that feels.

  4. #4
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    As Pedal said, it's basically spin vs Mash and all his points are dead on. I don't think you'll find many MTB's set up with the dead ontop the spindle setup, most I think you'll find 1,2,3 or even 4cm behind it depending on the disciplin and riding style. I do know that I have personally experienced how much more easily you can spin when the saddle is further forward compared to back, so it's a compromise to make sure you can spin good but still use those quads for some big torque when you need it.
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  5. #5
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    I have mine set "directly over the pedal axle with the plumb bob" approach. I set my racing bike up the same, and have the same seat height on both my XC/road bike. Seems to work well for me, too far back seems to give a loss of power from what i've found. Everyone is different though.

  6. #6
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    Sometimes it is a tradoff of power, comfort and even bike geometry.
    I have been riding MTB for 12 years, road riding for 6 and am no way a great racer or fit specialist. Until mid year of this year I kept my knee maybe 1 cm behind the spindle and used zero setback seat posts on both my mtb and roadie. No matter how much riding I did, I always seemed to get tired in my upper body first and then my legs would go shortly after when riding mtb or have my hands fall asleep after an hour or so on the roadie. Well, this summer, I ended up moving my the saddle on my roadie back as far as it would go and did not change anything else and you know what...I loved it. No more tired/asleep hands, felt I had more power when climbing. Felt better in the drops and ended up being faster over my typical courses. I did the same to my MTB and it was a love/hate relationship. It did become easier on my hands and arms but hated climbing anything relatively steep because the front end became just too light no matter how far forward I was on the saddle. For me the short chainstays on my GF sugar and tall saddle position for me was not a good combo for climbing. I solved this by buying a 29er hardtail frame with 1" longer chainstays and I no longer have to fight to keep the front end down and am much more comfortable on anything technical with no loss of speed. In fact I might even be faster now. Anyway, that is my story and I am sticking to it.
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  7. #7
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    Where are you guys placing the plumb bob?? Should be on the small bone protrusion below the knee.

    What do you guys think about the method stated in the Andy Pruitt book? He states that you place the plumb drop over the front of the knee and instead of using the pedal axel, he uses the most forward part of the crank arm as the intersection point.

    His rationale is that the small bone protrusion's position varies to much relative to the front of the knee from person to person.
    Last edited by Poncharelli; 11-21-2006 at 12:01 PM.

  8. #8
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    I've always used the small bump below my knee. Except on my knees, it doesn't seem to be that small? Almost looks like I have two knees when my leg is bent in certain positions!

  9. #9
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    I never tried the plumb bob to see exactly, but I found that I was much more comfortable with my saddle farther towards the rear. I can move around the cockpit easier and feel better when I get into the technical stuff. It also helps me keep my weight over the rear on climbs.

    I ride it back to the extent that I had to switch to a setback seatpost in order to stop breaking saddles. As far as power and stroke, I would like to think I have a pretty good stroke. This seems like more of a practice and less of a location issue and, I don't notice a difference in which parts of my legs tire quickest.

    In the end, I would think that bike geometry has a lot to do with it as well as personal preference.

    I always tweek stuff like saddle position or height a bit, to see which I like best.

  10. #10
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    ...I agree that the bikes geometry has a lot to do with fore/aft. On my trail bike forward seems to work great but on my new Anthem forward just seems to cramped and seems to defeat the intended purpose of a race bike. The Anthem with its steep angles just begs the rider to be streched out. I guess that was my original problem and why I wrote this original post. I was trying to set my race bike up like a trail bike...and that ain't gunuh work. So, now I have to find that find line on the Anthem. I want all the performance but I want to be comfortable too. To streched out equals low back issues. To far forward-quad and knee issues. So, after 2 weeks on the new bike, 1-2 cms behind the spindles seems perfect. Thanks to all for all the great info.

  11. #11
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    Try

    Your old saddle positinon with a longer stem. Might put your upper body in a better position and keep your weight over the rear for traction
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  12. #12
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    http://www.wobblenaught.com/

    Find a location near you that offers this service and your woes will go away...I don't work for them, just a satisfied customer

  13. #13
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    pruitt - position of plumb bob

    Quote Originally Posted by Poncharelli
    Where are you guys placing the plumb bob?? Should be on the small bone protrusion below the knee.

    What do you guys think about the method stated in the Andy Pruitt book? He states that you place the plumb drop over the front of the knee and instead of using the pedal axel, he uses the most forward part of the crank arm as the intersection point.

    His rationale is that the small bone protrusion's position varies to much relative to the front of the knee from person to person.
    I've done dozens of fits, usually on folks experiencing pains/aches, but also for new bikes, etc. For years, I've done front of knee cap, front of crankarm method, as Pruitt suggests in his book. Pruitt is probably the most well-known and well-respected medical bike fitter in the United States, so I was glad to read in his book that I was doing it the way he does. However, for most folks, the bone below the knee, center of pedal axle method produces the some result as Pruitt's method.

    Also, based on somewhat subjective analysis of power meter data, I definitely think you lose power with the seat too far back.

    Also, as one rider seemed to experience, the full-suspension on an XC bike might not work as the manufacturer intended with the seat too far back (or too far forward).

    One final thought, when I see folks with pains/aches caused by fit, one common problem is having two or three bikes but each of them are set-up very different. For those folks, I usually try to set-up all of their bikes the same, with seat and handle bar being measured and set in relation to the bottom bracket (and with crank arm length the same). Even with a road bike and an XC mtn bike, I try to set it them both the same in relation to the bottome bracket. Sometimes, I even recommend one pair of shoes, one type of pedal and one type of seat for all of the bikes--to eliminate differences there. For XC mtn riders, they usually don't mind a mtn pedal on their road bike. Once we get all their bikes fitting the same, then often that alone solves the aches/pains, but if not, we can pinpoint the fit problem and address the fit problem on all of the bikes.

  14. #14
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    re: Plumb bob....so you hang the plumb while you are holding still on the bike.....even though when you're pedaling (especially mountain biking!) you are constantly moving around, changing your position and dynamically interacting with your bike. So, how does a static fit work? I thought they worked, I have spent several hundred dollars trying to get a static (a.k.a. Plumb bob) fit, but no one (including the very "reputable bike fitters") has been able to figure it out for me.

    One dynamic fit with Wobble-naught this past year and all my problems have been solved. I was so impressed by the solution that my husband and I even got certified as a dealer. This is not a sales pitch, as I'll bet very few to none of you are even local to us, but I'm just posting this as another happy customer. I'd highly recommend checking out the Wobble-naught site because while times are changing, bike fit has too.

    One other thing---by only looking at one piece of the fit (i.e. fore/aft saddle position), you are missing the whole idea. Think of the body and its relationship to the bike more wholistically, and dynamically. Good luck!
    Last edited by namrita; 11-28-2006 at 08:54 PM.
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  15. #15
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    dynamic fit - yes!

    Well, I directly answered the original post about plumb bob, but I also agree with the last person to post that dynamic fit is best -- but static measurements are a starting point, in most any system. I developed a system which is very similar (but a bit less techy) to wobblenaught, using video analysis of the person while pedaling and placing markers on the body for reference. Pruitt also does a similar dynamic fit, but a bit more high tech than most (with special infrared video capture cameras). Another thumbs-up for dynamic fitting (i.e. fitting reviewed while pedaling).

  16. #16
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    Couple of people might jump on me for this, but the whole knee-over-pedal plumbline thing is baloney. It's no more than a very general rule of thumb to get you somewhere a reasonable fit. There's nothing behind except that... well.... we've all been using it for eons. Keith Bontrager has a wonderful rant on it somewhere (Google is your friend ;-) )

    In the end it comes down to three measurments:

    1. The distance from your seat's 'sweet spot' to your cranks' center.
    2. The distance from your seat's 'sweet spot' to the center of your handlebar.
    3. The angle between lines 1 and 2.

    #1 determines how far your leg compresses and extends. #2 determines largely how your upper body is extended over the bike, and #3 affects how your lower back and pelvis are angled. All have a significant effect on comfort and power output. The plumbline makes no difference.

    On a mountainbike weight distribution and stem length play a significant role in handling, so that's an extra consideration to make. On my 'XC only' bike I can get by with a long (130 mm) stem and zero setback post. My whole position on the bike is relatively weight-forward and my knee is ahead of the pedal spindle. On my marathon bike, a bike where I might actually have to descend for more than 10 seconds, I have a 120 mm stem and a setback post. My kneecap is about 1.5 cm behind the pedal spindle. This said, measurements 1, 2 and 3 are exactly the same, so aside from the difference in weight distribution my position on both bikes is the same.

    Wether or not you need a seatpost is a question of weight distribution, and how top tube length, stem length and seattube angle influence 1, 2 and 3. If you think you need to unload the front end a bit by riding with a shorter stem, you will probably need a setback post. If your bike has a very steep seat angle, you will probably need a setback post as well.

    I may be pointing out the obvious here, but if you change the fore-aft position of your saddle, there's a slight change in the effective distance from sweet spot to crank center - so you'll have to change saddle height.

  17. #17
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    Great thread

    I've done quite a bit of research in to this because I'd had all sorts of knee/back/hamstring/calf issues.

    The basic answer is that location of your knee in relation to the BB should be entirely dependent on your anatomic makeup and your flexability, (if you're interested in efficiency that is...)

    What you should be aiming for is to make sure that your quads, your hammies, and your gluts are all sharing the workload. If the saddle is too far forward, then you'll 'blow up' your quads, if your saddle is too far back then you'll 'blow up' your hammie/gluts.

    To achieve this position I'm 2cm behind the BB.

    One expert here in Australia also has the opinion that the saddle fore/aft position should allow the pelvis to be stable, so that your hands/arms/upper body doesn't need to work unnecessarily hard, and so that you have a solid base to push on the pedals from. Once again, this will be different for each person.

    I highly recommend spending to money to have an assessment done by a bike fit 'expert'. I was fitted by an expert, and my soft tissue issues slowly went away.

    Do a google search for Steve Hogg..you'll come up with plenty usefult info (particularly from www.cyclingnews.com)

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