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Thread: Time Frames Geometry

  1. #21
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    Quote Originally Posted by giordana93 View Post
    especially if we admit that riders of small bikes should get the opportunity to try a position a couple cm behind kops like everybody else? and don't answer "get a custom frame"--that is not the question. and how does one refute cervélo's claims on these slides of the same paper grant cited?


    But KOPS is a red herring... that's the point.


    -g
     

  2. #22
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    Quote Originally Posted by giordana93 View Post
    bingo. it's again what percentage of the population can be "made to fit" on the fewest possible number of offerings

    re: Richard, we get hung up on these angles because manufacturers usually don't include what you framebuilders measure as the frame setback and it's a trial and error process to figure out how the one number (sta) translates into the other (frame setback). I'd love a custom frame and will spring for one one of these days, but I'm still sorting out my contact points--after 30 years, but the last decade has seen a precipitous falling off of annual mileage so I'm second guessing some things I took for granted, starting with seat height which dictates a whole host of others (I've been low but way back, now trying out higher, more forward, yada yada)
    it actually has nothing to do with that. cervelo makes three sizes that are so far out of range as to be virtually unrideable. the thing is, they really believe in their design and their philosophy. if it were just a cost cutting measure, they'd just make the 54, the 56 and the 58 and be done with it.
     

  3. #23
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    Quote Originally Posted by jerk View Post
    frame setback is all about putting the rider in the right place and the wheels in the right place. if you have too much setback in the smaller sizes without making the top tube longer the front center ends up being stupid short....like on a 48cm and 51cm cervelo and the bike rides like shit. likewise if you put too little setback on a big bike like a 61cm top tube without making the top tube stupid shorty you end up with too long a front center and the bike rides like shit.

    for this reason every single person on csc regardless of size, rode 54s, 56s or 58s. the 61, 48 and 51cm frames sucked.

    companies that design bikes based on "fit" are doomed to design bikes that ride like shit. if you're only smart enough as a product manager to take one criteria into account....for god's sake pick front center and trail and make the rest of the bike work within the specifications of the shimano components you're buying by the container load....at least then the chainstays won't be too short or too long and the brakes, cranks and gears'll all be in the right place.

    jerk

    i owe you at least 2 beers for saving me from typing that out.

    -g
     

  4. #24
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    Quote Originally Posted by GrantM View Post
    But KOPS is a red herring... that's the point.


    -g
    agreed, it's just a reference point, that I don't use. but the few times I've bothered to check, I've been behind kops, except on my old Viner whose 75 sta made it impossible to be behind kops. it was fine in the flat lands of New Orleans but just too forward when I went to Ithaca
     

  5. #25
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    Quote Originally Posted by jerk View Post
    frame setback is all about putting the rider in the right place and the wheels in the right place. if you have too much setback in the smaller sizes without making the top tube longer the front center ends up being stupid short....like on a 48cm and 51cm cervelo and the bike rides like shit. likewise if you put too little setback on a big bike like a 61cm top tube without making the top tube stupid shorty you end up with too long a front center and the bike rides like shit.

    for this reason every single person on csc regardless of size, rode 54s, 56s or 58s. the 61, 48 and 51cm frames sucked.



    jerk
    Here are a couple of pictures of some Italians who were totally perplexed at the 48cm Cervelo before them. Dario did a triple take when he measured the front-center. And as someone who has ridden her fair share of 48cm bikes, the Soloist was a turd.
    Attached Images Attached Images
     

  6. #26
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    Quote Originally Posted by giordana93 View Post
    agreed, it's just a reference point, that I don't use. but the few times I've bothered to check, I've been behind kops, except on my old Viner whose 75 sta made it impossible to be behind kops. it was fine in the flat lands of New Orleans but just too forward when I went to Ithaca
    yes, it's a fine reference point for figuring out where you weight is.

    If you're feeling like you're fighting to get further behind the pedals,
    and you're running out of seat rail..... lower your bars. The reason
    your body is sliding back is to close your hip angle, it's not about
    being behind the pedals.

    -g
     

  7. #27
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    Wow, you guys are all 4.5/5 cms back? Are you all Tri-geeks? My saddle ht is 80.5 and my setback is 11cm with a Regal. Okay, I drag my knuckles when I walk, and I eat babies for breakfast, but Eddy set my up years ago and I never strayed from the bible.
     

  8. #28
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    Quote Originally Posted by WFSTEKL View Post
    Wow, you guys are all 4.5/5 cms back? Are you all Tri-geeks? My saddle ht is 80.5 and my setback is 11cm with a Regal. Okay, I drag my knuckles when I walk, and I eat babies for breakfast, but Eddy set my up years ago and I never strayed from the bible.
    I'm about the same size as E-Richie, and our saddles are 12cm lower than yours...
    11 is right in the range for your size. That's why bigger frames should have
    shallower seat tube angles than small ones...

    -g
     

  9. #29
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    I love Alexis.
    shrink, terrorist, poet, president of concerned cyclists for the abolishment of bovine source bicycle parts and head of the disaffected commie dishwashers union.

  10. #30
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    Quote Originally Posted by GrantM View Post
    I'm about the same size as E-Richie, and our saddles are 12cm lower than yours...
    11 is right in the range for your size. That's why bigger frames should have
    shallower seat tube angles than small ones...

    -g
    protractors are the tool of the devil and john schubert atmo.
    lose them. go get a steel rule with millemeters. linear rules.

  11. #31
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    Quote Originally Posted by GrantM View Post
    yes, it's a fine reference point for figuring out where you weight is.

    If you're feeling like you're fighting to get further behind the pedals,
    and you're running out of seat rail..... lower your bars. The reason
    your body is sliding back is to close your hip angle, it's not about
    being behind the pedals.

    -g
    good thought, Grant; actually I think it's because no small frame has enough reach for me. I've got the legs for a 52 (80 cm) but the trunk for a 54 or so--I'm 5'9", and not having the means to buy a bike more than once a decade or so, haven't been able to get beyond the old fit kit / handful of seatpost paradigm that tells me "you're a 52, just put a 12 or 13 on there." and having ridden like that for decades (with reasonable success once upon a time) I'm kind of sean kelly stuck in my "bad but I can still go fast and nothing hurts so why change it?" position (sorry, I'm too lazy to put the required hyphens in that)
     

  12. #32
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    Quote Originally Posted by e-RICHIE View Post
    protractors are the tool of the devil and john schubert atmo.
    lose them. go get a steel rule with millemeters. linear rules.
    i recently made the leap to linear.
    you rock. i have seen the light
     

  13. #33
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    Quote Originally Posted by giordana93 View Post
    good thought, Grant; actually I think it's because no small frame has enough reach for me. I've got the legs for a 52 (80 cm) but the trunk for a 54 or so--I'm 5'9", and not having the means to buy a bike more than once a decade or so, haven't been able to get beyond the old fit kit / handful of seatpost paradigm that tells me "you're a 52, just put a 12 or 13 on there." and having ridden like that for decades (with reasonable success once upon a time) I'm kind of sean kelly stuck in my "bad but I can still go fast and nothing hurts so why change it?" position (sorry, I'm too lazy to put the required hyphens in that)
    we're on the same page.

    a lot of frames are too short, and the current fit 'trends' are shorter and higher
    as the market for road bikes expands into the mainstream.

    I'm of a similar proportion, most stock bikes today are too short, resulting in short
    wheelbases. I shouldn't have to use a zero set back post and a 13cm stem on
    a 51cm frame just to center my weight over a badly designed frame...

    -g
     

  14. #34
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    Quote Originally Posted by GrantM View Post
    we're on the same page.

    a lot of frames are too short, and the current fit 'trends' are shorter and higher
    as the market for road bikes expands into the mainstream.

    I'm of a similar proportion, most stock bikes today are too short, resulting in short
    wheelbases. I shouldn't have to use a zero set back post and a 13cm stem on
    a 51cm frame just to center my weight over a badly designed frame...

    -g
    egg-zactly; and if I size up (this is still conjecture b/c I haven't tried it yet) to get a longer TT, the head tubes start coming up too, so I'd need a track stem to get my normal saddle-to-bar drop. though maybe with an added 2-3 cm of reach, I might want less drop. just gotta bite the bullet and try. easier said than done with the miles I've been able to put in lately.
     

  15. #35
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    Quote Originally Posted by swoop View Post
    4cm on an arione. 71.5 to saddle top. I'm a hobbit with long shins.
    Quote Originally Posted by GrantM View Post
    I'm at 4.5cm back... 68.5 saddle height.

    I'll do 75' on my next frame, so i can slide the seat 5mm further back on the rails
    Quote Originally Posted by giordana93 View Post
    --snip-- I've got the legs for a 52 (80 cm) but the trunk for a 54 or so--I'm 5'9"
    And I'm also 5'-8' w/ 67mm setback on an SLR at 73.5cm to saddle top. My 33" cycling inseam makes me all legs. I've got 1-1/2" more leg than G93 who's 1" taller.

    So now we have two 5'-8" riders and two others maybe an inch either side and quite a variety of proportions. My point is that perhaps there's room in the market for different geometries. And a reason for custom for folks at the extremes. And regardless of fit the Jerk makes the point well that the design must be still rideable.
     

  16. #36
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    to add to the database: seat height at 70.5 (+/- 1) setback @ 4.5-6


    yeah, senors jerk and sachs seem to know somthin about this stuff. I wonder if the numbers for the Time front center make their small frames rideable. I edited my post on page 1 with the Time #'s to include the legend; worth noting that they do give the linear setback # for their frames, not just angles.
     

  17. #37
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    ........and senors Jerk and Sachs will not put you on a shopping cart.
     

  18. #38
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    Quote Originally Posted by Peter B View Post
    And I'm also 5'-8' w/ 67mm setback on an SLR at 73.5cm to saddle top. .
    You can roughly convert every 3 cm's of saddle height change to a 1 cm change in set back
    for any given seat tube angle.

    Someone better at math than me could extend the set back numbers from this frame chart
    to include the seat height.... and then make another chart for saddle lengths for all the
    different models. who's up for that? :)

    -g
    Attached Images Attached Images
     

  19. #39
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    good chart. I suppose it doesn't matter much, but are those c-c or c-t numbers?

    as for the saddle database, there's some guy in France trying to compile the numbers for where the "dip" in the saddle occurs across varying models, since (and he argues rabidly about it) a set back from the nose of the saddle is only half the story. where you sit can vary by a couple cm, so he always talks about the set back to the spot where one sits (creux de selle)
    his site is mecacote.com
     

  20. #40
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    Quote Originally Posted by giordana93 View Post
    egg-zactly; and if I size up (this is still conjecture b/c I haven't tried it yet) to get a longer TT, the head tubes start coming up too, so I'd need a track stem to get my normal saddle-to-bar drop. though maybe with an added 2-3 cm of reach, I might want less drop. just gotta bite the bullet and try. easier said than done with the miles I've been able to put in lately.
    g93;

    I have the same fit issues as you. 5'9", long torso, short legs. I wanted to mention the possibility of having slightly different positions for a road fit, depending on what you're using the bike for.

    I have a radically different cyclocross set-up of course, but up until recently, I was pretty set on a single position for all of my road bikes. It was a written piece that dbrk did a few years back on the Hampsten blog that made me think about adjusting my fit subtly for different road bikes depending upon their use.

    My "home" position is the one Sir Steve of Hampco set up for me on one of his gravel road customs: 70cm saddle ht, 5cm nose behind the BB. This is my most relaxed road position and the bars are about 3.5cm below the saddle, which is moderate for a 51cm frame. I love the ride and the position.

    I have a Merckx MX Leader which I intentionally set-up with a different position: rotated up and forward. It has the saddle higher by 0.5cm and the nose forward by 1cm compared to the Hampsten. Reach is a touch longer, and the bar is 6cm below the saddle. Frame is a 52cm. I also love that ride and position.

    I use the bikes for different reasons and seasons. The Hampsten is great in the winter and on really bad roads. It's great to get behind the BB and roll over gravel. The Merckx uses skinnier tires and gets out on the nicer roads, dry weather (no fenders on the MX Leader) and with fast riding partners. I find the more forward position easier for higher rpm.
     

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