Confusion over frame sizing.. 5' 10.5" and I need a 58cm?
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  1. #1

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    Confusion over frame sizing.. 5' 10.5" and I need a 58cm?

    Hi.. Im about 5' 10.5"
    My real inseam is 32" or just a hair shorter..

    I have a 56cm frame now and have been doing a lot of reading on proper seat adjustment. Ive always had a little trouble on the hills and really am beginning to wonder if I need a larger frame. On my current bike, I have a recessed seatpost but have to I have the seat pushed pretty far back and my knee still does not line up with the pedal axle.. seems I need to push the seat back further but there is not much room.

    Reach on bike seems comfortable, but I'm definitely not in a racing position. I have a 110cm stem on there. Probably could go longer.

    Anyway, here is my point of confusion. I have an inseam of 32" (about 81cm), but all of the 58cm bikes I look at have a 81cm or sometimes higher standover.. Seems like it would be too big?

    Think I should look at the 58cm frame, or is the knee over axle think not always accurate?

  2. #2
    RoadBikeReview Member
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    I have a 32" inseam, and ride a 56". Previous bike was a 55". Have you gotten measured at a bike shop?

  3. #3

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    long femurs?

  4. #4
    If I only knew...
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    Knee over the pedal spindle means nothing, you shouldn't get hung up on it. Check out cyclingnews.com, in their fitness Q and A section there is some really useful info on positioning.

  5. #5
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    I am almost exactly the same size you are, and it is tough to tell, my current bike is almost too small at 56cm but a lot of 58's are too big... agrivating

  6. #6
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    I am a butthair or two over 6'0" (some would argue Iím 6'1"), my inseam is 34", and I have ridden both 56cm and 58cm frames (for long periods of time). I would wager that the 56cm is more appropriate for you, as it was too small for me. My 58cm seems just right, but then again the frame geometry varies just a tad from make/model to other make/model. The best way to find out is to have a real pro shop let you try out the frame sizes, as long as they are dialing you in via a real fitting session. I just sorta went the hit-and-miss method and got lucky.

  7. #7
    I like Chicken
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    My measurements are the same as yours and I ride a 54,55cm.
    Quote Originally Posted by gutfiddle
    Most of the gals we know schedule C sections whether they need them or not nowadays to keep their cooter from gettin torn up but I say you can't hurt them things, they're made of hognose material.

  8. #8
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    try 56cm w fizik arione saddle. Has extra long rails. when deciding new bike why not try a 57cm. bigger bikes usually let seat more back.

  9. #9
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    info..

    You need to read up on bike fitting. First be sure that 32 inches or 81cm is your cycling inseam. That would be fairly short legs for your height.

    Frame size doesn't mean much these days with so many different measuring methods. What determines the true size is the head tube length, with the headset (vertical) and the combination of seat tube angle and top tube length (horizontal).

    If it turns out you have short legs and a long torso, expect to need a 120-130mm stem on a frame that is the proper vertical size.

    FWIW, at 5'-6" tall, I've got an 83cm cycling inseam and ride a 51cm frame, measured center to center or 53cm c-t. You would not need a taller frame to fit your legs, but the TT might be too short.

    www.coloradocyclist.com/bikefit

  10. #10
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    I'm 5'11" and I ride a 56, a 58 could be too big for me. Try getting a set back seat post and also adjusting your cleats. The seat should be in the middle of the rails otherwise you need to get a set back seat post.
    Last edited by lawrence; 04-04-2008 at 05:47 AM.

  11. #11
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    Quote Originally Posted by OldRoadGuy
    My measurements are the same as yours and I ride a 54,55cm.
    The dude gives us his inseam and you say your measurements are the same as his?

    The measurements are a lot more then just inseam.

  12. #12
    RoadBikeReview Member
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    I'm 5'11" w/ a 33" inseam, and ride size 57 frames (center-center). What fits for you depends on a lot of factors. How did you measure your inseam? It's easy to under-measure it. Top tube length is generally the most important measurement, but that also depends on the seat tube angle and whether the TT is sloped or not. Slacker seat tuble angles will make a frame fit effectively shorter, and steeper angles will make one fit longer. Eg, my Merckx frames have 57 TTs but slack seat tube angles (72.5), so they fit about the same across the top as my De Bernardi with a 56 TT and steep STA (74).

    Another factor for many cyclists is head tube length. I can't handle a lot of drop in my handlebar height, so I tend to buy larger frames to get more head tube length. I could easily fit most 56 frames if it weren't for the short head tubes.

    A further complication is that many manufacturers measure or size their frames differently. Eg, some measure their seat-tubes center-top, others center-center. That's why you want to go by top tube length. However, if a frame has a sloping top tube, make sure you go by the effective or horizontal top tube, not the actual.

  13. #13
    zac
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    To the OP there are a couple of good posts here. Don't get hung up on your measurements too much. Go into your LBS (or an LBS that has a good fitter and selection of frames from different manufacturers) with a blank slate and let them assist you in the fitting.

    Be aware that online calculators can be wildly inaccurate, usually due to improper self measurement, and, just as importantly, fit to frames which are using different methodologies of "sizing."

    As was alluded to by C-40, a good fitting is going to depend on the relationship of leg (both femur and shin lengths) and torso and somewhat arm lengths. Two 5'10" people can be completely different; and consequently, the same person can be fit to two different "sized" bikes from two different manufacturers. Also as was said, bike "size" is sort of meaningless today until all manufacturers use a standard method of sizing. Heck some manufacturers use different methods of sizing within their own product lines from model to model.

    For what it is worth I am 182cm (5' 11 3/4") tall with an 84.5cm (33-1/4") inseem I ride 56cm Madones, 58s in more traditional geometries steel & vintage, and a SS Langster.

    zac
    Last edited by zac; 04-04-2008 at 06:27 AM.

  14. #14

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    Is there a measurement/ratio you can do to figure out the long femur? If you do have long femurs, does the knee over pedal thing still apply?

    The longer femur ratio is interesting, because I remember reading that Lemond ration puts riders with longer femurs to low. One thing is certain, that .883 formula does not work for me. With a real 32" inseam, its puts me at 28.3 inches which is way to low for my seat... Its comfortable at about 29 inches.

    Looks like I need to talk a good fitter at a shop

  15. #15
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    saddle heght...

    That old .883 times inseam formula was written many years ago, before clipless pedals. Pedal and shoe stack heights have changed over the years.

    If your saddle height has been set properly, it's about that same as mine (at 5'-6" tall). There can be up to a 2cm difference in saddle height just based on personal preference. Some people pedal more heels-up than others and use a taller saddle height, even with identical leg lengths. I'm never confident in most people's ability to measure inseam (to saddle-like crotch contact in bare feet). I'd rather rely on a good saddle height.

    As a rough starting point for saddle height, adjust the saddle so the foot is horizontal with the leg locked out at the bottom of the stroke. During normal pedaling, a 2-3cm rise of the heel will then produce about a 130 angle between the upper and lower leg. See how you 29 inch setting compares to that standard.

    Based on your saddle height (if accurate) ang not being experienced, you probably wouldn't want a frame as small as my 51cm LOOK 585, but the next larger size with a taller head tube would probably fit just fine. The most common problem for new riders or those who don't put in a lot of miles is usually the need for higher handlebars. A lot of the major brands now offer frames with taller head tubes for those riders.

    The only thing that you may need to accomodate long femurs is more saddle setback, which fortunately increases reach and lessens the need for an overly long stem. You won't find a very large varitaion in seat tube angles for a given frame size, but in your size, there are a few that will have a 73 degree angle. Others will be in the 73.5-74 degree range. One degree makes about a 1cm difference in the seatpost setback at your saddle height.

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