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Bike sizing: Importance of standover height? Top tube?(8 posts)

Bike sizing: Importance of standover height? Top tube?Brian T
Jun 22, 2003 10:35 PM
I recently acquired a newer Bianchi, sized at 54cm. I was assured this was the correct size. I am 5'9'' with a 32in inseam. When standing over the bike, there is little, if any room between the top tube and my parts. I remember reading that there should be at least an inch of space there. After raising the bars and lowering the saddle considerably, I was able to attain a pretty comfortable, albeit relaxed riding position. So, I have this super-aero bike, but I think that it is 1.Wrong Size and 2.Under-utilized because of the super-relaxed position. I got the idea for the relaxed riding position from the Rivendell website, and it seems to be a good idea.
re: Bike sizing: Importance of standover height? Top tube?dawgcatchr
Jun 22, 2003 11:19 PM
I used to have a 55cm Bianchi EV2-I am 5 foot 8 with a 30 inch inseam, 86cm floor to pelvic bone. It fit me great. I would think the same would be true for you-what is the standover height of your frame? If you don't have the geometry in front of you, measure the distance from the floor to the top of the top tube, and compare that to your inseam. 54cm is a pretty standard fit for someone 5 foot 9, maybe even a little bit short, but it doesn't sound like that in your case.
re: Bike sizing: Importance of standover height? Top tube?03Vortex
Jun 23, 2003 4:45 AM
Perhaps you just made an arithmetic error, but if your cycling inseam is 30 in, then 86CM is calculated incorrectly. Perhaps you meant 76 vs. 86.

Standover Height should be roughly 3-5cm less than cycling inseam. Also, I believe Bianchi measures their frames ceneter to top but should check their website to verify. I have same dimensions (5'9" and 32-32.5 in inseam) and I ride a 55 Litespeed measured center to top. My standover is about 3cm less.
I too touch the top-tube when standingcoonass
Jun 23, 2003 5:11 AM
My first decent bike was sized on the 'two-finger distance' and I was never comfortable riding....I then got sized by the Bio-racer method to learn that my proper fit (55cm w/55cm top-tube) was the correct size and I do touch the top-tube when standing and every ride is a ride on a perfectly fitted bike....(IMHO...I believe that the 'two-finger' method was a general rule of thumb for the 'around-the-block' rider....Articles I have read indicate that the height of the seat-post should be about 120cm-130cm (4¾" - 5¼") and the bar set lower....however, this will also depend on your crank length....there is no magic single answer...If your top-tube length is not an issue, and you are comfortable after riding >30 miles, I'd say that your frame is correct....only you can answer that
Just lean the bike overLeroy
Jun 23, 2003 5:30 AM
when you're stopped. If it fits ok otherwise, don't worry about it.
Don't worry about the "inch."djg
Jun 23, 2003 5:40 AM
I don't know if the bike fits you or not. Although there are various sizing formulae out there, and they may work fine for many people, I see them more as starting points for individual adjustments. That said, the crucial issues are whether you can get your saddle in the right place, first, and whether you can THEN get your bars where you want them (both the saddle and bar/stem adjustments have up/down and fore/aft components about which similarly built people can have slightly different preferences) without having to jury-rig strange solutions. Having an inch or three free space under the parts, when you are standing flat-footed, straddling the bike, with the bike perfectly upright, and with your feet fairly close together is, in my mind, of very little benefit, if any. It's not that a bike cannot be too tall. Certainly, something that doesn't allow for the proper saddle position or that's awkward to mount and dismount is a problem, but neither of these sounds like your problem.

Instead of imagining what the somewhat iconoclastic folks at Rivendell would do to fit you to a bike built very differently from the way they build bikes, why don't you go back to the shop and have them help you with the setup. That could include both an initial setup, and then an attempt to tweak things to suit you after you've ridden the bike a while. It's possible that you may have the wrong size, but it's very possible that your bike will be fine if set up properly--you may need a new stem or bars to be happy (or not) but that's a much easier fix than a new bike.
Why did you have to raise the bars?jtolleson
Jun 23, 2003 7:07 AM
That part confused me. Having limited standover is not a big deal, but for a bike that you think is "too tall" I'm surprised you felt a need to raise the bars. But the biggest determining factor should be how is your reach?

Plus, I am 5'7" and have a 31.75" cycling inseam. 32 sounds kind of small for a 5'9" rider. And if that really is your inseam, then you must be very long in the torso and most definitely would NOT have wanted a smaller frame. My guess is you already may need a longer stem.
Not important... I think jtolleson is right...funknuggets
Jun 23, 2003 9:14 AM
This question comes up roughly once every month or month and a half and it always highlights the "rules of thumb" and how they do and don't work. Too many things come into play, how frames are measured, what geometry the bike has, body shape, etc. Everyone always has their opinion. However, one thing you should stop doing immediately is judging frames on their 'size'. With compact sizing, c-t size, c-c size, lah de dah, and all the rules of (2 inches of standover, or at least one fist of seatpost exposed)... can go out the window. The most important measurement, in my mind is top tube length. I have both a 51 Look AND a 54 Fondriest and you know what the difference in TT length is... <1 cm. Both nearly have the exact same TT length due to differences in seat tube angle. Many tell me the 54 is too big... whatever. I can still hammer on either one. Find one that is comfortable and puts you in the right position. Note the tt length and stem length and drop from saddle to hbars, and note crank length. Replicate that from bike to bike and you will be in business. Best of luck.