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Old 02-18-11, 11:23 AM   #1
BG2
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Frame size for classic steel what is right

I was wondering how to know what is the right size frame/bike as these bikes have a diamond frame and not the sloping i can't figure out for these style frames what my perfect size is.

Can anybody throw in some light please.
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Old 02-18-11, 11:29 AM   #2
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First, it must always have a 57cm TT ctc. That way, when you realize that it doesn't fit, you can sell it to me.
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Old 02-18-11, 11:38 AM   #3
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Ah, but can you afford the shipping :-)

Ok now on a serious note how do i determine the correct size for a classic steel bike.

I mean is it determined by how far the seatpost should be out of the frame or is there another trick to know
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Old 02-18-11, 11:43 AM   #4
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Nooo, it should have about a 20/21" TT. Then sell to me!!!

Seriously though, my 80's bike is 52cm. My current bikes, are under 50cm.
The older seatposts weren't 350mm long or longer. Mostly 250 or 2something (under 300). The style of riding back then was more of a "flat back".
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Old 02-18-11, 11:51 AM   #5
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BG2, do you currently own/ride a modern bike with sloping top tube? If so, measure the top tube (from center of seatube to center of steerer) to find out your appropriate top tube length. Then measure your pubic bone height (some call it inseam, but pbh is more accurate term) - Rivendell and other sites have advice on how to do this. Once you have your inseam measurement, find the largest frame that you can stand over comfortably, and that has an appropriate top tube length for you.

Here are a couple helpful reads. They're long, but full of relevant knowledge.
http://www.rivbike.com/article/bike_...g_a_frame_size
http://www.sheldonbrown.com/frame-sizing.html

I'm 6'1", and I fit on frames with a 58-63cm seat tube (measured center of bottom bracket to top of seat tube). Most vintage frames are sized in this manner, abbreviated as "C-T". Any smaller than 58cm and I feel cramped, and any top tube shorter than 56cm and I can't enjoy the ride.

While someone's height is not the sole factor to be taken into account, and you shouldn't base your sizing off of mine or anyone else's, it does help to give some basic perameters for your search.
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Old 02-18-11, 11:52 AM   #6
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People will tell you all kinda things: some will say you need at least about an inch from your junk to the top tube, but not more than 2", some will say you should size such that when you raise the seatpost, you get about a "handful," some will say seat tube is irrelevant as long as you can standover and you want to look mostly at top tube length to determine if you're gonna be overstretched.

Have a look at rivendell's articles here and Sheldon Brown's here.

Another question is what kinda riding you're going to be doing. Do you want a more upright, relaxed riding position for touring or commuting? or a race-y, bent-over position? If you're used to riding most new mountain bikes or hybrids, I think you'll find an upright position more to your liking.
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Old 02-18-11, 11:53 AM   #7
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^ Wow he beat me to it! Same links and everything!
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Old 02-18-11, 11:53 AM   #8
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Generally, you want to be able to stand over the top tube of a vintage bike with around 1 to 1-1/2 inches of clearance between your bits and the tube, but that's by no means a hard and fast rule.

How tall are you?
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Old 02-18-11, 11:54 AM   #9
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There's been a ton written on this, both on the forums and elsewhere. Do a forum search, and check the Rivendell site. They used to have a pretty good section on this and probably still do. Generally speaking, folks used to ride larger frames back in the day, and many who ride vintage bikes still prefer frames on the larger side by today's standards. The rule of thumb used to be "a fistfull of seat post showing". Of course you need to pay attention to top tube length, etc.
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Old 02-18-11, 11:54 AM   #10
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^ Wow he beat me to it! Same links and everything!
hahaha!
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Old 02-18-11, 12:30 PM   #11
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I was making fun earlier, but there was a touch of seriousness there too. Unlike most people apparently, the stated ST length of a vintage bike is almost irrelevant to me. The ST length measurement was never standardized. Sometimes it is measured from center of crank to center of lug, sometimes to the top of the TT, sometimes all the way to the top of the ST. However, I know what the sweet spot is for me in turns of 'reach'. If I'm looking at a bike, I'll always ask the seller what the TT length is ctc. If it's 57-58cm, for me, I know I can get a good reach-feel by putting on the appropriate length stem for the type of riding I want to do.

I used to own, what was sized as a 62cm ST, touring bike. If I stood flat-footed over it, my boys might as well have been playing volleyball with each other. It had a 57cm TT however, so I could ride it fine. I finally did sell it as "too big". I think my "boys" were releaved.
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Old 02-18-11, 12:39 PM   #12
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We need a wiki... and a gizmo like eBay's ask the seller a question answer finder before getting to post a thread
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Old 02-18-11, 03:25 PM   #13
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We need a wiki... and a gizmo like eBay's ask the seller a question answer finder before getting to post a thread
It's called the search function, people just don't know how to use it.
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Old 02-18-11, 04:03 PM   #14
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To get you into the general ballpark, measure your inseam, subtract 11inches and multiply by 2.54.

Example:
inseam = 32"
(32)-11= 21
(21)x(2.54) = 53.3

Bike size is roughly 53cm.
This is the measurement taken along the seat tube from the center of the bottom bracket to
the top of the top tube (assuming the top tube is parallel to the ground).
If the top tube is not parallel, then measure from the bottom bracket to the imaginary line that comes parallel to
the ground from the head tube to the seat tube.

Once again, this is just to get you in the ballpark. I personally believe that the top tube length
is much more important.
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Old 02-18-11, 04:11 PM   #15
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And just to further throw a wrench in things, it depends on when the bike was built, and what it was built for. Back in the '50's, the "fistful" approach was used for everything. By the 80's racing frames were being sized much smaller, with tall seatposts and the beginnings of the huge saddle to bar drops that we're seeing today. Touring bikes, for the most part, were (and are) still being built for "fistful" sizing.

And a lot depends on your preferred handlebar position. If your bar is level with your saddle, or just slightly above or below, "fistful" sizing is pretty much mandatory. On the other hand, if you use a "racier" position, a smaller frame makes more sense.

So there's really not any "one size fits all" formula.

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Old 02-18-11, 04:15 PM   #16
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We used the "elbow on the knee" thing back in the 80's to measure stem length. 'Membah that?
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Old 02-18-11, 04:50 PM   #17
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We used the "elbow on the knee" thing back in the 80's to measure stem length. 'Membah that?
"Elbow on the knee"? Haven't heard that, but there was the "1 cubit" rule: elbow against the nose of the saddle, your fingers should just brush the back of the 'bar. But that was always uncomfortably short for me.

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Old 02-18-11, 04:58 PM   #18
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You get on the drops. Right foot on 3 oclock position. Bend elbow from drop position like you are tucked on a downhill. It should just touch your knee.
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Old 02-18-11, 05:37 PM   #19
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It's called the search function, people just don't know how to use it.
To be fair, search returns a pile of unorganized information. And every time we indulge a generic request like this, it just adds to that morass.
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Old 02-19-11, 12:13 AM   #20
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In November 1983 locally-famed racer Cynthia "Bonanza Jellybean" Marks gave me a copy of The Custom Bicycle authored by Michael J. Kolin and Denise M. de la Rosa. A good deal of the book dealt with sizing/setting up the bike, so if you want a "period correct" (and very comfortable/efficient) fit you might want to purchase a copy.
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Old 02-19-11, 02:32 AM   #21
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Two other resources on selecting a plausibly-correct frame size and fitting the bike to you (these are not the same thing) are:

The Competitive Cyclist pages on fitting: http://www.competitivecyclist.com/za...LCULATOR_INTRO

Bike Fit, an eBook by Dr. Arnie Baker, sold by Road Bike Rider.

Both talk about body measurement and frame sizing, since they are prerequisites for a good fit. Ultimately a given fit can be implemented on a range of frame sizes. Custom builders in many cases start with fit, and select the best frame dimensions to suit the fit you need, as they see it.

Ultimately you won't know it's right without experience and experimentation, but these, or Custom Bicycle will get you a fit that won't injure you. Any change in bike setup needs a few (at least) rides for good evaluation. For me, the best fit is one that I can ride long on, without discomfort.

Last edited by Road Fan; 02-19-11 at 02:36 AM.
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Old 02-20-11, 12:13 AM   #22
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Thanks everybody for al the very useful links and info given.

It's perfectly clear what i should do and how to get there.

Very useful again and many thanks for all of you sharing this important info.
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Old 02-20-11, 07:06 AM   #23
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It's perfectly clear what i should do and how to get there.
Wow, after just 21 messages on the internetz. Clarity and enlightenment are yours!

Now seriously, bike fit has been the source of spirited argument and consternation for decades. Don't think you've got it figured out this quickly. Ride some different bikes, see what feels right over distance. You'll learn what the "BG2 fit" is.
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Old 02-20-11, 07:33 AM   #24
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IT depends on the period. I have a bike from the sixties that's a 60 cm center top, so normally 4/5 cm's too big for me. But since it's a relaxed angle bike with a short TT (55 cm or thereabouts) and a fork with ample rake it fits me perfectly. I have several square build 55/56 italian bikes from the 80's that with great as well, but my most recent bike (2005 principia) is at 55x58 slightly large for me, though rideable with a short stem.
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Old 02-20-11, 09:22 AM   #25
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There is no agreement on fit.
Thus there can be no definitively correct information on the internet.
What one person says, another will vehemently contradict.

Listen to people's opinions, (they are just that), but form your own, from your own riding experience.
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