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Fit...Probably been discussed b/4...Cut a newbie some slack.(12 posts)

Fit...Probably been discussed b/4...Cut a newbie some slack.Tele_Pathic
Jul 10, 2002 7:59 AM
Ok, I'm choosing between two good, quality bikes; however, there's a snag. A bike shop I trust said I should buy a 52cm frame. One of the bikes I'm looking at is a 50cm; the other is a 54cm. I know I can adjust the fit with stem lengths and saddle position. But, should I choose the smaller frame, or should I choose the larger frame? OR, should I wait for a 52cm frame because I won't be as comfortable on the 50cm or 54cm frames? Does that 3/4" matter that much? Thanks for your expertise. Once I've ridden for awhile, I promise to add some meaningful discussion to this board, and I'll drop these questions.

I'd have to be telepathic to answer.Spoke Wrench
Jul 10, 2002 8:24 AM
One bike mfg's 52cm frame might match another's 54cm. Top tube lengths, especially on smallish frame sizes, can vary by quite a bit. You didn't say if you're a female gymnist who is interested in triathlons or an older male recovering from a spinal fusion.
A bit more info about my size...Tele_Pathic
Jul 10, 2002 9:05 AM
Thanks for the help so far. Need more input, need more input, need more input. My physical measurements follow: Inseam - 80 cm. or 31.5 in.; Frame size - 52 cm. So, does that help?


PS. My screen name, Tele Pathic, indicates my love for Fender Telecasters; it is also the screen name I use on another forum. It's easier for me to remember one screen name for all the forums I belong to; as a bonus, I never suffer an identity crisis. I know it's not bike related, but hey, I can only keep up with one screen name at a time. Just a short explanation is all this is. Anyone else here play Fender Teles?
except that, as Spoke Wrench, says, one man's 52 is another's 53bill
Jul 10, 2002 10:30 AM
or 54. Here's why -- there are two industry standards on how to measure. Some frames are measured from the center of the BB (bottom bracket) to the center of the top tube, some are measured from the center of the BB to the top of the top tube. Arguably more critical than that measurement is the top tube length itself, but here you need to be careful, too. Depending on the STA (seat tube angle), the effective top tube measurement for a steeper angle seat tube is longer than for a shallower angle frame with nominally the same length top tube. Smaller-sized frames (and 50 or 52 is on the small side) probably vary more than larger-sized frames on the seat tube angle, so you have to pay attention to this.
I'm about your inseam, and I ride a 52 cm center to center bike. It is probably on the small side, but supposedly it was designed to be that way in the Italian racing bike tradition. American makers seem to go a little larger.
A cm or even 2 cm either way is not a terribly big deal, but the difference between a 50 and a 54 (assuming the frames are measured the same; frames are usually measured c-c unless they say c-t) definitely could be.
except that, as Spoke Wrench, says, one man's 52 is another's 53Tele_Pathic
Jul 10, 2002 10:50 AM
Well, I'm looking at Cannondales, which have oversized tubes anyway. So would a 52cm Cannondale be equivalent to some manufacturer's 54cm, or am I heading down a super-highway of "what-if's"?

I agree the difference between between a 50cm and 54cm is great. What about the difference between a 52cm to 50 cm, or a 52cm to a 54cm? In other words: Stuck between a rock and a hard place, is it better to have a frame slightly smaller or slightly larger? Or, am I just "sweating the details", and in reality, any three of these sizes will fit my body well? Again, thanks for the input.
At some point, you do get into too small and too large. But,bill
Jul 10, 2002 11:16 AM
you're asking whether, if you can't be spot on, is it better to be on the small side or on the large side of right, right?
It is somewhat a matter of taste, including how you intend to use the bike and, to some extent, aesthetics. Racers, particularly European racers, seem to go a little smaller. The theory there is that the smaller frame is a little lighter and stiffer. Also, the degree of drop between the saddle and bars comes into play; if you don't have much seatpost showing, maybe you won't be able to get your bars low enough to get the six inches of drop for that extremely aggressive racer's position (you still do see racers with a couple of cm of spacers under the stem or even with the stem reversed, raising the bars a bit more, so, don't get upset if you find 6 in. of drop uncommonly uncomfortable). There is some feeling that, if you have less than 4-5 in of seatpost exposed, your bike doesn't look so much like a racing bike anymore. Probably most people would say that smaller is better.
If you don't want very much drop to your bars, maybe you're just as happy with the larger frame.
I don't, by the way, know how C-dale measures frames. It is a question with an answer; I just don't know it.
you didn't cover all the c-t possibilitiesET
Jul 10, 2002 12:48 PM
c-t of top tube

c-t of seat tube

c-t of seat tube clamp

c-t of a totally fictitious reference

There's even c-c of seat tube clamp; I believe this is still called c-t.
what's your height???C-40
Jul 10, 2002 2:32 PM
We need more than inseam to estimate frame size.

Also, have you measured your inseam correctly? Some folks get timid and don't apply saddle-like pressure to the book or whatever they cram into the crotch and come up short on the measurement.

One of the methods recommended for measuring inseam requires the cyclist to stand against a wall. A large book is placed firmly into the crotch, and held against the wall. Measure the distance from the floor to the top of the book to determine inseam. Cycling shorts and no shoes should be worn when taking these measurements.

I prefer to use a bicycle with a horizontal top tube as the inseam measuring device. I just block up the wheels (equally) with boards, books or magazines, until I get saddle-like crotch pressure when standing over the top tube. The distance from the floor to the top of the top tube will be an accurate inseam measurement.

Measuring the height of the saddle above the top tube tells a lot about the frame's vertical fit. 15-19cm is a good range. I like mine as close to 17cm as possible.
Vital stats...Tele_Pathic
Jul 10, 2002 2:56 PM
Male, 5'8", 167 lbs, 30 years old, PANTS inseam 30", bicycle inseam 31.5". Used to ride in high school, now I'm getting back into it. I was measured at a shop that had a stick mounted horizontally to a spring loaded "shock absorber" that had measurements on it. I stood over the horizontal stick, let it snug up against my nethers, and levelled it with the level. So, I would say it gave a very saddle-like feel. Took my shoes off, btw. The guy had a binder filled with handy formulas for turning those measurements into frame and saddle measurements. He recommended a 52cm. He just happened to have a Cannondale in stock that was 52cm. I rode; I loved it.

I guess my main question is, as another poster put it, would a 50 cm or a 54cm frame size do in a pinch? If I can't find a 52cm bike I like, but I do find a 50cm bike and ae 54cm bike that I like equally well, should I choose the smaller one or the larger one? Or, should I wait for a 52cm frame to turn-up? Or does the difference between a 50cm --> 52cm or a 52cm --> 54cm bike make much of a difference? Thanks.
don't settle for anything but the correct size....C-40
Jul 10, 2002 6:18 PM
At 5'8" tall the 52cm would be the smallest frame that you should ride. A 50cm would be too small. Don't even consider it.

A 54cm C-dale has a standover height of 31.2 inches - obviously too tall if your inseam is 31.5. If you find one in a store, straddle it and see if there is only about a 1/4 to 3/8 inch of standover clearance. If so, it's too tall. Standover clearance should be in the range of 3/4 to 1-3/4 inches. I would ride a 54cm, but I've got at least an inch longer legs.

If you look at brands other than C'dale, that's when you have to be sure how the frame is measured. Generally that's not too tough. If the frame is in the shop, measure it yourself if necessary and compare to the C'dale geometry chart for a 52cm, or post your selection here for an accurate comparison.
Skip the 50cmjtolleson
Jul 10, 2002 7:29 PM
Your specs are almost identical to mine, and I'll tell you that my partner's 50 cm Litespeed feels like munchkin bike. Some of that is the stem, but ultimately you are in 52-53 cm land, which depending on the bike will especially be important for not screwing yourself on bar height (you can jack the saddle up but radically adjusting bar height becomes more complicated).

Knowing c-dale's measuring, I think a 52 probably is in the ball park and he isn't just saying that because he has one in stock.
Id go with the 52, you are my sizeishmael
Jul 10, 2002 9:39 AM
I'm 5'8" with a 32 inch inseam and I've got a 53cm top tube. Ride them around and see what you feel, If the differences are by 2cm increments I'd definately go with the 52 c to c but it depends on the toptube really.

dont worry yourself about adding discussion to this site, questions are as good as anything.