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@5'9", 175#s why do I feel comfortable on 56cm Trek 5200?(26 posts)

@5'9", 175#s why do I feel comfortable on 56cm Trek 5200?wasabekid
Nov 20, 2002 7:49 PM
With 33" inseam and using 172.5 cranks, I have since logged a little over 700mi on my new bike without any unusual discomfort than what I have previously experienced in my other bikes (21" Raleigh and an older panasonic). At first LBS "sized" me with a 54cm, after testing I requested if he could try setting up a 56cm. Lo and behold, after test ride it felt more comfortable than the 54cm.

The question is:
1)Do you guys find this unusual? (since I seemed to have broken the "basic rules" of bike fit 101).
2)Do you anticipate any longterm disadvantage in my situation?

I have been an avid reader of this forum and have found a lot of the comments informative if not entertaining.

re: @5'9", 175#s why do I feel comfortable on 56cm Trek 5200?irregardless
Nov 20, 2002 8:00 PM
trek frames are small for their size. I think a 56 may be spot on for you. Contrary to what you say, I bet you haven't broken any rules of bike fit.
Nov 20, 2002 10:07 PM
I believe you are correct. If Trek measures to the top of the seat tube, a 56cm would likely be in the neighbourhood of a 54cm bike measure in more standard methods.

This leads me to believe my frame is slightly small for me, and I could probably get something larger next time around, as it is measured like a Trek.
Nov 20, 2002 10:48 PM
Trek measure to the top of the seat color, which is at least 1 cm above the top of a top tube. I 56cm Trek is closer to a 53cm center-to-center frame.
not correctFrith
Nov 21, 2002 7:13 AM
We had this discussion yesterday. Scroll down to the post..."Am i normal?"
TREK only measures that way to account for a slightly different geometry.
The top tube on a 56 trek will be very similar to the top tube on any other 56.
Get it out of your head that TREK measures differently and you should be able to closer to the proper size.
I made a similar mistake... After reading about "TREK sizing" I test rode a 60cm when a 58 is usually what I ride. The 60 was too big and the 58 felt right.
not correctJames OCLV
Nov 21, 2002 9:08 AM
I've had a different experience w/Trek OCLV... I'm 5'7", and my inseam is 31.5. I should be riding a 52cm c-c frame. Based on this, 2 years ago I ordered a 52cm Trek OCLV. I rode this frame for 2 years in complete discomfort, and I couldn't understand why. I broke out the old measuring tape, and lo and behold, my 52cm Trek OCLV measured 50cm c-c! I had about 6.5 inches of seat post sticking out, and the drop to my bars (quill stem, 130mm, max height) was 4 inches. I traded up to a 54cm (52 c-c) w/a 100cm stem (got down to a 2/5" drop) and am much more comfortable.
not correctFrith
Nov 21, 2002 9:26 AM
Most manufacturers sizes are based on a center to top of top tube measurement. Your frame was too small because you applied a center to center sizing requirement. What I'm saying is that if you are normally comfortable on a bike that is Xcm, then the Xcm TREK is the first one you should be looking at.
not correctJames OCLV
Nov 21, 2002 9:48 AM
I gues that's what I was saying... My previous bike (a Diamondback something or other) was a 52cm and fit great. Keeping your line of thought (if you are normally comfortable on a bike that is Xcm, then the Xcm TREK is the first one you should be looking at) I boughta 52cm Trek. WRONG SIZE!!!
not correctlaffeaux
Nov 21, 2002 12:45 PM
I work an shop that sell Treks and Lemonds. We always put people on Lemonds that are one size smaller than Treks. It's not a trick, Trek measures to a different point on the frame. It's pretty straight forward.
Nov 21, 2002 1:23 PM
I've been told that Lemonds are measured c-c, is that correct? If so, there would be a 4cm difference as compared to a Trek OCLV if both bikes are nominal 56cm. Just curious.
I also thought LeMonds were measured ...Allez Rouge
Nov 21, 2002 2:22 PM
... center-to-center, but the current geometry chart on the web site shows center-to-top. However, this is to the top of the top tube itself, NOT to the top of the seat post collar as per Trek.

I don't know if LeMonds have always been measured c-t. As I said I thought it was c-c but perhaps I am thinking of his book, in which the dimensions he gives are, if memory serves, measured c-c.
I also thought LeMonds were measured ...laffeaux
Nov 21, 2002 11:03 PM
They are measured center to center (or were in 2002 and earlier). Because Trek comes in even sizes and Lemond in odd, a Lemond that is measured 3cm smaller than a Trek is about the same size.
They may or may not be changing...Allez Rouge
Nov 22, 2002 5:24 AM
I just took a more leisurely look at the LeMond website. The geometry chart for the 2002 (and older, presumably) models shows the ST measured center-to-center. That's what I thought was the case, and that's what you say. But there's a link that says "Click here to see the 2003 bikes" and the geometry chart for these very clearly shows the ST dimension as being center-to-top.


I have a 2003 LeMond printed catalog, and the geometry chart in it still shows center-to-center.

So, I guess you'll just have to wait until you get some '03 models into your shop and measure the things ...
Nov 22, 2002 9:10 AM
I don't think you can always trust those charts. I know the Trek geometry chart at their site has been wrong for years. I think it's just a drafting error.
Nov 22, 2002 5:12 AM
Trek frames are very close to other brands which use the c-t measurement. Your experience was different because you tried to measure your Trek c-c and compare it with another brand which measured c-c.

Depending on thickness of tubing, you have to keep in mind there is about 1-1.5cm difference between c-t and c-c.

Treks are measured differently, but the size that Trek says it is is VERY CLOSE to most other brands c-t frames!!
Nov 22, 2002 9:18 AM
I understand what you are saying and agree mostly but I think if you were to install identical forks, spacers, and stems in a Trek OCLV and another comparable sized bike measured c-t you would find that the drop from saddle to handlebar would be more on the Trek, maybe by 2cm or more. This needs to be taken into account when shopping Treks.
re: @5'9", 175#s why do I feel comfortable on 56cm Trek 5200?sjomi
Nov 20, 2002 8:26 PM
I am pretty confused by this sizing thing myself while in the search of my new bike. But I'd like to add that I looked at the Trek 5200 and a 5'8.5" and 32.25" inseam I would be on a 56cm also. But if I follow the numbers I would need only a 10cm stem.
re: @5'9", 175#s why do I feel comfortable on 56cm Trek 5200?wasabekid
Nov 20, 2002 8:38 PM
Sorry for the misprint. My inseam measure is suppose to be 32" instead of 33".

re: @5'9", 175#s why do I feel comfortable on 56cm Trek 5200?Allez Rouge
Nov 21, 2002 5:54 AM
Okay, then. Upon reading your initial post my first thought was, "For a 33" inseam, a 56cm measured c-t seems too small." But for a 32" inseam, that should be just about perfect if you use the formula in LeMond's book. He calls for a frame size equal to inseam length x 0.67 which for you works out to 54.46cm measured c-c. So a frame that measures 56cm c-t ought to be within half a cm or so of right on the money.

The other thing you should check is saddle height, measured from the center of the BB up along the angle of the seat tube to the top of the saddle. LeMond's formula here is inseam length x 0.883, or 28.26" / 71.77cm.

Both formulas are, of course, just rules of thumb from one fitting school-of-thought, but they are generally a pretty good starting point for people who are not too oddly put together.
LeMond is a great rider53T
Nov 21, 2002 1:46 PM
but seriously, is there any good reason to be picking a frame based on seat tube length? This is the easiest dimension to change, simply raise or lower the seat. Top tube length, and head tube height are the ones you don't want to miss. If the top tube is too long or too short you will be forced to use stems that are not the optimal length, and even then you could wind up with bad position. If the top of the head tube is too low, you will wind up with too many spacers or back problems, or both. Before sloping top tubes, steep American seat tube angles, and "inovative" geometry, you could approximate the imporatnt measurements by specifying a trivial one, seat tube length. Those days are over. We need to start paying very close attention to top tube length, reach to the bars, drop to the bars and other more important variables.
As I said ...Allez Rouge
Nov 21, 2002 2:16 PM
... they're just rules of thumb, based on two assumptions: first, that the top tube length will be proportioned to the seat tube length according to more or less standard industry practices, and second that the rider is not too unusually proportioned himself. The section of LeMond's book from which I was quoting (from memory: don't have it at hand) is aimed mainly at first-time buyers looking at stock bikes ... and those stock bikes are typically sized by the manufacturers using the seat tube length. It's just a starting point; but then so too would be any other dimension one might choose to specify the size of a standard frame. As you say, there's a lot more to it than just the seat tube length ... but there's also a lot more to it than just the top tube length, or the head tube length, or the seat tube angle, or whatever else.

Understand that I am NOT disagreeing with you at all. The situation is akin to car makers advertising how much horsepower an engine has, when torque would be a much more meaningful figure.
A not-so-minor correction ...Allez Rouge
Nov 22, 2002 5:40 AM
The rule-of-thumb formula in LeMond's book calls for the seat tube dimension, measured center-to-center, to be equal to the rider's inseam length x 0.65, not 0.67 as I wrote yesterday. That doesn't seem like much but for a rider with a 32" inseam, the difference would be 1.63cm -- and that's essentially one full frame size change for manufacturers that offer stock frames in 2cm increments.

And while I'm certainly no fit guru, and with all due respect to Greg LeMond and his coaches, IMO that's just too damned small, and probably helps explain why many riders end up on bikes that are undersized. Per this formula I would need a 56cm measured c-c, but I am currently riding a 58cm c-c and if anything it could stand to be one cm larger.

Which is why these things are called rules of thumb. They're starting points, not inviolable magic formulas.
if the bike is comfortable, it is right for you. nm.nonsleepingjon
Nov 20, 2002 11:03 PM
Because it fits youpmf1
Nov 21, 2002 5:43 AM
I'm pretty much exactly your height and inseam and I have 3 56 cm road bikes. That is the size that fits me. Probably the same for you.

172.5 cranks are pretty much standard for everyone.

I find there are a lot of "rules" of fit, but it comes down to what feels comfortable to you. Just because pro bike racers get on the smallest frame they can and are very stretched out doesn't mean that will be the most comfortable set-up for you.
no surprise...C-40
Nov 21, 2002 6:32 AM
The 56cm Trek is really close to a 54cm, measured c-t. For someone with your inseam, it's the smallest size that you should have considered. Treks have fairly long top tubes, which explains the good fit on a frame that's as (vertically) small as you should ride.

I would suspect that you either have a significant amount of head tube spacers or a high rise stem to keep the saddle to bar height difference less than 10cm.
Trek GeometryChen2
Nov 21, 2002 9:54 AM
My 56cm 5500 measures 54cm c-t, 52cm c-c, and has a 56cm TT length. I expect all OCLV models have the same geometry. I don't think there is a "standard" geometry in the industry. I describe the OCLV's as having a low top tube and short steep head tube. I'm not an expert but I think the thing to look out for on an OCLV is the drop from saddle to top tube, this is why I would not buy an OCLV on the small side, and they make them only in even numbered sizes. Consider that Lance is 5' 10" (I think) and rides a 58cm OCLV.