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bike sizing 56cm vs 58cm on a Trek(15 posts)

bike sizing 56cm vs 58cm on a TrekSlick21
Dec 13, 2001 4:06 PM

I got on both of these bikes a 56cm and a 58 cm Trek 5200. I believe they run center to top. They both fit, but the 58cm was a bit stretched out, and the 56cm was a bit cramped on the top tube according to the sales person. I didn't get to test ride any of them because of lack of time. Which one should I go for, the sales person inclined towards a 58cm with a shorter stem. What do u recommend?

?56cm vs 58cm on a Trek?Chen2
Dec 13, 2001 4:38 PM
It's impossible to say which is better for you without seeing you on the bike, or at least having all of your body dimensions. Let me offer what I can. The OCLV Treks are measured from center to top of seat tube, which is about 2cm above the top of the top tube. The smaller size will be slightly stiffer and slightly lighter. If the 58 is a bit big for you it might be more comfortable on longer rides, the smaller size might be better for racing. I ride a 56cm 5500 (same frame as 5200). I am 5' 9" tall with 32" inseam, short torso and long arms. I like the fit.
What you need to do is have some experts check you out on both bikes.
Dec 13, 2001 4:40 PM
possibly neither. I used to work in Trek shops and the pro deal was so sweet on those bikes I really wanted to like them. I test rode both extensively and played with the setups but decided neither really felt right for me, that I was in between sizes. I'd try some more bikes before you buy. Getting the right fit is very important.
Been Theregrzy
Dec 13, 2001 4:56 PM
I went with the 56 and regreted it slightly. Eventually I sold the bike - the fit just wasn't working right and I was getting lower back pain from being scrunched up - I should've been on the 58. The 56 was a better deal (5200 vs. 5020?). In any event that's just me.

What you need to do is take MORE time and play around with it. You're talking about a significant amount of money and a lot of time that will be invested in the future - ain't no way you should rush this. You will live with the consequences for a long time and it will cost you if you make a mistake. You need to fell like it's right - at the very least you need to swing a leg over quite a few other bikes as well - maybe you'll fit better on something else, like the previous poster said. if you don't solve the doubts in your mind now they'll only get worse.
Been Theregtx
Dec 13, 2001 5:19 PM
If I recall right you're on a 56cm c-c Serotta--73STA and 56tt--which is the same as my custom bike. Funny that on paper the 56 OCLV seems like it would might work, but it just felt small to me. Also had a slightly steeper STA (73.5 I think) and a general handling feel I just didn't like.

I think Lance is riding a 58 (though in a few photos I've seen I could swear he was on a 56). I think when he was on Motorolla he rode a pretty stock 57cm c-c Merckx, which is my rain bike (has a 57cm tt but slacker STA).

In general, when road bikes come in 2cm increments, people get stuck between sizes. It's even worse with mtbs.

Dec 13, 2001 5:59 PM
The 56 cm OCLV really measures our more like a typical 54 cm frame - not that anything is really that typical. I too felt like the Trek didn't quite handle right, but I think being a bit too large for the frame had a lot to do with it. Obviously it works well enough for The Man. My challenge is that my legs are relatively longish for my torso. My Serotta is actually a 54 x 54, but somehow it fits well. In a perfect world I'd probably be on a 56 CT x 54 TT (maybe 55 TT), but in that perfect world I'd have more $$$. I can ride the Serotta all day, and then some, while the OCLV used to get me around the century mark.

Kinda nice when you go true custom - you get whatever it takes!
geometry analysis....C-40
Dec 14, 2001 9:56 AM
According to the Trek geometry chart the 56 has a 56.1cm TT with a 73.5 degree STA, while the 58 has a 57.1cm TT with a 73 degree STA. If you correct for the difference in STA, the difference in TT length between the two is only about .6cm. Either one could be made to fit the same by adjusting stem length and saddle position by this small amount. The only other major issues are standover clearance and head tube length.

I'd select the frame size that would give adequate standover clearance, without excssive use of steering tube spacers. If the 58 was a stretch, a 10mm shorter stem would more than make up the difference. The longer head tube length will reduce the steering tube spacers required.
It depends...TJeanloz
Dec 13, 2001 6:11 PM
Which size is better for you depends, at least partly, on what kind of riding you plan to do.

For a fit, flexible racer-type, I'd say go smaller.

For a masters age touring rider, I'd say go larger. The larger bike will let you keep the handlebars in a higher position vis-a-vis the seat, and will give a more stable ride.
This is interesting but........KurtVF
Dec 13, 2001 6:36 PM
If 2cm increments are too small, what about the sizing of "compact" frames which come in S,M,and L????
This is interesting but........TJeanloz
Dec 13, 2001 6:50 PM
I personally do not believe that 2cm increments are too large. I think that 4 or 5 sizes could fit the vast majority of people. I think a lot of people (and I know this to be true of myself) can fit well on several different size bikes. We just are so overwhelmed with choices, that we gravitate towards the 'optimum' size, which isn't necessarily the only efficient and comfortable size.
This is interesting but........gtx
Dec 13, 2001 7:08 PM
I think once you've been riding a while you establish a seat position relative to the cranks that works best for you. From there there is a natural place where you'd want your bars to be. Now, using different seatposts or stems you could achieve this same basic position on say the 56 or the 58 OCLV (for example) but probably only one (or neither) will "feel" right when it comes to long rides, fast descents, etc. I think you've got a better chance of finding a good fit with companies that offer bikes in 1cm incriments AND vary geomtry across the board (steeper seat tube angles on smaller sizes, etc.). And some people will require custom. My $02.
real dealTJ
Dec 13, 2001 10:49 PM
Get fitted by the dealer, Trek sizes are off and your better to get a proper measurement and be happy. I have a 58cm Colnago and its fit is awsome, I have a 62cm trek 5900 and its fit is awsome. Trek measures from the top of the seat tube.

So long story short is get measure and you will be happy for a long time.

Good $.02dzrider
Dec 14, 2001 5:52 AM
As I've ridden longer I've become more fussy about how my bikes fit. I measure my seat height from the top of the pedal very carefully. Next the distance from the tip of the saddle to a point above the center of the bottom bracket and then to the back edge of the bars. I first found these dimensions on a 55 cm Vitus 992. I can get them on an old Trek whose size I never knew, a Raleigh 600 frame that I think is a 55cm, a 56 cm Jeff Lyon. I move seat posts up or down a little, slide seats forward or back a bit, and have different length stems and cranks, but eventually get all of them the same. Curiously, the Jeff Lyon feels much more "right" than any of the others.
Do it yourselfKerry Irons
Dec 13, 2001 6:25 PM
Since you gave no information whatsoever, you'll just have to go to a sizing calculator and figure it out for yourself
center to top and all thatET
Dec 13, 2001 8:34 PM
It's dangerous to say just center to top, because there's lot's of ways to define "top". It would be nice if the industry would standardize "top" to mean top of top tube, because then, along with a bike's other published stats, you could figure out, with a HS math formula or two, everything about the bike's geometry you'd ever need to know.

As another poster mentioned, OCLV measures to top of seat tube, or even to somewhere on the clamp. This translates into around a 54.3 c-t of top tube for the size 56, and a bit over 56 c-t for the 58. Let's take the 56 as an example. Most bikes size 54 c-t of tt would have a tt more like 54.5 or 55, whereas the Trek's has a 56 tt. Looked at the other way, most bikes with a 56 tt would have a seat tube c-t of tt of more like 56. So in essence, a Trek top tube is rather long for the corresponding standardized seat tube, or for a given top tube it's seat tube sizes rather small. IMHO, this OCLV sizing is very misleading, and misleads fitwise a lot of Lance wannabes, or simply those who thought they were getting a great-priced carbon bike with guarantee but didn't know much else. The standover height (controversial to mention that on this forum) on a 56 will be quite lower than for another bike with a real 56 c-ttt seat tube, or for that matter one with the same 56 tt, meaning that the handlebars will be lower on the OCLV as well. No big deal if you like a 5 inch drop between seat and handlebar, but possibly a big deal if you like the bars much higher. I've seen in an LBS with my own eyes several cyclists bringing in their OCLVs and asking how they can raise the handlebars. Not that easy to do if they're already at 4 cms of spacers. This is a case where the usually reliable "just size by top tube" rule can get some OCLV purchasers in trouble with the vertical differences.

Many will be able to hack it with at most a minor stem/spacer change. Those who are very flexible, get and keep their backs horizontal, or have proportionately long torsos may prefer OCLV. But it's just possible that neither the 56 nor the 58 will fit properly. Something to keep in mind.