ccrnnr9

I am wondering if any of you have ever used the Zinn method of road bike fitting found in "Zinn and the art of bicycle maintenance". I have used numerous fit methods and they all seem to show something different. His method seems very logical. It is based off of inseem measurement, arm measurement and torso measurement and a couple easy formulas. The only concern is that it recomended a 58cm top tube for me. I am just under 6ft (probably 5ft 11.75in) with long legs and am currently riding a small 56cm that is very uncomfortable. I rode a 58cm specialized s-works that I like a lot. I am curious to get some feedback on his method. Can arm length make a significant difference in my choice in frame size. I know I have long legs and an average torso but some say I have a long reach and that could necessitate a larger frame. When I went in for my fit I was told if I get a chance to get a slightly larger frame.
~Nick

Proximo

No matter what the fit caculations say, you should buy the bike that feels right to you. The fact that Zinn's formula points you at the top tube length that you say feels good to you should be an obvious sign that his formula works.

For what it's worth, I used the online fit caculator at both zinncycles.com and competitivecyclist.com and both pointed me at a 55cm top tube which fits me perfectly.

stea1thviper

so you have long legs and long arms but a short torso? like a lego man...? hehe just playin. have u considered a longer stem? my upper body extension is slightly longer than average compared to my leg extension, so i got a longer stem and it worked wonders...

Zinn-X

Zinn rulz!

Al f R

As long as you forget the inseam X 2.16 formular for crank lenght cause that sucz.

Lucky07

I'm 6' and had the same expericence with Specialized. 56cm felt too small and very twitchy. 58cm felt just right. But it's really about what's comfortable for you, online calculators or not.

ccrnnr9

I currently ride a 56cm w/ a 120 stem and that feels very cramped. The frame I am getting is a 58cm specialized s-works and zinn suggests a 120 stem. Seems like quite a jump in size, but maybe that is what I need! My bike now feels twitchy. I have a couple different stems so I guess I can swap them around and see what I like.
~Nick

grahny

Zinn's method puts me on a bike that I know is waaaay too big for me. Competitive cyclists comes much closer. The thing I've noticed though is that a size 56 or a size 58 varies COMPLETELY from one manufacturer to another. When looking at cross bikes I rode a trek x01 58 and a cannondale cross 58... the cannondale was waaay too stretched out and uncomfortable.. but the same bike in a 56 fit me fine.

In looking at road bikes, I've gone with a size 56 cervelo soloist team... the top tube is 56.5 cm, which is the same as my "58" trek x01... the 58cm on the trek was related to the seat tube.

So when I hear people say a 56, or a 58 or a 60, I wonder exactly what that measurement is relating to, because it seems to vary depending on who made the bike and what they're considering a 56 or 58, etc...

It's all about test riding!

Hop on Bike

I'm 0.25" shorter than you and every calculator I checked, including Zinn's, recommended a 59cm for me; Last year I tried Specializeds and Treks from 56-60cm and bought the 58cm Roubaix that felt like the best fit. The 56cm felt too small and though the 60cm felt good, I didn't feel like I could control it as well. I recently bought Zinn's maintenance book and have been adjusting my fit based on his calculations; as you probably know, he gives you two factors to calculate stem size - one for a more recreational position and one for more aggressive riding. The first one recommends a 120mm stem and the second a 130mm stem for me. I currently have a 130mm stem that most 'experts' would probably say stretches me out a little too much, but I ride fairly aggressively and like the way it feels.

alanbikehouston

One of the "odd" things about bike fitting is that a larger size can "feel" smaller than a smaller size. Over the past five years, I've had road bikes as small as a size 54, and as large as a size 62. If a road bike has traditional geometry, with a level top bar, the size that fits me best is in the size 59 to size 61 range.

Yet, for a guy my size (5' 9 3/4" tall, with a 32 inch slack's inseam, and a 34 inch leg length, most shops would suggest a size 55 to a size 57. That size range, with the "stock" stem, puts my hands about two or three inches below the top of the saddle. The ultra-low bar position pulls my torso forward, and shifts a lot of weight to my hands, and put my nose down near the front tire.

The result is sore hands, sore wrists, sore neck, sore back. These problems are identical to the problems someone has if they buy a bike with a top tube that is too long, yet they can also occur with a bike where the top tube is shorter than ideal.

With a size 60 bike, I can get the bars up level with the top of the saddle. Having the bars that high also brings the bars back closer to the saddle (bringing the bars up two inches shortens the distance from the saddle to the front of the stem by almost an inch). Having the bars as high as the saddle takes the weight off my hands, and I can ride hours without the slightest soreness.

That size 60 bike has a standover height of about 34 inches. No bike shop would suggest a bike with 34 inch standover to a guy with 34 inch leg length. But, when I'm riding, that size fits me like a glove. And, the only time I stand flat-footed over a bike is when I'm checking standover clearance...in everyday riding standover is not an issue.


If you are thinking of trying a size that is significantly different than what you are used to, borrow a bike in the "new" size from a friend, or even buy a $50 bike at Goodwill or Salvation Army in that size. Ride the new size for a couple of weeks before investing "mega-bucks" into an expensive bike that may not fit you well.

Hambone

Do they make a 5' 4.8" long crank?

"inseam X 2.16 = crank"
___30"_X_2.16 = 64.8" (= 5' 4.8")

ccrnnr9

Thanks for all of the replys. I bought my frame used and did not spend much on it so if worst comes to worst I can find a different one and sell this one. I should have it built up friday night so hopefully I will know pretty soon there after how much I like the fit. One of the things I hate about my current ride is how uncomfy it is to sit in the drops and hammer away or try to descend in that aero position. When I ride like that, my knees hit my elbows. I think I made a big mistake in buying a 56cm frame on that bike. My first bike was a 58 and was much more comfy as far as descending, aero position, drops, etc.
~Nick

Al f R

My apologies for not elaborating. In Oz we use metric measurements. I'm 5' 9 1/2 & my crotch to floor measurement is 83 cm X 2.16 = 179.28. So according to Zinn & his partner in crime Kirby Palm a 180 crank should be the ticket. Well I have been struggling with a 175 crank for 6000ks now with all the tweaking I can think of but to no avail. The pedalling circle was very awkward [to large] to start with but I have become more accustomed to it. The real problem is the bend of the knee just after TDC when power is applied to the down stroke. The bend is too sharp for good power generation.
My quandary is which crank do I need, 170 or 172.5? The way I see it is if I compare 170 to 175 than that is a 10mm [3/8 inch] difference at the top of the stroke.
BTW my first bike had 170s & my current bike came with the 175s. I didn't realise what difference this would make, but I do now. So in MHO Zinns crank length formula still sucz.

Hambone

I don't have the nikd of body awareness to notice a difference like 3/8"

I am always amazed at people with that kind of attention.

I'm one of those lumbering, brutes who after a year and thousands of miles realizes he had two different length cranks on his mountain bike...

I mean I have a friend who is a lumb...

(In my defense, I was wondering why my left hip was always a little sore after a long day on the trail...)