Q&A

The correct measure of a frame

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Parent Category: Q&A

Category: Q&A Biomechanic and Training

Published on Friday, 03 September 2010 08:22

Written by Luca Salvatelli

 Dear Editor,

is there a general formula you use for determining frame size. For example, in my case I'm 175cm with a leg length of 81cm. With those measurements, can you recommend a frame size or maybe a min/max size range? Your advice is always appreciated.

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There are many formulas to determine the size of a frame, but all indicate an approximate value, because they can not take into account a number of factors, such as muscle and joint elasticity, any physical ailments, attitudes postural asymmetry and other factors related to the morphology of the athlete. That is always good to find the right position on the saddle after a careful analysis of the dynamic cycling athlete. In calculating the extent of the frame is good as a reference height of the horse, is the distance between the ends of the pubic bone and the plantar plate. This measure, according to Bernard Hinault, found standing with his back against the wall, to be multiplied by 0.65 and get as far as the frame, measured from the center of the bottom bracket tube intersection between vertical and horizontal. This measure refers to the frame with traditional geometry, while the sloping frame you should refer to the same theoretical measures, which are always specified by the manufacturer. Bernard Hinault was theorized, based on their experience, these measures:

Horse Height in cm - Size frame in cm
72/75 - 47/49
75/78 - 49/51
79/82 - 51/53
83/86 - 54/56
87/90 - 57/59
91/94 - 59/61

All these indications refer to a frame with traditional geometry and length of tube equal to the vertical pipe.
The relationship between the length of the legs (horse) and the bust (measure the distance the horse from the beginning of the neck) shows us the formation of the athlete.
We distinguish between:
short lines <1.32
normal lines = 1.32
long lines > 1.32

Subjects short lines take frames with slightly shorter top tube seat tube, while long lines must adopt a long-limbed tube slightly longer than the vertical, in reference to the table shown above.

Other authors prefer to multiply the height of the horse to 0.66 for road bike and 0.59 for bike Mtb

Still others have made this table provides additional data.

Height in cm - Horse in cm - Road Frame Size - MTB Frame Size
152/160 - 68/73 - 48
161/162 - 74 - 48
163/164 - 75 - 50 - 41
165/166 - 76 - 52 - 41
167/168 - 77 - 52 - 41
169/170 - 79 - 53 - 44
171/174 - 81 - 53 - 44
175/178 - 82 - 54 - 46
179/180 - 84 - 54 - 50
181/182 - 86 - 56 - 50
183/186 - 88 - 56 - 52
187/188 - 90 - 58 - 52
189/192 - 91 - 60 - 55
192/200 - 94 - 62 - 55

My advice is to refer to the table for Bernard Hinault and its coefficient of 0.65 calculated. Starting from that value can then analyze whether to adopt a frame just slightly larger or smaller, depending on your physique and needs.