Big Mag Zinn

Recently I did an ergopower rebuild on a custom bike from Leonard Zinn. As a long time technical writer for Velonews and author of a series of books on bicycle maintenance, Zinn has offered custom bikes for riders, who like the man himself, fall on the tall side of the rider bell-curve.

Zinn 01

This bike is manufactured from welded magnesium alloy, which makes it rather rare. Magnesium’s low density, good strength-to-weight ratio, and vibration characterists make it attractive for building high performance bikes, but it doesn’t lend itself easily to welding. And magnesium has poor corrosion resistance. Few builders dare to use it (Pinarello’s original Dogma model is the highest profile example), but Zinn has building with it for a few years.

Yet the bike’s geometry is even more unique than its frame material. The design is driven by the extraordinary crankset, also a Zinn creation.

Zinn 02

Zinn is about 6 and half feet tall and leggy. In his involvement with a number of studies analyzing rider performance and crank length, he became convinced that taller riders could never achieve their potential with even the longest road cranks on the market. So he set about creating cranks as long as 220mm, far longer than the 175-180mm lengths offered by larger manufacturers.

Zinn 03 crank

The longer cranks put the pedals nearly two inches closer to the ground on a conventional bike, so Zinn designs the bike with a high bottom bracket to restore cornering clearance. From a frame design perspective, this is far more significant than the Specialized putting an 1-1/2” bearing on the fork’s lower headset bearing position.

Really daring stuff, I think, except I’m 5’3” and ride 167.5-170mm cranks on the road. Not for me.



2 Comments

Does the fork have a full-length carbon steerer?  If it does, that is very impressive. 

I respect Zinn’s work regarding the longer crank arms - he’s the reason I went to 180s.  But I found it was harder on my knees, and so went back to 175s.  (I’m 6’4” with a 37’ inseam.)

The fork is made by Alpha Q especially for Zinn, but it is available for purchase through regular Alpha Q distribution channels.  I think it’s called the “Z Pro”.  The carbon steerer is both extra long and a much sturdier carbon layup.  It is noteworthy that the Z Pro, unlike most other carbon steerer forks, does not have a maximum spacer height.

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