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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 11-16-08, 10:03 PM   #1
vicoll135
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Bottom Bracket Height and Riding Fixed

Hey everyone,

This is my first post here and i just had a quick question about bottom bracket height, i apologize in advance if i ask anything stupid.

I currently have an old Carlton frame made for 27 inch wheels, but while i was in the process of doing the single speed build i changed my mind and put 700 wheels on instead. In addition, i have 175 cranks on, my main question is would making my bike a fixie now be safe in terms of my pedals hitting the ground?
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Old 11-16-08, 10:06 PM   #2
matthavener
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It really depends on the BB height and how much you lean the bike in turns. The typical approach is obviously shorter cranks...
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Old 11-16-08, 10:23 PM   #3
vicoll135
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It really depends on the BB height and how much you lean the bike in turns. The typical approach is obviously shorter cranks...
Would going with something like a 170 or 165 change the way i ride or anything? i'm guessing that a shorter crank would equal pedaling slightly harder?
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Old 11-16-08, 10:38 PM   #4
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Shorter crank means less leverage which means you need more force. So yep your right.

I'd try out your 175's for a bit, if you run into some pedal strike get 170s or 165s (depending on how dramatic the pedal strike is)

btw it would help if we knew the original bb height on 27's
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Old 11-16-08, 10:39 PM   #5
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I am in just about the same situation. My old Dawes was make for 27s and I run 175mm cranks. They were on it when I bought it. I just take it easy on turns. The only time I could foresee it being a problem is turning uphill - which is the only time I have had pedal strike on my roadbike.

I haven't been riding fixed long, but I haven't hit the pedals yet and don't expect to. Then again, I don't ride very aggressively.
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Old 11-17-08, 12:14 AM   #6
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It's not unknown to have the occasional strike and you do learn to avoid them, so don't go panicking early on, wait until you're got a few hundred miles under your wheels before making a decision to change. Pedal strike needn't be scary either, just don't go throwing your bike into a corner like a full on racer and you'll be right.

Richard
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Old 11-17-08, 12:57 PM   #7
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Go to 170 or 165 cranks.

I ride with 170 cranks on one fixed gear bike and 175 on the other.

I can ride with the 175 cranks because the fixed Mountain Bike on which I use them has an unusually high bottom bracket.

I feel a big difference between the 175's and 170's, which surprised me; and, all around, I prefer the shorter crank for the ease of spinning faster.

On my next bike, I might try 165's.

When one considers the relevance of crank length, it helps to consider the differences between horsepower and torque.

In simplest terms, torque corresponds to horsepower with the TIME element of the equation removed.

At any given instant in time (meaning no time), a longer crank will feel easier to push (or pull) than a shorter crank, but, over time, that impression might change.

And one length relationship does remain constant: the shorter the crank arm the faster the spin.

In any event, a pedal strike can not only ruin your day, it can alter your life.

Look for some 170 or 165 cranks, try clipless pedals (more clearance in turns), or consider a used track frame, like a Bianchi Pista.
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Old 11-17-08, 03:02 PM   #8
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Another thing to consider in crank length is what cranks are they.
I have 175mm Dura Ace track cranks and the arms are about 1/2 tighter to the frame, (lower Q factor) than my 172.5mm Sugino RD's so the pedal strike is actually less of a problem.

I think I still prefer shorter than 175mm but the DA cranks were a good deal on CL so I had to try them. And they look good.
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Old 11-17-08, 09:33 PM   #9
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Originally Posted by Ken Cox View Post
Go to 170 or 165 cranks.

I ride with 170 cranks on one fixed gear bike and 175 on the other.

I can ride with the 175 cranks because the fixed Mountain Bike on which I use them has an unusually high bottom bracket.

I feel a big difference between the 175's and 170's, which surprised me; and, all around, I prefer the shorter crank for the ease of spinning faster.

On my next bike, I might try 165's.

When one considers the relevance of crank length, it helps to consider the differences between horsepower and torque.

In simplest terms, torque corresponds to horsepower with the TIME element of the equation removed.

At any given instant in time (meaning no time), a longer crank will feel easier to push (or pull) than a shorter crank, but, over time, that impression might change.

And one length relationship does remain constant: the shorter the crank arm the faster the spin.

In any event, a pedal strike can not only ruin your day, it can alter your life.

Look for some 170 or 165 cranks, try clipless pedals (more clearance in turns), or consider a used track frame, like a Bianchi Pista.
Thats really helpful thanks, i'll keep in mind the, "a pedal strike can not only ruin your day, it can alter your life," though.
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