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BB too low? pedal bite

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Old 04-21-07 | 01:13 AM
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BB too low? pedal bite

Just finished building up my fixed conversion. It's a 80's Motobecane Super Mirage frame.
Anyway, the BB is way low and I get pedal bite with 170 cranks. Low enough that I scrape going over a speed bump in a straight line.

Aside from going to 165 cranks (which I will be doing), are there any other little things that I can do to increase the BB height?
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Old 04-21-07 | 01:17 AM
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Bikes: IRO Angus, 46/18, promax sb to deep v

clipless, i don't like them, but they'll reduce the risk of pedal strike, especially with 165s
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Old 04-21-07 | 01:24 AM
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Originally Posted by cid499
JAside from going to 165 cranks (which I will be doing), are there any other little things that I can do to increase the BB height?

no
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Old 04-21-07 | 01:35 AM
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Any disadvantages of going to super tiny cranks? Like 150 or 155 range. I"ve seen some on ebay
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Old 04-21-07 | 01:56 AM
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Have you had any other pedal strike issues? I ride with 170s on a road conversion and one of my only two pedal strikes came when going over a speed bump. I think it may be a far more likely place to strike than in a corner. Basically though i have to keep pedal strike on my mind when cornering hard it is an insignificant issue for me.
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Old 04-21-07 | 02:58 AM
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I just went for a ride right now.. going around a bike circle at a very moderate speed, i struck pedal. Then, going EXTREMELY slow on a very slightly off camber and very slightly downhill turn, the pedal struck again. From the ground to the bottom of the BB is only 9 inches, and about 9.75 to the center of the BB spindle.

Anybody else have numbers to compare to?
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Old 04-21-07 | 04:41 AM
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It sounds like you have an unusually low-riding bike. My eighties' roadie has 1/2" more ground clearance than you have (with current 20mm tires), and I thought that was already a bit low for a satisfying fixie. Worry about pedal strike is a frustrating distraction while riding, even if the worry is unfounded.

Fatter tires will probably help a bit.
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Old 04-21-07 | 12:21 PM
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if you're rocking super wide platforms that is also a problem, for turning, not speed bumps
try narrower pedals
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Old 04-21-07 | 02:38 PM
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I had an old Bianchi conversion with 170 cranks. It was an english style frame, so its bottom bracket was low. Buy cheap pedals.
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Old 04-21-07 | 02:43 PM
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There's a few options, if the problem is bad enough it may warrant all of the below:

1) Buy 165 cranks. No brainer.
2) Buy some MKS GR-9 pedals as they give just about the best cornering clearance, or if you want, buy clipless.
3) Fatter tires, like some 27x700's.

That's about it...
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Old 04-21-07 | 05:59 PM
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The pedals I have right now around only about 3 mm wider than the GR-9's, so I don't think I'll be getting those. I have looked into getting a set of 165 cranks and bigger tires.

But have you ever heard of a roadie that was just not suitable for a conversion?
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Old 04-21-07 | 06:20 PM
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Are you running 700c wheels or 27" wheels. The frame was probably intended to be used iwth 27" wheels with 1 1/4" tires or larger. If you've got 700cs with 23mm tires on there, that'll lower you BB considerably.
Whichever is the case, you can gain BB height by mounting larger tires.
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Old 04-21-07 | 06:32 PM
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I am indeed running 700c wheels with 23mm tires. I didn't know that a wider tire is also taller.
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Old 04-21-07 | 07:51 PM
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Originally Posted by cid499
I just went for a ride right now.. going around a bike circle at a very moderate speed, i struck pedal. Then, going EXTREMELY slow on a very slightly off camber and very slightly downhill turn, the pedal struck again. From the ground to the bottom of the BB is only 9 inches, and about 9.75 to the center of the BB spindle.

Anybody else have numbers to compare to?
My bareknuckle has ~13.75" of clearance. Also why I had to get a 50cm frame instead of a 52 like I usually get. Couldn't stand over the damn 52 without selling my balls to science.
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