cid499

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?

andrewssohip

clipless, i don't like them, but they'll reduce the risk of pedal strike, especially with 165s

deathhare

no

cid499

Any disadvantages of going to super tiny cranks? Like 150 or 155 range. I"ve seen some on ebay

mander

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.

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?

darsu

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.

mugatu

if you're rocking super wide platforms that is also a problem, for turning, not speed bumps
try narrower pedals

BuddyMike

I had an old Bianchi conversion with 170 cranks. It was an english style frame, so its bottom bracket was low. Buy cheap pedals.

andre nickatina

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...

cid499

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?

mihlbach

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.

cid499

I am indeed running 700c wheels with 23mm tires. I didn't know that a wider tire is also taller.

SkyeC

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.