Singlespeed & Fixed Gear - Crank Clearance

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newleefixed
10-02-08, 06:32 PM
So I am in the process of building up my first fixed gear. The 70's raleigh frame that I am building up is designed for 27 inch tires. It seems to me that 27's are outdated and with 700c wheels you have much more options. What are the disadvantages to switching a frame designed for 27's to 700c. So far the only thing that I have found is crank clearance. Is there a measurement that I should try to avoid going under.(end of crank arm to the ground)
Thanks for any advice

operator
10-02-08, 07:36 PM
It'll be 4mm lower with 700c wheels. You won't notice a difference. Tire size alone can mask that size difference. Since you're converting a road frame you should probably run 165mm cranks if you're concerned about crank clearance and run low profile pedals.

In practice, it doesn't make too much of a difference unless you're going to one end of the extreme in terms of crank length/tire size when cornering.

You learn how to deal with it.
noriel
10-02-08, 09:04 PM
I did the same, and ran 165mm cranks. The only problem will be the lower bb height and if you're running brakes, you'll have to get some that have longer arms so your pads can actually hit the rims. Check your chainline, too. Your hubs and ears will thank you.

bbattle
10-03-08, 08:01 AM
Which Raleigh frame? Quite a few frames from the 70's had clearance for fenders and wide tires and used what we now call long reach brakes. I built up a Raleigh Sprite(same frame as the Record) and even though I used 27" rims (sun cr-18, very shiny) I still needed the Tektro R556 long reach brakes.

sun rims with Formula hub, shimano 108-109mm bottom bracket. We simply retapped the bottom bracket to accept the Shimano bb. Sugino RD 165mm cranks. No problems with pedal strike so far but I don't hammer with this bike.

http://gallery.mac.com/bbattle/100187/100_1125/web.jpg
http://gallery.mac.com/bbattle/100187/P1010030/web.jpg
http://gallery.mac.com/bbattle/100187/P1010031/web.jpg
newleefixed
10-03-08, 10:56 AM
It's a 79 grand prix, I think I am going to go with 700c wheels and just get a little larger tire and 165 cranks and hopefully I should be fine. Ya I have a long reach brake already so I will put that top use.
Thanks for the advice
fivehoursfree
10-03-08, 11:19 AM
I thought this was going to be about someone selling cranks at 60% off!!