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Discussion Starter · #1 ·
Not really a beginner, trying to get serious on the road thing, but my question might come across as such though. In my giddyness over getting my new stead, I might have overlooked an important item. I realize there are some rule of thumb settings I'll get during fit, and fine tuning things to follow, but initially I didn't think of the cranks. I am little over 5' 6" and run 175's on my mtb's. My new road bike setup is a small (52cm) frame using a compact double crankset with 172.5 arms. Thinking 170's might have been more appropriate for the spin factor and all on the road. Just wondering what the rest of you run between road/dirt (providing you do both :eek: )? Seems like there was a bigger gap between the two in similar threads I've seen.

Thanks in advance for any input.

rr
 

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Yeah, sounds like 170 would be more appropriate for you. However, most of the discussion on here about crank length seems to conclude that a little difference won't matter much. Whether it's 170 or 172.5, you'll get used to it.
 

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I think 5mm less on the road is about standard, but try those out for a while before you decide. Knee problems are a watchout, but your seat is higher on the road and they are shorter than your mtb, so I don't see how you can hurt anything by trying them out. If you have trouble spinning the revs you want, and/or you are doing crits, then spend the bucks to change. You might like them just fine, especially since they are so close to what you are used to.
 

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CarbonFrame
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172.5/175

I have 172.5 on my roadie and 175's on my MTB, no problems. Unless you are a professional racer looking for that one little edge there probably isn't much to be gained by spending the $ to switch cranks.IMHO
 

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i'd say the 170s are what you want for sure on the road bike
(unless you have really long legs compared to your torso)

I'd seriously reconsider using those 175s on your MTB as well.

think of it this way. you set your saddle to have optimal reach at the bottom of the pedal stroke on the road bike. on a mountain bike you drop the saddle a bit for technical manuavering. you dropped the saddle and you moved to a longer crank arm. you knee position is a heck of a lot higher in the 12 O'clock position.

If you were ridding a single speed, i'd say go with the longer crank arms as you'll be standing up hills not spinning up them.

the longer crankarm will be detrimental to your spin. (notice track racers use shorter arms for a faster spin)

its up to you, but i'd put you on 170s around the board.
 

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Resident Curmudgeon
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If it feels all right the way it is...leave it. If it feels awkward to you, change it. I'm a clyde, and have 170's on my commuter & 175's on my race bike. Frankly, I can't tell a significant difference. A little diff maybe, but no biggie.
 

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Discussion Starter · #7 ·
Thanks everyone

I was more or less hindsighting myself on the fact that I hadn't thought (nor was it brought up @ the shop) about length when the bike was being put together. Since I hardly have any miles on them I was wondering if now would be the time to switch (work something out with the shop) if the 170's were really the ticket for my size.

Anyway, I'll start logging some miles. I'd like to say "when the weather gets better", but would probably open myself up to some well deserved keyboard lashings.

Thanks for the tips.

rr
 
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