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 Post subject: Odd Crank Arm Lengths
PostPosted: Mon Oct 08, 2007 2:13 pm 
Devout Dirtbag

Joined: Wed Aug 15, 2007 10:16 am
Posts: 116
Location: Perth, Western Australia
Hi there,

I'm the process of building up a GT STS DS, buying parts mainly though ebay.

Recently bought a FSA Gamma crankset (modern I know..) and the drive side crank arm is 170mm and the non-drive crank arm 175mm. The lengths are stated on the crank arms and I've double checked with a tape measure and the centre to centre measurements are definitely different.

I've messaged the seller but assume all is above board as they were removed from a new bike.

Any opinions as to whether I'm likely to notice the difference in length when riding? They were a bargain and I'd rather avoid the hassle of returns etc if its likely to be ok. They're just for allround use, bit of casual road riding and trail riding.

Unfortunately I only have half the parts I need so can't install and test ride.

Cheers
Ashes


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 Post subject:
PostPosted: Mon Oct 08, 2007 2:24 pm 
Old School Grand Master

Joined: Wed Jun 29, 2005 11:18 am
Posts: 15806
Location: near cwmcarn
a mate of mine (tinks) did this unknowingly in uni & buggared his knees. dont do it!


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 Post subject:
PostPosted: Mon Oct 08, 2007 2:25 pm 
retrobike rider / Gold Trader
retrobike rider / Gold Trader

Joined: Sat Jul 21, 2007 9:48 am
Posts: 6979
Location: Bristle
i rode a hack with unequal crank lengths. it was nasty.


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 Post subject:
PostPosted: Mon Oct 08, 2007 3:06 pm 
B.o.T.M. Winner / Feature Bike
B.o.T.M. Winner / Feature Bike
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Joined: Tue Dec 13, 2005 3:26 pm
Posts: 6191
Location: Tilting at windmills and shouting at the rain.
It'd be like wearing one of those raised heel 'polio' shoes, nasty!


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 Post subject:
PostPosted: Mon Oct 08, 2007 3:09 pm 
Gold Trader
Gold Trader
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Joined: Sat Jul 29, 2006 11:14 pm
Posts: 3843
Location: Somerset
You will just go round in circles. :lol:


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 Post subject:
PostPosted: Mon Oct 08, 2007 3:14 pm 
King of the DuckBoard
King of the DuckBoard

Joined: Sun Jan 28, 2007 12:30 pm
Posts: 21466
All these measurements sound very small 5mm here 2mm there. But their's good reason why. And if you value you knees return them and get the same length cranks. If 5 mm didn't matter then every body would be doing it. Just picture all those weight weenies out there and how much weight they could save in having 170 cranks :roll:


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 Post subject:
PostPosted: Mon Oct 08, 2007 5:50 pm 
Gold Trader
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Joined: Wed Jun 20, 2007 11:19 pm
Posts: 7006
Location: Odense, Denmark
Actually, I run 170mm cranks BECAUSE of my knees, and my short legs!

Running 175s was not fun... (Well it was the first year or so... but then ceased to be a laughing matter).

It's easier to spin a lower gear with shorter cranks. I'm hysterical about it to be honest. I'd rather run a crap chainset with 170 than something high end in 175.

To add a further 2pennoth. MOST people have a slightly longer right leg than short leg. Look top down onto at a road bike that is ridden by a fanatic and often the saddle will be at a slight angle to the top tube to take account of this. Speedplay even do cleat shims for the same reason.

So odd length cranks CAN be OK if they are right for your legs. But put the long crank on the side that you need the shorter one, and you are BEGGING for trouble.


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 Post subject:
PostPosted: Mon Oct 08, 2007 10:40 pm 
Gold Trader
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Joined: Sat Jul 29, 2006 11:14 pm
Posts: 3843
Location: Somerset
I agree to an extent woth dbmtb's comment.. I also run 170 cranks despitr being 182cm (6'2") as I have ankle problems.

But critically BOTH are 170mm :wink:


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