Why only left hand cranks for sale?

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DPietersen
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Why only left hand cranks for sale?

Postby DPietersen » 14 Jul 2020, 5:46am

Morning all
I was given an Raleigh airlite 2006 and plan to refurbish the bike as a project with son.

The left hand side crank is missing so I thought “easy enough” I will order one online and get a new set of pedals and a nut.
Found an exact match (or so I thought) on ebay.

Anyway...it was delivered yesterday , only for me to find out the square hole should have been dismond shape

Back to ebay, Halfords, and the rest for a pair of cranks. Don't need anything fancy.

Now my problem. Everything In this type of crank is sold as left hand side. I need both left and right. Are these cranks interchangeable? Will it be come another problem when trying to fit the new pedals(as the have opposite thread on?

I cant get my head around this..

Any help/advise appreciated.

Thanks in advance

Dieter
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fausto99
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Re: Why only left hand cranks for sale?

Postby fausto99 » 14 Jul 2020, 8:20am

I've read this post several times and am none the wiser. If you want both left and right, you will get a set that matches....no?

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simonineaston
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Re: Why only left hand cranks for sale?

Postby simonineaston » 14 Jul 2020, 8:33am

I'm a bit puzzled too - just had a quick decco on fleabay and its heaving with second-hand / NOS cranksets with both arms :-) - all sorts, from a tenner upwards.
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Paulatic
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Re: Why only left hand cranks for sale?

Postby Paulatic » 14 Jul 2020, 8:39am

Read it earlier, checked it wasn’t April 1st and thought I’d leave that to the experts to fathom. :D
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rjb
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Re: Why only left hand cranks for sale?

Postby rjb » 14 Jul 2020, 8:47am

When fitting a replacement chainset to a tandem with a crossover drive one has to be aware of getting a chainset with the correct square pattern. But the bonus is that you end up with a redundant left crank. Lots of tandem owners have them available. It's worth asking on the forum if you need one. Check the length required and the square pattern, square or diamond. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin, Raleigh 20, Falcon K2 MTB dropped bar tourer, Longstaff trike conversion on a Falcon corsa. :D

reohn2
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Re: Why only left hand cranks for sale?

Postby reohn2 » 14 Jul 2020, 8:54am

If I were the OP I'd put the left hand crank purchace down to experience and buy a cheap road chainset from Spa(good quality at a reasonable price),Decathlon,Halfords,Ebay or similar.

The answer to why all the left hand cranks for sale is that they may be a forging mistake and are being shifted cheap to unsuspecting buyers,we've had the same problem on the forum in the past.
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RickH
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Re: Why only left hand cranks for sale?

Postby RickH » 14 Jul 2020, 12:18pm

Some manufacturers us the "diamond" orientation for their cranks, some use the "square" orientation. Obviously both cranks have to be the same or they will not sit at 180° to each other.

As it happens, I just realised I still have an left crank floating around off an old MTB that I split up to sell the frame. I've just checked & it is the "diamond" orientation & 170mm long (between the hole centres). If that is any use message me & you can have it.

mattsccm
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Re: Why only left hand cranks for sale?

Postby mattsccm » 14 Jul 2020, 5:06pm

Power meters are sometimes left hand if crank only and single sided. Your original becomes redundant.

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RickH
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Re: Why only left hand cranks for sale?

Postby RickH » 14 Jul 2020, 6:26pm

mattsccm wrote:Power meters are sometimes left hand if crank only and single sided. Your original becomes redundant.

I wouldn't have thought many (any?) would be square taper cranks though.

DPietersen
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Re: Why only left hand cranks for sale?

Postby DPietersen » 14 Jul 2020, 6:44pm

Hi everyone.

Firstly, thank you for all the replies and offers.
Secondly, apologies for the confusion I caused (I did have a giggle at the “April fools day” response)

Its now all become clear.....I don't know what I’m talking about when it comes to chainsets... but I’m getting there. Please be patient.

When I ordered the left crank arm i didn't check for square or diamond shape. Got that now. Pity though, because it exactly the same (patterning on the face) to the right crank arm.. only its square not diamond. Luckily I can return it.

Please see the photo of the right crank arm on the bike as is. To me it didn't seem to be joined on the directly onto the chainrings (via a spider) and that it was separate as the left crank arm. I know now that it has to be joined with chainrings somehow (voodoo magic in this case) but thought I could buy the right crank arm separately (this might still be the case, crank puller on order)
So this is where I got confused thinking that right crank arms come separately, from chainsets. Except for really fancy ones where you can see the spider clearly holding the whole lot together.

I cant seem to find that exact left crank arm in diamond shape so will probably look for a whole chain set to replace.

Like I said, crank puller on order as I’d like to have a good look at what I need to get and not make further unnecessary purchases

Thanks again for all the replies

Im sure I’ll be back here for more advise

Dieter
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mattsccm
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Re: Why only left hand cranks for sale?

Postby mattsccm » 14 Jul 2020, 9:42pm

Not wanting to be rude but thats a pretty cheap chainset there. Ebsy should give a replacement for not a lot new.

drossall
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Re: Why only left hand cranks for sale?

Postby drossall » 14 Jul 2020, 11:51pm

DPietersen wrote:So this is where I got confused thinking that right crank arms come separately, from chainsets. Except for really fancy ones where you can see the spider clearly holding the whole lot together.

I cant seem to find that exact left crank arm in diamond shape so will probably look for a whole chain set to replace.


I think you may have worked it out, but chainsets are made up of left and right cranks, and chainrings. On most chainsets, the rings bolt onto a spider that is part of the right crank. On yours, it looks as though the spider is a separate part, but permanently attached to the crank in manufacture. That's a sign of a cheaper chainset (sorry) for which spares probably aren't available. Unlikely you could get an exact left crank either, but it doesn't matter because there are loads of left cranks around so you could just choose a near match.

On extremely cheap chainsets, the spider and outer ring are both one part. The problem being that, once the ring wears out, you have to buy a complete new right crank and ring (probably a complete chainset in practice).

Most square-taper cranks will fit most square-taper bottom brackets, as long as you don't get one crank diamond and the other square, like you did :D The only other thing to watch out for is that there are actually two tapers, known as ISO and JIS, and you really want the same taper on both BB and cranks. They are similar; the easy way to find out which you have would be to find some kind of product name or information on the cranks or the BB (but you'd have to take the BB out to see the label on it, and that's more tools). Then Google to find out (if you're lucky) which taper that particular product uses.

Brucey
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Re: Why only left hand cranks for sale?

Postby Brucey » 14 Jul 2020, 11:55pm

if you can post a couple more photos of the crank and confirm the length (175mm....?) I might have a suitable LH crank that might match reasonably well.

cheers
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drossall
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Re: Why only left hand cranks for sale?

Postby drossall » 15 Jul 2020, 12:10am

NB length is measured centre-to-centre (i.e. centre of the square/diamond to centre of the pedal hole) - because that measures the distance from the BB spindle to the pedal spindle, which is what matters, after all.

It's often stamped on the backs of the cranks - typically 165, 170 or 175 (mm).

DPietersen
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Re: Why only left hand cranks for sale?

Postby DPietersen » 15 Jul 2020, 11:42am

Here are some photos

Its a Prowheel 170mm

Think it will make nice project for my lad and I
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