Cycling UK Forum

Am I being thick here, but what is the difference?

I need to order a crank for my lads bike, and I cannot decide if its a square taper or a diamond taper??

Isn't a diamond just a square turned 90 degrees??

45 degrees.
But yeah, I think you'll be fine.
There are even different standards for square taper, but frankly people ride for years on the wrong one.

Careful to get the right taper!

JIS vs ISO - one is longer than the other, but the same angle of taper.

I can never remember which way round, but mixing them one way is ok, and the other is BAD as there won't be enough BB spindle in the crank.

Some help here:-
http://www.sheldonbrown.com/bbtaper.html

Talk about a nightmare job!!

The bike concerned is a junior sized, Decathlon racing bike. It is one of many that belongs to my club and are "loaned" out for the kids to try there hand at the sport before they commit.

However, the last person to have it clearly did not look after it, or should I say that the last adult who was in charge of it, did not look after it.

The left hand crank has come loose and rather than say something and get it fixed they have continued to allow the child to ride it. Consequently there is no square (or is it a diamond?) shape left in the crank arm!

Decathlon no longer make the bike and subsequent models now have 170mm cranks, as opposed to the 165mm that are currently fitted.

To make matters worse, I have no idea what groupset is fitted as nearly all the components are marked with the Decathlon logo. Apart from the front mech, which is marked as Shimano Soro.

My next option if I can source the correct length crank is to replace the whole chainset?

One place to go for cranks in 'all the sizes' and for advice about what will fit is Spa Cycles. Another is St John Street Cycles. If you are fitting a crank on a bike for somebody with shorter legs, you are certainly right to avoid adult lengths of 170mm and even higher.

There's a Sunrace crank which has steel rings, costs about £15 and is available in 160mm length. I've been pleasantly suprised by the quality of Sunrace stuff recently.

thirdcrank wrote:One place to go for cranks in 'all the sizes' and for advice about what will fit is Spa Cycles. Another is St John Street Cycles.

Tried both already sadly with no joy.........

AlanW wrote:

thirdcrank wrote:One place to go for cranks in 'all the sizes' and for advice about what will fit is Spa Cycles. Another is St John Street Cycles.

Tried both already sadly with no joy.........

Yes. I should have checked before I posted.

I see that Spa now only stock TA Cyclotouriste (once available in all sorts of lengths) in 175mm. We could be seeing some bad knees.

Spa advertise Stronglight "Impact" double or triple in 165mm.

http://www.spacycles.co.uk/products.php?plid=m2b0s109p0

From St John St Cycles :

http://www.sjscycles.co.uk/product-Thor ... r-1672.htm

Not cheap, but available in a wide range of sizes. Whether they will be suitable for you though, I don't know.

So this opens a whole new can of worms for me.

I'm building up using a Stronglight 100LX, so i started wondering about whether it's ISO or JIS

So I looked it up on Sheldon who helpfully says that "older Stronglight" is ISO, but just how old is older?

Does anyone know whether my 100LX should use ISO or can I safely use a Shimano (presumably JIS) sealed as I planned?

Stephen

cycleruk wrote:Spa advertise Stronglight "Impact" double or triple in 165mm.

http://www.spacycles.co.uk/products.php?plid=m2b0s109p0

Hmmm.....interesting and rather annoying?

Ok I was only looking for a crank to start of with, but I did also also ask about complete chainsets, and my options? Which still lead me down a blank route with them?

rualexander wrote:From St John St Cycles :

http://www.sjscycles.co.uk/product-Thor ... r-1672.htm

Not cheap, but available in a wide range of sizes. Whether they will be suitable for you though, I don't know.

Apart from this being a for a triple, I have to watch how much I am spending, and this is right on the edge before we have to call time.

Well I think that I 'might' have found what I am looking for, having just trolled through the Shimano Technical Documents web site.

It would seem that I need to source Shimano part number:- Sora Y-1DP 03100 165mm, left hand crank. But do a need a square or diamond taper.

Plus, its a shame that it comes in a polished finish when I was looking for a matt black finish, but hey..........

Now wheres that tin of black spray paint..