52t front crank?

[Andrew_Culture]

I've never quite gotten my head around ratios, so I need a little help.

My winter hack / commuter / single speed is currently running 52t on the front and 17t on the back 16t in the summer) and the ratio suits me just fine. The 52t front crank is very old and not only has shark finning on the teeth, some of the teeth are so worn that it looks like they've melted.

I can't replace just the chainring because it's an obsolete crank so I figure I'll just replace the crank and the chainring. When I look around the web I see plenty of singlespeed / fixie crank and chainring sets but most seem to be 42t or 44t. So if I got 44t what would I need to change the back to?

Can I buy a standard front crank and then buy a chainring of my choice? Do spacers for front cranks exist?

This is not a pretty bike (but I love it) so I'm fairly open to any suggestions.

 

[Andrew_Culture]

Here's the crank I've been told is obsolete.

There is nothing wrong with the crank as far as I can tell.

 

[derrick]

I am running a 44 main ring with a 14 tooth fixed cog on the back, i woud think you would have to change the rear cog to suit you and your riding style.

 

[HovR]

42x14 is pretty close to your 52x17 ratio, as is 40x13.

Is that the Nervar crank I've seen on one of your bikes before? If so, the BCD (bolt circle diameter) is no longer used, making it very difficult to find replacement chainrings.

 

[Cycleops]

Your crank has a five bolt fixing which should be compatible with a Shimano type 52t chainring which I was looking at recently on the Chainreaction site, unless your bolt spacing is different.

 

[Andrew_Culture]

42x14 is pretty close to your 52x17 ratio, as is 40x13.

Is that the Nervar crank I've seen on one of your bikes before? If so, the BCD (bolt circle diameter) is no longer used, making it very difficult to find replacement chainrings.

Yup, you have keen eyes!

This crank owes me nothing, it was a bin rescue and I've done over a thousand miles on it.

I have a budget of about forty quid so it's time to go shopping!

 

[Andrew_Culture]

Now to figure out what bottom bracket fixing I have

 

[jim55]

go to sheldon browns site ,see what ur gear inches are at present and ,..edit 42*14 is pretty near (as is44*15) its not vastly different ,,im running 44*16 so its a bit lower and its fine for the wee hill ive got on the way home

 

[Old Plodder]

If the crankset is still good, just buy a new ring. Measure from the centre of the chainring bolt to the centre of the BB, & then double it, that is your BCD (bolt circle diameter). It looks like you have a square taper BB, so all you need to know is its overall width, (usually 109mm for compact chainsets). Remember if you buy new cranks, the length is important, (probably 170mm).

 

[Andrew_Culture]

If the crankset is still good, just buy a new ring. Measure from the centre of the chainring bolt to the centre of the BB, & then double it, that is your BCD (bolt circle diameter). It looks like you have a square taper BB, so all you need to know is its overall width, (usually 109mm for compact chainsets). Remember if you buy new cranks, the length is important, (probably 170mm).

Sadly it's an old Nervar crank with a bolt circle diameter that is now obsolete.

 

[SportMonkey]

I'd take the big ring off your normal bike and see if it fits. I bought a crankset for £26 from CRC as it was powerspline, but moved the two rings to my Shimano square tapered crank. Oh, and I have a 44t that doesn't fit my bike that was bought from Mellow Johnny's if you're tempted to alter your full ratio.

[Edit]

I should have googled the crank, the 44t I have is 135/144BCD.

[Edit Edit]
122BCD here: http://hilarystone.com/chainrings122BCD.html

 

[Poacher]

Hi Andrew, as SportMonkey and Hovr alluded, you need to check for certain what your Bolt circle Diameter (BCD) is - it looks like 122mm. SportMonkey's link to Hilary Stone's site is useful, but also keep checking Ebay - e.g. http://www.ebay.co.uk/itm/STRONGLIG...sure_cycling_bikeparts_SR&hash=item5651b0cd59 If all else fails, get a new chainset, and you probably need a new sprocket and chain anyway, judging by the state of that chainring! If you do, you may find you can cover the cost by flogging the old, obsolete cranks! There are plenty of vintage fanatics willing to pay wodgy dosh for outmoded kit like that. Bonne chance!

 

[Andrew_Culture]

If you do, you may find you can cover the cost by flogging the old, obsolete cranks! There are plenty of vintage fanatics willing to pay wodgy dosh for outmoded kit like that. Bonne chance!

Well I like the sound of that

 

[Andrew_Culture]

Thanks as ever for every's help.

I quite like the idea of getting a new crankset but would prefer to get a 'proper' crankset and just put one ring on it. Dedicated singlespeed crank sets (at least on eBay) look kinda weird.

 

[SportMonkey]

I should get a picture of my SS crankset that came on my Trek, it's actually a double 130mm with a chain guard on the outer.