# 52t front crank?



## Andrew_Culture (26 Jan 2013)

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.


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## Andrew_Culture (26 Jan 2013)

Here's the crank I've been told is obsolete.







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


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## derrick (26 Jan 2013)

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.


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## HovR (26 Jan 2013)

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.


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## Cycleops (26 Jan 2013)

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.


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## Andrew_Culture (26 Jan 2013)

HovR said:


> 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!


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## Andrew_Culture (26 Jan 2013)

Now to figure out what bottom bracket fixing I have


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## jim55 (26 Jan 2013)

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


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## Old Plodder (26 Jan 2013)

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).


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## Andrew_Culture (26 Jan 2013)

fatmac said:


> 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.


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## SportMonkey (26 Jan 2013)

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


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## Poacher (26 Jan 2013)

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!


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## Andrew_Culture (27 Jan 2013)

Poacher said:


> 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


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## Andrew_Culture (27 Jan 2013)

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.


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## SportMonkey (27 Jan 2013)

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.


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## Andrew_Culture (27 Jan 2013)

SportMonkey said:


> 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.



I'd love to see what that looks like.


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## SportMonkey (27 Jan 2013)




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## Old Plodder (27 Jan 2013)

Just filed off the teeth....


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## 4F (29 Jan 2013)

Andrew_Culture said:


> 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.
> 
> ...


 
You need to look in the right place .... Plenty of 48's here http://velosolo.co.uk/shopcrank.html


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## simon.r (29 Jan 2013)

These are decent cranks at an attractive price: http://www.spacycles.co.uk/products.php?plid=m2b0s109p2003

Fit a ring of your choice.


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## totallyfixed (29 Jan 2013)

Those are damn big gears you are all riding there, I would be walking up a lot of hills with that ratio on my bike. You make me feel weak .


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## Andrew_Culture (30 Jan 2013)

4F said:


> You need to look in the right place .... Plenty of 48's here http://velosolo.co.uk/shopcrank.html


 
Oooh, pretty!


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## Andrew_Culture (30 Jan 2013)

simon.r said:


> These are decent cranks at an attractive price: http://www.spacycles.co.uk/products.php?plid=m2b0s109p2003
> 
> Fit a ring of your choice.


 
Ta star!


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## Andrew_Culture (30 Jan 2013)

totallyfixed said:


> Those are damn big gears you are all riding there, I would be walking up a lot of hills with that ratio on my bike. You make me feel weak .


 
I only use the SS for getting to work and a bit of biffing around at lunchtime, and while I wouldn't say Suffolk is as flat as folk think it is, there are almost no hills around where I work


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## Smurfy (31 Jan 2013)

Andrew_Culture said:


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


 
Gear-calculator is by far the best GUI of any of the gear calculators on the web. Just a shame that rpm only goes up to 120!

This is my ratio. Click on 'Show Values' and change to development or speed, then drag the sprocket or chainwheel up or down in size with your mouse. Oh, and make sure to set your own tyre size too.


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## e-rider (1 Feb 2013)

Tests in the 1990s showed that using a larger front chainring was slightly more efficient, than a smaller one (for the same size gear) - also, larger rear sprockets are more tolerant of a chainline that isn't 100% straight.

Two reasons you should stick to a larger front ring and larger sprocket, rather than changing to 42x14 or similar

the downside is that 'going large' means more weight


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## Andrew_Culture (1 Feb 2013)

e-rider said:


> Tests in the 1990s showed that using a larger front chainring was slightly more efficient, than a smaller one (for the same size gear) - also, larger rear sprockets are more tolerant of a chainline that isn't 100% straight.
> 
> Two reasons you should stick to a larger front ring and larger sprocket, rather than changing to 42x14 or similar
> 
> the downside is that 'going large' means more weight


 
Thank you!


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## dan_bo (1 Feb 2013)

Never mind slightly more efficient, bigger gears (= larger turning radius) feel better, are quieter and wear slower.


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## Dave Davenport (1 Feb 2013)

totallyfixed said:


> Those are damn big gears you are all riding there, I would be walking up a lot of hills with that ratio on my bike. You make me feel weak .


That's what I was thinking, 85" is old school TT style gearing. I run 44 x 16 (72"'ish) and I'm on the limit on steep hills.


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## MrGrumpy (2 Feb 2013)

Riding 48 x16 here and I manage, my neighbour over the road is on a 52 x 17 I think?? But he is a wee lightweight! Oh and looking at the pictures in this thread, it would seem my front rings looks as worn as the ones on here lol. I too need new chain ring, rear cog and chain to boot, bike is currently off the road due to also new bearings required for rear wheel but toying with the idea of building a new set of wheels. My fixed was my main commuter and I miss it badly, not that the new acquired Giant SCR 2 is bad, I just love riding fixed!


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## Andrew_Culture (2 Feb 2013)

I really like the setup I have right now so I'm tempted to leave things as they are for now, or at least until the chain starts slipping.


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## SportMonkey (4 Feb 2013)

I run 68", it's a good enough number for most things: 30mph on the flat and decent up Snake Pass.


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## Andrew_Culture (5 Feb 2013)

SportMonkey said:


> I run 68", it's a good enough number for most things: 30mph on the flat and decent up Snake Pass.



Agreed, I cranked it up from nowt to 26.5mph in 10 seconds yesterday, 5 seconds later I had hit 30mph.

There was quite a tailwind though


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## e-rider (5 Feb 2013)

Andrew_Culture said:


> Agreed, I cranked it up from nowt to 26.5mph in 10 seconds yesterday, 5 seconds later I had hit 30mph.
> 
> There was quite a tailwind though


... and a 20% descent!


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## Andrew_Culture (5 Feb 2013)

e-rider said:


> ... and a 20% descent!


 
Cliff face more like


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## Andrew_Culture (10 Mar 2013)

I've got this sorted now. A local CCer sold me a Stronglight crankset and I just ordered some chainring bolts from Charlie The Bikemonger.

Just gotta get my head around switching out the crankset now


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## Andrew_Culture (30 Mar 2013)

Situation resolved, partly due to Scilly Suffolk borking his frame

replacement crank


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