Cranksets

General bike chat that does not fit elsewhere
Gabbo
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Cranksets

Postby Gabbo » Tue Dec 25, 2012 10:33 am

A slightly random topic, but I'd like to further my knowledge on different components of the bike including the drive train. If two cranksets both have 50.34t, but one costs £600 and the other £100.. apart from £500 difference in price, what will be the different in how it performs?

I have the FSA Gossamer bb30 but I do believe my bike deserves better.

Also, does anyone here have a compact crankset? And if so, how does it compare to a double?

Thanks, and Merry Christmas to you all!

cougie
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Re: Cranksets

Postby cougie » Tue Dec 25, 2012 10:47 am

I doubt you'd be able to tell just by riding it.

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smidsy
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Re: Cranksets

Postby smidsy » Tue Dec 25, 2012 10:48 am

Generally with most things cycling the higher up the spec range you go the lighter and stiffer something is.

Chainsets are essentially just a way of transfering drive to the back wheel but as most of your effort is put into driving through the crank it makes sense for the components to offer as much torsion as possible to reduce wasted energy through it being lost in flex of the chainrings or arms or BB.

They are also often made of percieved exotic materials (e.g carbon fibre).
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pinarellokid
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Re: Cranksets

Postby pinarellokid » Tue Dec 25, 2012 12:49 pm

a compact is a 50 top ring teeth count a standard is a 53 tooth count
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Gabbo
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Re: Cranksets

Postby Gabbo » Tue Dec 25, 2012 13:14 pm

So basically a compact just has a smoother transition throughout the gears? Sounds more ideal for hilly routes

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smidsy
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Re: Cranksets

Postby smidsy » Tue Dec 25, 2012 15:29 pm

Gabbo wrote:So basically a compact just has a smoother transition throughout the gears? Sounds more ideal for hilly routes


Not smoother just a compact is generally 50/34 where as a standard double is 53/39 so yes a compact is easier for hills.
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TakeTurns
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Re: Cranksets

Postby TakeTurns » Tue Dec 25, 2012 16:59 pm

If you're a spinner, I wouldn't advise you to choose a 53/39. You won't be able to spin efficiently on gradients above 7-8%.

I run a 53/39, it works for me most of the time, I prefer it for not so steep hills and flats. If I were to be doing long climbs over 10% then a 50/34 for sure.

The more expensive chainset may possibly be stiffer. SRAM Rival chainset is one of the stiffest out there for about £120. I'd say it's the best unless you're a weight weenie. Will get one once my DA wears -which might still be a while :roll:

Gabbo
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Re: Cranksets

Postby Gabbo » Tue Dec 25, 2012 19:01 pm

TakeTurns wrote:If you're a spinner, I wouldn't advise you to choose a 53/39. You won't be able to spin efficiently on gradients above 7-8%.

I run a 53/39, it works for me most of the time, I prefer it for not so steep hills and flats. If I were to be doing long climbs over 10% then a 50/34 for sure.

The more expensive chainset may possibly be stiffer. SRAM Rival chainset is one of the stiffest out there for about £120. I'd say it's the best unless you're a weight weenie. Will get one once my DA wears -which might still be a while :roll:


I started off as a spinner but I prefer the higher gears with a slightly slower cadence nowadays - not sure why!

Question: Why does the chain often slip from the big cog to the small cog without me changing gear? Is the crankset wearing down, or does my deraileur need adjusting? This problem has only occured over the last few rides.

Another question: My cassette and chain look ready to be replaced. They are old'ish, look worn and chain is stubborn when shifting. I currently have a 11-28 cassette but I actually want to know what this means? What difference would an 11-23 make, for example? Is it more compact, and suitable for flatter routes opposed to what I already have?

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Monty Dog
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Re: Cranksets

Postby Monty Dog » Tue Dec 25, 2012 20:11 pm

IME the euphemism about one crank being 'stiffer' than another is purely in the minds of the marketing department - most people don't produce the power to make any perceptible difference.
The only real differences in cranks are weight i.e. lighter, and more durable materials - expensive chainsets use harder alloys with hard anodising which last longer. Likewise, a £500 chainset will use ceramic bearings that cost 3x the price of regular bearings to replace.
In terms of your chain slipping off the chainring, sounds like front mech adjustment.
An 11-23 cassette will give you a lower range of gears - probably more suited to racing and flatter terrain rather than all-round riding.
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TakeTurns
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Re: Cranksets

Postby TakeTurns » Tue Dec 25, 2012 20:14 pm

Gabbo wrote:I started off as a spinner but I prefer the higher gears with a slightly slower cadence nowadays - not sure why!

Question: Why does the chain often slip from the big cog to the small cog without me changing gear? Is the crankset wearing down, or does my deraileur need adjusting? This problem has only occured over the last few rides.

Another question: My cassette and chain look ready to be replaced. They are old'ish, look worn and chain is stubborn when shifting. I currently have a 11-28 cassette but I actually want to know what this means? What difference would an 11-23 make, for example? Is it more compact, and suitable for flatter routes opposed to what I already have?



Spinning is more efficient. I used to do slow cadence for strength training. However, if you want to be efficient, spinning is the way.

The slipping is usually down to poor alignment of front mech, in your case it could also be that your components along with chainrings are worn. If you use a worn chain it will deteriorate the chainrings faster.

11 is the smallest cog on the cassette and 28 is the biggest. These are the teeth count. The smaller the teeth count, the harder it is to pedal. I use a 11-28 and I think it's just right. From what I know, you can go up to 32t. 30t is usually the largest most standard rear mechs can accommodate, so check prior to purchase. If you change from a 11-28 to 11-23, you'll lose about 2 gears (estimate). So the easiest gear you'll have will be the third from the top on your 11-28.

Unless it's for a TT bike, I don't see much point in a 11-23 cassette. You can't use it in a hilly area. It saves a minute amount of weight in comparison to a 11-28

gloomyandy
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Re: Cranksets

Postby gloomyandy » Tue Dec 25, 2012 21:06 pm

One of the advantages of an 11-23 is that the steps between the gears are much more even which if you don't need the lower gears (because you live in a flattish area), can mean that you can ride in just the right gear more of the time rather than one that is just too big or just too small.

Some of the more expensive cranksets may come with slightly more complex shapes to the actual rings (steps on the face or different profiles for the teeth), which may give slightly smoother changes.

You may also find that the new electronic shifters work better with the more expensive cranks. Apparently they work better with very stiff chain rings.

thecycleclinic
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Re: Cranksets

Postby thecycleclinic » Tue Dec 25, 2012 21:36 pm

There is alot of nonsene talk about stiffness. I would like to see anyone bend a square taper steel axle or twist one to any degree that would be noticeable and cause a measurable power loss. If you are running a 24mm or 30mm axled cranks then the ammount of twist will be even less than not perceptable. There is a differnece in lateral stiffness of crank arms though some flex a bit more than others but again I am not convinced about how much energy is actually wasted in flexing crank arms.The main benefit of expensive crank arms is in order of real world imprtance,
1) looks
2) other peoples look at the cranks and think nice
3) weight as even though I like light weight kit it does not make me faster.

Square taper rank + BB are generally the heaviest combination around weighing at least 900g for double. Some combinations will be lighter. The square taper BB's generally last a long time though.

24mm axled cranks are normally in the 630g (for SR11 +BB) to 900g heavier for some of the cheap ones.

30mm axled cranks tend to be 900g or so for the entry level ones but can be less than 600g for the high end stuff.
You choose cassete range based on terrain and what the bike is for. My three geared road bikes have the following gearing:
I ride in south Suffolk where there are rolling hills up to 10% gradient
1) Trek 52/39T 12-21T 9 speed for fast riding
2) Traitor winter bike 53/39T 11-25T
3) Alan 52/44T 13-18T (6 speed) I use this for TT's.
The reason why I use close ratio cassettes is for the 1 tooth jumps between cogs. So close ratio cassette is fine so long as you are not riding in the south downs or peak district or anywhere where proper hills exist.

Shifts on the front are never as smooth as the back and while the more expensive chainsets may shift a bit smoother the cheaper ones still shift almost as well. In the end so long as it shifts quickly it does not really matter how smoothly it does it.

With a MTB mech then you can use a 11-34 or 11-36T cassette if you are running shimano.

Remember a crankset only has to be stiff enough like every other part of your bike. Any extra stiffness above that required minimium is simply wasted.
http://www.thecycleclinic.co.uk -wheel building and other stuff.


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