Compact v regular cranks

[Eldron]

Ha Ha

 

I am the dude that goes on a Club ride from CT to JHB.

I am the dude that cycles to the Races Amamashova / 94.7 Kemetart.

 

LOL

 

How did you manage to make a 177mm crank though? Did you fill in the hole then drill and retap 0.5mm closer to the centre

 

How is the charity work going? I'm finding companies a bit more open with their wallets this year than the same time last year!

[Zeps]

I'm finding companies a bit more open with their wallets this year than the same time last year!

 

Not ours .... 3% increase in 2 years? earn less than I did then now .....

[SwissVan]

Yeah but the material was presented in a really bland format.

 

Plus there were no ratio and inch arguments.

 

I give those threads a 4 out of 10. Try harder.

 

Eldron's soliloquy for the day:

Ultimately it all comes down to ratio - gearing is measured by dividing the front teeth by the rear. If you can put a little Excel spreadsheet together and work out silly things like what cadence you will be doing using inputs such as speed and gearing then you should be able to decide what cranks/cassettes to buy.

 

If not you're probably better off going to your LBS and asking them for advice.

 

Each to their own, compact crank riders are people too, having fellow riders laugh at you can be solved by intense therapy and you can still look manly with a 34 front ring on your bike.

 

Was wondering if Eldron has practical experience riding with compact cranks in real life or just in excel?

[Guest Frail4Life]

How did you manage to make a 177mm crank though? Did you fill in the hole then drill and retap 0.5mm closer to the centre

 

How is the charity work going? I'm finding companies a bit more open with their wallets this year than the same time last year!

Do you want to buy a raffle ticket?

[The Ouzo]

some of us are like Vtecs and like to rev, others are like turbo diesels and can make power with very little revs

[Eldron]

Was wondering if Eldron has practical experience riding with compact cranks in real life or just in excel?

 

No need.

 

All these gears are the same:

50x25

34x17

52x26

38x19

36x18

 

If I gave you a bike with any of these gears it would feel identical. There is no "magic" - the back wheel turns twice for every turn of the cranks.

 

That said I've ridden track bikes, TT bikes, mtbs, fixies, singles and road bikes with various crank lengths and chain rings/cassette combos - my choice is a 52/39 and a 11-23. I have a 12-25 and 11-25 for when I ride Suikerbosrand or similar.

 

I notice your total contribution to this thread has been a few infoless one liners - if you have anything useful by all means - go ahead....

[Tankman]

Yeah but the material was presented in a really bland format.

 

Plus there were no ratio and inch arguments.

 

I give those threads a 4 out of 10. Try harder.

 

not gonna try - dont need to impress anyone - the other half already saw the Cycling VS Wife thread!

 

The gear ratios were discussed in other threads, just to lazy to use the search function now B)

[Eldron]

Do you want to buy a raffle ticket?

 

 

You got (e)mail!

[Eldron]

not gonna try - dont need to impress anyone - the other half already saw the Cycling VS Wife thread!

 

The gear ratios were discussed in other threads, just to lazy to use the search function now B)

 

One question that still puzzles me is the lever effect. I'm not a mechanical engineer - perhaps someone can help out...

 

Given that crank length and ratio stays the same - does the radius of the chain ring and cassette make an appreciable difference?

 

Eg: would a 50x25 require more force to turn than say a 36x18 because the diameter of the 36x18 is smaller?

 

I can't figure out if you do the lever calc on the crank (in which case the force would be the same regardless of the diameter of the gears as long as the ratio stayed the same). If you do the lever calc on the diameter of the chainrings there might be some science behind compact cranks.

 

My instinct says that chainring diameter makes no difference but I'll happily eat humble pie if a boffin proves me wrong.

 

Wow. This is not entertaining at all.

[eddy]

A question which has been puzzling me:

 

Why did manufacturers have to change the Bolt Circle Diameter ?

 

Would it not be possible to have run both 53 or 50 and 39 or 34 on the same crank set ?

 

Oh, And it seems I have been outed as I chose compact Super Record for my new Tarmac

 

 

.

[linnega]

I'd guess your instinct is right. Effort required is (I imagine) purely a function of the gear inch and crank length.

 

You are all being fairly entertaining, but perhaps the bland answer is that there are many ways to skin a cat. If you want to figure out if you should get a compact or a different cassette, do some calcs using Excel or Sheldon Brown's website and decide whether you want to eliminate big gaps, eliminate duplicate gears or get easier grannies or bigger knee-crunchers. There isn't an answer that fits all, as there numerous potential combinations out there.

 

Personally, I have a compact 50/34 with an 11/25 on the back. These days though I only ride the bike around October and then again for that little 320km charity ride from Little Switzerland in December.

[javadude]

No need.

 

All these gears are the same:

50x25

34x17

52x26

38x19

36x18

 

If I gave you a bike with any of these gears it would feel identical. There is no "magic" - the back wheel turns twice for every turn of the cranks.

 

 

Thought so, you've just gone and proven that you're a poser. So the guy spinning a 50 x 25 next to you is gay and you're a big tough guy with your 52 x 26. You must have quite a fragile ego if the size of your chainrings defines your manhood. Do you by any chance drive a V8 Lumina?

[Zeps]

A question which has been puzzling me:

 

Why did manufacturers have to change the Bolt Circle Diameter ?

 

Would it not be possible to have run both 53 or 50 and 39 or 34 on the same crank set ?

 

 

 

Then you would just buy chainrings and not a whole new crank silly (and that's not what the manufacturers want )

[Zeps]

Thought so, you've just gone and proven that you're a poser. So the guy spinning a 50 x 25 next to is gay and you're a big tough guy with your 52 x 26. You must have quite a fragile ego if the size of your chainrings defines your manhood. Do you by any chance drive a V8 Lumina?

 

Uhhhhmmm you'd be 'spinning' at the same cadence so who would notice

[Minion]

One question that still puzzles me is the lever effect. I'm not a mechanical engineer - perhaps someone can help out...

 

Given that crank length and ratio stays the same - does the radius of the chain ring and cassette make an appreciable difference?

 

Eg: would a 50x25 require more force to turn than say a 36x18 because the diameter of the 36x18 is smaller?

They'd take the same amount of force to turn. All that matters is the ratio of the two.

 

Why did manufacturers have to change the Bolt Circle Diameter ?

 

Would it not be possible to have run both 53 or 50 and 39 or 34 on the same crank set ?

You can run a 53 chainring on a 110mm BCD crank (and you do get them). They tend to be a bit more flexible than a 130mm BCD chainring due to the larger amount of unsupported metal.

 

You cannot run a 34T chainring on a 130mm (or 135mm in Campy's case) BCD crank. The PCD of that chainring is 137mm so the chain rollers would overlap the bolts.

[Eldron]

I'd guess your instinct is right. Effort required is (I imagine) purely a function of the gear inch and crank length.

 

You are all being fairly entertaining, but perhaps the bland answer is that there are many ways to skin a cat. If you want to figure out if you should get a compact or a different cassette, do some calcs using Excel or Sheldon Brown's website and decide whether you want to eliminate big gaps, eliminate duplicate gears or get easier grannies or bigger knee-crunchers. There isn't an answer that fits all, as there numerous potential combinations out there.

 

Personally, I have a compact 50/34 with an 11/25 on the back. These days though I only ride the bike around October and then again for that little 320km charity ride from Little Switzerland in December.

 

 

Lets have some maths fun!

 

A 34x25 huh? Right - so if you climbed using a cadence of 65rpm then you'll be doing 11.26km/hour...

 

Damn - thats higher than I thought. I was hoping it would be single digits so I could mock you senseless. Alas...

 

Much as I poo poo compact users - everything is relative - I ride 175mm cranks where the standard is a 52 big ring. Oh how the 172.5 crowd with their 53's should mock me