replacing chainrings - pins and ramps

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Sweep
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Location: London

replacing chainrings - pins and ramps

Post by Sweep »

Bear with me,

I've changed chain rings before but have always used exactly the same part from the same manufacturer, well actually Shimano, so everything straightforward.

When changing the shimano rings i have made efforts to align the new ring the same way as the old one so that the mysteries (to me) of pins and ramps are preserved.

But i may end up using chainrings from other shimano chainsets in future, or even non shimano chainsets. Basically because of shimano's dedication to, er, continuous improvement, or "discontinuing perfectly good stuff".

So to the questions:

@1: Will the pins and ramps for a given number of teeth chainring be comptible across manufacturers?

@2: If, as i suspect they won't be, is it best to ensure that the replacement chain ring has NO ramps or pins?

@ 3:Will i have significant shifting problems with chainrings without these mysterious bits.

@4: Answer to any relevant question I should have been intelligent enough to have asked.

The chainrings will be used on bikes that are 8 or 9 speed.

PS - small point - I have always referred to "bolt circle diameter", BCD, when changing rings, but have recently started to notice the term PCD. I am assuming that this is the same measurement. But what does the "P" stand for?
Sweep
mig
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Joined: 19 Oct 2011, 9:39pm

Re: replacing chainrings - pins and ramps

Post by mig »

'pin'
beardy
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Joined: 23 Feb 2010, 4:10pm

Re: replacing chainrings - pins and ramps

Post by beardy »

1 The ramps and pins on a chainring are for the benefit of that chainring and nothing but the size of the feeder ring below it matters. So makes, models etc dont matter. The rotation of the ring will optimise the effectiveness of the ramps and pins but I find they work well in any position on the crank.

2 You are better off using one with ramps and pins because

3 If you use one without ramps and pins the chain will be resistant to going onto the chainring without a bit of over-shifting. Overshifting can be done easily and habitually with non indexed systems. Much more of a pain with indexed, sometime leading to going all the way to the ring beyond.

4 Double inner rings can be much cheaper than triple middle rings which is why I know 2 & 3.

I thought it was pitch circle diameter. Dont know why, just one of those things that you thought you knew.
goatwarden
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Joined: 20 Nov 2009, 12:03pm
Location: Bristol

Re: replacing chainrings - pins and ramps

Post by goatwarden »

mig wrote:'pin'


Oh no it doesn't!

P.C.D. implies pitch circle diameter; this is the normal engineering term for the diameter of a circle about whose circumference the location of features (in this instance hole centres) are (usually equally) spaced. I often found Americans using BCD instead; it's not really wrong but is more specific to bolt holes.
Keezx
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Joined: 20 Dec 2014, 10:44am
Location: The Netherlands

Re: replacing chainrings - pins and ramps

Post by Keezx »

Sweep wrote:
So to the questions:

@1: Will the pins and ramps for a given number of teeth chainring be comptible across manufacturers?

@2: If, as i suspect they won't be, is it best to ensure that the replacement chain ring has NO ramps or pins?

@ 3:Will i have significant shifting problems with chainrings without these mysterious bits.

@4: Answer to any relevant question I should have been intelligent enough to have asked.

The chainrings will be used on bikes that are 8 or 9 speed.



I ignore everything that's supposed to be not compatible or suboptimal and encounter almost no problems.
Including rings without pins and ramps.
Anything that has the right BCD and teeth I want is used.
For 8 and 9 speed even rings from the 6 speed times work.
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bikes4two
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Joined: 12 Jan 2010, 10:14pm
Location: SE Hampshire, UK

Re: replacing chainrings - pins and ramps

Post by bikes4two »

goatwarden wrote:
mig wrote:'pin'


Oh no it doesn't!

P.C.D. implies pitch circle diameter; this is the normal engineering term for the diameter of a circle about whose circumference the location of features (in this instance hole centres) are (usually equally) spaced. I often found Americans using BCD instead; it's not really wrong but is more specific to bolt holes.


+1 -that's my understanding too as I believe what Sheldon Brown says :D
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Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: replacing chainrings - pins and ramps

Post by Brucey »

most chainrings will work OK but....note also that

- middle and large chainrings have shoulders on them too, on the left side. These help with upshifts and when you downshift, the chain is less likely to sit on top of the smaller ring or even get jammed.

- chainrings (middle and large) also have gates in them. These are to help downshifts.

occasionally you will fit a pinned ring and it will do something weird like the ends of the pins will catch on the chain when running on the neighbouring chainring and the small sprocket. Or that the chainring teeth are microscopically thicker and therefore the chain doesn't shift so well.... Pot luck job really.... there are numerous small variations possible.

cheers
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531colin
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Location: North Yorkshire

Re: replacing chainrings - pins and ramps

Post by 531colin »

My set-up is borderline Luddite, I suppose..... 8 speed with friction-shifting triple on 3 bikes, with one of each 7 and 9 speed.
My chainsets/chainrings are a pretty random collection of pinned rings and rings that pre-date pinning.
I don't try front shifting with any load on, and I can't tell the difference between pinned and non-pinned rings.....I would have to go look at the bikes to tell you.
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Sweep
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Location: London

Re: replacing chainrings - pins and ramps

Post by Sweep »

Thanks for the replies from all so far.

I maybe should have said that I will be using indexing if that is at all relevant - maybe not from some of the replies.
Sweep
pwa
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Re: replacing chainrings - pins and ramps

Post by pwa »

When replacing rings on a (to my eye) aesthetically pleasing Simano Ultegra 9 speed chainset (road triple) I splash out on lovely TA rings, with all the ramps etc you could want, and they work well. Great quality, good looks and the chance to choose ring sizes slightly different to the Shimano ones. Of course the large ring has to have the pin that stops an overshooting chain going down by the crank in the right place, but other than that you just make sure the inside faces in.
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531colin
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Location: North Yorkshire

Re: replacing chainrings - pins and ramps

Post by 531colin »

pwa wrote:When replacing rings on a (to my eye) aesthetically pleasing Simano Ultegra 9 speed chainset (road triple) I splash out on lovely TA rings,......................... the pin that stops an overshooting chain going down by the crank in the right place, but other than that you just make sure the inside faces in.


You have to line up the TA logos on the other rings.....its the law.....otherwise the style police will get you....... :wink:
beardy
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Joined: 23 Feb 2010, 4:10pm

Re: replacing chainrings - pins and ramps

Post by beardy »

Sweep wrote:Thanks for the replies from all so far.

I maybe should have said that I will be using indexing if that is at all relevant - maybe not from some of the replies.


As I said up post with the indexed shifters you dont get enough overshift to make a change without ramps and pins. You can end up riding along with a chain rubbing against the side of the larger ring but not being caught by it until you push the lever a bit more, feeling to avoid the click that will take you either to the ring beyond or to a different state of feathering.

I guess this only matters for the middle ring as the large rings will be designed the same regardless of whether it is a double or triple.

Colin rides a non-indexed system and probably overshifts automatically every time he changes gear, I used to do it as part of my changing action.
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