Cycling UK Forum

Is there a "correct" position for the pins on a chainring, in relation to the cranks? I thought there was, until I replaced a ring with one of a different brand, on which the pins were differently placed relative to the bolt holes.

Do you mean the pin that is intended to stop the chain being trapped bettween the crank and the ring? If so fit it so that is how it is placed.

My impression is that the OP is asking about the pins located around the perimeter of the chainring as shifting aids. On five-bolt chainrings where there are five possible orientations for the chainring relative to the crank, there is often a small mark engraved at one of the mounting bolts that indicates that this should be in line with the crankarm, either hidden behind it or 180 degrees away from it, depending on whether the crank has the fifth bolt hidden behind the crankarm or not. For example, here's the mark I refer to on one of the TA chainrings in my stash: And if the chainring has a longer pin intended to prevent an unshipped chain from getting jammed between the chainring and the back of the crankarm, that should be in line with the crankarm.

Steve wrote: ↑4 Jul 2023, 9:39pm Is there a "correct" position for the pins on a chainring, in relation to the cranks?

Not really. You use the marking on the chainring to get correct orientation.

Note that a chainring can be flipped - they are pretty much symetrical. Some crank arms cover a 'spoke' of the chainring, others do not ... if you see what I mean.

Steve wrote: ↑4 Jul 2023, 9:39pm Is there a "correct" position for the pins on a chainring, in relation to the cranks? I thought there was, until I replaced a ring with one of a different brand, on which the pins were differently placed relative to the bolt holes.

If the number of crank arms is not a divisor of the number of teeth for none of the adjacent rings you work with, then you can change the shifting quality by rotating one of the rings relative to each other. You can, e.g., fix the orientation of the smallest chainring and then work on the orientation of the next one. What you want to arrive at, is that the shifted chain climbs naturally onto the pin and teeth of the next ring. After you are done orienting all chainrings relative to each other, you can carry out their overall rotation relative to the crank to get the outer logo where you want. You can, of course also go from the top, fixing the largest chainring first.

The above is for upshifts. For downshifts, some teeth on the larger ring should be shorter and you can trim with a file if necessary. No more than two are needed and, most likely, your new ring has already some teeth shortened.

I've always assumed that as long as the 'timing' mark on the ring aligns with the crank then all should be well. On the outer ring the anti-jam pin doubles as a timing mark, all should be aligned with the crank arm.

Steve wrote: ↑4 Jul 2023, 9:39pm Is there a "correct" position for the pins on a chainring, in relation to the cranks? I thought there was, until I replaced a ring with one of a different brand, on which the pins were differently placed relative to the bolt holes.

Just one of the reasons it’s not always a good idea to mix different brands of chainring

Yes, I do mean the steel pins which assist the upshift.
The old one is identical to the one in NickJP's photo so also has a neat little arrow indicating where the crank should be.
The new one doesn't:
and I couldn't replicate the relative positions of the pins, so just fitted it any old how. It seems to work fine, though I haven't tested it on the road yet.

When talking to BETD about the Middleburn chainrings that they now make, the guy there told me that they had to change the ramp and pin placings on Middleburn’s designs ‘because they were wrong’. Which makes me think their placing may not be an exact science.

Steve wrote: ↑5 Jul 2023, 9:00am Yes, I do mean the steel pins which assist the upshift.
The old one is identical to the one in NickJP's photo so also has a neat little arrow indicating where the crank should be.
The new one doesn't:

new.jpg

and I couldn't replicate the relative positions of the pins, so just fitted it any old how. It seems to work fine, though I haven't tested it on the road yet.

On SPA website, the SPA branding is opposite the crank

TheBomber wrote: ↑5 Jul 2023, 9:02am When talking to BETD about the Middleburn chainrings that they now make, the guy there told me that they had to change the ramp and pin placings on Middleburn’s designs ‘because they were wrong’. Which makes me think their placing may not be an exact science.

I have in the past ground the things off and didn’t notice any difference
(Why? I was getting the chain carried round after a downshift….in the end that was tooth wear, nothing to do with the pins!

Steve wrote: ↑5 Jul 2023, 9:00am Yes, I do mean the steel pins which assist the upshift.
The old one is identical to the one in NickJP's photo so also has a neat little arrow indicating where the crank should be.
The new one doesn't:

I bet there is a mark somewhere, I've been caught out before, they can be quite subtle

531colin wrote: ↑5 Jul 2023, 9:15am

TheBomber wrote: ↑5 Jul 2023, 9:02am When talking to BETD about the Middleburn chainrings that they now make, the guy there told me that they had to change the ramp and pin placings on Middleburn’s designs ‘because they were wrong’. Which makes me think their placing may not be an exact science.

I have in the past ground the things off and didn’t notice any difference
(Why? I was getting the chain carried round after a downshift….in the end that was tooth wear, nothing to do with the pins!

Ho ho I had the opposite problem here - I thought it was "chain suck" too as the middle ring was quite worn, but once the new ring was on I found it was a loose pin on the big ring that was catching. I knocked it out with a nail punch, which seems to have cured it.

looks like there is a marker on the bottom left of the photo ( about 7 o'clock)

older campagnolo chainrings has a short bolt to secure it into the back of the crank so there was no other orientation. the bolt did tend to work loose though.