cheap BIN syncros alu cranks

[FMJ]

how many cranks for sale have the orientation pips in the wrong alignment, what does this tell us

You're mistaking shifter ramp pins for orientation pips (?). Seeing as there's 4 ramps+ pins on the 5 bolt middle ring, there is no "right" way to align the pins. As well, it's picking the chain up off a granny with non recessed teeth, so orientation is moot. You made the same comment on the ramp pins of the middle RF ring in my Brodie build thread, which I found odd, but didn't comment on at the time.

The only orientation pin that I can think that you're on about is the pin that sticks out from the outer ring. That one makes a difference, but it's sole purpose is to keep the chain from getting jammed between the crank arm and the chain ring if the chain gets derailed. It has nothing to do with shifting.

 

[Anthony]

Do you think it's a coincidence then that the protrusions on the inner edge of the rings are always aligned under the crank arm in all Shimano drawings?

http://cycle.shimano-eu.com/media/techd ... 704680.pdf

http://www.paul-lange.de/fileadmin/paul ... -IG-96.PDF

 

[cchris2lou]

I thought the Syncross had the fith bolt underneath the arm .

 

[FMJ]

Do you think it's a coincidence then that the protrusions on the inner edge of the rings are always aligned under the crank arm in all Shimano drawings?

http://cycle.shimano-eu.com/media/techd ... 704680.pdf

http://www.paul-lange.de/fileadmin/paul ... -IG-96.PDF

Who said anything about Shimano? We're talking about 5 bolt Syncros and Race Face middle rings here. Both have 4 ramp pins and machined ramps on the middle rings, while the outer rings have 10 machined ramps. No matter which of the 5 mounting options middle relative to outer you chose, they will always line up to each other's ramp pattern the same, only the pattern will be rotated 72 deg. to the axis of the crank arm from the previous one. Which ramp pins are (or aren't) lined up to the crank arms (none will line up on the Race Face) means nothing.

 

[FMJ]

I thought the Syncross had the fith bolt underneath the arm .

No. they have a gizmo called a Stress Transfer Device that bolts on to the crank arm at the 2 granny ring mounts closest to the crank arm, the middle and outer rings bolt on to that. It's supposed to be due to stress risers created from the otherwise machining of the two said spider arms.

Here's the cranks that are on my Dekerf.

 

[FluffyChicken]

Syncros call the alignment pins 'timing markers' these should be aligned up with the arms as per their instructions.
If not it put the ramps in the wrong position for where they are designed to ramp through the pedal cycle.

Saying that Sycros are quite rudimentary shifting and there is little profiling of the pins going on, unlike Shimano 5-arms where barely a straight tooth can bee seen.

Anyway, the rings are knackered in the ebay auction

The STD give the Syncros part away, and that ugly left cranks arm.
these may be some 1998 cranks thing (1997 used stickers with no logo, and no STD, 1999 was embossed logo's with STD. 1998 used STD but no idea what they looked like.
No idea if GT made OEM models of them (I think it's that logo that was used when GT nabbed them ?)

 

[Prometheus]

I have a set of these that I posted about over a year ago.

here's a link to the thread, I never did follow up on them so I have nothing further to add. The set on eBay is the only other set that I have seen other than mine....

http://www.retrobike.co.uk/forum/viewto ... ht=syncros

.

 

[dyna-ti]

Another point to add on the alignment pin question
As a chain ring wears the greatest amount of wear will occur with the pedals at a certain point[probably where the power is put down]
Re-aligning would move the worn section around to where there is less torque on it and give the chainring a longer life
Agree?

 

[FluffyChicken]

Another point to add on the alignment pin question
As a chain ring wears the greatest amount of wear will occur with the pedals at a certain point[probably where the power is put down]
Re-aligning would move the worn section around to where there is less torque on it and give the chainring a longer life
Agree?

Agree, and more so if you're chain is worn and you keep running on it.
But only really useful if you have no ramping pins or cutaways unless you don't care about where your shifting happens. But then you may as well be running standard rings in my opinion.
But then the greatest amount of wear will be where it shifts and removes a chunk of aluminium.

For the amount of miles or fun riding you'd have had to wear that much you might as well just invest in new ring or get steel to make them last. In the scheme of things, they don't cost much. Even a new low end chainset would be better than worn rings.

 

[dyna-ti]

I sometimes do it with used rings bought off ebay. just really depends on condition :?