Weight Weenies

Mackers wrote:I can imagine the 11S front derailleur working slightly better with the intended spacing.

What is the spacing on the new red crank? Would it be possible to shave a bit of my rings to make it narrower?

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Just got my BB30 Compact crank , 175mm in the mail today.

529g with the std rings.

Have the Praxis rings ready to go, so will check out the full weight a bit later, and add some pics too.

Just weighed all the bits separately and then with the Praxis rings, the crankset tips the scales at 491g

One minor issue though (need a pic later) that when the Praxis outer ring is installed, the inner edge when it mates with the hidden bolt on the crankarm needs to be trimmed ever so slightly - has anyone else struck this problem ? The std SRAM ring obvious;y doesn't have this issue.

Now for some pics

BB30 Comapct 175mm crank - std



Now issue with Praxis rings not quite fitting on the hidden bolt cutout.

First the std rings


Now the Praxis rings


It seems that the profile of the cahinring bolt area (square rather than chamfered) is the issue.

Has anyone else seen this or noticed this when fitting.

A quick lick of the file is probably all that is needed, but thought I'd check first.

Thanks in advance

Michael B

Edited to get rid of monster image. Bloody computers ...

I didn't have to file mine.

Now I see what you were referring to!

I didn't have to file mine either.
Are you sure that you have that ring facing the correct side? (maybe flip it?)
Barring that, and if everything is facing the correct side and rotated as you need to, it may be just a manufacturing hiccup that you encountered... and if that is the case, some minor filing wouldn't damage the ring.

I've got the same issue with non-original chainring. I think it's a bb30/gxp thing. Ie anything will fit on the GXP whereas the BB30 might have issues with some chainrings.

Edit:
The BB30 has a 'groove' in the crankarm (as per MichaelB's pic). The GXP has some added material on the crankarm to mount the chainring on:


I wonder if user CBRE did some modding on the various chainrings he used on his BB30 Sram Exogram crank (see the beginning of the thread).

It could also be a compact issue. My crank is bb30/standard and I didn't have to file anything.

More specifically, it seems like it is a BB30 + Compact specific issue, perhaps related to the Q-factor/angle the arm has to be at because of the BB30 specs.

BB30/Standard = OK
BB30/Compact = a little bit of filing.
GXP/Standard = OK
GXP/Compact = OK

The "compact bb30-hypothesis" certainly makes sense when thinking about it. My fit issue is on a compact BB30 as well (when combining with a Stronglight CT2 chainring).

Aha !!

Thanks MagnusH (you pic helped show the difference between compact and non-compact) and prendrefeu, it seems like the issue is noted !!!

So a bit of filing is in order. A chance to remove even more weight !!!!

I'll take some more pics when the job is done and post them up.

Thanks for the help guys

well that is a bummer because i was looking to do this next week but i have the compact one as well.

michael can you let me know when you get your set up and running because i would need some help on my side to make sure i do it right. thanks.

liketoride wrote:michael can you let me know when you get your set up and running because i would need some help on my side to make sure i do it right. thanks.

Can do.

First job is to strip the logos off the crank. Actually, gotta do a whole pile of other jobs, but happy to help where I can.

Anyone chime in on 11 speed compatibility (especially with Campy)? I've read that the old Red Crank works fine, but supposedly the spacings are different for the new one any info?

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Here are some pics comparing the spider connection points on both chainrings. In both pics, the SRAM 50T ring is on top.

First off, the connection to the crankarm (hidden one)


Now, all the other connection points on the SRAM one are different to the crankarm one, as seen here



Here is the profile of the cutout on the crankarm (BB30 compact). You can see why the cahinring has some different machining.


All makes sense now. For BB30 Compacts, the Praxis rings need to be filed slightly to match the profile as per the SRAM 50T chainring

Problem solved.