New Red crank info, must read! :)

Discuss light weight issues concerning road bikes & parts.
MichaelB
Posts: 448
Joined: Tue Apr 22, 2008 4:31 am

by MichaelB

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)
Image

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


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

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 :smartass:

Problem solved. :thumbup:

by Weenie


liketoride
Posts: 302
Joined: Wed Nov 21, 2012 3:05 am

by liketoride

thanks, that really helps, great pics.

sawyer
Posts: 4498
Joined: Fri Dec 15, 2006 7:45 pm
Location: Natovi Landing

by sawyer

I got my Exogram BB30 Compact 50-34, 172.5mm last week.

523g ... genuinely light even by WW crank standards.

...and less WW was the price ... $350 new from an ebay retailer
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Stiff, Light, Aero - Pick Three!! :thumbup:

Stuartclark1977
Posts: 88
Joined: Tue Sep 13, 2011 9:45 pm

by Stuartclark1977

Image

So - pre-stripping.

170mm 53/39 BB30 and 549g, with a decent chunk of grease that came on the spindle, doesn't include the pedal washers or PF30 fittings.

Plan is to strip it back to bare carbon, 303 it, add some Praxis Classic rings and then stick it on my Firefly. When I have I'll use a camera rather than an iphone for a photo!

Praxis classic - SRAM red
112g - 139g
32g - 33g
Saving 28g

So pre strip 519g (there was 2 grams of thick blue grease on the spindle as well!)
For comparison my da7900 170mm 50/34 was 653g and I will be dropping a pf30 adaptor from the mix as well.
Last edited by Stuartclark1977 on Tue Dec 18, 2012 11:40 pm, edited 1 time in total.
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LVGH
Posts: 216
Joined: Mon Jun 18, 2007 3:12 pm
Location: NL

by LVGH

Has anyone tried to fit Red Black rings to the Exogram crankset? I don't like the new ring design. Does this fit and shift properly, also with older Red front derailleurs?

Imaking20
Posts: 1543
Joined: Fri Nov 18, 2011 5:19 am

by Imaking20

You'd be doing a MAJOR disservice by using red black rings... the best part of the new crankset is shift performance and these rings perform light years better than the old.

That said, I'm sure they'll fit. Knock yourself out.
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gospastic
Posts: 266
Joined: Tue Jun 08, 2010 4:58 am
Location: Chicago

by gospastic

Stuartclark1977 wrote:
So - pre-stripping.

170mm 53/39 BB30 and 549g, with a decent chunk of grease that came on the spindle, doesn't include the pedal washers or PF30 fittings.

Plan is to strip it back to bare carbon, 303 it, add some Praxis Classic rings and then stick it on my Firefly. When I have I'll use a camera rather than an iphone for a photo!

Praxis classic - SRAM red
112g - 139g
32g - 33g
Saving 28g

So pre strip 519g (there was 2 grams of thick blue grease on the spindle as well!)
For comparison my da7900 170mm 50/34 was 653g and I will be dropping a pf30 adaptor from the mix as well.


I'm surprised by the weight difference on the Praxis rings. I'm also using the classics and mine were 98g and 31g respectively.

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Wizzo
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Location: San Francisco, CA
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by Wizzo

Couldn't be more happy. Filing wasn't very hard nor do you have to file much at all.

Image

MichaelB
Posts: 448
Joined: Tue Apr 22, 2008 4:31 am

by MichaelB

Wizzo wrote:Couldn't be more happy. Filing wasn't very hard nor do you have to file much at all.


I presume yours was BB30 & compact ?

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Wizzo
Posts: 115
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Location: San Francisco, CA
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by Wizzo

Yes it is, BB30 172.5 with Praxis 52/36. I had the luxury to open couple of standard BB30 and GXP cranks with the corresponding BCD Praxis rings to confirm. Should've just read Page 8. :roll:

mate
Posts: 20
Joined: Thu Sep 13, 2012 7:31 am
Location: Slovenia

by mate

Wizzo wrote:Yes it is, BB30 172.5 with Praxis 52/36. I had the luxury to open couple of standard BB30 and GXP cranks with the corresponding BCD Praxis rings to confirm. Should've just read Page 8. :roll:

Did you tried them yet?

How is the shifting with these 52/36?

yeagermeister
Posts: 169
Joined: Mon Aug 29, 2011 8:55 pm
Location: New Jersey

by yeagermeister

Great info here! Does anyone have a weight for a BB30 Quarq setup? Someone posted a gxp quarq combo which was heavy but I was wondering if the BB30 setup would be lighter.

mises
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by mises

From reading this thread it appears that, including BB's, the 170mm BB30 compact I just ordered for my wife's bike will be within 1g of my old THM Clavicula BSA 175mm using the same rings. This is truly appalling. :shock: Maybe I miscalculated....

OwenN
Posts: 40
Joined: Sat Dec 24, 2011 2:28 am
Location: Roanoke, VA

by OwenN

Could someone do me a favor and weigh just the left-side arm/spindle of a BB30 style crank? A scale picture would be best. I ask because I am running a Quarq on an BB30 S900 and I am wondering how much weight I could save by using a Red crank on the left side. Also, does anyone know if this combo would work? Would the left/right arms be 180 degrees?

Stuartclark1977
Posts: 88
Joined: Tue Sep 13, 2011 9:45 pm

by Stuartclark1977

Image
Without lock-ring
Image
With lock-ring
Image
Spline pattern

This has lost the SRAM graphics but not been aggressively sanded.

I'm also not sure how the end shot of the spline weighs an extra 2 grams than the side on shot but should help you determine if the cranks would line up okay. (Maybe you should average them to a 179g without the lockring.)

They are 170mm 2012 SRAM Red BB30, hope that helps.
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Firefly FF050
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by Weenie


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