New Red crank info, must read! :)

Discuss light weight issues concerning road bikes & parts.
deek
Posts: 406
Joined: Fri Aug 31, 2012 6:32 pm

by deek

That's a 53/39 chainring, which can't be rotationally symmetric by 180 degrees. It still is designed to upshift on two quadrants and downshift on the other two quadrants.

Image

Take a look at a 50/34 chainring set. It is symmetrical.

I think the only thing you need to worry about when using aftermarket chainring sets with this crank is the thickness of the ring. Since the ring mounts to the hidden bolt tab on the outside of the ring vs the inside of the ring like all other rings, you could get some run out issues if the new ring is not the correct thickness.

by Weenie


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CharlesM
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Location: Phoenix Arizona

by CharlesM

If the green boxes sizes match on your monitor, you may want to adjust settings... :beerchug:

Even if the pins did match up in timing and these were symmetrical(and they're not), the 5 bolt pattern doesn't allow for swapping the rings to either of the two other semi-opposite crank bolt spots to have the pick ups / pins and ramps be in the best position relative to the crank position where most people are applying the greater / lesser power to allowe for best pick up.

deek
Posts: 406
Joined: Fri Aug 31, 2012 6:32 pm

by deek

You're missing the point. There are basically 4 areas of your chainring that you need to worry about. This is when:

Right foot at top dead center (low load, where downshift occurs)
Left foot at top dead center (low load, where downshift occurs)
Right foot totally forward (high load, where upshift occurs)
Left foot totally forward (high load, where upshift occurs)

The first two conditions are the same and so are the last two. Chainring designers aren't designing rings to be leg specific and they shouldn't be since your legs are more or less equal. The Red cranks just rotated the spider 180 degrees. Rotate your rings 180 degrees to follow suit. I never said that rings have to be totally symmetrical to work well. A 53/39 set can't possibly be symmetrical while a 50/34 will be (I'm sure designing half a ring is much more attractive). Any and all chainrings will have two sections for upshift and two for downshift.

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CharlesM
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by CharlesM

I'm not missing the point.



The suggestion is that inverting the orientation of the chain rings wouldn't make a difference because they are the same at the top and bottom.

They're not only not the same (the ramps and pins on opposing sides are very simply not the same location or spacing), but because the number of bolts is odd, there is no bolt hole that lines up correctly in the average power curve to do the job correctly.

You're talking about making a 180 degree change, but you'll have to explain how that is possible in 72 degree increments... 5 bolts in 360 degrees...


The chain drop pick up is also located at the crank relative to where its most likely going to come over the top and off the ring. That's not a big deal for any properly adjusted drive line, but its also designed to be located at the crank.


Put simply...
Rotating rings 180 (or more accurately, 144 or 216) from where they're designed to be installed will not work as well as installing them where they are designed to run.

deek
Posts: 406
Joined: Fri Aug 31, 2012 6:32 pm

by deek

144/214 degree rotation is not more accurate, it is flat out incorrect. We are talking about putting aftermarket rings on a new Red crank. A new Red crank has a spider that is rotated 180 degrees from the old Red crank or most other cranks (DA 9000 and Campy excluded). The only thing you're giving up by rotating the rings 180 degrees is the catch pin. But like you said, it's not a big deal.

I can tell that I'm not going to convince you otherwise, but hopefully I convinced some others reading this. If anyone else wants further proof, look at the Red rings that Specialized uses on their cranks. They're the same as the one for the SRAM cranks, just rotated 180 degrees. They could also take a look at their inner rings which say to mount it one way for hidden bolt cranks and rotate it 180 degrees for non hidden bolt cranks.

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prendrefeu
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by prendrefeu

So, in the end, rotation is not a big deal.

It's only a big deal if you want to have your marketing department have your brand technically covered in case someone who is somehow extremely sensitive to every minute detail of the percentages of elements they are breathing as "air" in their lungs then complains about their front shifting not being absolutely-beyond-a-doubt-perfect-as-it-is-in-their-over-glorified-imagination. Which, as any half decent marketing department or lawyer will advise you, means you as a brand have to say "no" to what isn't absolutely perfect because that same person will probably launch a class action lawsuit, pitting your money against their high-strung butts. Which is a waste of time. Just like folks not reading a thread that is literally packed with nearly all the information a person may need to know about these really awesome cranks. Even the subject line says "must read!"

Which goes back to the original point: switching chainrings from the original SRAM to whatever-you-want is not a game changer. You probably won't notice any difference in shift quality (unless of course you switch to some really crappy chainrings for some reason). What you will notice is that the original SRAM chainrings, while beautiful, are damn heavy, and this is Weight Weenies, remember?

See page 10, bottom.
Exp001 || Other projects in the works.

Boralb
Posts: 113
Joined: Sat Aug 22, 2009 11:44 pm

by Boralb

After using the gxp compact version, here is the new bb30 compact 172.5mm, arrived today.
Happy with the weight so much.. Just 10g heavier than my hollowgram sisl2 53/39(spidering) :mrgreen:

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Juanmoretime
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by Juanmoretime

Does anyone know the length of the axle on the BB30 version? Possible retrofit with a VumaQuad bottom bracket?
RESIDENT GRUMPY OLD MAN.

Chello
Posts: 44
Joined: Sun Apr 22, 2012 8:23 pm

by Chello

The BB30 crankset will only work on BB30 frame. There is no way around it.

robdamanii
Posts: 4
Joined: Sat May 08, 2010 9:36 pm

by robdamanii

For those of you using Praxis or TA rings on your Red Quarq, did you have to do a full on recalibration or did the OmniCal feature take care of that?

goodboyr
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Joined: Wed Jan 10, 2007 10:56 pm
Location: Canada

by goodboyr

robdamanii wrote:For those of you using Praxis or TA rings on your Red Quarq, did you have to do a full on recalibration or did the OmniCal feature take care of that?


I've got the Quarq Elsa 10r which is identical internally to the Red Quarq. Its a compact and it came with the SRAM 50/34 rings. I changed them out to the Praxis 52/36 rings. I used the Qalvin app and a 20 kg NIST calibration weight and the slope was within 0.2% of the original. So, yes it appears that the OmniCal feature is the real deal.

Old Slope:4.405823

New Slope:4.414889

cailas
Posts: 2
Joined: Sun Apr 28, 2013 9:27 am

by cailas

When I bought my bike, was only compact version. I want to put 53 ring instead 50 on my Red compact crankset, will it work?

istigatrice
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Joined: Sat May 12, 2012 8:32 am
Location: Adelaide, Australia

by istigatrice

you'll probably need to change the inside ring too, the 53 to 34 drop might be too big for the RD... That's assuming it doesn't screw up your chain length and you can find compatible 53/39 110BCD rings
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jerbax18
Posts: 15
Joined: Tue Apr 30, 2013 3:42 am

by jerbax18

Hi. First Post.
Is anybody using 50/39 130bcd stronglight? Im using the stock 53/39 but 53 is too big for my legs.
Thanks.

by Weenie


deermatt
Posts: 108
Joined: Tue Aug 09, 2011 11:46 pm

by deermatt

Sorry if this has been stated, but I went through all 17 pages, and still not sure on the answer.. I currently use BB30 hollowgram SL cranks. If I sold them , it seems like on ebay I could get around 450 for them, if I bought the new 2013 exogram cranks in BB30, will they be lighter ?

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