Quarq Power Crank Install (SRAM Red Cranks)

Now I’ve done it.  I’ve gone and installed a power meter.  D’oh.  Life will never be the same.

Install detail:

This went on the Ridley Noah.  You can see the Time Carbon i-Clic pedals, the KMC DLC chain, and just a peek of the ENVE wheels.

In proper RATG form, the first step is putting on your rubber gloves.  Then, secure the bike in the bike stand, and loosen the allen screws holding on the non-drive side crankarm.

(While disassembling, take a slightly blurry picture of an allen wrench).

Using the specific star-shaped wrench for the job, remove the plastic nut that secures the non-drive side crankarm to the crank.

Remove non-drive side crankarm.

Look at that…it’s clean and greased!  Who’da thunk–on one of my bikes…?  Next, slide the drive-side crank and chainring out through the BB.  Because I’m using a BB-based magnet to trigger the power cranks, the next step is removing the drive side of the BB, with a BB wrench or socket.

Right about now is where we gaze lovingly at the Quarq box…

And then we open it up to find a spiffy new crank inside.  (Disregard the disc brake packing parts).

The timing magnet can be mounted on the cable holder underneath the BB, can be glued onto the frame, or can mount behind the BB cup.  I chose that last option.  Here’s the stainless steel ring + magnet that comes with the crank.

And here it is installed; it simply slides over the BB, and the BB gets tightened down onto it.

Here’s the one odd part of my install…My existing Shimano BB bearings were in good shape, and I planned on reusing them.  However, when I tried to install the SRAM crank, it would not tighten down on the BB…even after trying several times, I had close to 2mm of lateral play in the crank.  After much fumbling and online research, I decided to try a flyer…I had a new SRAM GXP bb sitting in a box with parts intended for the Vaytanium.  I took it out, and slapped it in the Ridley…and then the crank fit perfectly.  From the reading I’ve done, the Shimano and SRAM BBs should be interchangeable…I cannot explain this fitment issue.  I would recommend checking into it if you’re contemplating a power crank install.

The new crank slides through the BB from the drive side, and the non-drive side crankarm gets indexed to 180 degrees from the drive-side crank, and then carefully tightened with an 8mm allen key.  Note that there are 2 hex holes in the non-drive side crank.  Disregard the outer hole on a standard install.  Torque specs are on the crank…I used a Park Tools beam torque wrench to set and check the torque.

I should also note that I lubricated the splines on the crank, and the crank shaft that goes through the BB, with a little grease.

When installing the pedals, I also shot a little grease inside the crankarm pedal holes…and don’t forget to use the pedal washers that come with the crank:

This is the finished install:

Before my install, I did a weight comparison between the two cranks…this is cranks only, with both crankarms, no BB and no pedals.  The Ultegra weighed in at 704 grams (about 1.55 pounds):

The Quarq weighed in at 796 grams (1.75 pounds):

The BB mounted magnet is only a handful of grams…so adding the power crank added about 0.2 pounds to the Ridley.  That’s more than acceptable, in my book.

My basic training plan is to ride for a week or two and get some baseline wattage numbers, without watching wattage while riding.  After I have some idea of what my baseline power output is on a ‘normal’ training ride, I’ll try to undertake some detailed power-crank based training, and up my wattage.  The goal is to improve both my maximum sustainable wattage and my peak, sprinting wattage.  From the NCC Indoor Nationals, I know that my sustained wattage in a maximum effort, 1 hour indoor/trainer ride (on terrain ranging from 10% descent to 20% incline) was around 235 watts.  At my then current 150 pound weight (about 65 kilograms), that would equate to about 3.5 watts/kilo.  That’s measured on the Tacx Bushido.  I’ll be very curious to see what the Quarq results are, for a few reasons.

First, I suspect the Bushido is off…according to most of the power/weight charts I’ve seen, 3.5 watts/kilo would put me squarely in Cat 3 standing…and I’m simply not there.  Part of the issue is that I suspect my 1 hour endurance riding is disproportionately more powerful than my shorter endurance speed riding, and part of the issue has to be trainer error.

Second, I’m both lighter (around 143 pounds, at last measurement) and faster than I was 6 months ago.  Lighter is not a good thing–and believe me, it’s not intentional.  Faster is a good thing.

Third, I’ve previously written that I stopped using a heartrate monitor because I was psyching myself out…I’d see 99 or 100% of my MHR, and would convince myself that I was pushing too hard and needed to slow down.  Since dropping the HRM, my riding has improved greatly, and I get in my head a lot less.  I’m curious to see how the power meter works into my psyche…is it an informational tool that I can use to train and rider harder, or will it get in my head.  The jury’s still out on that one.

Once I get some time on the power meter, and some initial results, I’ll report back with more detail.

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7 thoughts on “Quarq Power Crank Install (SRAM Red Cranks)

  1. I am also curious about how accurate the bushido is as far as wattage compared to a precision crank like this. I hit 1,200w a few times on it while trying to see my max, but i am very skeptical because i hit 1,200w a few times while trying to see my max.

    Sram and Shimano use the same diameter spindle, but on sram cranks the non-drive bearing I.D. is slightly smaller, so the do require different b/bs.

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