Thread: GRX Di2
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Old 05-22-20, 09:25 AM
Bryan C. 
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Recently I decided to upgrade my 2019 Diverge from a Sram Force 1x to a Shimano GRX Di2 2x drivetrain. The bike is too new for me to justify selling it and buying a new bike already equipped with electronic shifting. The overall cost would be similar, or even more, considering how much money I would lose selling the bike itself. It made sense for me to keep it and upgrade what I didn't like.

I was torn between a 1x12 Sram Force/Eagle set up and the GRX 2x. Most of my local LBS's have the Sram Force/Red/Eagle set ups on their high end bikes and were not easily available for me to test ride. My opinions of Sram are based only on what I was using, Sram Force 1.

Ultimately there were a few things that made the decision easy for me:

1) $700 for a Sram Eagle AXS rear derailleur to me is ridiculous. One good wipe out and you are out some serious cash for repairs. Sure, I don't think the average gravel rider is pushing the limits of their bike but my own recent experiences of wipe outs has shown that it can and will happen. Nobody plans to wipe out, but it sure does happen quickly when you run out of talent.
2) I absolutely HATE the Sram Force 1 hydraulic brakes. Even after the upgrade to 4 piston Hope RX4 calipers the brakes still didn't improve much. They're probably OK if you weigh under 170 lbs but for me at 210+ pounds they left me with hand cramps and taking descents at a much higher speed than I would prefer. Add to that me constantly comparing them to my road bike's Shimano DA brakes there really was no reason to continue on with them on my bike.
3) The lack of a bonafide Sram XC/gravel friendly 12 speed cassette. The recent release of the wide range gravel 2x AXS set up from Sram could have been a game changer had they made something similar to the Shimano 10-45 12 speed cassette. I'm not sure Sram is really interested in designing any drivetrain components for anyone other than strong riders. I guess that's their business model, and they are free to do as they want. For aftermarket cassette support all I could find was a 9-46 12 speed cassette from Rotor that would work ok but availability was very limited when I looked into it and the price was expensive.
4) Sram and their MAP pricing forces retailers to sell at full price. Not only that, most places do not discount Sram products or offer sales or incentives of any kind. The best deal I could find was clicking through rebate sites for whatever percentage rebate was offered. 10% or less is hardly anything to get excited about but it does add up if Sram is your go-to components.

Ok, enough with the Sram bashing. No need to pile on.

I chose the GRX Di2 based exclusively on the idea that the brakes would be a major improvement. And with transitioning to a 2x system I felt Shimano was the right choice for that. My build consisted of the following:
815 front and rear shifters, calipers, and L03a pads(more on that later)
815 front derailuer
817 rear derailuer
Bar end junction port with internal handlebar cable routing
Wireless/Bluetooth module
Sram 12 spd eagle chain
Sram 10-42 cassette
Praxis 48/32 double chainset

All of the major GRX components were purchased with a 20% off discount code and with an additional 12% off through a rebate site. Total savings in the neighborhood of $600 off of retail.

I chose to re-use the factory equipped Praxis Zyante carbon cranks. I simply changed the 1x chainring out for a 2x LT2 Praxis spider and chainring set. My preferred setup would be a 46/30 chainset with an 11-40 cassette but my Diverge can barely handle the 32t small chainring due to frame clearance issues with the chainring bolts. Ross over at Praxis helped me figure out how to work around this problem with using some shaved down chainring bolts. I was able to make it all work thanks to his help.

According to the bike gear calculator it shows this system has a 630% range. The 32/42 climbing ratio is pretty nice. The Sram cassette is fairly well spaced except for one combination that I seem to fall into regularly. I may try the Shimano 11-42 cassette as the jumps are small, 2 teeth, until you're near the mid-point of the cassette. Still working on that but for now the Sram cassette is staying in place.

The 817 RD does limit one feature of Di2, synchronized shifting. Without the matching front/rear 815 derailleurs, the system will not allow you to program the sync shifts. Not sure if anyone has found a work around for this yet but for now I can just shift the front as needed. Not a deal breaker for me but it may pose issues for those that use Di2 on multiple bikes and like that feature. The auto trim feature still works just fine so no worries about chain rubbing on the front derailleur cage.

Now the brakes. Shimano updated their L02a resin pads to a different compound. The new L03a pads came installed in the GRX calipers. This is probably my favorite part of the upgrade. I can't say enough about how much of an improvement these brakes are. Better stopping power, better modulation, and better power than the Sram brakes they replaced. Light riders may say they are too grabby, but if you are a fat ass like me then they will be perfect.

Overall the upgrade has been a complete success, and for me worth every penny.
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