Technical FAQ: Shimano GRX and 12-speed compatibility, plus carbon braking

Have a question for Lennard? Please email us veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
Regarding this column, can I use a SRAM Road AXS cassette on my mountain bike (with XD body) boost bike?
Is this possible?
— Jay

Dear Jay,
No. The AXS 12-speed cassette is 1.85mm too wide for the XD driver; that cassette requires the wider XDR driver.

Furthermore, the SRAM 12-speed MTB chain doesn’t work on the road AXS cassette. You could use the road AXS chain on it, but it wouldn’t work on your MTB chainrings due to the chain’s bigger rollers.
― Lennard

Dear Lennard,
I’m replacing the front shifter on my 1×12 mountain bike. It is currently set up with SRAM Eagle GX all around, but I prefer the shifting actuation, and frankly, the durability, of Shimano. My specific question is, can I run an XT M-8100 shifter with a 12 speed GX rear derailleur? I’ve watched videos where the author claimed success using an XTR with an Eagle X001 but nothing involving lesser-priced models.

As a follow-up, have you found an across-the-board comparability between the two brands’ 12-speed MTB component offerings?
— Joe

Dear Joe,
I have not tried mixing and matching 12-speed Shimano and SRAM derailleurs and shifters, nor have I seen the list you ask about.

SRAM Eagle GX derailleurs and shifters are interchangeable with SRAM Eagle X01 derailleurs and shifters. Similarly, Shimano XTR derailleurs and shifters are interchangeable with Shimano XT derailleurs and shifters. So, if an XTR 12-speed shifter works with an Eagle X01 derailleur, an XT 12-speed shifter should work exactly the same with an Eagle GX derailleur. I’m not saying it does work; I’m just saying that if the first combination works, then the second combination must also work. Likewise, if the first combination doesn’t work, then the second combination also will not work

If you try this, I’d love to hear how it works for you.
― Lennard

Dear Lennard,
I’ve known Shimano mechanical road STI levers had a different pull that wouldn’t work with mountain read derailleurs. However, with fact that the GRX mechanical levers will shift on an XT cassette, doesn’t that mean the cable pull is will work with an XT rear derailleur. And, if that’s correct, would it be possible to run a GRX shifter with and XT-SGS rear derailleur with an 11-40t cassette and a 48/31t crankset and still be within the 47t capacity of the rear derailleur. Di2 is probably even easier.
Is this possible?
— Jeff

Dear Jeff,
No, the fact that the GRX shifter and derailleur shift on an XT cassette means nothing about the cable pull of the derailleur other than that it is matched to the lever so that it will shift on cassettes with that same spacing between the cogs.

For instance, if you were to use a Road Link derailleur-hanger extender, you could get some Shimano road derailleurs (with a road shifter) to work with an XT cassette, even though if you were to instead use an XT derailleur with that road shifter, it would not work on that cassette.

As for Di2, the GRX right shifter will work with the XT Di2 rear derailleur only if there is either no front derailleur, or an MTB Di2 front derailleur—not a GRX or road Di2 front derailleur.
― Lennard

Dear Lennard,
I ride an Enve 3.4 SES clincher wheelset on my Parlee Z5.The groupset is Dura-Ace 9100, (w/ D/A brakes).
As per the manufacturer’s requirements, I am using the Enve black carbon brake pads.
“ENVE requires the use of their pads in order for ENVE’s Five Year Warranty to take effect.”

I like the wheels except they do not brake well with the configuration I described above.

My last wheels were older ENVE carbon tubulars in conjunction with Ciamillo Micro-G brakes and Swiss Stop Black Prince pads. These wheels (& pads) were used for ~ 50,000 miles before I traded them in (during Enve’s buy-back offer last Fall). Although the braking surface was lightly scarred, there were no signs of delamination or compromise of the layup. I live in Tucson AZ and ascend/descend around 500,000’/year so these carbon hoops saw a LOT of high-speed downhill braking. As a bonus, I could lock these brakes up and power slide on the tires if required.

Now back to my new (and improved?) wheels.
The brakes will not lock up the wheels
The pads slow the bike down, but I fear not having enough stopping power in a panic situation.
I can bury the brake levers to the bars and the bike keeps rolling.
The pad/rim gap is minimal to achieve maximum braking power.
I changed the pads after only 3 months; same results.

Do I compromise the warranty to save my life?
Aren’t D/A brakes the bomb/gold-standard (albeit heavy)?
Why not use Black Prince – they WORK!
— Michael

Dear Readers,
This could be a cautionary tale for anybody with any carbon rims who likes to wax their bike.

I sent Michael’s email to ENVE, who worked directly with him to solve his braking problem. This is the upshot of it:

“Well I finally got to the bottom of the issue. Turns out that this customer has a ritual of washing, lubricating, and polishing his Parlee after each ride. The polishing process consists of wiping down all raw carbon surfaces w/ an oil-based Pledge, including the braking surface. So, he was essentially lubricating his braking surface.”
— Jake Pantone
ENVE VP Product and Consumer Experience

The takeaway is that, while cleanliness may be next to godliness, too much focus on cleanliness may make you unstoppable.
― Lennard

Dear Lennard,
I own two sets of Velomax/Easton wheels, the Orion II and the Circuit. While I’ve enjoyed riding the Orion IIs for three seasons, I’m a bit miffed about the high cost of spoke replacement. On two occasions, about two years apart, I have had a broken rear wheel drive side spoke with the breaks occurring at the nipple.
When I contacted Velomax the first time about getting a replacement spoke, I was told that the only way was to have Velomax install the spoke and the all spokes would have to be loosened and re-tensioned. With shipping costs, that was around $50. Now that Easton has an East coast service center in New York, I got the same answer when the second spoke broke last month. This time, the total cost of replacement including shipping was around $64.

I’m not cheap and don’t mind paying for quality. However, I can’t help but feel that spending a total of $114 for a couple of spoke replacements is outrageous. Although I’m an OK wheel builder and have built about a dozen sets of wheels, I’d still like to have the option of either doing a self repair or having the LBS do the job for less cost.

Are you aware of any source for the same type of spokes used in these wheels so that a reasonable alternative is available?
Thanks,
— Bill

Dear Bill,
I googled “spokes for Velomax/Easton wheels” and found lots of options like this.
― Lennard

Feedback on last week’s column  :

Dear Lennard,
Great article on spoke/nipple breakage in VeloNews online. I felt compelled to send this email, because Bill Mould stated that both “[replacing nipples and spokes] is expensive and time consuming”. Really? A good Sapim race spoke costs around $1 retail per spoke and nipples are like 10 cents each. It takes me less than an hour to rebuild a wheel.

You are spreading false notions to consumers that replacing spokes and nipples is time consuming and expensive. I wish more riders would send me their factory wheels (which more often than not, tend to be built poorly) so I can rebuild them with better equipment and technique.
— Brian Staby
Baker’s Dozen Wheel Works

Dear Lennard,
In this week’s column, you write: “While I have seen corrosion of aluminum rims from tubeless tire sealant with ammonia in it, blaming broken spoke nipples on it is a big stretch, since the quantity of sealant getting under the rim tape to the nipples will be zero or near that if the tire remains inflated.”

Based on my experience working as a mechanic at a mountain bike-oriented shop (where we dealt with tubeless problems daily) I’m confident saying that you are mistaken on that last point. If the tubeless tape is properly applied, properly seated before sealant is introduced, and replaced at the first signs of peeling or other damage, then yes, there will be effectively zero sealant reaching the nipples. Unfortunately, I’ve seen many cases in which tubeless tape was poorly applied from the factory (or shop), or never properly seated, or left in place despite damage and peeling, and in these cases, it is very common to find significant accumulation of sealant and visible corrosion on and around the nipples. And that can occur even if the tire remains inflated. So, while it may not be the primary cause of broken nipples, sealant in the rim cavity is quite common and can weaken alloy nipples and/or cause them to seize. One more reason to be careful and patient when applying tubeless tape.
— Sam

Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”
He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn