Ask Pinkbike: AXS Derailleurs, Izzo Shocks, & Brake Caliper Conundrums

Here at Pinkbike, we get inundated with all kinds of questions, ranging from the basic “Can I have stickers?” to more in-depth, soul-searching types of queries like if you should pop the question or what to name your first child. Ask Pinkbike is an occasional column where we’ll be hand-picking and answering questions that have been keeping readers up at night, although we’ll likely steer clear of those last two and keep it more tech-oriented.


Ohlins air shock for a YT Izzo for the BC bike race?

Question: @Yet1man asks via PB Mail: I’m looking at the possibility of changing the rear shock on my YT Izzo to the Ohlins TTX air. How do you find it performs on the Izzo?

I’m not looking at turning the Izzo into a mini Enduro rig, just looking at upping its range of usability slightly. One other reason for changing the rear shock is I’d like to ditch the grip shift lockout. I’m looking at using this bike for the BC Bike Race next year, so need to retain its eagerness to climb, but need the bike to be burly enough to ride Squamish, Vancouver’s North Shore, etc.

bigquotes As well as reviewing an Ohlins TTX2 air shock on my Privateer 161, Ohlins sent me a YT Izzo to review their RXF 34 fork which was also fitted with an Ohlins’ TTX1 air shock. The TTX1 has a smaller volume air can and so is more progressive than the TTX2, which, combined with the Izzo’s kinematics, meant I had to fit the smallest volume spacer to get all the travel without too much sag.

As with the TTX2 I reviewed, the TTX1 on the Izzo has a very usable range of adjustment, which makes it possible to fine-tune the damping feel in a meaningful way, but without it becoming over-complicated; the scope to get the setup really wrong is less than it is with some shocks. I was able to get a setup I was happy with, running 28% sag, the high-speed compression in the firmer setting and the low-speed compression near the middle.

On the other hand, the shock fitted to a bike by a manufacturer is usually selected for a reason, and they usually go through several different tunes with the suspension manufacturer to find what works best for the bike. So in general, swapping shocks isn’t something I’d recommend lightly.

Based on your comment about the twist-grip lockout I’m assuming you have one of the first-generation ones with the Fox DPS shock. While I have n’t ridden the Izzo with that damper, Dan Roberts was impressed with his performance in his review, and I’m not sure how much better it would descend with the Ohlins. At the end of the day, the less travel you have the lower ceiling for potential performance in terms of sensitivity, traction and bump absorption. While you might be able to get it to handle gnarly terrain in a way that’s slightly more to your tastes using the extra adjusters, given there’s only 120 mm of movement to optimize I don’t think it’s going to change your world.

Besides, what struck me most about the Izzo with the TTX1 was how mediocre the pedaling efficiency was for the travel. I was regularly reaching for the climb switch, and if I was going to do a multi-day race, a lockout is not something I would want to forgo. I realize that the twist-grip remote is ergonomically awful, but have you considered swapping to an under-bar remote like this Fox-compatible one from DT Dwiss and a normal grip?


SRAM AXS clutch issues?

Question: @Mikelb01 asks in PB messages:

Have you ever had an issue with Sram AXS rear derailleurs and the clutch for the cage not being strong enough and the bike having a lot of chain slap? I’ve had a few of these rear derailleurs now and after a short few months of riding the rear derailleur’s clutch mechanism seems to lose tension

bigquotes It’s certainly true that the ability to adjust the clutch force is a feature many of us would like to see from SRAM derailleurs. Especially as the chain and chainring start to wear, it would be nice to increase the amount of clutch force to ward-off chain derailment.

In his review of SRAM GX Eagle AXS, Mike Kazimer noted that “I do think the main clutch tension could be increased a little. I never dropped a chain, but I did notice a fair amount of chain slap noise when riding through rough terrain, or after a larger impact”.

It’s worth noting, however, that a firmer clutch can result in clunkier downshifts, requiring more force at the shifter paddle. In the case of electronic shifting, a firmer clutch increases battery consumption for the same reason, according to SRAM. Firm cuts may also increase drivetrain friction and reduce suspension sensitivity, albeit very slightly, so there are good reasons not to go crazy with the clutch force. If you’re experiencing chain noise but not dropped chains, perhaps rubber frame protection is a better solution.

As for the crux of your question: is the cage clutch less forceful on AXS derailleurs than their mechanical counterparts and does the clutch force drop off with use? This is something Pinkbike editors have several about so I reached out to say something

bigquotes Your reader could be picking up on the cable and hosing putting an anti-rotational load into a mechanical derailleur which could reduce ‘chain slap’ but has no impact on shift performance or chain retention. There is no difference between the AXS and Mechanical RD that would lead to a ‘lighter feeling clutch’… Our warranty data does not show changes in clutch force resulting in SRAM RDs reducing their shift performance or dropping chains over time. We have the most robust customer service in the industry and if riders feel they are experiencing chain dropping or poor shifting issues they should reach out to their dealer or SRAM Rider Support.SRAM

Does the mounting position of the caliper around the axle matter?

Question: Guillaume asks via email: Does the angular position of the caliper around the axle matter? Sure it matters if it’s placed on the chainstay or seatstay, but does the angular position around the axle matter if it’s placed on the same frame member?

Some say yes, some no. Those that say yes think that it’s placed in front of the axle to push the wheel down and that if it were placed behind the axle it would push the wheel up, as in this explanation.

bigquotes Thanks for sending this over. That’s a good article you linked, but unlike the author, I think the angular position of the caliper on the disc does not affect suspension behavior.

Of course, it definitely matters whether the caliper is mounted to the chainstay (single-pivot) or the seatstay (Horst-link or split-pivot). That’s because the chainstay typically rotates more than the seatstay as the suspension compresses, and so the brake torque acts to compress the suspension more strongly if it’s connected to the chainstay than the seatstay. This effect is known as anti-rise, and it explains why single-pivot-bikes generally sit lower in their travel while braking than comparable horst-link or split-pivot designs.

Take these two Mondrakers – the caliper is attached to the same frame member but at different angles relative to the axle. Does that make a difference? Spoilers: No.

But exactly Onde the caliper is mounted on any given frame member (seatstay or chainstay) doesn’t matter. Yes, if the caliper is mounted directly in front of the axle it will apply a downwards force on the swingarm (as shown in this image from the above article), but this is canceled out by an upwards force at the axle; , if the caliper was mounted directly behind the axle (as while in this diagram), it would pull up on the swingarm, but the axle would apply the same amount of force downward. (Picture spinning the wheel without the axle installed, then pull the brake – the hub will shoot out of the dropout in the opposite direction to the force applied by the caliper).

So, wherever the calliper is positioned on the swingarm, the torque it applies to the main pivot is the same, and that’s what determines braking behavior.


Code RSC dial stuck?

Question: Gene158 asks in the All Mountain, Enduro & Cross-Country forum: I installed new Code RSC brakes on my Meta TR about a month ago. I followed the bleeding procedure correctly and the brakes were working great. About a week ago however, the contact point adjuster dial on the rear brake lever stopped working. I didn’t crash or hit it on anything, but the dial just won’t spin in either direction now. I’m not sure what the issue could be. Has anyone else encountered this issue?

bigquotes This is a pretty common issue. The contact adjuster can get sticky and hard to turn if it’s not been used for a while.

Sometimes, at least in my experience, it’s easy to simply turn the dial the wrong way, into the stop limit instead of away from it. Remember that to move the bite point outwards you have to turn the dial on one lever away from you and the other towards you; that’s because the levers are identical (not side-specific) but they’re facing opposite directions.

But assuming you’ve tried turning them in both directions, it usually just takes a bit of extra force to budge the dial. It’s hard to get any purchase on the narrow little adjuster wheel, so try wearing gloves. If that doesn’t work, try a bit of penetrating oil (eg WD-40) on the adjuster, making sure to prevent contamination of the caliper (perhaps by leaving the bike upside down), leave it a minute to soak in, and then try again. If it’s really stuck, perhaps try a pair of thin pliers with a cloth to prevent scratching the lever, though I’ve never had to resort to that myself. I’ve had a lot of experience with these brakes and while the adjuster can get stuck, it always seems to un-stick with a bit of persuasion.

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