Ask Pinkbike: AXS derailleurs, Izzo shocks and brake caliper puzzles

At Pinkbike we are inundated with all kinds of questions, ranging from the simple “Can I have stickers?to more in-depth and introspective types of queries, like whether you should ask or what to name your first child. Ask Pinkbike is an occasional column where we’ll select and answer questions that kept readers up at night, though we’ll probably avoid the latter two and keep them more tech-focused.

Ohlins air shock for a YT Izzo for BC bike racing?

Question: @Yet1man request via PB Mail: I am studying the possibility of changing the rear shock of my YT Izzo to Ohlins TTX air. How do you find it performs on the Izzo?

I’m not looking to turn the Izzo into a mini Enduro rig, I’m just looking to slightly increase its range of usability. Another reason to change the rear shock is that I’d like to ditch the shifter lockout. I’m planning to use this bike for the BC Bike Race next year so I need to keep up its eagerness to climb but I need the bike to be beefy enough to ride in Squamish on the North Shore of Vancouver, etc

In addition to reviewing a Ohlins TTX2 air shock on my Privateer 161, Ohlins sent me a YT Izzo to review their XRF 34 fork that was also fitted with an Ohlins TTX1 air shock. The TTX1 has a smaller air volume and is therefore more progressive than the TTX2, which combined with the kinematics of the Izzo meant that I had to fit the smaller volume spacer to get the full travel without too much drudgery. subsidence.

As with the TTX2 I reviewed, the TTX1 on the Izzo has a very usable range of adjustment, allowing the damping feel to be refined significantly, but without it becoming overly complicated; the chance of getting a really bad setup is less than it is with some shocks. I was able to get a setup I was happy with, with 28 percent sag, the high-speed compression in the firmest setting, and the low-speed compression near the middle.

On the other hand, the shock installed on a bike by a manufacturer is usually selected for a reason, and they usually go through several different settings with the suspension manufacturer to find what works best for the bike. So in general, swapping shocks is not something I would recommend lightly.

Based on your comment on the twist grip lockout, I assume you have one of the first with the Fox DPS shock. Although I did not ride the Izzo with this shock, Dan Roberts was impressed with the performance in his review, and I don’t know how much better it would be with the Ohlins. Ultimately, the less travel you have, the lower the ceiling for potential performance in terms of sensitivity, traction and shock absorption. While you may be able to get it to handle gnarly terrain in a slightly more to your liking using the extra adjusters, given there’s only 120mm of movement to optimize, I don’t think it will change your world.

Also, what struck me most about the Izzo with the TTX1 was how poor the pedaling efficiency was for travel. I was hitting the uphill switch regularly, and if I had to do a multi-day run, a lockout isn’t something I’d want to give up. I realize the twist grip remote is awful ergonomically but have you considered upgrading to an under the helm remote like this compatible Fox from DT Dwiss and a normal plug?


SRAM AXS clutch problem?

Question: @Mikelb01 request in PB messages:

Have you ever had a problem with the Sram AXS rear derailleurs and the cage clutch 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 few months of riding the rear derailleur clutch mechanism seems to be losing tension

great quotes It is certainly true that the ability to adjust the clutch force is a feature that many of us would like to see from SRAM derailleurs. Especially when the chain and chainring start to wear out, it would be nice to increase the clutch force to prevent chain derailment.

In his SRAM GX Eagle reviews AXS, Mike Kazimer noted that “I think the main clutch tension could be increased a bit. I’ve never dropped a chain, but I did notice a fair amount of chain slapping noise when I rides on rough terrain or after a greater impact”.

It should be noted, however, that a firmer clutch can result in clumsier downshifts, requiring more force on the shift paddle. In the case of electronic shifting, a firmer clutch increases battery consumption for the same reason, according to SRAM. Firm cuts can also increase transmission friction and reduce suspension sensitivity, although very slightly, so there’s good reason not to go crazy with the clutch force. If you are experiencing chain noise but no chains dropping, perhaps rubber frame protection is a better solution.

As for the crux of your question: is the cage clutch less powerful on AXS derailleurs than their mechanical counterparts and does the clutch force decrease with use? This is something several Pinkbike editors have wondered about, so I reached out to SRAM for comment and here’s what they had to say:

great quotes Your drive could capture the cable and hose by putting an anti-rotation load in a mechanical derailleur which could reduce “chain slap” but has no impact on shifting performance or chain retention. There is no difference between the AXS and the mechanical RD that would lead to a “lighter clutch”… Our warranty data shows no changes in clutch force resulting in reduced shift performance speed of SRAM RD or chain drop over time. We have the most robust customer service in the industry and if riders feel they are having issues with a chain dropping or poor shifting, they should contact their dealer or SRAM Rider Support.SRAM

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

Question: Guillaume asks by e-mail: is the angular position of the caliper around the axle important? Of course it matters if it is placed on the base or the seat, but does the angular position around the axle matter if it is placed on the same frame member?

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

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

Of course, it really matters whether the caliper is chainstay-mounted (single-pivot) or chainstay-mounted (Horst-link or split-pivot). This is because the chainstay typically rotates more than the chainstay as the suspension compresses, and so braking torque acts to compress the suspension more strongly if it is connected to the chainstay rather than the chainstay. This effect is known as anti-rise, and it explains why single-pivot bikes generally sit lower in their travel when 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 to the axle. Does it make a difference? Spoiler: No.

But exactly where the stirrup is mounted on a given frame element (seatstay or chainstay) does not matter. Yes, if the caliper is mounted directly in front of the axle it will apply downward force to the swingarm (as shown in this image of the article above), but this is canceled by an upward force at the axle; whereas if the caliper was mounted directly behind the axle (as in this scheme), it would pull on the swingarm, but the axle would apply the same force downward. (Imagine the wheel spinning without the axle installed, then pull the brake – the hub will come out of the dropout in the opposite direction to the force applied by the caliper).

So no matter where the caliper is positioned on the swingarm, the couple it applies to the main pivot is the same, and this is what determines the braking behavior.


Dial blocked RSC code?

Question: Gene158 request 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 worked great. However, about a week ago the contact point adjustment dial on the rear brake lever stopped working. I didn’t crash or hit it on anything, but the dial doesn’t spin back and forth now. I don’t know what could be the problem. Has anyone else encountered this problem?

great quotes It’s a fairly common problem. The ignition adjuster can become sticky and difficult to turn if it has not been used for a while.

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

SRAM’s official advice? “Absolutely DO NOT use WD-40 or other penetrating oil on your brakes, it will void the warranty. Using a petroleum based or aerosol based oil or lubricant will contaminate your seals and the brake could fail to The contact adjuster dials can get stuck when turned to their limits in either direction, but if it gets stuck somewhere in the middle of the adjustment, it would probably be worth disassembling the brake and clean everything.

If the ignition adjustment dial is stuck at the ends of the adjustment range, just use chain link pliers (it fits into the grooves of the dial quite well) and turn it gently. It should release fairly easily with the added leverage.

Wiley C. Thompson