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A wandering bite point can cause some serious frustration, ruining your hard earned descents. It is unsettling to say the least. Brakes need to be reliable, 100% of the time. We asked leading brake manufacturers, Hayes, SRAM and Magura, to shed some light on the matter. They pitched in on a couple other brake tech questions for us too. Time to get educated.

Why do some hydraulic disc brakes have a wandering bite point while others are reliable?

Hayes: We have studied wandering bite point and have a good understanding of what causes it. While I can’t give specifics since we consider it a trade secret I can say that in certain conditions pad clearance to the rotor is reduced while riding which results in a shorter lever stroke to the bite point. Higher ratio brake systems have a larger change in lever stroke from this compared to lower ratio systems and therefore it is more noticeable.  We have developed tests to recreate this phenomena and have implemented specific countermeasures in the design of Dominion to greatly reduce the occurrence.

SRAM: Basically it comes down to material selection based on fluid choice:

  1. The brake fluid you choose will ultimately determine which types of rubber compounds you can use in the brake system. The rubber has to be compatible with the fluid and not shrink, swell or experience other changes in the rubber properties with exposure to the fluid. With DOT fluid based systems, EPDM rubber is the most compatible compound. Mineral oil based systems typically use an NBR compound, often referred to as Buna. EPDM offers several distinct advantages:
    • EPDM has excellent resiliency when compared to other rubber compounds, which means that the seal returns to its original position very quickly after it is displaced. This is important, particularly in the caliper, because the caliper piston seals are effectively springs which pull the pistons back to their original position after the brake lever is released. Rubber with lower resiliency take more time to return, which can cause more variation in piston rollback, and therefore variation in the lever contact point. This is apparent when cycling the brake lever multiple times in quick succession, where the contact point will move further away from the bar with each pull.
    • EPDM has a broader temperature operational range than NBR and most other conventional rubber compounds. With so many different types of bikes available to be ridden in an ever-widening range of conditions, this becomes very important to the overall consistency of the brake systems performance.
      • On the hot side, having a higher temperature limit means that the material is able to withstand the heat generated by braking without melting, extruding, or leaking.
      • On the cold side. The low temperature limit is the point at which the seal material will basically freeze. Freezing means loss of squeeze and ultimately fluid leaking. The rollback consistency and resulting contact point variation will be worse at lower temperature as a result. EPDM maintains better resiliency at lower temperatures when compared with NBR.

2. DOT fluid has a much lower kinematic viscosity compared to most mineral oils. As temperature decreases, the viscosity of any fluid will increase. This results in flow restriction during brake applications, which can exacerbate the rubber resiliency concerns mentioned above. With a DOT based system, you are getting both the best fluid and the best seal option for consistency and performance.

Magura: A “wandering bite point” is a brake operating “not as designed.” Sometimes it is the cause of multiple piston caliper’s pistons operating independently due to piston seal stickiness or caliper alignment.

Also, the wheels/chassis can experience massive violence (rock garden, high G cornering etc.) causing brake pad “kick back” where the wheel and rotor flex laterally enough to reposition the pads within the caliper’s bores while braking.

In addition, there could be a hydraulic fluid flow restriction (kinked line, improper line fitting install, poor caliper alignment) which can produce a “pump” of the lever blade caused by the inability for the brake pad (really the piston’s quadring seal) to push the fluid back through the system fast enough when  the lever blade is released.

Incorrect fluid (viscosity) can also produce differing bite points and then there is the possibility of a mechanical failure and hardening of caliper or master piston seals.

Should I clean my brake rotors? If so, with what?

Hayes: Brake rotors do not require cleaning as the rotor and brake pads are designed to clear away any dirt, mud, and water from the braking surface. However, if the rotor is contaminated with by other materials like grease or oil then a thorough cleaning with isopropyl alcohol is recommended. In this case it is likely that the pads have been contaminated and need to be replaced.

SRAM: If your rotors are starting to look dirty you may clean them, but there is no reason to do so to improve performance. We recommend using isopropyl alcohol to clean rotors as it will not induce brake noise after a cleaning the way some detergents will.

Magura: Only if there is a need like contamination, otherwise leave it alone. We’ve always recommended something safe yet effective which is rubbing alcohol. You can of course use more aggressive cleaners like automotive brake clean but highly recommend removing the rotor so the excessively caustic cleaners don’t damage rubber components like brake caliper seals or the wheel’s hub seals.

What is the difference between brake pad compounds?

Hayes: Each brake compound is formulated with different targets for various performance categories like dry power, wet power, fade, speed sensitivity, pressure sensitivity, temperature sensitivity, noise, wear, and burnish. Setting the targets is a balance of giving up performance in some categories in order to gain performance in others. The constituents of the formulation are chosen and their relative volumes are adjusted to meet these performance targets. For example one compound may be formulated focusing on dry power while giving up noise and another compound may be formulated focusing on stable performance across speeds and temperatures while giving up peak power.

SRAM: Our pad offerings include the following:

  • The new Power Organic configuration developed for the new G2 brake – “Lunar” Grey backing plate
  • Quiet Organic pads – Black backing plate (currently used in Guide and Level brakes) – A good all-around pad, quiet, but not as powerful as the Power Organic version
  • Metallic – copper backing plate – Our most powerful, hardest hitting pad compound. Long lasting and great in wet and muddy conditions. It does create a bit more noise.

Magura: Metallic and Organic pads.  Metallic pads can last longer and provide a different “bite point” than the organic.  This is typically a rider based preference.

Do brake and shifter cables actually stretch? Or, is it just the housing systems compressing into their fittings? Please help settle this debate.

Hayes: Cables from reputable brands will be pre-stressed which means there will be almost no stretch in usage. The length change actually comes from compression of the housing. When a cable is under a tensile load the housing experiences an equivalent compression load. This can result in housing length shortening, especially in the bends.  “Compressionless” housing performs much better in this regard.

SRAM: Brake and derailleur systems can require readjustment after a new build due to housing end caps settling relative to the end of the housing once they system is tensioned.  Adjustments required after the system has been in use are usually due to the housing end shifting. Over time, a derailleur housing with too tight of a bend may force some of the inner strands to protrude from the protective layer, which can slightly change cable tension.

Magura: We don’t produce nor promote non hydraulic brake actuation. That said, the cable for shifting or braking doesn’t stretch and instead compresses the housing, ferrules and fittings. Often in a poor performing cable-actuated brake or derailleur system, the housing sheath has pushed back and revealed the metal lining that acts as a compression device inside of the ferrule and results in poor shifting (or braking) performance.

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34 COMMENTS

  1. So you left the brand who invented wandering bite point as a feature of their disc brakes, Shimano, out of this installment? Any of the ones you invited to answer here has a much better history than the Japanese brand. And to make it worse, Shimano doesn’t offer replacement parts for their brakes, out of pads and brake lines.

    If any brand on the Moto or Auto world would suffer such an elevated number of failures they would be facing a snowball of suing. Yet we as bikers are supposed to put up with disposable brakes, and in the case of Shimano, they won’t offer a recall of their products. Even when their representatives acknowledge in low voice how unreliable their servo wave brakes are.

  2. I have to ask, what does “wandering bite point” feel like? I ask because I have been using TRP, Shimano and Avid/SRAM brakes on various bikes since 2004-ish, and I have experienced the following:
    2004 XT – 4-finger lever will stop the bike in a reasonable span unless it’s wet or steep.
    2005-ish Avid Juicy 7 – Being chased by a turkey, but it won’t catch me because I can’t stop.
    2005-ish Avid BB7 – Made me want to switch back to cantis.
    2007 SLX – Stop better than Juicy 7 [low bar], not easy to bleed.
    2009-ish SLX – Stop okay, not easy to bleed, will corrode quickly in salty environments.
    2012 SLX – Stop great with metal pads and 203 rotors, easy to bleed, which is great because I have to do it monthly.
    2014 TRP – The turkey is chasing me again, and it’s going to catch up since these brakes stop well. PITA to bleed.
    2014 Saint – Too much power? Caliper can and will trap air unless bled VERY carefully resulting in a random lack of power. Otherwise good until the lever starts spitting oil, LOL.
    2016 XT – Really nice, could use some more power, consistent., great modulation.
    2017 SRAM Guide RSC – Nice feel at the lever, never need to bleed, quiet, OH NO I CAN’T STOP I’M GONNA DIE
    2018 XT – Really nice, decent power, consistent., great modulation, easy to bleed if needed.
    2018 XT 4-pots – Really quite nice, enough power for non-pro DH, consistent., great modulation, easy to bleed if needed.
    2019 SRAM Guide R – Nice feel at the lever, never need to bleed, quiet, Juicy 7 levels of power.
    2019 XT 4-pots – Too much power! Might need to downsize the rotors. Super easy to modulate.

    In all the above, the pads contact pretty consistently unless the brakes need to be bled, or it was below around -15C, in which case both the SRAM/Avid and Shimano brakes lost the vast majority of their modulation and either dragged against the rotor or were hair-trigger on-off. What am I missing here?

    • My 2014 Saints had it for the first year of their life. Then I took them off the bike, mounted them ‘upside down’ with the caliper in the workstand and the lever about 3 feet below it, then bled them in that position with an oversized reservoir of mineral oil attached to the lever. It worked beautifully, the brakes behaved great ever since.
      .
      I’ve done it for a bunch of other people’s brakes as well and Shimano calipers just seem to be evil little bubble traps. Once you’ve very definitely got the tiny little air gaps out of the caliper they’re great. If you don’t take the time to get every last one the performance comes and goes as they get hot, which makes sens if there’s a tiny bubble of expanding gas right next to the pistons.
      .
      Meanwhile the Hope X2s I bought in 2011 continue to work great on my hardtail and mock me for ever considering another brand.

      • I went the other way, with the caliper low and lever high, and cycled each piston in and out until that one solitary bubble made its way out through the funnel. Worked a treat after that. Shimano may have fixed that issue on the more recent 4-pot brakes, as it hasn’t been a problem on the XT calipers I’ve used.

    • 2003 Avid cable disc. Still going strong. Bit of a warble on the rear, change cables and pads from time to time. Admittedly, conditions here aren’t extreme, but with my Servo Wave levers, they’ve been great for years.

    • David, the dreaded wandering bite point is something you’d remember for sure if you had suffered it. Imagine coming hot into a trail feature, and needing to scrub off a decent amount of speed. You grab your brake lever the same way you’ve done it a thousand times in the past, and all of the sudden the lever goes straight to the bar. No stopping power, no modulation, nada. You start pumping the lever like crazy, until the brake miraculously recovers its power. Now imagine that happening over and over again, at random times, without previous notice.

      Odds are you never felt it because you weren’t going downhill with repeating hard braking situations (and please NO, I’m not calling you slow or low skilled, maybe your terrain or riding style just don’t include such situations).

      I broke a collarbone once because I ended up hitting a tree, after my XT brakes failed me without no time left for the pumping bandaid solution.

      The possible causes have been discussed thoroughly in several internet forums. For one, the calipers with non-ceramic pistons don’t suffer from this “feature”, which points to micro-cracks in the pistons themselves, as a result of thermal stress from repeating overheating and cooling cycles.

      Also, since Shimano does machine the inner bore of the master cylinder after anodizing, the MC piston will start ovalizing it and oil will pass through the seals. The ovalizing happens because the servo wave pushes the MC piston off center. I’ve seen a couple of XT/XTR levers with scoring in the MC bore so bad they wouldn’t push oil towards the caliper. You’d squeeze the lever and it would go straight to the bar with no stopping power at all.

      The worst pars is Shimano knowing all those defects in their products, yet putting generation after generation of the same basic design into the market. If you make a warranty claim, they just send you a new complete brake, or sometimes a brake lever/MC.

      • Ah, I see. I’ve experienced the dreaded “lever to the bar” on SRAM/Avid, Shimano and TRP brakes, although without the randomness that you note. If the lever is soft when I leave my house, it’s going to be consistently soft on the trail. In my experience, it just means that I’ve done a bad job bleeding the brakes. For context, I live in the front range of the Rocky Mountains, and all the riding around here involves climbing for 30-60 minutes, and then ripping back down. When I visit places like Squamish, Whistler, Revelstoke, etc., I end up doing the same kind of riding. In short, I use my brakes a LOT, and can’t say that I’ve ever had the same kind of unreliability you reference. Soft lever feel? Definitely, but that’s easy to fix with a quick bleed.

        • Hi David,

          I ride mountain bikes in British Columbia (North Shore, Squamish, Whistler, etc.) where the trails are steep and challenging and brake systems are worked hard. I am an ex bike mechanic and work on my bikes as much as possible.

          My experience of wandering bite point with Shimano SLX (2016) and XT (2018) brakes is having the lever throw decrease during a ride due to heat in the system. This is typically after a few minutes of normal braking during a descent and then at some point when the brakes are pulled the lever will stop its travel further out from the bar than normal. The brakes still work fine but it’s irritating to have this happen. After the system cools down the bite point returns to normal.

          Happy trails!

  3. So funny… SRAM and Magura want to justify their systems.

    Sram: DOT is sooo much better, thats why we are the only companie with it.

    Magura: Yes we have problem with the wandering brake pistons, but thats normal… isnt it!

    Personally i ride SRAM Codes RSC, never had a problem with it!

    The Magura MT7 is on my other bike, also a well working brake, except the pistons… after every ride you have to check the caliper if its in his right position…

    As well i have experience with the shimano brakes, old and new… and yes, that brake point wandering is so dissgusting…

    Waiting for the answer from shimano!

    • ^This. Their response is, of course, their opinion. Of course they have testing to back up THEIR product. That’s normal. Many elastomers can be formulated to work at low temperatures, just think of the -60C aircraft hydraulics are exposed to. Those use mineral type fluids.

        • I did detail why they are wrong. SRAM are being disingenuous about their poor brake fluid selection to justify their choice. Hayes and other competitors are switching fluids because they are willing to admit that using a solvent as brake fluid is mostly necessary for two ton cars but a bad choice for ten kg bikes. SRAM refuses to acknowledge that they made a bad choice and continues to parrot disinformation to justify it.

  4. I’ve heard a lot of people complain about Shimano’s “wandering bite point”, but I own and have owned many sets of their brakes, and I must have installed or serviced hundreds, and I don’t think i have ever experienced this phenomenon. The alternative is that i have felt it and I’m just completely oblivious, but frankly i doubt that.

    • Agreed. Never had an issue with wandering bite point on any brake unless the lever reservoir wasn’t full enough.
      That said, I live in Ontario, and we don’t know what an actual descent is here…..(riding the whole enchilada in Moab was eye opening).

  5. Not entirely on point here I know, but in my experience, Shimano is a pain in the ass to bleed correctly. Had no end of trouble using Shimano’s bleed kit to do Ultegra road. Bleeding SRAM, using their bleed kit, is an absolute delight – forcing fluid back and forth between master and caliper seems to effectively eliminate air from the lines, and I’ve never had bite point issues (not that I’m a brake killer). And in defense of SRAM/Magura etc, cars/motorcycles use DOT fluid for a number of reasons. Seems reasonable to use it on bikes as well.

  6. Commenting here to solicit input from the hive mind. I just picked up a barely used trials bike (Jitsie Varial 1010 disc), and so far the Magura T2 brakes with their blue organic pads have been a little underwhelming. I’ve swapped the rear rotor for a 180 and it helped a bit. Is there a disc brake out there, or a pad compound, that will give me braking similar to my old tarred rims and HS33 brakes?

    • It’s a little off topic but I’ll bite and offer this- how have you gone about bedding in the pads? This makes a huge difference in the performance of a brake. A completely fresh pad and rotor will have almost no power, a perfectly bedded in setup will be more than powerful enough with more modulation than a rim brake, and a poorly bedded brake will exist somewhere in the middle of this range.

      • Bedded in per manufacturer’s procedure, or as close to it as I could get. It’s not really safe to ride a mod bike at 20mph.

  7. Shimano the most inconsistent brake on the market.
    Luiggi, your comment nailed it. Good work bud.
    Hoses too thin (I was actually advised to use XTR hoses on road bike as standard are made thin to prevent less experienced riders locking wheels…..), seals weep oil if left standing for a few weeks, pain in the @ss for putting bike upside down for wheels on and bite point moving. Need bleeding every 2-3 months even if PERFECTLY bled. No feel/control.
    It is dissapointing that we didn’t pull in thier comments for this article.
    Shimano disc design for road bikes has very bad feel/modulation.

    Cheese, can’t agree about your comments on brake fluid. Clearly you never used Hope. At least brake fluid will burn off the discs/pad with no issues. Mineral oil, get your tools and wallet out. Combine that with Shimano’s little known feature of weeping piston seals has a good earner for them or bad brakes for you.
    Hope brakes – The gold standard. Expensive, slightly heavy. Every time i ride them on MTB brings a smile to my face.
    Put in pads, use bike. No maintenance. Take out pads when finished. Put in new pads…….same bite point, same consistency….repeat for 2-3 years. Totally rebuildable, and sometimes on the trail too. I even had a buddy put water in his reservoir when he ripped his hose out on a tree. Got him home with brakes.

    To be fair to Shimano, the icetech system deals amazingly with heat. I live in Taipei and it’s a struggle to cook a 140mm rear rotor on road bike. Go look at some of the mountains.
    Formula, i’ve almost given up bleeding them, my bike shop too. Refuse to own/work on them despite pleading of buddies. tried thier discs in place of shimano, great feel, no heat capacity.
    SRAM, i have not owned or serviced a set. My buddies who throw bikes at me havn’t made requests. That’s a good sign (unlike thier gears…)
    Magura, fine performance, but you pay. Can be finicky. Generally powerful. Hard to fix if go wrong.
    Hope, expensive outlay, best feel/consistency/reliability in market. Watch you don’t cook them so make sure phenolic pistons, pad choice and disc size.

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