Hello Vital MTB Visitor,
We’re conducting a survey and would appreciate your input. Your answers will help Vital and the MTB industry better understand what riders like you want. Survey results will be used to recognize top brands. Make your voice heard!
Five lucky people will be selected at random to win a Vital MTB t-shirt.
Thanks in advance,
The Vital MTB Crew
That's all interesting, but to reiterate my question in a shorter form: why not add more material until it stops breaking?
The fiber reinforced plastic Magura uses wouldn't handle tensile loads very well (compare to carbon fiber which has a fabric grid). No surprise that it breaks so easily from minor crashes. I had a set snap at the lever pivot on a trivial crash myself.
Back in the late 90s, I used to paintball a bunch, and had a gun that used a similar fiber reinforced plastic material for the grip/trigger frame. I had it snap off at the mounting bolts to the receiver one cold morning. I never saw that happen to any of the other brands that used aluminum for the grip/trigger frame.
As to why Magura uses it still, it's probably a combination of sunk cost and German-ness.
We should talk about the difference between static friction and kinetic friction. Basically, all friction is calculated using the equation of F (or N) times Mu, f being force, either from weight (the normal force, how much the surface you are on is pushing back against you perpendicular to its surface) or how much force you are putting into the surface and Mu being a coefficient that is dependent on the two material that are rubbing against each other. There are two Mus for every combination, one for static friction the force preventing slipping, and kinetic friction, the force once there is slipping. The Mu value for kinetic friction is always lower than the Mu for static friction which means that there is always more force required to start something slipping, than it takes to keep it slipping. With trials, most of the time brakes are going to be operating in the static friction area, so less force is required to keep the wheels from slipping. Trials bikes use pretty small rotors compared to most mountain bikes, I would suspect mostly because weight is a much more important factor for trials than all out power.
This is only looking at the forces between the pads and the rotor, so it doesn't cover every but of friction that keeps the wheels from moving, but it's a start.
Basically, a powerful brake is a brake that delivers enough force to the rotor, that the maximum static friction between the tire and the dirt can't exert enough force to keep the tire rolling, locking up the wheel. Tons of variables there, once we start considering different rubber compunds and riding surfaces, so we focus more in on how much force the brake can put out at the Caliper, not to mention heat management and how that power is delivered (modulation). Understanding braking is a blend of classical mechanics, fluid mechanics, material sciences, and thermodynamics all at the same time. I love thinking about this but for most people, pull on lever to stop wheel from moving is good enough haha.
because reducing weight is absolutely the most important thing on a bike and must be done AT ALL COSTS
That's a great question that I don't know the answer too. Maybe the cost, maybe weight, maybe it's a lot harder to mould. The only people who would know are magura
Funny enough, I work for Glock
Most users probably don't have any issues. The few that do sooner or later buy Shimano levers.
As to why not add more material, it's not the material itself, it's also what you do with it. You don't have aluminium bearing races, but it's fine for frames. You have to take care of the design and adapt it to the material you're using.
Mounting a structural plastic part to the bars is HAAAAAARD. Unless you want 10 mm screws either side of your bars and a 50 mm high master cylinder that is 100 mm long. Then it would probably work fine.
I'm using A4 calipers with HardHeaded Ram sintered pads and TrickStuff Dachle HD front/HS2 rotor rear, only noisy when wet and great stopping power.
See no need for the Hayes D rotors, except to just try them out maybe at some point.
My experience has been that Hayes rotors howl at a lower pitch than some, but just as loudly (when wet with metallic pads).
Question for the nerds, I dont have trouble with Brakes, generally ever But i picked up a bike with 4 piston XT m8120's(brand new bike)
I swapped out the pads to shimano metal(non finned) and Galfer Wave rotors (223 and 203) - ensured perfect alignment and equal piston movement to hit at the same time
Bedded them in via normal process on a hill i live on(like i do with every other bed in process)
Initially the brakes Grabbed really hard But after a couple of trails the perfomance fell off and was bad vibration, the Hummmm sound and could feel it through the bars - they still worked and didnt have that contamination feel or sound.(both front and rear)
checked pads, rotors and caliper and no oil or anything - went for anther ride and same performance, strong to start but heavy braking and vibration and performance falls off at same time
theres no oil from pistons or leaking etc 2 very high end botique shops(1 ex WC mechanic) checked them and they couldnt find an issue.
the pads and the rotors look perfect - it's so weird, they go fine but under heavy braking they vibrate and the performance falls off each time
Yeah that's pretty strange, a couple of questions-
Are front and rear equally bad?
Were the rotors new?
Are they bled with brand new fluid?
What frame/fork is it?
Yes, front seems worse but i assume from more braking load.
Everything brand new, I did a lever bleed only before i changed them out and to push piston back due to 2mm rotors.(used a brand new tyre lever)
latest Canyon torque CF with a fox 38.
Everything was clean and ensured Calipers were tight.
Looking through this, I have to ask if your rotors are center lock or if they are 6 bolt, and what they are torqued too? Chasing vibrations is a pain, but torque is a good place to start. Same thing with the caliper fixing bolts but I don't usually think they would be the issue. Resurfacing the pads and the rotor could also help, if they came out of the factories not as flat as they could be.
I would second the suggestion to resurface the pads and rotor.
I have tried this, I've even tried new pads and rotors(same) - Because I bought lots of these from a shop going under so have many years worth of Wave rotors.
6-bolt rotors, Torqued to Galfer spec which i believe is 4NM for the Wave's.
I use Wave rotors With Mavens with Zero issues.
switch to galfer pads, i had the same problem with finned shimano metal pads on m8120 with sharkfin discs.
Putoline HPX R 2.5 weight seems to be a popular fix in Europe for weird bleed related issues.
Interesting review from Dale Stone on Hope T4V4, i'd say i agree with everything said:
I liked his description of the power delivery being about position through the lever travel, rather than force applied to the lever. Great way to describe the feeling. Overall agree with the review, love my V4s
only one things is effectively wrong, the inconsistent bleeding is user error, just by looking at the membrane you can easily understand how you should roll it to not trap any air, and the opposite has been done, but agree on the rest, even if even the Hope statement that there's no difference between the normal hose and the braided one is bullshit, the latter is way stiffer and gives a much firmer bite point.
I have only used my V4 brakes with narrower rotors, but it works fine with the 1.8mm and 2.3mm rotors I have used. The vented rotors are way too expensive for a consumable part.
Both ends of the bike is really weird. I'd focus on the front and change things there. Will drive you less crazy to focus on one at a time and the front is easier to get smooth and quiet in my experience.
For whatever reason, and more commonly on the rear because you've got the frame involved, combinations of calipers, pads, and rotors just resonate and vibrate more easily. Sometime changing the type of rotor or pad will fix it for no real discernible reason. I'd try that if resurfacing and bedding doesn't work.
Good luck. I hate chasing sh!t like this round and round. Can be really frustrating.
I mean, this ain’t pinkbike, what’s the dislike for 😂
Did I hurt anyone feeling by saying the truth?
Alot of pinkbikers are now on vital aswell, which sucks.
a workplace saying now is: "the grass is greener on the other side because you are not over there F^%king it up"
You wrote a coupla interesting bits. To me it sounds like the pads may be sitting too low over the rotor, which may allow them to run on the rotor arms. Light-med braking may not create a vibe but harder pulls will as you may be getting a little bit extra stopping power each time the arm passes through the pad, and that extra bite causes the vibration. Check the rotor wear marks on the little triangle transition from the brake track to the arm and compare it to the wear mark that lines with the outside/top of the pad/outer diameter of the rotor. I've seen mounts that were off and AM rotors where the brake track wasn't 100% spot on with the brake. Additionally, the pad running over the arm in those hard brake actions can cause the pads to push back the piston ever so minimally, resulting in an inconsistent brake feel. If you can check to a stock Shimano rotor that would be ideal.
Another potential that would be harder to diagnose: inconsistent rotor thickness. Seen that back on old Hayes OG V7/178mm rotors and Tektros a coupla times. A slight high or low spot will change brake force and cause vibration. Worst examples can lead to a pulse in the lever blade during actuation. It doesn't take much, just a couple thousandths of a mm. That would be related to the grinding op at manufacture so would be considered a defect. Again, comparing to a stock Shimano unit would likely suss that out.
Next potential culprit is a bad bed in. Poor bed in can lead to inconsistent pad material deposition, which can create vibration. I don't think that's the case here, but it's worth mentioning. The second we think/act like we always do things right is generally when the time is ripe for us to prove ourselves incorrect.
I'd also suggest trying them with different rotors. I just swapped from Galfer Sharks to Waves on one of my bikes (to move the Sharks to a more desirable new bike), and noticed there's a LOT more vibration/feedback from the Waves. This is with Mavens & Galfer Purple pads. No noise, but it definitely feels very different.
Pinkbike is where you go to stir the pot, Vital is where you go for real discussion.
These are great suggestions. I've had the same symptoms in different instances on Shimano brakes because of a) caliper sitting too low on rotor and getting pulse/vibration from the pads hitting the six rotor spokes inside of the intended braking surface and another time from b) bad bed-in process that resulted in a little too much pad material left on one or two spots on the rotor, creating a bump and then vibration/howling. Both situations resulted in perfectly grabby brakes at first but then overheating and sub-optimal braking on longer descents. Problem A was solved by running a 1.5mm spacer under the caliper (203 rotors on 200mm PM) and in the other situation Problem B was solved by being extra careful to not lock up the brakes or even come close during the bedding process. I think the Shimano metal pad material can be perhaps too eager to deposit itself onto a new rotor, which can result in an inconsistent bump on the rotor, but that's a dumb uneducated guess.
Thanks. Been guilty of a bad bed in myself a couple times. I try not to throw suggestions out that involve throwing money at the problem without first fully understanding what the problem is. I was thinking about the Wave rotors a bit more. Those jobbers have awfully large cutouts in the brake track, which has me wondering if there's potential for the pad to 'fall' into the cutouts under harder braking events. That could create a vibration and again cause an inconsistent brake feel due to the pistons advancing and getting pushed back under each pass. But I'm not about to drop a hundred+ bucks to get a rotor to find out. That's something @noideamtber can check into easily enough.
If anyone feels like doing some science on this - you can tape your phone to a fork leg (most people have old smartphones lying around these days right?) and use a sensor app like sensorlog (iphone), physics toolbox or I think the arduino app to record vibration and speed - you can use FFT analysis (some of those apps have it built in) to get the frequency of the pulsing, which combined with the speed & wheel diameter you can figure out if it matches the number of spokes in the rotor
Post a reply to: Nerding out on Brakes shall we? Not another tech deraliment