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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.
Just sold my XT 4 piston brakes recently because I just couldn't take it anymore. I also did not find any leaks, and yet it felt as if I used contaminated rotors/pads.
I bought my bike brand new with these brakes fitted. They came with the xt icetech rotors and finned metallic pads. The bite started dropping gradually, and I did a full flush and bleed for the next season given the brakes felt like mush.
After the service they felt better, but not great. I sort of just stuck with them for that season as well, but the following season I decided to try new rotors and pads, in an attempt to isolate and narrow down the problem. I mounted 2 x 203 galfer wave discs and tried their standard G1053 pads to go with them. I did a full flush and bleed(the sram way, no gravity bs) and also made sure to clean the pistons etc.
After the inital bed in session that I do just in my neighborhood, they felt super grabby and I thought that I've solved the case. To my big disappointment, the bite dropped significantly after just one ride, and I couldn't get that same feel back again.
Not only did the bikeshop not touch my brakes and outright ignored my claim of brake issues, but I just could not fix the problem that I still do not know what caused it. I also never used screwdrivers or any other funky tools to twist and bend the ceramic pistons back in. I used a Birzman brake piston pusher to evenly spread the pistons out, and I did this every single time and no other mechanic had touched them.
That's why I just have a hard time thinking the pistons had cracked, when I as well never managed to even find them leaking.
Not only all of that, but the fact Shimano doesn't sell all internal parts for their customers, is a big F you, which means I refuse to touch any Shimano brakes again unless they do a full 180 and fix all their issues by redesigning them all together. Shimano are plagued with wandering bitepoint issues, and it's such an annoying reoccuring "feature" to be plagued with.
My advice for you is to get rid of these brakes while you can, and just find a better option. It's an utter pain to have issues without knowing how to fix it, and certain things unfixable.
PS: Be careful using tirelevers to pry pistons back in as these brakes use ceramic pistons which can easily crack. Lots of users have managed to crack their pistons, and they are NOT available as a sparepart from Shimano. Going for 3rd party pistons that may have even worse tolerances is just a route I never even wanted to consider.
If you crack those pistons, I'd rather just sell them as-is and be up front and honest with who ever wants to give you a few quid for them.
EDIT: When I think about it I did start to get some vibration/rubbing on my front brake, and I thought initially the pads did not clamp onto the disc where it should, but the brakewear was identical front and rear, and it could not have been more perfect at least visually. One of my rotors was slightly bent right out of the box, so I used a disc prying tool to bend it back into shape, and I got it straight as an arrow again.
I cannot really say I know why it happened and I never got to fix that either, so I found it odd you as well got the same thing with the same brakes and rotors.
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
How do you know what mount will suit the dropper lever? I see so much offerings for shifter type, and I have found I-spec EV for my shimano shifter so thats fine, but what about my Fox dropper? I remember it was just attached to the underside of the Shimano brakes I sold, and I still have the bolt and "nut" attachment. How do I know what else that can fit?
So, I see for example Hope have their option https://www.bike-discount.de/en/hope-tech-4-shimano-shifter-ev-mount?number=20123239-40333770 that you can mount either left or right for the shifter, but how do you know in advance which will work for you when a new lever may easily be mounted at another spot on the handlebar, so you don't really know if you need to push the shifter to the right or left?
This is the Shimano mount with the left offset and I have the shifter pushed all the way left also. The brake lever clamp band is about 25mm from the grip clamp and the end of the thumb lever on the shifter is level with the end of the grip clamp. I would think the right hand offset mount will put the shifter too far outward for most people.
On the other side I have a OneUp lever mounted to a separate clamp on the inside of the brake lever clamp band, which gives a similar position for the lever, maybe a little further away from the grip. Not sure how much distance there is from the Fox dropper lever end to the mounting point, but if you compare it to your shifter you should get an idea, my guess would be that you need the right offset mount for the dropper, but not 100% sure.
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.
For me it seems like they refer to RH for the side of the handlebar(even though it is on the left side of the clamp) and that this should be the recommendation which is the option I see you have went for. Then they show that you can use the LH version if you want.
To my understanding now I must have I-spec EV on the FOX dropper as well as they have the same shape on either side. I just thought I-spec EV was Shimano so it could not be anything but their shifter.
That must mean I should use I-spec EV for both sides, and only decide on offset which seems to be just to pick one left and one right if I've now understood things correct?
it can be a tricky one depending on how far in you will keep the brakes, and what dropper lever/shifter you've got, in my case it had to be 2 LH sram mounts
Ok, good to know. Seems like I'll just have to go with 1 left and 1 right, and then I can at least try both on either side. Hopefully it will be enough. Will have to test fit the new cockpit anyhow, so we'll see how it goes.
Good to see other images for reference at least 👌
Personally I would never really benefit from their 3.3 mm rotor so the E4 caliper would suit me better. On that bombshell I see that Sinter only offer pads for the V4 caliper, and I'm a bit at loss. This time around I'd like to start off with some new pads as well with all new brakes, and want to try that brand.
I see that you can just fill the system with more fluid to accompany for a thinner rotor paired with the V4 caliper, but is that really a viable option for the long run? Doesn't that just mean the pistons will always be pushed out a bit to be able to be close enough to the rotor?
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.
Yeah price is another thing, but personally I'm a normal trail rider so I have no need for extra cool running discs. So for me it's just overkill.
Well if you're actually using them with thinner(normal) rotors and have good experience with that then perhaps I'll just have to go for the V4s instead.
I have found complete 3d printed kits on Ebay for the service items they don't offer and that thinner bleedblock they call caliper tuning tool so...
Tech 4 V4 with Sinter green pads and Hope floating centerlock (1.8mm) rotors seems to be the ticket for me this time then.
I thought I was the only one!
I run two lefts as well, but with different brakes and levers. Definitely consider something like this if you're struggling to get lever in the right position and punting to seperate clamps won't work. If you're going to punt to separate clamps, look at BikeYoke.
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.
Been running the T4 V4's with Freeza rotors for a season now and have been pretty darn happy. Personally I didn't bother with the thinner bleed block as I finish my bleeds with a lever/cup bleed with the wheel/rotor installed in the caliper to make sure there is the correct amount of fluid in the system. Haven't run into an issue with this setup/technique so far.
I mean, this ain’t pinkbike, what’s the dislike for 😂
Did I hurt anyone feeling by saying the truth?
That’s why it’s nice to run 2.3 rotors on the v4
Between the lack of braided hose and the less power it would be a no go for me
The 1.8 I reckon they’re too thin in general, if they say it’s fine I’d believe them, but for sure I’d try to run 2.3mm
At the same time I’ve got friends using them with 1.8 hope rotors or 2mm Maguras with great feel and no issues for years, so either option will be good, the vented are not a necessity especially given price and weight
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"
I'm actually looking at the TRP RS05E right now which is 2.3mm and in the diameter I need. The only reason they went under my radar is they are only offered in 6 bolt pattern, and I've been zoomed in on centerlock. I'd rather be without an extra adapter, but those look like to be the best middleground for the V4 caliper right now after a bit of scrolling up and down lots of different websites.
That’s exactly what I run
Your fox dropper lever is matchmaker compatible. The matte black part is actually the adapter from matchmaker to I-Spec EV for the XT brake you were previously running. Every dropper lever on the market is matchmaker compatible except the wolftooth (use a smaller matchmaker alike interface that works only with wolftooth adapter or clamp) and Shimano own dropper lever (I-Spec EV).
Ok, but all I need to know is if it means I should order I-Spec EV for the fox dropper as well?
Here is what Hope offers that is I-spec EV and I just need to know if I just order that for both shifter and dropper, or what I then would need in order to attach the Fox dropper to a Hope Tech 4 lever:
I see a few comments on the internet stating that I need an SRAM adapter for the fox dropper, and that looks like this:
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