becave7

Hello.

I just installed Shimano hydraulic disc brakes on my son's older Stumpjumper FSR and noticed that there is no modulation at all on the front brake, but the rear is fine. They are either on or off with a very small margin on the lever. They are Shimano M445 brakes with resin pads.

Seems strange that they work too well. Reminds me of the older Magura HS33 rim brakes when fully pulled, Endo! But they really are on or off, no modulation at all.

FBinNY 

I may be wrong here, but it's hard to work on bikes through other people.

However, you sound like someone driving a car with power brakes for the first time.

To be clear, brake force isn't supposed to modulate with lever position, but with lever force. Even if the lever barely moves, the braking is likely proportional to how hard you're squeezing.

Before you take things apart and look for a fault, take it back out and try the brakes focusing on squeezing GENTLY, and noting how acceleration (braking) changes with lever force. Then ride it a while making multiple stops from various speeds, and at various rates. The key is to retrain your brain to relate to how these brakes work, so you are programmed to apply the brakes in such a way as to get the results intended.

becave7

Thank you for the quick advise, but I use VERY powerful brakes on my trials bikes. Try hydraulic rim brakes, that's what I mean and even they have more modulation. I have hydraulic disc brakes on many bikes and ride road, XC and all mountain all the time but have never felt brakes do this before. Trust me I know modulation and brake lever feel (rim cetner pull, side pull, canti, hydraulic disc and rim, cable, even coaster! , these nearly lock up immediately from mid lever to, well a literal touch beyond that.

This is a forum for discussing bike related subjects, and specifically, mechanics. Just a note on your first statement, please read my whole post. Not meaning to sound rude but that's what this forum is for correct? I very much agree that it is hard to figure out what people are experiencing online, but I thought I explained what is happening pretty clearly.

Cyclist0108

I can send you some pre-contaminated brake pads for better modulation.

But seriously, we recently installed XT brakes on an old mountain bike for my son, and noticed the same phenomenon. I attributed it to the larger front rotor (180 mm vs. 160 rear).

I think FB is just trying to help, and he has no way to know what your previous experience is.

becave7

Actually we've never really had much experience with resin brake pads before because this is NM and we ride in dusty conditions. Maybe contamination is causing this, but I've only seen less grip. They brake really well, just incredibly binary.

becave7

Forgot to mention we grind rims on the trials bikes with HS33's so we know brake power haha

corrado33

When I first rode proper hydraulics I thought the same thing.

Your hands will get calibrated eventually.

Cyclist0108

I use resin pads on my road bike. They are generally less grabby than the metallic ones. I have a set of metallic ones that seemed very non-grabby, and had to take them off and replace them with another set. I suspect they might have been very mildly contaminated, but they might just not have bedded in before I yanked them. I

becave7

No I literally just got of my Titus Motolite with XT hydraulic brakes, same size discs with perfect modulation that I ride all week. No something about getting used to, or calibrating feel.

We searched for a while online for this exact problem and did not find an relative information or solutions. I'll figure it out. Not sure where I didn't explain that we ride all sorts of brakes, including hydraulic disc brakes.

FBinNY 

No need to get upset. I don't know you from Adam, no idea of your bike experience, and no basis on which to draw any conclusions.

So all I have is your reference to the lack of modulation, with references to lever movement, but have no frame of reference to gauge the info provided and put it into perspective.

That's why I tried to cover what I thought was an important possibility, and prefaced it by saying I might be wrong.

So, instead of getting upset, you might have simply filed it away, and assigned it the value you paid for it.

corrado33

Don't get too upset. FB assumes everyone posting bike mechanics questions on a forum is an bike noob. He's usually not wrong. All we can do is throw out possibilities for what it COULD be. You are in the best position to diagnose and fix it.

FBinNY 

Actually, I try to assume nothing. But, I find things are worse if I overestimate OP knowledge than if I underestimate it.

But you're right, all we can do is offer possibilities based on the info given, and given the nature of a forum, try to throw stuff against the wall and see what sticks.

We're all also constrained by the limits of language between strangers. We know the words, but shadings of meaning can vary greatly.

gsa103

The lower end Shimano don't have the same feel as the upper tiers. I'm not sure what the difference internally is, but they don't feel the same. It's probably something simple like lever ergonomics.

becave7

FBinNY. I'm not upset at all and tried to not sound that way but it's hard online, haha. Just was confused why you responded that it was like I'd just ridden power brakes for the first time, when I had clearly stated that I ride Magura HS33's (they can crush a rim if not build well, and have good modulation)

These are definitely not high end brakes but we have the exact brakes on a DiamondBack Lux Comp and they are very smooth throughout travel are plenty powerful.

It was very very hot yesterday and I wonder if that had an affect on them, as we were riding in the evening just as the sun was setting. I've had issues with my old Maguras when the bike sat out in the sun most of the day. But these are nearly digital, on or off.

Thanks for the help all. I think we will clean the master and slaves, just to take dirty pistons out of the equation.