Shimano M447 vs M615/SLX brakes

[Craig Armstrong]

Hey guys, 

I'm currently rocking a Spez Camber with the stock M447 brake calipers and M506 levers. 

I really feel like my brakes aren't good enough. I'm pretty sure they're sufficiently bled, but they just don't have good stopping power. 

I don't have much frame of reference, so I don't know where I should be looking to upgrade. Calipers, rotors or pads... 

Are the M447 calipers known to be not great? Would M615/SLX brake calipers would be a significant upgrade? 

I'm currently using 180F/160R rotors. I'm not sure if I should move to 203F/180R rotors, or if 180F/160R should be good enough with the right brake set? 

Does anyone here have M447s and feel like they are good enough? I'm not sure where my issue lies. Could even be the pads, I guess 

Edited October 10 by Craig Armstrong

[nick_the_wheelbuilder]

Your brakes don't have Shimano's "servo-wave" technology which adds a lot of extra power.

I wouldn't try and upgrade either the levers or calipers, but go with a new brake set completely.

Even the Deore 2-piston brakes will be remarkably more powerful than what you have.

 

R3795 at the moment on Evobikes.

[Dexter-morgan]

That servo wave thing makes a difference but you can try other brake pads as well.

[Ruben101]

A new set of pads and good quality rotors should do the trick. Those calipers use the lower end shimano brake pads B01S or B05S. There is not a lot of other higher end pad options available for those calipers.

Bedding in the brakes properly also affects the performance 

[ajnkzn]

https://m.pinkbike.com/news/review-shimano-br-mt420-4-piston-brakes.html
 

If the 447 is part of the 420 model range, they should be plenty powerful and avoid the Servo Wave Wandering Bite Point ™️

 

It may also be possible to buy just a 420 caliper and put that on the front using your existing brake lever - the NSMB guys talk about it in this review https://nsmb.com/articles/ruminating-on-treks-1650-usd-1880-cad-roscoe-7/

Edited October 10 by ajnkzn

[117]

Im all for bigger rotors

Upsize the rotors to 203/180mm - you'll have to get a new mounting bracket for the front caliper to get the position correct to the rotor. Then, use the existing front 180 bracket for the rear.

Get new OEM brake pads (Shimano) on the new rotors. Set them nicely and you'll stop on a dime

Im not sure where you are based, but chat to @droo or one of the other LBS guys and get some parts. It'll take you all of 10min to do the changes and a butt size cheaper than a new set of brakes altogether 

 

[thebob]

I'd suggest getting the brakes properly bled and then sanding and cleaning the pads and discs to remove and glazing or contamination. Bed them in properly again and you should have a lot more power

Edited October 11 by thebob

[Chadvdw67]

18 hours ago, ajnkzn said:

https://m.pinkbike.com/news/review-shimano-br-mt420-4-piston-brakes.html
 

If the 447 is part of the 420 model range, they should be plenty powerful and avoid the Servo Wave Wandering Bite Point ™️

 

It may also be possible to buy just a 420 caliper and put that on the front using your existing brake lever - the NSMB guys talk about it in this review https://nsmb.com/articles/ruminating-on-treks-1650-usd-1880-cad-roscoe-7/

Wandering bite point is a poor bleed issue, myself and a few friends have Shimano Servowave brakes, they operate perfectly, but they need to be bled properly.

5 hours ago, thebob said:

I'd suggest getting the brakes properly bled and then sanding and cleaning the pads and discs to remove and glazing or contamination. Bed them in properly again and you should have a lot more power

Agree with Bob, a good bleed, not all shops can do it right, and then a good clean up of the discs and pads, I accidentally contaminated a set of pads on my last pad change, baked them in my airfryer at 200 for 5 minutes, let them cool down, and then took some wet sandpaper and sanded them while putting some isolropyl alcohol on them, and did the same to discs, then wiped them all down nicely with a clean rag and isopropyl, did the bed in procedure again, and my brakes have been epic since then 👌🏼

[droo]

The main issue with the entry level Shimano brakes is the cheap and nasty rotors. Swap those out and size up while you're about it, and you should be well on your way to better braking.

Failing that, the Deore 4 pot brakeset is about the best price to power ratio that I've found so far.

[ajnkzn]

Agree with the above.

 

I've embarked on a "downgrade" for 2025 and although they aren't world class, the MT200 brakes with resin only rotors and pads on my new bike are not terrible.

I believe that they're toxic in the wet, but on my trail rides so far, they definitely haven't been an issue.

Will ride them til the pads die and then likely do the front caliper upgrade to the 420 and a better disc.

 

[117]

@droo Speaking of upgrades, is it possible to upsize the rotors on a gravel bike? 

I run the GRX BR-RX400 calipers on 160mm rotors on a Revolt Advanced 2 frame. Any reason why I cant upsize the rotors to 180mm front and rear? (with the additional brackets for the calipers of course)

[droo]

Depends on the frame. If it's flat mount you'll only get 160s to fit, if it's post or IS mount you might get 180s in there. Maybe.

160s on properly set up brakes should be more than enough on a gravel bike though. Your tyres will run out of runway long before your brakes do.

[thebob]

Peak Torque (of YouTube fame) makes 180mm road bike and gravel bike brake adaptors

[117]

3 hours ago, droo said:

Depends on the frame. If it's flat mount you'll only get 160s to fit, if it's post or IS mount you might get 180s in there. Maybe.

160s on properly set up brakes should be more than enough on a gravel bike though. Your tyres will run out of runway long before your brakes do.

Its post mount on the front end. On the rear it looks like a 200mm will fit too as there is no pivot to get in the way of the rotor

With the amount of kinetic energy I generate, thanks to gravity, I will need bigger rotors .... 😏