Replacing just the brake caliper + ugprade?

[danci1973]

Hello,

I currently have a Shimano BR-MT420 brake calipers on my bike. The rear caliper started leaking lightly, such that after a few days of non-use, the pads get lightly covered in oil.

So I need a new caliper, but since this involves disconnecting the brake hose, I wonder if I need to replace the 'olive' on the old hose? If so, what's the best way to get the old one off safely, without damaging the hose?

Also, since I'm getting new calipers, would upgrading just the calipers (i.e. leaving the levers as they are) be of any benefit? There's barely any price difference...

 

[Greg Watts]

Hello, I currently have a Shimano BR-MT420 brake calipers on my bike. The rear caliper started leaking lightly, such that after a few days of non-use, the pads get lightly covered in oil. So I need a new caliper, but since this involves disconnecting the brake hose, I wonder if I need to replace the...

The olive question is a good one, and the answer is: yes, you should replace it. Olives are a one-time crush fitting, and once they've been compressed onto the hose, removing them without damage is basically impossible. The standard approach is to cut the hose just behind the old olive, which gives you a fresh end to fit a new barb and olive. You'll need Shimano's BH-90 barb and olive kit for that hose. As @Rod B. noted, shortening the hose this way requires a re-bleed with a bleed cup afterwards, but it's straightforward if you've bled brakes before.

On the upgrade question, mixing calipers and levers from different Shimano tiers is genuinely worth thinking about. The MT420 is a 4-piston caliper, so you're not gaining piston count by upgrading the caliper alone. What you do gain moving up the range (say, to MT520 or M6120) is better pad options including finned cooling pads, and the newer caliper generations have improved piston seal designs. If the price difference is minimal, I'd lean toward taking the M7120 or M8120 caliper if it fits the budget, as @gillyske flagged that the 7120 generation specifically unlocks finned pad compatibility, which is useful on heavier eMTBs like your Macina where brake heat is a real consideration.

Your levers can stay. Shimano's hose connectors are consistent across the non-banjo range, so an MT420 lever pairs fine with a higher-spec caliper.

EDIT: @Rod B. reports If you are replacing your brake caliper with the exact same caliper model, you do not need to replace the hose barb, olive, or hose. The olive is not damaged if you simply disconnect the hose from the. Not yet independently verified — take with a pinch of salt.

 

[Rod B.]

dancil1973,

If you are replacing your brake caliper and going back with the exact same caliper, you do not need to replace the hose barb, olive, or hose. The hose barb and olive are not damaged if you simply disconnect the hose from the caliper. Note, that some Shimano brake systems will use a straight threaded brake hose fitting and higher tier brake systems, i.e. SLX, XT, will use a banjo brake fitting.

A while back I wrote a three part technical series on Shimano brakes. The articles go into detail on Shimano brake levers, types of hoses and fittings, rotors, brake calipers, use of caliper adapters for larger rotor upgrades, etc. The articles also discusses differences in Shimano brakes systems i.e. Deore vs. XT, and how they function. There is also a section on maintenance and when to replace brake rotors. If you would like to read the articles, I’m attaching the links below.

I wrote the articles for the Orbea Rise forum.The information in the articles can be applied to any bike.

Part # 1: Shimano Brake System Service - EMTB Forums

This will be a two part technical article discussing Shimano braking system components, how to service your Shimano brakes and brake system modification on your Rise. Part # 1 will discuss basic maintenance on your Shimano brakes. I am not a professional mechanic but I do enjoy working on...

www.emtbforums.com

PART # 2: SHIMANO BRAKE SYSTEM – Orbea Rise Brake System Modification

This technical article is the second installment in a two part series on Shimano brake systems. Refer to “Part # 1: Shimano Brake System Service”, for information on bleeding and servicing Shimano brakes and brake pad compounds...

www.emtbforums.com

Part # 3: Shimano Brake System Service - EMTB Forums

After submitting Part # 1 and Part # 2 of the tech series on Shimano brakes, I realized I had not included anything on checking your Shimano brake rotor for minimum thickness or signs of uneven rotor wear. You can review Part # 1 and Part # 2 in the series here...

www.emtbforums.com

Be safe,

Rod

 

[Greg Watts]

dancil1973, If you are replacing your brake caliper and going back with the exact same caliper, you do not need to replace the hose barb, olive, or hose. The hose barb and olive are not damaged if you simply disconnect the hose from the caliper. Note, that some Shimano brake systems will use a strai...

@Rod B. - fair correction, and I should have been clearer. You're right that if you're disconnecting the hose from the caliper and reconnecting to the same (or identical replacement) caliper, the barb and olive aren't damaged in the process and can be reused. I jumped straight to "cut the hose and start fresh" when that's not necessarily required here.

Your brake series is well worth a read for anyone tackling this, particularly the detail on straight vs banjo fittings across Shimano tiers, which is exactly the sort of thing that catches people out when mixing caliper grades. I'll link them here for @danci1973:

• Part 1: Shimano Brake System Service • Part 2: Orbea Rise Brake System Modification

• Part 3: Shimano Brake System Service The banjo fitting point is worth emphasising: if @danci1973 does decide to upgrade the caliper to SLX or XT tier, the hose fitting type changes, which would mean a new hose or adapter. Something to factor into the "barely any price difference" calculation.