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This is my first time dealing with hydraulic brakes.

The front brake on my bike is Shimano BL-M4100 lever with MT410 caliper. I stripped the lever's clamp thread and going to replace the lever with a new BL-M4100.

I have a new lever and a bleeding kit from Amazon. Looks like I have all the necessary tools, but I don't have a new olive and a connector insert. Would it be OK to just unplug the hose from the old lever and plug it into the new one? Or is it likely to leak and I should better get a new olive and a connector insert?

Thanks!

3 Answers 3

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No one can say what you should do, just make a recommendation. Recommended option is to get a new olive and barb, do it right, do it once.

If you have problems sourcing these in the time frame before you need to ride the bike, you could have a crack are not replacing the olive and just swap the hose to the new lever. Don't however be tempted to over tighten it to get it to seal - you could end up needing another new lever. If the brake leaks you will need a new olive and barb, cut the old ones off and start on a fresh end of hose. Make sure it is not leaking before heading out on any big rides (but you want to do this even if you use a new olive).

With care and a bit of luck, you may be able to do the swap without needing to bleed the brakes.

Note: Shimano have two different barbs. Make sure you get the correct barb for the MT410 hose, which is BH59.

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    My guess is that the new lever has a fresh olive in it. Last time I bought brand new levers (GRX 400), they had olives in them. I didn't discover this until after I called in some favors with buddies and bummed some olives they had lying around.
    – Paul H
    Commented Dec 26, 2023 at 17:27
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New olive - definitely. New insert (barb) - I do not see the point. You won't be able to get the old one off anyway, unless you want to cut the brake hose.

Bleed the system from the bottom up.

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  • Disagree on bleeding from the bottom up. If there's any contamination in the in the hydraulic fluid, it'll be near the caliper. You don't want to push that contamination up towards the lever. Do a gravity bleed (top down) first, and after fresh or at least clean fluid is coming out, then bleed from the bottom up.
    – Paul H
    Commented Dec 26, 2023 at 17:25
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    After getting some hands-on experience with it, I believe it's impossible to replace just the olive, because it sits there super tightly. I kept the old barb/olive for now. If it leaks, I'll cut off the hose and install the new barb and olive. Commented Jan 1 at 21:40
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I replaced my shimano m4100 brake levers with m9100 xtr levers. I just swapped them out with the same brake hoses olive and barb. no leaks. I had to bleed both front and aft brake systems. I used the reservoir cup syringe brake bleed kit.

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