Front Brake Reservoir to Master Cylinder Hose

[Moto-Oopzzi]

Hi everyone, new member here. Shortly after purchase, the front brakes of my lowly non-LeMans V11 seized up on me. I’m rebuilding the front calipers and replacing the master cylinder and reservoir, but I’m not sure of the size needed for the small segment of rubber hose between the reservoir and the master cylinder. Since it’s for the brakes, I don’t want to mess around with a guess. Does anyone know the correct diameters? Included is the prerequisite glamour shot taken immediately after purchase. Thanks everyone. 

Edited October 31 by Moto-Oopzzi

[audiomick]

In case no-one comes up with a quick answer, I would take the old hose, cut it through the middle and measure it there. The ends will be deformed from the clamps and what-have-you, but the bit in the middle should have near-new dimensions, I would imagine. 

Edited October 31 by audiomick

[Lucky Phil]

On 11/1/2025 at 5:34 AM, Moto-Oopzzi said:

Hi everyone, new member here. Shortly after purchase, the front brakes of my lowly non-LeMans V11 seized up on me. I’m rebuilding the front calipers and replacing the master cylinder and reservoir, but I’m not sure of the size needed for the small segment of rubber hose between the reservoir and the master cylinder. Since it’s for the brakes, I don’t want to mess around with a guess. Does anyone know the correct diameters? Included is the prerequisite glamour shot taken immediately after purchase. Thanks everyone. 

Are you sure the front brake "seizure" wasn't caused by a mal adjusted aftermarket front brake lever you have fitted to the bike. You need to adjust the master cylinder piston actuating rod length to make sure there is enough free play in the lever or they will jam on when the brakes get warm because of brake drag.

[gstallons]

IF this "lever to piston" clearance does not exist you are having a hydraulic jack experience with your front brake system. There has to be adequate clearance to keep this from happening or you can replace all the parts you want and still end up with trouble.

[Scud]

If you are replacing all those parts, it's likely that the reservoir will come with the hose that feeds the master cylinder. It's not pressurized. I put Rizoma tanks on mine and they came with the hose and spring clamps.

If you have not already ordered new parts (or even if you have), it would be worth removing that lever to see if the adjusting screw that contacts the moving part of the master cylinder is set too far out (as alluded to above, I'm just trying to add a bit more detail.)

[Pressureangle]

Meh.
No, neither the reservoirs nor the master cylinders come with the hose- I just replaced both sides on my 2000 V11. 

The barbs on both the M/C and the reservoir measure 7mm, which comes to .275", or a bit over 1/4". 

I'll try this one- says 7mm but it states .280"... we'll see. 

https://www.amazon.com/uxcell-3-3ft-Rubber-Water-Black/dp/B08MZC17K2/ref=sr_1_4?crid=2N3UKYKJHFF5W&dib=eyJ2IjoiMSJ9.COxJ2-UzaKM-UA4iA0hK-rbkBQwPalfZ4tv7idlzCl17ZTbgr0ajtwiY0D_G5Xbw8i5AkGNQffBhn0wz67GG5n1fJRJtaDqYYOKs8mcmFDoENeVh49my-YIJs1YSqgxfmikbaouwO48WTcNtaIiAW5LzpVFkutMxoguSrzfCmAzGRYEmdHdLZaJzEXQiBX2BaeEqpzLl2A0kn7HjxGWGOjzPmzkyO7HwIpZSBsae6YA.wiX15ixR3X3b5S-vGyCtQkssKXjJOpFRP6tPh69lzow&dib_tag=se&keywords=7mm%2Bbrake%2Bfluid%2Bhose&qid=1762104388&sprefix=7mm%2Bbrake%2Bfluid%2Bhose%2Caps%2C147&sr=8-4&th=1

[docc]

These excellent folks sell the correct hose, yet I cannot find it on their website. Their reservoir descriptions simply say "black rubber hose."

My replacement, from OPP Racing, measures 5mm ID/ 10mm OD . . .

https://www.oppracing.com/

[Speedfrog]

@docc Would it be this ==> Brembo Reservoir Hose

[Pressureangle]

As much as I like to believe that OEM Brembo hose is some industry secret special sauce, more likely it's the same Chinese sourced stuff I'm getting on Amazon for half price. We'll see what shows up, how it fits, and whether I've wasted $6. 

[Lucky Phil]

5 minutes ago, Pressureangle said:

As much as I like to believe that OEM Brembo hose is some industry secret special sauce, more likely it's the same Chinese sourced stuff I'm getting on Amazon for half price. We'll see what shows up, how it fits, and whether I've wasted $6. 

The issue with non genuine reservoir rubber hose is after a while the brake fluid permeates the rubber and collects in a drip that runs down the hose and in some cases onto bodywork and damages paint. The hoses "sweat" brake fluid esp if the bike sits a while between rides. Genuine rubber hoses don't do this. It happened to my new DB1 Bimota years ago. During shipping the hoses had sweated and the result was brake fluid dripped onto the perfect Bimota paint work and damaged it. Not just my bike but all the bikes in the shipment. Bimota had used the incorrect rubber for the hoses. The importer had to repair paint and source the correct rubber hose.

Phil 

[Pressureangle]

14 minutes ago, Lucky Phil said:

The issue with non genuine reservoir rubber hose is after a while the brake fluid permeates the rubber and collects in a drip that runs down the hose and in some cases onto bodywork and damages paint. The hoses "sweat" brake fluid esp if the bike sits a while between rides. Genuine rubber hoses don't do this. It happened to my new DB1 Bimota years ago. During shipping the hoses had sweated and the result was brake fluid dripped onto the perfect Bimota paint work and damaged it. Not just my bike but all the bikes in the shipment. Bimota had used the incorrect rubber for the hoses. The importer had to repair paint and source the correct rubber hose.

Phil 

That begs the question, 'What is the correct material for brake fluid hose?' 

[Lucky Phil]

41 minutes ago, Pressureangle said:

That begs the question, 'What is the correct material for brake fluid hose?' 

Probably EPDM or Viton. I can't remember what I used on the Bimota but I think the importer supplied it as a replacement.

Phil 

[Pressureangle]

4 hours ago, Lucky Phil said:

Probably EPDM or Viton. I can't remember what I used on the Bimota but I think the importer supplied it as a replacement.

Phil 

So say we all. 

SuperGrok;

I need a hose to carry brake fluid, DOT 4, under no pressure. What is the most appropriate material for such hose to be made of? UV stability is important as a second property.

Thought for 23s

 

EPDM (Ethylene Propylene Diene Monomer) rubber is the most appropriate material for a hose carrying DOT 4 brake fluid, as it offers excellent compatibility with glycol-based fluids like DOT 4 while resisting swelling, degradation, or chemical breakdown.

 

quora.com +2

It also provides strong UV stability for outdoor exposure, along with resistance to ozone and weathering.

 

rubberandseal.com

Since there's no pressure involved, a basic unreinforced EPDM tube should suffice for transfer or storage applications.

 

reddit.com

Avoid materials like natural rubber or PVC, which can degrade quickly in contact with brake fluid.

[Pressureangle]

<sigh> McMaster-Carr has it as cheap as anyone, sure to be quality, and ridiculously expensive shipping. Well, I guess I can just replace all the hoses on everything I own. 

https://www.mcmaster.com/catalog/131/163/9776T31

[Speedfrog]

Why not just get the Brembo hose, that would eliminate the guesswork. 10 bucks for 1 meter(3.3ft for the metric challenged) you should have enough to cover a few bikes!