Brake MC restoration on early 105

[sprint750]

Hello,

Just digged out some forgotten stuff.

It is a stock of original Alfa repair Kits for 22mm ATE master cylinder, for floor mounted pedal+ brake booster.

Among all the stuff were some resleeved (bronze / Brass ?) master cylinder.

My question now.

The original MC features 2 channel for brake fluid.

- A large one (45°)
- A small one (90°), plugged by a soft alloy plug.



But the resleeved MC is only drilled on the large one.



What is the reason for this small channel.
Something that makes me wondering is that the new production MC also features this channel as the original version... ther should be a reason (bleeding, pressure rise...)

Repro (new manufacture)
Original (ATE)


Any idea among the brake specialists ??

Can I use safely the resleeved MC without any drawback ?? (I don't want to invest into an expen$ive new one = 180€ =250$ )

Any help will be appreciated

regards
sébastien

[ossodiseppia]

I'll take a run at this, but I am sure Papajam will pipe in and straighten me out if I am wrong. I think that vertical port is needed to lubricate the seal as it's pushed further into the cylinder. The vertical port probably needs to be drilled and the cylinder honed to remove any burs. However, I am not a fan of brass sleeved cylinders as they tend to wear faster than a steel sleeve. When they wear, they wear irregularly and can cause premature brake failure. If it were my cylinder, I wouldn't use it unless it's resleeved with a more durable material.

[papajam]

The small channel is called the compensating port. It's vital function is described in this thread. In short, without a compensating port in your sleeved master cylinder, the brakes simply will not work.

[ossodiseppia]

Quote:

Originally Posted by papajam The small channel is called the compensating port. It's vital function is described in this thread. In short, without a compensating port in your sleeved master cylinder, the brakes simply will not work.