Brake woes

[Don French]

Thank you for the “Long Winded response.”

It’s always good to be reminded about the how, what, when, where and why maintenance is important.

I’ll be rejuvenating the brake fluid on “Zippy” this weekend.

Ride on!



Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10



________________________________
From: GPZList <gpzlist-bounces at lists.micapeak.com> on behalf of Alexander Finger <af at genevainformation.ch>
Sent: Tuesday, July 2, 2019 5:33:19 PM
To: Don French
Subject: Re: Brake woes

thanks for the insight :)
I'll keep you guys posted about the progress, we're down to the south of
France next week with the Africa Twin and the GS750,. first..

Jeff Walker <walkerjl at charter.net> schrieb am Mi., 3. Juli 2019, 00:17:

>    Brake temperatures at the pads routinely get past 200C, or 394F. During
>    hard continuous braking, like going down a long hill at speed they can
>    get to 1000F. 200C is easily hot enough to vaporize condensed water in
>    brake fluid after heat transfer through the pad material and caliper
>    pistons. All it would take is for a micro drop of water to vaporize to
>    make the hydraulics feel spongy. Further, I've seen it happen on a
>    poorly maintained car before. The water always condenses at the lowest
>    point in the system, and that's also the hottest part of the
>    hydraulics, at the piston calipers.
>    Unless they've overheated routinely, it's far more likely for the seals
>    in a master cylinder to fail than a caliper piston seals. The
>    degradation mechanism comes from sliding wear, and the piston calipers
>    hardly move at all. The good news is that the master cylinder also has
>    the least contaminated fluid at it's seals, as the corrosion products
>    migrate down to the calipers. The counterpoint is that the heat at the
>    calipers causes hardening of the elastomers in the seals.
>    However, that being said, sticking calipers almost always stick in the
>    applied direction and fail to retract, vs sticking such that they
>    prevent the hydraulic force from squeezing the pads on the rotor. Or if
>    the seals are failing, brake fluid leakage is evident.
>    Otherwise a master cylinder seals can leak by and fail to produce
>    hydraulic pressure with no evidence of leakage. That's what happened to
>    my rear master two years ago. Very minimal brake force applied at full
>    stomp, then it would fail to retract when I took my foot off, and no
>    leakage. Rebuilt it and it's back to perfect.
>    In the last 130K+ miles on my GPz I've gone through several sets of
>    pads, but I'm still on the original calipers. I always bleed them
>    before and after pad replacement, as pressing the pistons back in to
>    install the new pads always frees up more gunk to be flushed out.
>    New brake lines are always challenging to bleed the first time. My
>    metal braided lines both connect at the master cylinder, each having a
>    straight run to their respective caliper and eliminating that "Y"
>    cylinder above the fender. Much easier to bleed that way.
>    Just goes to show the importance of preventative maintenance. I flush
>    and bleed the brakes on all my vehicles every two years regardless of
>    how often they're used. As a result I very rarely have any issues with
>    the brakes outside of normal pad wear. The rate of degradation of the
>    brake fluid is mostly time dependent, not mile dependent.
>    Sorry for the long winded response, but as a mechanical engineer that
>    specialized in maintenance, troubleshooting, and failure analysis of
>    far more complex systems I get interested in topics like this.
> ______________________________________________________________________
> GENERAL GPZList MAILING LIST INFORMATION:
> This is from the GPZList mailing list. GPZList at lists.micapeak.com
> http://lists.micapeak.com/mailman/listinfo/gpzlist
> You subscribed to this mailing list. Therefore, you solicited all
> mail that you receive from this list. Therefore, ANY mail that you
> receive from this list is, by definition, NOT Spam, and if you report
> it as such, you are violating the lists.micapeak.com terms of service.
>
> To unsubscribe, you may send email to
> gpzlist-unsubscribe at lists.micapeak.com
> ______________________________________________________________________
> YOUR PERSONAL SUBSCRIBER OPTIONS:
> Unsubscribe or choose new options at
> http://lists.micapeak.com/mailman/options/gpzlist/af%40genevainformation.ch
> You are subscribed at the email address AF at genevainformation.ch
> ______________________________________________________________________
>
______________________________________________________________________
GENERAL GPZList MAILING LIST INFORMATION:
This is from the GPZList mailing list. GPZList at lists.micapeak.com
http://lists.micapeak.com/mailman/listinfo/gpzlist
You subscribed to this mailing list. Therefore, you solicited all
mail that you receive from this list. Therefore, ANY mail that you
receive from this list is, by definition, NOT Spam, and if you report
it as such, you are violating the lists.micapeak.com terms of service.

To unsubscribe, you may send email to gpzlist-unsubscribe at lists.micapeak.com
______________________________________________________________________
YOUR PERSONAL SUBSCRIBER OPTIONS:
Unsubscribe or choose new options at
http://lists.micapeak.com/mailman/options/gpzlist/sirdondiego%40outlook.com
You are subscribed at the email address Sirdondiego at outlook.com
______________________________________________________________________