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Breva 1100 - rear brake

Gazdok

Gazdok

Cruisin' Guzzisti
Joined
Oct 27, 2008
Messages
134
Location
GB
The brake lever on my Breva 1100 seems to have increased the travel down before the brake bites. The brake still brakes o.k..... just later, I think. I have cleaned the brake recently and also had a look at the brake pads. They are still good and do not seem to have gone down much. The brake fluid is also o.k.
I do not think I have air in the line. Once the brake bites there is no sponginess in the lever. I have not removed the foot peg holder yet to look at the brake cylinder.
Has anyone noticed their rear brake having more travel? Any ideas if this is a problem?
 
Small amounts of pad wear, significantly increase the travel distance of the piston (I.e. necessary applied force) within the master cylinder in order to achieve the same braking force. It is not a linear relationship but rather an exponential one.

Although this is an arbitrary drawing the engineering principle holds true.

If we plotted pad wear in mm on the x axis (horizontal) and then the travel distance of the piston (i.e. necessary applied force) in mm on the y axis (vertical) to achieve the same braking force, the graph would resemble this curve.

IMG_3898.jpeg

I am positive that your “eyeball” evaluation of the condition of your pads is flawed.

Put a set of brand new OEM pads in it and you will immediately understand precisely what I am communicating to you here.
 
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Weeks later...

I also noticed that the rear brake seemed to be binding a little, i.e. it was more difficult to push the bike or just turn the wheel, the rear caliper was getting warm.

I have looked at the rear brake a few times, as in first just cleaned it first, the changed the brake fluid then checked the master cylinder - o.k. -, the took the rear caliper to bits expecting some corrosion - no corrosion at all - but I will need new seals for the rear caliper. I had a look online but they do not seem to be for sale.
Does anyone have a part number for the seals?
The bike is a Breva 1100 from 2005 without ABS.
 
Check that the brake lever is returning correctly, my Breva once had a small stone that became lodged in the mechanism and every operation of the lever it dropped lower and exerted more pressure on the pads.
 
I had the rear master brake cylinder apart today, foot peg hangers off and everything cleaned. There was a little bit of rust on the pushrod and inside the rubber below, but the spring action in the cylinder itself and the lever worked fine.

I then took the rear calliper off again and apart - just before my last post - and started to look for seals.
The smaller of the seals on the 28mm piston is quite frayed and there is some fraying too on the smaller seal on the 26mm piston.

I have "cleaned them up" for now. The bike is braking again and I think the loose rubber bits were the problem. In the long run I want to replace the seals but cannot get a part number.

I know that BMW has got a similar rear brake calliper on the R1200 range but I am not sure what the piston sizes are on them. I needed the little compression spring under the brake pads and found out that the BMW one was exactly the same and even cheaper than MG oem and I could just get it off the shelf at the BMW dealer.

Edited - it is the R850, R1100 r and GS range with 26mm and 28mm rear calipers.
 

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Got front brake caliper seals (B-11) from "Brakemaster" (dot com) in the UK last fall. They seem to only sell on ebay. Offer an amazing amount of kits for most bikes. Caliper fixed. Don't use their replacement bleed nipples. Kits include the small o-ring between the caliper halves.
In your back yard ;)
 
Late update.
Brakemaster were helpful, but could not supply the rear seals.

I tried the local MG dealer again and the parts guy's reply was:
"MG does have this - Brembo seals .... or any Brembo spares - as a separate part because Brembo do not supply brake spare parts any more after they lost a huge court case where a Ferrari Brembo spare had failed and caused an accident"........ . I was chuckling a little after hearing this. But he would have sold me a replacement caliper for £400 - not in gold though.

The rear brake caliper on a Breva 1100 and also on Griso, Norge and I think Stelvio are similar to BMW as said above.
I ordered a BMW seal kit 34212330311 with 26mm and 28mm seals. It helped a little as one piston was a bit dragging when pushing with a little force. The brake was still sticking though.

So in the end I thought that it could only be the master cylinder even though the action when removed was o.k. I bought a used Ducati one which is exactly the same as the MG and that solved the problem.
 
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