Wooden feel front brake (NGC, but Brembo P08)

[Anders Pedersen]

Hello all,

This winter, due to wear and tear, I replaced the single front brake disc (non-floating) on my BMW for a new one, and put in new pads as well (EDC, sintered).

It brakes all right, it just takes a somewhat physical effort and i don't have much feel with what's going on down at the wheel.

Brakeline is steel braided, 4 or 5 years old and so is a rebuild of the caliper (new pistons and seals).

Can a faulty master cylinder cause such a symptom? Or will the feel of the brake improve as the pads bed in? (I've only ridden the bike, say 100 km's, after replacing disc and pads).

Best regards,

Anders


 

[Late to the party]

I'm going to assume you meant EBC sintered brake pads.

Can I ask why you went with sintered pads?

[Triple Jim]

Can a faulty master cylinder cause such a symptom?

Probably not.  The master cylinder can leak fluid, but it's unlikely it can change in a way that causes a wooden feel if it was working OK before.

Or will the feel of the brake improve as the pads bed in? (I've only ridden the bike, say 100 km's, after replacing disc and pads).

It could definitely improve with more use.  I've had new pads feel marginal at first.  A few hard stops may help speed up the process.

[canuguzzi]

Did you bleed the brake lines or just change the pads? Any chance you overfilled the masters? Could be as simple as that.

Do the simple: bleed the lines and carefully replace the fluid taking great care not to add more fluid that required. You can start out slightly below the full line.

Look at your masters. Sometimes they aren't level because of bar tilt angle and so on. Get them level and then fill if you can. If you can't do that, then fill to where the fluid touches the fill line at the lowest point and slowly get to just shy of half way, not more or you're putting too much fluid in.

Too much fluid, hard level pull and lack of feel.

[Anders Pedersen]

Yes, EBC!

Sintered for no other reason that I'm under the impression that's the recommended choice for that system and my kind of use. But I could be wrong?

No leaks, I'll try some hard stops next time out.

I bled the line, but I'll go back and check the level.

Thank you all so far!

[canuguzzi]

Yes, EBC!

Sintered for no other reason that I'm under the impression that's the recommended choice for that system and my kind of use. But I could be wrong?

No leaks, I'll try some hard stops next time out.

I bled the line, but I'll go back and check the level.

Thank you all so far!

added some to last comment I made for tilted masters.

[Chuck in Indiana]

Try this. Going slowly on a back road apply a little brake, add some throttle and keep applying brake as necessary to keep your speed the same. After about 30 seconds of this, let off the lever and don't touch the lever until the rotor/pads cool down. That should break the pads in.

[Anders Pedersen]

Look at your masters. Sometimes they aren't level because of bar tilt angle and so on. Get them level and then fill if you can. If you can't do that, then fill to where the fluid touches the fill line at the lowest point and slowly get to just shy of half way, not more or you're putting too much fluid in.

Too much fluid, hard level pull and lack of feel.

Went out to have a quick look-see. On the centre stand, front wheel pointing straight ahead, the reservoir tilts slightly to the front. Front of the reservoir, line of fluid is half a centimeter below "max", rear of reservoir line of fluid is one centimeter below "max". I doubt I've been overfilling.

Try this. Going slowly on a back road apply a little brake, add some throttle and keep applying brake as necessary to keep your speed the same. After about 30 seconds of this, let off the lever and don't touch the lever until the rotor/pads cool down. That should break the pads in.

Sounds quick and dirty to me :) I'll go out and try Chucks advice tomorrow, keeping all of the above in mind, will revert. Thanks again.

[nc43bsa]

The only time I experienced a Brembo with "wooden feel" was on a T3, and after inspection it had one stuck piston.  This is unlikely in your case since you have already rebuilt the caliper.

[mtiberio]

wooden feel is usually due to having a master cylinder with too large a piston diameter. Perhaps you have a single caliper on a master cylinder made for two caliper?

[Sasquatch Jim]

  New pads have to learn what they are supposed to do.  More miles and brake applications will help.

[stmike]

I had a wooden feeling on the linked front/rear on my California, so I bled them and apparently had a bit of air in the system.  All was good after that, problem cured.  But I certainly wouldn't discount any of the other solutions listed here.

[oldbike54]

 Change the brake fluid and hang the calipers above the master cyl. overnight with the bleeders cracked . The way BMW split the lines makes them difficult to bleed . Doubt if it is the pads , but be careful with those sintered pads , they will score the stainless steel rotors .

  Dusty

[Triple Jim]

Change the brake fluid and hang the calipers above the master cyl. overnight with the bleeders cracked . The way BMW split the lines makes them difficult to bleed .

Wouldn't you think a problem described as "wooden feel" would not be a spongy lever from air in the line?

...but be careful with those sintered pads , they will score the stainless steel rotors .

In my experience, the HH sintered pads are fine on stainless rotors, but in my case they are Kawasaki rotors.  Are BMW stainless rotors softer than the Japanese ones?

[Chuck in Indiana]

HH and stainless is fine as far as I know.

[Markcarovilli]

wooden feel is usually due to having a master cylinder with too large a piston diameter. Perhaps you have a single caliper on a master cylinder made for two caliper?

As mt said - had same problem and went to smaller master cylinder and noe have wonderful brakes.....

Mark

[Anders Pedersen]

Been busy with the brake today and these are my findings:

First of all, the pads are not sintered, they're organic, EBC FA18. I know because I bought the pair on the BMW together with 3 pairs still on the shelf to go on the Le Mans when the time comes. I beg your pardon for leading you on like that.

The only time I experienced a Brembo with "wooden feel" was on a T3, and after inspection it had one stuck piston.  This is unlikely in your case since you have already rebuilt the caliper.

Back then, I did change the pistons myself...  So I took the pads out, both sides showed wear, and both pistons moved freely. Just wanted to check this before employing Chuck's rather brutish advice of showing the pads who the boss man is :)

Try this. Going slowly on a back road apply a little brake, add some throttle and keep applying brake as necessary to keep your speed the same. After about 30 seconds of this, let off the lever and don't touch the lever until the rotor/pads cool down. That should break the pads in.

Well, I think it did the trick. Round 2 I nearly fell off the bike because the wheel blocked, it didn't do that in Round 1. I find it difficult to describe the change of feel, but it definitely is more easy to dose, coming on or off the brake. Result!

wooden feel is usually due to having a master cylinder with too large a piston diameter. Perhaps you have a single caliper on a master cylinder made for two caliper?

OK , what year year is this bike ? All of the BMWs that used the P08 calipers , except for R80 GS models , are twin disc , so unless someone changed the master cylinder it should match up .

It's from 1992, and I got it at a Danish Army surplus auction. Spares part list says it's a 12 mm piston for a single front disc/rotor, and I don't think the army bothered to fiddle with that.

Back in the day, the army had a 27 bhp version to use by dispatch riders, and a 48 bhp version for the MP's (both 650 ccm). Not knowing how comprehensive the detuning was, I bought one of the measly powered, cheaper version.

The odometer was broken, but the timing chain was so worn you could literally bend it sideways in a 90 degree angle. I had it repainted, had a mechanic put in a 308 degree camshaft and bought a pair of secondhand 32 mm carbs in place of the stock 26 mm's. Now it will run all day at 165 km/h, the final gearing is so low I think it's quicker off the mark than the Le Mans and I don't think I could break it if I kicked it. Nicely balanced, and a fun runabout!

Gents, thank you all for taking your time to reply to my questions.


/Anders