Poor braking from 11mm MC

[Sci85]

Hey guys, I put an 11mm front master cylinder on my build using the stock single piston caliper. It works, but requires way too much lever travel and doesn't feel very powerful at all. I'm running a drilled rotor and stainless one piece hose. I got the 11mm MC from a Zuma and noticed that the caliper piston on the Zuma is much smaller than the XS one. Could that have something to do with it? I thought the 11mm bore was the hot setup for the single disc rotor but doesn't feel good at all. Is anyone else running an 11mm bore MC with the stock caliper and if so, how is it working for you?

 

[gggGary]

If the caliper and master cylinder have been rebuilt and are functioning correctly you are not done bleeding the system. There are lots of complicated "sure fire" bleeding techniques out there but this is my goto. Make sure you have an uphill path from caliper all the way to the MC reservoir. Usually on the side stand, bars turned full left is enough but some times you have to loosen or remove the MC to get it angled up at the outside. Got that done? Good, now this is the hard part! Put down your tools, walk away from the bike, check hardness in an hour or so. That should do it.
PS
I am running a 10mm MC from a TW200, SS line, stock single piston caliper It has about the same or slightly less lever travel as a stock system ( I have both stock and modified bikes and ride them back to back) and I love it.
PPS no matter what the seller said any used MC needs to be stripped and cleaned.

 

[5twins]

I guess that's what they mean by "better braking feel", lol. I've heard the smaller MC does give more lever travel and a softer "feel". I wouldn't know, I still use an original and I think it works just fine. My lever pulls in about 1/4 of the way and then gets very hard. I guess that's what they mean by a "wooden feel". But, the harder I pull on it after that, the harder it stops.

I've thought about trying the 11mm MC but I don't want to pay a lot of money for one. I'm afraid I might discover I don't like the "improvement", just as you have.

 

[gggGary]

On the caliper rebuild also check the slide pin that is part of the mount. If that doesn't move freely it creates a soft lever. Gunk behind the caliper piston seal does that also.

 

[fredintoon]

I guess that's what they mean by "better braking feel", lol. I've heard the smaller MC does give more lever travel and a softer "feel". I wouldn't know, I still use an original and I think it works just fine. My lever pulls in about 1/4 of the way and then gets very hard. I guess that's what they mean by a "wooden feel". But, the harder I pull on it after that, the harder it stops.
I've thought about trying the 11mm MC but I don't want to pay a lot of money for one. I'm afraid I might discover I don't like the "improvement", just as you have.

Hi 5T,
try it, you might like it.
And if it turns out that you don't like the way it feels at least you'll KNOW you don't and could sell the
11mm M/C on to someone who would be glad of it because they ain't got Hellboy's gripping strength.
Then you'd be richer in experience, breaking even on the resale and only out of pocket on the shipping.

 

[5twins]

Oh, I do look on eBay from time to time for a nice used TTR or TW 11mm MC. If I can find one for $20 to $30, I may indeed try it. It will require another Banggood brake line with ends oriented in the same plane, but they don't cost much.

 

[Sci85]

Well, I did rebuild the caliper and put on a new SS line but the MC was really clean. It didn't need a rebuild. It may have even been new. I've bled it good and done the "pin the lever to the handle bar trick overnight". I may open it up again and try over.

should the 11mm have a lot of travel or little? What's the actual pressure like to stop? I've got lots of travel and lots of pressure needed to stop this thing. No bueno.

 

[5twins]

Did you pull it apart and look inside? Clean on the outside means nothing.

 

[gggGary]

Be sure to check the tiny second port from reservoir to bore in the MC, the smallest little bit o crap will plug it.

 

[Sci85]

Did you pull it apart and look inside? Clean on the outside means nothing.

Yes, I looked inside. It looked new. Very clean. However, with that said, you never know. I will disassemble and double check everything.

Dang for some reason this bike has more gremlins than any I've done to date.

 

[angus67]

How clean is the inside of the caliper? Break fluid gells up. There could be a ring of gunk just behind the o ring, not letting the piston slide good enough

 

[Sci85]

I cleaned and rebuilt the stock caliper. Clean as a whistle!

 

[grizld1]

Been using 11 mm. Brembo MC with 77-forward stock floating caliper for years. Big improvement. If bleeding doesn't help, remove the line from the MC, thread in a solid bolt to plug the hole, fill the reservoir, and pull the lever. If the pull isn't rock hard, you have a defective MC.

 

[gggGary]

blue bike all stock brakes
off

all slack out

Squeezed hard

Red bike 10mm MC ss line
off

All slack out

Squeezed hard, this would be past locked up tire pressure.

Note both levers have an adjustment screw, and are set so "lock up" ie max brakes is near the bar for better hand leverage. I did a similar mod on my Royal Star Venture recently but went from 4 pots to 8 pots and from a 17mm MC to a 14mm, huge improvement. I think lever pressure is now less than the XS. I had to change the MC to an adjustable lever. Hard lever was too far out for a comfortable grip and squeeze.

 

[MaxPete]

Hmmmm....Sci85. - is your adjustment screw set at a reasonable position?

 

[Sci85]

Ok this all helps. I will look things over carefully tomorrow and try the bolt trick mentioned by grizld.

I'll also take some pics as gggary above. But, Gary, when my lever is almost to the bar, there's still not much stopping power. Maybe the pads I have are crap. What do you guys recommend for pads these days for these bikes?

 

[Sci85]

Hmmmm....Sci85. - is your adjustment screw set at a reasonable position?

Yes, and I've adjusted it a couple times for more and less slack trying to get a better feel. I'll post up some.pics tomorrow.

 

[MaxPete]

OK. It occurs to me that if you can squeeze that lever nearly to the bar, you've either got air in the hydraulic line or your pads may be too thin.

Anyhow - looking forward to more data.

Pete

 

[gggGary]

Sci85don't know what pads you have BUT any pad that has been contaminated by fork oil is toast there is no recovering an oil soaked pad.
My red bike has ferodo's in the compound sold by 650 central squeezing a MikesXS rotor. The other has "no name" cruizinimage pads squeezing a stock rotor that I sanded smooth, that works fine.

 

[gggGary]

It is also possible to glaze a set of pads creating poor braking. (I've done it) But from your description you have an issue with bleeding or some other component that isn't functioning properly