Inconsistent Brake Pedal: Crap then fine... Every press.

[JimF]

Got a ph2 172 with a braking issue.

Basically on first pedal press you get about half braking force no matter how hard you press. Second press however is great. Full braking force and good feel. This means that half the time you end up doing a pre-tap before applying the brakes.

Currently have no warning lights (had ABS lights but replaced both front abs rings) and plenty of meat on the pads. Have also bled the brakes tonight and no obvious air bubbles came out.

Any ideas? Thought bleeding the brakes would sort this but it hasn't and I've got a track day next week!

 

[JB21]

Does the pedal go hard after a few pumps with the ignition off, then with your foot still on the brake pedal sink down when the engine is turned over? If not could be a servo issue. TBH though it sounds more like air in the system.

 

[JimF]

To be honest from memory yes but I can't confirm it. Will check tomorrow. Where might this air be hiding? In the ABS pump requiring the computer to cycle it?
To add I took it out at the weekend and kicked its head in on some B roads and it the brakes consistently had this issue.

 

[Daz...]

Mine done this when the front wheel bearing gave up, turned out the disc was moving about.

 

[JimF]

I've just had someone on the Facebook group say that, strange but makes sense! Since I stripped it I got a bit paranoid about little noises as there were more than before but I've checked the bearings (two handed yank on all four wheels and rotated and checked for funny noises and movement) and all seemed fine.

 

[welshname]

Air in the ABS pump more than likely. You need CLiP to get it out properly.

Where are you located? I've got CLiP and it's a really easy procedure to do.

 

[JB21]

@JimF go out when you can and get the ABS to fire a minimum of 5 times, grass or gravel is easiest. Then re-bleed and see how it feels, if better but still not right do it again until right. That's how Ive got rid of air in the ABS pumps on 2 occasions now when switching out the pump.

 

[JimF]

Air in the ABS pump more than likely. You need CLiP to get it out properly.

Where are you located? I've got CLiP and it's a really easy procedure to do.

Thanks mate, I'm in Lancashire. Are you localish?

@JimF go out when you can and get the ABS to fire a minimum of 5 times, grass or gravel is easiest. Then re-bleed and see how it feels, if better but still not right do it again until right. That's how Ive got rid of air in the ABS pumps on 2 occasions now when switching out the pump.

Will try and give that a go, cheers mate. Only thing I will say is Ive never been able to activate the ABS before, but not tried on grass or gravel. Trying to think where there is some grass I can drive on!

 

[welshname]

Thanks mate, I'm in Lancashire. Are you localish?



Will try and give that a go, cheers mate. Only thing I will say is Ive never been able to activate the ABS before, but not tried on grass or gravel. Trying to think where there is some grass I can drive on!

Lancashire is a big place lol. I'm in Manchester. Depending on when your track day is I might be able to help as I'm off work next week but I'm moving house so early next week won't work

Sent from my Nexus 6P using Tapatalk

 

[BoatNonce]

Trying to think where there is some grass I can drive on!

Try your local school, they should have a playing field.

You might have to swerve about a bit to avoid the kids but this should also cycle the ABS pump too, so swings and roundabouts. You might want to avoid those too actually.

 

[JimF]

Lancashire is a big place lol. I'm in Manchester. Depending on when your track day is I might be able to help as I'm off work next week but I'm moving house so early next week won't work

Sent from my Nexus 6P using Tapatalk

True it is quite big lol. Didn't want to go for specifics if you were in Suffolk lol. I live near Blackburn but work in Walkden. I've managed to cancel the track day as I was getting stressed with the clock ticking so the pressure is off now.

Try your local school, they should have a playing field.

You might have to swerve about a bit to avoid the kids but this should also cycle the ABS pump too, so swings and roundabouts. You might want to avoid those too actually.

Actually lolled at that then!

 

[White16valver]

Just to check, you're not running 24hour-endurance-race-spec pads that take time to warm up? lol

 

[JimF]

Ha! Why, am I not supposed to?
J/K

As far as I know these are slightly uprated road pads, and previously had performed fine.