spngey brake pedal

SkodiRS · 24-02-2004, 10:00

Right....now that I've maanged to post this in the right place.

Can anyone explain to me why when you change your brake disks and pads you get a spongey brake pedal feel.

Is it due to air getting into the system?

Would be interested to know why it happens and may be then I can reduce the probability of it happening when I do my brakes.

Cheers.
Adrian.

SimonT · 24-02-2004, 10:10

I don't know, but my best guess it that it feels "spngey" (

) because you are used to making the pad move a fraction of a mm until all the pad surface is in contact with the disc. A new pad doesn't have a flat surface (compare it to a pad you're taking out) or the correct "angle of approach" (we're talking fractions of mm's - the pad WILL be slightly mis-seated) so part of the pad makes contact, but only a small part so you apply more force which persuades more of the pad into contact.

Eventually the pad wears smooth and to the correct angle, so you're back to normal.

<waits for expert answer>

redbaron · 24-02-2004, 10:11

Quote:

Originally Posted by SkodiRS

Right....now that I've maanged to post this in the right place.

Can anyone explain to me why when you change your brake disks and pads you get a spongey brake pedal feel.

Is it due to air getting into the system?

Would be interested to know why it happens and may be then I can reduce the probability of it happening when I do my brakes.

Cheers.
Adrian.

change of discs shouldnt let air in... but would be worth hammering the abs a bit... and then bleeding them... top up with super 4.1 fluid just to be sure...

Tavia4x4 · 24-02-2004, 10:38

Yup, sounds like another with air in after a change - god knows how it gets in as we always seem to get it!

Find a low grip \ zero grip surface, ice, grass, anything with nothing to hit

Go as fast as you dare, slam on the pedals and get the abs firing for as long as possible, this pushes the fluid through all the chambers.

Check and top up afterwards.

SimonT · 25-02-2004, 09:56

Anyone with any more suggestions? I still can't understand how air gets in the system.

Fatbloke · 25-02-2004, 10:29

I don't believe air is getting in. It will be the pads bedding in. Until the surface is worn to match the disc only high points on the disc and pad surface will be making contact and this causes a slight loss in performance and a spongey feel. Bed them in gently and after 100 miles or so they will feel like normal.

SkodiRS · 12-03-2004, 08:37

Now done front discs and pads all round.....did initially have a spongy pedal but it's gone now.

After a slight technical hitch pointed out by Obi Wan French (

....it make such a big difference it's unbelieveable) braking is much improved and I'm sure will get better with further usage.

Free tip of the day: get the brake winding tool or someone to lend it to you.....absolutely fantastic bit of kit and so easy to use.

**TaviaRS** · 12-03-2004, 08:45

Live and learn Adrian, live and learn

Always happy to help.

Glad you bought the wind back tool now are you? Best £15 I spent, can do both sets of front pads in under 20 minutes now and that includes removing and refitting the wheels

piv34uk · 12-03-2004, 09:23

when changing brake pads the rubber brake hose should be clamped half way up with a pipe clamp..NOT MOLEGRIPS..the bleed nipple on the caliper should be undone before the piston in the caliper is wound back in...this stops any dirt from entering the master cylinder and is ejected through the bleed nipple.......pressure bleeding is the only way to fully elimanate air from the system................

brake fluid is hydroscopic which means it absorbs air and water (moisture) every time you drive...mainly from the kerbside because that is where most water settles......you can buy a device to boil the fluid in the reservoir and it will tell you the boiling point....for dot 4 and 4.1 the minimum is 180c anything below this requires changing....

the more water content the quicker it boils....catch the jist?????????

sharp intake of breath

Phil

Lummox · 12-03-2004, 19:16

When i fitted my Brembos I bled my brakes out with DOT 4 Castrol Response fluid and all seems well. Remember brake fluid should be replaced at least every 2 years and Phils tips above are spot on, the best way is to open the bleed nipple to let the old fluid escape, top tip!

I will be upgrading the pads soon and skimming the discs as the set I 'aquired' werent brand new and need refacing.

But they are superb on such a light car.

24-02-2004, 10:00	#1
SkodiRS BRISKODA Staff Join Date: Oct 2002 Location: darkest Hampshire Posts: 8,650 Thanks: 0 Thanked 17 Times in 13 Posts	spngey brake pedal Right....now that I've maanged to post this in the right place. Can anyone explain to me why when you change your brake disks and pads you get a spongey brake pedal feel. Is it due to air getting into the system? Would be interested to know why it happens and may be then I can reduce the probability of it happening when I do my brakes. Cheers. Adrian. __________________ Adrian.

24-02-2004, 10:10	#2
SimonT Briskodian Join Date: Sep 2003 Posts: 1,174 Thanks: 0 Thanked 0 Times in 0 Posts	I don't know, but my best guess it that it feels "spngey" () because you are used to making the pad move a fraction of a mm until all the pad surface is in contact with the disc. A new pad doesn't have a flat surface (compare it to a pad you're taking out) or the correct "angle of approach" (we're talking fractions of mm's - the pad WILL be slightly mis-seated) so part of the pad makes contact, but only a small part so you apply more force which persuades more of the pad into contact. Eventually the pad wears smooth and to the correct angle, so you're back to normal. <waits for expert answer> __________________ Si

24-02-2004, 10:38	#4
Tavia4x4 Briskodian Join Date: Oct 2002 Location: J5 M61 Posts: 5,294 Thanks: 0 Thanked 0 Times in 0 Posts	Yup, sounds like another with air in after a change - god knows how it gets in as we always seem to get it! Find a low grip \ zero grip surface, ice, grass, anything with nothing to hit Go as fast as you dare, slam on the pedals and get the abs firing for as long as possible, this pushes the fluid through all the chambers. Check and top up afterwards. __________________ Ian __________________ Nice to be important, but more important to be nice...

25-02-2004, 09:56	#5
SimonT Briskodian Join Date: Sep 2003 Posts: 1,174 Thanks: 0 Thanked 0 Times in 0 Posts	Anyone with any more suggestions? I still can't understand how air gets in the system. __________________ Si

12-03-2004, 08:37	#7
SkodiRS BRISKODA Staff Join Date: Oct 2002 Location: darkest Hampshire Posts: 8,650 Thanks: 0 Thanked 17 Times in 13 Posts	Now done front discs and pads all round.....did initially have a spongy pedal but it's gone now. After a slight technical hitch pointed out by Obi Wan French ( ....it make such a big difference it's unbelieveable) braking is much improved and I'm sure will get better with further usage. Free tip of the day: get the brake winding tool or someone to lend it to you.....absolutely fantastic bit of kit and so easy to use. __________________ Adrian.

25-02-2004, 10:29	#6
Fatbloke Briskodian Join Date: Oct 2003 Location: Biddulph Posts: 21 Thanks: 0 Thanked 0 Times in 0 Posts	I don't believe air is getting in. It will be the pads bedding in. Until the surface is worn to match the disc only high points on the disc and pad surface will be making contact and this causes a slight loss in performance and a spongey feel. Bed them in gently and after 100 miles or so they will feel like normal.

12-03-2004, 08:45	#8
TaviaRS Dinosaur Join Date: Oct 2002 Location: North of the Watford Gap Posts: 14,918 Thanks: 19 Thanked 42 Times in 38 Posts	Live and learn Adrian, live and learn Always happy to help. Glad you bought the wind back tool now are you? Best £15 I spent, can do both sets of front pads in under 20 minutes now and that includes removing and refitting the wheels __________________ A jolly sensible Mercedes E class saloon in a rather fetching bluey grey colour. No it isn't fast, no it isn't modded, and yes, it will still eat your Fabia for breakfast. Official mobile chicane for Briskoda trackdays

12-03-2004, 09:23	#9
piv34uk NOW @ PEUGEOT Join Date: Nov 2003 Location: Bicester,Oxfordshire Posts: 1,416 Thanks: 29 Thanked 35 Times in 34 Posts	when changing brake pads the rubber brake hose should be clamped half way up with a pipe clamp..NOT MOLEGRIPS..the bleed nipple on the caliper should be undone before the piston in the caliper is wound back in...this stops any dirt from entering the master cylinder and is ejected through the bleed nipple.......pressure bleeding is the only way to fully elimanate air from the system................ brake fluid is hydroscopic which means it absorbs air and water (moisture) every time you drive...mainly from the kerbside because that is where most water settles......you can buy a device to boil the fluid in the reservoir and it will tell you the boiling point....for dot 4 and 4.1 the minimum is 180c anything below this requires changing.... the more water content the quicker it boils....catch the jist????????? sharp intake of breath Phil __________________ 1)RED ONE, FEW MODS; AND A HEALTHY 237bhp 2)GONE BUT NOT FORGOTTEN, 2ND OWNER OF THE BLACK BEAST, GOD WHAT A HOOT LACK OF PLANNING ON YOUR BEHALF DOES NOT CONSTITUTE AN EMERGENCY ON MINE

12-03-2004, 19:16	#10
Lummox Hairy Yeti Join Date: Sep 2003 Location: Newport Pagnell Posts: 21,403 Thanks: 19 Thanked 573 Times in 501 Posts	When i fitted my Brembos I bled my brakes out with DOT 4 Castrol Response fluid and all seems well. Remember brake fluid should be replaced at least every 2 years and Phils tips above are spot on, the best way is to open the bleed nipple to let the old fluid escape, top tip! I will be upgrading the pads soon and skimming the discs as the set I 'aquired' werent brand new and need refacing. But they are superb on such a light car. __________________ Unit 18 now open Servicing, repairs, modifications you name it we do it. Cupra console bushes at special price, PM for a very competitive quote.

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