Hard braking - Keeping her straight

Discuss problems you have had or are having with your Z4
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R60BBA
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Hard braking - Keeping her straight

Post by R60BBA » Thu Mar 08, 2018 9:15 am

Does anyone suffer from their Zed pulling to either side whilst under hard braking?

The car does not do this under normal braking, only when I’m pushing it and have to brake hard for an emergency as an example.

I have a fresh set of tyres, front pads are thick, rears are a little low but there is easily 3,000 miles left in them.
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Hard braking - Keeping her straight

Post by GAZA62 » Thu Mar 08, 2018 9:30 am

What's the road surface like ? if there any sort of ruts it can pull the car around even on non RFT sports suspension and wide low profile tyres do no give as much
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Hard braking - Keeping her straight

Post by Marlon » Thu Mar 08, 2018 9:53 am

You've checked the pads so could be uneven tire pressure, Stuck caliper, collapsed brake hose, worn suspension parts
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Hard braking - Keeping her straight

Post by R60BBA » Thu Mar 08, 2018 10:30 am

GAZA62 wrote:
Thu Mar 08, 2018 9:30 am
What's the road surface like ? if there any sort of ruts it can pull the car around even on non RFT sports suspension and wide low profile tyres do no give as much
It happens on normal smooth surfaces but only when braking hard.

Only noticed it 2 days ago...

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Hard braking - Keeping her straight

Post by R60BBA » Thu Mar 08, 2018 10:32 am

Marlon wrote:
Thu Mar 08, 2018 9:53 am
You've checked the pads so could be uneven tire pressure, Stuck caliper, collapsed brake hose, worn suspension parts
Is there anyway to diagnose a sticking caliper or collapsed brake hose without visiting a mechanic :?
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Hard braking - Keeping her straight

Post by Marlon » Thu Mar 08, 2018 11:08 am

R60BBA wrote:
Thu Mar 08, 2018 10:32 am
Marlon wrote:
Thu Mar 08, 2018 9:53 am
You've checked the pads so could be uneven tire pressure, Stuck caliper, collapsed brake hose, worn suspension parts
Is there anyway to diagnose a sticking caliper or collapsed brake hose without visiting a mechanic :?
I will let the 'mechanics' among us answer that one - personally I'd get my Indy to take a look :)
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Hard braking - Keeping her straight

Post by Ducklakeview » Thu Mar 08, 2018 11:18 am

If it's only under hard braking, I'd be checking the lollipops as a first call. If they are soft/worn, they allow the car to "self steer" under heavy braking. Quick test you can do with it on the ground, handbrake on - Then put your hands at the 12 O'clock position on top of the front tyre, and try hard to move it back and forth in the direction of normal travel. If a bush is soft/worn, it will allow the wheel to move forward and backward slightly.

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Hard braking - Keeping her straight

Post by patriot66 » Thu Mar 08, 2018 11:24 am

I'd check tyre pressures and look for uneven tyre wear first. Are the brake pads/discs in good condition ? Jack each front wheel up and spin it to see if caliper is binding and check track rod ends, ball joints and bushes on each front wheel whilst it's of the ground. Hold the wheel at 9-3 and 12-6 o'clock and give it a bloody good pull/rock. :thumbsup:
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Hard braking - Keeping her straight

Post by R60BBA » Thu Mar 08, 2018 11:33 am

patriot66 wrote:
Thu Mar 08, 2018 11:24 am
I'd check tyre pressures and look for uneven tyre wear first. Are the brake pads/discs in good condition ? Jack each front wheel up and spin it to see if caliper is binding and check track rod ends, ball joints and bushes on each front wheel whilst it's of the ground. Hold the wheel at 9-3 and 12-6 o'clock and give it a bloody good pull/rock. :thumbsup:
It’s not tyres as I put a brand new set of PS4s on last month.

It’s not pads either (refer to original post). However my discs have a slight lip and I don’t know when they were last changed, so the problem could be related to them.

I’ll check the play in the joints this weekend to see if there’s any movement. If not, it will be another trip to Munich Legends :roll:
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Hard braking - Keeping her straight

Post by jabber » Thu Mar 08, 2018 12:32 pm

A small lip on a disc is fairly normal due to pad size only a problem if it is a a large lip indicating excessive disc wear
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Hard braking - Keeping her straight

Post by brillomaster » Thu Mar 08, 2018 2:03 pm

after normal use, is one of your brake discs hotter than the other? a sticking caliper will leave the pads rubbing the disc slightly, so will heat one disc up despite not actually braking.

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Hard braking - Keeping her straight

Post by R60BBA » Thu Mar 08, 2018 2:34 pm

brillomaster wrote:
Thu Mar 08, 2018 2:03 pm
after normal use, is one of your brake discs hotter than the other? a sticking caliper will leave the pads rubbing the disc slightly, so will heat one disc up despite not actually braking.
I wouldn’t know how to test this?
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Hard braking - Keeping her straight

Post by ph001 » Thu Mar 08, 2018 2:55 pm

Drive along a relatively straight flat road trying to use the brakes only minimally. Park up the car and check the temperature of each disc. They should be the same side to side. Just be careful as they do get very hot if you have been hard on the brakes.

To be honest, a sticking caliper has always been really evident to me - you can feel it with the car in neutral when coasting to a stop from very low speed on a flat road. Any kind of binding and the car grabs just a fraction before it comes to a standstill.
Last edited by ph001 on Thu Mar 08, 2018 4:53 pm, edited 1 time in total.
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Hard braking - Keeping her straight

Post by raymond.harper » Thu Mar 08, 2018 4:09 pm

The Z4 has emergency brake assist so when you brake hard the car decides to brake even harder. Would have thought the stabilty control would cut in if the computer thought there was a problem with traction. Then I could be wrong. After you have used the brakes hard crouch down on all fours near a wheel, not a good look, and see if your face can detect if one of the calipers are hotter.

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Hard braking - Keeping her straight

Post by Marlon » Thu Mar 08, 2018 4:15 pm

raymond.harper wrote:
Thu Mar 08, 2018 4:09 pm
. . . After you have used the brakes hard crouch down on all fours near a wheel, not a good look, and see if your face can detect if one of the calipers are hotter.
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