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stuart123

Member Since: 03 Apr 2017
Location: Manchester
Posts: 207

2009 Defender 90 Puma 2.4 CSW Aintree Green

90 Puma rear brakes

Hi all

My front brakes lock up the front tyres way too easily... I've checked and adjusted pressures with no improvement.

The rear callipers were in okay condition but I have rebuilt them with new pistons and also put new pads in - no improvement. Also, new fluid and bled etc.

However, I still can't get the backs to lock up, even on gravel/ grass etc.

The readings on the rolling road were
Front: 268 kgf and 278 kgf
Rear: 119kgf and 122 kgf.

So the rear are half of what the front are...

I understand the backs shouldn't lock up easily but this still seems too light.

It's been suggested the front pistons maybe sticking meaning the front are too effective - could this be the case? Is it worth checking them?

Can't see any issues with the servo - cracks etc.

Any other suggestions?!

thanks

16th Sep 2019 11:40am

stuart123

Member Since: 03 Apr 2017
Location: Manchester
Posts: 207

Anybody?!

17th Sep 2019 8:04am

Balvaig

Member Since: 19 Feb 2016
Location: Fife
Posts: 730

2016 Defender 90 Puma 2.2 Landmark LE Corris Grey

There is a pressure sensor for the rear brakes which may have seized. See link below:
http://slroc2.co.uk/forum/index.php?topic=4336.0
Mine has never been tested on a rolling road so don't have values to compare.
Hope the link works.

17th Sep 2019 10:15am

stuart123

Member Since: 03 Apr 2017
Location: Manchester
Posts: 207

Thanks, I had read that forum but couldn't see where a pressure sensor is actually fitted?

17th Sep 2019 10:34am

Balvaig

Member Since: 19 Feb 2016
Location: Fife
Posts: 730

I am not certain where it is . I only have access to a 2012 workshop manual which states:
On 90 models a pressure reducing valve (PRV), fitted to the right-hand bulkhead in the engine compartment, maintains the braking balance. Pressure to the rear calipers is regulated by the PRV, this valve is of the failure by-pass type, allowing full system pressure to the rear brake calipers in the event of a front (secondary) circuit failure.

Hope this helps.

17th Sep 2019 1:22pm

derbywill

Member Since: 25 Mar 2010
Location: Derbyshire
Posts: 556

If ABS is fitted it will not have a PRV. Did they lock on the rollers when these pressures where achieved? If so try loading the rear to max weight and try again.

Readings don’t sound too bad, and you don’t want the rear ‘stepping out’ in an emergency braking situation.

Cheers

Will 2005 90 XS
1954 86'' Series 1 tilt
1968 88” 2A 200tdi
2002 110 Hardtop

17th Sep 2019 7:01pm

keef9t

Member Since: 13 Mar 2016
Location: manchester
Posts: 170

2007 Defender 90 Puma 2.4 HT Stornoway Grey

I posted on this problem back in 2017. I would suggest all 90's without ABS will give similar rolling road readings. The result of the PRV doing it's job in preventing dangerous rear wheel lock-up. The 110's don't have one fitted.

I have used the same garage with the same tester for years and he always said " all 90 rear brakes are crap, the 110's ok"

I told him about the PRV and he now understands.

He uses the Tapley footwell meter on mine since we came to an understanding and it passes. The vehicle would fail the MOT based on the rolling road figures.

If you suggest to your tester that the rolling road could potentially damage the transmission they should be minded to use the Tapley footwell meter.

Just out of interest, I had renewed every part of my braking system, except the steel pipes ( I'm talking Master cylinder, servo,PRV, flexibles, discs, callipers, pads and fluid). It made absolutely no difference to the readings.

For once, "they all do that,Sir" has ring of truth about it Life is short, so have your pudding first
---------------------------------------------

2007 90 2.4Tdci County HT Stornaway
Discovery 1 200Tdi Sold
90 Turbo Diesel HT Sold
110 2.5NA CSW Stolen
88 Series II Sold
Meccano Set. Don't know what happened to that

17th Sep 2019 8:58pm

stuart123

Member Since: 03 Apr 2017
Location: Manchester
Posts: 207

derbywill wrote:
If ABS is fitted it will not have a PRV. Did they lock on the rollers when these pressures where achieved? If so try loading the rear to max weight and try again.

Readings don’t sound too bad, and you don’t want the rear ‘stepping out’ in an emergency braking situation.

Cheers

Will

Interesting, thanks. No ABS fitted. Not sure about locking the back rollers...

18th Sep 2019 7:38am

stuart123

Member Since: 03 Apr 2017
Location: Manchester
Posts: 207

keef9t wrote:
I posted on this problem back in 2017. I would suggest all 90's without ABS will give similar rolling road readings. The result of the PRV doing it's job in preventing dangerous rear wheel lock-up. The 110's don't have one fitted.

I have used the same garage with the same tester for years and he always said " all 90 rear brakes are crap, the 110's ok"

I told him about the PRV and he now understands.

He uses the Tapley footwell meter on mine since we came to an understanding and it passes. The vehicle would fail the MOT based on the rolling road figures.

If you suggest to your tester that the rolling road could potentially damage the transmission they should be minded to use the Tapley footwell meter.

Just out of interest, I had renewed every part of my braking system, except the steel pipes ( I'm talking Master cylinder, servo,PRV, flexibles, discs, callipers, pads and fluid). It made absolutely no difference to the readings.

For once, "they all do that,Sir" has ring of truth about it

Thanks for that. It passed the MOT using the Tapley brake test. It was only me asking them to put it on a rolling road to see what the rear brakes were actually doing after the fronts kept locking up.

Maybe I need to look at changing tyres....

18th Sep 2019 7:42am

Balvaig

Member Since: 19 Feb 2016
Location: Fife
Posts: 730

The pressures are in balance both front and rear.
With no ABS you will inevitably lock up the axle with the greatest pressure if you brake hard. That's why we were taught cadence braking in the old days before ABS!
As stuart 123 says, designed to lock the fronts before the rears and if he has similar readings, then probably all ok.
Tyre condition will also have a big impact on braking - old tyres become hard and loose their grip more easily.

18th Sep 2019 9:13am

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