Brakes.... should they stop you?

[Jonny Boaterboy]

If i drive up a 45 degree slope (I have a suitable one near me which is block paved see pic) and stamp on the brakes the front ones lock up and the rear wheels don't.... and i slide down the slope with the front locked up and the rear wheels rotating..... This carnt be right can it? has anyone got any ideas as to why this could be happening?

It has traction control, abs and the rear discs look scored but that shouldnt stop them locking up should it?

Tar

Jonny

[Range Rover Blues]

That way round, weight transfer.  Given that the rear wheels are so far under the car when it's on level ground think how far back the C of G is when on a 45 degree slope? the front end must be loads lighter.

Have a look at your tyres for bulging as a rough guide to how much the weight has shifted.

BTW, if you are locking up the fronts and the backs are going round your viscous unit is fine :D

[waveydavey]

I know older cars used to have an anti lockup valve for the back wheels to help stop cars spinning.

[Jonny Boaterboy]

Hey there Mr blues..... good point about the viscus   however even if your center of gravity is way over the rear wheels you should be able to lock them up surly? otherwise how are you supposed to stop yourself on a failed hill climb? I understand that you have different brake forces for the front and rear wheels but I thought if you press the brake pedal hard enough there should be enough pressure to lock the rear wheels as well

The reason this came to my attention was because on a recent trip up north I had an empty trailer on the back, a fairly big one, and while coming down a long steep hill you could smell the burning of the pads with a touch of brake fade...... Surly a range rover that can tow 3.5 tone and has twin vented discs  should'nt  get brake fade with an empty trailer? Thats why I started to look at whether the rear brakes were doing there job?

what do you think?

ps I havent forgot about the air surspension info will get onto it soon

[redhand]

If i drive up a 45 degree slope (I have a suitable one near me which is block paved see pic) and stamp on the brakes the front ones lock up and the rear wheels don't.... and i slide down the slope with the front locked up and the rear wheels rotating..... This carnt be right can it? has anyone got any ideas as to why this could be happening?

It has traction control, abs and the rear discs look scored but that shouldnt stop them locking up should it?

Tar

Jonny

Have you tried reversing up to see what effect that has on the braking.

[Jonny Boaterboy]

I guess if I went up backwards it would hold fine on the foot brake as the front wheels appear to be ok.

Interesting about the anti lock valve waveydavey so how are you surposed to stop youself on a failed hill climb.... pull the hand break?

  :?

[Range Rover Blues]

Front wheels should be doing more than 70 of the braking, but what you said about brake fade reminds me that my rear brakes are not that good at the moment.

Although the orignal spec for the rear disks sees a smaller diameter they are in truth the same disk as the front, so less of the surface area is used and as the back brakes don't work as hard it's possible for the surface to rust or become pitted.

What's happened to mine is that the surface has rusted and the pads have polished that rust, it continued to rust away and formed a scale on the disk surface that the pads polish but can't grip, it's a bit spongy.  So the braking effort goes into this scale rather than the disk and the brakes become less effective.  What makes it doubly worse is that it mostly happens on the outside of the disk, reducing the disk efficiency further.

So look at the rear disks for scaling, oil contamination (a favourite on Blue), blueing (overheating) and general condition.  If they are scored what caused this? and are the pads wearing evenly across all 4.

That said I still don't think the rear brakes are strong enough to lock up the wheels unless you stand the car on it's nose.  the deceleration valve on the inner wing will reduce the hydraulic line pressure to the rear only when the car is decelerating rapidly, it might do something if you are facing down that hill.

BTW you have ABS right, did you check it with the engine running? the hydrostatic circuit only works on the front primary circuit, not the secondary/back circuit.  That is taken care of by the ABS hydraulic pump and booster unit.

As for failed hill climb, err, handbrake :? possibly? dunno on that one but I'd hope you had difflock on a 1 in 1 hill climb otherwise when the front end starts to scramble you could spill it.  As you will know with the Viscous unit it's not so hot when the vehicle is stationary, it could have done with manual lock as well.

[Jonny Boaterboy]

Ummmm it could be the fact the discs are in a bad way there is scoring on them and alot or corosion maybe a discs and pad change is in order..... so do I go for standard landrover pad's and discs of put some EBC's on there?

The brakes are quite spongy as well do you bleed the brakes in the same way as standard brakes using the nippels on the calipas and if so is this how you change the brake fluid i.e. pump out the old fluid while keeping the resivior toped up with new fluid?

[Range Rover Blues]

Yes but......
I was reading the manual last night by coincidence as I think my rear callipers are past their best on the LSE and I have new ones from Blue I've never fitted.

I'm fitting standard disks on the back with EBC pads, not that they make any real difference as the standard pads are very good.

EBC disks are about £70 from Paddocks if you feel a bit saucy, you aught to put matching ones on the front soon after though

otherwise I'd say standard is fine if it's in good condition.  Make sure you clean your new disks with spirits (petrol etc) before using them, the oil they come in is hrad to shift but if you leave it on it will ruin the new disk.  Go on, ask me how I know that

[Jonny Boaterboy]

sounds like you have had a bad experience! I allways thought oil would burn off eventually? What about the brake cleaning sprays you can get do they work or is the petrol the best bet?

Its true what they say about you Mr Blues you know your stuff shame you dont live down the road! it good to have someone with you knowledge and  understanding who is so willing to help all the time I will buy you a beer one day       =D>

[Range Rover Blues]

sounds like you have had a bad experience! I allways thought oil would burn off eventually?

So did the guy who fitted my new disks when I had the shocks done on my Cavaliler.  One of the reasons I don't pay garages to f*** up jobs I can quite easily do myself.

I will buy you a beer one day       =D>

That'l do nicely :)

[Range Rover Blues]

BTW, you asked about bleeding the brakes on ABS cars.  It isn't straightforeward if you read the manual and it's going to be a 2 man job.

Given that your system is full of fluid you may get away with bleeding a small amount in the 'normal' way but I would advise having a read of the manual first.

[waveydavey]

I will buy you a beer one day       =D>

That'l do nicely :)[/quote]

I was new to the Forums when you came up here last year.
If you come back again and I'm home I will happily buy you a beer!

[SebastianW]

What's happened to mine is that the surface has rusted and the pads have polished that rust, it continued to rust away and formed a scale on the disk surface that the pads polish but can't grip, it's a bit spongy.  So the braking effort goes into this scale rather than the disk and the brakes become less effective.  What makes it doubly worse is that it mostly happens on the outside of the disk, reducing the disk efficiency further.

Is there any way to clean up the discs once that has happened?


seb

[Range Rover Blues]

Yes you can get them skimmed but TBH it's not worth the cost these days, though I have done it in the past you have to watch you don't go below the minimum thickness.

You can try scrapping the scale away as the wheel turns slowly, engine running in 1st, but it will never be as good as it should be.