Defender 90 Brake Bias Valve Pictures needed

[Ibex94]

Morning all,

Need a bit of help.  The Ibex went through his first IVA inspection last week and the rear wheel brake loads were low when tested (downrated my tow capacity to 2.2 Te).  From memory everything is either new or I've refurbished it apart from the brake bias valve.  Given inspector was surprised at how good front brakes are and the brake balance across the axles was good I suspect the bias valve has some issues.  I originally installed it in my donor vehicle when I upgraded the rear brakes to disks and then swapped it into the Ibex.  However I can't remember how I confirmed the piping was all connected correctly and. want to make sure I don't have something hooked up wrong.  Searched for pics and connection information but the manuals don't appear to show it.  I

If anyone has this information could you send me a link or alternatively your best fag packet sketch and a photograph please?  

Many thanks.

[miketomcat]

From memory IVA call for the rear brakes to be 60% of the front where as MOT it's only 50%. It might be worth deleting the bias valve completely.

You can always refit it if you find the rear locking to much after the IVA.

Mike

Edited March 25, 2023 by miketomcat

[western]

These might help 

[Ibex94]

Thanks for the info Ralph, @western, its difficult to tell  off those manual outlines.  I think mines the combination valve as it bears the closest resemblance in shape but it doesn't have a brake press switch fitted in the middle at the top and mines mounted opposite hand .  My part number is NTC8836.  

The master cylinder has 2 outlets, one goes direct to N/S front wheel, the other goes to the bias valve. The rear brake outlet goes to the bias valve.  other go in to the bottom port, front lhs.  The outlet then come off the top with the lhs going to the front O/S.

I think I figured this out from the vehicle it originally came off but can't find my pics.

@miketomcat contemplating your option as a safe one for getting passed, just need to make replacement lines which will be a pita with everything now fitted.

A43B5320-5EB0-42E0-A764-ED2907441E45.heic

[western]

Your welcome, I can't open the file you uploaded. 

This is your valve going on the part number you posted

https://www.jgs4x4.co.uk/brake-valve/

[Bowie69]

Here you go Ralph:

[western]

 Cheers 👍

[Ibex94]

Thanks @Bowie69 a local boy I see

That's the bad boy @western.

Front brake circuit LHS, Rears RHS in at the bottom.

Think I'm going to remove it as @miketomcat suggests for my next IVA.  Such a pain to resolve the issue when you can't legitimately drive on the road.

[western]

On 3/25/2023 at 5:42 PM, Ibex94 said:

Thanks for the info Ralph, @western, its difficult to tell  off those manual outlines.  I think mines the combination valve as it bears the closest resemblance in shape but it doesn't have a brake press switch fitted in the middle at the top and mines mounted opposite hand .  My part number is NTC8836.  

The master cylinder has 2 outlets, one goes direct to N/S front wheel, the other goes to the bias valve. The rear brake outlet goes to the bias valve.  other go in to the bottom port, front lhs.  The outlet then come off the top with the lhs going to the front O/S.

I think I figured this out from the vehicle it originally came off but can't find my pics.

@miketomcat contemplating your option as a safe one for getting passed, just need to make replacement lines which will be a pita with everything now fitted.

A43B5320-5EB0-42E0-A764-ED2907441E45.heic 1.28 MB · 3 downloads

Don't know why I can't open the download, it says content restricted

But glad the info you have received from myself & others has helped. 

[Retroanaconda]

My brake bias valve is a different type - the earlier one I think. It just sits inline between the master cylinder and the rear brakes.

Bad photo here:

[uninformed]

Brakes are an interesting topic. My 98’ 110 cab chassis does not, nore ever had a proportional valve. I think that’s true for a lot of 110s? No idea on the 130 but I’d assume the same given the affect longer wheelbase has on ‘pitch’. 

I can’t speak for the earlier 110s but when they went to discs all round, the front calipers have exactly double the piston area of the rears. Obviously pad area and rotor dia also play a roll in brake bias, as does the ‘locus’ point , which in our case of AWD is the centre of centre diff. 
 

Add to all that, you will get more pitch in a shorter wheelbase than longer. 

[miketomcat]

Early 110's just have the shuttle valve that puts the light on and stops you loosing all your fluid.

I had a brake bias issue years ago when I SVA'd a buggy (mini based) that was mini brakes but rear engined so drum rear with all the weight and disc front. It would lock the front easily until I lowered the front tyre pressure but to get it through the SVA I pumped the front tyres up so the front locked earlier this brings the brake force at the front down allowing the rear to be closer.

Mike

[Ibex94]

On 3/26/2023 at 7:47 PM, Retroanaconda said:

My brake bias valve is a different type - the earlier one I think. It just sits inline between the master cylinder and the rear brakes.

Bad photo here:

Thanks Retro, that looks like the G valve which adjust brake force based on deceleration.

Trucks looking good!

 

[Ibex94]

On 3/27/2023 at 3:45 AM, uninformed said:

Brakes are an interesting topic. My 98’ 110 cab chassis does not, nore ever had a proportional valve. I think that’s true for a lot of 110s? No idea on the 130 but I’d assume the same given the affect longer wheelbase has on ‘pitch’. 

I can’t speak for the earlier 110s but when they went to discs all round, the front calipers have exactly double the piston area of the rears. Obviously pad area and rotor dia also play a roll in brake bias, as does the ‘locus’ point , which in our case of AWD is the centre of centre diff. 
 

Add to all that, you will get more pitch in a shorter wheelbase than longer. 

Thanks Uninformed, from what I can see bias type valve only went in the 90, I assume the short wheel base makes them more sensitive.  I can't work out what the early discos had, there appears to be something in the line but only attached to the rear circuit.  The Ibex is 2.5m so pretty much the same as disco.

[Bigj66]

On 3/26/2023 at 7:47 PM, Retroanaconda said:

My brake bias valve is a different type - the earlier one I think. It just sits inline between the master cylinder and the rear brakes.

Bad photo here:

Do you happen to know the angle from horizontal that the G valve must be mounted?

20 degrees springs to mind.

And does the outlet to the rear brakes need to be in the highest position or could it be mounted with that port closer to the chassis?

[western]

Yes 20 degree is what the workshop manual states, see my previous reply the 3rd photo shows the info. 

The pipe connections are marked 5 & 6 on the diagram, just as inlet & outlet

[Bigj66]

38 minutes ago, western said:

Yes 20 degree is what the workshop manual states, see my previous reply the 3rd photo shows the info. 

The pipe connections are marked 5 & 6 on the diagram, just as inlet & outlet

Missed that photo but looking at it now shouldn’t it be 7 degrees for the G valve?

 

Forget that, senior moment there 🤦‍♂️

20 degrees it is 👍

[western]

No, in the list number 7 states 20degrees, 

You have chopped off the bottom part of the original photo of the relevant page, 

[Bowie69]

Helpful, using a numerical key to point to a numerical value.... Not confusing at all 😄

[Snagger]

15 hours ago, Bowie69 said:

Helpful, using a numerical key to point to a numerical value.... Not confusing at all 😄

Especially since there was space just to put “20*” there, eliminating the need to look it up in the key at all. 🙄

[miketomcat]

On 4/16/2023 at 8:26 PM, Bowie69 said:

Helpful, using a numerical key to point to a numerical value.... Not confusing at all 😄

Yes but then they couldn't change it randomly 3 years later and not tell anyone.

Mike