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110 Rear drums locking before front disks


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Hello,

Now the 110 is on the road and I'm getting some miles on it I'm starting to work through a snag list.

The problem is that the rear drums are really quick to lock up, if you continue to press the pedal then the fronts do lock as well but it takes quite a lot more force to get to that stage. With all four locked it stops quickly and straight but with only the rears locked is quite a different beast.

It has new front callipers and vented disks. New pipes and braided hoses all round. New rear cylinders and a new master cylinder. It has a working (tested whilst bleeding) PWDA valve that lights the brake warning light on the dash when there is a pressure imbalance front to rear.

So my question is why are the rears so keen to lock? Is it just a trait of 110 hard-tops when unloaded? If so is there any way to improve it (G valve)?

Thanks in advance!

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Cheers Western, no evidence whatsoever of there ever being a G valve, no bracket on the chassis and piped up for the PWDA valve.

Saying that that 110 has been apart before I had it (originally a 2.5 petrol - now a 200tdi). Not sure why they would have removed this useful (and EXPENSIVE!) part!

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Top right of attached page shows the 3 different brake valves,

upper left = combined pressure conscious [PCR] valve,pressure differential warning actuator [pdwa]

upper right = is a PDWA as on my 110 C station wagon

lower left = G valve.

just wondering which one you have on your 110 ? if there is no seperate G valve I suspect you have the combined PCR/PDWA, so the PCR part may not be operating correctly, that would explain your rear brakes locking up before the fronts.

post-20-0-74535200-1422033682_thumb.jpg

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.... New master cylinder ....

Can they be plumbed the wrong way around? (Front port to rear port etc)

Would it make a diff as I thought the plungers were different sizes (not sure of correct term... Force over area etc)

Worth a glancing check no?

(Do you get a different master cylinder for disc brakes all round to discs plus drums (again force over area .... Presume it was working fine at some point in the past) ... Did you get / have supplied the right master cylinder

Rob

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Wrong master cylinder is possibility the part number of the one I fitted was Nrc8690. The 110 wasn't on the road when I bought it so I never fully checked the brakes, therefore I'm unsure if this has always been an issue.

Regarding which port on the master cylinder I should be using, I just put the new cylinder in place of the old and connected the pipes to the same ports, can anyone confirm which port is for the front and rear?

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NRC8690 is correct for a pre 300tdi 110, same as mine, http://www.lrseries.com/shop/product/listing/8980/NRC8690-LWB-110-BRAKE-MASTER-CYLINDER-ASSEMBLY.html

can't be connected wrong, as the pipes end fittings are different sizes.

for which port goes to front or rear, refer to the lower left diagram on the attached page I posted earlier

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  • 1 month later...

Interesting, I didn't realise that the PDWA could affect bias? Is there a valve in there as well as the switch then?

And point taken regards the bias valve, I'm going to remove the knurled knob once I'm completely satisfied with the bias.

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The pdwa is only there to tell you what you have just discovered if one of your circuits has failed. I.e an imbalance of pressure in the circuit pushes the shuttle valve either way to light the light.

They are a series leftover, and not fitted to later 110's which should have the cap with float switch to detect low fluid level.

They originally turned up on old triumph cars and are equally despised by their owners.

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To update this thread, I've fitted an adjustable bias valve and the difference is enormous!

Which one did you use in the end?

I have had exactly the same problem with my 110 (its also a 110 van of the same age). I was going to fit an adjustable bias valve to solve the problem but I've just managed to get hold of a 110 short nose rover type axle with disk brakes, so I was going to fit that and see if the problem still exists with the new axle. I suspect if anything it wil make it worse.

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Can i join the club :wacko: - got an f reg 110 kept by factory then fitted with 200tdi and sold on by them

I only have what seems to be the Pwda valve fitted on a bracket to rear axle. I am not sure what it is i have a photo

post-22339-0-72443500-1427115814_thumb.jpg

Mine locks up rear drums very easily and i am used to sliding sideways but would rather not!!

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Thanks for info

post-22339-0-25479600-1427123413_thumb.jpg

i have no g valve or anything else it seems from photo. Pipe goes straight back to the t piece.

So i guess thats my problem unless theres any other system.

Used firmly the brakes are ok but stand on them a little bit more and back locks up like a good un -drivers side first - resulting in a sideways lurch or worse.

so what do i need to correct/ improve this? is it possible its a later system? if so what do i look for?

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