My 90 skid when braking

[Tibout]

Hi there my landy a 90 2.5TD (doom 200tdi hopefully) I noticed that if I have to break a bit hardthe back of the truck just skid and I could easily lose control of it and that's only at around 40mph and worse if I'm coming down a hill. There's new brake pads and caliper in front and the back has got new drum wheel cylinder shoes spring. Any ideas what causing the landy to skid so badly if I brake heavily!

Any advice are wellcome

thanks a mil

thierry

[Mutley]

Going too fast!?!....Braking too hard!?!

Sorry couldn't resist

[Tibout]

Haha I wish I was going fast even at 30mph she will skid as if the back wheels just lock itself. Brakes are too good( I wish) but sometimes it's scary specially when I'll finish the conversion with the 200tdi!

[Anderzander]

Does that model have a brake bias valve? It sounds like one gone wrong.

[Tibout]

I don't know if I have one if she's got one where will it be and how to fix it? Thanks again lads

thierry

[Litch]

What tyres are you using?

I remember when I bought my first S111 and it was still running on hard 6.50x16 crossplys and the wheels used to lock up all the time (especially in the wet), as soon as I changed over to 7.50x16 radials which were softer they actually used to grip the tarmac and no more skidding.

[Tibout]

I'm using 3weeks old insa turbo special track 265/65/16 but was the same with the insa turbo sahara 235/85/16. I don't know what causing it but it's making worried a lot so easy to lose control of the landy

[FridgeFreezer]

Pop the rear drums off and check that no oil has gotten on the friction material, oil from a leaking hub etc. will make the brakes very grabby.

Also check that none of the shoes have separated from their lining or are no longer seated properly - I have had this happen on the freelander, one of the rear shoe linings fell off and touching the brakes at all resulted in the wheel locking as the lining was pulled in & jammed.

[Tibout]

thanks for the reply i'll have a look during the week. hopefully it will just be an easy fix

thierry

[Briarston]

I don't know if I have one if she's got one where will it be and how to fix it? Thanks again lads

thierry

My '88 90 has one, LR. call it a "G Valve" I believe. It's located on the RHS of the engine bay, ontop of the chassis rail, roughly below the clutch master cyl.

Follow the pipe from the brake master cyl. down and you will come to it, unless it's been removed. It contains a fairly light spring and a ball bearing. Moisture in the brake fluid doesn't do these steel parts any good - it may have siezed.

BTW, when I fitted a Disco disc braked axle I found that the rear brakes locked up easily, even though the G Valve was working ok with the drums. I fitted the unit from a Disco 1 in it's place which prevents this now.

Hope the above may be of some help, although others who have done this mod. say they have no problems with the brakes locking, using the standard G Valve.

[Tibout]

thanks so much for the reply i'll have a look tomorrow and see if i can find it.

king regards

thierry

[Aragorn]

If your saying the REAR locks up and the front doesnt, then (assuming the aforementioned valve is present and correct) theres something wrong with the front brakes.

The front should be doing about 3-4 times the braking of the rear, and the stock brake bias is configured such that the front locks up first for safety reasons.

[reb78]

Doesnt this happen on 90s with drums if the leading shoe is put on facing the wrong way?

[Briarston]

Doesnt this happen on 90s with drums if the leading shoe is put on facing the wrong way?

Assuming that the rear brakes are all correct, then surely "locking up" is due to weight transferance, which I think is more pronounced with the SWB models - hence the "G Valve".In my case, I had already replaced front discs, pads and caliper pistons/seals, and the rears, still drums at the time, would tend to lock the wheels when braking moderately hard - nowhere near an emergency stop, particularly on a wet road. Wouldn't you need to be doing a full scale "crash stop" to lock the fronts on a hard surface?

Just my own opinion and experiences, no contradiction intended!

[reb78]

The valve is one possible fault, but on the 90s, there is a leading and trailing shoe and the trailing shoe i think faces rearward and has a tendancy to snatch on when applied in reverse - this is generally at low speed and not often. Reverse the shoes so they are the wrong way round and the trailing shoe will have the opportunity to snatch on more frequently and at much higher speeds. Its come up a few times on here that people have put these on the wrong way round.

[Aragorn]

Assuming that the rear brakes are all correct, then surely "locking up" is due to weight transferance, which I think is more pronounced with the SWB models - hence the "G Valve".In my case, I had already replaced front discs, pads and caliper pistons/seals, and the rears, still drums at the time, would tend to lock the wheels when braking moderately hard - nowhere near an emergency stop, particularly on a wet road. Wouldn't you need to be doing a full scale "crash stop" to lock the fronts on a hard surface?

Just my own opinion and experiences, no contradiction intended!

The point is the braking system is designed with that in mind. The front should ALWAYS lock up before the rear, which is why the fronts on all cars have bigger calipers and usually larger disks, and the rears are often limited down further with a reduction valve.

A stock disk braked 90 has two pairs of 46mm pistons on each front with a 300mm disk, and a single pair of 41mm pistons with a 290mm disk on each rear. The rear line pressure is then further reduced with said valve, to ensure that under heavy braking, the rears do not lock before the fronts. Its a safety feature, such that if you have to for instance brake hard on a fast road or motorway, you dont get the rear end overtaking the front.

Something like 70-80% of braking effort occurs on the front wheels due to the weight transfer, and as a result the brakes are sized accordingly.

If its locking the rears first, the brakes arent working correctly. Either because the rear is recieving too much pressure or is over-eager due to the shoes as reb mentioned, or because the front isnt up to scratch.

[Tibout]

hi lads you were right it's my G valve which is faulty. just wondering i may have one from an defender 93 200tdi will it fit mine 90 1988 2.5TD?

thanks

thierry

[western]

for chassis from HA701009 to LA930455 use G valve this one NRC8215

from chassis LA930456 use brake valve NTC8836

I'd stick with the type you have, for the simple reason, you know it'll fit & will not require any brake pipe changes.

[Tibout]

thanks for the information. just wondering because i've got a 93 rusty defender in the garden from which i've got my tdi engine.

[Tibout]

P.S:My chassis number is EA346592 and the 2 models i looked at seem not the right one's i might be wrong correct me please

[western]

might need the brake pipes from the donor vehicle as well as the valve, if the existing pipes won't connect/reach the ports on the later valve.

[SH4RKY]

Thought I would resurrect an old thread rather than starting a new one;

My 86 drum braked 90 (Chassis: AA261384) is doing a similar to the OP. But only the one rear wheel is locking...

For clarification, if mine has a G valve and it was faulty, would this cause both rear wheels to lock up, rather than just the one, right?

If so I’m thinking it’s probably one of the other issues mentioned above by FridgeFreezer; My hub cap has been leaking oil on the side that locks, so I guess there is a good chance some oil has got into the brake.

Will take the wheel off and have a look.

[cosecon]

Thought I would resurrect an old thread rather than starting a new one;

My 86 drum braked 90 (Chassis: AA261384) is doing a similar to the OP. But only the one rear wheel is locking...

For clarification, if mine has a G valve and it was faulty, would this cause both rear wheels to lock up, rather than just the one, right?

If so I’m thinking it’s probably one of the other issues mentioned above by FridgeFreezer; My hub cap has been leaking oil on the side that locks, so I guess there is a good chance some oil has got into the brake.

Will take the wheel off and have a look.

Maybe you need to re-adjust... It shows that one brake is more tight than the other. When I get this problem, I just pop open the rear drums, give them a good air cleaning (wear a good breathing mask) and then just slightly roughen the brake shoes and the inside of the drum with some very coarse sanding paper. I close them re-adjust the brake by tightening until the wheel blocks and then slack the same portion of a turn both sides.

[SH4RKY]

Maybe you need to re-adjust... It shows that one brake is more tight than the other. When I get this problem, I just pop open the rear drums, give them a good air cleaning (wear a good breathing mask) and then just slightly roughen the brake shoes and the inside of the drum with some very coarse sanding paper. I close them re-adjust the brake by tightening until the wheel blocks and then slack the same portion of a turn both sides.

Thanks for the info. Will check and clean both sides. By air cleaning, do you mean you just blast it with an air hose or clean it without water?

[lrfarmer]

My '88 90 has one, LR. call it a "G Valve" I believe. It's located on the RHS of the engine bay, ontop of the chassis rail, roughly below the clutch master cyl.

Follow the pipe from the brake master cyl. down and you will come to it, unless it's been removed. It contains a fairly light spring and a ball bearing. Moisture in the brake fluid doesn't do these steel parts any good - it may have siezed.

BTW, when I fitted a Disco disc braked axle I found that the rear brakes locked up easily, even though the G Valve was working ok with the drums. I fitted the unit from a Disco 1 in it's place which prevents this now.

Hope the above may be of some help, although others who have done this mod. say they have no problems with the brakes locking, using the standard G Valve.

my 90 brakes evenly with standard valve, MOT test shows almost the same backing force 450 front 400rear