TLS conversion on SWB.

[w3526602]

Hi Tom,

Probably too late now, but when I bleed TLS systems, I usually wind the adjusters FULLY OFF

The idea is that this allows the pistons to be pushed deep into the wheel cylinders, so reducing the potential for trapped air behind the pistons.

Also, when rebuilding the vehicle, axles, or whatever, I assemble everything onto the backplates, including the pipes and hose (can be awkward), and lay the backplates "face down", so that the bleed nipples are pointing to the sky. It has always worked for me.

Er, why not retain 11" drums, on the front at least, but fit 11" REAR back plates and drums, giving 10" more stopping power at the front.

If you revert to 11" rear brakes, fit them with 10" rear wheel cylinders.

My mind is starting to "boggle", trying to remember all the various cylinder types and diameters.

If I can find the time (and remember), I will hit my calculator, and work out the CSAs of ALL the various pistons. It is interesting to note that the LWB front wheel TLS cylinders are 1.3/16" diameter,(1.1875"dia) so smaller than the SWB front wheel cylinders .... smaller surface area, but better braking for less pedal travel and driver effort. TLS is (are?) very desirable.

I am concerned that SWB brakes, coupled to a LWB master cylinder will require super human leg muscles. I once mounted the master cylinder from LWB servo brakes (I can't remember the I/D) onto a SWB pedal box, resulting in very short pedal travel, but the effort required (double?) crippled me within a few days.

Did I donate my Lockheed hydraulic catalogue to the Club library? If so, did I keep a copy of the Series page? If I did, it was probably on the document files of a long deceased lap-top. If you are visiting a Motor Factor, ask if they have any out-of-date trade catalogues ... you will be doing them a favour.  I'm not sure if Halfords "counter" catalogues will be any use to us, but probably slightly desirable, anyway, if you can get hold of one/some. The BOSAL (I think) exhaust catalogue had drawings of all the various (and many) Land Rover exhaust systems.

602

[Wittsend]

I suspect there are no printed accessory catalogues used these days.
It's all done by computer.

All they need is your reg number and the computer does the rest 

Works well for modern cars.

Problem with our classic Land Rovers is you have no idea what a Previous Owner may have messed with 

From time-2-time I've posted this chart of brake parts.

And I & others frequently post that properly maintained and adjusted 10" SWB are perfectly adequate for driving in today's traffic conditions. Although I've not tested it or have any data I'm confident that such SWB brakes will perform better than the Highway Code stopping distances. I have never felt that my SWB brakes are inadequate for modern driving conditions.

If lack of braking performance does worry you - you live in the hills and tow caravans etc. then to me the best braking upgrade would be to cut out all the messing around and go for a bespoke disc brake conversion kit.

[2286]

My motorbike has a drilled disc - helps to better disperse water.

I had Minifins on my Mini 
Not sure about better braking, but it's reduced weight on the wheel bearings.

 

Are drilled or or grooved discs not designed to inhibit pad glazing?

Minifins the genuine ones had cast alloy body with a steel/or iron insert for durability, or were they all alloy with special compound shoes.

[Twomokes]

My motorbike has a drilled disc - helps to better disperse water.

I had Minifins on my Mini 
Not sure about better braking, but it's reduced weight on the wheel bearings.

 

Are drilled or or grooved discs not designed to inhibit pad glazing?

Minifins the genuine ones had cast alloy body with a steel/or iron insert for durability, or were they all alloy with special compound shoes.

Minifins were steel lined for the friction area. Without I believe they were liable to warp.

[w3526602]

Hi,

Can anyone here discuss (scientifically) on the stopping power of disc brakes without servo?

I'm guessing that the brake lining Coefficient of Friction varies (or should) between servo and non-servo systems. There have been many delivery van drivers who found out the hard way that servo brakes don't work if the engine is not running.

I suspect that after marked Land Rover brake shoes are intended for S3 brakes.

602

[GlenAnderson]

I may seriously regret this, but here goes...

The "power" of disc brakes without a servo is exactly the same as with one.

The servo just helps you push the pedal harder by increasing your mechanical advantage. They use atmospheric pressure to multiply your applied pedal effort. In the case of disc brakes, they multiply the pressure you apply by three to four times.

If your engine isn't running to generate a vacuum, your brakes will work exactly the same way, provided that you can apply three or four times the accustomed pressure. Most people will be caught off guard and unable to react quickly enough to the change in behaviour, hence the "my brakes don't work" fallacy. They do work, just not in the same way.

Some people, those of lighter build, may not actually be physically capable of applying the necessary pressure to stop the vehicle in anything like a normal fashion.

But the mechanical components, pads, discs, etc, are all the same.

[Peter Holden]

Glen is spot on, a servo does not increase or improve the braking efficiency, it just reduces the human effort required

Peter

[diffwhine]

Saved me typing the same! Agreed!

[2286]

Agree with Glen re servo.

Now we can give him a harder puzzle, regarding why some trucks use oil over air, the pedal and master is oil actuation an air brake system.

All this talk of modifying brakes at the axle end by increasing wheel cylinder size thus requiring a larger capacity master cylinder got me thinking.

So until relatively late in the run 90/110 ran disc front and drum rear sls.

There is a trend to replace the drum rear axle with a disc rear axle from a discovery that has gone to meet it maker.

I know that disc calipers range rover disco differ front being twin pot and rears being single.

But those 90/110 that were built disc drum, do they require a master cylinder of increased capacity to service the disc disc set up or is there sufficient spare capacity to get away with it.

Just on a visual inspection the single pot rear disc caliper has a greater cylinder bore that the drum wheel cylinder.

[GlenAnderson]

Lorries in the 50s usually used just hydraulics for the brakes, or a vaccum servo to decrease pedal pressure.

As the use of trailers increased, the need for reliable operation without a physical hydraulic connection was needed, so "air over hydraulic" became the norm, with compressed air sending the braking signal to the trailer brakes as well as providing the boost to the lorry's hydraulic system.

That morphed into "full air", with all the vehicle's systems air operated. This, for reasons of inter-vehicle compatability, particularly the huge increse of the use of articulated units in the 70s, resulted in the standardisation we see today. Air over hydraulic is still really common on smaller lorries that don't tow trailers, and have smaller wheels that make fitting the big air brake actuators impractical, but most vehicles over 10 tons are full air.

Braking on the back of a 90/110 is regulated by a load sensing valve, which brings a layer of complication (or simplicity, depending on your perspective). Strictly speaking, if you swap out a rear drum axle on such a vehicle, you should also swap out all the other parts of the system to match.

[2286]

Excellent, I am going to park my curiosity there for the moment.

A quick look on paddock confirms that masters differ and should be matched to axles re 90/110 disc drum to disc disc swap.

[NoBeardNoTopKnot]

Yes, agree with Glen... stands back, this thread is different, refreshing. 

Like Glen I too may seriously regret this...  here goes. An increase in pad or shoe size - with all else equal- will not increase friction. Friction is a factor of force, NOT area. Friction is proportional to force.  Which'd be why we want a  heavier foot or a servo to increase our force for more friction. Not - with all else equal - a larger shoe or pad.

However a larger pad or shoe will COOL better, therefore in the extreme won't fade so easily, and it will wear more slowly. People seem to struggle with this, however a larger area - with all else equal - will NOT generate more friction.

That'd be why a TLS set has more power - NOT by virtue of shoe-area-increase, but by FORCE increase. The clue's in the name... TLS, there's two leading shoes, thus a 'twin-self-servo' effects, not a 'single-self-servo' effect.

And if I recall correctly???  the TLS also has a larger diam. and wider drum. The larger diam. supplies more force. More leverage or 'moments of force'. Yes - it's that force-not-area 'thing' again. The added width aids cooling and wear, not friction.

And yes, wide tyres generally give more grip, ask why, because it's never for the reason given in the sales lit. or by the bloke wearing the 'dunce-cap'.

Master-cylinders in drum or disc will have a different bias and check-valve residual-pressure weight. One reason for this, drums have heavy return springs, whereas discs bounce back purely on piston rubbers. Maybe I've said too much already, hence my fear and I suspect Glen's in broaching this subject.

[w3526602]

Hi TNK,

I agree with most of what you say.

Bigger diameter drums give more leverage to stop the wheel turning, but bigger wheel/tyres produce more leverage to try and keep the wheel turning. Bicycle brakes have very similar diameters for tyre and braking point. Thoughts of caliper brakes for car wheels ... already been done, only they call them disc brakes ... but the point of friction is a long way from the tyre tread, so leverage is working against us.

The transmission brake on Land Rovers have their effectiveness multiplied by the axle ratio ... somewhere between 4:1 and 5:1 ... but the differential will allow the least loaded wheel to turn backwards, or even turn the truck over. Knackered prop-shaft U/Js can give an alarming effect.  Been there, done that. I would prefer the hand brake drum to be on the front of the differential. If you break a half-shaft, you will not have a hand brake until you engage the front axle, and even then, not if your FWH are dis-engaged. Life could get very interesting, very suddenly. What was that film about the gods being crazy?

Strangely, CARDEN brakes are not allowed, except (apparently) on Land Rover handbrakes? But hey, a bad idea that works is better than a good idea that doesn't.

Question! Do 4x2 Landrovers also have a transmission handbrake, which would zilch handbrake, and no engine braking if a half-shaft breaks.

And if I recall correctly???  the TLS also has a larger diam. and wider drum.

Your half right. The ONE TON (and possibly 6-pot Estates ) that have WIDER drums ... I think detailed in the parts book, but my understanding is that the drums are still 11" diameter. I'm happy to be corrected.

I have always believed, perhaps wrongly, that disc pistons return due to the flex in the piston seal. Wobbly wheel bearings will (I think) allow the disc to wobble, which will push the pads/pistons deeper into their callipers.

602

[Bloke]

Your half right. The ONE TON (and possibly 6-pot Estates ) that have WIDER drums ... I think detailed in the parts book, but my understanding is that the drums are still 11" diameter. I'm happy to be corrected.

Can confirm the 6-pot's have 3" wide shoes.

[NoBeardNoTopKnot]

Exactly my fear and I suspect Glen's. Listing the parts book is well enough, only if that's the direction we're choosing to go, we're probably missing the core point. If we get the LR part number for shoes 30 foot wide, this won't take us far. Yes, they'll cool better and not wear out as fast. However, this can't change the fact - the friction they create remains a factor of the force we apply to them, not how wide they are.

Yet whenever this subject comes up, the numerous falsehoods will abound. Someone will bleat "and they're wider" as if to infer that'll make them more powerful. Er... no. Cooling and wear improvements aside, how in all that's holy could it?

We want wider shoes for that mountain-pass or the bottom of Porlock Hill. The distinction here is more subtle.

A few months back it was clear in one thread no one understood the differing  functions of the return springs. One set brings the shoes down on to the snails, the other acts as a rather poor RPV.

Yet no one ever says a word. This is worrying.

602's point about wheel diameter is valid in the extreme. Going from say (6.50 x 16) to (7.50 x 16) will degrade brakes. If we are looking in the parts book we're looking for the improbable 'ideal'... drums with TLS and the same diam. as the tyre.

For some reason, brake-threads seem to spout the most nonsense.  I detect Glen was fearful of shout-down for words contrary to herd-think. I'm pleased it's not just me? It's refreshing to read his words.