Thread: Handbrake conversion to disc : Defender

Had a x-eng disc handbrake in my 90. Definitely better in water/mud where the drum would fill up and wear out of adjustment quickly. I hadn't done heavy towing with it though, but definitely an improvement in muddy off-road conditions.

Originally Posted by isuzurover

I have also had a lot of issues with mine. I am at the end of the adjustment and it won't hold on my driveway...

There are three adjustments on then. The first and most obvious is on the cable. As pads wear and/or cable stretches its quite easy to get to the en of the adjustment.

The second is attaching the cable to one of the three holes in the lever arm.

The third method of adjusting is course and so gives you the most "get you in the right area" type of adjustment. Take the unit off and you can rotate the arm around the splined spigot.

To say the brake can't hold the car on the driveway is rubbish. It's simply but adjusted correctly.

Download the install manual from the X-Eng site and have a look at adjusting. It's far more descriptive than above and has pictures!

Good luck.
Jon

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Originally Posted by uninformed

... you guys do realise that the original drum brake has more area and holding force than that disc right??...

That's as maybe but the point made is irrelevant.

For whatever reason, the X-Eng unit is much better, more effective and more reliable than the factory unit. It just is!

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Originally Posted by Yorkshire_Jon

That's as maybe but the point made is irrelevant.

For whatever reason, the X-Eng unit is much better, more effective and more reliable than the factory unit. It just is!

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Agreed

the point about the amount of friction material is not valid at all.

Infact, the less material the better the grip, otherwise the pads on disc brakes would be huge, and have you ever seen the clutch friction plate from a Mack truck

Count me in Lou.
Towing a camper make me very interested.

Cheers,
Paul.

Originally Posted by harro

Count me in Lou.
Towing a camper make me very interested.

Cheers,
Paul.

Hi Paul

the thread is 4years old

Originally Posted by goingbush

Agreed

the point about the amount of friction material is not valid at all.

Infact, the less material the better the grip, otherwise the pads on disc brakes would be huge, and have you ever seen the clutch friction plate from a Mack truck

umm, I think you need to rethink your last statement....Friction is basically a combination of materials, surface area and pressure. Given the materials are basically the same (drum/disc and pads) It comes down to pressure. Your disc pad needs more pressure to have the same holding force as the larger drum pads.

Forget heat build up etc as this is a holding brake, not a slowing, rotating brake.

Your mack truck gets away with less surface area due to very high forces. I doubt the clutch is operated via a cable and lever

Originally Posted by uninformed

umm, I think you need to rethink your last statement....Friction is basically a combination of materials, surface area and pressure. Given the materials are basically the same (drum/disc and pads) It comes down to pressure. Your disc pad needs more pressure to have the same holding force as the larger drum pads.

Forget heat build up etc as this is a holding brake, not a slowing, rotating brake.

Your mack truck gets away with less surface area due to very high forces. I doubt the clutch is operated via a cable and lever

Not quite correct.
Friction is a product of 'friction coefficient' and 'normal force'.

'friction coefficient' is a material property usually between 0.35 and 0.5 for brake and clutch linings.

'normal force' is the component of the force perpendicular to the friction surface.

Force = pressure x area

For a given normal force, the pressure is reduced if the area is increased, but the only reason we are interested in pressure for brakes and clutches is for the wear rate, which is a function of pressure x sliding velocity. If the brake doesn't slip there will be no wear to speak of.

With a brake we are interested in the braking torque achieved = friction force x radius. This becomes more complex than this simple equation indicates.

With a clutch or disc brake, where is radius measured? I won't go into a correct determination but it will be somewhere near the radius to the centre of area of the brake pad contact with the disc.

With the drum brake the braking torque is much more complicated, because the issue of leading and trailing shoes affects the outcome, etc., but the effective diameter is usually larger than for a brake disc that fits within the same package envelope. The friction on leading shoes cause the braking force to increase (self energisation), and the reverse happens for trailing shoes.

The disc pad doesn't need more pressure than a drum brake, it needs more force, because the effective radius is less and there is no self energisation like with leading shoes.

However when the force is increased, if the area remains constant, then the pressure will increase as a consequence, but that is a side effect, which does nothing for braking torque.