Rear drum to disc conversion?

[russtik]

What are the pros and cons of converting a (kit) car from rear drums to disc brakes, on an IRS car that's used on the road more than track?

Overall, worth the bother if the parts were easily accessible?

[jeffw]

Yes, worth it. The balance under braking was a big improvement when I did mine.

[Tony C]

Not sure I'd bother, from what I've read previously the brake balance needs to be adjusted so the rear doesn't try to overtake the front, effectively making them no more efficient than the drums you've taken off, nicer to look at and easier to work on though. Only ever bothered on an old SJ Suzuki which I used for green laning as a set of shoes would only last a single outing sometimes. Not planning any green laning, are you?

[DJ.]

As I understand it, the advantage discs have over drums is better cooling. It's very unlikely such a light car will overheat its brakes in road use even the way you drive . So, I would save your money.

[Wingco]

I had my old kit converted to discs, Ross and my self did the job. I thought the braking was a lot better after the conversion, it seemed to stop quicker and that gave me confidence in the car. Or were my old brakes just poor ? I asked Dick about doing a conversion on my new Tiger and he said why ? on his Tiger with all that HP he has drums on the rear, says it all really.

[Jay]

Sorry colin some confusion. Dad has discs with twin pot rear calipers and it needs them.

[Wingco]

Sorry guys my mistake must of herd him incorrectly. I’ll disappear with out a trace.

[Fury1630]

By reputation drums are lighter, not sure if there's any science behind that. I've just swapped from 9" drums to 8" drums because the rears sometimes locked & on the way home from Billy's last Sunday a moment's inattention proved that they don't any more (ahem ). The handbrake is a separate issue, but the drums on the Fury are excellent in that respect.

Can you adjust the bias? As Tony C said, you'll need to turn down the tap at the back, so if you've got a tandem master cylinder, you're into more engineering to make the rear's adjustable.

I have been told that on a rear wheel drive car the rear brakes only do 25% of the braking, on a front wheel drive car it's only 10% - I'm not sure that's true - I think it's probably true for the TYRES because engine braking is contributing to the braking on each axle. But even if it is 25% you'd need to improve the efficiency of the brakes a hell of a lot to make a noticeable difference.

Discs cool faster so are less prone to fade, but on a 600kg road car, they probably don't get more than tepid. They are easier to service, but after 30,000 miles, the linings in the drums I took off were showing no real signs of wear, so one set will probably last the life of the car.

It's one of those "you pays your money & takes your choice" things really. If my donor car had had discs, I'd have fitted them, it didn't so I have drums.

[Tony B]

You looking for something to take your car off the road for another 6 months??

I did this conversion on my old GBS and had to make sure I biased towards the front afterwards cos the back locked up far too easy - it’s as Dunc has said I think, in our light cars drums are more probably better - however in my opinion discs all round look far better

See you next April .....

[David T]

Have thought about doing this a few times, but have never quite convinced myself it is worthwhile.