Drum brakes making a comeback?

[Pugglt Auld Jock]

Somewhere in the murky depths of what masquerades as my memory these days, is an awareness that some of us were briefly talking about the problems electric cars, with their regenerative braking systems, are experiencing. The problem seems to very much revolve around the fact that regenerative braking cuts back on the use of conventional brakes to such an extent that the discs, especially on the rear, see so little use that they corrode rapidly and need to be renewed frequently.

My son in law's "ride" is a fully electric Skoda Enyaq 80 so it was with great interest that I observed this:



It's a rear wheel of course and, looking more closely, through the spokes of the wheel you can see:

Yes, a whopping great big drum brake!

The fronts are, unsurprisingly, discs, and pretty big ones at that - for comparison the wheels are 19" rims:



I think they are sensible and appropriate and certainly don't seem to be rusting any more quickly than on any other application. Discs on the rear of petrol engined vehicles rust quickly enough due to not having to do much work and getting blasted with all the road rubbish - grit, salt etc - from the front wheels. Electric cars compound this problem so much because the rear brakes do next to nothing. An enclosed drum brake of course gets round these problems to a very large extent. I like drum rears and would welcome them back on the majority of every day cars.

While I was dodging around looking at this I noticed the tyres - once a tyre man, always a tire man! - and noticed that apart from being quite a large diameter - 19 inch - wheel the tyres, at 225/50R19, were not outlandishly big considering the size of the car - Behemoth might be marginally overstating it? - But then I noticed this:



on the sidewall. It's a tyre specifically manufactured for electric vehicular use. Mentioned it to my son in law and he said "Oh yes, actually we had a puncture a few weeks ago, luckily a slow so I was able to drive to the garage." This vehicle is on some sort of lease deal so his garage directed him straight to a well known fast fit store who declared the tyre unrepairable and fitted a new one. He didn't have to pay as it's all covered by his maintenance agreement but he did inquire what it would have cost him. The chap was a bit evasive but mentioned "probably in excess of £200".

I also noticed the construction listing on the side of the tyre:

Which all looks quite "ordinary" in terms of sidewall and tread ply construction until I notice "Polyamide". Nylon, Rayon, Polyester and other less common materials I'm used to but, it looks like the world has moved on again because I've not seed Polyamide before. Went over to my Scala and, blow me, it's the same! You need to keep up young Jock!

Anyway, it then started to rain so we went back indoors to be greeted by the delightful sight of their dog, a Labradoodle, taking her ease on the corner setee:

It's where I usually sit and read my book but I hadn't the heart to disturb her!

 

[s130]

What is wrong with drum brakes as such?

Plus Points
o Trucks & Buses use them
o They have far more braking surface area
o More surface area = lower wear rate for shoes and drum
o Yes small slaves/pistons but they use mechanical advantage (nothing stopping bigger designs)
o Les hydraulic fluid required
o Potentially small brake travel required
o Very rarely get brake squeal

Minus Points
o Poorer potential cooling unless finned drums are used with possible more open wheel designs (which truck don't have!)
o Often requires drum removal to fully inspect linings but will often have inspection holes in backing plates
o Can bind if left applied (handbrake) in adverse weather / storage / etc. for long periods of time
o Not cool (as in boy racer with painted calipers, grooved and cross drilled placebo ego boosters )

I suspect that these modern drum brakes (compared to 60s/70s/80s/90s) are vastly improved.

 

[AndyRKett]

With many new electric cars having one pedal driving where you can literally speed up and slow down just off the accelerator, the brakes don’t get used at all, if they do it’s only lightly and most of that’s done on the front so I think several manufacturers have openly stated there is no point putting discs on the back as they would just rust and degrade without being used.

Drums on the other hand make for a much better more reliable hand brake, they are less likely to warp rust and generally deteriorate.

Many cars still use drum in disc for the hand brake, because disc hand brakes are just not as good, so it seems the engineers are doing some proper engineering and fitting what it needed rather than what looks good

 

[Pugglt Auld Jock]

What is wrong with drum brakes as such?

Plus Points
o Trucks & Buses use them
o They have far more braking surface area
o More surface area = lower wear rate for shoes and drum
o Yes small slaves/pistons but they use mechanical advantage (nothing stopping bigger designs)
o Les hydraulic fluid required
o Potentially small brake travel required
o Very rarely get brake squeal

Minus Points
o Poorer potential cooling unless finned drums are used with possible more open wheel designs (which truck don't have!)
o Often requires drum removal to fully inspect linings but will often have inspection holes in backing plates
o Can bind if left applied (handbrake) in adverse weather / storage / etc. for long periods of time
o Not cool (as in boy racer with painted calipers, grooved and cross drilled placebo ego boosters )

I suspect that these modern drum brakes (compared to 60s/70s/80s/90s) are vastly improved.

You don't have to try to "convert" me. I'd take a drum on the rear over a disc any day unless the vehicle is really high performance/heavy.

 

[Pugglt Auld Jock]

Many cars still use drum in disc for the hand brake, because disc hand brakes are just not as good, so it seems the engineers are doing some proper engineering and fitting what it needed rather than what looks good

I was interested to find the Ibiza had springs built into the handbrake cables which get compressed when you apply the handbrake lever. You can easily feel them as you pull the handbrake lever up. Great idea as it greatly reduces the risk of the handbrake loosing it's grip when the discs cool. I was pleased to find the Scala feels the same.

 

[StevenRB45]

Got to say our rear discs are a pain in the posterior, the Mazda ones were great they lasted 90k miles but I'm already one set in at 43k and eyeing up another set because they look like they've been at the bottom the sea.

I thought it was low miles originally...but the new set also looks like crap but at least they have shiny faces...if not wear lips on them after 25k.

All because some bright spark decided to fit 208 GTi rear beam (obviously with different springs and dampers) under the Diesel and Turbo petrol versions, it's nippy but it's not 180bhp cars neither fast enough or heavy enough to lean on them much unless you're doing it on purpose.

The only advantage I probably have over the drum cars is my hill start assist releases cleanly whereas when I've driven drum cars they seem to drag a little and pedal feel is a little bit more positive. Neither of these things make up for the fact that if it lives to 120k this car will likely have had 5 sets of rear discs.

 

[Pugglt Auld Jock]

The only advantage I probably have over the drum cars is my hill start assist releases cleanly whereas when I've driven drum cars they seem to drag a little and pedal feel is a little bit more positive. Neither of these things make up for the fact that if it lives to 120k this car will likely have had 5 sets of rear discs.

I've never got on with hill hold and never owned a car with an electric hand brake. However as I tend to apply the handbrake when stationary and select neutral then take my foot off the clutch, the hill hold doesn't activate anyway.

 

[StevenRB45]

But that would stop the engine in ours... because neutral and clutch up activates stop start.

So if you're creeping to an up hill junction that is proper annoying so tend to leave clutch down. Obviously if I'm there 5 minutes different story but for creeping forward as each car sees the way is clear and goes it would be on and off repeatedly in the space of 30 seconds.

That being the case it's easier to use the hill start assist, I could use the (manual) handbrake and not lift the clutch but it's very much 6 of one and half a dozen of the other.

 

[Pugglt Auld Jock]

But that would stop the engine in ours... because neutral and clutch up activates stop start.

But I cancel stop/start every time I start the engine so it wouldn't happen to me.

So if you're creeping to an up hill junction that is proper annoying so tend to leave clutch down. Obviously if I'm there 5 minutes different story but for creeping forward as each car sees the way is clear and goes it would be on and off repeatedly in the space of 30 seconds.

If creeping up hill I would be riding the clutch if I really have to - but staying stationary in neutral with foot off the clutch whenever reasonably possible - and using the hand brake to hold the vehicle.

That being the case it's easier to use the hill start assist, I could use the (manual) handbrake and not lift the clutch but it's very much 6 of one and half a dozen of the other.

Hill start assist just annoys the hell out of me because I feel the it hangs on for too long and then the clutch is momentarily fighting the hold of the brakes. In fact the Ibiza did it worse than the Scala. My standard practice whenever I come to a halt, whether on the level or on a slope, is to apply the handbrake - button depressed until fully applied, done it this way for years without any drama and it's easy with the Ibiza and Scala because you can feel the cable springs being tensioned. Then I "feel" for full engagement of the pawl as I relax the upward pull. - I've mentioned this in detail because I know some on here say you shouldn't do this but rather you should let the ratchet click over the teeth. Anyway, snick the gear lever into neutral and release the clutch pedal (unless it's very obvious I'm going to be needing to move again almost immediately. Only time I'd hold the car on the foot brake would be if it was an automatic and even then I'd likely apply the hand brake.

 

[The Panda Nut]

You don't have to try to "convert" me. I'd take a drum on the rear over a disc any day unless the vehicle is really high performance/heavy.

Me too, a re-convert. Rear discs mostly not worth the trouble. The Seat has a LOT less problems than the Fiats do. I wonder why.

 

[s130]

Hill start assist when towing and on a steep hill is a real pain and sometimes very dangerous. If you are unlucky and stall the car just when the automatic handbrake releases you end up rolling back. Worse still if you get to apply the handbrake via the switch you still have 0.5 to 1 second delay before the rear brakes are fully applied. Also it is not just the car but the towed item's weight that has to be stopped. On a hill the trailer/caravan draw bar is fully extended the their brakes will never engage.

Bloody dangerous IMHO and of course some numpty behind with have stopped to close to your trailer/caravan and out of sight.

As we all know with the traditional handbrake you learn to manually hill hold, pick up revs and clutch and then slowly release the handbrake in hopefully all in perfect harmony/synchronisation. Also if you stall the handbrake will be in that partly applied state during the release process and you already have your hand on it to rapidly pull it up.

I hate these modern cars built for lazy (but able, not disabled) idiots who can't drive properly.

 

[StevenRB45]

But I cancel stop/start every time I start the engine so it wouldn't happen to me.

If creeping up hill I would be riding the clutch if I really have to - but staying stationary in neutral with foot off the clutch whenever reasonably possible - and using the hand brake to hold the vehicle.

Hill start assist just annoys the hell out of me because I feel the it hangs on for too long and then the clutch is momentarily fighting the hold of the brakes. In fact the Ibiza did it worse than the Scala. My standard practice whenever I come to a halt, whether on the level or on a slope, is to apply the handbrake - button depressed until fully applied, done it this way for years without any drama and it's easy with the Ibiza and Scala because you can feel the cable springs being tensioned. Then I "feel" for full engagement of the pawl as I relax the upward pull. - I've mentioned this in detail because I know some on here say you shouldn't do this but rather you should let the ratchet click over the teeth. Anyway, snick the gear lever into neutral and release the clutch pedal (unless it's very obvious I'm going to be needing to move again almost immediately. Only time I'd hold the car on the foot brake would be if it was an automatic and even then I'd likely apply the hand brake.

I would say horses for courses...if it works competently then it's there for your use. There are situations I'll ignore it and use the handbrake but in the case of the example given it's usually stop, move 5 feet, stop move five feet... repeat until you reach stop line and stop, check right for clearance then peep and creep until you possibly have to stop again if once you can see round a parked clear it's not clear then one final hill start and you're away. Obviously entirely possible with a handbrake, did it for many years...much easier with hill start assist.

Obviously if it drags the cars arse like a dog with worms then the manufacturer hasn't set it up right. My observation was more having driven versions of our car with rear drums they don't release cleanly or grab as cleanly as discs..making it more annoying and less useful.

Same with the stop start... commuting into work there's times the engine has been off 20 minutes in an hour commute. So it stays on but similar to the hill start assist I'm aware of what it doesn't do and how to get to do what I want to do not what it wants to do.