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There has been some debate over fitment of rear drums to ID3

Heres some illustrative calcs, please feel free to amend or update.

a 1700kg car is travelling at 124 km/h.
If the car has to brake to zero, the kinetic energy to be dissipated is approx 1MJ (ignore any energy lost to air friction which would be true if the braking was instantaneous). The same car descends down a small hill of 60m, and the gravitational energy to be dissipated is again 1MJ (lets say 0.3 kWh).

Now if there is no regen, that kinetic energy has to be absorbed by the brakes. For high speed braking, brake bias will be mostly to the front, rears will only have to do say 20% of the braking. Lets assume rear cast iron drums have 16kg mass, no heat dissipation to the air (because we know drums are bad for heat dissipation). The temperature rise of the rear drums will now be a massive 26 degC (sorry being ironic, 26 degC rise will be fine).

Not a problem, even with the same assumptions, two stops from 124 km/hr should be possible.

Now think about the gravitational energy: lets make that 60m hill a 300m hill. Suddenly we are in real trouble, the rear brakes will suffer terrible fade (or we better hope that there is some cooling fins etc). But so long as we have regen, sufficient battery capacity to absorb the 1.5kWh generated no problems, it should all be stable.

Looks like barring track days, the rear ID3 drums are a very good solution thermally.
 

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VW ID.3 Worst Edition & Tesla M3 LR
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Looks like barring track days, the rear ID3 drums are a very good solution thermally.
Yeah, but not on a £30k+ car, lolz....

I like your working out, and really don’t see the issue with them on a road car.

I was wondering yesterday how it would cope with multiple high speed stops on the Autobahn, but then remembered its limited to 99mph...

I’ve noticed that the ID.3 drums are a little more elaborate than the ID.4 ones, the casting seems to have dimples which might be to aid cooling or are for structural or even aesthetic reasons?
 

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The regen provides up to 0.25g worth of braking effect before the mechanical brakes kick in. That's plenty for most road driving.

I'm curious what will be changed when the "R" version comes out. Will that have closer to 0.5g worth of regen ability with there being two motors? I'm sure it's not that simple but I'm still curious about it.

That will please those that are allergic to the brake pedal and demand 1 pedal driving.
 

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VW ID.3 Worst Edition & Tesla M3 LR
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I'm curious what will be changed when the "R" version comes out. Will that have closer to 0.5g worth of regen ability with there being two motors? I'm sure it's not that simple but I'm still curious about it.
Me too. If they do release it, I expect it will have rear disk brakes, even though technically it might not need them.

Firstly, to differentiate it from the ‘cooking’ models, and second because the potential market will expect it I suppose.

Any extra maintenance due to lack of use will be less of an issue on the performance variant, it kind of goes with the territory.

They could remove the maintenance requirement by specifying carbon ceramic brakes I suppose, but it would be a high price point with those.

Looking at the pre-release videos of the KIA EV5 GT, looks like big brake kits could be back in vogue. 🙂
 

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Carbon ceramics on an ID3? Overkill but I still want it!

I'm sure the all up weight and if the top speed changes beyond 99mph will be the defining factors but I foresee gearbox changes and that will just drive costs northwards.

350/400bhp in an ID3 that still does around 200 miles in the winter would be interesting!
 

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If your brakes are overheating on an autobahn, preventing an emergency stop, you're definitely doing it wrong! In fact, if your brakes are overheating, you're not driving efficiently, which is sort of the point of these non-lightspeed-performance EVs...

It's clearly a cost saving measure but I would wager that in an electric nearly all the heat generated by repetitive braking is a moot point due to regen doing most of that on/off work, unless you're at the ring or something. So, it makes sense. And, as an owner, they are cheaper to maintain... which is a ... good thing!

It wasn't long ago EV owners were boasting about not needing brakes, what happened!
 

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If your brakes are overheating on an autobahn, preventing an emergency stop, you're definitely doing it wrong! In fact, if your brakes are overheating, you're not driving efficiently, which is sort of the point of these non-lightspeed-performance EVs...

It's clearly a cost saving measure but I would wager that in an electric nearly all the heat generated by repetitive braking is a moot point due to regen doing most of that on/off work, unless you're at the ring or something. So, it makes sense. And, as an owner, they are cheaper to maintain... which is a ... good thing!

It wasn't long ago EV owners were boasting about not needing brakes, what happened!
What happened is people who worry about share prices and not cars are commenting a lot.
The more EV options the better and the style variations to suit more people the better.
 

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What happened is people who worry about share prices and not cars are commenting a lot.
The more EV options the better and the style variations to suit more people the better.
I think that you have hit it on the head.
Many of the comments in this thread treat brakes as a style item.

Who was it that started the fashion for painting brake calipers bright colours? I blame him.
 

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Mm, I’m not sure.

What colour did you go for on the Zoe?
Well the drums on the Zoe rust within a year from new, so this would be a neat solution.

But as you know with me I’m a kind of ‘out and proud’ kind of guy. So I treated the drums to a can of Hammerite silver paint.

You can judge me all you want. :)
 

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It's clearly a cost saving measure
I disagree. There's nothing fundamentally cheap about drum brakes - on my go faster car I have a set of magnesium :eek: alloy drums which cost similar to modern ceramic brakes (it's best 1935 technology).
For an EV rear brake a drum offers a low corrosion solution and an excellent handbrake. In "normal" road use they will not fade, and cooling technology exists (since at least 1935) to allow them to be used in race situations with no problems.
 

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Well the drums on the Zoe rust within a year from new, so this would be a neat solution.

But as you know with me I’m a kind of ‘out and proud’ kind of guy. So I treated the drums to a can of Hammerite silver paint.

You can judge me all you want. :)
The rear discs, in particular the bell over the internal drums on the LEAF, rust badly due to zero surface treatment from the factory. I'm still thinking about painting the non-friction surface but am only put off by it being very mini-cab style to do so. :rolleyes: It's strange that so many owners are willing to allow such a large visible patch of corrosion to remain on their cars when they obsess about the rest of their car's appearance.
 
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