4 ms·
"As long as you're not losing traction on your rear wheels" is the key part. The more you brake, the more weight shifts forward, which results in less traction
by kenhwang 3y ago
"As long as you're not losing traction on your rear wheels" is the key part.
The more you brake, the more weight shifts forward, which results in less traction available to use to recapture.
People vastly overestimate how much traction is available at the rear during braking, and running out of traction at the rear typically results in the car spinning (especially in an EV with low rotational inertia with most of the weight between the axles) so regen tends to be very conservatively tuned to not cause rear lock up, thus using even less of the little traction available.
- frosted-flakes 3y agoThis is obvious to anyone who's changed the brakes on their car. Front brakes are massive compared to the rear.
- scottyah 3y agoAlso people who ride dirt bikes- the back will slide out fairly easily compared to the front (but using the front exclusively comes with some pretty big tradeoffs)
- skeeter2020 3y agoOr used any vehicle with independent front/rear braking like a motorcycle or bike. The rear is for fine tuning while the front is for actually stopping.
- adrianmonk 3y agoAlso anyone who has ridden a bicycle.
- thomastjeffery 3y agoIn that case, leaning back makes a surprising amount of difference.
- akira2501 3y agoThey're both for stopping. It's why they're biased to have more power in the front than the rear. You can take advantage of this with the rear to "tune" in some situations, or to maintain stability at low speeds, but it should also be fully used when braking.
- bluGill 3y agoNot on more modern cars. In an emergency stop situation the front brakes still do the work, but in normal more gradual stop situations traction control biases to the back wheels as much as possible so the front wheels can steer.
- the_third_wave 3y ago...or to anyone who ever rode a bicycle or motorbike with front and back brakes. Pull (bicycle) or press (motorbike) the back brake hard and the rear wheel tends to skid. Pull the front brake hard and the thing wants to somersault. The back brake is needed to stabilise the vehicle but the front brake does the real work.
- robocat 3y agoRear-wheel energy recapture is surely fine so long as you are braking normally. Similar to driving a rear wheel drive car and just using engine braking. Yes, when braking strongly rear wheels alone certainly don’t have enough traction: signs of strong front wheel braking are the nose of the car starts to dip and your passengers are complaining! Similar issue with slippery surfaces and no ABS (regenerative traction control)? I would be interested to see some real-world figures of how often rear-wheel-only regenerative braking hits limits and wastes power. In addition, are there limits to the amount of power regenerative braking can push into the batteries? I presume that even on front-wheel regenerative braking, when heavy braking occurs the front calliper is engaged and energy is lost. The theoretical difference between front and rear regeneration might not matter in practice? Disclaimer: I don’t know much about this, and I suspect you are technically correct, but my guess is that it doesn’t matter in reality, and other constraints/costs/benefits matter more for deciding on front vs rear wheel drive.
- amluto 3y agoRear wheel regenerative braking (with a decent traction control system, which is table stakes) is fairly effective, but the down side is reduced life span of the rear wheels.
- ajross 3y agoRegen breaking never comes anywhere near the traction limits though. I don't follow the point.