ABS and Autohold Question

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syntaxfx
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ABS and Autohold Question

Post by syntaxfx »

I'm waiting for my Kona EV. It's to replace a VW Tiguan of "dieselgate" fame.
The Tiguan, like the Kona EV has an Autohold function that basically stops the brake fluid from leaving the wheel cylinders once the wheels stop turning, until you touch the throttle.
It's a helpful thing in traffic and over time, I got into the habit of leaving it switched on until one day when I made an emergency stop in the wet.
I expected the ABS to kick in but once the wheels had locked, Autohold kept them that way.

Does anyone know if the Kona EV's Autohold does the same trick?

Btw, no Tiguans were harmed in making this discovery.

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brendon_m
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Re: ABS and Autohold Question

Post by brendon_m »

Auto hold should not interfere with ABS on any car. Chances are that you just didn't hit the threshold for ABS to operate.
Essentially the ABS module monitors each wheels speed and if detects that a wheel is slowing faster than the car could possibly be slowing down (ie it's skidding /slipping) then it will release the brake to let it spin again and reapply doing the same check.
My best guess (without knowing all the circumstances) is you were already going below the minimum speed ABS will kick in or the car assumed it was possible to come to a stop in the time that the wheels took to slow down and skid.
Unfortunately the ABS only has the data from the wheel speed sensors and it has to guess what the rest of the car is doing from there. Maybe manufacturers should include a high accuracy GPS for actual vehicle speed.

davidEV
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Re: ABS and Autohold Question

Post by davidEV »

I have used Auto hold when picking up my Grandaughter from school while parking on a upward incline. I found it hard to release Auto hold because one had to brake and look down to push the Auto hold button. Also the manual states that the Auto hold should be released before going downhill As per manuel 5-36 onwards Electronic Parking Brake (EPB) is applied if sitting for 10 minutes. I found it better to stop on the slope by using the left paddle pulled back. From memory I think the EPG is applied also after 10 minutes of waiting. I continually successfully stopped on the slope using the left paddle without any problem and so found it so easy instead having to always remember to push the Auto hold button before going downhill.
Regards David

syntaxfx
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Re: ABS and Autohold Question

Post by syntaxfx »

Hi Brendon,
brendon_m wrote:
Tue, 11 Feb 2020, 06:03
Auto hold should not interfere with ABS on any car.
I completely agree.
brendon_m wrote:
Tue, 11 Feb 2020, 06:03
Chances are that you just didn't hit the threshold for ABS to operate.
Yeah, that's possible. The skid was about 6ft on a greasy road. However, getting off the brake didn't unlock the wheels - which was the disconcerting bit.

Cheers,
Phil

syntaxfx
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Re: ABS and Autohold Question

Post by syntaxfx »

davidEV wrote:
Tue, 11 Feb 2020, 08:24
I found it hard to release Auto hold because one had to brake and look down to push the Auto hold button.
Also the manual states that the Auto hold should be released before going downhill.
Hmmm. On the Tiguan, just pressing the accelerator releases the brakes after stopping with autohold.
davidEV wrote:
Tue, 11 Feb 2020, 08:24
I found it better to stop on the slope by using the left paddle pulled back. From memory I think the EPG is applied also after 10 minutes of waiting. I continually successfully stopped on the slope using the left paddle without any problem and so found it so easy instead having to always remember to push the Auto hold button before going downhill.
Regards David
Seems I have some new methods of driving to learn about when the Kona arrives. :o

Cheers,
Phil

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jeffthewalker
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Re: ABS and Autohold Question

Post by jeffthewalker »

syntaxfx "Hmmm. On the Tiguan, just pressing the accelerator releases the brakes after stopping with auto-hold."

I had an 'interesting' experience with my LEAF.

I was remote, rural and stopped at a gate on a slight down slope. I applied the (electric) hand brake and started to exit. Due to age and size, I shuffled a bit getting out. That is, open the door, right leg out, swivel body a bit then left leg from "clutch area" to "gas pedal area" ready for final swivel and push to climb out.

With most of my body bulk out of the car, I gave a bit of a push with my left foot to finish off the action.

And.... accidentally nicked the accelerator. Bingo, hand brake released creep mode and gravity did the rest.

Half in and half out I managed to find the brake pedal and prevented the LEAF from taking a swim in the creek crossing.

Lesson: Hand brake AND select PARK or don't get used to auto-hold for every occasion:-).

EDIT: Nissan (and others) apply brakes if no bum on drivers seat. Extra press on accelerator (or something ) to override.
It is hard to make predictions, especially about the future. Yogi Berra

reecho
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Re: ABS and Autohold Question

Post by reecho »

syntaxfx wrote:
Tue, 11 Feb 2020, 05:31
I'm waiting for my Kona EV. It's to replace a VW Tiguan of "dieselgate" fame.
The Tiguan, like the Kona EV has an Autohold function that basically stops the brake fluid from leaving the wheel cylinders once the wheels stop turning, until you touch the throttle.
It's a helpful thing in traffic and over time, I got into the habit of leaving it switched on until one day when I made an emergency stop in the wet.
I expected the ABS to kick in but once the wheels had locked, Autohold kept them that way.

Does anyone know if the Kona EV's Autohold does the same trick?

Btw, no Tiguans were harmed in making this discovery.
Yes it works the same. It does default to off though.

syntaxfx
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Re: ABS and Autohold Question

Post by syntaxfx »

reecho wrote:
Wed, 12 Feb 2020, 07:43
syntaxfx wrote:
Tue, 11 Feb 2020, 05:31
Does anyone know if the Kona EV's Autohold does the same trick?
Yes it works the same. It does default to off though.
Many thanks for that. I'll be leaving it switched off.

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