Gif
Posts: 237
Joined: Mon Jun 06, 2016 12:24 pm
Location: Bottom right hand corner of Wales

Re: Brake Pad and Tyre Wear

Sat Jun 23, 2018 12:17 am

Just to follow up on this old thread, I had the car in for the wheel check (see my other thread) and they did the usual courtesy safety and maintenance checks. Brake pads reported with 7mm (F) and 8mm (R) depth remaining after 28k miles so the original reading I had was plain wrong I am guessing :roll:

Mick787
Posts: 53
Joined: Wed Jul 11, 2018 2:43 pm

Re: Brake Pad and Tyre Wear

Mon Jul 16, 2018 1:51 am

Once again, I say we hope to collect our Rex this week here in the UK.
Whilst out on the test drive, the salesman stated that one foot driving will become the norm' however, 'backing off' on the accelerator caused brake pad wear and we should expect brake pads to wear quicker? I thought this to be rather odd, especially because of the supposed re generation which I understood takes place when 'backing off'. I thought this decrease in speed was much like engine braking in a manually geared car with a conventional engine and wouldn't affect brake pad wear. I have to say, my impression of the salesman's knowledge of the workings of the car wasn't that good, so perhaps one of the experts out there could clarify, does backing off and causing re generation cause brake pad and disc wear?

Gif
Posts: 237
Joined: Mon Jun 06, 2016 12:24 pm
Location: Bottom right hand corner of Wales

Re: Brake Pad and Tyre Wear

Mon Jul 16, 2018 6:21 am

I’m no expert but my understanding was very much the same which is why I questioned the original assessment of my pads.

I think there are two possible issues at play.

Firstly, your car can’t regenerate when the battery is close to full as there’s nowhere for the energy to be stored. This causes a lack of regenerative braking force and possible traditional braking as an alternative as there is no engine braking going on. How this would cause ‘more’ wear than in an ICE I have no idea as it would still represent a significant overall reduction in brake use and consequential wear over an ICE which uses pads to some degree 100% of the time even with engine braking.

Secondly and I have seen this commented on elsewhere, lack of regular brake use could result in a much less clean brake disc surface. Use of brake pads could result in extra wear when they have to first bite on a surface which needs cleaning back to bare metal. There is an issue here as I’ve noticed brake efficiency is not great when first used after a long period of rest.

Whether all this adds up to greater pad wear I’m doubtful. I would suggest that the regular use of normal braking in an ICE weighing far more and generally from greater possible speeds (EV drivers don’t generally thrash around all the time and certainly don’t travel at high motorway speeds) would result in greater brake wear.

Anyway, after 30k miles, I seem to have loads of pad left so not a great concern any longer.

jadnashuanh
Posts: 4990
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Brake Pad and Tyre Wear

Mon Jul 16, 2018 12:59 pm

There are three possible ways the brakes will be activated:
- you press them
- when the battery is essentially totally full and you let off on the accelerator pedal - regen works when there's room in the battery, which is most of the time. The computer does this to try to make the slowing nearly the same whether it is done by regen or can't if the battery is full.
- if the car senses an emergency situation where slowing will help in safety

It's not uncommon for salesmen to not have a clue on the vehicles they sell. It's kind of sad, and says something about their professionalism, but the best defense is a well informed buyer.

I seem to remember that the car will activate disk drying when it senses it is wet out, but you don't really notice that as the pads just start to skim the disks to clear them of water...not try to slow you down. IOW, that should not really cause any wear.

As a result, the pads on the i3 should last a VERY long time unless you charge to a stop and require pressing them and don't maximize regen for slowing purposes. As a result, the disks get a light rust coating, so it actually helps once in awhile to do an emergency stop to help clean them up when it is safe to do so.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

alohart
Posts: 2074
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Brake Pad and Tyre Wear

Mon Jul 16, 2018 3:48 pm

jadnashuanh wrote:There are three possible ways the brakes will be activated:
I have noticed a 4th situation: when driving under the control of ACC and regen deceleration to avoid a vehicle or an obstacle ahead would be insufficient to avoid a collision.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

jadnashuanh
Posts: 4990
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Brake Pad and Tyre Wear

Mon Jul 16, 2018 8:56 pm

alohart wrote:
jadnashuanh wrote:There are three possible ways the brakes will be activated:
I have noticed a 4th situation: when driving under the control of ACC and regen deceleration to avoid a vehicle or an obstacle ahead would be insufficient to avoid a collision.
Seems to fit into my third point, but hey, the car is fairly smart. Keep in mind that the car still needs to be driven...don't get lulled into becoming complacent. The camera has its limitations. Both lighting and especially contrast can cause it to fail to react. Don't become a statistic, drive the car.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

alohart
Posts: 2074
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Brake Pad and Tyre Wear

Tue Jul 17, 2018 11:26 am

jadnashuanh wrote:
alohart wrote:
jadnashuanh wrote:There are three possible ways the brakes will be activated:
I have noticed a 4th situation: when driving under the control of ACC and regen deceleration to avoid a vehicle or an obstacle ahead would be insufficient to avoid a collision.
Seems to fit into my third point, but hey, the car is fairly smart.
I assumed that your 3rd point describes when emergency braking occurs to avoid a pedestrian or car at low speeds which could occur without ACC being on whereas my 4th point is just normal ACC operation that could occur at any speed.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

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