Brake Pad and Tyre Wear

[user 3172]

So my i3 went in yesterday to have the recall done on the potential fuel line problem. No issues there and I got the car back washed as usual. They did the cursory service checks while it was in.

After 15k miles, it was reporting 3mm across every tyre which didnt surprise me but I'm not sure what the depth they had to start so not sure how much wear / life that represents. Anyone got any idea?

The more surprising thing was a report of 50% brake pad wear on the front :shock: Now given that I don't drive like a saint, I would expect some wear but the vast majority of my braking is done on regen so 50% sounded pretty high. Anyone got any experience of replacement yet?

 

[theothertom]

Hi Gif and welcome to the forum.
I don't know about the tyre tread depth when new but 50% brake wear seems excessive. Maybe they measured it wrong ?

 

[rtanov]

The EP600 tires (19 inch) when new are 9/32" for the 155 size (front) and 10/32" for the 175 (rear) which is 7.1 & 7.9 mm. The legal limit here in the US is 2/32" which is ~1.6 mm, so you have quite a bit more than that. My tires after about 19k miles and 2.5 years are probably close to what you have left ~4/32". I'd say there's still some life left in them, although they show their age on the wet pavement.

The break pads have sensors - if it's not triggered I would not replace.

 

[user 3172]

Hi Gif and welcome to the forum.
I don't know about the tyre tread depth when new but 50% brake wear seems excessive. Maybe they measured it wrong ?

That was my first thought on the pads in terms of a pure guess measurement without any knowledge of their original thickness. Unless they are excessively soft, I can't see how I can have gone through 50% in 15k on a car with very strong regen.

Up until recently I had two tonnes of diesel Ford Kuga in my garage. I had only just replaced its front pads at 35k miles and I drove that harder with no regenerate at all.

 

[user 3172]

The EP600 tires (19 inch) when new are 9/32" for the 155 size (front) and 10/32" for the 175 (rear) which is 7.1 & 7.9 mm. The legal limit here in the US is 2/32" which is ~1.6 mm, so you have quite a bit more than that. My tires after about 19k miles and 2.5 years are probably close to what you have left ~4/32". I'd say there's still some life left in them, although they show their age on the wet pavement.

The break pads have sensors - if it's not triggered I would not replace.

So that makes my tyres 81% worn on the front and 77% worn on the back based on 1.6mm min. That gives range of around 19k for a set of fronts and 20k for a set of rears. Pleased with rears on that basis what with the obligatory traffic light dragging Fronts are a bit disappointing as I don't drive it hard in and out of corners.

Not changing the pads, must be a lot more wear in them than implied I think.

 

[MikeS]

Just had my i3 checked over after 17K miles and no mention of any significant wear on the brake pads…..

 

[brastic]

The tires on these cars wear fast. It is just nature of the beast. At least the tires are cheap. Well compared to my M3. My guess on the brakes is that they were not read correctly. Some BMW dealers are still learning how to work on the i3. As others have stated, the wear is measured by the car and there is no reason to replace till you either hear it or the dash tells you.

My big wish is for wider tires in the future. I would be willing to give up a bit of range for more lateral grip. I mean, my minivan can out handle the i3 in any corner.

 

[Bawareca]

I mean, my minivan can out handle the i3 in any corner.

It may feel so, but you will need a heavily modified van to out-corner the i3. Given the i3 is not a top performer, the g-loads feel very different in small and a large car.

 

[brastic]

I mean, my minivan can out handle the i3 in any corner.

It may feel so, but you will need a heavily modified van to out-corner the i3. Given the i3 is not a top performer, the g-loads feel very different in small and a large car.

Thank you for asking more about this. I had to go look it up. With our minivan, we replaced the stock tires with some summer tires and the difference in handling was noticeable. The i3 is a good driving car, and I do not regret owning it. I hope that we can get some better tires for it, even it means less range. From the C/D test below, the i3 is faster, brakes longer and has the same skip pad numbers. This is what I feel when I drive both cars. It was after replacing the tires on the minivan, where I noticed that my exit speeds on some corners was higher than my i3. Then again, neither of these cars handle like my M3, nor do I expect them to. I hope that BMW will sell us the i3s rims and tires.

C/D TEST RESULTS:
2017 BMW i3 BEV
Zero to 60 mph: 7.2 sec
Zero to 90 mph: 19.0 sec
Rolling start, 5-60 mph: 7.3 sec
Top gear, 30-50 mph: 2.7 sec
Top gear, 50-70 mph: 4.7 sec
Standing ¼-mile: 16.0 sec @ 85 mph
Top speed (governor limited): 92 mph
Braking, 70-0 mph: 184 ft
Roadholding, 300-ft-dia skidpad: 0.77 g


C/D TEST RESULTS FOR:
2015 Honda Odyssey Touring Elite
Zero to 60 mph: 7.7 sec
Zero to 100 mph: 21.0 sec
Zero to 110 mph: 26.9 sec
Rolling start, 5-60 mph: 7.7 sec
Top gear, 30-50 mph: 3.8 sec
Top gear, 50-70 mph: 5.5 sec
Standing ¼-mile: 15.9 sec @ 88 mph
Top speed (governor limited): 120 mph
Braking, 70-0 mph: 178 ft
Roadholding, 300-ft-dia skidpad: 0.77 g
C/D observed fuel economy: 22 mpg

 

[jadnashuanh]

On the i3s, the track is wider and the fenders are flared to make them fit, so not sure its wheels/tires will fit without maybe a bunch more cost than just the tires/wheels. Given that each are 0.5" wider, it may mean that you'd only need new rear wheels...the larger ones on the car now would be the same size as the new one for the front. That may mean that there is only one new tire size needed. Note, also, that those are currently summer tires...if you need all-seasons or winter tires, you'd have to go back to the 19" wheels and narrower tires front-rear. WIth the existing car, trying to put the 5.5" wheel on the front will lead to damage immediately after driving. The least expensive way to allow a wider tire without changing the suspension much is the flared fenders...that way, the inner clearances can remain the same. Given that the car is also lowered, that often can limit clearance, too.

Because the center of gravity on the i3 is so low, how the cornering feels doesn't correlate exactly the same to one that has more lean in the corner.

 

[user 3172]

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]

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?

 

[user 3172]

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]

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.

 

[alohart]

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.

 

[jadnashuanh]

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.

 

[alohart]

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.