[Lotus99]

I’m guessing there’s only 5 mm or 1/5" of space between the brake caliper and my wheel right now! My pinky is 1 cm or 2/5".

I’ve seen a lot of people say they have put 8" wide / 35 offset wheels, and the outer edge would RETRACT by 11 millimeters based on the calculators. Tire Rack even suggests 8" / 32 offset wheels, which still retract 8 mm...

Even 8.5" wide wheels with 35 offset would RETRACT 5 mm, which would be too close for my comfort...


.

[asyvan]

You do know that offset is the distance from the center of the rim to the base that attaches to the car. See pic. Bmw have positive offset.

[asyvan]

It really doesn't matter. What clears the calipers is the design of the rim.

[Lotus99]

Originally Posted by asyvan

You do know that offset is the distance from the center of the rim to the base that attaches to the car. Bmw have positive offset.

It really doesn't matter. What clears the calipers is the design of the rim.

Of course each wheel's design is important. So much so that on my M2C that needs 19" wheels for its front brakes, many aftermarket 19" wheels don't fit without spacers. I know, cuz I got winters for it.

And I know what offset is. USUALLY the lower you go, the less brake caliper clearance you have as a rule of thumb.

So I'm not going to take a chance, unless I have a decent idea it should fit. With TireRack, I know they guarantee fit, and I'm sure I can trust them, but I was hoping someone actually knows the answer to my question...

[asyvan]

Well I am not sure your question CAN be answered. Look at it this way, if you have a rim of a certain design that comes at different offsets to choose from. And if that design clears your brake calipers.... then that same design will clear the calipers no matter what offset you choose.

[dkreidel]

A bigger concern on the M40i is tire/suspension clearance in the front. Some owners who added wider tires of the same diameter found they are either hit the upright, or are now dangerously close.

Another area of concern, especially on winter set-ups, is not simple static caliper clearance. Sufficient clearance between the caliper and wheel is required, as the heated caliper causes snow and ice to melt, and then re-freeze - essentially freezing the caliper to the wheel barrel

[asyvan]

Originally Posted by dkreidel

A bigger concern on the M40i is tire/suspension clearance in the front. Some owners who added wider tires of the same diameter found they are either hit the upright, or are now dangerously close.

Another area of concern, especially on winter set-ups, is not simple static caliper clearance. Sufficient clearance between the caliper and wheel is required, as the heated caliper causes snow and ice to melt, and then re-freeze - essentially freezing the caliper to the wheel barrel

Yes on suspension clearance.

On freezing calipers. Never heard of. I live in Northern Sweden though, so... 😎

[taketheturns]

Offset has less to do with caliper clearance than with the hub disk. A lot of manufacturers will ask you what car the wheels are going on, and this will allow them to provide you the proper sized disk. Depending on the wheel design (spokes, 1-3 piece wheels), you might be able to get away with low disk and lower offset on a bigger caliper like on the m40i. This is a risky way to do it.

These are the disk choices from WORK Wheels. You can see the part that meets the hub is larger for bigger calipers.

[dkreidel]

Originally Posted by asyvan

Yes on suspension clearance.

On freezing calipers. Never heard of. I live in Northern Sweden though, so... 😎

Heat from the rotors and calipers causes snow and ice to drip onto the caliper and freeze hard to the barrel if there is insufficient radial clearance between the barrel and caliper - If you don't have ~10 mm of clearance it only takes an hour or so to lock them up at temps <-15C. If both front calipers ice freeze to the wheel barrel it is very difficult to break them loose w/o heat. I have a Ford with only 5mm clearance to the big Brembo calipers, and it freezes regularly

Rocks and small pebbles can cause problems even when it's warm. I think it's possible to have adequate clearance for when things are good, but have problems when the roads haven't been plowed and have 20-30 cm of snow and ice.

I've spend some winter time in SE for work, and will put our Montana winters up to the worst SE can offer.

[asyvan]

Originally Posted by dkreidel

I've spend some winter time in SE for work, and will put our Montana winters up to the worst SE can offer.

Oh I have no doubt about that. We are sooo far north of you (Stockholm and Anchorage are about the same north) but our winters are milder than what the location says thanks to the Gulf stream.

Where I live we have snow from end November til end March and it reaches roughly 1 meter (roughly 3 feet 4 inches) deep in terrain. Temperature is usually around 5-10 below freezing, but can get much colder in periods.

[dkreidel]

Originally Posted by asyvan

Oh I have no doubt about that. We are sooo far north of you (Stockholm and Anchorage are about the same north) but our winters are milder than what the location says thanks to the Gulf stream.

Where I live we have snow from end November til end March and it reaches roughly 1 meter (roughly 3 feet 4 inches) deep in terrain. Temperature is usually around 5-10 below freezing, but can get much colder in periods.

Oh, I dream of 1 meter of snow! We had more than 1 meter in one day of October of this year, and last year the valleys of our local mountains received just over 21 meters of snow; more on top. It's usually late July before it's all melted. I am near Glacier National Park.

[Lotus99]

Originally Posted by taketheturns

Offset has less to do with caliper clearance than with the hub disk. A lot of manufacturers will ask you what car the wheels are going on, and this will allow them to provide you the proper sized disk. Depending on the wheel design (spokes, 1-3 piece wheels), you might be able to get away with low disk and lower offset on a bigger caliper like on the m40i. This is a risky way to do it.

These are the disk choices from WORK Wheels. You can see the part that meets the hub is larger for bigger calipers.

Thank you for that diagram and explanation. All good wheel companies know that intuitively I suppose, but I don't think I've ever seen it as part of the specs of a wheel (probably because it would overcomplicate things for most).

I went thru all this last year when shopping for winter wheels for my M2C, which has like 5 mm clearance between the calipers in the front and the wheel barrel. I'm down to 4 mm with the winter wheels set up. That's exactly why Apex doesn't list all their 19" wheels with the same offset as fitting my car... My OEM wheel is 9 x 19, ET 29, and not every 9" wide 19" wheel with 30 offset will even clear my calipers.

What I've been trying to say is that everything else being equal (in other words if you had the same shape spokes between wheels), the lower the offset, the more brake caliper clearance you will have.
.

[asyvan]

Originally Posted by Lotus99

What I've been trying to say is that everything else being equal (in other words if you had the same shape spokes between wheels), the lower the offset, the more brake caliper clearance you will have.

Here is a picture I made to show just that.
Imagine these three rims/wheels being same width, same design and three different offsets.

[plainmaster]

Originally Posted by Lotus99

And I know what offset is. USUALLY the lower you go, the less brake caliper clearance you have as a rule of thumb.

Isn’t that the exact OPPOSITE of what is true? The lower you go (less offset) the more brake caliper clearance you should have.

Look at the picture above of negative offset. The spokes are FURTHER away from the hub, not closer, as in positive offset.

[dkreidel]

Originally Posted by plainmaster

Isn’t that the exact OPPOSITE of what is true? The lower you go (less offset) the more brake caliper clearance you should have.

Look at the picture above of negative offset. The spokes are FURTHER away from the hub, not closer, as in positive offset.

It really depends upon the specific wheel configuration. In some wheels, the spoke position relative to the hub datum remains constant as offset varies, but on other wheels the back of the spoke face can move relative to the hub datum.

The only way to be certain is mount a wheel to the car and inspect for caliper and suspension clearance. On X3 AWD cars, there's another clearance concern point with the front suspension and inside edge of the tire if the tires have a larger section width and/or offset is too big.

[asyvan]

Originally Posted by dkreidel

Oh, I dream of 1 meter of snow! We had more than 1 meter in one day of October of this year, and last year the valleys of our local mountains received just over 21 meters of snow; more on top. It's usually late July before it's all melted. I am near Glacier National Park.

Sorry for being so OT here, but the world we all live in is quite beautiful.

[Lotus99]

Originally Posted by plainmaster

Isn’t that the exact OPPOSITE of what is true? The lower you go (less offset) the more brake caliper clearance you should have.

Look at the picture above of negative offset. The spokes are FURTHER away from the hub, not closer, as in positive offset.

You're confusing the description of positive and negative offset with the actual offset numbers.

My stock X3 front wheel is 8.5 x 21, ET30. Getting a lower offset wheel, like 8.5 x 21, ET 25, will push the wheel OUT 5 mm. 25 is lower than 30.

Which is exactly what Asyvan's picture shows. Smaller offset pushes the wheel farther out:

[beyondedges]

Originally Posted by asyvan

Here is a picture I made to show just that.
Imagine these three rims/wheels being same width, same design and three different offsets.

would wheels with the following specs work on 2019 x3m, is the offset too low? thanks

19x8.5j 25 offset