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what vintage CLA is that? older Merceddes wheels used m12 lug nuts, newer ones are m14, and you defintely can NOT mix those up, I don't know offhand what the split year is.
thats not the right size tire for an E, you want 245/40R18 XL (or on a 17" wheel, 245/45R17 XL). The XL (Extra Load) is important, these are heavy cars, like nearly 1000 lbs heavier than my early 90s Mercedes
the other critical number is, all mercedes wheels have a 66.56mm center hole, this is important to verify for non-mercedes wheels, and Mercedes has used spherical head lug screws since at least the mid 80s, probably before.
Older MB wheels not only used 12mm bolts, but they also had 12 mm seat radius.
E class starting with W211 switched to 14 mm thread and 14 mm radius.
If you want to put older wheels on newer car, you need to order custom bolts, who would have 14 mm thread and 12 mm radius.
There was a company specializing in this.
The holes circled in blue are not cosmetic. This is unique for MB cooling system.
Check who made the wheels?
I and some other members had similar looking Czech -made AMG wheels on our W212. They turned to have weak alloy and were cracking/bending under the car weight.
This is where mine ended.
Older MB wheels not only used 12mm bolts, but they also had 12 mm seat radius.
E class starting with W211 switched to 14 mm thread and 14 mm radius.
If you want to put older wheels on newer car, you need to order custom bolts, who would have 14 mm thread and 12 mm radius.
There was a company specializing in this.
The holes circled in blue are not cosmetic. This is unique for MB cooling system.
Check who made the wheels?
I and some other members had similar looking Czech -made AMG wheels on our W212. They turned to have weak alloy and were cracking/bending under the car weight.
This is where mine ended.
Older MB wheels not only used 12mm bolts, but they also had 12 mm seat radius.
E class starting with W211 switched to 14 mm thread and 14 mm radius.
If you want to put older wheels on newer car, you need to order custom bolts, who would have 14 mm thread and 12 mm radius.
There was a company specializing in this.
...
would those 14mm bolts even fit through the 12mm hole on the wheels ? I've seen the opposite, bolts with 14mm heads and 12mm threads.
The holes circled in blue are not cosmetic. This is unique for MB cooling system.
Check who made the wheels?
Dear kajtek1,
I have a hard time taking those holes as part of a passive cooling design.
I am all ears to learn from anyone, but the fundamental of increasing surface area for cooling purposes requires a higher heat transfer coefficient than it could be found on those cylindrical holes. Though I have not seen the wheels myself, you have, those holes must be capped on the other side by the hub once installed, correct? Therefore, no airflow through them (unlike ventilated perforated disks). I would love to see the engineering drawings, and heat transfer calculations used for the design.
I would accept they needed the holes for some structural stress relief of some kind.
Since the quality of the wheels is suspect, it would not surprise me the engineering as well so I would take the "passive cooling" with a grain of salt.
For obvious reasons I can't find a picture of inner side of the wheel, but instead of making silly forum reply, you could take a look at your wheel.
OE MB wheels have molded slots, allowing the air to be sucked between hub and the rim, where at the end is the hole.
Centrifugal force push the air via holes making air flow between hub and the wheel.
Lot of aftermarket wheels don't have the slots, even sometimes they have the holes.
I don't think it is crucial feature as not too many cars have it, but than MB is not average design.
For obvious reasons I can't find a picture of inner side of the wheel, but instead of making silly forum reply, you could take a look at your wheel.
OE MB wheels have molded slots, allowing the air to be sucked between hub and the rim, where at the end is the hole.
Centrifugal force push the air via holes making air flow between hub and the wheel.
Lot of aftermarket wheels don't have the slots, even sometimes they have the holes.
I don't think it is crucial feature as not too many cars have it, but than MB is not average design.
Do you mean the above?
I thought I wanted to see the engineering calculations before, now I will probably have to model it using a CAD/FEA/CFD program to convince myself the additional manufacturing is worth some improved cooling. Live and learn as usual.
It must be within the error of the data used for the modeling.
That's it.
In my google search I found that Mercedes expanded the cooling slots to their F1 wheels, what is stirring pretty good rumors between competition.
Perhaps is worth clearing out that the centrifugal forces due to the wheel spinning can only push air from the inner radius toward the outer radius; therefore, the air can only flow in one direction unless there is enough high pressure on the outer radius than the inner radius.
There is a big difference between the airflow in open-wheel (like F1), and closed wheel (like streetcars) designs. For the F1 design the airflow is ducted, i.e. forced and driven by the car motion; therefore, the flow is forced through the hub into the spinning center of the wheel. The article using the same picture you showed also shows a diffusion ring at the center so, the ducted air can go through the hub and connect to the wheel and then spun out due to rotation.
On closed wheel design w/o ducted brake cooling (passive cooling only), I cannot foresee enough low pressure on the inner side of the wheel compared to the tangential flow around the car to force flow into the wheel, perhaps the other way around. Flow usually takes the path of lower resistance; therefore, it will go through the wheel larger opening before channeling against the centrifugal forces at the center of the wheel.
Still think that for streetcar applications w/o ducted brakes those holes are still cosmetic; or with minimal contribution to the cooling of the wheel or hub.
09-20-2021, 10:31 PM
.. Definitely not for cooling , but neither are they cosmetic 
