Как колеса помогают снизить неподрессоренную массу

Когда дело доходит до модификации и тюнинга послепродажного обслуживания, большинство энтузиастов сходятся во мнении, что уменьшение веса автомобиля — это хорошо. Когда вес двигателя меньше для толкания или тяги, его мощность используется более эффективно, что улучшает общую производительность. Это также означает более короткий тормозной путь, лучшее ощущение руля, лучшую общую управляемость и большую экономию топлива.

Здесь в игру вступают два типа потери веса:подрессоренная масса и неподрессоренная масса. Думайте обо всем, начиная от амортизаторов (по направлению к центру автомобиля), как о подрессоренной массе:крышке багажника, сиденьях, вашем собственном человеке и даже маленьком освежителе воздуха, свисающем с рычага указателя поворота. Неподрессоренная масса — это все, что находится снаружи подвески, более или менее:тормозные диски, тормозные суппорты, колеса, шины и многое другое.

Когда дело доходит до снижения неподрессоренной массы, самый простой способ сделать это — установить легкие колеса послепродажного обслуживания. Они отвечают нескольким требованиям:украшают вашу поездку, придают ей фирменный вид и повышают производительность.

Кажется, у каждого в голове свое соотношение относительно того, насколько неподрессоренная масса равняется уменьшению подрессоренной массы. Форумы битком набиты разными формулами. Например, некоторые люди считают, что потеря одного фунта неподрессоренной массы подобна потере 10 фунтов подрессоренной массы. Однако это не обязательно так, поскольку в игру вступает гораздо больше факторов. Однако преимущества снижения неподрессоренной массы обычно более очевидны, чем уменьшение подрессоренной массы.

Есть несколько вещей, которые следует учитывать и учитывать, если вы ищете комплект легких колес для повышения производительности вашего автомобиля, экономии топлива и долговечности. Действительно ли все дополнительные преимущества связаны с установкой более легких колес или есть другие аспекты? Является ли определенное легкое колесо и соответствующая шина лучшим выбором для вашего стиля вождения и места, где вы это делаете? Давайте разбираться.

Не все легкие колеса одинаковы

Не погружаясь слишком глубоко в металлургию, общее практическое правило заключается в том, что легкие колеса послепродажного обслуживания слабее, чем заводские колеса OEM. OEM-варианты имеют металл, на который не обращают особого внимания для снижения веса, а производственные процессы для создания более легких колес также более дороги. Автопроизводители могут работать более рентабельно, улучшая экономию топлива и эффективность ускорения/торможения в других областях. Все колеса имеют определенные сертификаты, и в игру вступает старая поговорка «цена, качество и вес, выберите два». Легкое и качественное колесо будет стоить дорого, а тяжелое колесо, изготовленное по более низкой цене OEM, будет недорогим.

Различные типы колес также производятся по-разному. Существует три процесса создания облегченных колес:литье, литье и ковка. Литье – самое дешевое и распространенное. The process is to essentially pour hot liquid metal in a cast, let it cool, and the basis for a wheel is created. Flow-forming involves initially casting the wheel, but then reheating it back up and pulling out the barrel into the right size before its cooled back down. Forging is heating up and shaping a chunk of aluminum into a round block and then machining it into its final form. Flow-forming is generally more expensive than casting, and forging is the most expensive of the three.

All have their own benefits, but it's generally considered that flow-formed wheels are the best value, as they're not as expensive to produce as forged wheels and they’re lighter than cast wheels, though are still quite strong and can stand up to potholes, curbs on track, and other hard hits.

Where Are They Rolling?

This leads us to a major consideration:What sort of driving will you be doing with your lightweight wheels? If they're bolted up full-time, know that they might not stand up to hazards as well as factory cast wheels. Personally, I've been lucky in my experiences rocking lightweight wheels all-year-round, on and off the track, but my experience is from having tires mounted up with at least a 50-series sidewall and about as much of a width as I can get away with on my old Mazda 2, thus giving the wheels plenty of sidewall to protect them.

I plan to swap lightweight wheels onto my current 2011 BMW 128i sometime in order to save around eight pounds per corner, or 32 pounds overall. Though, I'd be scared to mount up a tire that's near the minimum sidewall and width that the wheels can accommodate. Like I did with my Mazda 2, my BMW's lightweight wheels might be its primary set — why not reap performance benefits and better fuel economy in as many scenarios as I can and look good while doing it? Because of this, more rubber that's not stretched on there is a good thing.

Are You Really Saving Weight?

When enthusiasts swap to lightweight wheels to achieve better grip and overall performance, usually stickier tires are on the docket as well. Почему бы и нет? Plus, the wheels are often wider than factory wheels, thus more of a contact patch with the road can be achieved. But will the weight difference really be there. Matching performance tires often weigh more due to having stiffer sidewalls and coming upsized over the factory size.

The best apples-to-apples comparison I can come up with is discussing my current setup and planning and how much weight I want to shed. Right now, my factory 17X7 BMW Style 256 wheels weigh just about 22.3 pounds each, coming out to 89.2 pounds total. The wheels I intend to swap for track use, D-Force LTW5s in 17X8, weigh 15.5 pounds each (62 pounds total), netting a 6.8-unsprung-pound loss at each corner, and 27.2 pounds total.

The tires that the previous owner upgraded to are 225/45/17 Yokohama Advan Apex V601s, which weigh 22.4 pounds each and have a treadwear rating of 280.

My Bimmer's current wheel and tire package comes to a grand total of 44.7 pounds per corner, and 178.4 pounds total. If I keep the same tires (though they won't be long for this world if I keep tracking on them), or replace them with a fresh set of the same brand/model/size, I'd truly experience a 27.2-pound weight loss.

If I decide to upgrade to stickier, 200-treadwear Falken Azenis RT660s in the same size with the D-Forces, the weight jumps up to 24.5 pounds per tire (40 pounds per wheel and tire). This doesn't sound like much, but it takes away from that 27.2-pound weight loss, netting just an 18.8-pound loss instead. That's still a hearty amount of shedding for unsprung weight. But imagine what even wider wheels and wider tires would mean?

Still, it wouldn't be for nothing. Despite not having much of a weight loss, any drop in unsprung weight is still better than a net weight gain, such as adding non-lightweight wheels and tires to your rig. Plus, the added benefits of more grip are quite apparent, as more grip means higher cornering speeds, more stability at speed, and shorter braking distances.

It should also be said that stickier tires will reduce fuel economy, as they have a tad more rolling resistance over conventional everyday street tires.

Fitment is Key

Another consideration is that the fitment of the aftermarket wheels must be taken into consideration. This is where following guides and reading Facebook groups and forums comes in handy. What sizes are popular for your particular car, especially among enthusiasts who use their cars the same way? Because I'm after more on-track grip and performance on a daily driver, it's in my best interest to see what setups fellow enthusiasts have successfully used.

In my case, there are some great guides out there for the E82 BMW 1 Series, including some by Bimmerworld and Apex Race Parts. Fitment Industries has some fields that can be customized to offer wheel and tire choices that will fit your particular setup and how much modification of the car's body you're up for doing.

How will changing the wheel's diameter, width, and offset affect how they fit in the wheel well and over the brake? In the E82 128's case, you can't fit as big of a wheel and tire package as other rear-wheel drive sports cars without adding more negative camber and modifying the fenders. It seems like a setup with a 17X8.5 wheel, 40 offset, and 245/40/17 tires is the limit without doing some fender rolling, but not without adding negative camber. This is related to the alignment and involves tilting the top of the tire more inward. Depending on suspension valving, doing some fender rolling might be required.

Personally, I'll probably go 225s or 235s, even with some added negative camber, so as to give myself more wiggle room against rubbing the tires on the inner fenders, contacting the shocks, and other issues.

Final Considerations

There's more to all of this, but hopefully it's acted as some good pre-emptive food for thought, and at least put you in the mindset of figuring out what kind of net gains there are to experience. Plus, there's the financial aspect:What is your budget for wheels and tires, and what wheel and tire combo best fits it? Is it worth upgrading to x for y less pounds, at z more of a cost?

Hell, if you're after more grip on track for cheaper, why not keep the tough (albeit heavy) factory wheels, and mount up slightly narrower yet much stickier tires? There could be a net weight loss, and the more track-centric rubber will bode better for grip, as well as hold up to the higher heat and G forces.

There's also the aspect of the wheel and tire size altering the drivetrain's gearing, in which case I'd say refer to what fellow enthusiasts who've run bigger wheels and tires have experienced. When I ran 15X7.5 wheels with 205/50/15 tires on my Mazda 2, which originally came with 15X6 wheels and 185/55/15 tires (puny, right?), the speedometer read a little higher than the stock factory size.

Regardless of all of the above, it's fun researching all of this in the name of gaining more performance, potentially more fuel economy, and doing something that's a bit different than the way our vehicles were set up as everybody-friendly near-appliances.