Most factory or OE flywheels are made from cast iron (a.k.a. gray iron) to keep costs down. Cast iron is a very heavy and porous material and can be brittle when subjected to high stress loads. Steel is an alloy of iron where carbon has been added to increase strength and make the material more resistant to cracking.
(For more information on materials, please refer to the “Flywheel materials” section of our TECHNOLOGY pages…)
WHAT FLYWHEEL IS BEST; STEEL OR ALUMINUM?
The choice between steel and aluminum performance flywheels is mainly a function of the vehicle’s planned uses and driver preferences. Either type of flywheel is a viable choice and improvement over cast OE units depending on what you are looking for in strength and performance, what type of vehicle you have and how you will be using it… Steel flywheels are designed to be stronger than OE ones and will deliver approximately the same weight (or in some cases more) than OE cast iron or nodular flywheels. This means they will deliver about the same inertia at rpm and driving characteristics as the OE unit, but will be less likely to break or explode under high rpm, high load conditions as seen in drag racing, etc. Steel flywheels are often SFI approved for race use. Steel flywheels are also a good choice for helping move heavy vehicles at lower rpms, such as in heavier trucks and for rock crawling, hill climb, etc. These flywheels are designed for use where extreme strength is the issue and not increased performance. Other considerations with steel flywheels are that they still require resurfacing when changing clutches and therefore have a limited service life, requiring eventual replacement, and that they do nothing to improve heat dissipation from performance clutches and therefore can not significantly improve clutch performance or longevity. Another drawback is that the ring gear teeth are often cut right into the steel flywheel, meaning any damage to even a few teeth from a starter mishap, etc. will often mean replacing the entire flywheel.
Billet aluminum flywheels are also designed to be much stronger than OE cast iron flywheels, but their lower weight will provide significant performance benefits by delivering faster throttle response, quicker acceleration, smoother shifting, easier vehicle braking and by freeing up additional horsepower to the wheels (by reducing parasitic driveline loses). Billet aluminum flywheels can also deliver OE equivalent inertia, but at increased rpms, and will require a slightly modified driving style. Billet aluminum flywheel equipped vehicles will provide a more responsive and “nimble” driving experience over vehicles equipped with heavy iron or steel flywheels. All Fidanza Performance aluminum flywheels are made from high quality 6061 T6 billet aluminum to deliver the optimum in strength and durability and are often SFI approved for race use just like steel flywheels. Our billet aluminum flywheels are a great choice for street performance vehicles, as well as, ones used in road racing, autocross, time attack, drift and drag racing; anyplace where increased horsepower and throttle response is desired. In addition, aluminum flywheels are much better at dissipating heat from your clutch, which can greatly improve clutch performance and life; and all Fidanza Performance aluminum flywheels feature a replaceable hardened steel clutch friction surface, which means they are infinitely re-buildable and will deliver years and years of exciting drivability.
Separating Fact From Fiction!
So, what IS the best flywheel to use; steel, lightened chromoly or lightweight billet aluminum? Can you use a performance lightweight aluminum flywheel on a daily driven car? How about for drag racing? Can a factory dual-mass flywheel be replaced by a one-piece aftermarket flywheel? What are the trade-offs? These are just a few questions we hear every day at Fidanza Performance.
Unfortunately, there is a lot of misinformation out there about flywheels. We’ve all seen the conflicting posts on the multitude of forums about whether to use a steel or aluminum flywheel. Most often the posts are not really based on facts, just opinions or what other people have heard. Often, the majority of commenters have never even tried or used both types of flywheels to really know what the differences, benefits and trade-offs are, they’re just repeating an opinion they’ve heard from someone else (who often doesn’t have first hand experience either). It’s kinda like asking 10 people what to take for your headache… One will tell you asprin is always best, while another swears by ibuprofen and yet another says acetaminophen or naproxen or maybe just a cold washcloth. Which one really works? They probably all do, but to differing standards depending on your needs or likes and how they effect you personally. So before you make up your mind on what is the best “medicine” for your performance car, be sure to check multiple sources and find knowledgeable people that have actually USED the various products; if not, you’ll only get a partially informed opinion.
“You can’t run an aluminum flywheel for drag racing, you need a steel flywheel for drag racing, it has more inertia.”
This is one we see all the time. Truth of the matter is, there are drivers who run; and swear by, aluminum flywheels in their drag cars. Including some multi-year national champions. They love the extra horsepower they get from using a lighter aluminum flywheel, as well as, the fact the flywheel friction surface can be easily changed, allowing them to put a new clutch in ad get right back out on track if needed. Many also say the lighter flywheel doesn’t shock the tires as hard at launch and allows for better traction. He bottom line is that inertia is a math equation; mass X rpm = inertia. If you have a lighter mass, you just need to add some rpm to get the same inertia; it’s all in how you drive the car.
“Aluminum flywheels are just for racing, not for the street.”
That is another comment we hear all too often. Who says and for what vehicle or what type of driving? There are tens, if not hundreds of thousands of cars on the road today with aluminum flywheels, and they work great! If you are changing from a heavy iron or steel flywheel to a lightweight aluminum flywheel the car WILL drive differently, but most people get used to the differences and adapt quickly, some people say they don’t notice anything other than the faster acceleration, quicker throttle response and an overall lighter, nimbler feel to the car.
“An aluminum flywheel is noisier than a stock or steel flywheel.”
“A lightweight flywheel will be louder than a stock/replacement dual-mass flywheel.”
We’ve heard this a few times too. While this can be true in some instances it is not a significant difference in sound over stock flywheels in most cases; and if the flywheel is going on a performance car with say a high performance exhaust system and aftermarket intake system, the sound difference might not even be noticed. Keep in mind that the whole reason for heavier stock flywheels, and especially dual-mass flywheels is to help dampen noise and vibration in a car’s driveline. When you go to a lighter flywheel, some noise and vibration may return, but if the flywheel and clutch assembly is balanced correctly as a unit, it is usually minimal. In any case, the performance gains in liberated horsepower, faster acceleration and quicker throttle response are often considered more than adequate trade-offs for any minimal increase in sound or vibration.
Looking for more outside input on these subjects? Then check out some of these links to see what others are saying, or check out our Customer Testimonials under the COMPANY tab here on our website: