It's a controversial topic. Here's our thoughts.
Every single OEM that makes a dual mass flywheel says it should not be resurfaced and that it needs to be replaced when the time has come.
We can't recommend that you don't follow an OEM recommendation. It's one of those things that someone a hell of a lot smarter than all of us over here has determined not to be the best idea.
With that said, it's been done, and it will continue to be done. But with risks involved.
A solid mass is a flywheel cut or cast from a solid piece of metal and machined to tight tolerances. Most are steel. But if it's made of aluminum, it will most likely have a removable friction surface made from a more durable alloy than the aluminum it resides in. Either way, everything is toleranced and balanced and can accept a machine job that easily keeps it within a specification range that meets the requirements when it needs to be refreshed.
A dual mass flywheel is a significantly more complex version than a single mass. It has parts inside of it that absorb NVH. The problems associated with machining a dual mass flywheel include:
- Improper balance - Because there are technically multiple flywheels on a dual mass, you could cause an imbalance by only machining one of the flywheels which could cause some vibration and harshness during use.
- It might require special fixtures to hold it down during resurfacing when compared to a standard solid mass unit.
- Metal shards and dust from machining have the ability to get inside the internal section of the flywheel, contaminating it with foreign material.
At the end of the day, many people have resurfaced them successfully and don't report issues. If you want to get by without spending as much money, at this risk of possible early failure or unwanted issues, we've seen much riskier decisions than this. Another issue is finding a place to resurface it. There seems to be the shops that don't mind sending it out and trust their work but many shops won't do the job. If you have it done, you might want to call around to find a place that has experience doing them.
However, the right way to do it, technically, is to replace it.