UKKid35

Here are some photos here that show the poor condition of the flywheel on my car









However it is likely to be much worse now because those were taken five years and 40,000 miles ago.

I am intending to get the flywheel skimmed, and could do with advice from anyone who has had this done before. In particular I'm interested in how much can be taken off, and balancing.

I realise a new flywheel would be preferable, but my budget doesn't stretch to an additional $600.

RyanPerrella

Hi Paul

you take it to a place that resurfaces brake rotors.

Its pretty standard stuff, although the cracks on your flywheel are really bad. Someone isnt too great with clutch modulation ...... I would strongly recommend replacing THAT flywheel. Buy another used one and resurface it, but that one you have pictured is terrible.

The factory spec is in the WSM, measure it and take it in, if the guy wants to cut it then great, if not then you will need a new or another used flywheel.

UKKid35

When I first posted these pics five years ago I was told I was insane to continue using it. However it's worth bearing in mind that those photos are extreme close up and are probably displaying at more than 5x actual size, so the cracks may not have been quite that bad - at the time.

As far as I can tell used manual flywheels don't really exist, so new is the only other option. But I really don't buy new, with the exception of service parts, almost every replaced part on my car has been replaced with used.

I have found a local machine shop that quoted me for brake rotors previously, so I'll take it there armed with the WSM spec.

123quattro

I had my Audi flywheel resurfaced, but only because I put in a new clutch disk. That thing looks terrible. I would really go looking for another flywheel. If it comes apart you could very easily loose a foot.

UKKid35

No doubt catastrophic flywheel failure can happen, but is there a known case of it happening to a stock standard road car, rather than in a drag racing scenario?

SharkSkin

Paul, not every shop that has brake equipment has a flywheel grinder, and yes, even though the WSM mentions use of a lathe it really should be ground, not just turned in a lathe. WSM calls for thickness from the mounting face against the flywheel to the friction surface of 27.5mm, max runout 0.05mm, "Surface finish/waviness" 0.008mm. 928I shows a used FW on their site for $300 if you need it.

I would not be especially concerned about the surface cracks that will probably clean up, but it looks like at least one crack is much deeper, and has split toward the inside beyond the friction surface. That implies that it is more than just a surface crack.

BTW, flywheels that break after passing a visual inspection are more common in high-horsepower high-RPM applications. The cracks you show would definitely give me pause -- i don't think I would re-use the flywheel. A flywheel coming apart at 6K RPM can take your foot or feet off regardless of how much HP you have. Try Googling "flywheel scatter" for plenty of info on the subject. Also, please post updated pics when you get it apart.

A properly ground flywheel will look something like the pic below. Note that the machine marks are not concentric.

123quattro

I've seen it happen on heavy trucks. Don't specifically know of any stock cars that have come apart.

LT Texan

Paul,

Mark at 928 Int'l shipped me a used one - reground and ready to go. it was a good price too.

And that after my machine shop ruined my original.

Landseer

Ditto, don't reuuse, in my opinion. That must have gotten hot.

I have deglazed them by hand, should you find a used glazed one and not want to pay a machine shop, with a wetstone + 400 paper wrapped around a flat bar, lubing with oil and WD 40 to carry away the bits.

dr bob

The process you are looking for is called blanchard grinding here in the US. As Dave A's example shows, the surface is ground flat while the flywheel is slowly rotated across the grinding wheel surface. This tuype of grinding is essential to maintain the surface perfectly flat, which is in turn essential for perfect clutch operation. The service is not at all expensive, and can usually be carried out by any competent automotive machine shop service.

Be warned that a brake disk lathe is not a suitable tool for this job unless the flywheel is smooth and has never been overheated. The overheating shows up as those little dark blue sections, results in tiny surface cracks, and the uneven hardening of the metal surface means that a lathe tool will chatter away and destroy the surface finish. This same warning applies to brake rotors by the way-- The ones you heat-treat doing track or other severe duty are quite likely to have hard spots that a normal brake lathe won't be able to clean up. Drilled, grooved, relieved, and cast-hole rotors generally need to be ground rather than turned no matter what.

RyanPerrella

Blanchard grinding..... sounds good, is this actually what the blue collar guy at the machine shop calls it? Or is there another term used in the industry, ive seen some machinists that may have steam coming out of their head if you say "blanchard grinding" But maybe thats just a sign that thats not the ideal place to take your stuff to

That method of resurfacing sounds allot better to me then having it done on a lathe

for small blue marks, i actually got some out of a pressure plate by using a 3m Roloc disk on a die grinder, it took out the blueing very easily, i was actually surprised, in all it took all of 2 minutes to do that to a PP, i imagine the same would happen on a flywheel, but cracks like those...... not a chance.

If 928 intl supplied a used flywheel that was already resurfaced, that sounds like the best bet to me, no need to take it to a machine shop once you get it either, just open the box, and plop it on.

UKKid35

A good deal for someone, but not for me once you add shipping, customs and VAT. I could ask my gf to bring it back to London for me next month, but luggage allowances make that an unreasonable request.

Rob Edwards

I had my flywheel done at a shop that Mark Anderson recommended in Lake Forest, CA for $50, 1 day turnaround. It had the same concentric machining marks that Dave showed. Paul, there's gotta be a machine shop locally that's do it for the same ballpark cost.

RyanPerrella

Dave,

why does that flywheel have that ring around it? I know thats an area that not in contact with the clutch surface, still i wonder why its there?

123quattro

Yes, this is what everyone calls it.