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I am going to need a clutch soon, and was gonna order parts. Because its so cheap through the mazdaspeed motorsports discount, I was considering just replacing the flywheel rather than resurfacring the old one (it'll be about the same cost to me, and will minimize the downtime for the car if I can have all the parts ready). Is the flywheel balanced to the engine, or is it neutral balance? I've read on some hot rod forums about balancing a flywheel TO an engine, but wasn't sure if this was just something for older cars or what.

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2012 MX-5 Sport SUV

I'm sure others may disagree, but why do either unless the flywheel is damaged? I've installed four clucthes this way with no problems.

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Vincent Keene
'06 Ford Mustang GT (track rat)
'15 Dodge Charger R/T (yeah, it's got a HEMI!)
'07 Ford Fusion SE (205,000 miles and counting)
'98 Chevy Z-24 (retired)
'93 Acura Integra (Team SWB 24HOL Car)

I agree, unless you take the PP and clutch off and the FW is blued and/or a dial indicator shows it's out of tolerance, I'd just keep the old one on there without resurfacing or replacement. Though, I'd probably take it off and replace the rear main seal while you are in there.

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2011/2012 Autox VP
2013/2014.5 President
2013 Top Gun

2015 Fit

22R-EC => 4G63 => D16Y7 + D16Y8 => EJ255 + K24Z2 => K20Z3 + K24Z2 => K24Z2 + M54 => L15B

As other have said, I would likely just take drill with a buffing pad on it just to clean up the surface. I had a '95 Mazda Protege with 205k on it when I changed the clutch on it and never considered changing the flywheel. Unless clutch disc has gotten so worn that it's really scored the flywheel, just a clean up of the surface is all I would do.

I owe this knowledge to Scott Johnson, who helped me through my first clutch change on my Miata about 10 years ago. - AB

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'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

That is exactly what I did.

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Vincent Keene
'06 Ford Mustang GT (track rat)
'15 Dodge Charger R/T (yeah, it's got a HEMI!)
'07 Ford Fusion SE (205,000 miles and counting)
'98 Chevy Z-24 (retired)
'93 Acura Integra (Team SWB 24HOL Car)

Just a data point for y'all - I just changed the clutch on the WRX. The clutch had been slipping for the PO for a long time and the surface was pretty blued. I decided to be cheap and lazy and didn't address it. Now there's a little bit of vibration during launch, not buttery smooth. I'm fine with it, doesn't bother me much.

Just to point out that worst-case (this was) is still OK for a tolerant driver. I agree with the other guys, don't bother.

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Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

Brice,

It's literally been decades since I built up an engine, but it depends on whether the engine is fully internally balanced or has some external balancing as to how you balance the flywheel/pressure plate. I recall some big block Chevy engines and some Ford V8s I think had some external balance on the flywheel, but the machine shop (if they know their stuff) is on top of that (was on top of that...this is 30 years ago). In other words, I think on those they balance the flywheel to the external balance (i.e. out of balance) specification...something like that.

Anyway, most likely the engine isn't externally balanced on the flywheel (but check), so you can have the flywheel and pressure plate each zero balanced. You should be able to find this out pretty readily on the net I would think. I had mine done together back then, but if you change out the pp later on, you lose that matched set. Of course, the next part is finding a local and competent enough shop to do the work.

I would imagine modern mass production tolerances are such that there is usually not much to be gained, but in the old days, it was super-sweet-smooth (plus I was building a 7+k rpm engine at the time which normally redlined at 6k, so it needed all the help it could get).

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

How cheap is the new flywheel?

IIRC, you can get a flywheel resurfaced for about $40.

But as others have mentioned, I wouldn't replace it unless it was damaged.

What he said

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2005 Mazda RX8 STX 11

NCR Solo Chair & Cape Fear Chapter Coordinator
http://www.ncrscca.com

Along similar lines, but maybe different outcome -

I've done clutches in a Miata, Subaru, and CRX. The CRX and Subaru flywheels were resurfaced at CarQuest, but the Miata was a new MazdaSpeed Motorsports replacement. Both the CRX and Subaru had a small amount of "vibration" or chatter at launch, and I was anal about proper installs, but the Miata was butter. For the same price, I would absolutely opt for a new flywheel. But as others have noted, I would probably think twice about doing anything more than a scuff unless there was significant scoring in the flywheel.

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Dustin Fredrickson
-- I'm a nobody --