F4R Flywheel Machining/Skim

[aldo_87]

I'm in the process of reshelling a 172 and have come to the point of fitting a new clutch kit. The original flywheel mating face is in poor condition, fairly pitted etc.

I've had a search on here regarding this but can't find anything concrete. Can they be machined, do they have sufficient material to take a skim off them? And if so, does anyone know how much material roughly?

 

[NorthloopCup]

It’s not advisable to skim the f4r flywheel, but people have done it. Would I personally? No.

 

[aldo_87]

Any specific reason? I'm not content to run the flywheel in its current state and I'd rather not fork out £300 on a replacement (unless absolutely necessary).

I suppose I'm asking is it worth a £30 gamble to machine it?

 

[Mr Underhill]

Any specific reason? I'm not content to run the flywheel in its current state and I'd rather not fork out £300 on a replacement (unless absolutely necessary).

I suppose I'm asking is it worth a £30 gamble to machine it?

I assume it’s £30 to machine it? What’s the cost of a good gearbox and new clutch these days, £700? Offset that against the cost of a new lightweight flywheel at say £300. That’s your gamble fella.

 

[aldo_87]

Would having a fraction of material removed from the face of the flywheel put the box at risk?

 

[Mr Underhill]

Would having a fraction of material removed from the face of the flywheel put the box at risk?

Well I’d no more get my brake discs skimmed, let alone a flywheel. Up to you at the end of the day but for the sake of £300 I personally wouldn’t risk it.

 

[plees]

Got a spare flywheel here if any use. Can check condition for you later on?

 

[PhillipM]

Would having a fraction of material removed from the face of the flywheel put the box at risk?

Not really, most production car stuff has allowance for about a mm of wear anyway - it's often why they have the step on the face to start with, so you have a reference to measure from.
No real issue with resurfacing the vast majority of flywheels, I've done dozens over the years.
Might have to remachine the step if it's a lot but for most things a cleanup is going to be a few tenths of a mm anyway.

 

[aldo_87]

Not really, most production car stuff has allowance for about a mm of wear anyway - it's often why they have the step on the face to start with, so you have a reference to measure from.
No real issue with resurfacing the vast majority of flywheels, I've done dozens over the years.
Might have to remachine the step if it's a lot but for most things a cleanup is going to be a few tenths of a mm anyway.

I have a similar take on it. It's a component that has a wear allowance, provided I don't go beyond the tolerances, I can't see an issue. It's machined or ground during manufacturing anyway.

Unless there is a specific reason not to do it, or that it can't be done because of the geometry etc.

Got a spare flywheel here if any use. Can check condition for you later on?

That would be ideal. Thanks

 

[Brigsy]

Cant imagine a slight reface is going to hurt anything assuming its not been done before. Ive not done a 172 flywheel, but have had other renault flywheels ground no issues.

 

[TheCAB]

Refacing a flywheel for the first time to remove minor wear where you are removing a few thou of material would be extremely highly unlikely to cause any failure due to it adversely affecting the structural integrity of the flywheel. Can't see it causing a problem really.

Off on a tangent. I have had many a flywheel for numerous engine builds lightened and balanced over the years (in my day specialist manufactured lightened flywheels didn't really exist) and never had one come to grief. Your engine builder / machining man though needs to have the "knowledge" as having too much material removed or indeed having the work carried out on an unknowingly "cracked flywheel" can have it exiting sideways out of the bellhousing in bits, which I have known to happen, particularly when people have been a bit "too greedy" in the lightening department.

As an aside I had the flywheel in my sons sprint/ hillclimb Clio 172 machined and lightened way back in 2012 and we have never had any issues with it. I am not advocating this as the "way to go" for anyone as again you need some in depth knowledge of the subject matter before having the work carried out but it's possible.

However for our current new F4R build I have bought a TTV lightened flywheel though as thought I would treat us to one as it's nice and shiny.

 

[Brigsy]

Ive had a few lightened oem r5gtt flywheels too, and had no breakages. All pre the days of billet flywheels been easily available.

One in particular was scalloped on the rear and slotted between clutch plate mounting points from 7kg down to 3.6kg, i believe it was as light as the machinist dared to go. I used to launch the carcon 22" x 8 drag radials at santa pod with around 230hp/220ft/lb torque and use 7500 rpm. Never failed, 4paddle clutch worn it out.

These days id just buy a ttv as easily available.

 

[PhillipM]

Yea I do my own usually so rather cheaper.

This was the state of my daily flywheel I took of the Pug last time I had the box off:

So I bead blasted it but you can still see the uneven area's from the carbide hot spots:

....

And then I decided to skim it slightly and got a little carried away:

Just slightly.