Skimming the flywheel

[Garfieldus]

Monty, my 1997 24v manual is in for a new clutch at the moment . I decided to fit a Toyota Optifit.

I suspected the flywheel would need skimming as it was juddering at times. Just got a call from the mechanic. There are discoloured hot spots on the flywheel but his engineering shop is suggesting that skimming it will make it worse.

I called another very experienced engineer whose shop does this all the time and he says that he has never heard that skimming would cause problems.

Do you have any advice for me?

 

[Towpack]

I've had flywheels skimmed in the past and had no issues. Don't know how much a new OE flywheel is but, personally, a skim would be my first option. To reiterate the opinion of the second engineer I just can't see how a skim would make things worse unless the flywheel is so deeply scored that a skim would reduce it's thickness beyond tolerance but with a few "discoloured hotspots" it doesn't sound like yours is anywhere near that bad. JMO

 

[Chris]

I agree, but it all depends on how well it's skimmed of course. If there is any run out on it when mounted, letting the clutch up could be interesting. I'd want a second opinion before I had it skimmed. Someone like your chap, but who'd actually seen it.

Was the Optifit expensive?

 

[Dave_S]

What mileage has your motor covered? I'm having a similar juddering issue, having just had a new clutch kit fitted (and not had the FW changed or skimmed)... Mine's covered 180,000....

 

[Garfieldus]

Thanks for all the advice, much appreciated. I'm bringing it to my engineer in the morning and I will go with his advice.

Don't know how much a new OE flywheel is

€393.00 + VAT (full retail)

Was the Optifit expensive?

€245.00 including VAT (trade price)

What mileage has your motor covered?

158,000 miles

 

[frank rabbets]

I've encountered this problem. Sometimes if you skim the flywheel you find hard spots in the surface and the lathe cutter does not go through cleanly to give a flat surface. I sent one off to the grinders instead and they did a perfect job.

 

[chapel gate]

can someone educate me on this flywheel grinding, I understand fly wheel lightening for performance gains. ive got 237000 miles on the original clutch and the last couple of years I get a bit of judder which seems to go after driving a bit.

 

[Garfieldus]

I've encountered this problem. Sometimes if you skim the flywheel you find hard spots in the surface and the lathe cutter does not go through cleanly to give a flat surface. I sent one off to the grinders instead and they did a perfect job.

I left mine with my engineering shop this morning and will collect on Monday. He said he didn't foresee any problems skimming it.

Interesting point about grinding instead of cutting. I'll mention it to him.

 

[Chris]

Surface grinding and turning are different processes
Surface grinding over a larger surface is a more accurate process
Well hmm it gives a more precise finish on things
But done well in a lathe you should still get a good finish
I put cruiser brakes on my lathe

 

[Towpack]

can someone educate me on this flywheel grinding, I understand fly wheel lightening for performance gains. ive got 237000 miles on the original clutch and the last couple of years I get a bit of judder which seems to go after driving a bit.

Skimming or refacing of the flywheel is done just to get rid of any grooves or wear marks so the new clutch friction plate has 2 nice smooth surfaces to mate with but is not always necessary. It's much the same as skimming brake discs to remove grooves or excessive corrosion. Clutch judder can be caused by a number of things, just one of which is a worn or scored flywheel.

 

[chapel gate]

thanks towpack, so if it looks ok, it is ok?

 

[frank rabbets]

Mine's always juddered for the first few gear changes and I've had it almost from new so nothing to worry about. Worse after it's been standing for a few days.

 

[Chris]

Have to say my new clutch is superb. for a big heavy truck, setting off, even uphill is like driving a small family car. No revving or slipping or anything. You just lift your foot and away it goes. I know I shouldn't sound surprised, but it really is very smooth indeed. The flywheel didn't look bad, but there were certainly some score marks on it. The old clutch was actually polishing the rivets. I don't know how it hadn't actually let go completely. I don't think that concentric rings on the surface would really be a major problem. It's uneven surfaces (lumps and bumps) that would give juddering I'd have though. Brake discs can be deeply scored and still fine, it's when there is run out that you start to get problems. If there are hard spots on the face then I'd suspect the other material may be wearing down around it and that would be noticeable.

 

[Garfieldus]

Mine's always juddered for the first few gear changes and I've had it almost from new so nothing to worry about. Worse after it's been standing for a few days.

I have mine just over a year now, and when I drove it before buying, the judder was there but disappeared after a few miles. After buying, I thought I had driven the judder out of it, but after parking it up for a week it was back as bad as ever just like yours Frank. The pedal was a bit heavy and the bite point was too high but I never thought it slipped. It'll be interesting to see how it is when its all back together.

 

[frank rabbets]

I recently tried to skim a large flywheel in my lathe for a friend. He had a new clutch and had terrible judder. You could see high polished spots on the flywheel. I did as good a job as possible but various cutters would not level out these high spots completely and as the flywheel was very thin from a competition car I did not want to take a big bight off it. He fitted it back and it was better but not satisfactory so we found a grinder shop and they managed to level the surface by taking off about 3/1000 th of and inch. Perfect result.

 

[Garfieldus]

All back together and on the road again. Lovely light clutch, good bite point, better gear changes and no judder. Much nicer vehicle to drive.

Hopefully the chance I took in getting the flywheel skimmed rather than replacing with a new one will result in the judder staying away.