Stock Pressure Plate Bolt Thread

[BlackbeardBen]

Hi there,

I'm a long-time lurker; I love the forums here. The community is great, and I thought I'd finally jump in. I have had my 2004 Vibe GT for a little over a year, and a good 18,000 miles (170,000 miles on the OD).

Anyway, the clutch was (typically) never very solid when I got the car - and after I let my brother drive it home one day he smoked it - so now I'm getting it replaced with the OE replacement Exedy clutch. Also, because I'm having an independent mechanic do it in a situation where he doesn't have any extra time to get the flywheel machined, I decided to get a new flywheel - and upgrade while I'm at it. I got one of the F1 Racing chromoly flywheels based on the good reviews I've seen for it - and yes, it is CNC machined very nicely with the exception of a couple of burrs that weren't cleaned up.

There is one thing I've read about the F1 Racing flywheels, though - that the pressure plate tapped holes aren't always the same thread as stock. I checked the holes on the F1 chromoly flywheel - they're M8-1.25. Can anyone tell me if that's what the stock bolts are on the 2zz? I suspect they may be M8-1.0 threads, but I have no way of finding out without either ordering replacements that might not work and I probably wouldn't need otherwise, or waiting until the clutch is out (which I can't do given my time constraints). The stock part no. should be 90119-08079 from Toyota.

Thanks - and glad to be here!
Ben

[BlackbeardBen]

I think I've found my answer - the stock bolts are in fact M8-1.25 x 14mm long and have lock washers:
http://www.toyota-4runner.org/3rd-gen-t ... wap-3.html" onclick="window.open(this.href);return false;

The F1 Racing chromoly flywheel threads plus the Exedy OE replacement pressure plate are approximately 15mm thick (can't remember off the top of my head the more precise measurements of each), so the stock bolts should work without any problems.

[star_deceiver]

What's the weight diffrence between the flywheels?

[BlackbeardBen]

What's the weight diffrence between the flywheels?

The F1 Racing chromoly flywheel is 10.67 lb according to my postal scale; Gripforce claims 10.6 lb.

If only I had a way to measure moment of inertia... I'd expect a slight advantage for chromoly flywheels relative to their weight versus aluminum flywheels, because the ring gear on aluminum flywheels has to be steel - adding weight where it hurts most disproportionately compared to the overall weight.

The Exedy OE replacement pressure plate weighs 7.59 lb.
The Exedy OE replacement clutch disc weighs 2.37 lb.
The Exedy OE replacement release bearing (in its plastic bag packaging) weighs 0.54 lb.

I don't know the precise weight of the stock flywheel. Gripforce claims 19 lb - but I have not seen any confirmed measurements, and that seems pretty high. I have seen conflicting measured weights of 16 lb and 13 lb from a Corolla XRS. I will post the weight of my old one when the swap is done on Saturday.

P.S. I'm not really a weight weenie; I just like accurate data.

[BlackbeardBen]

The new clutch and flywheel are in; they drive great! The Exedy OE clutch grabs very well, though pedal feel is quite light. The lighter flywheel revs up and down noticeably faster, but it's not a huge difference. The car does feel lighter overall though, which is nice. My old clutch was so bad that I got used to it not grabbing, so I stalled the new one a dozen times the first day. Since then I've gotten used to it and don't have any problems - the lighter flywheel is fine and doesn't make it any harder to pull from a stop.

So, here's some measurements:

The previous flywheel weighs 13.27 lb.
The previous pressure plate weighs 8.68 lb.
The previous clutch disc (heavily worn) weighs 1.69 lb.
The previous release bearing weighs 0.54 lb.

So I dropped about 3.7 lb between the flywheel and the cluch, a reduction to 83% of the stock weight of the two together.

The clutch and flywheel definitely had been replaced before - the old flywheel was marked 88,000 on it, presumably the mileage of the car it came out of. Everything was quite worn and the flywheel and pressure plate were lightly discolored - but the most shocking thing was that the clutch disc had chunks missing out of it! About 1/3 of one of the faces was missing all of the organic material in chunks down to the metal, and both sides were worn all the way to the rivets. I don't think I could have gone any longer without changing it...

Here's a pic of the devastation - just about the only thing worse is an exploded disc!