davidfarmer

I found I rarely had "measurable wear", but the discs were cheap and I'd replace them anytime they were out of the car. I did have a partial failure once...but not sure if the clutch went first, or the pilot bearing/torque tube cause a huge vibration that caused the clutch to whip out of alignment.

They are more durable than you might think.

sperkins

brkntrxn

Mark,

Can you quantify that ".75 sec" for me? Are you saying that you did back to back testing, with identical weather, identical weight except for the difference in the clutch, and identical tire grip? And your laps are consistent enough down to the 100th of a second that you could measure a .75sec difference?

I am not calling you out on this, I am just wondering if the clutch is truly worth 3/4 of a second. My laps times are usually fairly consistent, but I know that weather, grip and driving mentality can make 3/4 of a second difference as well.

The article that David sent me a long time ago quantified the standing acceleration times and differences in a straight light, so I know there are gains. I just question how much on a road course can be quantified unless the testing is accomplished with similar variables.

(sorry, my process improvement analytical nature coming out)


-Kevin

drivinhard

too much to type, we'll talk at CMP

brkntrxn

See you Sunday.


-Kevin

Kubs

Anyone know what is needed to install the 5.5" clutch in a C4 with a ZF? Will their hydraulic slave cylinder work with the ZF or no?

Z06Tracker

Mark, he is wanting you to tell him there were many other variables at play so he can convince himself not to spend the money on this!

drivinhard

there are always many variables at play, I highly recommend the stock clutch for all C5 TTA and PTA participants

Z06Tracker

Now Kevin, thank us for all the money we just saved you.

drivinhard

Kevin, we never talked at CMP. Not enough hrs in the day.

Feb CMP this past year was very very similar weather. same temps, same air (sunny, high pressure, fairly dry). car at the same comp weight (actually slightly heavier this past weekend, 25-30 lbs or so)

we'll throw out all the bits that throw in more variables and lets just look at the portions of the track that you are WOT, since any gains are only going to be seen there anyway. only drivetrain difference from Feb to Nov is the clutch. (51 lb, 12" dia stock clutch, vs 5.5" dia, 8.9 lb button clutch Nov, along with a 12" ~5 lb flex plate/starter ring)

Nov lap was 1:41.2, Feb lap was 1:41.3 (lateral G's were down in Nov, as were the cornering sector times). both events used no lift shifting on the WOT portions.

Front straight from a dig in 2nd gear

3 tenths quicker from exit of 14 to the start finish. 3 mph faster at the line)

Back side between 7&8

2 tenths quicker

Back side 8 - kink

1 tenth

3rd gear squirt between 11 and 12

2 tenths

That’s 8 tenths on a track where you are WOT only 20% of the lap

No, not the same day/same car, but conditions very similar, so I don't think those numbers would stray very much.

Be more than happy to send you the TM files

sperkins

No fair.

9707vette

what is the life of the 5.5 vs 8.25 vs stock clutch. I can run a full race season without having to do any major mechanicals. For me thats 7 race weekends ( open track friday, practice/qualify/race Sat and Sun). In addition to the race weekends, we also run 15-18 test/practice days. Do these clutches last as long, 1/2 as long, or????

davidfarmer

clutches never wear out unless you slip them. I see no reason a 5.5" clutch would not last as long as an 8.25 unless you slide it a lot in the paddock or driving it onto a trailer. Once you are on the track, the clutch should slip very little.

Time to invest in a winch and an ATV to pull you around the paddock...... (I'm kidding, I always drove mine everywhere, including into the trailer)

RAFTRACER

I have been using the QuarterMaster 7.25 OptimumV triple and it has proven to be quite durable......

I like David am bad and drive my car into trailers too...

drivinhard

you can install a cable catch in the ground and a hook on the car, like a carrier and an F14 tomcat, and just drive the car in the trailer @ 100 mph and not slip the clutch

Jason

Don't forget to set the parking brake on your truck.

RAFTRACER

And to raise the front ride hieght on the car significantly before doing so......

davidfarmer

actually, I (an many of you too) are pretty good at getting a rolling start and just gliding up. You can be gentle on the clutch if you are willing to put in the effort.

And for what it's worth, pretty much anybody that wants to be competitive in NASA TT or open wheel really has no choice but to eventually convert to a small clutch. You can count points all you want to, but the lightweight clutch/flywheel is the Elephant in the room!

Timz06

That is a trick setup. I think I am going to get one of these. Just hate doing drivetrain work!

drivinhard

aside from the obvious inertia advantage, you'll never get a C5 to 50/50 without one (unless you run the car heavy and throw a ton of weight in the rear)