MrAWD

Right! Grip would, again theoretically, not depend of the surface area, so higher coefficient of friction would always produce more forces required to break it, assuming the same weight. Once the tire is abused, other things here come to play as its deflection, temperature, and so forth that would play its role in where the final number is.

Dallas J

iTrader: (1)

Well I would put money on a 285 rivals or RE71 over 225 A7 on an Evo on asphalt. Concrete opens gap between streets and r-comes, just look at nats pax vs tour/pro's.

white_turbo

iTrader: (2)

Well, my 2017 debut in a "National" event was a fail. I thought the car was nice and healthy with rebuilt transmission/xfer case and new clutch done at end of 2015 (minimal events in 2016 and no hard launches since) would survive the NJ ProSolo. Not a single run was made by me and the car broke down on my co-driver's third run. =(

Now back to fixing the car.....based on a fellow autoxer opinion, the front diff is probably shot (which in hindsight should have been swapped out also at the time).

Dallas J

iTrader: (1)

Stock front diff is pretty weak, would not take that to a pro outside of a stock clutch. Wavetrac makes a perfectly suitable OEM style replacement but I'm far happier after swapping to the 1way clutch front.

white_turbo

iTrader: (2)

Well, my clutch is stock-ish. I replaced it with the Exedy Stage 1 thinking that I could protect the drivetrain more with it. Which diff did you use?

I have talked to Aaron about it, he seems happy with Quaife. And I just talked to Jon @ TRE and he recommends the Wavetrac. Obviously, I have no experience on either nor the 1 way clutch that you are referring to.

Did you see a huge improvement in the way the car pulls out of a corner?

Dallas J

iTrader: (1)

I have the Mfactory clutch diff which I swapped out from a Wavetrac. The torsen diff in AutoX at heavy steering angles and off throttle induces push. The engine braking torque is enough to try and bind the tires. The 1way clutch diff just acts open off throttle and when trying to change line mid corner you really get the car to tuck in on lift instead of push wide.

And its not a marginal difference. It was one of the most eye opening changes from something that doesn't seem that important. Its enough that I would probably run an open front diff rather than a torsen after feeling the change.

white_turbo

iTrader: (2)

Thanks. So I take it as that the helical diffs act more like a 1.5 (or even 2 way) diff, but you are much happier with a 1 way diff for the front and the clutch type diff is the only way to do that. ​​​​I guess this makes sense to me.

Obviously, the clutch type requires more maintenance and offer adjustability also, just not sure if I will even be able to take advantage of that.
​​​​

Dallas J

iTrader: (1)

Exactly. It might require more maintenance but you can also upgrade the plates to longer lasting parts. My car isnt a street car so its not an issue for me. But make no mistake, it is definitely the way to go.

kikiturbo

Dallas, how much preload do you run in that front diff..

I am asking as I have managed to get my hands on a ralliart front plate diff that can be configured as a 1 way or 1.5 way diff with 3 different preloads.. Since it came in a heavy preloaded version, I am thinking of getting the weakest preload spring washers first..

Dallas J

iTrader: (1)

I would start on the soft side of things and move up. Itll be easy to feel if you have inside front wheel spin but that can at least be managed with rolling into throttle gentler. Its hard to do anything about too much preload with driving.

I have my plates stacked to only give 60% of max lockup. Currently dont feel any need to go up or down, but if I did pull it to change I would probably try down and see if one-wheel spin becomes a thing. I dont know for sure if its the right mentality on it, but its where I'd start.

kikiturbo

ok, sounds about right..

we will first baseline the suspension geometry and damper changes with the original helix diff and then switch the transfer box to the one with raliiart diff... to see what difference it brings.. I'll get the softest preload cone springs... darn things are stupidly expensive..

griceiv

iTrader: (2)

20-30 ft-lb is a good target for front preload.

kikiturbo

my diff came with 180 lbft preload... can get it down to 88 lbft.. (sticking to official spec.. playing with non standard preload washers will give different range of course..)

Dallas J

iTrader: (1)

If theirs an even stack of washers, like say 8 or 12 of them, can you take out half? Or interval of 3 take out 1/3rd. Also, is the preload you're specing the break away torque or the spring load? Measuring break away torque usually requires a special tool (I think Mfactory sells a tool for it)

griceiv

iTrader: (2)

I suspect we're not talking the same units of measure, but if it really is 180 ft-lbs of preload that is way too much for a front diff.