Strange behavior at the track

[kyrix1st]

I had some strange behavior at the track where car suddenly judders and loses rear grip.

I'm guessing this is related to malfunctioning abs pump (I have the christmas tree on) and traction control that is supposed to be off somehow kicking in but not sure.. can anyone chime in?

It starts at around 4:44.

Also happens around 2:50, 3:40~3:50.

[Ximian]

I didn't watch the whole video but just the spin when entering the track is odd enough that you should have tried to figure out what's going on right away. The track is wet, but doesn't have standing water. Unless your tires are in terrible condition, that shouldn't be an issue at these low speeds. What's the condition of your tires and what are they?

If you have the tire pressure light on and along with some other things, DSC kicking in could be partially responsible for this. Is that the case? Have you tried doing a reset of the TPMS? When switching from 19" street wheels (with TPMS) to my 18" track wheels (without TPMS), I have to reset the sensors or DSC will kick in at very low speeds and the slightest of turns.

[kyrix1st]

Originally Posted by Ximian

I didn't watch the whole video but just the spin when entering the track is odd enough that you should have tried to figure out what's going on right away. The track is wet, but doesn't have standing water. Unless your tires are in terrible condition, that shouldn't be an issue at these low speeds. What's the condition of your tires and what are they?

If you have the tire pressure light on and along with some other things, DSC kicking in could be partially responsible for this. Is that the case? Have you tried doing a reset of the TPMS? When switching from 19" street wheels (with TPMS) to my 18" track wheels (without TPMS), I have to reset the sensors or DSC will kick in at very low speeds and the slightest of turns.

Track was wet and icy (freezing temp) and I was on R compounds so entry spin was understandable. (I had DSC off) But now that you mention it, I also had that juddering sound on entry.

What I find strange is that although I've had ABS issues for a while which is supposed to disable traction control completely, it somehow seems to be kicking in randomly.
I don't think we have TPMS in Japan.

Maybe I'm just ignorant to drive in this condition.

[FuzzyPeaches]

My initial thought watching this is that you're getting no where near enough speed to get any heat in the tires and with traction control turned off on a wet track, its going to be pretty easy to break the tires loose.

What tires are you running and what is their condition?

Edit: You responded as I was typing. R-Comps need heat to get any decent traction. It doesn't look like you were going to get anywhere near fast enough on this track for that. Wet and icy on R-Comps... its going to kick loose at random times.

[bigjae1976]

Originally Posted by FuzzyPeaches

My initial thought watching this is that you're getting no where near enough speed to get any heat in the tires and with traction control turned off on a wet track, its going to be pretty easy to break the tires loose.

What tires are you running and what is their condition?

Agreed. Don't know of any R-Comps that like low temps.

[kyrix1st]

Originally Posted by FuzzyPeaches

My initial thought watching this is that you're getting no where near enough speed to get any heat in the tires and with traction control turned off on a wet track, its going to be pretty easy to break the tires loose.

What tires are you running and what is their condition?

F: RE71R (265/35/18) 29 psi cold
R: RS4 (265/40/18) 29 psi cold

Ventus RS4 was initially on front but swapped to rear after one track day at Suzuka. This is the first track day for RE71R (1000km~ mileage.) Both have quite a bit of tread left.

[FuzzyPeaches]

Originally Posted by kyrix1st

F: RE71R (265/35/18) 29 psi cold
R: RS4 (265/40/18) 29 psi cold

Ventus RS4 was initially on front but swapped to rear after one track day at Suzuka. This is the first track day for RE71R (1000km~ mileage.) Both have quite a bit of tread left.

Ok... Not really what I would call R-compound tires, but what I said earlier still holds true. Granted, my track/race knowledge is e30 based, but I believe those pressures are way too low to start out on a freezing track where your speeds are barely getting you to 3rd gear. Someone with more e9x track work will hopefully give you a good base for that.

[kyrix1st]

Originally Posted by FuzzyPeaches

Ok... Not really what I would call R-compound tires, but what I said earlier still holds true. Granted, my track/race knowledge is e30 based, but I believe those pressures are way too low to start out on a freezing track where your speeds are barely getting you to 3rd gear. Someone with more e9x track work will hopefully give you a good base for that.

We call them high grip compounds here, thought R compound was closest in meaning Is A052 considered R comp?

[FuzzyPeaches]

Originally Posted by kyrix1st

We call them high grip compounds here, thought R compound was closest in meaning Is A052 considered R comp?

Its the same as the other two. Those all have treadwear ratings of 200 (not sure how these work outside of the US). R-comps will have a TW rating of roughly 40.

[Ximian]

Originally Posted by kyrix1st

Track was wet and icy (freezing temp) and I was on R compounds so entry spin was understandable. (I had DSC off) But now that you mention it, I also had that juddering sound on entry.

...

Maybe I'm just ignorant to drive in this condition.

That's not going to work well as you found out and there's really not much to learn with that tire combo and icy conditions. Put on regular street tires and enjoy a day easily drifting around the corners without destroying your tires.

[bigjae1976]

You'd be surprised how bad cold tires feel. I just got to experience cold and heat cycled tires for the first time last month...almost spun in the pit lane.

[kyrix1st]

Originally Posted by Ximian

That's not going to work well as you found out and there's really not much to learn with that tire combo and icy conditions. Put on regular street tires and enjoy a day easily drifting around the corners without destroying your tires.

Funny thing is the full course was divided into drift and grip (i.e. D or G course), but everybody ran on grip course that day so it was much safer to drift on grip course

Originally Posted by bigjae1976

You'd be surprised how bad cold tires feel. I just got to experience cold and heat cycled tires for the first time last month...almost spun in the pit lane.

Which tires were you on? I kind of knew RS4s would crap out at this temperature range because I could casually drift with my 140ps Z3 track car

[bigjae1976]

[QUOTE=kyrix1st;24171373]

Originally Posted by Ximian

Which tires were you on? I kind of knew RS4s would crap out at this temperature range because I could casually drift with my 140ps Z3 track car

Hankook C51s. If the RS4s are like the RS3s then they will perform like shiet under 40 degrees.

[gmx]

Juddering under braking is CBC kicking in, imo. Not sure if that is normal with everything turned OFF (completely off).

[Estoril Blue]

RE71Rs shouldn't be run below 40F.

Mismatched front and rears? That isn't doing you any favors.

[roastbeef]

i have 295 rear tires with solid sub/diff bushings. on wet pavement with mdm on, the amount of tires slip it allows sort of makes this shuttering like the tires are hopping. i think it just might be a trait of tires on wet pavement with traction control.

[bigjae1976]

Originally Posted by Estoril Blue

Mismatched front and rears? That isn't doing you any favors.

That can be tricky. I do know NT01s on the front and Toyo RR's in the back are a workable combo.

[Richbot]

It’s called wheel hop. Normal but not desirable obviously

Also, the rS4 and re71r light off very differently in the cold and damp. Re71r comes in much faster than most other tires. That tire combo in those conditions qualifies as a USDA Choice Grade A Bad Decision imo

[Rassilon]

Were you hitting the gas pedal when it happened? My car does that all the time going from a standing start in rain or even 40% throttle 2nd gear in freezing temp. The solid subframe mount helped a lot but doesn't completely eliminate it. However, I have never got any hopping from the rear during deceleration or corning. The rear typically slides out progressively rather than suddenly transitions from gripping to hopping.

[Candide13]

Well the sounds at 5:27-5:35 certainly indicate a drivetrain malfunction of some kind; otherwise hard to hear over the bouncy music

With slippery conditions like this I would recommend to aim for a lot smoother steering input, but the malfunction does not seem to be related to your turns.

Cool (and safe) that you had the whole track to yourself...

[kyrix1st]

Originally Posted by edwardgtxy

Were you hitting the gas pedal when it happened? My car does that all the time going from a standing start in rain or even 40% throttle 2nd gear in freezing temp. The solid subframe mount helped a lot but doesn't completely eliminate it. However, I have never got any hopping from the rear during deceleration or corning. The rear typically slides out progressively rather than suddenly transitions from gripping to hopping.

Nope I wasn't.

Interesting should you ask, because on dry, I usually try to follow "brake to the limit, then fully release to distribute grip to all four wheels when steering into a corner" which typically isn't preferrable with under-steery setup on braking as you get relatively more understeer without trail braking. (as weight transfers from front back to rear, getting back to the "understeery" nature.)

Video below provides a good explanation by Taniguchi,from 10:00 to 11:00. You can see that the car that is oversteery in nature gets too sideways if you trail brake into a corner. Conclusion in the video is in order to go fast, it's important to make the car more turnable in nature (primarily with aftermarket LSD) rather than resorting to typical braking techniques for understeering vehicles, which most passenger vehicles are. Then again, it's all preference.

Originally Posted by Richbot

It’s called wheel hop. Normal but not desirable obviously

Also, the rS4 and re71r light off very differently in the cold and damp. Re71r comes in much faster than most other tires. That tire combo in those conditions qualifies as a USDA Choice Grade A Bad Decision imo

It is bad lol. I prefer this setup on dry because 1. RS4 definitely holds out longer on the rear than 71Rs being a harder compound 2. it is damn scary to lose front grip. Didn't expect a wheel hop though!