rjmalm

What is your tracking or aggressive driving experience with OEM tires (Mich PSS)?

I got alot more rollover on edges on the fronts than expected. Lost about 3/32" on the outer edge of the fronts in about 50 miles.

It was recommended that I try higher cold tire pressures on the OEM tires
and start at 40-41psi cold vs the standard 36psi So that is what I used and by 4pm they were at 50psi. The 4 stints started at 10am 85 deg air time and ended at 4pm at 97deg. 25 total laps. Each lap contained 4 straights with speeds om 90-125mph down to about 40-50mph entry speed, (no fade all day) and the corners after the straights were full U turns. 16 turns total at the track. I did not push hard, since it was a new track for me HPDE (and there was no passing except straights). I only was doing about .8g Max in the corners as you can see in the video. I was trying to learn the line vs max speed and still could feel the rollover and that limited my feeling that I could go faster. Of course, Sport+ and TVD=track. Arizona Motorsport Park. You can hear the slight tire slide in the corners (please ignore the damn noise from the blue painters tape that I put on my mirrors for flying gravel protection, next time I will use some collision impact film that other guys were using.)

https://www.dropbox.com/s/84zd676ubb...ht%20.mov?dl=0

Any comments would be helpful.

JCtx

I have no comments on tracking, since I only have 400 miles on my car. But just by looking at it, it's obvious it needs a much more aggressive alignment for the track, especially with its whale-like 4K+ lb weight. And your tire wear results confirmed that. My car actually looks like it has positive camber in the front at some angles, so definitely very mild negative camber. And same for the rear. Doubt it's even -1º. You don't want a track alignment on a touring car, but something more in the middle. The car has a stiff ride and excellent brakes for a touring car, so alignment needs to be more in line with the rest of the package IMO. That way the tires will wear a bit better than yours. With a mild alignment and a heavy car, you can eat a set of tires in short order with some aggressive driving.

But while others with track experience respond, how about telling us how the car felt at that pace (8/10s or so). And did you drive it in auto only, auto using the paddles sometimes, or manual mode? And how about nannies off, expert mode, or just plain sport+? Thx.

rjmalm

I think the full power made my instructor nervous about stopping. He did not really like a novice going full out on the straights at 1st. I have done DE before and taken Boundaurant classes but he never asked before hand. We both commented on how quick the braking was. I did take Rage2 hints about watching out of oversteer with heavy trail braking and it never was an issue at my 80%.... I did only drive in auto since I was focused on the learning the track line and in 25 laps you dont have alot of seat time. I did some prep doing some calculation of corner and straight speeds (knowing lengths and radius from google earth).

Bye the way, someone did post the attached settings in another post FYI.
I lost the link and description.

JCtx

Thanks man. Interesting the front middle spec is only -0.75 (way too little); but -1.2 is the minimum acceptable to me. I'd say -1.5 in front and -1.8 at the rear would be perfect for some aggressive driving. Any more would be nicer for the track, but not so good for the street. The trick is to find your own balance. I don't drive much in the twisties here in the desert southwest, but like to do so aggressively, hence the figures I stated. More aggressive alignment would eat my tires on the inside, before eating them on the outside, like you did. Wonder at how many miles that first alignment chart was measured; it's red all over the damn place. Lexus doesn't include a free alignment check, right? Car transport almost always throws it out of whack. Might be a good idea to pay for a check, before eating $2K in tires, no? Watching tire wear is another way to first check we need a realignment. It'd be good to start a new thread to see how many folks have checked their alingment, and how many are having uneven tire wear issues, and whether they're tracking their cars or not.

rjmalm

Thanks for you opinion on setting values.

I see a date on the 2 alignment images (red and green) of 7/22/2015 which is when I downloaded them. I found the author Carnevino and short thread https://www.clublexus.com/forums/rc-...questions.html
Maybe Carnevino will see this an comment about his wear pattern and driving style/history.

Before tracking at 9100 miles I was getting even wear and the measurements across each tire is attached. I would say it was light aggressive street driving and a few hundred miles of mild aggressive twisty roads on long road trips.

So I guess one should get "track aligned" just before tracking and then realign for the street. I only do this a few times a year.

Guess I better have the alignment checked after I get the new fronts
this week.

rage2

I don't think camber is adjustable on the RC-F (at least I couldn't find it when I did my alignment), which is a bummer because it really needs more negative camber for proper hard cornering. You'll need camber plates to adjust it. That might explain the fronts rolling over so much even at 50psi hot, but I'm surprised at how much it rolled over for the pace you were going at. The good thing is your rears look great! Those alignment settings you posted are for a lowered car I think.

Great tire data, you should get a tire pyrometer, much quicker readings at the track to see how the tire is behaving for quick adjustments.

One question I have, can you post the RC-F's G meter circle reading? Flip to the screen and press OK and it loads the historical peak data. I'm curious how it looks compared to your in car G-meter in the video.

JCtx

Hey, that was awesome information. That's pretty much the way I'll drive my car (before your track day), and can actually step up the aggression in the twisties a bit to even out inner and outer wear. Otherwise your wear pattern shows almost perfect wear until the track day. The front needs more camber for track duty, and if it can't be adjusted beyond -1.2, you'd need camber plates... or pretty much eat a set of tires per session, especially if driven to its limits. The rears could be okay at -2.0 at the limits, but need data like yours to know for sure. I honestly would have bought a different car if I wanted to track it. And now that we know front camber can't be adjusted for that without aftermarket changes, it's even more true now. Would have bought the much lighter Cayman GTS or GT4 instead. But the reason I went with the RC-F was precisely because I wasn't going to track it. But it's really fun to do that every once in a while indeed. Keep us posted on how you attack that alignment issue, and thank you again for such comprehensive data.

It HAS to be adjustable man. And the proof is on the corrected values shown above after alignment. I guess what you meant is it's not adjustable beyond certain parameters (looks like about -1.2 in front, and about -2.0 in rear), which is almost always the case with stock suspensions.

rage2

If you know how to adjust front camber please share. I haven't been able to do it, and searching the forums no evidence that it can be done without aftermarket parts.

edit - This guy says the same thing here.

The posted settings are off by .1 before and after, probably just a measurement issue more than anything.

rjmalm

[QUOTE=rage2;9216025
One question I have, can you post the RC-F's G meter circle reading? Flip to the screen and press OK and it loads the historical peak data. I'm curious how it looks compared to your in car G-meter in the video.[/QUOTE]

I dont know when at the track I did a G meter reset but this is what
there is now on the display. I have pulled more lateral Gs off the track but not alot more (maybe 10% or so). Some time I will have to do a more exact compare with HLT values in a parking lot in a circle.

ExSrAaron

Not sure who was telling you to run cold pressures at 40+psi, that is NOT a good starting point IMO. You should be shooting for 40psi hot or less depending on the vehicle and specific tire. The higher temperature will improve wear I believe, but not ideal. The novice instructors (including classroom teachers) always seem to recommend "follow whatever OEM pressure is" instead of providing helpful information. A pyrometer is the best way to test and evaluate tire pressures by reading temperatures across the tire. Camber will improve wear across the tire, but you will need to experiment to find what works best on the RCF. Keep in mind the RCF suspension has more dynamic camber gain than most strut-based systems. Static camber will change through compression and rotation. The PSS is a capable tire, but once your pace improves they'll start overheating (greasy) and chunking.

I'm taking my IS350 to Mid-Ohio this weekend (first event with adjustable front camber) so it should be interesting to see how these cars perform with more camber. I went from a -0.5deg to -1.7deg. and reduced toe to 0 upfront. Initial impressions are very good so far, all-but eliminated understeer (main issue with this 3rd gen. IS350). So if you're still struggling with understeer on track I'd suggest using some offset A-arm bushing or call FIG up and get custom adjustable arms.

Lastly, I suggest you always use manual mode with Sport+ settings. The automatic is not intelligent enough to pick the right gear (always one gear to high) and you'll be using precious corner exit speed. You'll also have better control of the chassis through throttle modulation.

I didn't read every post carefully, but are you running track brake pads or OEM pads?

rjmalm

Thanks for the comments....

rage2

The RC-F on oem tires and suspension likes high front tire pressures. I run 37psi cold up front to prevent rolling onto the sidewall in semi aggressive street driving. The rears need much lower pressures.

JCtx

Are you saying the RC-F has no camber adjustment, or no camber adjustment BEYOND stock parameters? I could bet my house the former is not true, but you probably meant the latter, correct? I'll get under my car tomorrow to see if I can adjust the stupid parking brake myself (goes all the way to the carpet without holding the car much), and will look for camber and toe adjustments for myself. They're usually adjustable thru an eccentric nut/washer with limited adjustment (same for the toe). Once you get to the maximum length of the 'oval', that's it; you're maxed out. But you should always be able to reach the maximum tolerance spec. In the RC-Fs case, the spec seems to be -0.75 -0.45, for a total of -1.20 max, but I only extrapolated that from a chart posted previously. It'd be nice ot have ALL suspension specs with 'x' value plus +/- 'y' tolerance.

May I ask you at what Gs your front tires started squealing? And what tire pressures you were running? Thx.

Very good point. Forgot to comment about that. Usually you run LOWER cold pressures at the track, not higher. 40 should be the highest HOT pressure indeed, not 50. But I have NO previous experience driving a 4K-lb whale aggressively, so optimal tire pressures might be different. Will continue to read other more experienced owners for the best cold tire pressures for aggressive driving. Another thing I forgot to mention is for some strange reason, Lexus recommends only DOT3 brake fluid, even though the car has a very aggressive Brembo braking system. That's not good for track duty either. As a final comment, my tires started squealing at 0.9G today, with hot tire temps of 38 all around (ambient was about 68ºF, and equivalent cold tire pressure of 35, since I set them at 36 but it was 78º in my garage). So backed down to 0.8G the rest of the run, and car was cornering superbly. Doesn't sound like much, but was actually cornering faster than on my sport/touring bike (2015 Kawasaki Concours 14) dragging the pegs. Not bad for a 4K+ pig. But came to the conclusion with stock alignment (mine is probably less than -1.2 at the front other owner posted, as they look like they actually have positive camber. He he), 4K+ wieght, and not doing this too often (live in the flat desert, after all), better leave the alignment alone, and don't push the car beyond 0.8Gs. Maybe in summer I could do 0.9 or even 1G initially. But as you mentioned, tires would start to get greasy right away, so not a good idea. The good news is this car has superb feedback, and I could feel exactly what it was doing, and playing with the throttle to maximize grip and corner speed. It was awesome. I have plenty of track experience in other cars, but this is the easiest to drive fast AND the most fun (auto, that is) at the same time so far. So quite happy with it. The GTR without disabling TC (voids warranty) and AWD it wasn't fun at all for me (it requires the least skill to drive fast though). The Corvette was fun too, but MUCH more nervous at the limit, and you have to be 100% focused, or could lose the rear if you don't catch it fast enough. Or just drive it with all the nannies, but that's boring too. On the RC-F, it's relaxing to drive fast. And even with its 'limited' cornering ability, was going 65 on a 30 zone, so fast enough already. And enjoyed the scenery much more than on any other car. The only thing I didn't like was my driving position put the left A pillar in the worst possible position for left handers, not allowing me to see thru the curve far ahead, so had to move my torso forward. Since this car does not have a ratcheting driver seatbelt, like Corvettes and others (I like to cinch it when driving aggressively myself), it wasn't a problem, but definitely not ideal. Finally, steering isn't communicative enough, as expected for an electric rack. But I could feel what the car was doing, which is rare, so not a big issue for me. Okay, enough. Looking forward to get more experience driving this thing in the twisties. Have a good one.

rjmalm

I have most of my 25 laps on video and went back too look at the best few with overlap of Harry's laptimer. Tthe video sound shows tire squealing range around .8G. I did have a few .9 but average was .8. One time I got squeal at .6 but maybe HLT sample rate was not fast enough catch the actual G since it was the quick right left from turn 2 to 3. Yes 40psi cool was too high but my instructor did not have me reduce it and it was my 1st track in years and 1st in the RC-F.

Track maps are attached with my prep calculations of driving line and corner/straight speeds. Green line annotation on the corners shows the changes in line at the track based on the experience and instructors suggestions. the video
link (reference lap) shows the following.
T1 .7g 45mph is what I predicted I could do and did but straight into it was slower at 64.. Slight Squeal
T2 .8g after 56mph straight, 48mph n corner, a little higher than corner prediction given the measured radius but less than the max I saw others doing on YouTube. Slight Squeal
T3 .7g 46mph Slightly more Squeal
T4 .3g 50mph
T5,6,7 .6-.8G Straight 121mph down to 63 at turn in and higher at apex for 5 and 6 and 49mpnh for turn 7 which is lower than predicted.
T8 .8G U turn 35mph Squeal
T9 nop
T10 .8g 90mph Slight Squeal
T11 .6G 66mph very Slight Squeal
T12-T16 Traffic but slight squeal on these.

Same link as at start of thread:
https://www.dropbox.com/s/84zd676ubb...ht%20.mov?dl=0

ExSrAaron

ELP_JC,

You make some good points there! I'm surprised Lexus recommends DOT3 for the RCF, but it is compatible with DOT4 so I would still recommend using a higher-threshold fluid unless Lexus for some reason says not to do that (doubtful). The weight is really the dealer of this car, if they can pull a Land Rover or Audi and drop 700lbs that would be ideal, heck even 300lbs would be great. My experience is limited to the 3600-3700lb 3IS IS350 RWD though.

40psi +-5psi is about right from my research and experience too. Basically as low as you can go before you start to roll over on the sidewall. I don't think PSS sidewalls are quite as stiff as other tires like the DZ-II or RS3 so you may need a few extra pounds of pressure. You really have to experiment while you're at the track though.

Also, I wouldn't worry about carrying "X" amount of lateral acceleration through corners, but it can give you an idea of how your corner speeds may compare to other vehicles. With my IS, similar tires, and less camber I peak at 1.2G with consistent 1.0G figures now (squealing all the way around the track). I would recommend dissecting a corner to figure out where in the turn your car starts to squeal, corner entry, apex, or corner exit. Making a few assumptions here, but if it's consistently "corner entry" than you probably have bad understeer and you'll have to adjust your line/speed to compensate (late entry and/or slow down).

Hopefully some other owners will chime in with their experiences too