Hi Everyone,

I'm coming from a '16 Subaru Legacy here, so still adjusting to the RC's brakes - currently i have just over 1000 miles on the 350 F Sport.

My Legacy's brakes feel very linear, whereas the RC feels like it can "lock" sometimes if you're braking slightly harder than usual - i.e. exiting off of a ramp on the freeway...

So the potential problem goes like this... when I was in sport in the passing lane today heading home from work, I had to brake suddenly as the cars in front of me did so. Felt my car "lock" or "stall" - RPM stayed at around just under 3000 and wouldn't budge for about 2 seconds as the engine sort of just stalled...I've been googling and found potential culprits from Torque Converter, idle control valve, catalyst failure, to a bunch of other things.

Does anybody feel that the RC's brakes are less linear than other cars? I'm assuming what happened today isn't normal so i plan on giving my dealership a call tomorrow morning...but wanted some opinions from other RC owners...thoughts?

 

I'm a little confused about the scenario you are describing. I haven't experience anything quite like that.
There are some things that come to mind though. One I experience, and one is a feature I'm aware of, but haven't experienced.

Brake Assist: This is a feature on many new cars, and all Lexus. If the car thinks you are attempting emergency braking it will assist by adding additional braking force for you. I have not experienced this, but it might feel non linear.

Downshifting for engine braking: I do experience this in certain scenarios. I notice it most when I'm heading downhill. If I pump the brakes heading downhill, it seem like sometimes it decides to downshift to create some engine braking. This can go on for a while, at least a few seconds, until conditions change. Maybe the road flattened out and it upshifted again, or more brake is applied slowing the car down enough that the engine braking wasn't causing the rev's anymore.

I don't know if either or both of these make sense for what you experienced. They are just what came to mind for me.

 

If you were in sport, sounds like the car downshifted and kept the revs high so you could change lanes and blaze around the person in front of you. Hope you followed through.

 

It was a weird feeling and kind of hard to describe. I thought for a split second that I accidentally pushed the gear stick to manual so i looked down to make sure that it wasn't...and it wasn't. I think i tried to then step on the gas to get it out of the stall but it was really budgeting until a moment later. First thing came to mind was i thought there's something wrong with the transmission but upon googling, I feel like there could be so many possibilities...

Other than that, I love the car...I just don't know if this is something serious...

 

Hmm That's an interesting thought... Could harder braking trigger that?? I wasn't going to change lanes actually, but i was braking like i normally would as if in my Subie with still a good amount of distance in front. I thought the car hated me at that point. I was expecting the rpm meter to go down but instead it just stayed there and didn't want to go anywhere. While the engine noise sounded like it was struggling. I think i tried to hit the gas to get it out but it didn't seem to want to do that either...how would you blaze around the person in front while the car feels idle? I was also just in automatic if that helps...

 

The transmission in sport mode tries it's hardest to anticipate your next move as if you're doing spirited driving, so a quick stab of the brake will encourage it to drop a gear or two (which might make the car jerk momentarily) and hold the revs high. Of course introducing additional brake (or accelerator) input can confuse the transmission logic and produce a numb spot where it's unsure if you're ready to accelerate or continue braking. I imagine that's what you're experiencing. Try replicating the scenario in sport and normal mode and see if you can confirm it.

 

I'm slightly scared to replicate it because i didn't feel like i was in control of the car at that time. Although i did take my car back out after the traffic died down a bit...but couldn't really replicate what had happened. Closest i got was i tried to get off of an exit at a higher speed than usual and brake harder than usual...and then i just feel the non-linearity of the brakes - kind of sending you forward in the seat a bit and taking small jabs at you. I feel like the car wants to come to a full stop - but because i was not coming to full stop and still have to keep moving, I had to left off the brake a little. This I believe i'm just not used to this car yet...

But back to earlier today...I think "numb" is a good way of describing it - like it was confused because i might have tried to climb and applied harder brakes with not much time in between. I heard the torque converter might have something to do with it? Very much confused...

 

The engine braking experience I'm having is not sport mode related. Happens in normal. I'm familiar with the sport mode stuff. It's similar but a bit different although probably part of the same systems.
I reproduced 2x today. Both times going downhill. I live in hilly area. I've read other reports of Lexus and Toyota vehicles doing the same.
When coasting downhill and going a bit too fast (slow poke in front) I tap the brake briefly. Engine downshifts. My goal isn't to be aggressive at that point, it's to maintain a steady speed down the hill. Downshifting and engine braking reduce need to use brake pedal as much.

I suppose it could be the computer guessing I'm in a turn and wanting to be aggressive, but it's normal mode and I'm not getting the sporty high rev corner action that I get in sport mode.
This is why I think it's more about braking efficiency rather than sportiness.

It doesn't feel unresponsive like OP though. It's definitely ready to roar if I want it to.

Some people say they don't like it. I'm getting used to it. Kind of nice as I don't have to ride the brakes all the way down the hill.

 

^^^ this.


the RCF is highly aggressive in this behavior especially in Sport+ scared the living hell out of me the first time I had to hard brake and the car dumped from 6th to 2nd in a heartbeat, I was not expecting the car to stop as abruptly as it did, I've had several vehicles with the large Brembo Calipers like the RCF and none of them stopped abruptly as the RCF. the downshifting behavior makes a huge difference. I've had several RC-whatever models as loaners when the RCF is in service and the behavior is the same, though not as aggressive, in those.


It takes a lot of control when I switch to driving my 1939 Ford Hot Rod with single piston front disc and rear drum brakes and a 40 year old 3 speed no computer controlled transmission. I have to actively remember I need 4 times as much space to slow and stop that car vs. the RCF.

 

I'm actually thinking I want to keep an even bigger distance between my RC (I don't have the RCF) and the car ahead, because I don't like the jabbing, abrupt sensation that the car sends when you apply the brakes harder than usual. So to minimize that, I'm going to adjust my driving style a little.

However, feeling like the car idles and doesn't want to respond wasn't fun...not sure if that's the right way to describe it, but i felt like i was actually driving on manual for a second when i wasn't. I'm trying to find an explanation for that one incident when i had no idea what the car wanted to do.

One other thought that popped into my mind to describe it is: the car needed to shift up to the next gear, but i didn't let it...which is false because i was on automatic...so it should be doing that itself. I think it got confused because it originally thought i was going to keeping up the pressure on the gas pedal but instead, i braked harder than usual?

 

well with an 8 speed transmission there are a lot of gears it has to go through when you make an abrupt stop from highway speeds. there is hesitation, sometimes worse than others.. if your car was in 8th and all of a sudden has to be in 2nd during a hard brake, then you mash the gas trying to accelerate back up to speed, the computer is trying to catch up to your behavior and it hesitates between the downshift and the new upshift demand in order to protect the engine.

I understand what you are describing, as I have experienced it in several cars. with 6-7-8 speed transmissions, there is a momentary hesitation when you go from speed to brake back to speed, even in taking a corner at higher speeds, where you brake into the turn and accelerate out of the turn, the car will hesitate on that reacceleration, it is annoying as all hell. which is why I have taken to doing such things in manual mode, then it stays in the gear I want it in.

 

This sounds to me like a bad Torque Converter.
I had a 2010 Subaru outback which was purchased new and had hard 120k miles on it. One day under hard hard sudden braking, the car just stalled out. Didn't think much of it until it did it again and again until anything more than a cruising stop will stall it out.
Dealer found the TC bad and it causes the stall from being unable to detach itself from the flywheel in time.

Hope that helps.

 

Is this a 2018 RC 350? They have the new safety package that might have something to do with it. I have a 2017 with RCC w/PCS, and from what I understand there are quite a few changes in the overall system in the 2018s.