Power steering issue with slicks?
 

I got some new Hankook slicks for previous race, it was my first time run with slicks on BRZ. However with slicks the power steering stops working(or feel like no power steering) sometimes, mostly during high speed turns, some low speed turns too. But when I switch back to AD08R the problem disappeared. 2 of my other friends has same issue on their GT86, so I assuming this is a common problem with our cars??? I was wondering if any of you found out solution to fix this issue?

I had this happen to me on rs-3s this weekend right after a right hand sweeper transitions quickly to a sharp left. felt like i was driving a go kart for a second. theres a more extensive thread about this somewhere on here, by i think evasive motor sports or element tuning.
http://www.ft86club.com/forums/showthread.php?p=250538

Yeah, this seems to be pretty common on the track, especially when you start using stickier tires. It happens to me all the time and you just get used to it. I'm so used to it now that I didn't even remember that this was an issue until I let someone else drive my car on the track and he complained about the steering getting weird at times.

If you are getting the sensation that the PS isn't working, it means that your car is too low for those slicks. We had this issue when running Continental Race Tires, we raised the car slightly and the binding went away in the turns.

-mike

what is actually binding, the tie rods at too extreme of an angle? im lowered only 30 mm and not even on slicks.

I will try raise the car a bit and try, my car is running complete racerX arms with whiteline roll center adjuster tie rod joint, and I am not a fan lower my car a lot, didn't thought this way.

My impression is that this happens while trail braking too hard and ABS is about to engage. Easing off the brakes just a bit makes it go away.

I wonder if there is a power drop to the steering due to power used by ABS??

I've experienced the same thing - My car is lowered as well on 245 17 RS-3's
I've learned not to trail brake on tight, high G corners. It definitely feels like ABS kicking in when you don't want it.. possibly affecting power steering.
I haven't tried the same tight roads with the pedal dance engaged (all aides off). I always run with TC turned off, but not the pedal dance as much. I need to try this and see if that helps at all.

I always use pedal dance.

Mine is lowered 20mm.

Have experienced this on several tires: PSS, AD08, RE11, NT01 and Z2 Star Spec

FWIW I experience this on stock suspension with BFG R1S tires.

I run Pirelli DH Slicks and have the same thing occur. I think it is definitely the fact that we have waaaay more grip than the system was designed to operate with.

I get the same with stock suspension and semi-slicks.
I'm so used to it, I don't notice it anymore.

Anyone got a fix for this yet?

Man handle the steering wheel. The steering still works, you just have to use more force on it. Think of it this way, if you arent getting to the point it shuts off, you can still corner faster there :burnrubber:

My bet is due MY2017 among changes listing fixes/improvements to electric powersteering to not overheat with sticky tires on track, that this is the reason for loss of powersteering on older models.

Things that may affect powersteering more - ones that make it work more/counter larger forces. Yes, sticky tires included. Other things that may imho impact - things like wheel spacers/higher wheel offsets (changing scrub radius, heavier steering/more load on power steering), extra caster (also will make steering heavier and more straightening forces to wheel in turns). Don't know about camber impact on steering/power steering.

I somewhat doubt in ability to retrofit MY2017 power steering to older ones and also doubt Toyota doing something to "fix" it on older ones. It works fine on stock spec suspension/tires and during daily driving within legal limits, it works when you ask reasonably more (like interim tires between slicks and stock) and on track .. i doubt Toyota will see it as "bug" to fix. Not even majority of all the twin owners/drivers had been to track even once, so why should Toyota loose money on that for older ones?

Hmm .. on second though, if it's due overheating .. i wonder if some extra cooling mod of it may help? People seen other cooling limits for engine oil, tranny oil, diff oil and implemented track worthy mods/rads/cooling for those .. why not think of something for powersteering?

I myself most probably will never use slicks but at most something like MPSS or AD08R of reasonable width, so again very probably i won't care about it :)

Power steering is electric and is under the dash. Why would an electric power steering in the cab of the car need additional cooling?

Actually thinking about it, since process of going into a high G turn is braking, downshifting etc which also has the RPM's dropping has anyone ever tried putting a voltage meter on the power to the electric motor to see if a voltage drop is causing the issue?

Under heavy usage the electric motor generate a lot of heat, and it overheat, and cut on thermal protection.
But I've seen people in other thread saying that they had PS issue on the first lap of a session, so it's not overheating in those particular case.


I've not had this problem on my 2017, but only used RE71R in autoslalom.

what about trying to pull the fuse or power connector to the PS and see if it steering manually will feel the same. If it feels different than the motor is the issue.

BUMP.
This is still an issue for with my track car and getting worse with addition of a splitter giving some downforce. It happens under hard cornering, especially when the front is loaded at the bottom of a dip or cambered turn

Has anyone come across a fix for the EPS system being overpowered and momentarily shutting off the power assist?

EPS overheating? Yes, recall posts about that. The grippier the tires, the more there is downforce, the higher offset, the higher caster, bits that make EPS working more, may trigger overheat of EPS resulting in temporary disabling to cool off. Haven't seen yet if anybody managed to fix that (except dialing back some of things that make EPS work harder (eg. caster)).
IIRC one of things fixed in MY2017 from change list. Haven't seen if someone was successful retrofitting restyle EPS either.

My solution is to grip the wheel harder through corners I know may cause it to cut out :iono:

Have seen no fix.

Make sure it really is EPS shutting down and not your tire contacting the inside top of your fenders. Check the plastic to see if there are scratching marks in it (any marks at all means you are touching up top).

Wasn't EPS switching off due overheat (so far haven't experienced by myself) indicated as red steering wheel light on dash?

:iono:

I can't see my factory dummy lights. My aftermarket gauges are in the way.

Thanks for the replies. Yes I reduced caster and it helped a bit but its still a problem.

My guess is that this is some safety circuit to keep the motor from overheating, not actual overheating , because it happens on the first lap not just after a long session.
I bet if we had an electronics expert or some inside information this overheat safety circuit could be disabled. Maybe with just a snip of a wire or a resistor. I would risk a motor burnout to possibly fix this issue.

If it happened on first lap and possibly is not temperature triggered .. then i guess it might be rather from what strength/torque from EPS is asked to turn a wheel. Not sure it's that simple of a fix, it might be also some programmed firmware logic. I'd rather explore possibility of retrofit of EPS from MY2017.

@ROADRACER did you actually went and checked your fender liners inside on the top? It sounds very much like you are just hitting it with your tires and it "locks" the steering into place while it rubs. Just check it, takes no time and you can at least write it off the list if its not that (but it does sound like it is to me).

Yes, I have checked. It is definitely not from a clearance/interference issue.

I think you are correct. I think the power being ask of the EPS motor is beyond the design limit. I wish there was a way to just reduce the assist level to a point it didn't exceed the limit, or raise the limit with a firmware modification.
I would bet there is a Japanese guy sitting at a desk at the Subaru factory in japan that made the system that could fix the problem...unfortunately I don't have his email address.

As with car stock, with less grippy tires, with stock alignment, it's unlikely for problem to occur, i somewhat doubt for there to be official fix. Unfortunately twins with at least stock alignment, are not of optimal setup to track often. Even more so, if updated EPS is among new features of restyle model, and even though if not among major, but extra incentive/selling point. And actual engineers in most big companies are almost never possible to reach directly by customer according common practices. So i guess, that any possible fixes for older twins EPS will probably be unofficial and may probably come from own experiments or will from community.

Is there a fix / hack for this yet? I ran my SC'd car yesterday for the first time and this was happening all over the place, I thought it was wheel on hard part at first until I found no evidence and I did a bit of reading online.

I run a Koyo unit in my Miata that looks very, very similar to the BRZ one and have never had an issue, so I'm pretty surprised to find out the cause here.

Yes, stop letting your front tires rub inside your wheel wells. Increase the ride height, get stiffer springs, etc.

Tires are not rubbing anywhere, 600lb / 700lb springs, ~130mm to pinch weld, etc. Only driven the car one event so far, pace was TT4 record pace in what will be a TT3 car so a few seconds off TT3.

Someone makes an upgraded motor for the EPS. I just can't remember the manufacturer.

Check that end links aren't binding too.

I had this issue plenty on my 2013 even with no bind or rubbing. Annoying.

Okay, they are the stock ones up front that I'm replacing with RacerX as I type this. :)

I saw the one company that was mentioned before, not sure what the price point is but it looks like the same unit (Koyo) I run in my Miata and am really happy with.

I wonder if the revised units will plug and play in older cars

These are the ones I use without any issue. Make sure your sway bar can clear your lower control arm. You can check this by removing a strut and end links and rotate the sway bar up and down while the LCA is in an upward position as it if was under cornering compression.



I have scuffs on my LCA where my massive Eibach sway bar occasionally just skimmed it when I had the length of my end links set wrong.

I went through everything more closely after reading your comment and found this hiding behind the struts. Not sure if it was there from before I bought the car, but I think I'll need to pull a tiny bit of camber out or see if the OEM -> RacerX links bought me enough clearance. I didn't really find any evidence on the original endlinks that I'd expect for contact, but better safe than sorry.

https://i.imgur.com/VmdkWiE.jpg
https://i.imgur.com/B1ZoKTV.jpg

Slap some painters tape on the spot to see if it happens again.

Im with most people here on that its probably rubbing somewhere. If its happening everywhere (or very often) its not the EPS cutting out, that only happens under very heavy load, so usually cambered turns or big elevation changes at turn in points. Since you didnt post any pictures of it, look UP inside your wheel wells. The tire usually rubs on the black plastic (fender liners) right above the tire at max compression if you are too low, and 130mm is very low.