Cross winds at high speed (un)stability
 

I recently testdrove MY2017 BRZ finally, and being on autobahns I can do some speed. I immediately noticed, that while the car being stable at high speeds, it was very vulnerable to (probably) any wind. The surface was smooth, so I don't think it was bad roads but rather wind, also I did not feel anything in a steering wheel (like from low-profile tires, etc).

I checked the forums and there are hints about it there and there, so I think it is worth to its own solution thread.

Around 100 mph car is "jumping" left and right, while obviously I drove straight. The car was stock, dealers presentation model. I am unhappy about it, since I want from a car to be able drive at those speeds at ease and it is one of the reasons I wanted a good handling sports-car. I have never experienced vulnerability like that in any car I have driven, including estates with much more side-area. And lastly, my Accord with the same Primacy HP tires (225/50/17) is rock stable at those speeds. No feedback and soft, but stable.

Do anybody know a reason for this, and more importantly, can anything be done to solve this to be at least "normal"?

Thank you!

Personally I do not believe it is wind, I had an old boxy '80s truck that was absolutely affected by wind and you could hear and feel when a gust caused the car to move. The 86 is absolutely less affected by crosswinds and large commercial vehicles due to it's low profile. There are some here that believe it is wind, I regularly drove across a bridge that routinely gets flagged with 'high wind advisory' 30+ mph gusts easily on a good day, the 86 is very easy to maintain in lane provided the alignment specs are conservative.

IMO it is wheel alignment and road related, ask for an alignment to be performed on the car, a little toe in all around will likely have it feel just like you want it to, factory alignment specs are not perfect, and maybe the dealership set alignment to be a bit more aggressive during pre-sale inspection since that's what many 86 buyers like.

I think it's dependent on the following element..


https://encrypted-tbn0.gstatic.com/i..._drBbELLXN5Okw


https://encrypted-tbn0.gstatic.com/i...SxV9C6PCO5kzeA

It's a dealer's model- check underneath and make sure the panels under the car are all there. Maybe it's been in an accident and the alignment is off? I get some cross wind buffeting but not as bad as you describe, though it got worse when I installed the lip kit. It doesn't get really squirrelly until over 120 MPH.

We drive well over 100 on the track and have never noticed that. We do use track tires and a good alignment, so I doubt it is body related.

I would start with the tires (uneven wear/uneven pressure) and then look at alignment and/or buckled wheels and then suspension (loose components) and then chassis for alignment..

Thanks, so basically you are saying it is not wind and it is not normal? That would be great. BTW weird, that it is worse with the lip kit - that should decrease lift if anything.

IMO it may still not stable enough for your comfort as it is a lightweight car, maybe your threshold for comfort is different than ours. I'd call the salesman up and say "hey the high speed stability concerned me, I would be very interested in the car if you could solve that, I believe a four wheel alignment may help, if you can have that done I'd love to test drive the car again, oh and I'd like to see the alignment printout of that isn't too much trouble"

If they refuse, head out to another dealer and hop in a different car. There's other things too like tire pressures and potential unseen damage, some cars had spring spacers not removed early on, things like that, but imo alignment has the biggest impact to how the car acts.

BTW, why not check tire pressure from steps listed by yourself at any fuel station?

keep in mind that the stock alignment is a wide range. you will get better results if you specify a certain alignment setting. I personally use the following settings:
Front:
Camber: -2
Caster: 6 degrees
Total Toe: 0

Rear:
Camber: -1.5
Total Toe: 1/16" total toe in

You can't touch that front alignment until you own the car. It will take more than just the common factory crash bolt, which typically maxes out ~-1.4deg camber. And caster will usually fall a touch short, ~5.8.

The car is definitely sensitive to alignment.

The other thing to consider here is that the car may simply be providing that much more feedback, so it's easy to notice those little annoyances where other cars they'd be absorbed by all the little things that make the car feel mushy...

I have felt this too OP. Windy day, strong gusts hitting the rear quarter make the back end of the car feel uncomfortably light at 100 mph. (Deserted highway, I had just been passed by an Audi A4 and sped up from limit just to see how fast he was cruising.) After a few seconds of "Whoa, this is new!" I dropped back to 60 and the car went stable again. Alignment is good, tires were almost new, pressures good. I do have the stock rear spoiler.
I think it is more to do with the shape of our cars. Not saying they produce gobbs of down force or anything but I remember a video on the development of the car where the Japanese engineers were talking about the shape and how every crease has a purpose aerodynamically. Even the little canards on the tail lights are there to do something.
A strong, gusty wind on the rear quarter definitely does lighten the tail end and push the car around a little at those kind of speeds, IMO. If I hadn't experienced it, I would have been skeptical.

I am in the same boat as the OP and have been baffled ever since I joined the forums that no one really compains about this.

When I first purchased the car I was extremely concerned about the squirly feeling this car has on the freeway. I bought 2 different sets of tires and got it aligned probably 4 times, had the dealer check everything probably 3 times and never found a solution.......until summer time.

I purchased my car during our windy season. When Summer came along and the wind went away it was like a completely different car. It is now windy season again and it drives me nuts!

I feel like it is a combo of the VSC, electric power steering and the electronic brake distribution trying to over compensate at times. I am convinced that these systems are still ACTIVE AND VARIABLE at all times even when the dash lights aren't indicating it(unless in peddle dance mode).

Thanks for the input. If you have this kind of behavior on the same roads with the correct setup, it seems like the wind is the variable. Perhaps you can try drive in pedal dance mode then? Personally I think it is highly unlikely this to be caused by ESP, but you never know. Can you try?

- was it windy?
- was the track hidden from wind? here in europe most track has tribunes and are in a hole with a lot of wind/sound deflectors like trees and barriers.
- could be body related but your track setup might compensate :iono:

Sorry I forgot to mention that, yes, I have tested the conditions in Pedal Dance Mode. The car does drive noticeably different in PDM. This is why I brought up the topic. PDM shuts off a few different systems tho so it is hard to determine which ones are responsible for the strange effect when driving in windy conditions.

Sent from my LGLS991 using Tapatalk

So you are saying, that you drive with pedal dance and the car is calm, and then you switch back to default all-on setting and the car became unstable like we experience? If so, then holy fuck.

I would not say the PDM completely eliminates the problem. But it does make me feel more confident when driving on the freeway.

HOWEVER, none of my "tests" were in absolute controlled environments. So having said that, all of this information could be completely wrong. There are MANY variables and at the end of the day no one factually knows what PDM actually does. There is plenty of hard evidence but nothing in writing anywhere that I am aware of.

Sent from my LGLS991 using Tapatalk

:confused0068:

I can't imagine what conditions are like that you're getting wheelspin while cruising down the freeway, that's just bonkers to me.

If the wheels aren't spinning the TC isn't doing anything and you're fooling yourself.

The traction control system does nothing on the highway. If you "feel" more confident on the highway with no nannies on, it's just because you feel good about it, not because you actually feel any difference. I don't think most people understand at all how the traction control system works.

When did I mention traction control?

Sent from my LGLS991 using Tapatalk

Pedal dance is explicitly a diagnostic mode that affects traction control, nothing else to my knowledge.

No electronic setting affects how this car travels down a road without tire slippage, excluding the engine performance.

Get a rear diffuser, front lip side canards, under panels and spoiler. Then get back to us.

I have all of these, with the exception of a rear diffuser.

Sent from my LGLS991 using Tapatalk

In response, Road America, Gingerman, Blackhawk, Chicago Autobahn. We do not drive in a hurricanes but yes we do get windy days.
Could your body mods change the air under the car in an adverse way? (I know it is supposed to help.)
I do not remember anyone else in the past 5 yr. having aero stability problems with a stock car.

I use Autodesk Flow Design wind tunnel software to ensure that call of my mods are aerodynamically functional. I have simulated it countless times in my wind tunnel and all of the mods help only due to increased downforce. However, downforce is only beneficial up to a certain degree before it starts to feel like you're driving under water.

Sent from my LGLS991 using Tapatalk

I was referring to the OP that had modded his car and was having problems in Europe with the car darting right and left in the wind.

Being in Europe isn't going to make a difference. I suffer from all of the same problems in America. 😞 And I have opted for all of the solutions in this post. So whether I am the OP or not, what is your point?

Sent from my LGLS991 using Tapatalk

I don't know that it helps with stability much, but a proper diffuser will change from lift to a touch of downforce in the back. I'm​ confident it would help at least a little.

I have been anxious to get one but I am the type of person who does way too much research for such simple things.

To you have one? Do you have a recommendation?

Sent from my LGLS991 using Tapatalk

The car was dealer stock, I have never said I modded anything. Our specs include OEM underbody panels and that MY2017 rear spoiler. It is really weird.

EDIT:
I have found this post with an interesting thought: http://www.ft86club.com/forums/showp...0&postcount=17

P.S.: I have a theory that not that much people experiencing this just because not much people travel at those high speeds? The faster you go the worse this is, so perhaps not much high speed driving with combination with wind makes this topic a bit underground?

EDIT2:
I just found on UK forum people noticing this too, with no solution. We are not alone :) Check this out:
http://www.gt86ownersclub.co.uk/foru...topic3573.html

Velox, Driveway labs... Others out there with less shared data. Not all exhausts always fit, etc. so you'll have to dig in a little still, I think.

sorry, I stand corrected.
I did not realize that yours came stock with different options.
again, not sure the two posts experienced what you were experiencing what you had happen at high speed. did you notice the instability at high way speeds? you seemed to say it was a high speed related problem.
I was only trying to help with a possible place to start looking, based on personal experience. we are all aware that all cars experience affects of strong crosswinds it is really a matter of how much.

Side splitters should help with cross wind, as they are intended to work when the car is in yaw. I noticed less buffeting around tractor trailers since I installed mine. Keeping the air from getting under the car is key.

I have just found another thread about this
http://www.ft86club.com/forums/showthread.php?t=20857
Still wondering what the hell is going on and how to make this car stable...

Still on the stock low-rolling resistance made-for-fuel-economy tires? That's what it was for me....proper performance tires cured the high speed wandering it liked to do.

I'd second the alignment suggestion. Our cars are already pretty good aerodynamically, with low Cd, small surface area and a functional rear spoiler.

If you want a 100mph highway cruiser, this car is probably not the best starting point (light, short, stiff susp.), but I'm pretty sure a good amount of toe in would make it much more stable on the highway, at the expense of low speed maneuverability.

In the thread I mentioned there is an another theory and that is soft bushings...