GR Racing Announcement: 4-5-2021

[Sport-Tech]

Fatter front tires will also reduce steering feel, all else being equal. That feel is one of the twins' great strengths, and should not be sacrificed for marginal gains in grip.

[Yoshoobaroo]

Originally Posted by nikitopo

People are usually thinking incorrectly that a bigger rear tire means always less grip on the front tires which is a myth.

But if you put that bigger rear tire on the front as well, you have more grip on the front axle too. All else the same, putting bigger tires in the rear increases understeer. Yes a skinnier tire up front will improve turn-in response, but if you don't have enough front grip to keep it from understeering, your turn-in doesn't do anything for you.

I'm sure the cost differences are there, but once you consider economies of scale, and the fact that you can use the same wheel front to back on a mild stagger, I'm not sure how much you'll actually see.

Originally Posted by Sport-Tech

Fatter front tires will also reduce steering feel, all else being equal. That feel is one of the twins' great strengths, and should not be sacrificed for marginal gains in grip.

You're correct, you probably want to keep the fronts as skinny as you can to preserve what little feedback the electric rack provides. I haven't driven a twin with 245s up front, maybe someone can chime in on the feel.

On a great hydraulic rack with superb steering feedback like an E46 or E9X BMW, I've found the difference in feel negligible between 225-255 tires up front. The balanced grip front-to-back was always worth it over all the downsides. Then again, those racks have a ton of feedback, so losing a little bit isn't the end of the world.

[nikitopo]

Originally Posted by Yoshoobaroo

But if you put that bigger rear tire on the front as well, you have more grip on the front axle too. All else the same, putting bigger tires in the rear increases understeer. Yes a skinnier tire up front will improve turn-in response, but if you don't have enough front grip to keep it from understeering, your turn-in doesn't do anything for you.

I'm sure the cost differences are there, but once you consider economies of scale, and the fact that you can use the same wheel front to back on a mild stagger, I'm not sure how much you'll actually see.

Let me tell you what the factory did in the 86 GR model with the staggered setup. They increased much more the rigidity at the rear and added a much bigger rear sway bar. This setup was transferring in corners more weight in front and decreased the understeer. I am not saying that this is an optimal setup for the race track, because the front tires will get hot sooner. It is just a solution for street cars if the manufacturer wants to keep a balance with all the others things we were discussing.

[Blighty]

They make the new michelin PS Cup 2 Connect in our tire size.

If you want to add some grip and keep/increase steering feedback.

[ZDan]

Originally Posted by nikitopo

Styling is always subjective and something that will look nice to one person, might look different to another person. I have read for example your posts about how the platform would look better if there was a 2 seater version comparing to the 2+2 seater version.

Really more for better weight distribution, shorter wheelbase, lighter weight, but yeah I like the cab-rearward 240Zesque proportions better as well!

For example, a manufacturer shouldn't take the risk to change too much something that was a financial success. The shape/proportions of the new car are the same as you said, but if you take both generations side by side the exterior changes are too many.

That would be a dangerously overly-conservative approach, to barely change anything over the course of many years. Most people don't want to buy a car that looks like it's already 9 years old. Sometimes change is good, sometimes it's bad, in this case I think it's mostly positive but I'll give the nod to having some changes in any case, as long as they're not terrible. Which in my subjective opinion these changes are not.

About the engine, I believe that it was the most wise decision. However, it is still weird to increase the engine displacement and performance and keep the same tire width front and rear. I would expect to increase the tire width squared or even going to a slight staggered setup, something that was done already 2-3 years ago to the real GR86 version.

I could see them going to 225s all around, but staggered setup would be pointless on this car given 55F/45R weight distribution and 13 lb/hp. If anything wider *fronts* would make more sense, given how much more front wear I get at the track even with 3 - 3.5 front camber. I actually considered doing that this year for time trials, running 245 fronts with 225 rears to save 20 lb. in classification points.

Maybe, I am influenced by the German manufacturers who are usually more conservative between model revisions. Or to phrase it better, if they will do changes they will do on things that really matter to a street car and not on things like the fake vs "real" vents.

Like the latest M4 front end? I guess it really mattered to make it look like that!

[nikitopo]

Originally Posted by ZDan

If anything wider *fronts* would make more sense, given how much more front wear I get at the track even with 3 - 3.5 front camber. I actually considered doing that this year for time trials, running 245 fronts with 225 rears to save 20 lb. in classification points.

Funny how people think that a track focused setting as the above would be safe for the street.

It would be for sure a quite tail happy option in non-well maintained and slippery backroads, but quite inappropriate for most drivers. I am sure legal departments would make great fun with suggestions as the above.

[ZDan]

Originally Posted by nikitopo

Funny how people think that a track focused setting as the above would be safe for the street.

I was kinda joking there...

It would be for sure a quite tail happy option in non-well maintained and slippery backroads, but quite inappropriate for most drivers. I am sure legal departments would make great fun with suggestions as the above.

Effect of tire stagger on general handling characteristics is almost always *way* overestimated. It makes a small difference in handling balance compared to other factors.

A staggered tire setup makes zero sense for the stock BRZ/86, given 55F/45R weight distribution and 13 lb/hp. No good reason for wider rears.

[Transport3r]

Originally Posted by ZDan

Like the latest M4 front end? I guess it really mattered to make it look like that!

You can make that ‘everything on the new M3/4’. Damn thing doesn’t look like a BMW no matter how you look at it. So many striking cues that started in the 60s and were carried all the way through to the FXX cars are just gone.

Crease across the fender tops and through the door handles? Gone. Replaced with generic flank surfacing copied from current Benzes.

Hofmeister kink? Gone. Replaced with corner window form a 5 year old Hyundai.

The SUBTLE M-power bump on the hood? Started on the E46 and has been there since. Gone. Replaced by the hood off a 2012 Dodge Charger.

Distinctive tail lights that immediately identify a BMW? Gone. Some Lexus units will do.

Subtle but noticeable wheel arches bulging out, wrapping around the tire? Nope we’ll make the wheels look sunken in and small instead.

Slightly raised trunk from the E30 M3 and the slightly notched-up roofline that leads up to it? Nah the current mustang profile works too.

Not even going to address the kidneys. In fact, they’re the only thing that even call back to ANY of BMW’s styling.

The M4 is one of the most generic car designs I’ve ever seen. It has no personality at all, except for the ridiculous buck teeth. It’s not even that ugly, it’s much worse than that. It’s boring.

Edit: wow, sorry. Rant over I guess.

[nikitopo]

Originally Posted by ZDan

Effect of tire stagger on general handling characteristics is almost always *way* overestimated. It makes a small difference in handling balance compared to other factors.

A staggered tire setup makes zero sense for the stock BRZ/86, given 55F/45R weight distribution and 13 lb/hp. No good reason for wider rears.

I don't think it is *way* overestimated. Germans are using this setup for decades. It was a kind rule of thumb for rear wheel drive cars after model revisions and not necessarily only on mid- or rear- engine setups. Check here to see some results on our cars:

GR86 front 215/45R17 rear 235/45R17
GR86 best lap time 1'18"40

BRZ STI sport front and rear 215/40R18
BRZ STI sport best lap time 1'20"54

Both cars on Michelin Pilot Sport 4 tires. I believe Gazoo Racing didn't do the same on the new GR86 car mainly for cost reasons.

[ZDan]

Originally Posted by nikitopo

I don't think it is *way* overestimated. Germans are using this setup for decades. It was a kind rule of thumb for rear wheel drive cars after model revisions and not necessarily only on mid- or rear- engine setups.

Those German cars are much closer to 50/50 weight distribution than ours are. I do remember when the E36 M3 went from 235 square to 225F/245R. The most common theory was this was more to ensure understeer at the limit rather than max performance. Of course the thing to do was get another pair of rears and run them up front. Most serious E36 M3 trackhounds I know (those in the mid-200s rwhp range and not running significant downforce) run square tire sizes.

Check here to see some results on our cars:
GR86 front 215/45R17 rear 235/45R17
GR86 best lap time 1'18"40
BRZ STI sport front and rear 215/40R18
BRZ STI sport best lap time 1'20"54

You can rest assured that the 2 second difference in lap times is not down to tire stagger. No subtitles so I have no clue about how the cars were set up, but I would bet if wheels/tires were swapped that BRZ STi would not end up being quicker than that 86. 17" vs. 18" wheels might also have something to do with it, but again nothing like 2 seconds. If setups are similar, I'd guess that the BRZ's tires have gone "off" (I had a set of Michelin PSS do this, with plenty of tread left). Also, it'd be interesting to see how the GR86 did on same tires in 225/45-17 all around, with adjustments to re-optimize for the square setup.

I never got hugely different overall handling characteristics running different stagger setups on S2000, LS3 FD RX-7, or 987.2 Cayman. Noticeable, yes, but nothing major, less of a factor than getting camber and toe settings right. And lap times were affected by tenths of a second, nothing like 2 whole seconds!

I believe Gazoo Racing didn't do the same on the new GR86 car mainly for cost reasons.

For sure that's part of it. Also, bigger wheels/tires are heavier and they obviously have paid a lot of attention to keep weight in check. While I think going with a staggered setup would have been dumb for *this* car (again, 55F/45R, modest power/weight, and a Torsen diff which will ultimately have inside rear wheelspin if too much roll stiffness is apportioned to the rear), I think they should have gone 225/45-17 all around with the better tires rather than going to 215/40-18. Car doesn't need 18s, and the brakes look absolutely LOST inside them!

[nikitopo]

[Dadhawk]

Originally Posted by nikitopo

^video^

Unless that line between the tail lights does the Cylon eye thing, I've had to black out the spoiler.

[Tcoat]

Originally Posted by Dadhawk

Unless that line between the tail lights does the Cylon eye thing, I've had to black out the spoiler.

[Transport3r]

Originally Posted by Dadhawk

Unless that line between the tail lights does the Cylon eye thing, I've had to black out the spoiler.

That would be a great idea for the aftermarket to make a lit trunk trim piece.