OEM primacy HP vs OEM PS4S stiffness
 

I've long been a supporter of the stock primacies because of their stiffness and feedback. I believed part of this was due to the Eco rating which requires a stiffer sidewall resulting in less rolling resistance. Now that the 4s have the Eco rating I'm willing to give sticky tires another shot. I believe the 19 TRD edition and brz ts have these tires. Any input from owners of the new PS4S?

Thanks.

The primacies sidewalls feel no stiffer than a decent set of performance tires like the mpss. havent tried the newer ps4s.

The PS4S are a very good street tire. You'll like them. Get a good alignment while you're at it.

- Andrew

Except they are available only in US :( in usable sizes. only 19-20-21" in EU, just non 'S' PS4 being offered in usable sizing for twins. And non 'S', while great street tire, runs a bit short for dual-use daily and track tire.

Went from the stock to MPS4S in 225/45 R17. Would never think on going back. Unless you have changed wheels I would stay with the stock size.

Does PSS/PS4S ruin the raw and sporty feeling from the stock tires by being too mushy/floaty due to softer compound/sidewalls?

I believe main decision for factory to fit primacy HP was the sidewall stiffness. I don't think it is a coincidence when they installed higher grip tires (MPSS, PS4) they went in 18" wheels.

When you say they installed the PS4 on 18" wheels, do you mean they did so to get a thinner sidewall to try and offset the soft sidewalls? And doesn't the PS4's on the BRZ Ts come on 17" wheels?

Yes. A thinner sidewall could offset a softer sidewall. All tS editions in US and Japan had 18" wheels. They didn't do it for Brembo clearance, because the PP editions had a 17" wheel with Primacy HP.

Serious?
"raw and sporty feeling" from tyres that were stock on a Prius...
"too mushy/floaty due to softer compound/sidewalls" for tyres they fit on Porsche GT3's...

I think it's a false premise that stiff sidewalls equal feedback or "feel".
Tyres are hugely complex structures with side wall "stiffness" being only one part of a technical jigsaw, that is often counter intuitive.
Remember, "run flat" tyres have stiff sidewalls and they are way way less than ideal...

I have never heard a tire to be categorised based on which car is fitted like for example in some Prius models. This nonsense is mentioned only here. Good tires might be fitted in econ subcompact cars and in more expensive cars. There is a reason tires come in different sizes. What should we say if these tires came in a BMW 3 series? That it's wearing Prius tires? Lol. Designers were looking back in '12 for a tire with stiff sidewalls. Everything else is a coincidence.

Sent from my SM-A105FN using Tapatalk

I have never read or heard that "stiff sidewalls" (whatever that actually means) was the criteria for the initial tyre choice on the 86/BRZ.

At the time of the 86/BRZ release the much stated primary intention of the tyre choice was about the car not having too much mechanical grip... and yes, at the time, much was made of the fact that it was the same tyre as fitted to the Prius. Toyota itself made a point of it, as did every single road test journalist. It was not just a "coincidence".

Yes, the stiffness is one of the aspects that I personally find makes the car feel more like a sportscar and induces excitement. From your point of view, sporty tires should be categorized based on what type of cars they are fitted on?

Also, I'm not saying that soft sticky tires aren't sporty, but I'm simply trying to figure out if it gives up on the stiff feeling property of the stock tire.

Check below snapshots. They are saying that they are ECO tires, but also expensive and well balanced tires. They wanted to focus on the suspension and body development and they decided to use these tires. They mentioned that these were also fitted to Prius (performance package in Japan) to point out that you can develop a good handling car without focusing just on tires and speed. There are also other aspects of handling like agility and good balance of the whole car.

And as said before these particular tires were provided as a factory option in BMW 3-series and 5-series. No journalist ever said that BMW was doing this to provide less grip on their cars. My personal point of view is that the mentioning of the "Prius" tires by the designers was an unfortunate moment, because they didn't manage to pass clearly the message. Then journalists either misinterpreted the argument or just distorted it for their own interests by saying it has "crappy" Prius tires.

When you say a "stiff feeling" what exactly are you talking about? Response over bumps? Harsher = stiffer? Feedback through the chassis (steering wheel, pedals, seat)? Hard compound? Lower grip level?

Can you elaborate on what a "sporty" feel means to you?

Yes, I want a tire that retains the stiff feeling where when you go over a bump or rock, you would feel it through the car. Not crashy, but a dampened yet obvious feel of the road imperfections.

What I'm trying to stay away from is a tire that would instead cushion those bumps like more luxurious cars and in the process make your car feel disconnected from the tarmac and become floaty.

So back to my original question, would the Ps4s fit my criteria? :happyanim:

I don't think PS4 S will make the car floaty. You might lose a bit of steering feel if you keep the stock wheels, but it should not change radically the car. On the other hand, the PS4 has been said to have softer sidewalls and to lose information. A stickier tire that gives faster laps, it doesn't mean that it is always better. So, take care that you fit the correct tire.

Here is the correct tire: https://m.tirerack.com/tires/tires.j...odClar=Limited

Due being in EU and having only "normal" PS4 available in 17", not PS4S, i tried only it. And with stock sized those (on x7.5" though) steering felt sharp enough despite being more street oriented. Non-S didn't stand well to track overheating though.

Yes on 7.5" wheels on a stock size tire the PS4 will behave better.

The PS4S is an exceptional tyre that's designed with fewer compromises than a Primacy (ie. it doesn't have to cover such a broad spectrum of potential uses that a Primacy is intended to).
You will not be disappointed with a PS4S, and it will not feel in any way "less sharp", it is a number of steps up the ladder in that regard. In fact it will probably highlight other improvements that could to be made over the standard suspension.
I have never said the Primacy was a rubbish tyre because it was standard on the early Prius (and journalists at the time did not say that either!), but rather that the suspension engineers specified it because of some of its inherent characteristics... one of which was not endowing the car with too much grip (ie over tyre-ing the car).
I truly don't understand the fixation on "side wall stiffness" in this particular context as I'm not sure that it is necessarily the magic ingredient that you may believe it is in a tyres "sporty" feel.
Whether or not you want/need the extra mechanical grip is probably a more interesting question.

Grumpy has covered most of the bases. I'll add that my experience has been with Continental EC Sports. That has been that the Primacies were low grip tires - the limits of the tires were quite low. On very good asphalt a modestly brisk pace would generate screaming worthy of a 3 year old's temper tantrum.

The ECs are much less dramatic - the limits are much higher. I did not notice anything that seemed to deaden the feel through the controls or make the car seem to "float." Some folks like the "friskier" nature of the OEM tires. If you like the lower limits stick with them. I got tired of countersteering in situations where I didn't think I should be having to do that or having to listen to the tires caterwauling and extracting my wife's fingers from the door handle when we stop for a light. I find the car much more enjoyable - YMMV.

You don't need to change the tires to fix countersteering behaviour. They "fixed" it in +'17 models without changing the tires.

My question for you would be, why are you needing to countersteer? Did the rear step out on its own, or did you get a little exuberant with throttle application?

Stock tires are fun. They are the Goldilocks tires for the platform. I don't want/need more grip. I like a bit of predictable slip angle at legal speeds. Sidewall stiffness pairs nicely with the grip level.

And yes, the stock setup pushes. It's designed for the general public. Of course it pushes. If you're kicking out the tail unintentionally, you're doing it wrong.

Exactly this. I'd never driven a car with tires that squeal while doing a normal u-turn until I drove my FR-S on the OEM Primacies. I never found anything remotely fun about them and couldn't wait to get them off, literally nothing redeeming about them besides perhaps fuel economy. The PS4S is a genuine upgrade in performance, seems about equal in road noise and comfort, and is less expensive to boot. If someone does want a low grip tire to drift around on, you can buy some decent all-seasons for half the price. Replacing the stock tires with another set of Primacies is essentially like setting money on fire.

"normal u-turn" bit is arguable. When few years ago i drove first times in mine, i noticed that i often take turns/roundabouts at higher speed/pace then in my previous cars. I guess, (possibly many do) because gauged safe speed from car's roll extent (obviously higher in more comfort oriented/softer sprung/of higher center of gravity family cars/SUVs) aswell, and as this rolled less, i pushed more. And if so, i see nothing out of order, if tire slips extra from time to time. It even provided me extra fun moment. It's upto driver to gauge grip level and drive accordingly. I wouldn't claim that even on primacies twins have less grip and are less capable then other cars. I just pushed more. On track, even on supposedly "gripless" primacies, i could drive faster then on many "family cars", that supposedly "don't squeal" on "normal u-turns".

I have stock sized PS4S on a set of 8" wheels. The difference in stretch vs 7" wheels may effect the responsiveness of the tire.

I view the PS4S as a straight upgrade. Grip, response, road noise, wet performance.
The main downside to me is that the factory spring rates clearly weren't designed for that amount of grip. Last summer on stock springs I could easily put the car on the bump stops in corners.
The car still handled great, but it obviously felt different. Pros/cons.

I wasn't a fan of how it felt. Since adding RCE yellows and camber bolts the suspension feels way happier dealing with the extra grip.


Primacys are a ton of fun on the street. So grip limit is so approachable, you get chirps and squeals before you get near the limit. Really just depends on how you like to drive...

This is helpful to hear your feedback on the impact to the stock suspension after adding more grip. It'll be something I'll look out for when I swap to something like the RT660's with stock suspension and stock wheels.

Everything is connected after-all. Brakes will be the next area of focus.

The latter.

If you start going faster, it'll still happen even with stickier tires!

That said, I do love the feeling of when the car just hooks and you go, rather than dealing with wheelspin.

Although the speed/accuracy of the drivers inputs then become even more critical....

Mmmmm depends on the tire. Some tires break away progressively, while others are abrupt.

MPS4S is fairly progressive, especially with the soft sidewall and the tread squirm.

For sure, but I guess my point is more that the forces released increase with speed/grip... the tail moving out at 100mph on stickier tyres requires a different skill set to those needed on a wet round-about at 25mph on lower grip.

I actually teach people to deal with this for a living. The forces are identical if the conditions are identical! If you can do it at 25mph, you can do it at 100mph!

However, the release at 100mph dry will probably be more progressive than 25mph wet, with a larger window for recovery, since the yaw impulse that started the unwanted rotation is likely smaller. I'll have much busier hands in a tight low speed slide than in a big high speed slide. However, if an 86 with sticky tires is loose at 100 mph, I'll be pretty darn impressed!

Slicks are a different story, but they don't belong on the street to begin with.

Nah, the energy forces are not identical... the energy released in a 100 mph tank slapper is far far greater than at 25 mph.
The energy released when a sticky tyre loses (and gains) grip is higher than when a low grip tyre gives up in a comparable situation. Cornering forces are higher.
Hand speed and reaction times need to be much sharper at high speeds, particularly when gripping back up, when the car immediately wants to follow the nose.
I feel its a bit glib to say that anyone who can catch/recover a slide at 25mph can do it at 100mph... (particularly on sticky rubber.)
Excluding race tracks, how many drivers do you know who can actually cleanly recover an 86/BRZ when the tail unexpectedly comes out at 100mph in a long sweeper that they have misjudged, in the real world. Or 90 mph. Or 80 mph. Or even 70mph?
:)

grumpysnapper: in certain conditions it's not that hard. After all, the quicker one corrects, the less correction needed. And when one pushes near limit, be it slow corner in wet or high speed one in dry, one on track imho should always anticipate possible slide due mismanaged mass transfer mid corner or too eager accelerating out of corner, this anticipation imho noticeably cuts reaction time to correct. Of course, concentration during daily driving is much lower .. but then again one shouldn't push dangerously on public roads either, leaving much higher safety margin. And if no skills (and especially due lesser concentration level & more uncontrollable variables), one shouldn't drive on public roads without nannies too.

Thats true, in certain conditions, and with certain skill sets. And talent or hard work.
For most drivers difficulty increases with speed, as the skill sets needed increase.
99.9% of drivers are not driving on the track, and the tyres we are talking about are also mostly used in the real world on real roads.
The reality is that real world road driving is what our cars were primarily designed for, and that's also where most still (hopefully for a little while longer) get our pleasure from.

The kinetic energy held by the car is greater, yes, but the lateral force exerted by the tires is not significantly changed without aerodynamic intervention.

Outside of the racetrack, the average driver doesn't have the opportunity to safety attempt correcting rotation at those 70-100mph speeds!

I have the OEM wheels and tires in storage. I would really like to refit those, find a skid pad and spend some time getting to know the car closer to its limits, but I'm hundreds of miles from a track and Texas is still in the grip of Sars-Cov2.

I doubt I can persuade a local mall or the university I just retired from to let me set up a 200ft circle in one of their parking lots. :(