Picking New Tires, Trying To Get More Front Grip

ScottOmatic · 07-04-2015, 05:36 PM

Quote:

Originally Posted by Jordo!

Hmm. I was going to suggest a square set up as well, but really in order to keep tire size and compound a constant more than to play with relative grip -- a lot of that will depend on alignment settings and weight distribution/suspension more than anything.

I guess you could buy ultra sticky fronts relative to the rears, but that sounds like it will just make the car unpredictable...

GT Porsche 911 track cars often run harder rear compounds due to all the weight being over the rear axle but of course, those are engineered to work correctly from the tire supplier and the rest of the setup is dialed in in every other aspect along with track time.

I think running 2 different street tires with different compounds and different tread patterns that are meant and have only been tested running on all 4 corners is hairy at best.

Even if the effect is generally positive in the dry it could be a nightmare in the wet.

As you touched on, the other idea I have had was upgrading the rear sway-bar and leaving the front alone. This would be a pretty cheap upgrade and I could always add the front later when getting new springs/struts or Coil-Overs, which I am sure would take out most of the understeer with default tire sizes.

The reason I don't want to just spend the money on a full suspension setup right now is that I am trying to pay off my 2014 FJ Cruiser early (that currently takes precedence when funneling money into cars) and to be honest, I am slightly worried I will get the bug for a different sports car in a few years and know it will be hard to get my money back in upgrades (Currently under 23,000 miles on my Z so everything but the tires are still pretty fresh).

Maybe I will get some new suspension components in awhile, maybe I will eventually get a tune, but until I make that decision I am going with the bang for the buck approach.

I should say I already bit the bullet on a cat-back exhaust a year ago, I'm sorry but the default exhaust setup just had to go!

Rusty · 07-04-2015, 06:27 PM

You should read the track section. Everyone is running the stiffest front bars, and the biggest tires they can. Some are running no rear bar at all.

Spooler · 07-04-2015, 10:02 PM

Your best savings will be reading and searching. I do quite a bit of that on here. Only spend the money once, will save you a fortune in the future.

Jordo! · 07-04-2015, 11:30 PM

Quote:

Originally Posted by ScottOmatic

GT Porsche 911 track cars often run harder rear compounds due to all the weight being over the rear axle but of course, those are engineered to work correctly from the tire supplier and the rest of the setup is dialed in in every other aspect along with track time.

I think running 2 different street tires with different compounds and different tread patterns that are meant and have only been tested running on all 4 corners is hairy at best.

Even if the effect is generally positive in the dry it could be a nightmare in the wet.

As you touched on, the other idea I have had was upgrading the rear sway-bar and leaving the front alone. This would be a pretty cheap upgrade and I could always add the front later when getting new springs/struts or Coil-Overs, which I am sure would take out most of the understeer with default tire sizes.

The reason I don't want to just spend the money on a full suspension setup right now is that I am trying to pay off my 2014 FJ Cruiser early (that currently takes precedence when funneling money into cars) and to be honest, I am slightly worried I will get the bug for a different sports car in a few years and know it will be hard to get my money back in upgrades (Currently under 23,000 miles on my Z so everything but the tires are still pretty fresh).

Maybe I will get some new suspension components in awhile, maybe I will eventually get a tune, but until I make that decision I am going with the bang for the buck approach.

I should say I already bit the bullet on a cat-back exhaust a year ago, I'm sorry but the default exhaust setup just had to go!

I think that's great idea! The OEM tires are actually pretty good (the Nismo RE-11's are better, but the ones you have now are still excellent).

Also, it's probably best to play with only one (or two) variable(s) at a time. I think go with the stiffer rear sway and hold off on the front for now, as you said, and see how that feels.

The only other change you might play with at the same time would be alignment, but otherwise, manipulating one thing at a time (in this case rear sway) is the best way to gauge its individual effect.

So, in summary (I'm rambling, sorry

), a good way to go might be to try the rear sway first, see how it feels, and then either do front sway or tweak alignment next.

jpkirk · 07-06-2015, 05:02 PM

Quote:

Originally Posted by Jordo!

Hmm. I was going to suggest a square set up as well, but really in order to keep tire size and compound a constant more than to play with relative grip -- a lot of that will depend on alignment settings and weight distribution/suspension more than anything.

I guess you could buy ultra sticky fronts relative to the rears, but that sounds like it will just make the car unpredictable...

So, assuming equal sized tires of same make, you want to stiffen up the rear relative to the front. That means a beefier rear anti-sway bar and firmer damper settings in the rear and softer in the front, if you can adjust them. Any other bracing you can add to the rear (without adding significant weight) will tend to nudge you more towards oversteer.

I think, maybe a little more camber in the front relative to the rear will help tuck the nose in too... not 100% certain on that one off the top of my head.

Scan over this site for lots and lots of advice on setting up cars for road racing

Autocross to Win (DGs Autocross Secrets) - ATW Home Page

This thread is helpful too

Suspension adjustments and how they affect handling

Dang, beat me to the Far North Racing link.

jpkirk · 07-06-2015, 05:09 PM

Quote:

Originally Posted by VSS370z

Wouldn't motorcycle tires be better optios?

Too wide and heavy and rolling resistance would increase torsional loads.

kenchan · 07-06-2015, 07:05 PM

almost sounds like someone didnt read my post about S04's being unreasonably narrow in the 275/35/19 size for some reason, bought it and now trying to convince one's self it's the way it should be?

the 285/35/19 S04's i run on my G's 10.5" are

Red__Zed · 07-06-2015, 07:54 PM

Quote:

Originally Posted by MacCool

The basic equation accounts for adhesion as part of the coefficient of friction. Surface area doesn't matter.

Simply not true. What you are describing is the Coulomb model of Physics, not Physics. If you had any background in physics you would know that adhesion and deformation are two of the most standard cases to break you out of the Coulomb model. Your 7th grade Physics equation assumes "hard" solids - it's a terrible approximation of a tire, especially on a performance car, where you are using "sticky" tires and air pressures that allow for a good bit of deformation.

Quote:

Originally Posted by MacCool

The solution, obvious solution, to oversteering or understeering is suspension, not tires. I can't help it if your grasp of rudimentary physics is so lacking that these concepts are beyond your ability to understand. Public education apparently isn't what it used to be.

That's for sure - now they explain the limitations of basic models to junior high students. Go do some research on the adhesion and deformative components - you can find a start on Wikipedia, but any modern Physics textbook will get you up to speed here.

Here's a relevant quote to get you started:

Quote:

When the surfaces are conjoined, Coulomb friction becomes a very poor approximation (for example, adhesive tape resists sliding even when there is no normal force, or a negative normal force). In this case, the frictional force may depend strongly on the area of contact.

Quote:

Originally Posted by Jordo!

Hmm. I was going to suggest a square set up as well, but really in order to keep tire size and compound a constant more than to play with relative grip -- a lot of that will depend on alignment settings and weight distribution/suspension more than anything.

I guess you could buy ultra sticky fronts relative to the rears, but that sounds like it will just make the car unpredictable...

So, assuming equal sized tires of same make, you want to stiffen up the rear relative to the front. That means a beefier rear anti-sway bar and firmer damper settings in the rear and softer in the front, if you can adjust them. Any other bracing you can add to the rear (without adding significant weight) will tend to nudge you more towards oversteer.

I think, maybe a little more camber in the front relative to the rear will help tuck the nose in too... not 100% certain on that one off the top of my head.

Scan over this site for lots and lots of advice on setting up cars for road racing

Autocross to Win (DGs Autocross Secrets) - ATW Home Page

This thread is helpful too

Suspension adjustments and how they affect handling

Points are true in general, but the Z tends to have more issues with stiffness up front (depending on tire selection), and not need a whole lot of help in the rear. The additional camber up front is very important. The Z runs best with 3+* of camber and a bigass bar up front from what I've seen - all the really fast guys have a Hotchkis bar and as much tire as they can get up front, preferably with a stiff sidewall. There's already a ton of stiffness out back on the Z, and a stiffer rear bar doesn't do as much for you.

Rusty · 07-06-2015, 08:20 PM

Here I am of thinking on going with 305's in the front to go with my 345's in the rear in search for more grip.

Now I'm going to have to rethink everything. Maybe I'll start a new trend by going with 145's in the front and 155's in the rear.

ScottOmatic · 07-07-2015, 01:52 AM

As for the roll-bars, its interesting what Red and Rusty are pointing out and what people are saying on the track forum, more front bar and stock or taking out the rear giving more oversteer.

Which goes against the generalized principals but I guess when something is at an extreme value, especially relative to the other end of the car, many theories can go out the window.

I may actually just try to take out the rear ARB and see how that changes the handling dynamics before I get the new tires, I still probably have a couple months before I have to really.

onzedge · 01-06-2016, 11:31 AM

Quote:

Originally Posted by ScottOmatic

As for the roll-bars, its interesting what Red and Rusty are pointing out and what people are saying on the track forum, more front bar and stock or taking out the rear giving more oversteer.

Which goes against the generalized principals but I guess when something is at an extreme value, especially relative to the other end of the car, many theories can go out the window.

I may actually just try to take out the rear ARB and see how that changes the handling dynamics before I get the new tires, I still probably have a couple months before I have to really.

Rusty · 01-06-2016, 02:09 PM

Quote:

Originally Posted by onzedge

EzDz · 01-06-2016, 02:38 PM

You can do everything or one of the many good ideas posted here but after you do take it to a track oriented suspension shop and have it aligned for your square or staggered set up.

07-04-2015, 06:27 PM	#32 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 35,186 Drives: 2011 Nismo GM 6M Rep Power: 2684437	You should read the track section. Everyone is running the stiffest front bars, and the biggest tires they can. Some are running no rear bar at all. kenchan, gomer_110, ScottOmatic and 1 others like this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

07-04-2015, 10:02 PM	#33 (permalink)
Spooler A True Z Fanatic Join Date: Jun 2014 Location: Ga Posts: 13,800 Drives: 2013 Nismo 370z Rep Power: 2684392	Your best savings will be reading and searching. I do quite a bit of that on here. Only spend the money once, will save you a fortune in the future. ScottOmatic likes this.

07-06-2015, 08:20 PM	#39 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 35,186 Drives: 2011 Nismo GM 6M Rep Power: 2684437	Here I am of thinking on going with 305's in the front to go with my 345's in the rear in search for more grip. Now I'm going to have to rethink everything. Maybe I'll start a new trend by going with 145's in the front and 155's in the rear. ScottOmatic, Spooler, Memphis370Z and 1 others like this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

01-06-2016, 02:38 PM	#43 (permalink)
EzDz Enthusiast Member Join Date: Aug 2015 Location: Pittsburgh Posts: 309 Drives: 2016 370z Nismo Tech Rep Power: 10	You can do everything or one of the many good ideas posted here but after you do take it to a track oriented suspension shop and have it aligned for your square or staggered set up. __________________ Nismo \| Moore Performance \| AAM \| Tein \| PPE \| Tomei \| Eibach \| Z1 Sponsored: Mishimoto

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07-06-2015, 07:05 PM	#37 (permalink)
kenchan A True Z Fanatic Join Date: Aug 2009 Location: N/A Posts: 76,801 Drives: N/A Rep Power: 141521	almost sounds like someone didnt read my post about S04's being unreasonably narrow in the 275/35/19 size for some reason, bought it and now trying to convince one's self it's the way it should be? the 285/35/19 S04's i run on my G's 10.5" are

07-07-2015, 01:52 AM	#40 (permalink)
ScottOmatic Base Member Join Date: Jun 2013 Location: Madison, WI Posts: 63 Drives: '88 Porsche 928 S4 Rep Power: 12	As for the roll-bars, its interesting what Red and Rusty are pointing out and what people are saying on the track forum, more front bar and stock or taking out the rear giving more oversteer. Which goes against the generalized principals but I guess when something is at an extreme value, especially relative to the other end of the car, many theories can go out the window. I may actually just try to take out the rear ARB and see how that changes the handling dynamics before I get the new tires, I still probably have a couple months before I have to really.