How wide tires affect overall performance
 

Just a quick question here.

I will be mounting my new GS4 soon after my OEM tires wear out, 22k miles and still have maybe 30% left.

thinking about going with Bridgestone Potenza RE-11 with 265/35 front and 305/30 on the rear.

The GS4 will already be adding weight (comparing to the stock 18") so i am not sure how the wide tire specs will affect the overall performance. anyone have any ideas?

the Z is my dd and i do not track it, for now anyways. But i do take a canyon road to work so there are a lot of corners and curves.

any other recommendations will be greatly appreciated.

Certainly it would improve the handling with the 305's on the rear. The principle behind that is the more/wider contact with road makes you more stable on the curve. I do recommend have your camber at -2 at the rear.
It does make your tire wear uneven though but it is what it is...you could not get both worlds in life either.

The down side you sacrifice acceleration as you spin a heavier mass with the 305.

I don't care as you said you don't race the car in the track and dd it on the mountains the 305 is just perfect! I love mine!:tup:

MAybe you sacrifice acceleration, maybe not. If you can apply more throttle without spinning the tires, you're going to accelerate faster.

Wider tires will improve your handling in the dry. In rain or snow, it will hurt handling. A 305 may be overkill unless you're putting down serious power.

[QUOTE=Chuck33079;2503801] In rain or snow, it will hurt handling. QUOTE]

Could you maybe elaborate on that, im just curious as to how it hurts your handling.

With snow tires you want a smaller footprint because that means the tires have to displace less snow. Hence, snow tires are typically quite narrow. A wide tire with a larger footprint has more to displace, which means the more snow, the more likely you are to loose traction.

The same applies to standing water. A wider tire is more likely to hydroplane.

:iagree:

I love my setup: 275 front and 305 rear. Track day was amazing and DD is great too. I run -1.2 rear camber though for better tire wear and performance has not suffered at all.

Generally Speaking OP:

TOO wide front tire = More Understeer
TOO wide rear = no such thing

*Note: There is such thing as having a tire too wide for the wheel also

Sure there is. It's a tradeoff between width and tire weight and rolling resistance. And your front/rear explanation just describes putting a wider tire on one end of the car. If you go wider on both front and rear in the same amount, there will be very little change in the car's balance between understeer and oversteer.

And now i learned something :tup:

Innnnnteresting...

http://dealbreaker.com/images/entrie...anke%20nyt.jpg

if you're just streeting the car, just use stock size. maybe go 285/35/19 on the rear which is nismo size.

otherwise it's really overkill imho and just weights down the car.

quality stock size tires > cheap wide tires

Hey, hey!!! First of all :gtfo2:

I'm ordering my 305's today!



I want 305's because they look SEXXXY
Apples to apples, the Michelin PSS weighs 27lbs as a 275, 28lbs for a 285, and 30 lbs for a 305. Those are some of the lightest tires you can find.

RE-11's are 31lbs for the 285 and 32lbs for the 305's

So not a WHOLE hell of a lot depending on which compound you want to stick to (no pun intended) and the tires get lighter over time! Lol
Lastly, 305/30-19's are 1.3% shorter than 275/35's so the added weight might mean a hair less because now you've geared up the car

This is a good enough reason.

whut? :happydance:

http://www.the370z.com/members/wheee...-30-19-v12.jpg

As Chuck pointed out it is not as simple as all that. For example, for the stock Nismo sizes at 245 front and 285 rear there is a 40mm stagger. This results in the car driving like a plow under certain conditions (understeer). If you keep the rear the same size and put a wider front tire compared to stock on the front, it will not increase understeer. It will actually bring the car closer to neutral and reduce understeer. The larger front tire creates more grip allowing the car to turn instead of going straight while you're turning.

Conversely, if you simply increased the rear size and left the front alone you would be increasing understeer.

Personally, I went to a 285 front and 305 rear combination. I still have mild understeer that can easily switch to power oversteer. I do plan on going to a 305 square setup to get to neutral and so I can rotate my tires.

Wouldn't an overly wide front increase oversteer?

Yes, too wide on either end will make the other end grip less respectively. Too wide in back, understeer. Too wide in front, oversteer.

Interesting... my 305 rear and front 275's seem to be perfect balance right now. My camber in the front is -1.6 and the rear is -1.2.... on the track it seems to be extremely nimble but no loss of 'balance'. I noticed neither understeer or oversteer throughout the roadcourse.

You maintained the stock stagger. 245 to 275= 30mm, 275 to 305=30mm.

I'm gonna not go stock stagger and get 245 and 305. I'll take the risk of understeer

245's are on clearance, and 305's are on clearance as well... Lol

A 60mm stagger...ouch. You won't be oversteering, you'll have serious understeer.

Your fronts will have a lot less grip compared to the rear. Meaning if you go into a corner hot, your rears will handle it and not step out. Your fronts won't have enough traction to change direction and instead of turning, they will go straighter than you'd like. With a RWD, you can always give it a bit of power to reduce the traction to the rear and try and get some power induced oversteer though.

Or set the rear sway to full stiff to at least help out some.

Thanks a lot for all the input, i do not wanna quote and reply to individual posts with my phone so i will do that when i am at home.

My bad! Meant under steer! Lol

My current bars aren't adjustable, but if I find it to be too much, I'll spring for an adjustable or stiffer rear bar

I'm new to sway bar settings myself. So could you explain how stiffening the rear sway bar will help with too much grip in the rear already? I was under the impression that stiffer = kept the tires planted more = more grip.

Secondly, wouldn't he want to work on increasing the front grip instead of reducing the rear grip? Which would negate any benefit the 305's would of given him and simply reduce overall traction?

You get different data/input from different sources.


The GENERAL rule is:
Increase front bar stiffness, increase understeer.
Increase rear bar stiffness, increase oversteer.
I think the thinking is weight transfer/balance in turns?

The track guys, IIRC, say that you need more front bar for better traction/oversteer though.


All I know is that it's a balancing act and too much/too little of either bar plays different roles depending on what kind of driving you're going to be doing.



My input, for me, 99.9% of my driving is very aggressive street driving, so I got the Nismo S-Tune bars, because I assume they know what they're doing a bit, and they are making a stiffness setting for the masses, which I fall into.

I tried looking online, and you're right I'm getting a lot of conflicting information. The bottom line was "it depends" and its all about balance. Increased stiffness may increase grip, but then again going too far reduces it. The best I understand it now is thus: (if someone understands it better please correct me if I'm wrong)

The front is looser than the rear under that scenario. Which means the front rolls a bit more, and since the rear doesn't roll it has to slide. So it's all about the balance of the two.

I'd still think that softening the front relative to the rear would be the way to increase overall traction. I.e. upgrade both front and rear, but put rear on stiffer and the front on softer. So both bars are stiffer than stock, but the rear increases stiffness more than the front.

Suspension is confusing...

Will 305s on Rays clear without camber if I'm running 25mm spacers?

I's confuzed too...


That's why I took the crappy lazy way out, lol

This is the reason I like this forum so many smarty pants! Very informative! Thank you much!
Guys Op said he doesn't track the car so what the fuss...as long you enjoy your Z and like how it looks it doesn't matter! We still love you because your nuts about the Z.:tup:

I kinda doubt it.

I have a 20mm which I might have to remove or make 15mm (I'm also going to remove most my camber with a camber kit)

If you go 245/305, it'll be interesting to get adjustable front camber arms and dial in a little more negative camber to increase efficiency of the front tires during cornering, offset the "plow" that the huge stagger will cause

member Nismo09 runs the SPL front arms, he dialed in lots more negative camber and he's on stock nismo setup (40mm stagger), and the steering has come to life quite a bit

It just like folks have stated it all depends, if you track add camber and you can't get stiff enough in the front, but if you daily drive and want run camber for looks a spirited driving, you are going to need a fund for tire replacement. I have 305s rear and 265s up front. I bought rear camber arms and toe bolts so that I could run them at factory settings. There is under steer, but grip is much better over all. I'm running SO-4s.

Most auto x guys run no rear and a hard front. Doran runs a huge front! I now have a stock rear and whiteline front set to full hardness. It feels fine but still lots of body roll! Dare I say feels like more body roll than stock? But stock alignment blows and left to rights are off 0.5* on both so no report till I finish what I want.

The bigger the difference in front and rear tire widths, the more the car will understeer. Car manufacturers started using staggered tire sizes on sports cars mainly for safety reasons. Of course, there's also the extra grip advantage.

What would you recommend for a street tire for both looks and performance? Wheels are 19x9 +15, 19x10.5+15, might lower with swift spring in the near future

i know i cant have best of both worlds but i am more than willing to balance them out.

I was worry about 305s weighing down the car, especially with the added weight of the wheels.

by no means i am looking for cheap tires, but i want something that will look good but wont affect daily driving

The forum consensus is RE-11s or Michelin PSS. Weight is going to vary depending on the tire.

For strict DD-ing, you want PSS.

And PSS's are LIGHT. The lightest tire I have seen in any/every size

PSS is going to be my next set, unless Dunlop makes their star spec replacement in the right sizes. Star specs were awesome.

It's going to be a while, since I just picked up a set of Nismo wheels with fresh OEM rubber.