I know what the numbers stand for...example: 265 - width of tire/35 - sidewall height/19 - wheel size...

How does each change affect handling though? A wider tire would make you handle worse or better? A taller sidewall would affect what? Understand what I am asking?

--Brandon (trying to understand suspension and braking a little more)

 

My answer from the other forum

Here are some quick points, some obvious:

Increasing the front width or decreasing the front to rear difference will decrease the understeer, adding some swaybars in addition will probably turn it inot oversteer.
Also going too wide in the front will affect driveability as they will follow any imperfection on the road.

Increasing width in the rear will obviously add traction, as for how wide you can go depend on the wheel width, I have seen 305's you just have to get the right width and offset.

As for profile as mentioned the taller the tire the smoother the ride but also the softer the handling as the sidewall is more likely to flex on hard turns and not feel solid.

I would go with 18's as the 19's will rob you of performance, the majority of the weight of the wheel will be an inch further out, so unless you go with a TT and add a lot of more power you will notice the difference.

 

Thanks Gus.

I'm planning on 550, 650, and 750 (diff. boost levels with different octane rating gasoline) so I am going to go with 19's. (since you said it won't make too much of a difference with a tt kit)

So 235/35/17 in the front....and 275/40/17 in the rear for the stock wheels?
And 245/35/19 in the front....and 295 or 305/40/19 in the rear for the aftermarket wheels?

The aftermarket wheels i'm looking at are Volk Racing TE37's and SSR GT-3's. And should I go with 8.5 in the front and 10.5 in the rear?

 

Ok, only dealing with tires...

You want different tire sizes based on what you are trying to accomplish. If you look at a 'funny-car' drag racer, they have giant tires in the back, and bicycle tires on the front. Since they don't really have to turn, lighter fronts are better. But, since you and I want to be able to make that U-turn, you need bigger tires on the front (well, wider than those bike tires).

It's all about ratios. The wider the fronts are compared to the rears, the easier it is to turn. But... you don't want it to get twitchy, because curbs are not your friend.

The wider your rears, the more likely you are to go in a straight line, and the more acceleration traction you have, but the harder it is to turn.

If you have lots of power, you need big rears to get it to the ground. Small tires will spin (more) easily. If they spin while you are taking a fast turn, your rear completely loses traction and your car spins around, too.

So, wider = more grip on that end (except in rain, when wider may/can = hydroplane, ie surfboard).

Stock, the 350Z is a bit wider at the rear (225 front, 245 rear). This will mean better traction in the rear, so you will have good straight line traction, but tend to 'plow' in a turn. Not badly, just a bit. This is generally safer than the opposite (old Porsche 911's can get real twitchy because of all the weight in the back. Notice the newer models have very wide rears?); most production cars have this tendency built in.

Lots of people like putting bigger tires and/or wheels on their car. Wheels bigger than 17in are mostly for show, and they get much more expensive. The advantage to bigger wheels is a bigger contact patch front to back (think wagon wheels), and slower wheel speeds at faster car speeds.

The downside is, the bigger the wheel, the heavier it gets. And even worse, the farther away from the hub that weight is. Physics says, the farther from the hub your weight gets, the harder it is to spin it. So a 20 pound 14" wheel is going to be easier to spin than a 20 pound 17" wheel. And, the more energy you spend spinning your tires, the less energy you have to accelerate your car.

So what do you want? If you want to drag race, get big rears. If you want to autocross, probably getting the same size (245-ish) all around is better. If you just want to look good, get 20" chromed wheels. But if you get spinners we will have to hurt you.

 

Second part (still just tires)...

The /35 is another ratio; 35 means "35% of 265, measured from the rim to the tread"

So, the bigger this second number, the taller the tire will look compared to the wheel.

Old style tires, ie 185/70 R14 from your old 1975 Buick, are really "tall."
Taller tires soak up more bumps from the road, and therefore give you a comfy ride. Mmmm, Buick, squishy tires, squishy springs, squishy shocks... it's just like a waterbed...

But, in a hard turn, the sidewall can flex, and that makes your handling sloppy. So, all other things equal, the shorter the sidewall, the less flex, the sharper/crisper/more precise your handling.

Up to a point.

Somewhere on here, knowlegeable people were saying that less than /50 doesn't really make much difference. Also, really short sidewalls + potholes = bent rims. The tire takes up a LOT of bumps, so the less tire you have, the more work your suspension has to do. Which is good and bad, because it's much easier to control what your suspension is doing than your tires.

 

Damn! Very nice, exactly what I was looking for. I figured there had to be a negative to doing a different size (depending on which part of the tire size you are changing).

So it seems like there is a medium...going with a smaller sidewall will improve handling but decrease ride comfort, going with a taller sidewall will improve ride comfort but decrease handling. So 30-40 seems like a good sidewall.

The wider the rear tire, the more grip, the worse it will handle. The smaller the width, the better the handling, the less grip. So 295 should be good for the rear tire. (I would go with 305 but when I do go on the track...it won't handle very well) The more skinny the front tire, the better it will handle, the less traction it will have, so 245/255 should be good for the front tire.

Thanks...

 

what kind of horsepower are you putting down?

/30 is actually very small; be real careful when it comes to potholes. the /45 on the stock tires is a pretty good performance height. Keep in mind, a pretty typical sedan is running /60 or /65, and trucks are often /70 to /80. With a /30, you pretty much have Wheel, Bead of rubber, Tread. I don't know that you can even get lower than /30.

In any case, have fun. And get the best damn tires you can find. Skimping on tires is like taking steroids; yeah, you have the biceps to get the chicks, but what's the point if you can't get it up? (or keep it on the road)

 

I'm planning on 3 boost settings, 550rwhp for daily driving (93 octane), 650rwhp for whenever (93 octane), and 750rwhp for the drag track
(race gas) (going to use slicks there though).

We don't have hardly any potholes here.

I'm going to use either Goodyear Eagle F1's or Toyo T1-S'....I haven't found the tire sizes for the aftermarket wheels yet...but I know they will fit the stock (245/35/17 and 275/40/17). I'm also considering Michelin Pilot Sports and a few other tires.