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Bmsluite
Bmsluite New Reader
3/1/22 9:05 a.m.

I am opening up this discussion as I would like to learn more and I am sure some of you guys know A LOT.  I would like to know what you know factually and subjectively.

As far as I understrand contact patch of the tire it is firstly based off of the width and the height of the tire.  The wider the tire is the more lateral grip you get while also increasing to a smaller amount the straight line acceleration/braking grip.  The taller a tire is the longer the tire patch so you get better acceleration/braking grip and to a smaller extent some more lateral grip.  

The next is tire pressure which is based off of weight.  Generally the lower the the tire pressure the greatest the contact patch.

Now, as far as tire stagger goes we are going to discuss what I believe is a prime example of tire stagger and its effect on a vehicles performance on track.  My car is a RWD 350Z that weights 3250 lbs. and has 300 WHP. 

I understand that having a greater tire stagger inscreases understeer but is that the whole story?  I see most people go square and claim they end up with a more nuetral handling car.  I personally have always run a staggered setup.  I feel like the weight shift of the car, and especially my cars, shift more weight on the rear than the front.  Meaning I have more weight transfer in the back compared to the front.  This gives me more contact patch between BOTH front tires compared to the contact patch of BOTH rear tires.  

I also know there is conception of needing more rubber in the rear due to the car using those tires to both accelerate the car AND turn the car.

From these conceptions we can assume that a staggered setup is best performance wise.

Are these conceptions valid?  Is a staggered tire setup better?  From what I can tell a taller and wider rear tire compared to the front should be optimal.  Of course, you could add the same size rear tire but I am sure there is diminishing returns at some point when the weight of the bigger tires/rims ends up negating the performance of the vehicle.

When it comes to vehicle balance does the amount of stagger matter or does the actual ratio matter?  To clarify:  a 255 front and a 255 rear is a 1:1 ratio.  A 255 front and a 265 rear is a 1:1.04 ratio.  A 255 front a 315 rear is a huge 1:24 ratio.

This is open to any and all opinions on any of this.

Thanks

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) SuperDork
3/1/22 9:39 a.m.

The sad fact is that to keep the average person safe most production cars understeer excessively.  This is why a lot of people adopt a "square" setup.  It makes a big change in front / rear grip.  It also allows for tire rotation to equalize wear.  
 

Taller tires also have bigger contact patches.  The larger diameter puts more rubber on the road too.  That bigger outer diameter is closer to flat compared to a smaller diameter.  
 

 

dps214
dps214 Dork
3/1/22 10:03 a.m.
AnthonyGS (Forum Supporter) said:

Taller tires also have bigger contact patches.  The larger diameter puts more rubber on the road too.  That bigger outer diameter is closer to flat compared to a smaller diameter.  

Not without other things changing. Contact patch is just vehicle weight divided by pressure. Same pressure, same total contact area. Diameter changes might result in the shape of the contact patch changing, but not the size of it. What it does probably do is reduce rolling resistance, because the tire has to deform less to achieve the same flat area.

Keith Tanner
Keith Tanner MegaDork
3/1/22 10:20 a.m.

In reply to dps214 :

That's assuming a tire with no structure. In reality, the steel belts inside make the contact patch far less reliant on pure air pressure than you'd think. It's a fun experiment to put some paint on a tire and drop the car on to a sheet of paper and see how much the footprint changes with pressure. A lot less than it "should".

I like a square setup with my cars because I don't like handicapping the tires that do the braking and steering. The exception would probably be a car with radically unbalanced static weight, like a 911 or an F1 car. A 350Z should be pretty close to 50:50 with a slight front bias so there's no reason to put big fat tires on the back only.

classicJackets (FS)
classicJackets (FS) SuperDork
3/1/22 10:26 a.m.
Keith Tanner said:

In reply to dps214 :

That's assuming a tire with no structure. In reality, the steel belts inside make the contact patch far less reliant on pure air pressure than you'd think. It's a fun experiment to put some paint on a tire and drop the car on to a sheet of paper and see how much the footprint changes with pressure. A lot less than it "should".

Keith is exactly right. The Experiment he described is called a "footprint," and combined with other testing data and some good software allows for prediction about quite a few characteristics of a tire and it's performance. Tires are wildly, wildly, complicated, and you will absolutely see 2 different footprints between 2 tires of the same size, especially if one is a performance tire and another is all season. 

Source: worked in tires for an OE.

buzzboy
buzzboy SuperDork
3/1/22 10:44 a.m.

My winter car has no stagger because of 4wd.

My fun car has no stagger because I don't like the way it looks.

My race car has no stagger because I rotate my fronts to the rear.

codrus (Forum Supporter)
codrus (Forum Supporter) PowerDork
3/1/22 10:45 a.m.

Aside from promoting understeer for safety, the other big reason why many street cars have staggered tires is to look cool.  This is especially true on muscle/pony cars because of the association with drag racing.

For big pro-level road race cars my impression is that in an ideal world you'd want to have the same size tires at both ends but you just run out of space in the front because of the need for steering.  Beyond that point there are still gains to be had by going wider rear-only, it may not be ideal but it's still better than a square setup that's limited by the front.

 

gearheadE30
gearheadE30 Dork
3/1/22 11:06 a.m.

I would think stagger has a place in front wheel drive cars, or maybe AWD for that matter. Take this pinnacle of modern performance: the Grand Prix GXP. Plenty of power, front wheel drive, long wheelbase, heavy car. The "reverse" stagger with wider front tires (255 fronts and 225 rears, I believe) makes sense to me because the rear tires aren't really doing all that much in terms of braking and there is only so much you want to do with sway bar sizing and such for ride quality in a street production sedan.

I really don't see much benefit for performance use for RWD cars, except the drag racing example. I can't think of a reason why you would purposefully want the front tires to have less grip.

Javelin
Javelin MegaDork
3/1/22 11:18 a.m.

When I was drag racing cars I had staggered tires because the fronts needed less rolling resistance and the rears needed more traction. Once I got into autocross and track days a square setup worked better for chassis balance, steering, and tire life.

The exception I own today is the Boxster, which since it is mid-engine, has a heavy rear weight bias. The chassis and suspension are designed for a stagger and it works very well. The car is sensitive to less grip on the rear but doesn't seem to care much about fronts. I went up 20mm on the fronts and actually had worse handling with the same tire, so back to stock size I went.

TurnerX19
TurnerX19 UltraDork
3/1/22 11:30 a.m.

I have never called the front to rear tire size differential "stagger". The term "stagger" is a circle track term used on one end of a car to influence its cornering, usually larger on the right side.

Gearheadotaku (Forum Supporter)
Gearheadotaku (Forum Supporter) UltimaDork
3/1/22 11:47 a.m.

The Audi RS3 has an option for larger tires on the front than the back, even though it's AWD.

frenchyd
frenchyd MegaDork
3/1/22 12:04 p.m.
Keith Tanner said:

In reply to dps214 :

That's assuming a tire with no structure. In reality, the steel belts inside make the contact patch far less reliant on pure air pressure than you'd think. It's a fun experiment to put some paint on a tire and drop the car on to a sheet of paper and see how much the footprint changes with pressure. A lot less than it "should".

I like a square setup with my cars because I don't like handicapping the tires that do the braking and steering. The exception would probably be a car with radically unbalanced static weight, like a 911 or an F1 car. A 350Z should be pretty close to 50:50 with a slight front bias so there's no reason to put big fat tires on the back only.

I've never found two tires that are exactly the same.    So I put my car on the scales and see what each corner weighs.  At identical tire pressure. 
  Running a square set up I can move tires to where they give me the best  corner weights.  
      Classical example is dirt track sprint cars. The right rear is going to be the tallest tire and the left front the shortest.  
 That causes the car to naturally turn to the left.  
  Reverse that for road racing and the car will want to turn right.  Typically a road course will have 4 right hand corners and some other number of left hand corners.
   You may find that a left hand corner is more important  so you reverse stagger for that. 
 In other words read the track  and scale the car.  

Javelin
Javelin MegaDork
3/1/22 12:05 p.m.
Gearheadotaku (Forum Supporter) said:

The Audi RS3 has an option for larger tires on the front than the back, even though it's AWD.

It's not full time AWD and only like 30% of the power max can go to the back.

ProDarwin
ProDarwin MegaDork
3/1/22 12:07 p.m.

There are certainly setups where stagger is faster, but 99% of those I have seen are on high powered SMF cars.

Duke
Duke MegaDork
3/1/22 12:08 p.m.
TurnerX19 said:

I have never called the front to rear tire size differential "stagger". The term "stagger" is a circle track term used on one end of a car to influence its cornering, usually larger on the right side.

While you are technically correct, the rest of the world has adopted the term to mean differing wheel or tire sizes from front to back as well.

My favorite was the shortlived trend among the streeeet tunerz crowd to put wider wheels/tires on the back of relatively stock FWD cars just so they could show more dish in the rear.

When I had my Neon ACR I ran 195s on the front and 175s on the back.  It made for a great handling little car.

For RWD / AWD cars I prefer a square setup for all the reasons mentioned above.  I don't own a 911 or anything making massive power, though, and probably never will.

 

Tom1200
Tom1200 UltraDork
3/1/22 12:16 p.m.

I had to look it up but some sources refer to a non-square set up as stagger. Like TurnerX19 I think of stagger as taller tires side to side.

On all of my cars I run a square set up.  I've driven very few cars that have enough power to warrant larger rear tires.

My F500 is supposed to used smaller fronts for road racing. I autocross and road race it so I use a square set up. As these cars don't have a differential you need the wider front tires to combat understeer in relatively low speed tight radius corners seen at autocross. By doing this I'm giving up some time on road course; there is the higher rolling resistance and due to the open wheels the aero drag created by the wider tire. As I am the only one vintage racing an F500 it's worth the trade off as I only need one set of tires.

Javelin brings up a couple of primary considerations; like rolling resistance and what was the car designed for.

Even beyond the square set up I run the smallest size tires possible; this is peculiar to the low power cars I run. Wider tires mean more rolling resistance and weight. On my Showroom Stock Miata it was actually faster to run 185s, about 2-3 tenths per lap BUT the 185s would start to get greasy at the end of a race and couldn't maintain that pace for more than 3-5 laps . I would qualify on 185s and then race on 195s.

Another consideration is the wider tire & wheel represents more unsprung weight which will have an effect on dampers; this effect may or may not be noticeable.

For street cars; unless they are not designed for it I always run a square set up purely for convenience. I also run the smallest size possible on a street car because it's usually worth 2-3 mpg. Note my street cars are typically not sports cars.

Keith Tanner
Keith Tanner MegaDork
3/1/22 12:27 p.m.

The E39 M5 came with staggered tires and wheels from the factory. The hot setup is to square it up with a second set of rears. Which is why it is completely impossible to find a replacement rear wheel for those cars :)

Driven5
Driven5 UberDork
3/1/22 12:45 p.m.

I learned it that stagger simply refers to a difference in tire size. Depending on context that can be width, circumference, or even both.

I also learned it that the starting point for width stagger is generally based on steady state cornering, by having the f/r tire width % roughly matches the f/r weight %. So at the same weight and total tire width a 50/50 car might run 255 square, while a 45/55 car might run 275/235. Then perhaps add some primary drive axle tire % as the car becomes less power limited and more traction limited. Of course there are chassis limitations, and/or other practical considerations, that may prevent or alter this as well. Ultimately, the suspension can also be tuned to help compensate for less than 'ideal' stagger.

GameboyRMH
GameboyRMH MegaDork
3/1/22 1:15 p.m.

I stick to square setups because maintenance/rotation is so much easier. There's one less tire (and generally, wheel) size I'll ever need to store this way. The only good reasons to run a "staggered" setup IMO are to squeeze the last bit of performance out of a car, or to get a second spare for OLOA.

L5wolvesf
L5wolvesf HalfDork
3/1/22 2:09 p.m.
TurnerX19 said:

I have never called the front to rear tire size differential "stagger". The term "stagger" is a circle track term used on one end of a car to influence its cornering, usually larger on the right side.

Thank you

dps214
dps214 Dork
3/1/22 2:30 p.m.
Javelin said:

When I was drag racing cars I had staggered tires because the fronts needed less rolling resistance and the rears needed more traction. Once I got into autocross and track days a square setup worked better for chassis balance, steering, and tire life.

The exception I own today is the Boxster, which since it is mid-engine, has a heavy rear weight bias. The chassis and suspension are designed for a stagger and it works very well. The car is sensitive to less grip on the rear but doesn't seem to care much about fronts. I went up 20mm on the fronts and actually had worse handling with the same tire, so back to stock size I went.

I don't know, 245s on 9" wheels all around on my base 986 was pretty fantastic other than looking pretty silly. Not sure exactly how much of a difference it made but it certainly ws doing something to make up for the front being limited to .5* camber. But I think a big part of that was the car being underpowered enough that the rear end couldn't help rotate the car through the corner and the front tires were doing all the work. Add power and the need for massive front grip goes away.

Having now had a lot of experience driving various mid/rear engine porsches with reasonable power, I think the conclusion that I've come to is that more front tire alone doesn't really increase the performance potential but makes the car a bit easier/more forgiving to drive, at the expense of some feel/tire wear.

Javelin
Javelin MegaDork
3/1/22 2:43 p.m.
dps214 said:
Javelin said:

When I was drag racing cars I had staggered tires because the fronts needed less rolling resistance and the rears needed more traction. Once I got into autocross and track days a square setup worked better for chassis balance, steering, and tire life.

The exception I own today is the Boxster, which since it is mid-engine, has a heavy rear weight bias. The chassis and suspension are designed for a stagger and it works very well. The car is sensitive to less grip on the rear but doesn't seem to care much about fronts. I went up 20mm on the fronts and actually had worse handling with the same tire, so back to stock size I went.

I don't know, 245s on 9" wheels all around on my base 986 was pretty fantastic other than looking pretty silly. Not sure exactly how much of a difference it made but it certainly ws doing something to make up for the front being limited to .5* camber. But I think a big part of that was the car being underpowered enough that the rear end couldn't help rotate the car through the corner and the front tires were doing all the work. Add power and the need for massive front grip goes away.

Having now had a lot of experience driving various mid/rear engine porsches with reasonable power, I think the conclusion that I've come to is that more front tire alone doesn't really increase the performance potential but makes the car a bit easier/more forgiving to drive, at the expense of some feel/tire wear.

Mine is a Boxster S which is a pretty significant step up powerwise with the 3.2 to the 2.5 non-S (also different gear ratios with the 6-speed manual). Stock front is 235 on a 18x8.5 (with 265's on an 18x10 rear). The 914 1.7 (even as hot-rodded as it was) that I autocrossed significantly was a square setup.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) SuperDork
3/1/22 5:00 p.m.
dps214 said:
AnthonyGS (Forum Supporter) said:

Taller tires also have bigger contact patches.  The larger diameter puts more rubber on the road too.  That bigger outer diameter is closer to flat compared to a smaller diameter.  

Not without other things changing. Contact patch is just vehicle weight divided by pressure. Same pressure, same total contact area. Diameter changes might result in the shape of the contact patch changing, but not the size of it. What it does probably do is reduce rolling resistance, because the tire has to deform less to achieve the same flat area.

Amazing.....  okay let's say the universe is an infinite plane.  Let's smash Pluto down on that plane.  Now smash Jupiter onto that plane and tell me which one makes more contact.  

Yes there are other factors, but diameter is one of them.  
 

 

GameboyRMH
GameboyRMH MegaDork
3/1/22 5:21 p.m.
AnthonyGS (Forum Supporter) said:
dps214 said:
AnthonyGS (Forum Supporter) said:

Taller tires also have bigger contact patches.  The larger diameter puts more rubber on the road too.  That bigger outer diameter is closer to flat compared to a smaller diameter.  

Not without other things changing. Contact patch is just vehicle weight divided by pressure. Same pressure, same total contact area. Diameter changes might result in the shape of the contact patch changing, but not the size of it. What it does probably do is reduce rolling resistance, because the tire has to deform less to achieve the same flat area.

Amazing.....  okay let's say the universe is an infinite plane.  Let's smash Pluto down on that plane.  Now smash Jupiter onto that plane and tell me which one makes more contact.  

Yes there are other factors, but diameter is one of them. 

May sound counterintuitive, but it's true, it's about weight vs. stiffness. Consider this: If the plane and the two planets were all infinitely hard objects, both planets would make an infinitely small contact area with the plane - practically zero, regardless of their weight. If Pluto was made of mattress foam it would deform and would have a much larger contact area than the infinitely-hard Jupiter. That's an extreme example but the same applies to tires, and if tire construction and pressure are the same, and the vehicle weight is the same, a 315-wide tire on a 19" wheel will put the same area of rubber on the road as a 13" pizza cutter. They're both supporting the same weight with the same stiffness (tire carcass is a factor here), so they'll both deform to press the same area of rubber onto the ground. What would give more grip in that scenario would be spreading out the contact patch shape to a wider and thinner contact patch (Think of the 315-wide tire having a contact patch shaped like a ruler vs. the pizza cutter having one shaped like a CD minus the hole...even though the area of both contact patches are equal)

dps214
dps214 Dork
3/1/22 6:05 p.m.
AnthonyGS (Forum Supporter) said:
dps214 said:
AnthonyGS (Forum Supporter) said:

Taller tires also have bigger contact patches.  The larger diameter puts more rubber on the road too.  That bigger outer diameter is closer to flat compared to a smaller diameter.  

Not without other things changing. Contact patch is just vehicle weight divided by pressure. Same pressure, same total contact area. Diameter changes might result in the shape of the contact patch changing, but not the size of it. What it does probably do is reduce rolling resistance, because the tire has to deform less to achieve the same flat area.

Amazing.....  okay let's say the universe is an infinite plane.  Let's smash Pluto down on that plane.  Now smash Jupiter onto that plane and tell me which one makes more contact.  

Yes there are other factors, but diameter is one of them.  

Jupiter, because it's heavier, regardless of its shape. But I'm not sure how that's relevant to a discussion of same weight, same internal pressure, different diameter.

Keith is right that in the specific case of tires there's enough going on that it's probably not that simple. But in the hypothetical example of rigid objects, it literally is just p=f/a.

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