Which wheel spins first?

[Xaendeau]

These were from my Miata. The Fiesta will likely wear the outer edge pretty hard. Tips to consider:
Check your pressures
Chalk your side walls to check for roll over.
Spray not only the tires down but the insides of the wheels as well.
Also a little negative camber will help.

I need more negative camber in my life, tears up the inner shoulder with street driving though.

 

[Xaendeau]

Or if the performance aspect isn’t that big of a deal then have the fifth tire an asymmetrical. Just crazy.

I prefer to have directional tires. I usually wear down one outside tread-block shoulder before the rest of the wheel. Local tire shop will flip two tires on the wheel for a bucket of chicken. You take the rears, flip them, then put them on the front.

https://www.tirerack.com/images/tires/tiretech/tire_rotation_fg.png

Remounting two tires is cheaper than changing my oil, and I do that every time I track the car. 0W-40 or 5W-40 is somewhat expensive.

Do realize that we have two drivers, my Fiance and I, for autocross events. We do twice as many laps as everyone else per event, and might do a few suspension "testing" laps if people feel like sticking around afterwards. For fixing one particularly rough tire, I just go front to back without flipping until the 4 match the tread depth of the beat up tire.

 

[FiestaAlex]

They spin at the same time if you're in a straight line.

Hi fellow Alex. This is also my first post on this forum although I've lurked for a while.

This is not entirely true - rarely true, I should say. Very rarely. Here is why:

Horsepower will choose the path of least resistance. If resistance is the same from left to right, it will spin both of them.

This is true. Whichever wheel has the LEAST traction will spin. This is why open diffs suck. The amount of traction between both wheels has to be EXACTLY the same for both to spin and this is very rarely seen in nature. Just the weight difference between each corner will be enough to upset this balance for one wheel to slip first, and then you're doing the "one tire fire" - try it some time. Do a burnout. You won't leave two stripes. You'll leave one. Because as soon as one wheel slips just a bit, that's your path of least resistance and all the power goes there.

Having a driver with no passenger will create enough difference. Having a weight difference between passenger and driver, will do it too. Having the car on a slight slope - same thing (most roads are banked so rain will drain off the side, even if the road is "perfectly level" by every other measure). I'm also fairly certain that if you corner balance our cars in stock form with nobody inside there will be a weight difference between the front wheels just because the battery is one one side and so forth.

Now add the fact that the road contains variable amounts of loose dirt/sand on top and pebbles every few square feet, tires wear unevenly, and a dozen other random variables and it's easy to see why open diffs leave one stripe 99% of the time when you punch it. Due to the mechanical differences in the trans-axle, one tire may break loose more often than another - difference in half-shaft length, internal mechanics of differential, condition of wheel bearings, etc. But it isn't ALWAYS the left or the right, that depends more on the balance of available traction at that moment, between those two contact patches.

I won't even mention one wheel being in a puddle, or on a road marking - that's just too obvious. Oops, I guess I just mentioned it

You're thinking too hard as far as rotation. Just do a diagonal rotation then a front-rear rotation and then diagonal, and so on.

Agree 100%, just rotate the suckers and call it a day.

 

[FiestaAlex]

I would like to set up an experiment actually, and do a series of small burnouts. Even though it'll probably never be both wheels, my guess is there will be one side that comes out a winner either due to weight or some mechanical discrepancy in the trans-axle. Maybe I'll save it for the day before I get new tires. Maybe someone else here wants to do it and post their results?

 

[alexrex20]

Hi fellow Alex. This is also my first post on this forum although I've lurked for a while.

This is not entirely true - rarely true, I should say. Very rarely. Here is why:

I guess you've never launched your Fiesta ST from a red light. It spins both tires. Whether you choose to believe it or not, it will spin both tires.

 

[TyphoonFiST]

Someone get a video and settle all this Ballyhoo! Just in an "enclosed setting"!

 

[FiestaAlex]

I guess you've never launched your Fiesta ST from a red light. It spins both tires. Whether you choose to believe it or not, it will spin both tires.

I'm not sure why that would be your guess. Really makes no sense actually. Do you really think I've never punched it from a light?

More importantly, how do you know it spins both tires, while driving the car?

Quick google:

Pause it around 16s - you clearly see one skid mark. Just as you'd expect from an open diff...

https://www.youtube.com/watch?v=Y00-OvAcJ58

I'm honestly puzzled why you'd expect anything else. Is it the torque vectoring brake witchery specific to the fiesta? Common knowledge that open diffs usually spin one wheel, you can't possibly argue that isn't true Otherwise there would be no point in using a limited slip or a locker, etc.

 

[alexrex20]

Do you even have a driver's license?

 

[alexrex20]

https://www.youtube.com/watch?v=pqYkM4nB1l4

 

[Hijinx]

Figured these might help the conversation.

 

[haste]

In a straight line, the passenger side will spin first because the axle is longer. Basic physics. The longer the lever, the higher the torque.

 

[alexrex20]

the axle shaft would not be a lever in this situation. this thread really showcases who has and has not done a burnout in their FiST lol

 

[haste]

I've been driving FWD cars for over a quarter of a century, don't ask me who and who has not done a burnout...

Just look at Hijnxs' post, it's easy to see.

 

[cxwrench]

I've been driving FWD cars for over a quarter of a century, don't ask me who and who has not done a burnout...

Just look at Hijnxs' post, it's easy to see.

That doesn't change that fact that you have a basic misunderstanding of the 'physics' involved.

 

[alexrex20]

I've been driving FWD cars for over a quarter of a century, don't ask me who and who has not done a burnout...

Just look at Hijnxs' post, it's easy to see.

But his photos clearly show both tires smoking. And so does that video I posted. LOL

Sent from my SM-G960U using Tapatalk

 

[D1JL]

The (transmission) output shaft drives the differential ring gear.
The power flows through the side and pinion gears to the halfshafts.

There are so many things that can then alter traction at any given time or place.
It stands to reason that the tire with the least traction at that instant would be the one to spin first.



Dave

 

[haste]

That doesn't change that fact that you have a basic misunderstanding of the 'physics' involved.

Try loosening a screw with a 3" long screwdriver compared to a 6" screwdriver and tell me which is easier to turn.

But his photos clearly show both tires smoking. And so does that video I posted. LOL

Sent from my SM-G960U using Tapatalk

Clearly more smoke from the right front.

 

[haste]

How about another theory. Due to the length of the shaft on the right axle, it twists when torque is applied and snaps forward more than the left side therefore causing the wheel to lose traction easier. I haven't measure the thickness of the left/right shafts but I assume they are the same diameter.

 

[alexrex20]

I don't need theory. I know for a fact my car spins both tires if I dump the clutch from a stop. Next.

 

[cxwrench]

Try loosening a screw with a 3" long screwdriver compared to a 6" screwdriver and tell me which is easier to turn.




Clearly more smoke from the right front.

You have got to be kidding me. It's all about the size of the handle and how you grip it when using a screwdriver. Absolutely nothing to do w/ the length of the screwdriver shaft. Do some research on the interwebs before spouting stuff like this. Please...it'll make you sound way more intelligent. If you can't figure it out lemme know and I'll provide some links to the formula.

ETA: The shaft of the screwdrive is not a 'lever' in this type of work.