bald tires on dry roads

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My weekend car never gets driven in the wet, in fact not even driven over a puddle caused by sprinkler overspray.
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The tires aren't bald yet but they're getting there. Is there any reason to replace them immediately when they wear to the indicators? I was thinking of driving them a little past this point, figuring they would perform as slicks. Is there any safety or performance issue? The only issue I can think of is that the speedo/odometer will read high.

Once they wear to the indicators, how much actual rubber is left before you encounter the inner belts?
 
During emergency braking, the tires will not grip the road very well, causing your braking performance to be as if you were on ice with your slicks.

I would also avoid high speed driving. Anything over 35 MPH, I would most likely not do, in case of a blow out the tires will be susceptible to.

If you're in a bind, purchase a decent set of used tires.
 
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I would worry that is there was an accident what would happen to you legally? Now days the governmentand its stooges are out to get you as well as most every one else .
 
In my state, and most from what I understand, less than 2/32nds is legally bald, and could be used as proof of negligence if you get into an accident.

A very improbable situation, I agree, but you asked. From a non-liability standpoint, I'm amazed at how bald Edmunds allows it's long term fleet tires to go. So I doubt you'll have any problems at the wear bars. I wouldn't go much lower, though.
 
Read a review on some brand new UHP tire shaved to 4/32" for racing. I presume in some semi-stock class that requires DOT rubber. They made the point that because the tire was new (sticky rubber?) it was better than the same tire just worn down.

Punctures shouldn't be a problem, think about it, hit a obstacle exactly wrong in your tread when the tire is new and it's thick enough with the belts etc to take the abuse.
 
When I was in High School I drove around on almost bald tires.

One day I gunned it a little bit to do a left turn across a 2 way stop. All I knew is that it was not good when I started spinning out with traffic coming from both directions. I ended up facing the wrong way into on coming traffic.
After everything was said and done, and I had gotten off the road and into a residential area where I could examine my car, I found out that I had somehow blown out both my rear tires.

A dry summer day in a 1983 Ford LTD, an over weight under powered 4 door sedan with a 2 barrel carb. ANY CAR, and I mean ANY CAR today is more powerful than my first car.

If you have kinda bald, or almost bald tires, and you are out driving and know about it, And if this really is your "weekend" car.
You are asking for trouble, both that you can total your car, kill or injure yourself and others.

What I learned that day is that even the cheapest tires out there are better than bald tires. I have been financially crunched before, and cheapo tires have really helped.

I would let your weekend car sit in our garage until you can get new tires on it. It isn't worth the risk or the litigation you will face if you are found to be at fault.
 
In theory, a solid surface (not broken by tread groves) on clean, dry pavement gives the best traction. However, not sure bald is the optimum solid surface and then streets are rarely clean.

There also are legal issues if you drive past the wear bars and hit someone and get sued, you may be held negligent. Also, cops could give you a ticket, but not likely to notice unless stopped for some other reason.
 
Originally Posted By: eljefino
Read a review on some brand new UHP tire shaved to 4/32" for racing. I presume in some semi-stock class that requires DOT rubber. They made the point that because the tire was new (sticky rubber?) it was better than the same tire just worn down.

Punctures shouldn't be a problem, think about it, hit a obstacle exactly wrong in your tread when the tire is new and it's thick enough with the belts etc to take the abuse.


It has to do with the stresses on the tire lugs that occur over time. An unshaved tire has "longer" lugs, which increases the mechanical advantage and pressure on the base of the lugs. By the time the tire wears to the base of the lugs, they are already half worn out structurally (not measured by thickness). This is now it was explained to me at high performance driving school.

The instructor told me that shaving a brand new DOT tire to race thickness actually results in getting significantly more miles out of the track tire - on the track.
 
TallPaul is correct. Just looking at dry traction, bald tires are the best. Look at the indy cars, they have bald tires. If tread resulted in better grip, they'd have tread.
 
Thanks for the replies. If the bald tire is structurally weaker and prone to failure, then it's a no brainer -- replace with new ones. In case I wasn't clear before, money isnt a consideration as I can easily afford new tires, I'm more interested in optimum dry performance.

But why are race/competition tires bald and able to handle enormous stress without failure?
 
They had these tires called "cheater slicks" which were slicks (basically no tread for drag racing) with a bare minimum of tread groving to be legal, or so it seems that is what the case was. That might be your best option, though high end tire companies may make a similar tire that is more suited to road racing performance vs drag racing.
 
Originally Posted By: Kestas
Look at the indy cars, they have bald tires. If tread resulted in better grip, they'd have tread.

But you also need to consider tire temperature. Those bald indy or F1 tires don't start to provide optimal dry grip until they are heated up (either at the pit or by driving on them aggressively).

In typical street applications people don't drive hard enough to heat up their tires so much, or by the time they do, their typical commute is over.
 
I'll try to answer some questions posed here.

1) Yes, the optimal dry traction with a given tire is with minimum void area for maximum surface area at the tire-road interface. Unlike the physics of friction between solid, hard objects (where surface area is NOT an issue and greater surface area does not increase the overall friction, rubber is an elastic malleable substance and a large part of its traction is dependent on what is called in the industry, the 'rubber interlock'. This is where the rubber molds itself to the imperfections and irregularities in the surface. Softer rubber molds to the surface better, but if it gets TOO soft, then the rubber nubs extending into the microscopic depressions in the surface can shear which results in lower grip.

2) A bald tire and a slick are NOT the same thing. Racing tires and R-compound tires are designed with a minimum of void area so there is a maximum amount of rubber contacting the road for the greatest grip. As someone else has mentioned, racers will sometimes shave the tires for a shallower depth to increase grip AND service life of the tire. This has to do with heat buildup in the tires. A rolling tire inherently builds up heat. This is due to both the rolling friction with the road, and from internal stresses in the rubber as it deforms while rolling on a hard surface.

Shaving the tires reduces the amount of deformation (what racers feel as and call tire squirm) AND the shallower thickness of the rubber aids in dissipation of the heat buildup in the tires. A given rubber compound has an optimal operating temperature range to provide maximum traction. Below this optimal temp range, the rubber is too hard to fully conform to the surface irregularities to provide maximum grip. Above the optimal temp range, the rubber becomes too soft and wears and shears more easily also reducing max traction (what racers call overdriving or overheating the tires). The reason shaving increases grip and tire life in racing slicks is due to lower heat buildup and reduced deformation. Thicker rubber deforming more under hard lateral loads can cause a phenomenon called chunking where chunks of tread break off.

On a sidenote, because a tire's max traction is achieved at an optimal temp range, it IS possible to 'overtire' a car. This is when a racer mounts tires that are significantly too wide for the car. Within reason, wider tires DO actually improve traction in all directions (braking, acceleration and lateral), but if the tires is much wider than the weight of the car is fit for, the light car may not cause enough deformation to keep the tire rubber in its optimal temp range, resulting in reduced maximum grip.

3) The reason a bald tire, worn down till there's no tread is NOT equal to a slick tire is due to several reasons. For one, all rubber tends to harden over time. This is dependent on the rubber's composition and the conditions it has been exposed to. With race compound rubber, this is known as the heat cycle life. The softer race compounds have a much shorter heat cycle life than street tires. A set of Hoosier race tires for instance, can heat cycle out in one weekend, even though the tires have enough tread/thickness left, the rubber compound has hardened so that they no longer provide the maximum traction levels as they did new. Street tires do not heat cycle out as quickly, but they still do. If you've ever seen a tire with lots of remaining tread but with visible cracks on the sidewalls, you've seen the evidence of this. Exposure to more heat cycles, exposure to UV (sunlight) and exposure to ozone all accelerate and exacerbate the rubber's deterioration.

For maximum dry traction, buy tires made for it as opposed to running regular tires till they're bald.


Max
 
So then, if you want to run a slick and you current tread is 7 inches wide, why not get a wider tire, say 7.75 inch wide tread, so that minus the grooves, you actually have 7 inches of functional rubber width on the road?

(Here in snow county you want somewhat narrower tires to bite through the snow.)
 
With a bald tire you will have good grip on dry pavement.

With out the tread, you are getting more rubber to surface contact, thus providing a bit more bite.
I would never run like that though. Way to risky. Get them changed.
 
What kind of car are you driving? And how are you driving it?

My Dad had a 1990 miata with the original tires in 1998. Half tread left but they had hardened up quite a bit, giving less grip but I thought it made the car more fun to drive on dry pavement. In that car you could tell exactly what was going on with the tires and getting some slip angles at a reasonable speed was fun and not really dangerous. Afterall even with the reduced grip it would still stop and turn faster than most vehicles.

In the rain it was not good so we didn't drive in the rain... As long as you understand the limits of the car and tires running them down to barely legal levels isn't all that dangerous. The average dump truck turns and stops, well, like a dump truck. So the driver drives that way and no problems. I imagine your car handles better than the average dump truck.
Ian
 
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