Okay, I've seen more than my fair share of sets of used tires on the internet. More often then not I see "Plenty of tread left!" with a picture of a penny being used to indicate just how much there is. The reason for this, is because over the years the tire industry has needed to find an easy way to allow everyone in the country a way to reasonably accurately measure the depth of their tread. Pennies are pretty common, and don't cost you a thing. Every single picture I've seen is either misleading (deliberately or otherwise), inaccurate, or the seller legitimately doesn't understand just how much tread depth is left. Now, while the simplest thing to do is simply buy a tread depth gauge (about $3 at most auto parts stores), and it is an invaluable tool, especially in ownership of cars with an intolerant AWD system (see: Subaru) the penny trick can work. I'd love to spiel and bring images in, etc.. but tire rack has already done a much better job running down the whole US Coin/Tread depth measurement thing than i could: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=51 That being said, i do want to bring some points into it: 1. Any tread is not enough tread. The lowest point at which a tire can legally be used on a US road is 2/32nds. By this time, any tire has had severely compromised wet handling, and zero snow handling. Obviously, the closer you get to this point, the worse those things will be. This is something should be factored into how much usable tread there is in the tire. 2. Do the math. So say Joe Blow has a set of Dunlop Z1 Star Specs.. the hot street tire up until this year, and you want to buy them. He gives the tire seller's standard spiel of "They've got plenty of life left!" and shows you the tire is at 5/32nds. Right off the bat, take 2/32nds out of that, because that last bit isn't really something you should use. a quick glance at tire rack's website shows that they come molded at 9-10/32nds brand new. Best case scenario? That tire has 30% tread life left of street use. do you think half the retail value is a reasonable price for something you only get 30% of? do you want to spend the money to mount and balance something with such low life left? 3. Understand the Tread Depths Having a vague understanding of at what points tires become to be problematic can be a big bonus to the safety of yourself or others. while as mentioned before, 2/32nds is the lowest "acceptable" depth by the government, NEVER should you take a tire with that much tread on it into winter. wonder why traffic is so bad when it snows? you're the reason. Tires below 4/32nds really won't evacuate water very well.. this does depend on the tread design as well, but the channels are alot shorter now, so your likelihood of hydroplaning has increased. Tires below 6/32nds won't evacuate snow very well. There isn't enough tread wiggle at that point to break clumpy snow free, and you wind up driving around on snow balls. Snow tires are usually molded deeper to account for this(12/32nds), and extend their lifespans as well as give you that wiggle that lets the siping bite into the snow. Snow tires landing close to or at 6/32nds should be considered all season tires handling wise. And some notes to tire sellers: The penny picture can help, but the penny needs to be pressed against the tread to be accurate, especially if you're doing the 3/4 angle shot of it. Penny measurements are meant to be taken while tire is on the car, and you looking at the tire from the sidewall, not a 45* angle. As mentioned above, do some damn math before you try to price these things. Your OE tires are not worth what TireRack says they are worth. OE tires often have insane markups on a tire that may have a simple change, or one that is undesirable. Often times to take advantage of people who don't really know any better and just want to buy tires and be done. Take the much hated RE-92.. the ****tiest of ****ty tires that 02-05 WRXs came on. That tire at OE pricing is $192 per tire. Only idiots would put that tire back on their car. idiots who buy tires at dealerships (no offense dealerships). Why was it so expensive? because Subaru ordered different compound be used on their OE ones, so that they were softer and wore more evenly over the original 32k miles of the factory warranty, all but guaranteeing no center diff failures during that time. Is that unproven conjecture? yeah, but the durometer readings of OE RE-92s that came on WRXs are significantly lower than that of other RE-92s, and this seems to be the most logical hypothesis. All that being said, do some damn research people. Understanding your tires is an important part of being a car enthusiast, as every single modification you do, or driving you enjoy are translated to the road through 4 small patches of rubber. It may be awesome that you have 400Hp, but if you can't put it to the ground through your tires, you're just wasting money.. unless you're a dyno queen. Thanks to MNBD for this exelent video clearly, and simply demonstrating exactly what i'm talking about:
Good info, thanks Shane! It does drive me nuts when people are selling used tires and provide any sort of measurement other than a measurement in remaining 32nd's. It's also advisable to measure at various points on the same tire, as tires do not always wear evenly. At the end of the day, the tires are arguably the most important part of your car, which I think people forget all too often. Before upgrading your suspension, brakes, power, etc, see what some real tires can do for you (although you do learn a lot by learning to drive (competitively) on crappy tires!)
+1 on the just get a tire tread gauge. Really, for the $5 you spend, you can also monitor tread wear on your own car and rotate tires more appropriately rather than every oil change or whatever. Tires actually need to be rotated more frequently at the beginning of their life, versus the end of their life.
This is a great thread. It's amazing how much misconception there is about tires and tire wear in general. There are a lot of couch racers that have never actually driven on half the tires they're talking about. Which unfortunately floods the internet with useless incorrect information. I saw the actual test video at a tire training seminar a while ago and it's stuck with me ever since. Customers would always say, "Why does it cost me over $500 for a set of tires? Are you just trying to sell me an expensive set?" I would show them this video and after they would finally listen to my advice. The video they used is from an ABC newscast, so skip to :30 to see the test.
Great post Shane! I have a digital tire depth and psi gauge. Great little tool to just keep in my car at all times.
Wait... What... Don't they have more traction when the wires/bands are showing :-/ Thanks again Shane... I always say tires are the best upgrade/mod if your driving preference isn't in a straight line
Even in a straight line, people will see better results from tires. there's a reason Hoosier sells so many drag slicks. Most high end street tires will grab and launch harder than their lesser counterparts
Wha... i don't... how do you mess this up? and does it look like to anyone else they're pushing the tire tread up add some depth? It's clearly the highest point on the tire and i know i don't usually pinch a penny so hard my fingers start to turn white..
I see people driving on unsafe tires all the time and they have no idea that 2/32's takes almost 2x's as long do stop in heavy rain than 4.
Man, I work as a service writer and I wish there was a way management would let me bring my laptop in to show our customers these videos. You would be amazed how many people do not care about their tires and want whatever is cheapest even if it is the wrong size for the vehicle, speed rating, etc. They really get mad when you tell them they can't replace 2 tires on their AWD cars . They should have some sort of basic automotive ownership knowledge class as a part of driver's training.
The difficult thing with tires is (and I know many of you know how this goes) that they're price point product. It's an item that people only see price, not difference in value. This is often times because they don't understand the value and difference a quality tire makes. Another misconception is that the Kumho Solus that Wal-Mart sells for $48 is NOT the same tire dealerships order through USAutoforce etc... They're made specifically for them so they can sell them for less.
Tire rack shaves tires...but you have to buy the new tire from them. Local shops that shave tires are hard to come by (unless you live near a racing specialty shop)
Nice Thread sir. Any suggestions for those looking for dedicated used track tires, what indicators would you recommend buyers to use for inspection?
I was expecting you to be answering this question But I'll say that you wouldn't want to buy used summers tire if they were actually used for motorsports. Tires that have been raced on tend to have excessive shoulder/camber wear and have also probably been heat cycled beyond use. I suppose if you can find a set of good used summer tires (star specs, RS3's, Federals, etc) that someone daily drove politely, they might be a good buy. Otherwise slap on those used track tires and burn em up in a drift session! (on the track that is). If you're talking actual track tires (ie slicks), then I have no clue...I haven't hit that crack pipe yet. Anyway, for my dedicated "track" tires, I normally just buy new.
Oh no, this is brother Shane's show. I'm only here to help assist where I can and create opportunties for him to shine and that's how we all learn, by sharing. He's shared lots of valuable and functional information here and part of being a good listener is asking good questions, I don't know everything so I always apprecaite things even more when I learn about something I don't know. Everyone is going to do the same thing different and the last thing I want to do to him or anyone here is step on their toes. I know he'll help shed some light once he's found some time away from his busy schedule. Thnx Shane.
Very true...Shane has shared some useful knowledge with me over the years as well. ...paging "brother shane?"!
I'd say it really depends. I got to take a ride in a C6 Z06 with slicks on (holy **** g forces.) and he had gotten them lightly used. But this was the president of the corvette club of South Dakota so I'm sure he had connections.
Hmm... Dedicated track tires huh? All of my experience so far has been with street tires, so i probably won't have much good advice on the topic of full on slick tires, but i will impart what i understand. Right off the bat, i'd say the biggest thing about track tires will be their history. Most track tires with any life left in them are coming off cars that are very competitive. To this end, their driver or pit crew will probably have a pretty good log on exactly what was done with that tire. Personally, i can tell you i can get about 100-120 awesome autox runs, and another 40 decent runs runs out of a set of Z1 star specs, and after that i start to see some fall off in their grip levels. If i was a guy with a big budget, it's at that point they would no longer be valuable to me, and i would sell whats left. Similar goes for track tires. Spec Miata take offs can fetch between $20-100 a tire, depending on what they were used for. Qualifier only tire? probably closer to $100. a tire that's been in a race or a few races will fetch considerably less. This will require more trust on the buyer's front. While you can measure tread depth utilizing the handy little divits they mold into the carcas, a comp tire can be good to the core, but it will usually heat cycle out long before that happens, and a significant reduction in grip will occur. It may still be a faster tire than a street tire, but if you're going for top billing, it's not what you want to be on. Once you're to the point those divits are no longer visible, that tire is done, and keeping an eye on the wear leading up to that is very important. you don't want to run out of tire on a lapping session. it may not end well. A Tire Durometer can yield some good data on the hardness of a tire, but you'll need to baseline off something to see just how the hardness at any point will affect the grip and handling. Experience will play a big role here. And always keep in mind the application you're going to use a take off track tire for. Putting a set of Hoosier R6 Cups off a grand-am racer on your car may sound pretty bad ass to take to the local autox, but in reality, this tire will never get up to temp in the 30-90 seconds of an autox run, yielding you hard tires that won't grip at all. Tires like the A6 are specially formulated to be ready to go about 6 seconds into a run, and retain their heat while in grid. That about covers my scope on the track tires thing, if I've missed or incorrectly stated anything please feel free to correct me. Musashi, you have far more road racing experience than i do, so i happily defer to you
Very nicely put and thanks for sharing your experience on the subject. I like keeping things simple and please keep in mind I'm no expert on the subject. I'm just going to share a few simple idea's of how I inspect unsed run off dedicated track tires. You can use these tips on Street R Compounds as well. Some of these are mostly common sense and you won't need any special tools, just need a watchful eye. Physical Tools 1. Purple or Black flashlight 2. White/Red chalk - number the spots if permitted 3. Decent camera w/flash 4. Soft clean hands So step one do the obvious looking for any surface imperfections: 1. Uneven wear like flat spots from locking up the tires. Over/under inflating the tires. Defective materials. 2. Look for dry cracks - this is usually due to poor storage, some people just dump their HP tires in the garage and forget them over the winter. Tires are made of rubber and they are susceptible to air temp changes and it will cause them to dry out. The most common places are on the outter shoulders of the tire surface. This is probably the second worst and unsafe thing you could have on your tires. 3. Look for cuts on the tire surface, this is a very common problem with those who choose to drive their street and track compound tires. Because of it's much larger contact patch it's going to catch everything on the road surface. If you have a highly modified vehicle and you plan to drive hard at an event it may be in your wsier to keep these off the streets. I've seen friends with multiple cuts that were over an inch long and down to the core. It maybe fun to show them off on the streets but you've just made them useless at this point. 4. Hot spots - are sometimes caused by inproperly inflating your tire's pressure. Under inflating will cause you to use more outter sides of the tires surface. Over inflating will cause you to use more of the center. You can tell this because those area's will be harder and more shinier. 5. Check the outter sidewalls on both sides as well as inside the tires, you may find a perfectly good tire surface only to find out you can't safely mount this tire. 6. Probably the most dangerous element you'll find on a tire is oil/coolant/brake or hazardous fluids you'd find from within your own car. I'm talking about it looks like it's been sitting on a pool of this stuff for a while. You can't remove it or clean it up as the tires rubber acts like a sponge and it will absorb it. This makes the tire dangerous because you no longer have a consistent tire, the tire won't be able to maintain the core temps to achive maximum grip levels and under high performance driving situations it will not be predictable. Often that spot will become harder then the rest. Step two: I bounce the tires a few times about 3 feet high and listen to how sound it gives back. You'll want to make sure all four are consistent. Step three: I put some of my own weight to the tire and observe how it flexes, you're looking for structure deformation. You've all heard that high performance tires are more square, meaning the corners of the tires come out and then they drop off, they don't round out like your All-Season tires. This is part of it's design to help maximize corning grip. It's going to be difficult to find a good used set with a lot of rubber left on the corners, but what you're looking for here is if they were not running enough much camber, over driving the tires by staying inside the corners too long and bad alighnment or suspension geometry that just eats up a lot of of tire in the wrong places. You can tell this by comparing the whole set and most people will have their tires marked w/Driver Front, Driver Rear, Passenger Front and Passenger Rear. You can learn a lot about a persons driving just by studying their tires but we're not going to cover that here. Take your time when inspecting used tires and use the tools I've mentioned above to help you highlght the area's of concern. The nice thing about a flash camera is the 2 dimension picture which really helps me catch things I may have missed. Like for example the shadow of a groove or a notch. I'm not discouraging you from buying used tires. I'm just saying buy smarter, know what your intent is for these tires. This will hopefully give you a leverage you'll need when negociating a final sale price. Oops I forgot to mention unlike street tires which has tread depth from the blocks, track tires have dipples running across the tire's surface. Those are your indicators for surface material life.
^ Thank you sir, but I'm actually kinda embarrassed. Let's dial down the volume just a bit as I'd like to still fit in my Small Helmet.
Just saw this. This is great information! Should've seen this before my tire sale. Plus this is good too as I'm in search of used tires and I'll be using these measurement techniques to ACUTELY measure tires. Thanks for the post!
I have some photos of my tread depth gauge (same one as posted above) in this thread: http://mnsubaru.com/threads/fs-08-gr-sti-limited-bbs-wheels-tires-tpms.42728/ It is a handy tool to have.
Errm, you might want to check that math again... Assume 9/32 new....take off the 2/32 for legality....equals 7/32. 3/7 = 43% If you want to be optimistic and use 10/32.... 3/8 = 38% You can't skew the used tires and not account for the same on the new tires. Sorry, had to, I am cursed as an Engineer. Don't worry, still love ya. That said, anyone want to buy some Z1s with plenty of life? Looks like they may even come with an attached car! Hehe
