FOUR PURPOSES OF MOTORCYCLE TIRES
So, what the heck are the four things our tires do for us?
1) They support our bike. (Alternatively, a front and rear pogo stick would create a different kind of “riding” experience).
2) Our tires transmit traction and braking forces to the road, allowing us to get up and go, and slow down or stop, exactly when we need to. (Could you imagine accelerating or braking if we had “tires” made out of, say, steel or plastic?)
3) Our tires absorb some of the surface shocks, working with the suspension to give us a smoother ride. (Even with a great suspension system, we’d have a rougher ride with old-time wagon wheels, constructed out of steel bands that were wrapped around wooden wheels).
4) And of course they maintain and change our direction of travel as a result of our steering inputs. (Hmmmmm. Pogo sticks might be better here….)
All that seems simple enough. And yet there is a bunch of design and manufacturing technology that underlies that simplicity. If you want to know ALL about it, this article ain’t for you (although you can add your knowledge at the end to flesh this out further).
But if you might be interested in a surface overview of your tires without delving into the physics, history, debates and “everything” you can know about tires, well, the upshot of the following is that over the years, tire makers have continued to improve their tires’ performance in relation to those previously noted purposes, for the sake of a better, safer (and higher selling) product. The best news is that you and I benefit from all the complex stuff that brings that about.
WHAT’S WITH THOSE GROOVES?
The grooves in our tires prevent, or minimize, hydroplaning by providing channels for water to escape beneath our tire’s footprint.
And in case a fast refresher on hydroplaning would be helpful for some, this describes when a layer of water builds up between our bike’s tire and the road. More specifically, it’s when our rain grooves cannot let enough water escape to provide a dry footprint area.
The result of hydroplaning is that our tires seem to “float” above the pavement. (A bad thing for traction-loving motorcycle riders).
More to the point, when you lose traction, braking, or steering control, it sets a scene for an unfriendly sequence in an action movie starring you. The good news is that the handling is simple: roll back on the throttle without braking or steering.
OK, so hydroplaning sets a scene for bad personal movies. Why not make the grooves as deep and wide as possible?
The extreme of that would be knobby tires, which provide a much better grip in mud, sand, dirt or gravel, but they feature a smaller contact patch, which results in less traction on pavement, while wearing much faster. Additionally, that tread pattern is noisier and creates a rougher ride on pavement, compared to the tread patterns of street tires. Glad you aren’t a tire manufacturer, yet?
Generally speaking, manufacturers are engaged in a process of rectifying the differences between deeper tread patterns to enhance safety, as opposed to simpler patterns which can be less expensive to produce, especially when simpler patterns may even provide a smoother and quieter ride. When we buy our tires, we are paying those tire manufacturing engineers to make those decisions and continue to improve their wares.
Speaking of grooves, good old racing slicks have none. They not only don’t work well in the rain, they don’t even work well on the pavement, under “normal” riding conditions. Slicks are addicted to very high, continuous speed. If they don’t get that, they don’t bother to warm up to achieve their optimum traction. Slicks are so temperamental in this way that they are illegal as street tires.
TYPES OF MOTORCYCLE TIRES
This is a larger topic than the intent of this article. But since we’ve already touched on off-road (knobby) tires and racing slicks, we might as well visit a few others.
General street tires are what have been primarily discussed in this article, which are tires for pavement that deliver good performance, reasonable wear life, and good rain handling characteristics.
High-Performance tires are for aggressive sport-bike riders who want more performance than mileage. Such tires provide better traction in high-speed cornering at the expense of a shorter life expectancy for the tires themselves. Both street and sport tires have good traction even when cold, but when warmed too much, can actually lose traction as their internal temperature increases. With production sport bikes that now blast high into the triple digit range, there is good reason to pay attention to the manufacturer’s “speed rating,” which is a tire code that indicates the maximum permitted speed that the tire can sustain for a ten minute endurance without being in danger. In other words, going over 150 mph on a tire rated for more pedestrian speeds is another way to put yourself in a personal action movie with an unhappy ending for the hero.
Touring tires are generally not designed for high cornering loads, but rather for long straights, good for riding across the country and good for longer tread life.
Dual-Purpose tires are a unique blend of very divergent requirements for dual-purpose bikes that run on street and dirt. Such tires are a compromise between street tread patterns and knobby tires and are not great at either function, but they are better than riding with a street tire off-road, and are better than riding a knobby tire on pavement. But that’s the whole design of dual-purpose bikes, they are a practical (and fun) compromise between widely disparate requirements.
WHAT ABOUT CHICKEN STRIPS?
This point is arguable as to whether it is worthy of note. But if someone points to your tires and comments about “chicken strips,” he is referring to the width of unused tread on the edges of your tires.
That width indicates the angle that you lean your motorcycle. If there is very little (or no) wear near the edge of your tires, it simply means you don’t ride as aggressively (lean as hard in corners) as some riders. So, if a sport-biker points that out to you, they are typically commenting upon their perception that you may be an inexperienced rider who is afraid to lean a motorcycle as far as it can go. In which case, he is actually not overly experienced (or mature) himself, since he either doesn’t recognize that inexperienced riders shouldn’t be pushing the limits of their bike’s performance, nor would he have an awareness that you may be a VERY experienced rider who no longer pushes his/her bike to the limit.
Anyway, the solution to such silly comments is get back on your bike and enjoy the ride.
WEAR-LIMIT BARS
When should we replace our tires? As a general rule of thumb, it’s best to replace them before they are 90% worn. (Some replace them sooner than that). Most tire failures occur in that last 10% of a tire’s tread, so just don’t go there.
Keeping an eye on the wear-limit indicators on your tires let’s us know when we’re riding into the danger zone. When our tread wears down enough, we’ll see these small raised bridges within the grooves, which is our tires’ way of telling us to put them to rest.
TIRE PRESSURE
The most routine maintenance our bike needs, other than filling it with gas, is checking tire pressure.
Our tires should be inflated to what our bike’s manufacturer recommends (check your owner’s manual, or perhaps a decal under your bike’s seat). The inflation number on the sidewalls of our tires is the “maximum” pressure for that specific tire, rather than the “recommended” pressure from the manufacturer.
If your tire pressure is too high, that life-giving contact patch is reduced, which decreases rolling resistance. However, ride comfort is also reduced, because the tires will not absorb some of the surface bumps.
If your tire pressure is too low, your tire’s contact patch is increased, but it also increases tire flexing and friction between the road and your tire. Underinflation can lead to the overheating of your tire, as well excess tread wear, lower miles per gallon of fuel consumption, and may also result in setting a scene for bad, personal movies and more gray hair since it’s also a very common cause of tire failure.
Solution to all of this: Check your tires “regularly” (every day when on a trip), and keep them properly inflated.
Eghad. The subject of motorcycle tires is much more involved than this little overview, so if you’ve got some additional items you want to add, the door is wide open to write a comment below….
Looking to replace the rear tyre on my old Honda deauville. I want the best WET weather tyre. Any suggestions???
An article worth saving and rereading. In fact, I’ll print it out on paper to read at my leisure. Thanks.
About chicken strips: I’ve never considered myself an aggressive rider; quite the contrary in fact. Yet, many years ago, I discovered that the outer edges of my front tire, in particular, were worn smooth while the center strip was almost like new. A few years ago, my son, after following me on his Yamaha, said that he was surprised that the old man leaned so far over on my ’74 MotoGuzzi Eldorado. I guess the old “Goose” just likes to carve up those twisties.
I guess the point is to ride comfortably within your capabilities, but don’t push the limits.
dunlops known for bad rain tire.. compound ? just is
I slow down in the rain but have gone through water that has offered resistence, it was not hydrplaning which I have done in a car. Put new rubber on at 14K miles and the rear tire was sliding in curves, tread was mostly gone. Used the Dunlop 404′s replaced after 14K miles. Now have nice new safe ride.
I have read so much about going dark side and it’s easly cut and dry for a crusier’s back tire go for it, the only people that are against it don’t read and understand.
The math at the botton of this page is soo far off; wow 45 MPH and your “hydropoaneing” I have always heard it starts at 60. Some common sense now.
I was wondering if anyone has ever considered going to the darkside (running a car tire on the rear) and if so I would be very interested in your opinion, pro or con. It is something I have been researching and considering for quite some time now, and I believe that a person can never have too much information when making such an important decision.
Thanx!
B
It looks as though you guys in the States and Canada may have a better choice than we do in the UK. One problem I find with Bridgestone is that they tend to tramline.
Safe biking to you all
I’ve never hydroplaned a bike in almost 50 years of riding, but then again, I slow down when there are large quantities of water on the road. However, I am convinced by the youtube videos of guys riding their dirtbikes at high speed across small lakes that it is certainly possible to hydroplane for some distance. And one that I saw didn’t have enough speed so he and his bike sank into the lake. Tragic, but very funny!
I have been riding for 26 years, and have never hydroplaned. I have never heard of anyone hydroplaning a motorcycle. I have 50.000 on my 650r in 3 years in alabama year round. if I were yall. I wouldn’t give it much thought. oh yeah, the rocket scientist on there scooters. dont hydroplane either.
My biggest problem with tyres is not getting a tyre to suit my bike touring ability. Sure there’s plenty of tyres to suit the more sporty side of my ST1100 and nothing for the touring side so I have to suffer with sport type tyres that give low mileage.
Dual compound tyres are ok but with the set I have on now Ihave plenty of centre tread left but softer cornering compund is worn. I was lucky once and got one of the last sets of Dunlop D205′s, but no more. (20,000 kms on rear tyre)
Another thing is the price. It will cost me AUD$500 to put a set on the bike and get 10-12000 kms on them, I can spend that much on my car and get 55,000 kms at least.
Aqua planing (Australian name for it) has never been an issue on any bike I’ve had.
@Dave I have a roadgear tire pressure gauge. It is digital and has a built in tread depth measurement tool on the end. Comes with a decent case, small and lightweight. Seems accurate to me. If you joint their email, you may get a coupon for $5 off off this model:
http://www.roadgear.com/Accessories/Bike_Maintenance/Ready_To_Go_Hi_Tec_Digital_Tire_Gauge/
at $20.00 I think it was a good purchase (I actually had a coupon so $15), sorry I don’t have the coupon code, if you call rather than go online, you might be able to tell them your kids wiped out your email or something!
Ride Safe – Ride Smart!
lbriley says:
January 21, 2011 at 7:38 pm
If someone could I would like someone to comment on tires that have some weather crack on them, are they safe? I’m 59 and kinda new to riding, last summer I bought a 2007 Shadow VLX 600 I’ve just rode @ 600 miles and I’ve seen some weather cracking on the rear tire and would like to know it it is safe to ride, Thanks for any comments
IBRiley….Weather cracking may be an indication that the tire is old, underinflated, or has experienced some type of trauma. Personally, I am recommending that you have a repair technician examine the damage and discuss your concerns with them. The technician will most likely recommend that you replace that damaged tire as soon as possible.
The link below will explain the alpha/numeric codes stamped on the sides of your tires to help you determine the age of the tires on your new purchase.
http://www.ehow.com/how_5843415_read-motorcycle-tires.html
I hope this has helped answer your question and I wish you many miles of safe riding.
Big Mike
If someone could I would like someone to comment on tires that have some weather crack on them, are they safe? I’m 59 and kinda new to riding, last summer I bought a 2007 Shadow VLX 600 I’ve just rode @ 600 miles and I’ve seen some weather cracking on the rear tire and would like to know it it is safe to ride, Thanks for any comments
Dave – in my experince (South-Africa) all the tyre pressure guages sold fron the shelf were out – you have a choice – buy either a digital self-calibrating guage or for the same price get tourself a respectable TPMS.
you did touch on air pressure but allow me to point out the obvious and that is that wheels dont run on rubber they run on air – if they ran on rubber then the tyres would be solid. so it is vital that you know your tyre pressure (and temperature) at all times not just what the gerage guage said it was in the cold morning or the hot afternoon. in short one cannot talk about tyres without including in the converation TPMS.
For Tim concerning tire plugs: Last year I ran over a 5/16 bolt on Prince Edward Island. I plugged the rear tire and rode all the way to Iowa when I had to replace the tire due to wear. I never had a bit of trouble with the tire. Most tell you to replace the tire but I’ve found that that is not always true. I’ve even had to use 2 plugs on some large holes but then I run less air pressure.
I’ve learned the hard way. Keep good tires on your bike.
Wet weather tread design is very interesting. One thing to look for in a good wet tyre is the latteral spreading of the the “rain grooves”. You will notice that higher end tyres will have grooves that start narrow from the center and get wider as they approach the edges (shoulders). This feature helps clear the water from the grooves. You will also notice that good quality tyres have nice rounded or concave grooves which also reduce the friction of the water as it is squished (pumped) out from the grooves. It’s all about draining the contact patch as efficiently as possible ( as the tyre comes to a complete stop each revolution ).
In order to calculate the slide on a tire, or hydroplane there is much to consider. First total mass [bike +rider (s)] tread shape and depth, the coefficient of friction between contact areas (here will include not only surface water but the material driven on, the material the tire is made of, as well as the temperature of both) as well as the angle to the ground, level of incline and curvature of the road, center of mass, moment of inertia with acceleration. Air friction, is it windy?
The equation is not an easy one to use and is something you build with known values to find unknowns, So while you can technically create a standard equation for use a custom one by a knowledgeable person for the individual situation is going to be much more accurate. The more precise you are the more complicated it becomes, to be most accurate involves a moderate level of calculus to say the least. It is much easier to reconstruct once you know conditions. Its Much easier to just reconstruct an accident, which is what DOT would be doing. My best recommendation is ride smart, pay attention and maintain your bike following manufacturer guidelines on your tires.
If you truly are interested in the physics a basic algebra and trig based physics 1 class will begin to breach the subject. Although I will warn you th real applications will take research and schooling into a graduate degree.
Since we only have two tires under us, I feel obligated to check the pressure before each ride. My 2008 Road King has air valves that you cannot get to unless you lie on the ground. This has forced me to get a set of tire pressure monitors for around $200.00. You carry the fob in your pocket and can get tire pressures and temperatures whenever you want. I think this was a worthwhile investment.
I also got a deal from my local H-D dealer when I bought the bike–free tires for life! I got my first set at 10,000 miles and will continue to get new tires every 10,000.
Anybody have a suggestion for a good tire air pressure gauge? I have 3 and none of them give the same reading. I want something I can trust.
I was wondering which brand and model tires are the best for rain riding? I own a 1988 suzuki gsx-r 750 with full race exhaust(not the best for my application but it is what came with the bike and sounds awesome) and 3 main jet increase to optimize the exhaust. Everything else is stock. I live to ride in the rain, I choose rain over sun every time I ride. I’ve hydroplaned at over 230kph its only a temperary lose of feel and tire contact to the road. As long as its in a straight line you’ll be fine. I think I have a good idea as to what tires work well in the rain by sight of tread pattern. But ultimatly really don’t know for sure. I was wondering if I could get some ideas from you guys. I have had two sets of bridgestone battleaxes. An old bt something no longer produced but worked very very well in the rain! The newer battleaxes are no where near as good in wet conditions. My bike is at the shop so I can’t say what numeric designation they are either. Any ideas or help would mean alot to me. Thanks MIchael Sandham
Hi Lester, you are right when you say that the laws of physics are quite involved. This is in fact the reason why one mostly uses approximations. For our (motorcycling) purposes, acquaplaning happens at a speed when the quantity of water going through the tyre’s grooves is lower than the quantity of water met by the rolling tyre in its progress forward. It can be seen by intuition alone however that by increasing the speed, a point is reached when the tyre simply floats over the water (it’s not really “floating”, it’s an effect of the speed) and then you have “aquaplaning”. Think of a kid throwing (flat) stones over the surface of a pond: if the angle of approach is low enough, the stone will bounce quite a few times over the water, until it slows down and then it sinks.
True, weight of the bike and tyre depth have a certain effect, but over 120 km/h (about 75 mph) you are practically sure to experience the phenomenon. On a track the situation is slightly different because the surface is practically “billiard-smooth”, no potholes, and the tarmac is self-draining, so that effectively there is only a very thin film of water over it. Maybe if I were paid like a GP pilot, I too would risk travelling at 200 kph.
As it is, especially on a normal road, where water depth can suddenly go from a couple of millimeters to a couple of inches in correspondence of a pothole, I will stick to the lowest possible speed to avoid being rear-ended by some clever sardine-can driver.
very very interesting note. i will put it on practice. thanks a lot
Would you like to write something about the durability of plugged tyres?
I recently got mine plugged while on a touring holiday in Wales, following a puncture in the rear tyre caused by a crosshead screw, which embedded itself about 1½ inches from the edge. It works fine, in fact I did 200 miles to get home at about 100 mph most of the way, which luggage, but how long can I continue riding on that tyre, given that it still has plenty of tread and that an expert mechanic did the job for me?
Both Steve and Lester make very good points.Mine is this.When racing in wet conditions, “special” tires are installed. How special are your tires? That is the ultimate question. Most of us have “regular” tires and therefore should slow down to a safer speed.Or risk loosing traction.
Hey, Bob. I’ve heard some California Highway Patrol Officers using such formulas to calculate hydroplaning speeds. This is utter nonsense. The laws of physics are much more involved than that. Let’s take a hypothetical situation. Two motorcycles. One weighs 250 pounds, has a rider that weighs 150 pounds, and is equipped with an extremely wide set of roadracing slicks. He is riding on a very smooth road surface, that is also very flat, so there is little drainage to the side. It has rained 2 inches in the last hour.
The other motorcycle weighs 600 pounds, has two riders on it, each weighing 250 pounds, and has normal width tires with excellent wet weather tread design. This motorcycle is being ridden on a highway with rain grooves cut in it, and good cross fall for drainage. It has rained 1/4″ in the last hour.
The California Highway Patrol would have you believe that if both of these motorcycles had their tires inflated to the same pressure, they would hydroplane at the same time. I beg to differ.
Bob, a hydroplaning calculation would have to include more than just tire pressure.
What about tread depth? The deeper the rain groves the more water can escape so the faster you can go without hydroplaning.
The type of road surface and the depth of water on the road would also make a difference.
With rain tyres, MotoGP riders go over 200 km/hr in the rain without hydroplaning.
I did a little more research on motorcycle hydroplaning and found this from Wikipedia.com:
“Motorcycles benefit from narrow tires, which are less vulnerable to hydroplaning because vehicle weight is distributed over a smaller rubber contact patch. Tires with a round, canoe-shaped contact patch are similarly effective at pushing water to the sides. The comparatively light weight of most motorcycles counters this advantage, however. Further, because road friction is reduced in wet conditions, the lateral force that any tire can accommodate before sliding is greatly diminished. While a slide in a four-wheeled vehicle is often correctable, the same slide on a motorcycle will generally cause the rider to fall, with severe consequences. Despite the relative lack of hydroplaning danger in wet conditions, motorcycle riders must be even more cautious because overall traction is reduced by wet roadways.”
Thanks Bob. I hadn’t encountered that calculation for hydroplaning before.
To find the speed at which you will start to hydropoane use the following.
9 times the square root of the air pressure of your tires. For example, your tires are inflated to 30 psi. The square root of 30 is 5.5 times 9 = 49.5 MPH. Note: my square root is rounded to the nearest tenth. In practice drop the tenths and just use the whole number. So 5 times 9 = 45 MPH.
Your Welcome.