5 Ribs

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Informal staring out the window while at red lights survey over the past 2 weeks shows me that in my town over 95% of tires are some variation of a 5 rib. I think I saw a 6 rib on the back of a ‘Vette. I spotted 4 ribs on the back of a pickup and on the trailer of a semi . There were a couple of I don’t know what ribs on off road mud pickups. Motorcycles excluded. Other than those it made no difference in any of the sizing parameters (tall, short, narrow, wide, aspect ratio). So why is 5 the magic number?
 
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5 is probably the most common. 6 ribs makes sense for wider tires, and 4 ribs for narrow tires. The old General Altimax RT (not the new RT43) only had 2 ribs in the smaller sizes, and 3 ribs for 195 and wider. The RT43 is now 5 ribs. My old ContiExtremeContacts only had 3 ribs. The Falken Espia winter tire has 7 ribs! Probably the best tread-void ratio with the 5 ribs. Here is a pic of the 2-rib RT:
 

Tom_T

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Don't see snow tires down here in Florida. Still can't figure why there isn't a 3 rib on a Prius, Fiat or Mini. Seems like when a narrow tread is cut into 5 ribs it would have more flex than the same tire in a wider width.
 
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I assume there must be some exponential relationship between the distance to a void in the tire and how much "lift" a film of water produces when you are driving in the rain. For mud or snow though, a clean channel all the way around tire is just wasted space in the tire foot print for traction once you get a bit of wheel spin.
 
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After many brands and sizes of tires purchased I can tell you that tread design is an unreliable indicator of tire performance. We buy at least 16 tires a year, sometimes 24 or more. Mostly for trucks in a fleet, but I have two "tire eaters" that eat tires for breakfast. Michelin Pilot SS is my favorite example. Boring and strangely devoid of any "cool" looking tread patter, yet absolutely at the top of the performance scale IMO. Remarkable lack of voids yet fabulous wet weather traction. Smooshy soft yet 30k mile warranty. Don't let a cool tread design fool you, as tire designers know what folks stare at...
 
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Originally Posted By: mrsilv04
One rib? The original Goodyear Vector.
Haven't seen those in a very long time. My first car had a replacement set of tires when I got it, believe they were the Sears Guardsman version of these. Not sure if Goodyear made them or not. I do remember it didn't take long before I wanted to replace them due to horrible wet traction.
 
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Originally Posted By: SteveSRT8
Don't let a cool tread design fool you, as tire designers know what folks stare at...
A lot of that has to do with tread compound.
 
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Originally Posted By: SteveSRT8
Michelin Pilot SS is my favorite example. Boring and strangely devoid of any "cool" looking tread pattern
I don't know about that, since they even have some of those cool, oval 'mitochondria' sipes in the outer shoulder block, just like their intermediate rally tarmac donuts, and their Sport Cup stickies. thumbsup cool
 
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Some thoughts on tread patterns: First, I tend to think that "ribs" mean a more or less continuous circumferential pattern - like this: I also tend to use the word "button" to describe the same pattern where the rib is broken up - like this: Please note: I would call the center rib a "rib", and the other 4 ribs "buttons" - although I might refer to the outermost ribs as "lugs". Also, I would recognize that not all tires have "ribs" and "buttons" and "lugs". Some don't have anything that resembles those words - like this: I don't think the above tire has a "rib". One of the first lessons I learned about tread patterns was that circumferential grooves are THEE most effective way to prevent hydroplaning - that even these directional designs that look like huge arrows are only slightly more effective - and IMHO, not enough to justify the confusion the directionality causes.
 
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Capri, it is my understanding that 5 ribs is often mandated by the vehicle engineers. For example, the Goodyear Silent Armor was a 4 rib. It was a very popular and successful tire. However it could not be used as an OEM fitment due to having 4 ribs. My GY rep told me the biggest reason it was discontinued and replaced by the new Goodyear Adventure was because the Adventure is a 5 rib and therefore eligible as an OEM product. Yet that makes no sense due to the Michelin LTX AT2 being an OEM product.
 

Tom_T

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I misused the term “rib”. Please allow me to change that to “5 columns made up of a combination of ribs, buttons and lugs”. Still seems like 5 is a vastly popular number at the red lights. Heck, even my handtruck has 5 ribs on it. Just wondering why after all the physics are worked out for both the Prius and Peterbuilt that 5 comes up most of the time.
 
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Originally Posted By: SteveSRT8
http://www.tirerack.com/tires/BigPic.jsp...lot+Super+Sport Boring. No sense of "style". Just outrageous traction.
OK, I mistakenly thought that these had those oval shaped cutouts in the outer tread block/rib, like the Sport Cups do, but nonetheless, I personally think that is a sweet tread pattern, especially the large edge blocks (it still looks like a cut and grooved slick to me!). smile I also personally think that the Nitto Invo, even in wider widths, is one of the FUGLIEST tread patterns out there, despite everyone else thinking it is the coolest thing since sliced bread. To each his own, I guess.
 
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Originally Posted By: dailydriver
Originally Posted By: SteveSRT8
http://www.tirerack.com/tires/BigPic.jsp...lot+Super+Sport Boring. No sense of "style". Just outrageous traction.
OK, I mistakenly thought that these had those oval shaped cutouts in the outer tread block/rib, like the Sport Cups do, but nonetheless, I personally think that is a sweet tread pattern, especially the large edge blocks (it still looks like a cut and grooved slick to me!). smile I also personally think that the Nitto Invo, even in wider widths, is one of the FUGLIEST tread patterns out there, despite everyone else thinking it is the coolest thing since sliced bread. To each his own, I guess.
It does look like a home cut slick! That outer edge is amazingly sticky like a racing tire, too. Nitto lost me years ago, wore out so quickly I never got a chance to see if they were really any good. A lot like a high end Dunlop in that they got real greasy feeling when hot...
 
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Originally Posted By: HWEaton
Capri, it is my understanding that 5 ribs is often mandated by the vehicle engineers. For example, the Goodyear Silent Armor was a 4 rib. It was a very popular and successful tire. However it could not be used as an OEM fitment due to having 4 ribs. My GY rep told me the biggest reason it was discontinued and replaced by the new Goodyear Adventure was because the Adventure is a 5 rib and therefore eligible as an OEM product. Yet that makes no sense due to the Michelin LTX AT2 being an OEM product.
I don't think I've ever heard a car manufacturer dictate the specifics in a tread pattern. I know there is a review very early in the process where tread patterns are proposed - and by and large, the vehicle manufacturers are fairly conservative when it comes to tread patterns, and some tread patterns might be eliminated if too radical. There may be cases where - say - an All Terrain tire is desired, and a tread pattern is rejected as too All Season like, but the difference between a 5 rib or a 4 rib - I just don't think the car manufacturers have ever mandated this level of detail.
 
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