How to Build a Bet­ter Mud Ter­rain Tire

4WDrive - - Tech - PHOTOS BY YOKO­HAMA In­ter­view by Perry Mack with Far­dad Nik­nam, Di­rec­tor of Seg­ment De­vel­op­ment for Yoko­hama Tires Far­dad Nik­nam is Di­rec­tor of Seg­ment De­vel­op­ment for Yoko­hama Tires

4WD –

Hi Far­dad, thanks for tak­ing the time to an­swer ques­tions about this new tire. Any thoughts to share be­fore we get started?

Far­dad Nik­nam

– Thank you for call­ing. I’ll start by say­ing that the project started when we first went to con­sumers to see what they wanted from a new mud ter­rain tire. We knew we had to be bet­ter than the com­pe­ti­tion. Driv­ers said they wanted ‘stronger, longer, shorter and qui­eter.’ A stronger tire that’s more chipand cut-re­sis­tant; a longer last­ing tire with re­duced tread wear; shorter brak­ing dis­tance on wet sur­faces for im­proved safety and per­for­mance; and a qui­eter tire while driv­ing on-road.

4WD

Sounds great. Let’s start with stronger. Ex­actly what is GEO SHIELD con­struc­tion?

Nik­nam

– First, it’s a stronger polyester fiber. We achieved that by in­creas­ing the fil­a­ment core di­am­e­ter – they are thicker fibers. Sec­ondly, we added two full lay­ers of ny­lon cap to the belts be­neath it. Many man­u­fac­tur­ers only use one. Fi­nally, we ex­tended the ply edges fur­ther up so the ply pro­tects more of the side­wall. 4WD -

What has been added to the tread com­pound, or how has the man­u­fac­tur­ing process been to changed to in­crease tread life?

Nik­nam

– Most tire man­u­fac­tur­ers use a car­bon black base com­pound in this seg­ment. The goal is to get the three com­pounds to bind to­gether as best as pos­si­ble. We’ve used smaller car­bon black par­ti­cles, which im­prove the bind­ing with the other com­po­nents like nat­u­ral and syn­thetic rub­bers. We also added sil­ica to the com­pound. The sil­ica im­proves the wet brak­ing per­for­mance with­out any

com­pro­mise in other per­for­mance ar­eas. Ad­di­tion­ally, we de­vel­oped a flat­ter, wider con­tour con­cept which im­proved wear per­for­mance.

4WD

Aside from us­ing sil­ica, most tire fea­tures in­volve a per­for­mance com­pro­mise. You im­prove one fea­ture only to de­crease an­other. The flat pro­file gave you longer wear and more trac­tion – what did you lose?

Nik­nam

– Most tires in the seg­ment are rounded and nar­rower to im­prove pas­sen­ger com­fort. How­ever, the wider, flat­ter pro­file in­creases the tread life by more evenly dis­tribut­ing the load on the tire. That cre­ates a larger foot­print for im­proved trac­tion and wear. We may have lost some com­fort per­for­mance with this con­cept, but we have used other tire el­e­ments like belt an­gel to com­pen­sate for some of the losses. These changes re­sult in im­proved tire wear with a slight com­pro­mise on com­fort that’s not no­tice­able to cus­tomers.

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4WD

You played with the block to void ra­tio to im­prove off-road grip while main­tain­ing wet brak­ing per­for­mance. How did you de­ter­mine the tip­ping point – what mea­sure of trac­tion did you de­cide was best be­tween off-road and wet stop­ping dis­tance?

Nik­nam

– As you are aware, larger blocks im­prove dry brak­ing (more rub­ber on the road), while larger voids im­prove wet brak­ing (by the way sand and wa­ter be­have sim­i­larly). Start­ing with com­puter sim­u­la­tions, we ad­justed the block to void ra­tio so dry and wet brak­ing were well bal­anced. Then, we built more flex­i­bil­ity into the tread blocks to help eject mud (and added stone ejec­tors into the tread base to pre­vent drilling). As the tire flexes through the ro­ta­tion, these two de­sign el­e­ments help keep the voids clear, im­prov­ing off-road grip. Then we added jagged sip­ing to im­prove wet trac­tion. The sipes cre­ate suc­tion as the tire ro­tates, im­prov­ing wet trac­tion while the jagged sipe con­struc­tion im­proves snow trac­tion (like fin­gers clawing into the snow) with­out re­duc­ing the stiff­ness of the blocks. The snow per­for­mance earned the tire an M+S rat­ing.

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4WD

What depth of sip­ing did you use?

Nik­nam

– Most of the sip­ing goes full depth to the tread wear mark. We made sure that cus­tomers would get con­sis­tent per­for­mance through­out the life of the tire.

4WD

- What is ad­vanced vari­able pitch tread? What made you think of try­ing this to re­duce noise?

Nik­nam

– We’ve used vari­able pitch in some of other pas­sen­ger tires so it made sense to use it here to achieve our project goals for this tire. Pitch is how of­ten a block is re­peated. We’ve changed the pitch of the blocks from the cen­ter of the tire to the shoul­der. Us­ing our com­puter mod­el­ing we were able to ad­just each pitch by de­grees un­til we found the qui­etest ride. There is no doubt GEOLANDAR M/T G003 is the qui­etest tire in M/T seg­ment.

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