WideGear Fat Conversion
Performance System

 

 

 

 

Johnson Engineering
100 Blake Road
Denver, IA 50622
(319)984-9298
(319)984-9299 fax
info@twistgear.net

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May 13, 2003

Designed and Manufactured Exclusively in the USA!

Wide Tire Conversion And A Performance Close Ratio!

wg kit

WideGear is a plus 30mm (1.18") extension kit for late model (1991 and up) Big Twin five-speeds with trapdoor access (helical details). It also fits earlier five speeds that have been updated with a splined clutch kit. (At present, we don't offer a Sportster kit.) We offer transmission spacers for FLs, STs, and Dynas.

Incorporating Johnson Engineering's breakthrough TwistGear-based close ratio fifth-gear replacement set, tire clearance is provided by extending the transmission and engine sprocket shafts as opposed to the potentially unstable workaround of offsetting the wheel, entire drivetrain, the transmission only, or various combinations of the above. The billet transmission spacer shown in photo is for FL/FXR applications. Dynas require a two-piece spacer, while STs use our exclusive cast one-piece spacer, seen at bottom of page.)

What About My Twin Cam?

Thinking about a wide Twin Cam? Then forget about the transmission offset kits. The only way to fit wide skin behind a TC is by extending the primary, or offsetting the entire drivetrain (don't forget to put your foot down), or offsetting the wheel. For the first time you can take advantage of TwistGear performance and Twin Cam power in a wide tire profile...perfect!

Fit Up To 230mm — And Wider!

wg trapdoor

The extended main and input shafts safely move primary 30mm outwards.

WideGear’s 30mm extension (trapdoor assembly shown at left) means real rear tire fitment of at least 230mm (Canadian manufacturer Custom Valley uses WideGear in their own demo bike, offers 240mm ST and Dyna conversions) can be achieved without offsetting the wheel, engine, or transmission.

The result is a huge increase of 100mm of additional tire width when installed using a chain final drive. When a 1.5" belt is retained, 60mm (i.e., a 190mm tire when 130mm is stock) is the maximum width increase without additional modifications for more clearance. Use of a narrower, 1.125" belt for more clearance is another option, but due to the higher stresses generated by larger engines hooking to bigger tires through a close ratio box, there is a greater risk of belt damage or failure as a result. Practically speaking, chain conversion is the simplest method of gaining additional clearance, and has the added benefit of many more (and simpler to install) ratio options, although a good many riders are hesitant to give up the comfort and convenience of their belt.

Offset? Not If You Can Help It

widegear cutaway

Viewed from the front, WideGear's massive 30mm engine spacer is at right, with our 30mm extended main gear seen on end (left). Right behind the maingear is the transmission, kept in line with the drivetrain with our billet spacer for FLs and FXRs. Spacers are also available for STs and Dynas.

Some of the inherent drawbacks of the other wide tire conversion methods currently used include intentionally offsetting the rear wheel to gain clearance, which can introduce a nonlinear tracking situation, as well as headaches trying to fit fender and struts. If wheel offset is used in addition to any factory offset, the results can be alarming. Another factor to consider when dealing with wheel offset in particular is the tire design. Different manufacturers products can have a dramatic impact on riding stability.

Shifting the engine and/or transmission, the main method of providing the necessary clearance for a wider tire, has the undesireable side effect of intentionally repositioning the center of gravity to the left (outboard) to an even greater degree than offsetting the primary alone. When combined with an offset wheel, the resulting ride can be erratic. If you've ever watched a wide tire conversion rider fighting the handlebars, listing to the left while riding, or wondering what direction the bike will take going into a curve, you've seen the effect extreme offset has on handling.

WideGear (right) avoids these shortcomings by using spacers between the tranny and engine, and by extending the main gear (shown above, foreground) and mainshaft 30mm (1.18") outward. (Notice the helical angle of the extended main gear, as well as the extended engine sprocket nut and coupler in the photo.) And although the weight of the primary is moved outboard, the additional penalty created when the tranny and starter are also moved is avoided, as is the extreme weight relocation caused when the engine is also offset.

30mm For Plenty of Clearance

compare
Side by side comparison shows TwistGear profile, left, and WideGear's massive plus 30mm, right. The extra 1.18" of extension accomodates a wide variety of tire widths, without the need to offset the transmission or engine.

That said, if show's the name and sitting's the game, WideGear provides an excellent starting point for stuffing that fat skin between the rails. WideGear gets you going by allowing for an additional 2.36" of tire width, and if more is needed, than tranny offset with appropiate spacing at the engine is always an option. For all around performance, though, offset should be avoided, particularly when the aggresive gearing of our close ratio tranny is factored into the equation.

Fully Integrated Design

cast spacer

Unique cast transmission spacer (ST only) is one third the weight of billet, and heat treated to resist additional stress placed on components by extending the primary.

WideGear is the only close ratio engineered approach that retains proper design geometry and weight distribution, while maintaining the overall integrity of the drivetrain as it relates to the driven wheel.

Our revolutionary kit features the superiority of a one-piece fifth-gear and countershaft combo, and our unique cast spacer for STs. (Dynas use a 2-piece spacer, while FLs and FXRs require a billet spacer, which is a slightly higher special order option.) Installation can be completed without removing the engine or transmission, although the total conversion process remains a fairly complex procedure best undertaken by knowledgable technicians familiar with the necessary skills required for critical suspension and drivetrain modifications.

The complete kit contains all necessary parts, including extended clutch pushrod, engine and transmission spacers, starter coupler, extended compensator sprocket, and nut. Also included are our exclusive triple lip oil seal, chamfered transmission spacer, and 4-point trapdoor bearings.

WideGear also features a needle bearing (extra cost) that fits the engine sprocket nut for outboard engine shaft end support. (A suitable outer primary with a built-in support shaft or nub is needed to utilize this feature.)

What About Performance?

chartWideGear is the only performance oriented conversion kit available today. Manufactured in the USA, our gear components are the highest quality available, and are superior to offshore, imported kits. If you're interested in checking out just how good WideGear can be or need info on just what pulley combo's right for your kind of riding, then check out our gearing charts for answers to these commonly asked questions. You'll know ahead of time whether or not you need more gear or engine speed reduction, depending on your riding style.

SportGear™ and TwistGear® are trademarks of Johnson Engineering, Inc. Buell™, Dyna™, and Sportster™ are trademarks of the Harley-Davidson Motor Company. No affiliation with the Harley-Davidson Motor Company is implied or inferred.