The Softy Goes Rigid | V-Twin Hardtail on a Softail Frame - Hot Bike Magazine

Tech In Depth

The Softy Goes Rigid | V-Twin Hardtail on a Softail Frame - Hot Bike Magazine

The donor frame: a typical ’99 back Softail.

The donor frame: a typical ’99 back Softail.

01. Here’s the hardtail section from V-Twin MFG. PN 51-0947, ($271.29) for up to a 200-series tire with belt. A narrower 9-inch-wide hardtail is also available.

02. The lower splice point would be in this general area.

03. Likewise, the upper splice point would be just behind the seat area gusset plate.

04. Before cutting the Softail swingarm pivot section off, lengthwise cuts were made in the tubing where the rear transmission mount meets the lower rails. This would make removing this mount easier after the rear section was cut off.

05. Next, to separate the swingarm section from the frame, Rich cut just in front of the uprights on each side of the lower rails…

06. …and both upper rails just behind the seatpost gusset plates.

07. There was no turning back now!

08. Two more quick cuts, and the rear mount for the transmission separated from the old frame section.

09. The trans mount was cleaned up and set aside for reuse later.

10. Next, Rich squared up all the previous rail cuts to prepare them for splicing.

11. The new hardtail’s upper rails would need to be trimmed back some to mate at the right angle to the upper frame section. Rich marked the rails slightly longer than necessary, then “snuck up” on the proper fit by trimming and checking for the right alignment as he went.

12. When the proper fit was obtained, Rich held the upper part of the hardtail in alignment with the use of an improvised “turnbuckle” made out of mechanic’s wire and a bolt.

13. The lower rails of the Softail’s frame would need to be extended to mate up with the hardtail. Rich measured back 8 inches from the seatpost lower crossmount on each side and cut the rails back. More space was allowed between the final welds on the spacer to join both sections together.

14. All the tubing splice points were deburred inside and out, and all paint/coatings were removed approximately 1 inch back from the mating areas of the splices.

15. Here are the components needed to complete the splicing: a 1-1/2-inch long x 1-1/8-inch OD 1/8-inch wall DOM tubing spacer to go between the original rail and the hardtail section and an inner reinforcement slug.

16. Prior to final assembly and welding, all the various pieces and frame sections were cleaned and degreased inside and out with denatured alcohol to prevent anything on the tubing surfaces from contaminating the welds. Denatured alcohol cleans well, evaporates completely, and leaves no residues behind that could convert into dangerous gases while welding.

17. Rich stood the front frame section upright, then slid the lower rails of the hardtail with the related pieces into place.

18. How do you get the slugs in place if both sections are at an angle? The slugs were slid into the hardtail’s rails and held in place by hand until the sections were positioned. The slugs were then allowed to slide down the tubing into place with a little help from a deadblow hammer.

19. Using two ratcheting tiedown straps (one along the backbone to the seat crosstube, and one from the back axle to the seatpost) to hold both sections together and into alignment, the plug welds were done, checking for square and alignment after each weld.

20. Here’s the first two plug welds up top. The trick is to get the slug to melt first, then fill the hole as you move to the top surface. Rich’s preference is to use a MIG welder for the plug welding.

21. Here we see the plug welds completed on the bottom rail’s splice areas. Next up would be the final joint seam welding.

22. Using a TIG for all the seam welds, Rich used the same sequence of welding as the plug welds, skipping from the top to the bottom sections as each seam was completed, to minimize any heat warping that might occur. MIG welding is totally acceptable here as well.

23. Using the OEM transmission plate as a locater, Rich welded in the rear transmission mount last. After cleanup on the rear mount, the pointer shows the small spacer that was required on the L/H side to locate the mount in the right position for welding.

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For years, owners of Ironhead (and now Evo) Sportsters and four-speed Big Twin motorcycles have used hardtail rear frame sections to give their bikes the essential rigid frame “chopper” profile. Hardtailing a bike you now own has its benefits, the biggest being cash outlay—adding a hardtail section usually runs between a third to half of a full frame replacement, cost-wise. Second, a hardtail section enables you to avoid the hassles of re-registration and insurance that go along with a full frame replacement: you retain your original frame numbers and title.

For the most part though, Softail owners don’t feel that “rigifying” their bikes is an option, mainly because there isn’t a specific hardtail offering for their OEM frames. What they fail to realize is that their Softie frame design isn’t that far removed from their four-speed big-twin framed predecessors, and hardtail sections offered for the Shovel swingarm frame are totally adaptable to the Softie and can be accomplished without jumping through a lot of fabrication hoops. With a few simple tricks, the conversion doesn’t really take much more work than it would on a Shovel frame. Follow along as Irish Rich of Shamrock Fabrication performs the surgery and discovers how relatively straightforward and easy this conversion can be. HB

24. Here we have the finished frame. The line from the neck down to the rear axle plates is not that different than most rigid frames, and with all your components in place, it would be hard at first glance to know your original frame was indeed a Softail.


V-Twin Manufacturing
(888) 316-1994 |

Shamrock Fabrication
(303) 465-4839 |