Springer-Fork upgrade, the Juicer way

If you're like me, you think that the old-school springer forks look cool. A hundred years ago forks of this overall design were seen on on a lot of cool old brands like Excelsior or this Cleveland;


The forks we can get now that look like this are handsome, light, handle bumps pretty good, but are lousy in a turn. I learned this the hard-way while racing at Grange earlier this year. The fork did a poor job of keeping the wheel in line when facing lateral pressure (such as when banking) or even turning the neck when parked! Why is this the case? Well it appears to be because there is too-much slop, too many ways for the parts to shift in the XY plane, and twist about the X-axis.


I'm not willing to walk away from these forks. Let's see if they can be improved with a bit of modification.

Old and worn, or cheaper forks may have have an enlarged hole where the center-screw rubs inside the pinched part of the larger, curved tubing which also results in play about the X axis. Also, because there are four floating fork-legs with slotted holes the axle and the fork crown do a poor job of preventing the fork from paralellagramming or twisting opposite ways on the left and right sides. To eliminate the twist I added a bit of 7/8" fish-mouthed tubing below the center-screw spot, checking to make sure it had clearance between the bottom of the steerer and my 24" tires (there may not be room to do this if you are running 26" wheels).

Okay, that got rid of the twist, now what about the bored out center-screw holes? I found that 1/2" tubing (the kind with the red paint on the ends that is available at the hardware store) is a good fit over the 3/8" center-screw. I wanted the fork to fit over 3" tires, so I welded a short segment of the tubing over the right center-screw hole and purchased a longer, heavy-duty 3/8" bolt. This also makes room for your disk-brake on the left side, but can affect the tracking/balance of your bike by shifting the front wheel to the right. If I was not going oversize with the tires or running a disk-brake, a better way might be to drill the holes out to 1/2" and set the tubing in there flush before welding. Also, because I am making the entire fork wider, I will now have to mount the top of the legs to the outside of the crown instead of the inside.

Already the fork is a lot stiffer, but to keep the floating legs from floating, I welded them together so they are not able to slide around in their slots. This is also the time to weld on your disk-brake bracket.

I still think there is a chance the fork could parallelagram, because, just like a card-house, it needs sheer-wall. To give it some, I cut an x-shape to weld to the thinner fork-legs on front. This can be thin-guage metal because it is doing the job diagonal cables do on your gate; they only have to be strong when pulled.


This bit of shear-wall makes a useful spot to mount something on your fork. How about a horn?



Or maybe a light?



So this beefed-up springer is what's going on my production-model Juicers, but will it survive the punishment of the gridiron? We'll see the next time Team Juicer hits the track.

And the answer is NO, not ready for primetime! The reason why is that I did not give sufficient attention to WHEEL RETENTION. What good is a stiffened fork if your wheel falls off? Because I made the fork more ridgid and the springers have closed ends, I have been using a skewer mounted axle. This worked fine for about 50 miles, but eventually worked itself loose while giving test-rides in the most prestigious of company. My wheel stayed on, but it produced a frightening wobble. This is not good enough for the street, let alone the racetrack- just ask Chase who lost his wheel at the Bairdco race last month.


Can you spot three things wrong with this picture?

The culprit, in my estimation, was poor purchase of the axle-nuts resulting in a splayed right fork end. The remedy will be to address both issues; switch to a bolt on axle and rehab the fork-tips.

First to eliminate the splay. The pressed ends of the forks lack the geometric advantage of their former cylindrical shape. When push came to shove, the left side fared well due to the extra support of the disk-brake mount, but the right side suffered a slight bend. So my remedy was to sleeve a piece of steel rod into the narrow tubes. Key-hole welds are de-regeur in this situation.



This picture illustrates the problem of poor purchase of the axle-nuts as well. You can see the beveled surface of the pressed tips only bite the axle nuts at the high points. To get maximum purchase, these areas have to be both flat and parallel.



With a bolt on axle, suddenly there is no excuse for thin dropouts, so I am beefing up the right tip with some flat plate. Next time around I'll slot this piece into some heavier-wieght tubing rather than butt-ending it into a rod.



On the other side, I added a bead to the intersection to increase the surface area, then ground it flat. Finally I added some well named "wheel retainers" to each side as a failsafe.



Whew! Hopefully that does it, because I don't think this turd can handle anymore polish. Although ideally I would like to race-test any product I foist on the public, the suspension makes it more of a road-fork. In any case, for the next draft of the Juicer Springer I will probably replace the skinny tubing with heavier material I pinch myself, and size the disk brake for a 180mm rotor.

dracothered said:

Ok what about a plate welded from the main fork tubes to the second tubes and in between the two plates weld a cross tube so it will clear the tire on 26" wheel setups? Also weld a sleeve in where the pivot bolt goes though the main fork tubes with a washer also welded on each side to beef up this area. Then do the other mods.

Click to expand...

I'm with you on the sleeve idea. That will eliminate a lot of play. The plates you describe will accomplish what I did by welding the ends of the fork together, but instead of a cross-tube, I recommend another plate or some diagonal tubes in an X to resist paralellagramming in the XY plane.



...lotsa ways to skin this cat.