Tech Tip - Super Precision Fork Alignment

Sooner or later everyone has twisted the front end of their bike by taking an unscheduled soil sample or by playing pin ball with the trees. Besides the bars pointing off to the side, your front end might look something like this where the front wheel and the fender are out of alignment.

Shouldn't the front wheel and the fender line up?

Front wheel is crooked from a altercation with an imoveable object

On the trail, holding the front wheel against a tree while turning the bars can often straighten it out enough so you can kept riding comfortably.

When you get the bike back in the garage it’s always best to “reset” the front end after a crash event. A twisted front end will not work correctly as it will bind when the suspension compresses making the front suspension perform poorly. It’s also not very pleasing riding when your handlebars are crooked. 

I find it very annoying when I ride a bike that doesn’t ride straight. For some time I have felt that my trusty Husaberg FE450 was a bit out-of-wack, it seemed always pointed slightly to the right. It wasn’t enough to cause handling issues, but it seemed to be a problem when riding down the road. The bike has had a few hits with terra firma, so I could be possible the frame was tweaked slightly. I carefully measured the rear wheel to ensure it was tracking straight. BTW I used a laser level to get it to sub-millimeter alignment. It turns out that the alignment marks on the adjusters where bang on, some nothing bent there. Other careful measurements on the front wheel and forks also could not find anything misaligned. I then bought a used low-mileage Ducati Multistrada that obviously had never been down and was well maintained at the dealer. After riding it around I noticed it also seemed to pull slightly to the right. Then it dawned on me. The bikes aren’t crooked I am! I guess it’s time to get back to my chiropractor. Anyway, back to fork alignment.

There are a few ways to get everything line up and in its “happy place” where it’s meant to be (for your bike not your body). The simplest way to get everything aligned is to first get the front end of the bike off the ground. Loosen all the fork pinch bolt and axle pinch bolts to light finger tight just enough so they do not slide out of the triple clamps. Also loosen the front axle nut. Stand in front facing the bike with the wheel between your legs and lightly pull the handle bars left and right, let go and let everything settle in the middle. This usually works, but how do you know for sure everything is straight? Enter the Super Precision Fork Alignment Tool (SPFAT), or as it’s more commonly called, a sheet of glass.

Simply remove the front wheel and fork guard screws. Push the guards out of the way. Now you have the lower sliding portion of the forks fully exposed. Lay a properly sized sheet of glass on the front of the fork sliders. I cut a piece of an old glass shelf, but any piece of flat glass should work. You will quickly see if there is any twist at all in the fork setup if the glass does not lay flat on the fork sliders. Using this method you can get the front end bang on and back to factory spec straight.

Super Precision Fork Alignment Tool

Lay the sheet of glass on the front of the fork tubes.

This only takes a little longer to align your front end, but you can be guaranteed that everything is going to be exactly where it’s supposed to be. The bike will steer straight and the front suspension will works its best since it will not bind during full compression

Triple Tree Pinch Bolt

Loosen the pinch bolt to allow the triple clamps to align 

It may be necessary to loosen the top triple clamp pinch bolt at the steering stem if the triple clamps are out of alignment from a really big hit. Push and the fork lowers forward and back until they are straight and the plate of glass (the SPFAT) lays flat. Insert the front axle without the front wheel. It should go in with no problems. If it doesn't, the forks are still not in alignment. This may be because the forks are not even in the triple clamps, that is one is lower than the other. Check the disatance each fork tube is above the triple clamp and make sure they are equal.

Torque everything back down to the proper specification and you are good to go! 

Everything is flat now

The amazing SPFAT is now laying flat on the fork tubes. Forks are straight and aligned 

Make sure you use the correct torque on all the screws. Fork tubes and triple clamps on one of the areas that are very sensitive to over and under tightening. Over tightening can cause the thin fork tubes to crush or can cause the forks to bend rather than twist in the clamps during a crash. Not tight enough, and the forks can move in the clamps when you really don’t want them too, greatly hurting the handling and stability of the bike.

Pinch bolt torque spec

Torque spec is labeled on my Husaberg

Front Axle Tightening

While we are at it, I will also talk about the correct way to tighten your front axle. The axle nut clamps the front wheel to the fork, through the bearings and spacers by the axle. It clamped to only one fork tube. The other side "floats" and should be allowed to find its happy place before you snug up the lower pinch bolts on the fork slider.

Here is what I do. Make sure you apply a light coating of grease to the entire front axle to prevent it from corroding in place and to allow it to move freely in the wheel and fork tubes. Also make sure the axle pinch bolts are also loose. Slide the axle in and tighten the axle nut until the axle starts spinning. It should be snug at this point, but not tight enough. Snug up the pinch bolts on the side where the axle nut is and retighten the axle nut to the correct specification. If the axle is still spinning, tighten the pinch bolts a bit more, but don’t exceed the recommended torque.

Fork should move freely side to side

Fork should move freely left to right

At this point the axle should be tight but the fork leg opposite to axle nut still needs to be tightened. You will notice that the fork tube can move side to side slightly if you pull on it. If it doesn't you need to loosen up the pinch bolts more until the fork leg can move freely, or check to see that the fork height above the triple clamp is the same for each fork. If the fork is moving freely, give the fork a pull back and forth and let it settle where it wants to be, somewhere in the middle of the range of movement. Apply a bit of anti-seize to the bolt treads and tighten the pinch bolts to the required spec.

 

Bryan Kowalchuk

BKE Racing

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