Bike Front End Swap – Prerequisites

In order to convert bike from conventional to inverted front end one must ask few questions:

• Will the new fork fit?
• Will the new fork change bike’s geometry and if so in which way?
• What happens to steering bar?
• Will the old wheel fit without problems?
• What happens to fender?
• What happens to front brakes?

Will the new fork fit?

If you have a naked bike, the answer is most likely yes — it will fit. However, if the bike has any sort of fairing that shrouds the fork, chances are that you’ll have to do some measurements and pay good attention to clearances.

Will the new fork change bike’s geometry?

When talking about geometry in terms of front end, multiple variables are in question: wheel size (tyre circumference), frame head angle, fork length and fork offset from steering axis. By varying these parameters, two important values can get tuned: trail and rake.

Assuming that we want to maintain original geometry and that wheel will remain the same, basically the only thing that we need to ensure is that fork offset remains the same and that forks are long enough so that we can slide them in place where they need to be.

What happens to steering bar?

Replacing motorcycle front sometimes means replacing triple tree — either one or both clamps. In case of motorcycles with steering bar replacing top clamp usually means that the new one will not have bar clamps in the same place where the old one had it and serrated pieces of steering bar that need to be clamped will not be in a proper position. If you want to do everything by the book, you will want to consider acquiring a steering bar that came originally with the new clamp.

Motorcycles with clip-ons can be less problematic especially if the old and new fork legs are of the same diameter. You need to pay attention to the fork length and that enough of it will remain for clip-ons after setting a desired bike’s geometry.

Will the old wheel fit?

There are really only two answers: either it will or it won’t. If it won’t then it’s a bummer and a really weird situation because upgrading usually means bigger components with more clearance.

On the flip side unless it is a perfect match, old wheel will probably be narrow which means that a set of collars will need to be turned on a lathe to keep the wheel centred. Also disc rotors could present an issue depending on the calliper mounting situation with a new fork.

What happens to fender?

Bigger and/or substantially different forks usually require new fender that was designed for them in the first place. If the difference between old and new fender is not big, machining a set of brackets or adapters might be more feasible option.

What about brakes?

This also can range from very simple to complex question. Depending on the calliper mounting solution on a new fork old callipers might work. They might need a bit of adjusting with shims depending on where the rotors end up in a new set up.

Some bikes come with combined braking and have specific callipers where one of front callipers has two physically separate hydraulic chambers. Switching to fork which doesn’t support mounting old callipers could mean that you will need to delink brakes and forget about combined braking system. That could also render bike illegal in certain areas especially if the bike isn’t equipped with ABS.