Have you noticed those dirt bikes racing around on the tracks and trails while their forks are inverted? There is a clear reason:

Upside down front suspension forks on a dirt bike allow the front end to be stiffer. Riders using inverted forks are then able to have greater responsiveness in their steering and this leads to better cornering, as well as better handling in whoop sections. As a result, there is reduced stiction between the lower and upper halves of the fork.

There is a lot of engineering jargon and technical reasons why dirt bike riders choose to modify their dirt bikes like this, but Frontaer will try to keep things simple.

Fitting Dirt Bikes with Upside Down Forks

Having inverted forks has sound engineering principles, but do you really need it? Well, if you’re riding a dirt bike, then it really depends on your riding style. Most commonly you’ll find riders choosing to reverse their forks on their road motorcycles as opposed to dirt bikes.

If you’re the type that wants to win championships or take the lead in a recreational group ride, then you’re going to be pushing yourself behind the limits of your forks. This is when you’re going to move up from amateur to professional, and as a race bike, you’re going to want forks. The same can be said for adventure motorcycles who need to be stiffer in the front end to cater for the additional weight of camping gear and additional fuel.

The rigidity can far outweight the cost, but it still depends on your riding style and type of motorcycle, as well as your weight. For those who love to claim some airtime, the suspension lifecycle will be enhanced through inverting the forks in most cases.

To invert them, you can often get this done yourself or get a mechanic to go through the process. This will cost you $200 or if you do it yourself, 2 to 3 hours of your time on the weekend.

Disadvantages of Inverted Forks

While many sing the praises of inverted forks, and they certainly do have their advantages, there are some downsides too. This is why you won’t see them on most dirt bikes, despite the riders knowing of their upsides.

The disadvantages include:

1. Challenging to Service. If you’re riding often and clocking up the miles, then you’ll be servicing your dirt bike just as often. The services on the fork seals will be challenging, especially as you won’t have a drain on your upside down fork. How are you going to release the oil? Certainly you’re going to need some assistance there and mechanics themselves have a tough time with this task.
2. A Hazard to Braking Systems. When your fork seals let themselves go, then you can have a genuine issue on your hands. With upright forks, a leaking fork seal isn’t too hazardous and you can ride it out until you get back to the trail head or finish your race since gravity is on your side. With a USD fork, this is very much a case of gravity working against you. Given the location of the fork seal (directly above the front brake assembly), all that fluid is most likely going to end up on your front pads and tyre.
3. The upfront cost. To transfer from upright to inverted front suspension forks requires time and patience, with some extra help if you’re not mechanically inclined. If you’re not happy with the handling or the dangers that it poses, then you’ll spend additional time reverting it back.

Now – don’t let us scare you here. Thousands of dirt bike riders would only get behind the handlebars if their forks were inverted already given the advantages.

Closing Thoughts

You really have to weigh up the cost. It’s very debatable among the dirt bike riding groups on Facebook, but one thing is for sure – they certainly do make your suspension a little tougher but aren’t without the risks.

Have you been curious about the future of dirt bikes and fitting a turbo on to the engine? Sounds exciting, but why haven’t they done it?

Well, our findings over the last 10 years are quite straight forward.

Dirt bikes don’t need turbo chargers in order to perform well and often perform worse with the rear tire spinning too aggressively for the dirt. It’s also not commercially viable for manufacturers like Yamaha, KTM and Honda to fit turbos on to their dirt bikes, even for motocross or enduro racing. There are some prototypes and home-made versions with turbo-chargers, but nothing has developed in the mainstream market.

Many riders get too excited about the power prospects and don’t realize that their machine is fast enough already. If you don’t have enough power, the best way to achieve these outputs is to actually go up in engine size or to switch to a race-ready manufacturer like KTM.

Turbo-Charged Dirt Bikes

Fitting a turbo on a dirt bike just simply isn’t something that you need. Dirt bikes just don’t have the space capacity to get a turbo fitted, unlike the engine bay of a car. Space really is at a premium there and you’d have to reduce your fuel tank size among other things to even stand a chance.

We’ll also add in the fact that dirt bike turbos also weigh about 100lbs or 30kgs. That’s a lot of weight already for a dirt bike to haul around. So any power gains you’re looking to achieve would mostly be taken up by this additional weight, as well as the lack of space availability.

Probably the most common reason why this doesn’t work out well for the rider is the crazy amount of torque. It’s much like electric dirt bikes where their torque can be so excessive in that you simply lose traction. If your goal is to increase your acceleration speeds, then these gains may not eventuate with a turbo as you simply can’t get enough weight on that rear tire to keep it from breaking ground.

AMA and Motocross Rules

The American Motorcyclist Association Motocross Division is unlikely to ever approve the notion of turbo-charged dirt bikes in events. Generally, once something has sudden successful time in any racing season, that same thing is rolled out into mainstream dirt bikes through stores across the country.

Thus, the biggest lead in taking these mainstream is also the biggest hindrance. Yet that hindrance is justified for the reasons outlined above – it hasn’t been done because it isn’t feasible commercially at scale. If KTM or Yamaha saw a future here, then they’d invest a few million which they haven’t yet. That’s a tell-tale sign.

Dirt bikes in both the recreational and competitive landscape are built for linear power delivery. Turbos aren’t linear and thus, riders would be frustrated pretty quickly in the constant breaking of traction. Yep, we’ve said that twice now.

In Summary

You’re unlikely to ever see turbo dirt bikes in a commercial sense anytime soon. Yet it isn’t actually wishful thinking here. Go on YouTube and you’ll find some good examples. If you did want this done to your dirt bike, then some service operations do exis.

Then again, you can find some used dirt bikes with turbo models on Craigslist and Gumtree, but the gains from these machines are questionable. Most commonly, the rider/owner has regretted their decision.

As they are, dirt bikes do already run exceptionally well, with 4-strokes coming a long way in the last 10 years to become the bike of choice for many motocross riders. With electric dirt bikes being the way of the future, we naturally aspirated dirt bikes continuing to shine until the lights of such factories are switched off.