Tag: leading link forks

Motorcycle Comfort and Safety

In designing a motorcycle there are several critical measurements that must first be finalized.

From watching customers decide which bike to buy, over the years, and from my own riding experience, the first and most important measurement to be locked in should be the seat height. After all, these machines should be built to fit people and people come with various inseam lengths, within certain ranges.

Currently, go anywhere all-purpose motorcycles called “adventure bikes” seem to be built for people who are in the 32 through 36-inch inseam range. There simply are no all-purpose motorcycles built for the 25 inch through 30-inch inseam range.

In reality what this means is approximately 60% of the world’s population can’t buy a “go anywhere adventure type motorcycle” to fit their body at any price. The only motorcycles available to them are some of the cruiser models and motorcycles built for young children to learn on.

To put this into perspective the adventure type bike is the popular two-wheel equivalent of the crossover style car that’s the biggest seller now in the automotive market.

It seems to me there is a huge chunk of business available to the company who takes the time to develop a line of go-anywhere motorcycles to fit the 25-inch through 30-inch inseam range of people. With all the millions of short people, which includes most females and a huge percentage of males available as customers, that market could be larger than the current motorcycle market we see now.

Some original design work will have to be done for sure, but the prize available in the end will be a whole new market for motorcycles every bit as large as the current market or larger.

To see if you would be a customer in this new market segment simply measure your inseam length.

It’s an often ignored safety issue, but the closer you can come to being able to touch the ground flat-footed at stops or in panic situations, the more control you have over your motorcycle.

My motorcycle passion has always been in trail riding and off-highway competition. To do that with my 27-inch inseam length, I’ve always had to build my own special motorcycle frames with components from various bikes to achieve the control and comfort I desired. One thing I learned early on, was that the maximum suspension travel I could use with my inseam length was 7 inches.

My effort then became to experiment with various 7-inch travel forks to see which ones gave me the control, handling, comfort and safety trail riding and off-road racing required, with my inseam length. The best handling and smoothest riding ones were leading link forks from Dot, Greeves and Sachs.

Both Dot and Greeves had relatively useless Villiers engines, so I simply used their forks, which were great, with much higher tech engines from other makers in my modified 29-inch seat height frames. With about 2 inches of suspension sag, as my weight found the seat, I could put my feet flat on the ground. With my race clothes on, and ready to ride, my weight was right in the 160-pound range so it didn’t take huge engines to make me very competitive overall.

So there I was racing through the forest, or the desert, in relative comfort as most of those around me were wearing themselves out on motorcycles that didn’t fit them and certainly didn’t ride as good as mine.

~Herb Uhl

Mechanical Problem with the Telescopic Motorcycle Fork

The telescopic fork is being asked to do a job that physics and common sense won’t allow it to do no matter how many thousands of dollars they continue to throw at its development. It has already had millions wasted on trying to perfect it.

Leading link forksHere’s the problem. – – When you ride it forward against a bump the movable part of the fork, whether it is a male or female slider, is violently shoved straight back towards the motorcycle, and only after that happens does it start to slide upward on or in its tubes that are attached to the handlebars. Therefore you have one set of tubes prying against the other set of tubes as they try to slide in or on each other. No matter what is done to make them more slippery there is no way those basic facts of mechanical action can be changed.

Even though the telescopic fork looks cool and simple and the effect is not noticed much when you’re sitting still and working your beautiful smooth front fork up and down, it does not have the same effect when you’re riding the bike and run into a bump.

That is why it takes 12 or 14 inches of up-and-down travel to get a good ride over unimproved terrain with telescopic forks.

There is absolutely nothing wrong with the shock spring units being made to telescope, it is simply that they have to be attached in such a way that impacts do not hit them directly and put them in any kind of a bind.

The answer of course is to use some kind of a hinged unit that separates the impact from the shock spring unit just like on the modern car. There have been many types of hinged front suspensions used on motorcycle forks. In fact one of the first multi-cylinder motorcycles had one used on it in 1895.

In one form or another leading or trailing link suspensions, as they are called, have been used on one model or another by most motorcycle manufacturers. Up until now these link type suspensions have been slightly heavier than a telescopic fork. Now titanium can be used in their manufacture and affect a 20% weight savings, finally making them completely practical, and perhaps slightly lighter than equivalent telescopic forks. So 121 years later technology has finally caught up with the design and they are practical for top-of-the-line motorcycles.

The practical results of changing over to a leading link design are;

1. No suspension binding either on impact or braking.

2. Better and safer braking because the front of the bike doesn’t dive during braking thereby taking weight off the rear wheel.

3. A much smoother ride needing only one-half of the travel because binding doesn’t compromise shock action.

4. Much longer life out of spring shock units.

5. Because of the way the impacts are absorbed there is less stress on the frame of the motorcycle allowing for overall lighter weight and longer service life.

6. A lower seat height with way better comfort and safety. It usually only takes one good ride to make you happy you made the leading link suspension choice.

7. In essence the leading link fork has an action similar to that used on today’s supercars and they are constantly being tested at speeds of over 200 mph.

Is there a downside to using the leading link type front fork? Yes there is, you’ll have to get used to the fork looking a little bit different.

I’ve personally raced several thousands of off-highway miles on leading link front fork equipped motorcycles and I have been able to perform well above my skill level because of their forgiving nature.

Herb Uhl

typical leading link fork motorcycle technology