The Missing Linkage

I rode this fork in the 90's. Linkage forks could be a good thing, if not a tad ugly.

So, there was a bit of a hullabaloo in the mtb community about this "new" design which features a linkage fork. Actually, it isn't anything new, or revolutionary. Linkage forks have been attempted and used in mountain biking since suspension became a "thing" back in the 90's.

My friend from So Cal, Grannygear, suggested that the "newest" incarnation of  this idea as shown recently could be miniaturized and employed as a gravel going fork. Actually, even that already exists. It is called the Lauf Grit fork, which doesn't use pivots, but it uses "leaf springs" which link together the two separate structures which make up the drop out and fork legs respectively. Lauf manages to eliminate pivots and a separate spring which a more "typical" linkage fork uses by making the links the springs. It is genius, and it seems to work. The negative here is that there is zero damping. Of course, with the short travel and higher frequency of bumps a gravel going bike would see, this is less of an issue than it is for a mountain bike.

An example of the German Answer "Kilo" linkage fork.

 Let's say we want damping though, well, then you get into pivots and a separate damper unit. Okay, but why? Why would you even want to put one of these ghastly contraptions on a bicycle?

Well, I happen to have some experience riding a linkage fork. I rode an AMP fork for a few years there on a couple of different bikes. In fact, I have two of these unicorns in my basement. Anyway, they did have a very good small bump compliance and steered really well even deep into their travel. There are reasons why that was.

While there have been, and are, many different types of these beasts, what is attractive here are two things. First; You can rid yourself of stiction- the term refers to the energy required to break free from/overcome the friction of bushings and seals on a stanchion sliding in uppers/shock can in a typical cylindrical, telescopic damper unit. (Suspension fork/rear shock) Linkage forks rely solely on pivots which are much freer to move, or as in the case of the Lauf, just any input overcoming the spring force will allow the wheel to move upward.

Secondly, linkage forks can be designed to control the axle path and can be designed to have "anti-dive" characteristics when applying the brake. Think "Split Pivot" for the front wheel, if "anti-dive" doesn't make sense.

Obviously, eight pivots and a damping unit are going to be susceptible to dirt and moisture and the damage those things can incur upon bushings and bearings. That's why most linkage forks put "the business end" of things where the fork crown is. That arrangement, well......actually anywhere you put linkage, is typically not a very attractive solution but it is an effective solution for bump absorption. Much more so than a telescopic suspension fork is, and generally speaking, lighter to boot.

A linkage fork wouldn't necessarily have to look ugly. Weird? Well.....yes.

In terms of gravel riding, a long travel of the wheel isn't a desirable trait, nor is it necessary. Many forks being positioned in this category feature 30mm of travel. That isn't much and wouldn't require much of a damper unit.

So, in my estimation, a fork like the recently shown mountain bike fork, with its frame altering design, is not at all necessary. A short linkage could be designed which would not only give the right amount of travel, but be aesthetically appealing as well. It may even be able to be made to be so compact that the fork could look nearly traditional. 

But then it could be argued that we don't need a suspension device at all. In fact, many would argue that a simple, rigid fork with an adequate amount of compliance will work with a voluminous tire to provide just the right amount of wheel movement without any unnecessary complexity. I happen to be one of those folks, and I think that many companies miss the boat on this when they spec these big section, beefy looking, unforgiving carbon fiber forks.

Many folks feel that carbon forks will damp vibrations. Really? If you own one of these beefy looking carbon forks you should check this out: When your front wheel impacts a road irregularity sometime, watch the fork blades. (Being extremely conscious of where and in what situation you do this, of course.) More often than not you will see the fork blades remain in plane, but the wheel moves backward a bit. What you are witnessing, most times, is a flex of the top and down tubes of your bike, not the fork blades themselves. This is because manufacturers are deathly afraid of fork failures, the industry testing standards are too stringent, and because of the manufacturers reliance on the fairy tale that carbon forks absorb road chatter. Now some do, but most don't on gravel bikes. 

That said, a smartly designed, short travel, tunable, good looking linkage fork with damping is possible, it just hasn't been done yet. If it ever is, I'll definitely want to try it out. It may just be the missing link between rigid forks and full on, traditional style suspension forks for gravel bikes. 
 

The Missing Linkage

I rode this fork in the 90's. Linkage forks could be a good thing, if not a tad ugly.

So, there was a bit of a hullabaloo in the mtb community about this "new" design which features a linkage fork. Actually, it isn't anything new, or revolutionary. Linkage forks have been attempted and used in mountain biking since suspension became a "thing" back in the 90's.

My friend from So Cal, Grannygear, suggested that the "newest" incarnation of  this idea as shown recently could be miniaturized and employed as a gravel going fork. Actually, even that already exists. It is called the Lauf Grit fork, which doesn't use pivots, but it uses "leaf springs" which link together the two separate structures which make up the drop out and fork legs respectively. Lauf manages to eliminate pivots and a separate spring which a more "typical" linkage fork uses by making the links the springs. It is genius, and it seems to work. The negative here is that there is zero damping. Of course, with the short travel and higher frequency of bumps a gravel going bike would see, this is less of an issue than it is for a mountain bike.

An example of the German Answer "Kilo" linkage fork.

 Let's say we want damping though, well, then you get into pivots and a separate damper unit. Okay, but why? Why would you even want to put one of these ghastly contraptions on a bicycle?

Well, I happen to have some experience riding a linkage fork. I rode an AMP fork for a few years there on a couple of different bikes. In fact, I have two of these unicorns in my basement. Anyway, they did have a very good small bump compliance and steered really well even deep into their travel. There are reasons why that was.

While there have been, and are, many different types of these beasts, what is attractive here are two things. First; You can rid yourself of stiction- the term refers to the energy required to break free from/overcome the friction of bushings and seals on a stanchion sliding in uppers/shock can in a typical cylindrical, telescopic damper unit. (Suspension fork/rear shock) Linkage forks rely solely on pivots which are much freer to move, or as in the case of the Lauf, just any input overcoming the spring force will allow the wheel to move upward.

Secondly, linkage forks can be designed to control the axle path and can be designed to have "anti-dive" characteristics when applying the brake. Think "Split Pivot" for the front wheel, if "anti-dive" doesn't make sense.

Obviously, eight pivots and a damping unit are going to be susceptible to dirt and moisture and the damage those things can incur upon bushings and bearings. That's why most linkage forks put "the business end" of things where the fork crown is. That arrangement, well......actually anywhere you put linkage, is typically not a very attractive solution but it is an effective solution for bump absorption. Much more so than a telescopic suspension fork is, and generally speaking, lighter to boot.

A linkage fork wouldn't necessarily have to look ugly. Weird? Well.....yes.

In terms of gravel riding, a long travel of the wheel isn't a desirable trait, nor is it necessary. Many forks being positioned in this category feature 30mm of travel. That isn't much and wouldn't require much of a damper unit.

So, in my estimation, a fork like the recently shown mountain bike fork, with its frame altering design, is not at all necessary. A short linkage could be designed which would not only give the right amount of travel, but be aesthetically appealing as well. It may even be able to be made to be so compact that the fork could look nearly traditional. 

But then it could be argued that we don't need a suspension device at all. In fact, many would argue that a simple, rigid fork with an adequate amount of compliance will work with a voluminous tire to provide just the right amount of wheel movement without any unnecessary complexity. I happen to be one of those folks, and I think that many companies miss the boat on this when they spec these big section, beefy looking, unforgiving carbon fiber forks.

Many folks feel that carbon forks will damp vibrations. Really? If you own one of these beefy looking carbon forks you should check this out: When your front wheel impacts a road irregularity sometime, watch the fork blades. (Being extremely conscious of where and in what situation you do this, of course.) More often than not you will see the fork blades remain in plane, but the wheel moves backward a bit. What you are witnessing, most times, is a flex of the top and down tubes of your bike, not the fork blades themselves. This is because manufacturers are deathly afraid of fork failures, the industry testing standards are too stringent, and because of the manufacturers reliance on the fairy tale that carbon forks absorb road chatter. Now some do, but most don't on gravel bikes. 

That said, a smartly designed, short travel, tunable, good looking linkage fork with damping is possible, it just hasn't been done yet. If it ever is, I'll definitely want to try it out. It may just be the missing link between rigid forks and full on, traditional style suspension forks for gravel bikes.