Suspension

It matters!

Telescopic forks, if from the stock motorcycle, are designed primarily for loads inline with the fork tubes and the direction of travel. In a two wheel environment cornering loads are in line with the bikes travel due to the leaning of the bike in corners. The forces from bumps and holes are also encountered in a straight line to the forks. It also takes very little twisting force to turn a two wheel motorcycle.

When Telescopic forks are used in a three wheel environment, severe side loads that the forks are not designed to withstand are introduced when cornering. Also unless the front end geometry is changed to minimize trail, considerable additional twisting forces are introduced to the front forks while turning. Most of the twisting forces can be reduced with a steerite or similar triple tree modification, but the side loads from cornering G forces will remain. These side loads usually cause sticktion in the fork tubes when cornering that can hinder the suspension from responding properly to bumps, etc. while cornering. This is not to say they can't be used successfully whithin their limitations, just that there are limits to their performance.

Leading link downtubes are usually considerably stiffer then fork tubes and designed to handle the sideloads present in a non leaning three wheeler. The suspension action is smoother in corners as the forces are better handled by the bearings at the pivot points rather then two tubes sliding inside each other. Most leading link front ends have as a design feature the ability to adjust trail by changing the position of a couple bolts rather then changing the triple trees.

An interesting difference between the two is while braking the forks will dive and the leading links will rise. Not really an advantage to either but a difference.

There are several aftermarket forks that have been made by EML and others that are specifically designed for sidecars and are exempt from the general comments I made above about front forks.

Another style of front end used on high end rigs is cennter hub steering, similar in function to a strut front end from a car.

Thanks tkpincs. I have been debating the Ural Retro or the Tourist LX and the suspension on the Retro is telescopic and Tourist is leading link. I like both but that makes my decision easier, not to mention the price difference.

Originally written by RunAnDun on 3/9/2007 3:26 PM

Thanks tkpincs. I have been debating the Ural Retro or the Tourist LX and the suspension on the Retro is telescopic and Tourist is leading link. I like both but that makes my decision easier, not to mention the price difference.

I've driven a Ural with LL forks, and they steer hard!! compared to my earles fork on my /5 .

Originally written by Bob in Wis on 3/9/2007 4:33 PM

I've driven a Ural with LL forks, and they steer hard!! compared to my earles fork on my /5 .

Ease of steering all comes down to trail and how much it is reduced from stock. Too bad figures are not published more often. I can see why but it sure would allow some to make a decision easier,
Note that all leading links do not rise under braking. Some use a floating caliper mount that segregates braking force from the leading link swingarm.
Also just to cut down on confusion when a leading link is mentioned along wioth an earles fork they are in reality the same thing.

Does the Ural Leading link have an adjustment for trail?

Usually there are several holes the swingarm pivots can mount in. Large trail for solo use and small trail for sidecar use. To reduce trail with leading links the front wheel should be in the forward (increased wheelbase) position.

I don't know about the steering effort on the various urals, but effort = trail, not which type of suspension is in use.

If it has a steering dampners installed that can also add to steering effort.

The unit leading links, and probably many others can also adjust trail by where you place the top shock mount on the downtubes. This adjustment primarily is for ride height, but also has a modest effect on trail.

It would be good to hear from a ural owner about the front end adjustments as I've never played with one.

I do know with the Unit brand Leading links on my r100rt I can adjust all the way to zero trail if I want to, very easy steering, no self center ability.

So- why did the early '50s Beemers do so well with tlescopic forks?

Not enough horespower or traction with vintage tires to develop the cornering forces that are comon with today's bikes.

What was the trail on the /3 bmw's? It may have been less then todays bikes.

Ya got me. I do know the bikes were pretty darn low and they worked great either solo or with a Steib. I'm not used to new stuff, but I had 2 R67/2's (I forgot why they weren't /3, but they WERE 1952) and I think they made better SC rigs than the '60s models.

Urals are an anomaly. Both their leading link and "conventional" forks are set up for sidecar use. They are "apples and oranges" to the discussion of leading link versus conventional forks on other cycles. If you are specifically looking at a Ural, don't worry about it. If you are looking at any other brand, fork style will be an issue.

Sarge

Originally written by Uncle Ernie on 3/9/2007 10:26 PM

So- why did the early '50s Beemers do so well with tlescopic forks?

Did they?
remember earles was also available then..I have a '56 earles on my /5 bike.