Toe in question

Hi:

I will throw my 2 cents worth in here. What you have done so far is good (the 33% on the lead may be a little generous as you indicated.) Less than 1 inch in the toe in is a good place to start.  Your combination bike and sidecar is pretty right on - light sidecar - small bike. The real proof is  - can you make the rig go straight down the road with minimal pressure on the handlebars.  It is pretty much - "make an adjustment and ride it".  If it is good - leave it alone.  If not make another adjustment.  There is much material on our forum on mounting and adjusting under the technical section.  Go there and pick those brains.

Will Short

USCA Ex-president

You really need to reduce your wheel lead. This will steer hard, wear tires quickly and be very hard at best to deal with a head shake. 

Here is a link to instructions as to how to align the sidecar, note that the bikes suspension should be compressed to where it will be with your weight on the bike. http://www.dmcsidecars.com/basic-sidecar-installation-instructions/

You have to much toe in. Your sidecar has a fairly skinny tire and your bike is also fairly short. We usually do not go as high as 1 inch unless it has an automotive wheel and is a longer bike. As we are measuring over the length of the bike, 1 inch toe on a long bike is much less toe then it would be on a shorter bike if we were measuring the angle as with the longer bike we are measuring over a greater distance, the number needs to be higher. I would start off with about 5/8 inch toe.

One issue you may be having getting things set right is placement of the lower mounts. If the lower rear mount is higher off the ground then the lower front mount, when ever you lean it out to fix a pull to the right, you end up toeing it out causing more of a pull to the left. Ideally the mounts should be the same distance off of the ground such that a change in lean out has no effect on toe. They should also be spread apart as far as possible. Your main frame section is quite short. Your lower mounts could be as little as about 7 inches apart. Further apart is always better.

I have only mounted one sidecar onto a 454ltd, This was about 20 years ago for the Evergreen safety council for use on the training range. They finally replaced this bike about a year ago. I have no photo's however what I would have done for the lower rear mount is make a sub frame, bracket, mount or what ever you wish to call it that replaced the center stand then went aft forming a triangle allowing the lower rear to be behind the main frame of the bike and much lower then if you went to the main frame. This mount would have also had a support going up to the rear foot peg.

Another thing that some people some times miss with a sidecar this light you may be able to get it to work ok with totally wrong wheel lead and toe but with high tire wear, until you add a passenger in the sidecar. With a passenger in the sidecar, now the sidecars tire can get some traction such that if things are not correct you may find that you now have a pull some times even to the left as with to much wheel lead and now having traction the sidecars wheel has more effect. Or in other words it is not simply skidding along.

If you want to get the most enjoyment out of the rig, take the time, start over get your wheel lead correct even if this means you have to make some parts or have them made. (we have nothing for your bike) 

If this is spirit eagle the front lower mount will thread into the frame and the lower rear mount will be a strut like the upper struts mounted with a crude square clamp around the 1 inch tube frame. When we have done these in the past we weld in two cross tubes to stiffen the frame and as they would be slotted with pinch clamps we would also convert over to "boss and clamp" type lower mounts. We could help you with these parts if this is the route you wish to go. We would need to know the distance between the frame rails. You can get an idea of why we would do this at this link http://www.dmcsidecars.com/the-result-of-improper-sidecar-mounting-and-the-proper-fix/

Moving your forks up in the clamps does lower trail which would lower steering effort. 

If you want to post some photo's of your mounts my self and others can critique them for you.

Good luck, let me know if we can be of help.

Jay G
DMC sidecars

www.dmcsidecars.com

866-638-1793

Hours Monday - Thursday 6-4:30

It's important to remember that "rules of thumb" are seldom even good starting places because your rig isn't exactly like my rig and your driving isn't like mine either.  That said, "What else have you got?". 

As Jay pointed out, there is a big difference between rigs with longer or shorter wheel bases.  There is also a huge difference in exactly where folks measure their toe-in.  If you measure right that the leading edge of the front wheel you will get a much smaller measurement than you would if you measure three feet further out.  That's why we should really talk about toe-in in terms of angles [except that's a pain to figure out].  BTW, measuring at a point that yields a larger number makes it easier to make small changes.  Think about trying to add a 1/8th of an inch adjustment to a one inch measurement and how much easier and more accurate it would be to add one inch adjustment to an eight inch measurement, it achieves the same the same net change.  Gross changes are often more accurate than miniscule ones. In the OLD BMW sidecar mounting instructions from the 1950's they say you should measure at the back axle and a point one meter in front of an imaginary line dropped from the leading edge of the front tire.

Too much toe-in is rarely felt as an issue in driving, it usually shows in tire wear, particular on high performance rigs.  Failure to go straight down the road by pulling to one side or the other is more likely to be a lean out issue.

What ever you do, as you make your changes, mark where you start so you can return to that point if things don't improve and after you find a good setting, record it in your notes in a way you can check it.  That goes for all the settings, lean out, toe-in, tire pressure, weight distribution, etc.  Mounts [particularly clamp mounts] can twist and move as you ride and you don't notice it until you realize that the rig isn't handling as well as it used to.

Good luck and keep asking questions.  Every sidecar driver wants to see more sidecar drivers!

A

Thank you all for your great info and advice. As for changing the lead, that's not going to be easy. Will have to completely change the lower mounts, probably have to have a sub frame built. Maybe next spring... Right now the lower mounts are pretty close to the same height, 4 1/2" front and 4 1/4 " rear and 18" apart on the bike frame with a triangulated front bracket which grabs both sides of the lower bike frame and connects the front mount of the side car frame which is 24 " between. 

As it is it's not bad at all, (not so much when I first started out) tracks pretty nice with no noticeable pull to either side but there is a bit of head wobble which I could live with but want to reduce as much as possible.  Also trying to figure out how/where to mount a stabilizer which I will put on after I get it as smooth as possible. This is mostly going to be a round town kind of thing, not comfortable enough for any major journeys... More tweaking this weekend!

Thanks again.

I'm unclear on 33% lead, what does that translate into inches of lead from the center of the bike rear axle to the center of the chair wheel axle? 9-11" would be a typical measurement. As to toe, I've run into a number of folks who are trying to fix a pull to the right (assuming the typical USA right-sided chair) with just toe. That won't work. Although 1" isn't terrible, 1/2" to 3/4" max would be better. How you deal with this is with lean-out. Assuming you're running motorcycle tires on the bike, that is -- you can offset the mass of the chair/frame and tendency to pull with lean-out. About 1 to 1.5 degrees measured on the rear wheel (preferably, a brake disk but across the tire is acceptable place to do this) lean away from the chair is a good place to start. Reason I mention motorcycle tires, being they have the round profile at the contact patch, as one can expect, a lean will essentially toss the bike in that direction; the entire theory of counter-steering a two-wheeled machine lives in that fact. Thus, a slight lean out puts what would equate into a perpetual counter-steer setup and will tend to want to pull the bike that way -- essentially zeroing out the opposite mass forces of the chair. I set lean-out with a cheapo digital level and THEN do toe-in. Think you'll find that you can significantly reduce your toe number doing it this way. Cheers.

I'm also confused by the idea of expressing lead in terms of percentage.  Remember how I hate "rules of thumb"?  Well the rule of thumb for sidecar wheel lead is that it should APPROXIMATE the diameter of the rear wheel.  So, an 18" rear wheel would suggest a sidecar axle that is about 9" forward of the rear bike axle.  More lead will increase the effort in turning toward the sidecar while less lead with decrease stability in turning away from the sidecar.  Sidecar racers generally run very little sidecar wheel lead... but they're sidecar racers and fast is more important than stable.

When you're doing all your aligning and measuring be sure that you have the suspension compressed as much as it would be when you're carrying a typical load [in the typical places, driver, passenger, etc.].  You can do this with out actually having the weight on the bike by having a helper use straps [trailer tie down straps work for me] to hold the suspension in place while the weight is actually on the bike.  It stays "compressed" so you can get to the connectors and make accurate measurements and changes.

If you use a steering damper it will increase your steering effort but not much if it's spec'ed correctly.  The picture below shows the attachment to the forks and the part you can't see goes to a sturdy place on the front diagonal mount arm or the sidecar frame, really any place that works for the geometry and doesn't move relative to the sidecar.

Sooo.... Major improvements! Head shake just about gone except when hitting some weird dips, bumps, etc. and it's not bad. Tracks pretty straight on most streets. Due to the soft suspension on the car the rig is definitely effected by the addition of a passenger but have it worked out nicely now. Dropped down the forks another 1/2" (now at 2 1/2") reduced the toe in to 3/8" and removed 20 lbs. When empty the preload on the rear shocks are on the highest setting and the car on lowest, with passenger car on highest and bike on lowest or somewhere in between depending on the weight of passenger. Don't have to worry about a very large passenger because they wouldn't want to get in this small seat anyway! Have about 1/8" lean out when empty and I can get it to stay pretty close by adjusting the preloads which works out pretty well. Running stock motorcycle tires at 40lbs. Thinking about adding a pinch of fork oil for better dampening up front. Should probably get a new shock/spring for the car,  it might be the original.

 The lead on this rig is 18" which is not ideal but I seem to be making it work (lots of tire scrub though). That was the best I could do with the mounts and hardware readily available and without making an entire sub chassis. That may be next years project? Not sure because I'm kinda liking it the way it is. Time will tell... 

Thanks for all your input!