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One of the many things that will screw you setting tow in on older HD's

We started aligning the car now that we have built a new mount to replace the one we broke.
This is on a 1988 police bagger with stock width 130/16 tires. The front is a continental and the rear is i an Dunlop E3.
While setting the toe in, I notice that the straight edge did not hit the front of the rear tire. We decided to check the chassis alignment because
it is adjustable on HD rubber mount frames. The chassis alignment was spot on.

Turns out, according to HD, the front tire is wider than the rear even though they are designated the same nominal width.
When we put a straight edge on both sides of the bike tires, there was equal gap to the rear tire on both sides on the front and back edges.
It may have been exaggerated because of the mixed brands of tires, but according to the manual the front is also wider with tires of the same brand.
A scrap of Plexiglas I had around made a good shim to correct for the difference. Without the shim the toe in measured, would have been a considerably different than the
actual.
On ours the difference is 3/16" per side. With 8 ft straight edges the error is substantial if it is not taken into account.

Joe
"Fight socialism buy a Ford"

Since many bikes have different width tires and wheels front and rear and also some misalignment , we always do the toe-in measurement using the rear wheel only.

Lonnie

Add to that the fact that some motorcycles, like BMW, have an intentional offset between front and rear wheel....

Best,

GTRider

There is a reason it says "expert" under your picture. It's because you approach these problems with knowledge and experience.
I'm short on both.

What you said implies:
If the front wheel is not in the same plane as the rear you would correct for it by turning the front end slightly? Probably without even realizing it.
Your toe in is relative to the rear wheel because it is not steerable?

I'm curious. Is it possible to compensate for the drag of the sidecar with just lean out? and have almost no toe out? or would you have it leaned out so far that you
would wear one side of the rear tire excessively?

We are trying 1 1/2 degrees lean-out with it loaded and 3/8" toe in to see how it handles today.

Some degree of toe in is needed to keep the two tire tracks from pulling away from each other, just as with an automobile.
With a singlewide sidecar 3/8" toe-in is a good tire saving measurement. Some wide track rigs will need more toe-in to avoid having to need excessive lean-out, which can be uncomfortable for the driver.
The optimum would be a setting which gives neutral steering, the best tire wear pattern and comfortable seating.

Lonnie

We just got back from the test ride.
Wife says it does not pull and the rig handles the best it has since we put it together.
Perfect!!
After having that mount fail I have a deeper respect for the forces on the connection points of a sidecar. I will be making frequent inspections. Probably take a look each time it goes out from now
on. That was a little too close. One pothole and we could have been done in.

Thanks for the help Lonnie.

Gt rider I was aware that HD offset the wheels on the K model and early iron head sportsters. I had no idea that BMW did it too.
Was it the early ones with the earls forks?

fastjoe - 7/2/2010 11:53 PM

Gt rider I was aware that HD offset the wheels on the K model and early iron head sportsters. I had no idea that BMW did it too.
Was it the early ones with the earls forks?

Can't speak to the early ones. Bought my first BMW in 1983 so every BMW I've owned has had the monolever/paralever rear end and they have all had an offset. The best rationale I've heard for it is that it's intended to offset the swingarm/driveshaft weight being all on one side of the bike, so that the bike doesn't have an inherent pull to left or right.

Best,

GTRider

If I'm correct, most Harleys have some offset for one reason or another. Using the rear wheel only is a good compromise.

So you are saying run the straight edge against the rear tire and don't worry about lining the straight edge up on the front tire and then do your measurements?

B-roadglide - 8/1/2010 12:41 AM

So you are saying run the straight edge against the rear tire and don't worry about lining the straight edge up on the front tire and then do your measurements?

Some of the later ones are built with left bias offset. It's shown in the Service Manual which I haven't got handy, The purpose of it is to counteract the weight of the primary drive components for balance when underway. It's very noticeable on Springer Softails with a 21" wheel, I'll have to look in the manual,

Nonetheless, if you can get a straight edge that is about 4" off of the floor and have it lie flat on the rear tire, you will be OK for a starting point for your sidecar setup. At any rate, using two 10' square tubes with 4" risers, I was able to lay it flat to the right of the wheels (looking forward).

Using my second long straight edge on the outside of the sidecar wheel, I set it at 3/4" toe with the bike set straight up. It's just fine. These settings are always subject to change, however, once you do a road test.

I use a dedicated 20' section of 1-1/4" square steel tubes with feet welded on each end to lift it up off of the floor. I cut it in half and used some scrap to make risers. I've only had to use it once.

Happy Trails!

gnm109, where do you take your measurment between the two strt. edges?

old iron - 8/1/2010 3:24 AM

gnm109, where do you take your measurment between the two strt. edges?

I use the method shown in the Harley sidecar manual. They suggest measuring the toe-in with the straightedge laid alongside of the front and rear bike tires to the left of the wheels on the outside of the bike. The other straight edge is as mentioned, alongside of the sidecar wheel. The straightedges need to be high enough so that they will contact both sides of each wheel. A 10' 2X4 would work, if it were straight. As I mentioned, I use square steel tubing with risers welded on to bring it up to the sdes of the wheels.

Unlike the picture shown below and for no good reason, I put my straightedge along the insides of tthe bike wheels. It's actually the same except the distance will be shorter. Note that the Harley-Davidson diagram makes no allowance for the possibility of tire offset. In actual practice, it's very likely negligible.

They show the measurement taken just ahead of the front tire of the bike across to the straight edge at a 90 degree angle and likewise at the rear tire at a 90 degree angle.

I assume you have a Harley but this method will work on any sidecar. If you have a harley, you need to get the manual (99485-06 or whatever the year of your bike might be)

Hope this helps. I tried out my new scanner. LOL.

From the Harley-Davidson Sidecar Manual...P/N 99485-06.

Photobucket

thanks for the help. I downloaded a manual but wasn't quite sure where to take the measurments exactly. I'll check my bike out and see what it is. It seems to be set good the way I have it, but I'm wondering. I just downloaded a pic of my bike and as you can see it's made up of alot of different stuff. (it's a 25+ year old swapmeet bike). On these old sidecar frames,I can't see how you set the toe because everything is hard mounted except the front S bar. I think on the newer frames you scew the lower monts in or out. I'll probably leave it because it runs so good, but just curiuse. thanks again.

old iron - 8/1/2010 9:03 AM

thanks for the help. I downloaded a manual but wasn't quite sure where to take the measurments exactly. I'll check my bike out and see what it is. It seems to be set good the way I have it, but I'm wondering. I just downloaded a pic of my bike and as you can see it's made up of alot of different stuff. (it's a 25+ year old swapmeet bike). On these old sidecar frames,I can't see how you set the toe because everything is hard mounted except the front S bar. I think on the newer frames you scew the lower monts in or out. I'll probably leave it because it runs so good, but just curiuse. thanks again.

Yes, I see that you have an older HD with an early CLE frame and tub. They are certainly good looking.

You're correct that there wasn't much if any adjustment for toe-in on those rigs. They are pretty much built in and set based on the design. I had a 1980 TLE on my former Shovelhead which had some adjustment on the rear mount. Remember, the early sidecars weren't really designed for high speed.

Hopefully your bike will pull straight down a normal road with minimal pull on a high crowned road. I just set mine according to the manual about 3 years ago when I got the sidecar and I haven't had to touch it since the first day - when it needed only one turn on the rear mount to bring it in.

GNM