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Wheel offset, reason, choices?
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BruceinHouston
Posted 11/9/2005 3:13 PM (#11444)
Subject: Wheel offset, reason, choices?


0
Location: Houston, TX
"Everyone" says the sidecar wheel needs to be offset a few inches forward from the bike's rear wheel. Two inches? 10 inches? Does it matter much?

Well, exactly what are we trying to accomplish here?

Hmmm, is this a center of gravity issue, where I am trying to get the loaded sidecar's weight center (say, about over the sidecar wheel) in line with the bike's loaded center, for tracking/stability? Just a guess.

Thanks in advance!
Bruce


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Hack'n
Posted 11/9/2005 3:31 PM (#11445 - in reply to #11444)
Subject: RE: Wheel offset, reason, choices?



Expert

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Location: Boise, Idaho
Read some of the stuff in the "Rig setup" thread.

Lonnie
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claude #3563
Posted 11/9/2005 7:41 PM (#11448 - in reply to #11445)
Subject: RE: Wheel offset, reason, choices?



Expert

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Location: Middleburg, Pa
That thread is pretty long but there is some good info there. Read Hal Kendall's response late in the discussion it is good. Hal also lives down Houston way. You can download his instructional material right here at sidecar.com for free. Click on the link included in my signature below.

Edited by claude #3563 11/9/2005 7:42 PM
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BruceinHouston
Posted 11/10/2005 9:53 AM (#11467 - in reply to #11445)
Subject: RE: Wheel offset, reason, choices?


0
Location: Houston, TX
Lonnie, Claude, thanks for the "lead."
It was indeed a very useful thread.
I have several fair maidens-- a spouse and several dogs who will be enchanted and, hopefully, safe.

Cheers
Bruce
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claude #3563
Posted 11/10/2005 10:24 AM (#11468 - in reply to #11467)
Subject: RE: Wheel offset, reason, choices?



Expert

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Location: Middleburg, Pa
Sometimes our minds begin to play tricks on us. If you ever get confused about what lead does for you just think about trying to drive you family car with the right front wheel off of it
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Bob in Wis
Posted 11/10/2005 10:28 AM (#11469 - in reply to #11444)
Subject: RE: Wheel offset, reason, choices?



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great way to put it, Clawed.Im goin' out and try itwith my 4X4 truck.!!
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Reardan Tom
Posted 11/10/2005 4:08 PM (#11481 - in reply to #11469)
Subject: RE: Wheel offset, reason, choices?



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Location: Reardan, WA
I'll just saw a leg off the dining room chairs and see if they stand as a tripod....
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claude #3563
Posted 11/10/2005 11:12 PM (#11488 - in reply to #11481)
Subject: RE: Wheel offset, reason, choices?



Expert

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Location: Middleburg, Pa
If the legs are spaced evenly you will have a very stable chair. Many three legged chairs were built years ago due to the floors being uneven...so they say.
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Reardan Tom
Posted 11/11/2005 7:52 AM (#11491 - in reply to #11488)
Subject: RE: Wheel offset, reason, choices?



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Hi Claude, that was a very meager attempt at a humorous way to demonstrate the same thing as removing a tire from a four wheel vehicle that was so dumb I shouldn't have posted it. But... I used to build shop heaters with three legs because they'd always stand solidly on any surface. The last ones I built I had changed to two inverted T legs. Still have the one I built that we heated our house with for a good number of years. I'll install it in the shop we're building over at the farm. OK, lets go talk about sidecars....
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hal77079
Posted 11/11/2005 10:49 AM (#11493 - in reply to #11444)
Subject: RE: Wheel offset, reason, choices?


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Location: Houston, TX
The sidecar wheel is offset forward by about 8 to 10 inches primarily to counteract forces on left hand turning. This is a compromise, as are all things in sidecaring. If too little, the sidecar nose would tip into the ground on hard sharp left-handers. If too great there would be too much tire scruffing on slow turning for both right hand and left hand turns, and especially on fast left hand turns. On slow right hand turns the sidecar wheel might actually revolve backwards.

Nothing to do with tracking or the CoG, except indirectly. It is basically a steering issue and the stability when turning.

It was NOT an issue in olden days when the lead was set at ZERO because the ethic at the time was to come to an ALMOST COMPLETE DEAD STOP when turning, and to NEVER ALLOW the sidecar wheel to LIFT off the ground, so the steering was easy and there was never any sidecar tire scruffing!

TODAY, we are not content with this but are pushing the envelope as far as we can, often much further than we can do so safely!

Slow down when turning is always good practice!

Edited by hal77079 11/11/2005 10:54 AM
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Posted 11/17/2005 5:48 AM (#11626 - in reply to #11444)
Subject: RE: Wheel offset, reason, choices?


Just got back my rig and it doesn't feel right. Installed a motorvation spyder side car on HD haritage springer. Front in wobles at start, and very stiff when moving. Side car tire about 20" forward of bike rear tire.
Any suggestions.
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claude #3563
Posted 11/17/2005 7:15 AM (#11633 - in reply to #11626)
Subject: RE: Wheel offset, reason, choices?



Expert

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Location: Middleburg, Pa
Who installed it? Typically lead is 8 or 10 inched give or take a little. If your 20" is an axle to axle measurement you surely have too much lead.
The wobble is not uncommon but it may be able to be adjusted out. If not you may jest get used to it as many rigs do this. You can also install a steering dampner.
Hard steering is due to the solo trail spec on the bike. It can also be associated with a lot of lead as I think you have.
One thing at a time. I woudl check your lead first and go from there.
Too much lead is like trying to drive the family car with one wheel straight ahead and the other one doing the steering.

Edited by claude #3563 11/17/2005 7:17 AM
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hal77079
Posted 11/17/2005 7:38 AM (#11635 - in reply to #11626)
Subject: RE: Wheel offset, reason, choices?


Veteran

Posts: 216
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Location: Houston, TX
Agree 100% with Claude. Only dirt track bikes set up for the speedway or bikes set up for handicapped with the driver in the sidecar have a lead like you have. Normal for street is 8 to 10 inches. You must have some but too much will cause hard scrubbing of tires when turning, especially to left. That might take some major re-engineering to get right.

The other cause is a large trail trail - normal unless you have had the front end re-worked to have it reduced. Normal trail for solo bikes is 4 to 5 inches. Foe sidecar work, 2 to 3 inches is good.

And a damper is usually required for wobbles. I prefer the friction type but most use hydraulic. Beware that too much damping is as bad as none or too little. Keep a firm grip on the bars at all times and do not allow a wobble to escalate. Normally, they can be kept under control. If allowed to escalate they can turn into a tank slapper!
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claude #3563
Posted 11/17/2005 8:12 AM (#11636 - in reply to #11635)
Subject: RE: Wheel offset, reason, choices?



Expert

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Location: Middleburg, Pa
Keep in mind that the 8 to 10 inches is not cast in stone. I almost wish we talked in terms of percentage of the bike's wheel base. Some bikes are much shorter than others so it is hard to compare apples to apples in many discussions.

Dampners? I do not like them and typically will deal with the wobble that is so common at a given speed by simply holding onto the bars if at all possible or practical. This is not to say that some bikes do not need them. It is so common to see a new sidecarist install a dampner when it isn't needed only because of a very slight wobble. Before going to a dampner be sure to tighten steering head bearings, play with tire pressue, setup etc to see if it helps. I just mopunted a BMW to A Dnper and it had a pretty bad slow speed wobble. It could be ridden that way but for a new sidecarist I felt it would be a little bit alarming. I played with tire pressure but did not get around to messing with the steering head bearings. I went ahead installed a dampner on it from inventory. He is riding the rig now and loving it but will soon remove the dampner and play with the steering head bearings. If this fixes the problem I will get the dampner back from him.
Dampners will also curtail the self cetering effect on many bikes.

Edited by claude #3563 11/17/2005 8:15 AM
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BruceinHouston
Posted 11/17/2005 8:53 AM (#11637 - in reply to #11444)
Subject: RE: Wheel offset, reason, choices?


0
Location: Houston, TX
Claude, "percent of bikes wheel base..." ? That sure makes a LOT of sense.

Have you thought that through all the way to any general recommendation?

Best regards,
Bruce


Edited by BruceinHouston 11/17/2005 8:54 AM
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