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#1 dowey

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Posted 01 January 2017 - 10:25 AM

Hi, I know this has been discussed a million times but it doesn't hurt to see if there are any more options available.
Just about to replace the tyre on the drive wheel and was about to order an Avon 3.50/19 sidecar tyre but thought i was ask about first.
The Avon has done well over the years for me and i know the proper size is 4.00/19 but this tyre lasts a lot longer than any others i had used and the size hasn't been a problem.
So, is there any other suggestions before i click?

Cheers an happy new year till yas :)
2005 ural
1992 dnepr mt11
2015 ural

#2 santareg

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Posted 18 March 2017 - 02:07 AM

I used those Avon "Square Block" tires on all three wheels of my 1977 R100S /Sputnik rig with great success, longer wear, good ride for stiff tires, just a tad skinnier. Will replace my Duro's with them when it is time.  Never had a front tire oscillation issue, plus the profile gave a larger on the ground footprint. My BMW had an extended triple tee by Dauntless and a damper similar to Sean's R2W setup that is soon to be on my 2014 Gear Up replacing the troublesome stock damper.

#3 Russ Noe

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Posted 18 March 2017 - 09:45 AM

Consider the tire profile for the front tire.
A square/flat profile up front can induce oscillations that cause the handlebars to slap back and forth.
('depends on other conditions including steering dampers.)
I've used the flat profile tires on the pusher and sidecar wheels, but always use a rounded profile on the front.
~RN

#4 santareg

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Posted 18 March 2017 - 10:34 PM

View PostRuss Noe, on 18 March 2017 - 09:45 AM, said:

Consider the tire profile for the front tire.
A square/flat profile up front can induce oscillations that cause the handlebars to slap back and forth.
('depends on other conditions including steering dampers.)
I've used the flat profile tires on the pusher and sidecar wheels, but always use a rounded profile on the front.
~RN
Hi Russ not sure why the profile would cause the oscillations, never had the problem, that I could blame on the tire profile, I had bad low speed oscillations on my Gear Up (Stock round profile Duro's) when the damper went bad, FYI on the 2rd replacement and a known issue. Bought the R2W damper to solve the issue once in for all.  I tried running the BMW (Avon Square Block) without the damper and had oscillations. Same problem with my heavy KawaHack 1600 V twin with Motorvavation Hack, hooked up the damper back up and all was well and it had rounded profile street tires.  I'm thinking we get the problem with the addition of a sidecar and the answer is a good damper. At first I thought the leading link would be immune to this but it is just as bad as all the others. Of course taking into consideration that I am a fat old guy!

#5 Russ Noe

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Posted 19 March 2017 - 09:45 AM

Santareg:
A flat tire profile can "drag" the steering tire to a side when it is turned.  The inner edge contact surfaces tends to pull the steering around, further into the turn. The wider the contact surface, the greater the force developed.

This can be related to 2-wheel front steering "toe-in" or "toe-out." Toe-out makes the steering unstable (over steer), while toe-in provides stability (under-steer). One tire "corrects" the position of the other. This is especially noticeable with tail-wheel airplanes taxiing on the ground. Toe-in corrects the tendency to "spin out"
when trying to go straight.

A single tire does not have the benefit of a balancing second tire. I suspect this is a component of the cause of the front end oscillations in our sidecar rigs.
I have experienced such oscillations with an old front tire that had worn to a flat profile. When replaced with a new rounded-profile font tire, the oscillations completely stopped. No other variables had been changed. And I've seen this happen on other sidecar rigs, too. Not only on my Urals.
Complex stuff, we humans engineer... And I don't claim to fully understand this subject.

Ride safe,
~RN




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