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tires for a rig
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Ursa da Grizz
Posted 12/7/2004 2:05 PM (#5559)
Subject: tires for a rig

I am currently setting up a Moto Guzzi Breva with a Duna sidecar. I started looking for 17" flat profile treaded tires to improve traction, braking and tire life and have had little luck so far.

I have gotten questions about why I would want to do this in the first place. "Those tires will quickly wear flat on the bottom anyhow so why bother?" sums up that point of view. Seems to me that "wearing flat" wastes tire rubber quickly and leaves one in a less safe condition until accomplished.

As I understand it, on a sidecar rig the stresses on the tire are more "automotive" in nature. That is, the vertical pressure is augmented by significant lateral force on turns and not significantly increased in turns as is a 2 wheel motorcycle usage.

I am running automotive tires on my Moto Guzzi V11 EV/ EZS RX5 combo. As I understand it motorcycle radials also give little lateral stiffnes. Automotive tires are built to deal with it.

Also, a tire having a flat tread has a larger contact patch at any time for greater braking capability.

Anyone have any thoughts on the above and sources for 17" flat tread tires?



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Posted 12/8/2004 12:47 AM (#5571 - in reply to #5559)
Subject: RE: tires for a rig

Good Day,
Bridgestone makes a 175/55 R17 model RE040 BZ. You would need to measure your clearences to see if that could fit. Probably nobody in North America stocks it though so you'd have to order it from somebody like BlackCircles or one of the other UK mail order outfits unless you've got a buddy over there.
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claude #3563
Posted 12/8/2004 7:49 AM (#5572 - in reply to #5571)
Subject: RE: tires for a rig


Posts: 2498
Location: Middleburg, Pa
'Wearing flat' is what motorcycle tires will do on a sidecar outfit. Key work is 'wearing' and they do it quicker than on a solo machine. Mnay have found that the Dunlop 491 does a fairly good job for a motorcycle tire on an outfit Reports vary as to actual milage a tire such as this can get . It depends upon many things such as proper setup, driving style, loads carried, roads traveled on etc. I have gotten 8000 miles with these tires on the rear and more on the front. I have also worn them almost to the air in half that amount of mileage due to hotrodding around . A bad setup can grind the rubber off of any tire in very short order but that should not happen if one monitors tire wear and makes adjustments to their setup as needed.
There are flat tread tires designed for sidecar use available for 18 and 19 inch wheels that do fairly well. There are none that we know of for a 17 inch wheel however.
With all of that being said the automotive tire conversion is very appealing to many. The good thing about the 17" rim is that it is very close in diameter at the mounting point to a 17" car wheel rim. Some other wheel sizes are far off enough in diameter to create a real life concern and a direct mount of a car tire on these motorcycle rims should not be done. 16" and 17" are very close though.
The downside of the 17" rim is , as you mentioned and Norm confirmed, is the availability of tires. They can be had, as Norm stated, but please count the cost of them. Do some checking on what they would cost to be delivered to you from overseas. Also a consideration would be the cost when tire replacement is in order.
Many have decided the value -vs- cost scenario related to these imported tires was not effeciently there. Suzuki Bandits are a good example. They have 17 inch rims and can use the imported tires. I know of two owners who felt it more sensable to go to a 15" wheel conversion on these bikes. Yes, the conversion is not inexpensive but with all things considered it may be a viable road to go down, especially if you plan to keep the rig for along time. The price of these wheel vary greatlyin the market place. You may want to shop around before making a decision. Norm, who posted earlier , has made wheels. Harry Tarzian of H.T.Wheels ,(814) 349/2421, also makes a nice looking Centerline Aluminum wheel conversion at a decent price. These wheels can run ,for example, a 165R15 car tire. The last 165 we bought was only 38 dollars at Pep Boys. Ya have to agree this is a very low price for a tire that may end up dry rotting before it wears out compared to a motorcycle tire that costs maybe more than three times as much.
In the motorcycle world today we all know that many spend untold amounts of hard earned cash on items that have no functional value. They buy 'look good' stuff. Nothing wrong with this I am just making a point that witha wheel conversion you have a functional product that fillls the 'look good' side of things as well.
So... There is some logic in doing the 15" conversion but only you can decide if the investement is valid for your situation.
In closing , yes, you are right. Flat tread tires will have a larger contact patch. Any given tire can only give us 'X' amount if traction. This traction can be eated up in acceleration, braking and cornering forces. In reality it is a combination of the three. When close all of a tires traction is being absorbed by cornering forces and a person accelerates then the traction account is overdrawn and the contact with the surface being ridden on is compromised. Pretty simple really. More tire equals more contact patch equals more traction to be used as needed. Face it Indy Cars do not have 3" wide tires .
Yes , there is more to it that that but the logic is still there.
Hope this helps a little

Edited by claude #3563 12/8/2004 7:53 AM
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Posted 1/25/2005 1:16 PM (#6007 - in reply to #5559)
Subject: RE: tires for a rig

how about the dunlop pt tires any thoughts on mileage for this tire ? harryho
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Posted 2/5/2005 10:53 AM (#6196 - in reply to #5559)
Subject: RE: tires for a rig


Posts: 16
Location: Owasso, OK 74021
How about the Dunlops? Well, they've just come out with the new 491 Elite III, for the GL 1500/1800, that's supposed to "significantly increase tire wear life." That said, remember, our stuff has different physics being applied. As said earlier, set-up, riding style, load carried, road conditions all affect year mileage. I got my new Friendship II couple'a weeks ago and am really enjoying it, but (yeah, there's always a 'but' isn't there) I don't like the way the rear tire is looking. Since the rig's been installed it looks really squatty, almost like a car radial. I added air to get it up to 44lbs and that helped a little. The rated max pressure is 41, so I'm already just under 10% over max. Won't risk taking it up any higher. Unless someone can really find a decent, hard tread, stiff sidewall motorcycle tire, we're going to have to drag along with what is used for 'normal' motorcycles and pay the price for the joy of riding our rigs. Rear wheel conversions are pricey, but they cost less to maintain once you've made the purchase. At this point, looks like I'm goint to have to go with the new 491 III's. I'll let everyone know how they work once I've got'em on.
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