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Old 06-19-2013, 04:52 AM   #31
GSBS
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After a half-hour of reading...

...on various sidecar forums and set-up guides, it seems to me that tire pressure for a sidecar rig it about as settled a question as the best type of oil to use. In other words, not at all!

In general most of what I saw recommended the tug rear having the highest pressure, then the tug front, and the sidecar tire having the lowest pressure.

I guess it calls for just experimenting with my rig to come up with the best for its characteristics. I think I may start off with a lower pressure in all three tires - around 25R/22F/20SC - to see what happens.
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Old 06-19-2013, 08:56 AM   #32
claude OP
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Rim width can affect the contact patch and make for more of a crown on the tread area itself depending upon sidewall defelection etc. Some sidewall are much stiffer than others and can do this ..others may show no affect at all.


Rule of thumb that may or may not be accurate in all cases: Low sidecar tire inflation will aggivate a low speed head shake. Headshake can be corrected many times by higher or lower pressure up front.

Rear tires should wear even. What can affect this is a multitude of things...
The air pressure, of course, can be a factor. Riding style? Those who are brave in lefties but timid in right handers may see more wear on the sidecar side of the rear tire.
Typically for most cases of excessive rear tire wear will be too much toe in.
This is again, most cases. Exception can be a that a car tire on the rear can overpower a small narrow tire on the sidecar causing it to wear first.
Front tire wear is usually the result of riding style to a point. Agressive lefties , especially with dual sport outfits will aggrivate front tire wear when smallish tires fail to provide a large enough contact patch where the rubber meets the road. Understeer , of 'pushing' the front end is comon on these dual sport type setups.
If on ewishes to play with low tire pressure take heed that is is possible to roll a tire off the bead if you get too low especially with non forgiving still sidewall tires.There are rims avaiable with bead locks if one wishes to push the limits of low tire pressures. I tis also possible to screw th etire bead to the rim but this is probably far past where we want
to go here.
We typically run about what is on the tire and things do quite well if tgh esetup is good. Dual spot type rigs exhibit a lot of body roll in cornering creating weird tire wear and faster tire wear. . This can be helped to th epositive side with a well designed anti swaybar. However with the addition of the swaybar you may see that your fron ttire begins to wear first. Another plus for bigger rubbe rup front.
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Old 06-19-2013, 11:36 AM   #33
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Claude, forgive me the mis information that I disseminated about bike rims vs car wheels. Of course a narrower wheel will act upon the tire by changing its characteristics. The act of pulling the beads closer together will cause the side walls and tread to bulge causing different handling properties. I have that problem now with a set of wheels that I had wanted to use but I have determined that they are to narrow for a car tire so i must either find a new wheel or do some modifications to the wheels that I already have. In all reality, tire pressure will be up to the preference of the rider, there will of course be a learning curve as trial and error is applied and handling characteristics are determined for each application. As of this moment I can not speak to the needs of running a sidecar or the use of tires on such so I will defer to those who have gone before to learn from. This discourse has given me the impetus to sit down and do the calculations for forces acting on a car tire in application to motorcycles and perhaps, write a paper on it.
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Old 06-19-2013, 04:21 PM   #34
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Quote:
Originally Posted by claude View Post
Front tire wear is usually the result of riding style to a point. Agressive lefties , especially with dual sport outfits will aggrivate front tire wear when smallish tires fail to provide a large enough contact patch where the rubber meets the road. Understeer , of 'pushing' the front end is comon on these dual sport type setups.
That would describe me. I love pushing it, and sometimes rolling on strong coming out of a tight curve I can feel the front tire chittering across the tarmac. I figured that's why I go thru front tires so fast, but it's how I ride. Guess there's nothing for it but to go with a car tire up front. Stroker, here I come!
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Old 06-19-2013, 07:06 PM   #35
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Air pres changes

I went for the dual sport mid afternoon ride front 145/65/15 Blizzak 28 lbs rear and chair 175/65/15 NittoSN2 winter tire 26 in the rear 25 in the chair.Really great in gravel and loose stuff almost too good I had a hard time getting the back to slid in gravel without using the brake.
Once the tires warmed up I ended up with 31 in front and 30 in back, next ride will start with 30 in front and 28 in back. The whole thing has taught me no one pressure fits all tire wise, the lessor pres in front really calms the blizzak down on rough uneven surfaces, the Nankang 145/80 I had on the front liked 34-36 pounds better.

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Old 06-20-2013, 04:33 AM   #36
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tires and pressure

I generally run the maximum air pressure that is on the tire sidewall. This is the manufacturers recommened pressure at which the tire is intended to be used. Obviously taller profile tires, like the 80 and 75 series tires that many of us on our dual-sport rigs, will have a softer ride and more floation properties on loose surfaces. Lower profile tires like the 65 thru 45 series tires will ride stiffer, but will give more precise steering and handling. What type of tire to use is a personal choice and depends on what type of riding that we plan on doing. Of course, sway-bar and shocks with the correct spring rate is also part of the equation. Tire pressure is a good way to "fine-tune" how the rig rides and handles after the proper tire choice has been made. Dave B. has tried many of the tires that are available for use on our wheels and has offered us objective characteristics of the various tires.
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Old 06-20-2013, 01:27 PM   #37
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I agree with Stroker on this. One can go up or down a few pounds with no ill efects. There are exceptions but I do not think we are dealing in that realm here.
I ,personally, would not reccomend running extreme low pressures in the types of tires and /or tire rim combinations we are dealing with here. Weight capacity as compared to a car is not the only factor we would be dealing with. If it was then possibly there would be little concern.
The concerns would be two fold with extreme low pressure. Heat build up in the tire will increase as pressure goes down. Heat is from the flex that is incurred. Sidewall flex is a concern . Many race cars have a valve stem that actually lets air out as pressure builds in order to maintain a given air pressure once things get hot. Once it then cools off it needs to get hot again to get the pressure back up. Not applicable in our case here.
. Yes, sidewalls want to flex and are designed to do so to allow for some semblance of a slip angle to make the cornering ability more forgiving. Slip angles are the result of sidewall design related to the height of the sidewall etc etc. You will notice that cars with very small sidewalls have a one ply rating...why? Yep...to increasse slip angle.
The other concern is that it may be possible to roll the tire enough in cornering of hitting a hole when cornering to break the bead on the tire. Yep...air comes out and things litterally can go down hill from there. You do not want to blow a tire quickly when cornering due to the bead unseating. Yes, one could switch to a rim with beadlocks to prevent this but the cost vs value isn't there at all due to what was mentioned above as well as other concern.
Other concerns? Wobbles! A low speed head shake that we hate to even refer to as a real wobble is fairly common with many sidecar outfits. This is not a big deal. However a high speed wobble can be disaster! You do not want to go into a tank slpper with a sidecar outfit. Very low air pressures on high sidewall type tires can aggravate a potential wobble. Ever tow a trailer that swayed? Many time airing up the tires will take that away.
So....why the low pressure on these types of outfits? I can see it on really really rough terrain at slow speeds but it is a stretch.
Stock air pressure give or take a couple of pounds max either way gets my vote.
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claude screwed with this post 06-21-2013 at 07:23 AM
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Old 06-21-2013, 02:13 AM   #38
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Two things and then I will shut up:

First, what is the "Max Load" rating on the tires you are using?

Second, does your rig even come close to that max rating?
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Old 06-21-2013, 04:41 AM   #39
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bike and car tire comparison

These are the ratings of the stock bike tires vs. the tires I run on my R1100GS rig: Front-Metzler 110/80R19-max load 535lbs@42psi / Nankang 135R15-max load 805lbs@44psi Rear-Metzler 150/70R17-max load 715lbs@42psi / Vredestein 165R15-max load 1169@51psi . My rig weighs upwards of 1500lbs when loaded with 2 passengers and gear. Make mine car tires!
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Old 06-21-2013, 05:38 AM   #40
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Quote:
Originally Posted by guitstik View Post
Two things and then I will shut up:

First, what is the "Max Load" rating on the tires you are using?

Second, does your rig even come close to that max rating?
I believe you guys are actually on 2 different tracks I understand Stroker completely here's an image of his rig on a long trip,probably the trip that helped him decide he needed better tire alternatives.


But I read somewhere years ago that the designers considered lots of different forces for motorcycle tires as there is allot more compression braking and sliding sort of forces on cycle tires and they are usually run harder(more pressure) than car tires. All us who mount their own know its best to leave the metzlers sit in the sun for awhile before mounting to fight them on and the sidewalls are stiff as the tread face.DB

Will the anti car tire forces pleas stand up and be counted ??
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Old 06-21-2013, 05:55 AM   #41
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The terrain I am riding on usually dictates the amount of tire pressure i run. Car or bike tyre .Any where from 15psi to 35psi .



Cheers Ian
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Old 06-21-2013, 07:27 AM   #42
claude OP
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Quote:
Originally Posted by guitstik View Post
Two things and then I will shut up:

First, what is the "Max Load" rating on the tires you are using?

Second, does your rig even come close to that max rating?
Don't shut up QUITSTIK you have made some interesting comments. Good discussion can help us all to think more and learn more. No One is beyond learning and ANYONE who thinks they know it all is obviously deceived in a bad way .
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Old 06-21-2013, 09:12 AM   #43
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Don't shut up QUITSTIK you have made some interesting comments. Good discussion can help us all to think more and learn more. No One is beyond learning and ANYONE who thinks they know it all is obviously deceived in a bad way .
Thanks Clude, I do enjoy the debate. Before I continue let me state that I am NOT against car tires on motorcycles, in fact I am an advocate. I have been a member of the darkside since '07.

Let me give you a little back ground info, in '09 I was involved in an accident on my motorcycle. It was one of those situations that as an MSF instructor I had always tried to avoid and taught to the students to do the same. NEVER get caught up with a large grouping of cars and NEVER allow yourself to get boxed in with no out. I was on a four lane road with a speed limit of 55mph and had passed through a controlled intersection that is notorious for bad accidents. As is my normal habit I was in the left hand lane to avoid cagers that have a tendency to pull out in front of you with no regard to safety. It was at this point that I became boxed in with traffic on all sides, there was a car in the turn lane going in my direction that was acting erratic. I had a safe margin between myself and the car in front of me, in fact I had slowed down to about 35-40mph when suddenly the car ahead veered into the right hand lane cutting off another vehicle. A pickup truck had stopped in the left travel lane in an attempt to make a left hand turn even tho there was a turn lane available. I hit both brakes in a controlled manner but even at the low rate of speed and about three car lengths I managed to slam into the back of the pickup rather hard. Had it not been for the fairing that I had installed on my bike I would have ended up in the back of the pickup but as it were, I was tossed backwards by the fairing. The bike, a '98 Honda VT1100C with saddle bags and a car tire on the rear. Everything on the bike was in perfect operation including the brakes front and rear. In the course of braking I had bent the rear brake lever. At the time of the accident I had been riding with the car tire for over two years and 30K miles in all types of weather including snow and ice so I felt confident in my abilities and those of the tire/bike.

Now as to the cause. In my research I have come to the conclusion that it was a lack of hysteresis. Hysteresis is one of those things that tire manufacturers take into consideration when designing a tire. Heat in a tire is not necessarily a bad thing in fact it is needed but to much and the tire breaks down faster, to little and the coefficient of friction for the tire pretty much goes out the window. The later was the case for my situation. I was ten miles from the house on a good dry clear road traveling at the posted speed limit of 55mph. Under normal circumstances with a bike tire on the rear at the speed I was traveling just before the accident the tire would have reached a normal operating temperature and stopping would have been achieved.

Hysteresis is the act of deflection/deformation that a tire goes through when rolling that creates heat in the tire that will result in a normal coefficient of friction between the tire and road surface. Most people do not notice this when driving but you do not need to apply the brakes to slow a vehicle down on a flat road. Friction will slow you down considerably just from the weight of the vehicle, rolling resistance of bearings and of tires on tarmac as well as other factors. A car tire is designed with hysteresis derived from the weight of the vehicle and tire pressures. When you keep all things constant but remove just one element from this equation all other factors become moot. We can all agree that a motorcycle, even with a hack and a full load will never exert the pressures on a car tire that a car will, unless of course you have a pachyderm as a monkey.

My point of this lengthy dissertation is that when one variable is changed another must change along with it to keep the values constant. The variable that we change by the very nature is weight/force on the tire, to match that, tire pressure must change to bring some balance back into the tire design.
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guitstik screwed with this post 06-21-2013 at 10:00 AM
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Old 06-21-2013, 11:03 AM   #44
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Quote:
Originally Posted by guitstik View Post
Thanks Clude, I do enjoy the debate. Before I continue let me state that I am NOT against car tires on motorcycles, in fact I am an advocate. I have been a member of the darkside since '07.
.
I did not mean to label you as anti car tire quitstik, your info's great, and your temp thesis is good also, now I just gotta get some weight on my 17 pound Mini Schnauzer Justin LOL.DB
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Old 06-21-2013, 06:26 PM   #45
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Googled Hysteresis in tires, los of interesting reading, Wiki's seems the best easiest:http://en.wikipedia.org/wiki/Rolling_resistance

I ended up with 29 front and 28 rear at the end of today's ride, the radials seem to deform about the same however much air's in them example 16-28 look about the same but I can't be sneaking over ugly rocky places without some air in the tire, I think I'd be courting disaster.DB
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