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Discussion Starter #1


So hard to get to the 650 valves to get an accurate read I broke down and bought the above which works the charm.

That said . We set it up 40 and 40 cold which I found too stiff on the front end so dropped it to 39.

That seemed fine most of the day of a 200 mile ride today through the twisties. As the tires heated it got to 41 and 43 which was acceptable.

But later in the day as the temp rose it got to 43 and 47!! and I really found the front end jarring at that kind of pressure on downhill twisties.

Now I'm torn as I like the lighter feel the higher pressure in the warmed up tires gives but was surprised at the range of change.

Anyone else using a real time gauge have some insight.

Going for a longish ride in PA twisties and want to settle on a cold tire pressure that gives me reasonable stick and ride comfort even when it gets hot.
Any thoughts. I'm thinking of seeing how it does over time and if there is any pressure loss but **** that was jarring and a bit uncertain with pressures up that high ( Metzlers on ).

viewtopic.php?f=4&t=31795&start=0

This was the related thread and in light of how high the pressure goes up on a hot day/ride - maybe Suzuki's 33/36 has some value as from the looks of it that could end as high as 38/41 when fully warmed and I certainly felt the bike to be more skittish when the pressure was up in the 40s hot.
I'm 250 lb with 20 lb of luggage carried regularly.

Thoughts?
 

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Whew,,,,,,,! Yeah I got thru your post - ok.......!!!! Nothing like overkill...! You can solve your tire pressure fluctuation problems affecting your ride....simply by finding a tire center AND HAVE THEM FILL THE TIRES TO THE DESIRED PRESSURE WITH - NITROGEN!!!!! Nitrogen is an inert gas which will not expand as the tires heat up......!!! Therefore - your tire pressure will remain -UNCHANGED!!! :thumbup:




There are several compelling reasons to use pure nitrogen in tires.

First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that your tire pressures will remain more stable over the long term. Racers figured out pretty quickly that tires filled with nitrogen rather than air also exhibit less pressure change with temperature swings. That means more consistent inflation pressures during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important.

Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.

If I ever need to top off a tire when I'm out on the road, I'll always briefly depress the tire chuck's valve with my thumbnail and vent some air. If my thumb gets wet, there's water in the line. Some gas stations don't do a very good job of keeping the humidity out of their air system. I don't even like to use a water-based tire-mounting lubricant unless I can let the tire bake in the sun for a couple of hours before I air it up and seat the bead. I've dismounted tires (not mine) that had several quarts of water inside—probably from a compressed-air hose that collected water and was never purged properly.

How is water relevant to a nitrogen discussion? Any system that delivers pure nitrogen is also going to deliver dry nitrogen. Filling tires with nitrogen involves filling and purging several times in succession, serially diluting the concentration of oxygen in the tire. This will also remove any water.

It's certainly simple, although time-consuming, for a tire technician to fill and bleed tires. But most shops use a machine that not only generates almost pure nitrogen by straining the oxygen out of shop-compressed air, but will also automatically go through several purge cycles unattended. Some shops have been charging as much as $30 per tire for this service. I think that's too much. If you're buying a new tire, it should be far less. Still, the nitrogen generator, filling system and technician's time aren't free—the dealer is entitled to some return for that.

So, to answer your specific questions: With nitrogen, your tire pressures will remain more constant, saving you a small amount in fuel and tire-maintenance costs. There will be less moisture inside your tires, meaning less corrosion on your wheels. You will not be able to feel any difference in the ride or handling or braking, unless your tire pressures were seriously out of spec and changing to nitrogen brought them back to the proper numbers.
 

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Discussion Starter #3
Ummm last time I checked nitrogen was subject to the same laws of physics as other gases.
It's used to combat moisture mostly and will not change the swing in pressures.

It's hardly overkill to know my tire pressures and nitrogen is not a solution believe what you like.
 

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MacDoc said:
Ummm last time I checked nitrogen was subject to the same laws of physics as other gases.
It's used to combat moisture mostly and will not change the swing in pressures.

It's hardly overkill to know my tire pressures and nitrogen is not a solution believe what you like.
Actually I found both posts of interest. While indeed nitrogen is not an "inert gas", it might help somewhat. It would be interesting to see pressure results from someone with nitrogen-inflated tires who has a gadget like MacDoc has.
 

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Nitrogen will behave in a very similar fashion to air as temperature is increased in what is essentially a fixed volume. Remember Air is 70% Nitrogen anyway and both are subject to the gas laws.

Establishing your pressures when cold is good enough for this marlarkey.

The increased pressure of gas is sort of compensated by the way the rubber behaves with increasing temperature.

It is an interesting exercise nevertheless, however you do not really have the full resource to do any meaningful R&D on this and should trust manufacturers recommendations for cold pressures.

Sometimes it is tempting to over think this sort of stuff.

All that been said tell us more about the monitoring kit. :wink:
 

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Discussion Starter #7
The monitoring kit is very straight forward and easy to install and use and you can have it alert you to various conditions. I figure it's a good buy over time as it's not bike specific. Will get the model - buried just now.

You may be correct on the manufacturer suggestion as clearly the tires go way up with heat. Will try some other configs on the front first and see what the pressure range is.
Will drop to 36 cold and see how it feels and where it goes up to.
 

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I have not had cold tires since April. 8)
 

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A friend has one on his Victory something-or-other (just like Harley, they change the tank emblem and it a whole new model), and it appears to be a fun toy if you have $200 burning a hole in you pocket. There are no online specifications available that I can tell, however the paperwork my friend received claimed its accuracy to be +/- 2% of the readout from 20 to 60 psi.

This is the outfit that markets it here in the US. The motorcycle version is not listed on their Products page, however it is on the price list page.
 

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I admit I'm a bit foggy from a bad head-cold, but I'm confused. Are you talking about 40 psi in the front or rear tire? Cold inflation should be 33 psi for the front - so 40 cold would cause a harsh ride. I only ask because your issue is with the feel of the front end.

Or, if you're talking about 40 psi in the back tire, are you saying normal heat-caused pressure increases in the rear tire effect the front-end ride quality to the point you can tell the difference in a few psi? Wow.

I just go with the recommended cold-tire pressures, knowing that the manufacturer has accounted for heat from friction/ambient temps as to safety, ride quality and tire wear . (As I do ride 2-up often, I keep my rear pressure at 41 even when riding solo). I would also think that as the psi rises due to increasing temps, the characteristics of the tire material also change - so a softer/more flexible hot tire at 40 psi feels about the same as a cold tire at 36.

Have you played with the pre-load adjustment to "fine-tune" for comfort?
 

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Discussion Starter #11
I was working off LeDude's comment about 40 front and rear and I had assumed that was cold.

Just came back and the pressure hot 60 mph for 1.2 hour is 43 front and 47 rear,
Temp on the rear was 117 degrees and front 93.
 

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Humm. I'll have to check out LeDude's comments for context. I'm not sure why one would run at 40 psi in the front tire. I did once by accident (the shop over-inflated it after a service), but I could immediately tell as I had lost much 'tactile feedback' from the road.
 

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Discussion Starter #13
This is the entire quote
there is not much around it .....
Re: Tire pressure

Postby LeDude » Wed Jun 25, 2008 3:16 03
You also have to take into account the bikes total weight with rider/gear and how you set your suspension.

I weigh around 190lbs and run the following:

40psi in the front
42 psi in the rear

Works great on my 04 and I have been getting close to 15k miles out of my rear tires and will probably get closse to 21k on the front tire.

Try different settings and see how it works out for you, the manufacturer's recommended settings are just that, a recommendation.

Check the side wall on your tires for the maximum allowable inflation setting, I think it is 44psi for the OEM Bridgestones...
The current 41/39 cold seems "okay" for casual riding on side roads etc.
It only goes way up with the heat and speed.
I'd like to avoid the squaring off on the rear and do enjoy the lighter feel the firm tire gives but worry it's too high for aggressive twisty riding.
I think I am going to leave it for the trip down - will get good mileage and then check it down in PA and maybe come down a couple pounds in each.
 

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Personally I don't like to run more than 36 psi cold in the front tire. The reason being that I could detect a little side slip in the front tire in aggressive cornering in the twisties when I ran pressures higher than that. I don't always ride that way but if I get into an emergency situation where I need that cornering grip I don't want to be without it.
 

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Discussion Starter #15
That's my concern as well - where is the point that you start to lose "stick" ??

Another forum was saying sports bikes run 30-33 cold and they higher for the highway so they don't get too hot.
 

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Maybe LeDude's goal is getting maximum tire wear - 15k on the rear? Another WOW.

I wouldn't be concerned about heat unless your way UNDERinflated. (Start worrying when Bridgestone or Pirelli come out with their special 'Global Warming' tires :wink: ) Personally, I wouldn't go more than a couple psi over on the front tire.
 

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I start noticing it at 37 but it's not disconcerting till about 39. Since I don't detect any advantage wear wise from going higher than 36 I don't see any reason to do so. Below 36 I get the scalloping wear pattern that some folks complain of. 36 seems to be the sweet spot for me.

Now I will qualify all this by saying I have a Corbin Long seat on my bike and that moves my weight further back than you will get with the stock seat. That could mean the way my front tire reacts is different to what others would see so YMMV.
 

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MacDoc said:
Ummm last time I checked nitrogen was subject to the same laws of physics as other gases.
It's used to combat moisture mostly and will not change the swing in pressures.

It's hardly overkill to know my tire pressures and nitrogen is not a solution believe what you like.
Hi MacDoc, speaking as someone who has used nitrogen in tyres I can confirm it's use will solve your problem. We also used to put it in customers bikes to solve this very problem. I don't have the 650 so I don't know what your recommended pressures should be. But whatever they are nitrogen will calm things down considerably. Nitrogen is of course subject to 'Charles Gas Laws' like any other gas. But nitrogen doesn't expand hardly at all when heated in car or bike tyres. You just set the pressures and ride. However, you must be careful to set the actual pressure you need when the bike tyres are hot, and not cold since nitrogen won't expand to raise the pressure as it heats. At least not to any real measurable amount. I've used it in all sorts of bikes and in a car and it's amazing. It will stop your problem, period! :cheers: Over this side of the pond it costs me the equivalent of about $7 per tyre.
 

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Quantum Mechanic said:
Hi MacDoc, speaking as someone who has used nitrogen in tyres I can confirm it's use will solve your problem. We also used to put it in customers bikes to solve this very problem. I don't have the 650 so I don't know what your recommended pressures should be. But whatever they are nitrogen will calm things down considerably. Nitrogen is of course subject to 'Charles Gas Laws' like any other gas. But nitrogen doesn't expand hardly at all when heated in car or bike tyres. You just set the pressures and ride. However, you must be careful to set the actual pressure you need when the bike tyres are hot, and not cold since nitrogen won't expand to raise the pressure as it heats. At least not to any real measurable amount. I've used it in all sorts of bikes and in a car and it's amazing. It will stop your problem, period! :cheers: Over this side of the pond it costs me the equivalent of about $7 per tyre.
If "...nitrogen doesn't expand hardly at all when heated in car or bike tyres.", and it "...won't expand to raise the pressure as it heats. At least not to any real measurable amount.", then why must one "...be careful to set the actual pressure you need when the bike tyres are hot, and not cold..."?

The answer is if course that the statement is not true. The pressure in a nitrogen filled tire will rise (or fall) about 1 psi for each 10°F change in its temperature--same as would happen in a tire filled with dry air. It is the water vapour in compressed air that make it expand, slightly more, than would nitrogen or dry air.

Heat in a tire is generated by the tire's structure flexing as it rolls along, this is its rolling resistance, and for a pneumatic tire it is to very large extent dependent upon inflation pressure. The source of the heat is vehicle's driving force overcoming the tire's rolling resistance. However for any tire on any vehicle, inflated to the same pressure with any gas, the amount of heat generated will be the same. Heat retained in the tire could differ if the gases being compared had different thermal conductivity, with the primary path I would assume being through the wheel; however nitrogen and air at STP do not differ, both being 0.024 W/(m K) (Watts per meter Kelvin).

[tongue-in-cheek]

Which brings us to another common claim for nitrogen filled tires, that fuel economy is improved. This is only true if one assumes that people do not monitor and maintain the pressure in their tires as they should. While this is likely true, and here nitrogen inflation does have a slight edge in it's lesser pressure loss over time, one could also argue that because of this element of human nature "wet" air would be a better choice as its increased expansion would to some extent compensate for the owner's negligence.

Using "wet" air would also have an advantage in that rolling resistance is decreased as inflation pressure increases. Lesser rolling resistance = improved fuel economy. In fact the lower the tire's inflation pressure the higher its rolling resistance, hence the higher its operating temperature, causing "wet" air to expand even more and further compensate for the neglectful under inflation...

[/tongue-in-cheek]

FWIW on my 400 with my fat butt on it (650 lbs total weight) traveling at 70 mph, overcoming rolling resistance uses up 1.2 HP, with aerodynamic resistance eating up 9.4 HP--more about this calculation here.
 

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Hi Cliffyk, sorry, you've misunderstood the thrust of my post, mainly due to the fact it's written badly no doubt. However, it is fact that nitrogen is used in tyres to prevent big pressure variations. Aircraft, race cars and bikes plus many other types of transport all use nitrogen to prevent big pressure variations. It is well known that nitrogen will expand the same as any gas, but it's volume and density is different to normal air containing oxygen and some other gases (and moisture) when heated. Thus nitrogen has a different volume and density when heated. Due to lack of oxygen and moisture in nitrogen this results in less pressure being generated in a warm tyre over a tyre inflated with just air (which is a mixture of nitrogen and oxygen). It's the oxygen (and moisture) that causes the big variations in pressure as the tyre is heated. Remove the oxygen and moisture and you get a much more stable gas/pressure in the tyres. I could go into loads of science stuff but it's been a long time since I was at engineering school.

Manufacturers know your tyres will increase in pressure as they warm so many manufacturers will often quote a cold pressure which is lower than is require by just a little. This is necessary to prevent your tyres being grossly overinflated when hot. So your cold pressure quoted especially on big bikes is normally below the peak running efficiency for that tyre. It's a balance, but that's what they do. So if you put nitrogen in your tyres when cold, and measure it, when the tyres are hot there will be almost no change in the pressures measured, and so they maybe marginally underinflated. It's something to consider anyway. An example is my GSX1400. I had nitrogen in my tyres. The rear tyre would gain around 4 psi when hot with AIR in the tyre. With NITROGEN the rear tyre went up by around 0.9psi when hot. These measurement are variable of course, but the trend isn't. This was insufficient to maintain good handling on the bike when the tyres were hot and at speed. So it's important to set the pressures to a setting that will maintain good handling and running when the bike tyres are hot. On my GSX1400 I set the tyres to 2psi above the manufacturers cold settings with nitrogen in to keep the handling ok. If you don't do that the Nitrogen won't expand enough to make things right. That's what I was trying to say...errr....badly it seems! I could go on about some other points you make but it's not really very relevant. The main thing is...Nitrogen works! Dry air won't work the same due to the oxygen expansion being greater and density being more etc etc.

You also make some very interesting points with which I agree concerning fuel economy etc. But none of that is relevant here I guess as the OP was asking about a tyre pressure problem.
 
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