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How To Adjust Hot Vs Cold Pressures?


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This is a huge mystery for me. Mostly because of all the different schools of thought involved. Does anybody have a workable "formula" of how to adjust hot pressure?

 

Normally I "set it and forget it" and that's worked well for me. I run Dunlop Q3's on an S1000RR and do 31/30 cold. I recently did a 101 degree track day and realized this is probably not the best approach when the temp goes from 80 in the morning to 101 in the afternoon.

 

HELP! :)

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This is a huge mystery for me. Mostly because of all the different schools of thought involved. Does anybody have a workable "formula" of how to adjust hot pressure?

 

Normally I "set it and forget it" and that's worked well for me. I run Dunlop Q3's on an S1000RR and do 31/30 cold. I recently did a 101 degree track day and realized this is probably not the best approach when the temp goes from 80 in the morning to 101 in the afternoon.

 

HELP! :)

Robert, If you don't mind let me repharse the question.

 

What would be considered the optimum operating temps for Q3's and what is the do not exceed temp for these tires?

If the tire is too hot should I add air or remove air and which way for too cold?

 

By knowing the operating range of the tire you can adjust the pressure to obtain this.

 

Jeff

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Jeff.

 

Don't mind at all. :)

 

My goal is to have a full end to end understanding of the "why" behind tire pressure adjustment. That's what's been missing in the past for me to be able to intelligently make adjustments. Ultimately it's about tire temp rather than pressure. Pressure is the method of the adjustment but the temp is really the important aspect that relates to having the tire function as designed.

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I was reading many things concerning the Q3's so I made it easy on myself and emailed Dunlop. Below is thier reply. You may want to start there and feel it out.

 

This is for your other thread but I always put my pressures back to stock for the street. I keep track riding for the track so I am not as worried about optimal hot tire grip.

 

"The best and easiest way to set your tire pressure is to start at 33psi cold front and 31psi rear, do a track session, then as soon as you come off the track, check your pressures and adjust them to 35 front and 34 rear for the Q3's. Don't be worried to try +- 2psi depending on how polished or coarse the track surface is. Lower psi for more polished tracks and higher psi for more course tracks."

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Thanks! That's exactly what I was looking for is a hot pressure value. At least "somewhere" to start. As for understanding all this witchcraft that may take a bit more time. :)

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This is a huge mystery for me. Mostly because of all the different schools of thought involved. Does anybody have a workable "formula" of how to adjust hot pressure?

 

Normally I "set it and forget it" and that's worked well for me. I run Dunlop Q3's on an S1000RR and do 31/30 cold. I recently did a 101 degree track day and realized this is probably not the best approach when the temp goes from 80 in the morning to 101 in the afternoon.

 

HELP! :)

My understanding is that you are usually looking for a 2-3psi increase from cold to hot. IIRC the Dunlop website recommends starting at about 32 psi cold and look for the tires to get to 34-35psi hot.

 

Many tire vendors will ONLY give you hot pressures for their race tires, and the expectation is that you will put on warmers, THEN set the pressures once the tires are up to temp - around 160-175 degrees F. That's because the COLD pressures will vary depending on ambient temp, but the HOT pressure (at the tire warmer set temp) will not, so it is much more consistent to do it that way.

 

I don't know that it is necessary to adjust your tire pressures for different ambient temps UNLESS you can't get enough heat in them because it is cold out. In that case you might set the pressure to 31 psi cold, ride a session, then check pressures right after exiting the track and if you have only gotten to 32 or are still at 31 you might drop the pressure a little to allow the tire to flex more and to get more heat into it. You'd also probably notice that the tires don't feel hot to the touch, or they might feel a bit loose on the track.

 

Q3s have a very wide operating temperature and will grip well at temperatures much lower than a race tire, and in my opinion they also warm up faster and more easily, so on those you may not notice much (or any) difference in how they feel on track.

 

It sounded like you felt that you needed to lower your tire pressures for a hot day - I'm not sure why that would be necessary, since the tires are designed to operate at temps in the 160-180 degree range, unless you found that the tire pressure was increasing too much between cold and hot. For example if you set it to 31 psi cold and the pressure jumped up to 38psi hot, you'd probably want to bring it back down to the recommended hot pressure of around 34psi.

 

(Side note - I think having the pressure too LOW is a more common cause of a tire actually getting overheated - too much flexion on a hot day can do that, and poor suspension setting can overwork a tire and contribute to that, too. )

 

For race tires I think it is more common to change compounds (ultra soft to soft or to medium) with different ambient temps, not pressure - a soft tire can provide better grip in cooler weather and a medium tire could be more resistant to excess wear on a hot day. The Dunlop website has good info on choosing the right tire for high or low temps or for different track surfaces.

 

The safest bet is to check the tire pressure when hot, at least once - but the Q3 seems like a very forgiving tire and is long as it feels OK and is wearing OK, you're probably fine just sticking with 'set it and forget it' in the morning.

 

Does that help? In your case I agree with something Jeff said earlier - since your pace has increased so much, I wonder if it is time to start doing some suspension adjustment. Do you ever adjust your clicker adjustments? That will open up a whole new world of mystery. :)

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Hotfoot,

 

As usual very helpful.

 

The problem that I had with the pressure towards the end of some sessions the back of the bike felt "bouncy" especially on a section of the track that had some ripples. The bounce got so bad that I hot pitted and was convinced there was something physically wrong with the bike. I don't know for sure since I never checked the pressure (I went right back out) but I would "guess" that perhaps the tire was overinflated and the pressure had risen too much.

 

Out of need I adjusted some of the suspension on the FZR but only to solve specific problems and at that I cheated a bit. I probably should start playing with the suspension a bit and get to know it a bit better. I don't even know which adjusters are which beyond the preload on the BMW's suspension. The guys at Traxxion Dynamics set the bike up and I have yet to touch a thing. I should probably get to know that stuff a bit better. :)

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  • 2 weeks later...

So I just got done with a pair of days at Streets in the 110 degree range, no idea what the track temp was but it was HOT, set the Q3's to 32/30 in the morning and they did just fine all day, i could feel them getting a little squirmy in T3 and T8 if I was a little more aggressive with the throttle, but they also were on track days # 5 and 6 for the set. I think unless your tires are telling you somethings wrong your probably over thinking things.

 

Tyler

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Oh. I'm definitely over thinking things. I tend to do that by default. :)

 

On the over thinking front though I think I may want to invest in a calibrated tire gauge so I know for sure I'm running the right pressure. The one I'm using is a Cycle Gear digital cheapie. It could be off and that in itself could be part of the problem.

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Oh. I'm definitely over thinking things. I tend to do that by default. :)

 

On the over thinking front though I think I may want to invest in a calibrated tire gauge so I know for sure I'm running the right pressure. The one I'm using is a Cycle Gear digital cheapie. It could be off and that in itself could be part of the problem.

That is a good plan. Or, if you like the cheapie one, you can take it over to a tire vendor at the track and compare your gauge's reading to one they know is accurate and see how it compares. I have one that reads 1psi low and I just marked the gauge with permanant marker and adjust pressure accordingly, because I like the gauge.

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Hotfoot,

 

Thanks for that suggestion. A lot more cost effective of a plan too. I was looking at $100+ motion pro gauges earlier today. Luckily for me none of them were available for immediate shipment. :)

 

I'm heading to Atlanta Motorsports Park this coming Monday so I'll see if there's a tire vendor that can tell me how "off" the one I have is.

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What kind of gauge do you have ? If it has a removable pressure gauge you can simply buy a high accuracy gauge from a manufacturer like Ashcroft or U.S.G. and replace it,

 

For example you can get a Dwyer DPGA-07, 50 PSI Digital Gauge, 1% F.S. Accuracy ( +/- 0.5 PSI ) and 0.02 PSI Resolution for about 65$.

 

That's better accuracy and 5x the resolution of the Motion pro gauge

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It's a Cycle Gear house brand that I got on sale. Stockton Tool Company. I seriously doubt it's upgradable like that.

 

I'm going to see if I can get someone to check it against a known good gauge on Monday. Might take a bit of doing but I think it would be worthwhile.

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  • 3 weeks later...

I had a similar experience than rchase and was told by Mark Bilt at NJMP that tires pressure on track should be lower than factory reccomendation (which are usually for street riding). I think he brought down the rear tire to 28psi hot and 30psi front. After that adjustment I felt more confortable.

 

One possibility though, is that by lowering the pressure tires get warmer quicker and that in turn improves tire performances, especially for less aggressive novice riders (I know that lowering the pressure increases the heat on tires, it can actually be dangerous if the pressure is too low). I'd like to hear the opinion of another expert mechanic on this.

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Your right on that Spaghetti,

 

Lower pressure = More Carcass Deformation and Flex = more heat, adjusting your pressures can help compensate for extreme weather conditions, lower pressure when its cold for more heat generation , higher pressure when its hot for less,

 

you also run lower pressure at the track for the larger contact patch that is generated by the additional deformation of the tire at lean

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I'll double check and see if Steve Brubaker already covered this. One thing to mention, the factory recommended pressures are not necessarily for best traction. It will be the overall deemed safest figure, there's a bit of CYA that has to be considered.

 

Too high pressure, just lowers the contact patch. Too low (as mentioned) deforms too much. Sometimes we hear a rider using one pressure for the street (substantially higher) and another for the track. I don't quite get that. Well, I do, but I wouldn't personally do it. Unless riding with a passenger, or otherwise heavily loaded.

 

Jacking up the pressure to get better mileage is one stated reason. After I watched my first bike sliding down the road about 1979 (one factor was I let the tires get too worn) I stopped worrying about a little extra mileage/life out of the tire.

 

Tires are the single most critical factor in traction, and letting them get worn/old/dry/thin/too high in pressure/too low in pressure for optimum traction--not worth the trade off. But that's just my opinion.

 

CF

 

I did go check, and on the first topic by Steve there are links covering this subject. http://forums.superbikeschool.com/index.php?showtopic=2587

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I ran warmers for the first time at the track yesterday. I adjusted the hot pressure on my Q3's to 32/26 based on some advice from someone I really trust and it worked quite well for me. Track temps were 42 degrees in the morning and barely climbed to 72 degrees before the sudden storm that sent us all scrambling to get our trailers packed and keep our ez up's from being blown away. I had plenty of grip all day and had very little concerns with grip.

 

I agree 100% with Cobie. Tires are cheap in the grand scheme of things.

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Sometimes we hear a rider using one pressure for the street (substantially higher) and another for the track. I don't quite get that. Well, I do, but I wouldn't personally do it. Unless riding with a passenger, or otherwise heavily loaded.

 

 

It's entirely possible that running track pressures while street riding could result in improper wear on your tires and cupping, you don't exactly do a lot of miles bolt upright on the track so the tire wear pattern's would be considerably different.

 

 

I also think Cobie would give me a stern talking too if he saw my used tires when I pull them off my commuter bike :ph34r:

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This is what I gather, after reading countless web pages and hearing various opinions about track tires pressure, like Q3, michelin pilot power or similar:

- start with 30/30 psi cold as a rule of thumb
- front tire usually carries 2-4 psi more than rear
- rear can go as low as 28psi and up to 34 cold, depending weather, track conditions and riding style
- 1 psi change will do almost nothing, so go by at least 2 psi change
- difference from cold to hot should carry 2/3 psi change as rule of thumb, but it's relative to weather or track. If the change is higher than that tire pressure might be too low.

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It's interesting. When I first got my S1000RR I was a bit smitten with the power that it has. Running track pressures of 31/30 and being super greedy on the throttle occasionally when no one was looking I was getting noticeable wear in the center of the rear tire. Adjusting the pressure up a few PSI eliminated this as well as not being as much of a squid helped stop the uneven wear. :)

 

Now that I'm used to the bike and not marveling at how quickly the numbers flash by on the display I don't adjust my street pressures anymore unless I'm using something really low. I'll probably adjust my pressure to 32/33 since I was running 32/26 on my last track day. I tried the factory pressures that BMW recommends and it was awful.

 

I love the longevity that the Q3's have but I'm considering trying the Pirelli's that the HP4 come standard with for my next set of tires just as a comparison. I'm sure the Q3's will last the rest of the track season and still have plenty of life left when I replace them in the spring.

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