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Discussion Starter · #1 ·
Ok, Weds night my bike as getting really squirly in the turns. The rear would begin to wallow mid turn at neutral throttle and when adding gas....at times it would start to step out over any bumps.

I haven't changed any settings from my last race, the only difference is that I am running the same tires (a bit worn, but just for practice) and tire pressure was set cold at 29R/31F on Dunlop 208 GP-A (UK rear).

I know that the tire is more worn than during the race, but it seemed abnormally squirly.

I think it may be solved with a 1-2lb tire pressure adjustment....

Should I got UP or Down on tire pressure? What are the symptoms of each?
 

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Ok, Weds night my bike as getting really squirly in the turns. The rear would begin to wallow mid turn at neutral throttle and when adding gas....at times it would start to step out over any bumps.

I haven't changed any settings from my last race, the only difference is that I am running the same tires (a bit worn, but just for practice) and tire pressure was set cold at 29R/31F on Dunlop 208 GP-A (UK rear).

I know that the tire is more worn than during the race, but it seemed abnormally squirly.

I think it may be solved with a 1-2lb tire pressure adjustment....

Should I got UP or Down on tire pressure? What are the symptoms of each?
Wallowing could be pressure, but in reality, it sounds like your suspension needs help. Stepping out is normal when hitting bumps - especially at Nelson. You need to steer with the rear there most deinately. I would say that you might be getting faster and the bike is moving under you more than you might be used to. What were your lap times at Nelsons?

Otherwise, if the bike is skipping, guys are going to give you a million ideas of what it could be. First and foremost, how do you like the bike set up? Hard or soft? Just because one guy likes a hard set up and is used to it skipping and moving isn't optimum to a guy who likes the suspension moving under softer settings. Get my point?

What's your sag? What's your ride height (Also, where are you measuring?)? What's your fork height at? Also, what's your weight?

These are questions you need to know answers to. Giving a basic response on where a bike SHOULD be set is a great starting point and then you can tailor it to your riding habits and style. However, w/o notes and set-up numbers, you're stabbing in the dark...
 

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Discussion Starter · #3 ·
Wallowing could be pressure, but in reality, it sounds like your suspension needs help. Stepping out is normal when hitting bumps - especially at Nelson. You need to steer with the rear there most deinately. I would say that you might be getting faster and the bike is moving under you more than you might be used to. What were your lap times at Nelsons?

Otherwise, if the bike is skipping, guys are going to give you a million ideas of what it could be. First and foremost, how do you like the bike set up? Hard or soft? Just because one guy likes a hard set up and is used to it skipping and moving isn't optimum to a guy who likes the suspension moving under softer settings. Get my point?

What's your sag? What's your ride height (Also, where are you measuring?)? What's your fork height at? Also, what's your weight?

These are questions you need to know answers to. Giving a basic response on where a bike SHOULD be set is a great starting point and then you can tailor it to your riding habits and style. However, w/o notes and set-up numbers, you're stabbing in the dark...
I had my bike set up at GMD. I have all the notes that you talk about...here are the highlights:
-like it on the soft side
-sag 41.5 front R/S
-sag 10mm rear F/S
-I run 15's at nelson
-loved the suspension last race, hated it Weds....made no changes
-tires were a bit shagged on weds (ok more than a bit)
 

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Going up in preassure will make the tire flex less and it will not heat up as well. It will tend to break loose more violently.

Going down on the pressure will make the tire heat up more. Take too much pressure out it can overheat and the tire will become more 'greasy'.

If the only thing that changed since your last race was the tire pressures then that should be your problem. Things to consider though is the track temperature. I'm assuming this is the same track?
 

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Going up in preassure will make the tire flex less and it will not heat up as well. It will tend to break loose more violently.

Going down on the pressure will make the tire heat up more. Take too much pressure out it can overheat and the tire will become more 'greasy'.

If the only thing that changed since your last race was the tire pressures then that should be your problem. Things to consider though is the track temperature. I'm assuming this is the same track?
I was told just the opposite on tire pressure? The higher the pressure the quicker it will heat up and so on. That's why people run like 35 PSI in there rain tires?
 

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If you put 50 psi you think the tire would heat up more than if it had 20 psi? Race tires run hotter than street tires that's why we lower the preassures for the track.
 

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Going up in preassure will make the tire flex less and it will not heat up as well. It will tend to break loose more violently.

Going down on the pressure will make the tire heat up more. Take too much pressure out it can overheat and the tire will become more 'greasy'.

If the only thing that changed since your last race was the tire pressures then that should be your problem. Things to consider though is the track temperature. I'm assuming this is the same track?
I was told just the opposite on tire pressure? The higher the pressure the quicker it will heat up and so on. That's why people run like 35 PSI in there rain tires?
both are true.

lowering the pressure creates more flex and thus more temp.

raising the pressure creates less flex but more tire spin thus more temp
 

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You need a tire durometer and infra-red temp gauge.

Measure your temps as you come off the track. Measure your durometer when rubber is cool.

Increase preassure in the rain to keep treads form closing on you. Decreased tire preassure will result in more carcass flex, thus more heat in rubber.

Coming off track with rains: 78f @ ambient 73f
Coming off track with drys properly infalted; tire duro 55; 165+f at 60f ambient.
Preassures will vary with ambient temp and race surface temps. 1/2 lbs. preassure makes a difference.

Measure your temps, set your preassure until you reach 165+.

Temp gauge you can get at Sears, I have my work's durometer.

YES, knowing this does NOT necessarily make you faster! Before anyone checks my times.
 

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Going up in preassure will make the tire flex less and it will not heat up as well. It will tend to break loose more violently.

Going down on the pressure will make the tire heat up more. Take too much pressure out it can overheat and the tire will become more 'greasy'.

If the only thing that changed since your last race was the tire pressures then that should be your problem. Things to consider though is the track temperature. I'm assuming this is the same track?
I was told just the opposite on tire pressure? The higher the pressure the quicker it will heat up and so on. That's why people run like 35 PSI in there rain tires?
Kip is correct . . . .
 

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Going up in preassure will make the tire flex less and it will not heat up as well. It will tend to break loose more violently.

Going down on the pressure will make the tire heat up more. Take too much pressure out it can overheat and the tire will become more 'greasy'.

If the only thing that changed since your last race was the tire pressures then that should be your problem. Things to consider though is the track temperature. I'm assuming this is the same track?
I was told just the opposite on tire pressure? The higher the pressure the quicker it will heat up and so on. That's why people run like 35 PSI in there rain tires?
both are true.

lowering the pressure creates more flex and thus more temp.

raising the pressure creates less flex but more tire spin thus more temp
You guys are nuts. If he starts with what Dunlop recommends for his tires and reduces the psi, the tire will heat up more and if he does the opposite, the tire will heat up, but less quickly and therefore, when he pulls off the track, it'll more than likely have less of a temp reading. Spin up can occur with lower psi - your suspension can be adjusted to compensate. Spin up is going to happen either way - not with just adding 2-3psi...

Rain tires need higher psi due to a few things, but mostly because they need to keep the flutes open for water shedding and the fact they are super soft - running a regular psi like a DOT race tire would melt them - another example of how higher and lower psi effect a tire.
 

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My tire guy measures my temps ten ft from pit-in. I might lose up to 5-10f from full race temps.

Still, he tells me if I have put too much or not enough pres. in them ~ due to the temps. This is good because any given day will be different. I dial them in at practice and race like hell.

I measure the duro; 45 is where they start, 75+ is where they start to slide unpredictably (Pirelli-last years compounds). Still gathering data on this year's 'stones (002).

When rains get warm, they lose grip.
 

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Wow this thread started to help with his question, but turned into something he wasn't even asking about.
 

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Someone please talk to a tire guy so we can get this resolved. If it's hot do you run higher or lower temps?
 

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There is no SET answer. The only way is to measure your tire temp and durometer, then set your preassures and tire warmers to achieve what you want.

"Tires are like brownies, leave them out and they get hard". -Quint.

I suspect goodmatt78 was riding a 65 point duro in his race. Now we don't know how long between then and when he could not hook up, was the race last FALL? At any rate, a race will heat-cycle your rubber, making it harder. So, he was prolly on a 78 duro tire after racing. If that's the case, he can run 100psi or 10psi, the tire will not get optimum traction at any temp because it's too hard, oil has evaporated and rubber is vulcanized.
 

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Discussion Starter · #16 ·
Wow this thread started to help with his question, but turned into something he wasn't even asking about.
So typical!!!!!
 

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There is no SET answer.
Exactly. However, you need to set the tires to a basic tire psi before you go and mess around. Meaning, start out with 29/31 and check temp and pressure. If you don't have a temp guage (You're not a serious racer w/o one...), you can do a quick psi reading. You should be near 10% above your set psi. In other words, when the tire heats up, the psi will increase.

Anyways, there isn't a "right" answer, but basic tire knowledge says that if you start with say, 30 psi and you check temps and they are too low, you take away psi by 1-2psi incriments and you should then heat the tire. Add if the temp is too high as more air will not allow the tire to heat as much as quickly...

Basically, you really need to get into :10's at Nelson before you start worrying about the tires moving under you and skipping over bumps. At that speed, you are over 8 seconds slower than fast experts and 5 seconds slower than average top novices there. Not saying you're bad - just saying that what you describe sounds more like set-up than psi...
 

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Outstanding Lizard 1!
 
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