TIRES: Sport vs Sport-Touring

[Nitro]

I can't believe it...a tire tread! On the S, the single most important thing for tire longevity is pressure. Anything lower than 40 psi and the front cups and the rear does not last. I've had the best luck with Continental tires.

[Supersteve]

Agreed Nitro, although on the road one can run that pressure where longevity is required, I can't run anything higher than 29psi/2bar cold on the track.
Luckily there, longevity is not the biggest requirement, as soon as I'm off the track I go straight back to 2.5bar/36psi for the 3- 4 weeks until the next track day.
Which Continental's are you using? I honestly haven't tried them as yet as very few dealers stock them here.

[Nitro]

I had a few sets of ConiAttack, now I'm running Motion. I buy online only. It seems to me newer tires, as in the last 10 years, really like higher pressure.

[bradzdotcom]

since tires are the first portion of your bike's suspension (yep, they are), nailing the right pressure for the right application (iron butt vs. 3 lap sprint race) isn't easy.

it still screws with my head that the motoGP tires are run at 1 atmospheric pressure.
that's 14.7 pounds at sea level. barometric pressure & altitude change that number somewhat.

and teams get their hands slapped if they add or delete more than a smidgen (technical word).
i like to imagine that they look upon us, with our tire pressures all over the board, with a mixture of lust and loathing.

[pwillikers]

It's a thin line between love and hate.

[Nitro]

Originally Posted by bradzdotcom

it still screws with my head that the motoGP tires are run at 1 atmospheric pressure.
that's 14.7 pounds at sea level. barometric pressure & altitude change that number somewhat.

I understand this is the Internet and one can claim to sport a 12" cock and have it next to a ruler in cm to prove his claim but Moto GP tires are run between 1.5 and 1.9 atm not 1.

They are stll low because the bikes are light, the jokies are tinny, and the sidewall is more flexy than street bikes.

The heavier the payload, the higher the pressure.

I've never had any luck running low pressure on street bikes, on road or on the track.

If you like to waste money in tires, be my guest and run low pressure but you're foolong yourself in believing the huge gain in grip you might have.

[throttlemeister]

Empirical evidence is not actually evidence.

Tire pressures are not about grip, not directly anyway. They are about temperature. Obviously maximum grip is achieved at optimal temperature, but the goal with adjusting pressure is to get the tire in the most optimal temperature range. Dropping pressure means more flex and a bigger contact patch, which results in a higher tire temperature. Get the tire too hot, it will start to smear. Don't get it hot enough, it doesn't provide maximum grip.

For sporty street tires like the S20EVO, the optimal temperature is somewhere between 60-70C (for reference: MotoGP tires run at almost twice that, at 130C but with a very narrow band). This is way hotter than you will ever achieve on the street and will actually burn your skin. For the track, Bridgestone themselves recommend 29F/27R cold pressure and 32F/31R hot pressure for this tire, where the cold pressure is just to get a starting point, and the hot pressure is the goal.

Imo, the big revolution in sporty street tires these days is not the pure grip levels, but the range of temperatures at normal pressures they can be used while giving good grip. It isn't too long ago where these types of tires were almost outright dangerous when ridden in sub-50F temperatures or in the wet. Today, a tire like the S20EVO gives as much grip as it's T30 touring cousin at low temperatures or wet conditions, but with enough headroom to really take a beating on a hot summer trackday. Even touring tires are not doing too bad on the track these days.

Imo it won't be long before the main difference between touring and sport tires is not so much the rubber, but the profile.

[BadToTheBown]

Originally Posted by throttlemeister

empirical evidence is not actually evidence.

tire pressures are not about grip, not directly anyway. They are about temperature. Obviously maximum grip is achieved at optimal temperature, but the goal with adjusting pressure is to get the tire in the most optimal temperature range. Dropping pressure means more flex and a bigger contact patch, which results in a higher tire temperature. Get the tire too hot, it will start to smear. Don't get it hot enough, it doesn't provide maximum grip.

For sporty street tires like the s20evo, the optimal temperature is somewhere between 60-70c (for reference: Motogp tires run at almost twice that, at 130c but with a very narrow band). This is way hotter than you will ever achieve on the street and will actually burn your skin. For the track, bridgestone themselves recommend 29f/27r cold pressure and 32f/31r hot pressure for this tire, where the cold pressure is just to get a starting point, and the hot pressure is the goal.

Imo, the big revolution in sporty street tires these days is not the pure grip levels, but the range of temperatures at normal pressures they can be used while giving good grip. It isn't too long ago where these types of tires were almost outright dangerous when ridden in sub-50f temperatures or in the wet. Today, a tire like the s20evo gives as much grip as it's t30 touring cousin at low temperatures or wet conditions, but with enough headroom to really take a beating on a hot summer trackday. Even touring tires are not doing too bad on the track these days.

Imo it won't be long before the main difference between touring and sport tires is not so much the rubber, but the profile.

+1

[Nitro]

I agree with mostly you have said but the Bridgestone recommendatio is bogus. You can't say to run a specific tire pressure without knowing the actual weight of the bike and the ambient temperature.

Given the same tire, do you think a 320 lbs bike with a 120 lbs rider at 20 degrees would run the same pressure as a 500 lbs bike with a 220 lbs rider at 90 degrees? I don't think so.

I've been experimenting a lot with tire pressures on my dirt bike as well. All the mx wonnabes around here swear by running 12 psi. Well, in my xr it does not work, the marginal gain in grip does not justify 4X the wear, 25 psi seems to be the sweet spot for dot tubed enduro on a 350 lbs bike.

Again, all things being equal , the higher the payload, the higher the presure.

[throttlemeister]

Originally Posted by Nitro

I agree with mostly you have said but the Bridgestone recommendatio is bogus. You can't say to run a specific tire pressure without knowing the actual weight of the bike and the ambient temperature.

Given the same tire, do you think a 320 lbs bike with a 120 lbs rider at 20 degrees would run the same pressure as a 500 lbs bike with a 220 lbs rider at 90 degrees? I don't think so.

I've been experimenting a lot with tire pressures on my dirt bike as well. All the mx wonnabes around here swear by running 12 psi. Well, in my xr it does not work, the marginal gain in grip does not justify 4X the wear, 25 psi seems to be the sweet spot for dot tubed enduro on a 350 lbs bike.

Again, all things being equal , the higher the payload, the higher the presure.

Of course there is a difference in pressure. But as always, manufacturer recommendations are not gospel. They are ballpark figures based on some sort of average. Everybody knows how that works.

Personally, I just run BMW recommended pressures on my R and K, ie 32f/36r for the R and 36f/42r for the K. I only ride on the street and when I run my tires hot they're not so hot that they're leaving burns on my fingers so I have no illusion my VR abilities.

[bradzdotcom]

Originally Posted by Nitro

Moto GP tires are run between 1.5 and 1.9 atm not 1

you sir, are correct.
the new 2016 spec for the new michelin tires calls for 1.5 (21.8 psi) and have a performance heat range of 130 to 135 C degrees to make 'em work. (actual created temps are team secrets apparently, and they all lie, don't know why).

hope you're happy.
the dunlop rep i woke up to ask the question was not. (sorry broc).

i love the tire discussions.

tires are the rubic's cube of motorcycling.

[Jay K.]

Originally Posted by Nitro

I can't believe it...a tire tread! On the S, the single most important thing for tire longevity is pressure. Anything lower than 40 psi and the front cups and the rear does not last. I've had the best luck with Continental tires.

I agree about pressure being critical...not about 40#.
Hanging around in the pits at sports car races taught me to to be very careful about tracking tire pressure...after a lot of experimentation I run 33R/37F on my BCR...and I get good mileage out of my tires.

[sgoodwin]

Originally Posted by bradzdotcom

i love the tire discussions.

tires are the rubic's cube of motorcycling.

Isn't that the truth, a bad set up can turn a perfectly great motorcycle into an ill handling pile of poo.

Been there & done that!

[BikerMiker]

All this talk about the s20! I blew my rear on the way home last night and it's forcing my hand early.

I was thinking of getting the q3s but I found this thread. Any comparisons? I haven't ridden either one.

[BMWR502]

The S21 is out now. Just ordered a set on Monday. $209 for a 120/70 front and 180/55 rear from Chaparral. Also... Bridgestone is running one of those $50 Visa check card deals right now. So no, it is not a true $50 off purchase price, but it's hard to beat $159 for a set of sport tires. I was a big fan of the S20 Evo, I'm sure the S21 will not be disappointing.

[PFFOG]

Great $$ on a set of tires

[BikerMiker]

I pulled the trigger. Really good price. And their website messed up and I ordered 5 sets!

[sgoodwin]

Could of saved a ten spot here....American Motorcycle Tire

[throttlemeister]

Good tip. Gotta try the S21 now too on the R.

While checking that out, I also noticed the T30EVO is now out in 190/55, so that's gonna be the next hoop for the big K. Dont know how they are going to make the regular T30 better, but I guess they are.

[BMWR502]

Going on in a few hours