Tire pressures for twisties

[OB_Kirk]

I've ridden with a couple of R1s, a TL-R, an Aprilia RSV Mille "R", and numerous ZX-9s and such. They all run and recomend lower tire pressures than the 42psi specified by Suzuki for my Bus. They also run slightly different pressures front and rear. I still have the OE "J" spec BT-56 tires. I'm not looking for speculation, I'm looking for advice from road racers with experience on street tires. Thank you very much and God bless.

 

[OB_BarryW.]

The endurance team I raced for last year was owned by the regional Dunlop race tire distributor. He kept me in D207GP race takeoffs for my streetbike ('97 ZX9R, heavy as a Busa), which I ran at 32psi front/rear in the twisties. When I ran street compound tires I ran between 32-35psi. I've run my Busa at 36psi fr/rear and also at 42psi fr/rear (Bridgestones). I preferred the feel at 36psi, however I don't like the Bridgestones in general and will be trying Pilots next. The Dunlop guy said he wouldn't run above 36psi on the Busa, but I don't know how much he knows about streetbike tire setup.

[This message has been edited by BarryW. (edited 21 June 2000).]

 

[OB_Wegs]

Kirk, I was never really comfortable on the BT56's that came stock on the Wegs Bus. I tried the rec'd 42psi f/r as well as 36psi f/r. The 36 felt better but still didn't get comfortable. I spooned on a set of D207 streets and immediately felt much more secure in corners. As we were about to leave on a big long shred to Arkansas and back, (from Houston), mileage was a concern, so I ran 40psi cold f/r. on the leg up. Once in Ark, I lowered pressure to 38psi cold f/r. The tires performed flawlessly in the corners (and there are bunches of those in Ark). I ended up getting about 3200 miles out of the set. I haven't tried the 207's at lower pressures, but I would imagine for street use, 34psi f/r would be fine. That pressure seems to work well on my 916SPS which is maybe 100 lbs lighter.

Hope this helps,
W

 

[OB_JokerJ]

For what it's worth. I run with my tires at 36-37. Once they really heat up the pressure rises to about 40-42.

 

[hangman1300]

for the best tire pressure start at 30 front and 33 rear. do a couple of hot fast laps if the air pressure rises more than 10 % from what you started at then take one psi out and run another hot lap. if the pressure rises more then 10% than add 2psi. i was running 31 front and 34 rear and it was just right. that was with a stock busa with stock front and d207 rear.

 

[OB_Johnnycheese]

OEM tires running with a 12R twisties
ran 42/42 no problem

 

[OB_CuriousMike]

Damn guys... it scares the crap outta me seeing some of you running 42psi in the front.
I guess I just equate that to being too hard, and the front pushing sooner.

FWIW, I left the lot on my bus at 36/38, and had to do 1 minor correction last week to keep it there.

The few twisties I've done so far, I get good feel from the front end, and the rear develops a good texture.

42... eeek. I'm sure it's something to do with the busas weight, wheelbase, or the Bridgestones tire construction... but I have to say, eeek.

 

[OB_Kirk]

Hangman, could you please elaborate. I'm not sure I understand you. For what it's worth, I've been working my way down. I'm at about 36/36, and I notice that the front end doesn't push anymore. I am also learning the importance of getting some heat into the tires before riding in an enthusiastic manner. Thank you all. Keep it coming. God bless.

 

[OB_Hyper]

BT56 non original set at 30/32 worked fine for me at the last track day and for day to day street use provides a softer ride. This is the street compound. You will not need R compound for any reason unless you are competing in a race for a plastic trophy.

 

[OB_ZXALAN]

WEGS, you from Houston?

 

[OB_DangerMouse]

My two pence/cents worth...

You run lower pressures to compensate for extra heat generated by hard riding, a hard riden tyre should end up inflated to slightly higher than the manufacturers specification when hot, PSI is worked out by the weight and weight distribution of the bike.

A very under inflated tyre will wear very quickly and initaily (until it warms up) will have a deformed "footprint" leading to less grip and (against most people preconceptions) will cause less grip in the wet as the centre of the footprint will not cut throgh water as the fatter footprint encourages aquaplaning.

For the wet let enough pressure out to encourage quicker warm up but not enough to alter the footprint of the tyre.

Avon Azaro IIs are designed to run at the recommended pressure only, and disperse heat so quickly that they no not need air let out for track use.

BT56s will rapidly over heat and chew up if under inflated by a large degree - especially on a heavy bike like a Busa.

I used to run 30/31 on the track 36/36 on the road (pilot races) on my R1.

On the bus I don't drop below 36 PSI ever road or track (Pilot Sports) as the tyre seems to suffer for it with terrible wear if you do.

 

[OB_valklex]

I have a question on this matter. All my previous bikes (hondas) had air pressures for 1 or 2 passengers, and the busa has only one, so it has to be the one for a fully loaded bike. I always ride solo, and I weigh 155 lb. Do I really need the 42/42? That's what I'm running now, but I would like to lower to 36/36 all the time (twisties and high speed), and hopefully have the same wear as 42. I don't think with my weight I'm making any difference in foot print at 36 than at 42. Any opinions?

 

[hangman1300]

the 10%rule is used by most road racers. by using the 10% rule takes into account bike , rider and gear weight. the p.s.i. increace is do to tire flex. the footprint is NOT distorted if they are radials. for running in the rain, you should air up some to make a smaller foot print to cut threw the water and you are less likly to hydroplain.

the best p.s.i. to start at is check the dunlop board in the pits. it will tell you what is a good p.s.i. and go from there.
remember p.s.i. up air down 1 p.s.i. air p.s.i. still up or higher air up 2 p.s.i.
you want max. traction on the track who gives a f... about tire wear. the tires will need to be change before the tire tread is bad because it goes threw too many heat cycles and the rubber brakes down. thats why you see tire warmers on the race bikes, its not to have the tires sticky its to limit the heat cycles they go threw.

(i went threw a dunlop tire school seminar )