Have heard mixed answers. What is a good cold temp AX tire pressure on Hoosiers???

Hi Rob,

How did you like the hoosiers compared to the kuhmos?

I've heard that the hoosiers are quite a bit lighter, I was curious to see if there was a noticeable difference in handling.

Bill

They are different. I don't have enough experience with them yet, but I found myself plowing around tight corners more than I was used to with the Kuhmos. I'm thinking the 30 lbs I was running may have been too much. Trial and error.

BTW- you took TTOD. Look for the AX results in a couple of days.

30 should be HOT pressures. Not cold. Start out at 26 or so. I havent been around the Hoosier AutoX tires in almost a year.. but 30 is too high for a cold Road race Hoosier. I'm betting it is too high for a AutoX tire.

Rennshift arrived. I'll be down tomorrow.

Bill.. you want a Rennshift ?? I bought two.


B

Awesome on the Rennshift. Thanks! Just in time for Sat.

I'm going to try and leave the car at Tony's tomorrow around 7. I'll try 26 lbs cold on Sat, hopefully with better results.

The Marina AX was a fun day. The course was long and different with 4 straights and what felt like 30 turns. I was sore this morning, but I golfed OK today. Marina usually posts times of 40-55 seconds - the average Saturday was about 1:20! Bill drove like a madman and the Boxsters did very well.

I'm not sure how I did overall (not place but skill). I felt like I drove the car, but I need to pay more attention to learning the track, keeping the lines, and not depending on 10 runs to figure out the course.

The car feels good, but I need to increase the oil pressure ASAP.

The guys up here run their Hoosiers around 40 psi hot

Hi Rob,

It seems like you were moving pretty good for never having run hoosiers before. I've heard that hoosiers don't like as much air as kumhos as well. I believe you were easily the fastest Bi car out there. I thought the course was great!....if it were banked, that middle section could be called talladega! (3rd gear, flat out!)

B, I haven't been keeping up. What's a rennshift? I've got a weltmeister short throw in mine right now. Is a rennshift something similar?

Thanks,

Bill

I'm on CRACK . Chris is correct. 40 HOT. We start off at 36 cold for road racing. I'm betting you could start off at 38 cold.


I really really need to attend an event with you..


B

I'll be attending events soon!

Once I either get some tires, or pound my fenders (all 4)

Andrew

hoosier dot-r's run that high of pressure? wow....I thought it would be alot lower than that. When I was running kumhos they liked 35 to 36 hot. They seemed to get greasy any higher than that. The canti's i'm running now run at 24 to 26 hot....they feel real elastic...but I know they are of different construction so there are no similiarities.

I'm thinking of buying a set of hoosiers for my 930 to trot out occasionally at an auto-x and DE....do you suggest 17" or 18" wheels/tires?

Thanks,

Bill

17's.. the tires are cheaper and you have more of a selection in sizes.


The Rennshift is a new shifter for our cars. R-1 is in a spring detent along with 4-5. The shifter sits in the 2-3 plane when in neutral. Basically it keep you from nicking reverse when upshifting to second. You can use your palm and shove the shifter forward without thinking about the shift. It "wants" to go into the 2nd gear plane.


B

oh man...that sounds like the ticket! my wife has been nicking reverse quite a bit when trying to shift too fast. What's the damage for it? you can PM me if you want.

Thanks,

Bill

My last set of Hoosiers I got from Tire Rack and they came with a little info sheet. For a 1800 to 2200# car they recommend 31# to 36# COLD pressure and 39# to 42# HOT pressure. It takes a little getting used to. They feel slippery at first. You really have to get them heated up before they start sticking well.

Rob,

You drove well and smooth: I need to emulate if I'm going to do more Autocross. Still sore from that day too.

Always fun watching Bill out there laying rubber on the track.

Stickey tires would be nice.

Pat

We ran Hossier autocross tires and now Kumhos on the track. the pressures were almost identical. HOT pressures of 37.5 in the front and 41 in the rear. Of course you own a pyrometer and are measuring what you really should have...;-)

Chris

What size front sway bar do you have Chris ??.. from watching you drive the car... I have always felt you where sliding the ass end around and people getting out of your car have made the same comment to me. It would explain the higher rear pressures (unless the tires temps are even front to rear). Just wondering if the rear end is loose and needs to be tightened up.. or if its just the way you drive. Typically cars with POWER are driven this way..LOL



B

The tire temps are very good across the tire and very similar front to rear (you are right, the rears are a bit hotter, but not much...you know we carry almost 60% of teh weight back there). We have 180 lb. rear springs. The fronts have (from what I remember) the 23mm hollow torsion bars and 21 mm anti-sway bar set at about half firm. The car is very well balance. It will go into a nice 4 wheel drift at turn 2 at Thunderhill which is a perfect skidpad test.
What are you trying to say about my POWER. What's wrong with running on 3 cylinders with a Bus cam?
You have to drive the cars hard to get good times..;-) People that rode along were probably used to a car that understeers. Our's does not.....
Both my dad and I like the way the car is set up. Either we both like a bit of oversteer, or we both think it is neutral. My feeling is the latter. Come out sometime and I can take you out....

Chris

Wow, 23mm front bars and 180 springs and you dont understeer. I was plowing like a pig with 180's and 22 up front

Neutral is gud.
Power is gud.

Neutral + power=power oversteer....fun !

I run the Hoosiers at 35 cold.
I ran the Kumhos at 26 cold.
Are these best? Who the hell knows? Do something and stick with it till you KNOW better.

We (unfortunately) aren't f1 test drivers. Those guys can reel off laps within a couple tenths, make a change and get quantifiable results. I just poke and hope.

I checked, actually sway bar is 22mm. Nope, no understeer. We are running about 1.9 neg in the front (because that's all we can get) and I think something like 2.7 neg in the rear (I need to check). Did our own home "professional" alignment. Running very slight toe out in the front and slight toe in in the rear. Caster is about all we can get in the front (a little shy).
We own the track record at Buttonwillow which is a very demanding mechanical grip circuit. We are just off of the record at Laguna Seca and Thunderhill (both directions) by about 1 second...all because we are not running Hoosiers (good for 2+ seconds easy).

The trick is to use your pyrometer. It does not lie. Get your temps even across the tire and try to get the same front and rear. We get dead even across the tires in the rear and they run about 10-15 degrees hotter than the fronts. The fronts, we are limited to 2 neg and our outsides still run a bit hotter, but you set the pressure so the middle is the average of the inside and outside.

Seriously, get a $100 pyrometer. It will save you at least that in tire wear....

Good luck,

Chris

J P Stein,
Your cold temps for the Kumhos seem close to right, a little low I think though. We set at 27-28 in front and 31 in the rear. 35 cold for the Hoosier seems too high. Obviously, it depends on the day's ambient temperature (roughly 1 lb for every 10 deg F tweak). The best way to figure it out is to get it set right hot and then just check your pressures the next morning...

Chris

What I've found is that the Promised Land with Hoosier AutoX tires is to get them hot, as quickly as possible, so that they get sticky. In an AutoX venue there isn’t lots of time to do this, as most runs are only 40-60 seconds.

The real technical question is whether a tire will get hotter more quickly running lower pressure (along with the corning loads) or higher pressure. Any tire engineers out there?

What I found was that was that lower pressure worked, so I’d start out at 24 lbs and adjust to that after each run. When you got the tires hot enough, to get sticky, it was like driving a different car and the times reflected this.

One of the Sacramento PCA guys told me to try lower pressures and it worked. BTW this was entirely contrary to all other advice I had heard.

What's the difference in thought between 24 cold and 36 cold. BTW I ran 30 cold and felt like I was plowing at low speed turns.