Kumho V700 ~ what tire pressure?

JekylandHyde · Post by **JekylandHyde** » Wed Jun 08, 2005 1:53 pm

This will be my first event on a race tire.
Any suggestions on where to start with tire pressures?

Thanks.

Tim Royer · Post by **Tim Royer** » Wed Jun 08, 2005 3:05 pm

Hi,

Depends on alot of things but if that was my car I would start about 28 or 30 the first run then drop 2 more pounds next and see what it looks like. Mark your tires with white inside to outside tread and look at them all up at turnaround. Be glad to show you what to do. Go buy a white paint stick with a wide tip on it.

My Goodyears on the Mustang liked higher pressures like 35 to 38. If it was lower then 35 I would get alot of sidewall scrub and less contact patch on the road. The sidewall would acually buckle under.

Your car will be different because of car weight is lighter and I'm not sure how stiff the side walls are on that tire.

JekylandHyde · Post by **JekylandHyde** » Wed Jun 08, 2005 5:38 pm

Some of the reading I have done indicates that this tire works best wit ha lot of air pressure (like 38-40). That just seems very high to me, especially since they will heat up throughout the run.

I am used to 32-34 tire pressure in my street tires .... and 14 psi in my drag tires

The tires I ever put over 40 psi are the Suburban and trailer.

At any rate, I would appreciate any insights you can give me Tim.
Maybe you can take a peak at my car this weekend?

Joe B. · Post by **Joe B.** » Wed Jun 08, 2005 6:44 pm

Start out at 35 PSI and go from there. V700's like alittle more pressure than the older Victoracers.

Joe Bartek

Tim Royer · Post by **Tim Royer** » Wed Jun 08, 2005 9:44 pm

HI,

Joe's right on that one. Sure could look at it for you. See ya there. Find me and ask, my mind has been on overfried lately.

Guest · Post by **Guest** » Thu Jun 09, 2005 7:26 am

Tim Royer wrote:HI,

Joe's right on that one. Sure could look at it for you. See ya there. Find me and ask, my mind has been on overfried lately.

I ran about 28psi in my v700's.

Steve Tumolo · Post by **Steve Tumolo** » Thu Jun 09, 2005 8:17 am

You also have to consider that on a short hill like Weatherly you will not get the tires up to their optimum heat range until the end of the run (if you are lucky). So starting on the high side of your tires pressure range is where you might want to start. I let somebody talk me into trying 25#'s of pressure up front on my Goodyears once. Then I proceded to peel my left front tire off of the rim in the sweeper before the jump. Not fun.

ps: I won't mention who talked me into trying that, but you know who you are Tim

.

Tim Royer · Post by **Tim Royer** » Thu Jun 09, 2005 12:23 pm

HI,

25psi?? Really, I don't recall that

I'm in the 32 to 35 range depending on the course. The tires will tell you what needs to be changed.

Tim Royer · Post by **Tim Royer** » Thu Jun 09, 2005 12:43 pm

HI,

Good article on your tires.

Tire Break In

The V700 does require break in. New tires will be slippery for their first laps, and will begin to feel better as they get scuffed in and build up heat. We recommend that drivers heat cycle their tires before using them in competition. Heat cycling helps you get the most consistent performance and tread life out of your tires. It is the process of gently bringing the tires up to temperature for a short duration and letting them cool. Ideally, you should break in your tires, remove them from your vehicle, and set them aside for more than 24 hours before your track sessions and races. Often this requires running a practice session on new tires to prepare them for a future race, while you use tires prepared previously for the current race. The Tire Rack offers an automated heat cycling service which can complete this process before your tires are delivered to you.

Inflation Pressures

The V700 will work well on most cars with inflation pressures between 35 and 40 psi ("cold" inflation pressures for autocross use and "hot" inflation pressures for racing use). Cars that are light, well balanced and relatively easy on tires will find slightly lower pressures may work for them, while heavy, high horsepower cars that are generally harder on tires may find that they need slightly higher inflation pressures.

Generally adding air pressure in small increments (2 psi) to the tires on the end of the car that looses traction first works best. For example, if a car is understeering, add pressure to the front tires. If the car is oversteering, add pressure to the rear tires.

Tire Temperatures

Tire temperatures are taken with a tire pyrometer which can measure how hard your tires are working and how evenly the work was distributed between them during the most recent corners. While the V700 tread compound operates well over a broad temperature range, it is most effective in the 160° to 200° F range.

When preparing to take tire temperatures, the driver should enter the pits using moderate braking. The temperature's of the car's outside tires on the last corner should be taken first, followed by the inside tires. Depending on the distance from the last corner to the pits, tire temperatures may not be even across the tread face. Your first goal is to achieve an even temperature spread between the tire's outside shoulder, center, and inside shoulder.

Alignment Settings

Your vehicle's alignment settings can influence the performance of your tires and often can be adjusted to maximize their capabilities. Like most tires, the V700 features a symmetric internal construction and will require negative camber to achieve its full potential. If camber is adjustable, most cars will perform best when camber is adjusted into the -2° to -3° range. Caster settings can enhance straight line stability and cornering traction, and if adjustable, should be set at the maximum positive value for the vehicle. Toe settings may be adjusted to enhance steering response and corner turn in.

Rain Conditions

Because wet track conditions are frequently different and always changing, you need to use your best judgement when selecting tires for driving in the rain. For damp conditions where standing water is not present and water evacuation is not required, shaved or worn V700 tires can be used. Standing water should be avoided whenever possible and V700 tires with nearly new tread depths should be used if any standing water is present. However like all tires, the V700 will be forced to hydroplane when their tread design's ability to remove water is exceeded by the vehicle's speed and/or the water's depth.

Most cars should begin by using cold inflation pressures for wet track conditions that are 5 to 8 psi below the cold inflation pressures they use in their tires for a dry track.

1/8" toe out is good for what we are doing that does a few things for you. Slight tire scrub to get heat in them, and better turn in traction. Because if your throwing it into a right turn with toe some toe out your right front tire will be helping you pull threw the turn. Your left front will have all the weight on it tracking straight while the right tire will be using all the 1/8" toe out pulling the right front tire to the right therefor increasing your turning speeds compared to 0 or toe in.

JekylandHyde · Post by **JekylandHyde** » Thu Jun 09, 2005 12:48 pm

Thanks Tim ... that is where I got the higher tire psi recommendation.
I did have the tires shaved and heat cycled.

I'm not sure what they are considering a "light" car or a "higher horsepower" car.

My MR2 is 2650 lbs (2820 lbs with me) and I am putting down 380 rwph.

Tim Royer · Post by **Tim Royer** » Thu Jun 09, 2005 12:51 pm

That would be you. start at 35 you can see where to go from there.

Toe:

1/8" toe out is good for what we are doing that does a few things for you. Slight tire scrub to get heat in them, and better turn in traction. Because if your throwing it into a right turn with toe some toe out your right front tire will be helping you pull threw the turn. Your left front will have all the weight on it tracking straight while the right tire will be using all the 1/8" toe out pulling the right front tire to the right therefor increasing your turning speeds compared to 0 or toe in.

brandonl · Post by **brandonl** » Thu Jun 09, 2005 2:20 pm

What kind of speeds are you guys seeing at this event? More importantly sustained high speed or fast corners?

Brandon

JekylandHyde · Post by **JekylandHyde** » Thu Jun 09, 2005 2:24 pm

This hill does not get very high top speeds. I'd be surprised if anyone is close to 100 mph. I can get to 90 mph by the first turn.

Duryea and Pagoda in Reading have much faster sections well over 100 mph.

You can see my in-car videos of Weatherly and Duryea here:
http://www.jekylhyderacing.com/HydePhotos.htm
(center column).

Tim Royer · Post by **Tim Royer** » Thu Jun 16, 2005 12:21 pm

HI,

So what pressure did you end up using, and what was the best for your car?

JekylandHyde · Post by **JekylandHyde** » Thu Jun 16, 2005 12:30 pm

lol ... I started at 35 psi cold and it felt fine so I stayed there.

The car felt completely predictable to me and I had more grip than my cahoona's cared to explore so I was plenty safe and fast.

Tim Royer · Post by **Tim Royer** » Thu Jun 16, 2005 12:39 pm

HI,

I must say you did great. After you trimmed down your launch it was looking very fast.

Got an in car from this weekend?

JekylandHyde · Post by **JekylandHyde** » Thu Jun 16, 2005 12:48 pm

Thanks Tim,

Actually of of my runs on Saturdays had errors (miss shifts or trashed launches). It took a bit for me to figure out the launch with the 2-step and those tires.

Overnight Saturday I ended up having major tranny problems. I lost 4th and reverse. Although we did some brake work Sat night, I realyl was not happy with my braking. It is not what I was used to. I think my brake MC is going out on me.

Anyway, Sunday morning I spent a lot of time visualizing the course I realized the one key place that I really needed to take a different line.

I did it on my first run, but was going os much faster into the next turn that I could not stop as well as I wanted so I botched that turn bad and killed momentum.

On my second run on Sunday I got everything figured out. I had a clean launch, nailed the new lines I wanted to try and I braked much earlier than I would have liked to be safe. I was extremely pleased with the 61.1.
I had set the SM2 record in the fall at 63.2, so improving over 2 seconds was enough for me to park the car for the day.

I did not want to throw the car away on questionable brakes and/or tranny. It sucked that I missed out on a good 8-10 runs, but at least I still have my car.

My in-car video of the 61.1 was posted here (that's the most air I have ever gotten on the jump):
http://www.pahillclimb.org/phpBB2/viewt ... ight=#1878

JekylandHyde · Post by **JekylandHyde** » Thu Jun 16, 2005 12:48 pm

oh ... and thanks Tim for all of your help and advice.
It is really appreciated

Tim Royer · Post by **Tim Royer** » Thu Jun 16, 2005 1:00 pm

HI,

Looks good. I know the road was pretty bad. There's 57's secs in that car easy. Once the road is paved you should be hammer down from the jump to the finish. Turn 1 can be taken much deeper and faster not much braking is needed in that turn. Lookin good though bud!

JekylandHyde · Post by **JekylandHyde** » Thu Jun 16, 2005 1:21 pm

Thanks

Turn 1 I was still braking like I was on street tires ... I got braver by that run. I kept getting surprised as I was anticipating trouble in 1 and those 265s out back just stayed glued, hence my comment above about the tires gripping more than my cahoonas

I feel Hyde is a sub-60 second car as well, but I want to feel my way into those kinds of times. The run in the video I was concentrating on being smooth and just nailing everything ... not so much pushing the car.

I need to resolve my brakes.
That will bring a lot more courage back to the run.

From the jump on I feel great about getting on throttle, but I hate the finish ... that is the scarriest part of that hill (or any of them I have tried).
I cross the finish so fast and that road just goes in a stupid direction for 90+ mph

... again, that will feel better with better brakes.