Tire Pressure

[Carlos Torres]

Our team is using GoodYear Tires. Which pressure do you use.. In the data GoodYear give, they say 15 psi. Is that the pressure to use or you use more or less in the competition??
http://fsae.com/groupee_common/emoticons/icon_confused.gif

[Patrick W. Crane]

to figure it our, take tire temps from the inside, middle and outside of the tread next time you test. if teh centers are to hot, let out some pressure, too cold? add some.

the 15 psi rating is based on a heavier car(i think) so don't trust it.

[Nicholas]

In the past my team has used 11 or 12 psi as a base, but Patrick is right... a pyrometer is the only way to find out the "right" pressure.

[Carlos Torres]

Which is the max Temparture found in FSAE Eventes?

And It´s really necesary to use a pyrometer???

[Schulberg J]

A pyrometer isn't absolutly neccessary, you can go off of lap times, driver feedback, etc... but having a pyrometer makes it much easier to make intellegent choices about tire pressure. I highly reccomend investing in one. Once you start using it you will love it and wonder how you got by without it before.

Jason Schulberg
Cal Poly SLO Team Lead

[GTmule]

or a well honed thermocouple and a multimeter, for the poorer among us http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Erich Ohlde]

I've got a question for u people using Goodyear. What tire size do u use and on what size rim? we've been having bad wear problems on the inside of the tires and its not from static camber

[Frank]

or you can look at the tire

[fsae racer]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by jayhawk_electrical:
I've got a question for u people using Goodyear. What tire size do u use and on what size rim? we've been having bad wear problems on the inside of the tires and its not from static camber <HR></BLOCKQUOTE>

How is your toe control? do u have a narrow toe base btw ur uprights/camber plates?

-nm, your toe control looks great, but what is your static toe then? On a different topic, this is the first year that we will running cv's inside our rear uprights. Do u know what kind/size of wheel bearings you guys used in the rear drivetrain last year? Hope this edit clears somethings up. Its late, and my typing is going much slower than my brain.

[Erich Ohlde]

What exactly are u asking?

[Carlos Torres]

guys, any ideas on max tire surface temperature?
Thanks

[Ben Beacock]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by jayhawk_electrical:
I've got a question for u people using Goodyear. What tire size do u use and on what size rim? we've been having bad wear problems on the inside of the tires and its not from static camber <HR></BLOCKQUOTE>

We have the same problem with our goodyears. (20x6.5/13 on 6" rims) We're down to about 1deg of camber and they still wear the inside bad. I have a feeling it has something to do with ackerman/toe, so I've made it adjustable this year.

[Kevin Hayward]

Ben,

Are both the front and rear tyres wearing really bad ... or just the front?

Some things do not show up with a tyre pyrometer because some really high peak temps on the edge of a tyre go down almost instantly.

How much caster do you run?

Kev

UWA Motorsport

[Frank]

with pyros

we found 60 deg C (averaged) meant you were in danger of cooking the tyre

now caroll smith says 100 deg C in his books, he is talking about hard tyres

but i found out recently that even some heavier cars like sedans only see 60 deg C

we also found that pyros tended to incourage you to deflate the tyre too much, i do not have a physical explination for this

[Ben Beacock]

Kevin,

we run 4.4 deg caster in the front, and haven't tried changing it yet.

[syoung]

Interesting, Frank, I'd also noticed the phenomenon of the pyrometer suggesting less than optimum inflation. We use a laser-sighted infra-red "gun" - do you use a probe-type pyro or a similar device to ours?

Possibly the reason for the under-reading is that there's more heat loss from the surface of the rubber towards the edge of the tyres than in the middle, as the sidewalls lose heat too.

Of course, it's the tyre's core temperature (not surface temp) we should be worrying about, hence the benefit of a probe-type pyro. We use the infra-red gun because it doubles as an instrument for measuring temperatures of brake discs, exhaust manifolds, the surface of oil in the surge tank, tarmac (a good estimator of amibent air temperature) and anything else we can think of.

Any suggestions/input to Frank's question?

[Erich Ohlde]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Ben Beacock:

We have the same problem with our goodyears. (20x6.5/13 on 6" rims) We're down to about 1deg of camber and they still wear the inside bad. I have a feeling it has something to do with ackerman/toe, so I've made it adjustable this year. <HR></BLOCKQUOTE>

Here is something we've tried and have had positive results. Run a 7 or 7.5 inch wheel with the 6.5 inch tires. We normally run 6.5 inch wheels with the 6.5 inch tire. We tried running a 7 inch wheel with the 6.5 inch tire and the wear seemed to almost go away. I believe it has something to do with preloading the sidewalls so the tire doesn't roll over on itself when it sees cornering loads.

[Tony K]

Yea, running a slightly wider rim than tire helps quite a bit. We run a 6.2" tire on a 6.5" rim and the wear pattern is quite uniform. Running the larger rim allows the sidewall to be in-line (stand-up straight) with the bead of the rim after the tire deflects from cornering loads. As one would assume, the size difference between the rim and tire depends on the stiffness of the tire sidewall.

[Patrick W. Crane]

when using a pyrometer i wouldn't use it to set tire pressures based on tire temp but relative temp across a tire on teh inside, middle and outside.

[Frank]

using 3 pyros, the temperatures on the outside of the tyre seem to always be cooler...

which (to what i initially thought) meant you should let some pressure out

but for us, we just kept letting pressure out until the tyre was near flat

hence im left wondering, is this just due to tyre geometry?, our suspension geometry? (lots of castor, little camber, hoosiers), something completely different?, typical pyro readings?,

or were we "seeing" something else?

or did we mess up repetitivly? http://fsae.com/groupee_common/emoticons/icon_smile.gif

regards

frank