For FSAE............wider tires are better???

[B HATCH]

(fishing for a argument)

My experience with FSAE cometietion and cars ( 3 years) and 2 years of Autocross running cometitivley with a SM Civic, tells me that on Hossiers compound wider tires are best. laps times always go down for people when they get a wider tire with the correct width rim. For raod racing this is not true, this is also not ture if you have a tire that negativly affects your final drive.

Hooisers tire compound heats up very fast, and have very good grip at low temps so heating a wider tire in the front should not be a issue for more then a few gates.

http://www.hoosiertire.com/rrtire.htm

When looking at the tire choices here we can look at the section width for the various sizes, neglecting the gearing of the tire since we cna try to desgin the high difference out. The LEAST wide tire is the very popular used FSAE 20 x 6 x 13 (i have been told this is what most cars run??), where as even in the 10" wide tires the smallest section width is 8.1" on a 6" rim, and you can mabey get some more rubber if you get a 6,5" rim.

My question to you then when choosing a tire, why not get the largest section width for your car. The available data shows the later defection and spring rate to not be far deviadted from a 20x6x13 and the 20x7x13. Both have the same outer diameter. Yet the 7 has more grip on a 6" rim as tests, BUT if placed on a 7" wide rim we would get a larger section width as well as less larter deflection since the tire would sit more sqare on the rim. Of course you can argue that they carrry larger rolling resisistance, more sunsprung weight and also a higher spring rate compared to the popular 13x6x20 but i belive, but can't prove, that if the driver can make use of the increased available grip then the large tire will yelid the best net gains and lower lap times.

I wish i could do an experiemnt and corrillate data on it...

[DHeineck]

(Takes the bait) http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

I think there is a significant difference between you SM Civic and a FSAE car as far as tire choice. I don't know right off the top of my head, but your civic with driver probably weighs about 4 times the weight of a nominal FSAE car with driver. That said, having that much more weight helps put a lot more heat into the tire. You could argue that with a standard sized tire on your civic, you might by overheating the tire dynamically mid turn, whereas a FSAE car with the same tire wouldn't even get it to proper operating temperatures. A cold wider tire may not have the same amount of grip as a narrower tire at temperature. This is especially true at the infinitely cold Detroit track, where any heat in the tires is critical.

In addition, there's a lot to be said about that extra weight brought upon by larger tires. Last year we switched from 8" Goodyears all around to the more popular 6.5" and dropped about 8 pounds a corner.

Now, on a warmer track, a wider tire may have a performance benefit over the 6 or 6.5" tire, but with the weather we've had at Detroit as of late, I'm fairly confident a 6 or 6.5" tire is the best idea.

Cheers,
Daniel Heineck

[Frank]

we're using r25a c2000
we're just about to start testing on 7" (rear)
then maybe 7" all round

just a note, i had a conversation with George the other night, and he saying that 55 deg C tyre temperatures are quite normal

we were reading the Carroll Smith books, and there he suggests 100 deg C

by comparing photos and looking at the tyre, we think we are overheating them in endurance

id argue with the hoosier tyre spring constants
we measured the c2000 13" * 6" on a 6" rim, by two different means, and got the same result each time - 1000lbs/in

even on 6" rims, the 6" and 7" tyre are pretty near the same diameter

i ask the question, does anyone note much improvement running exaggerated camber (inside wear pattern)on these tyres?, we really haven't tried it much, but then again our "testing" has been pretty random to date

we absolutely cannot find 13 * 6 c2000's at the moment

if anyone could sell us a (new) set, we'd be most appreciative

frank

[B HATCH]

Althought my Sm car weights more, the Hoosier As03 compound requires 124 to 140 degrees to start working, my car can make happen in about 4 gates, and i run them at 48 psi cold. Depending on ambient.

But i belive that that the R25A hooiser is desgined to operate best at 50 to 80 degrees, (i read this somwhere last week and can't find it!!!!) which is just a little above ambient air temp in Detroit. So you got grip from the first turn and probalby like Frank stated, they start to peel away near the end of the endurance or if temps reach 80+.......althought the tires do have CONSTANT cooling.....which again i have no mean to fesably caclulate the heat transfer rate of a open wheel tires goin 60 mph.

[jack]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> i belive that that the R25A hooiser is desgined to operate best at 50 to 80 degrees <HR></BLOCKQUOTE>

..if you mean F, not C, that cant be true.

Slip angle is very important!!!

[PatClarke]

Quote Frank ....."we were reading the Carroll Smith books, and there he suggests 100 deg C"

Frank, the old 'Boiling point of water' tyre temperature guidline is more for race tyres that have to endure more weight, more lateral loads and live longer than the tyres we use in FSAE. I would suggest that the temps you are seeing on your FSAE tyres are about optimum for those tyres in that application.
Regards
PDR

[Nick McNaughton]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Frank:
we were reading the Carroll Smith books, and there he suggests 100 deg C
<HR></BLOCKQUOTE>

CS reckoned that's the operating range for dry compound tyres (tune to win, p19) whereas the hoosiers are (I think) wet compounds, and operate between 140F-160F (60-71C). That's in the ballpark for our tyre temps for dry conditions, running Goodyears.

[Charlie]

I have a few observations on these tires, but if you take what I say with more than a grain of salt you are a fool... do your own testing...

The top 4 teams for Detroit all ran the same tire: Hoosier 7.0"

The Hoosier spring rate data was pretty close to our own testing, and I did not even see the Hoosier data until we were done with our test, and it was repeatable.

Along with tire pressure, wheel width seems to have a rather large affect on spring rate. Probably lateral stiffness too?

Hoosier is not the softest tire readily available, so carcass matters too.

Anyway the Hoosier 7" tires for 2004 were about an inch narrow than the 7" tires they offered in 2003. So in 203 the 7" was too wide, now it works. I guess. Maybe next year itll be too small http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Denny Trimble]

Top 5, thankyaverymuch http://fsae.com/groupee_common/emoticons/icon_smile.gif

And we ran the "old" 7's.

[BeaverGuy]

They may have ran Hoosier tires dry but not all of them ran Hoosier tires in the wet. I saw Goodyear rain tires on at least one of those schools cars while they had Hoosier dry tires. And that actually seemed to be quite common.

[Garlic]

I don't think any of the top 5 ran events in the wet anyway. If so it's a moot point.

[mtg]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Garlic:
I don't think any of the top 5 ran events in the wet anyway. If so it's a moot point. <HR></BLOCKQUOTE>

Road & Track was wet, except for Cornell.

[Kevin Hayward]

Garlic,

Would have been very hard for the top 5 to finish as the top 5 if they ran in the wet.

But there were some fast cars running in the wet during autocross ... interesting to see what tyres they were running.

Kev

[Christopher Chow]

Do you know what wheel width those 4 top teams where pairing up with their Hoosier 20"x7"'s ?

Chris

[Frank]

we're testing on 30 deg C days

we tried the 7 inch c2000 ra25's on the rear

liked 'em much better than the 6's

much better heating indications

we're considering 7's at the front now

except... hoosier (the manufacturer) now say they're out of 6's and 7's http://fsae.com/groupee_common/emoticons/icon_frown.gif

we'll be testing on Avon 7.2's (all round) next week and hoosier 6's front 7's rear to get some "back to back" data

its nice having a tyre sponsor

Frank

[Cement Legs]

What tires widths were the above 5 teams using for wets?

Cheers

[1975BMW2002]

I'm surprised that nobody has mentioned that a wider tire is not as forgiving when you start running higher camber. It varies from tire model to model, but it is almost always true that within a model a wider tire will run better at lower camber angles than higher ones. If your car puts the car at anywhere near three or so degrees cambered over(the actual angle with the mavement, so look at roll, and any extra camber induced by kingpin/caster) you wil start losing grip with the wider tires before you will with the narrower ones.

I don't see any need for anything wider than 6 inches. Wollongong had some skinny wheels two years ago.

[alfordda]

Frank-

What size rims are the Avons going to be tested on?

Is it the A45 compound you are testing?

[Frank]

alfordda,

on 6" rims

[spencer harp]

Last post was in 2004, anyone want to shed some new light on the subject. I am working with a company to develop a FSAE specific tire and would like some input. What are you "ideals" when looking for a tire.

I personally think that at the end of the endurance their shouldn't be a tire left. The Hoosier R25B compound seems to be a little hard. I know when they developed this tire the majority of the cars in that era were 500+ pounds. The new chassis including our teams was under 400, and with no pre heating, skidpad, acceleration, and autox suffer from a cold tire.

Our team has tested 6" tires, 8" tires, and 10" tires and I can tell you from experience that a cold 10" is better than a cold 6", and 2/3 of the dynamic testing is done on cold tires. Any Toughs?

[whiltebeitel]

A compound that can provide a consistent level of grip though endurance is important, not just that it has some rubber left at the end.

The level of grip that can be provided at near-ambient would make a big improvement in the dynamic events you listed.

From a design perspective, a tire with a significantly smaller rolling diameter would be great to see, as the cornering stiffness could be improved, the loads to the lower control arm would decrease, etc. I'm not worried about the extra fatigue cycles, as that's not the limiting factor in the hubs/wheel centers IMHO.

What 8" and 10" tires did you test? Avon, Hoosier for the 10" tires? I wish Goodyear still made their 10" tire. 6" tires are not allowed for FSAE, so they don't do us much good.

I'd love to see a competitive 8" tire. Like a Minicup tire with a certain compound... http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Kirk Feldkamp]

Originally posted by whiltebeitel:
What 8" and 10" tires did you test? Avon, Hoosier for the 10" tires? I wish Goodyear still made their 10" tire. 6" tires are not allowed for FSAE, so they don't do us much good.

I'd love to see a competitive 8" tire. Like a Minicup tire with a certain compound... http://fsae.com/groupee_common/emoticons/icon_smile.gif

I think he means width. http://fsae.com/groupee_common/emoticons/icon_wink.gif

I would also like to see a tire for a 8" diameter wheel that's not as hard as a brick. I think it would revolutionize the state of the art in FSAE!

[exFSAE]

Hoosier has the formula for a R15 tread compound, which as one would expect is "softer" than the R25.

Goodyear has tread compounds "softer" than what they currently use.

There's a reason why they aren't in use. There's such a thing as too soft for FSAE. Also, I completely disagree that at the end of the event there should be no tire left.

Want a FSAE specific tire? Go buy one. They're out there, that have been developed over the course of a decade and are pretty tuned in at this point.

[theTTshark]

Yeah we enjoy having tires that can last multiple events. Saves a lot of money. Unless they made tires for free, then make it as sticky as they want!

[Steve_Chung]

We have issues keeping 9.5x13 R25Bs from overheating.

Not sure if you guys have seen the tire cam from SCCA Nationals, but the tire deflects a LOT. Would like a stiffer construction if at all possible.

-Steve
Maryland FSAE

[whiltebeitel]

Originally posted by Kirk Feldkamp:
I think he means width. http://fsae.com/groupee_common/emoticons/icon_wink.gif

I would also like to see a tire for a 8" diameter wheel that's not as hard as a brick. I think it would revolutionize the state of the art in FSAE!

Ha, I'm always looking for a smaller tire, must be the tunnel vision!

On another note, softer isn't always the answer. I'd like to see something with more cornering stiffness and a higher grip level at lower operating temperatures.

Oh, and Maryland is at the far end of FSAE cars with A-mod sizing and wings on wings on wings. I saw the video, I'm not surprised you guys were cooking the 10"ers up front. Lots of download on a big car at high speeds.

[DougMilliken]

... I would also like to see a tire for a 8" diameter wheel that's not as hard as a brick.
It probably can't be tested for combined drive-brake-cornering by the FSAE Tire Test Consortium. Loaded Radius (RL) is too small for any test machine that I'm aware of. Cars made for a small tire might be very competitive, but, vehicle dynamic analysts will be unhappy without full tire data. This may have an effect on their contribution to Design points?

[Kirk Feldkamp]

Originally posted by DougMilliken:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">... I would also like to see a tire for a 8" diameter wheel that's not as hard as a brick.
It probably can't be tested for combined drive-brake-cornering by the FSAE Tire Test Consortium. Loaded Radius (RL) is too small for any test machine that I'm aware of. Cars made for a small tire might be very competitive, but, vehicle dynamic analysts will be unhappy without full tire data. This may have an effect on their contribution to Design points? </div></BLOCKQUOTE>

Sounds like it's time to reinvent the wheel, so to speak! The OD would still be on the order of 15.5" if that helps (based on the 8" ID tires on the market right now).

Personally, I'd gladly lose a few design points for a dynamically competitive (superior?) car.

-Kirk

[Thrainer]

All FSAE teams which are designing their own tyres which I know of (Darmstadt with Pirelli, Eindhoven with Vredestein) have chosen bigger wheel diameters (15" if I remember correctly) with 20" OD. There must be reasons for that.

*edit*
It was not my intention to suggest there is one best concept. It would be interesting to see how other tyre sizes are competing.

[Kirk Feldkamp]

There are many different methods you can take to building FSAE cars (single, twin, four, eight - turbo, supercharged, NA - 10's, 13's, 15's... the list goes on and on). I'm sure they have their own reasons for going down the path that they did! That doesn't mean their reasons fit your (or my) approach. Gotta love FSAE - there's no one "right" answer! http://fsae.com/groupee_common/emoticons/icon_smile.gif

-Kirk

[Zac]

Originally posted by Thrainer:
All FSAE teams which are designing their own tyres which I know of (Darmstadt with Pirelli, Eindhoven with Vredestein) have chosen bigger wheel diameters (15" if I remember correctly) with 20" OD. There must be reasons for that.

That could be something as simple as a manufacturing limit. Since 13" and 14" sizes are relatively uncommon anymore as OE fitments many tire factories no longer contain the tooling to manufacturer those sizes.