Tire Compound/Manufacturer Questions

[Tim]

I have some questions about tire compounds that I was hoping someone could help with. This is for a FF running in C-mod in Solo2, but I was hoping that those with any information could chime in. We have been running Goodyear R120 compound tires and have been happy with the results in warmer weather, but have found that they aren't as favorable when the temps drop considering the short amount of time we have to get heat into them. Our only other dislike Goodyears has been the cupped front tires that we have tried to avoid through selection, but all of them seem to have some amount of it (another issue really). It has been suggested to try un-cut rains (R080 compound) for cooler weather as one option, but we are concerned that they wouldn't hold up. Has anyone run the un-cut rains in cooler weather that could offer some feedback? I realize that in roadracing maybe this isn't as much of an issue as it is for Solo2 but was hoping someone would have some input.

Another option is to try the Hoosier R25A tires. Others who have done back to back comparisons with the Goodyears found them to not transition as well, but they are slightly different diameters than the Goodyears so if the car setup wasn't changed the data may not be valid. There are certainly a lot of drivers using these in Solo2 and they seem to have an advantage in the cooler weather, but we have also seen were they seem to have lost some grip as compared to the Goodyears when it gets really hot out. This could maybe be compensated for by going to the next harder compound however. Anyone with any comparison info between the Goodyears and Hoosier tires?

One other possibility is Avon tires. I know these are popular in British hillclimbing (similar to autocross with short run times) and I believe they use the Avon A15 compound which I think is also their rain compound. I have also seen the A49 compound available here in the states in FF sizes and wonder how that compares with the Goodyear and Hoosier compounds? Anyone with experience with the Avon tires able to offer any input?

Sorry for the length, I'm just trying to look at options here. I'd like to stick with a single manufacturer since I believe that switching compounds would be much easier in terms of car setup that way. Since we are currently setup for the Goodyear tires if the R080 is a viable option for cooler weather without disintegrating, that may be the best option. I hate to get a set to find out they don't hold up very well without it being wet out. Any advice is appreciated, thanks.

Steve Elzinga

[Alan R Guibord]

Bruce Dickey used the GY 080 compound for a while.
I don't know how he liked them other than the fact
he eventually switched to Hoosiers due to his
setup.

[timmy]

Try stirring up Mr. Morgan @ Avon...

Email Address: [email]pmorgan@coopertire.com[/email]
Location: Melksham, Wiltshire, England.
Occupation: Race Tyre Manufacturers
Homepage: [url="http://www.AvonRacing.com"]http://www.AvonRacing.com[/url]
Phone Number: +44 1225 35 7735

In UK they do a lot with cold damp pavement.

He has always seemed very willing to help.

[dc]

FWIW, we ran Avons all season in FC and we liked them a LOT. They have a longer life than the other 2 brands, and behaved very consistently. We plan on using them again next season, too. They were very predictable tires.

Then again, we're just duffers out to have fun. Any way we can simplify the program is always high on our list. I know that isn't very scientific, but for most guys, they are great race tires, and the support from Avon is fantastic. Pete is here somehwere, too... Pete?

[PortlandCARTfan]

Steve/Don, :confused:

The cupping is from too low of tire pressure, too much tire load, and too much camber. This is a difficult balance with the Goodyear 6.0" front tire. I found myself increasing the roll stiffness and decreasing the front camber to compensate. I was also flipping my front tires constantly.

The Goodyear 7.0" may be a good choice to avoid the cupping and the front grip degradation. I have done some brief testing with good results, but I have not developed the car around it.

Bruce Dickey tried the GY R80 ungrooved rains at Nationals two year ago. He went relatively slower on them than the R120. This might be a better choice for cold or on asphault, but the R120 is better on concrete.

We tested the Geiger/Cary car on Hoosiers with good results and finally got rid of the rear tire bounce. I plan on testing with them next year. We need careful tire maintance to avoid melting them on hot days on concrete. Covers (sun shade), water, and R35s may be the answer.

Does Avon has cantilevered rear tires for FF?

[Tim]

Hi Gary, it's just Steve. Don isn't really active on the discussion forums. Since we are both enjoying driving together and having me as a codriver has helped him we plan on continuing for next year. After the lousy performance at Nationals for the Goodyears in the cooler weather I wanted to try to find some options to handle this situation better in the future. We have also tried running a set of Formula-V treated R120's that seemed to work OK when it is cool, so that is another option but it requires two sets of tires since the treated tires only work for one day before going off. We had been running the higher tire pressure to help with the cupping issue but the last couple of events I started to reduce it and I think the tires grip better at a slightly lower pressure. We'll have to do more testing to find out for sure. I think we are running the same front alignment parameters that you are. Someone mentioned that they are moving the Goodyear manufacturing back to the states from Chile, that may help with the QC issues.

Avon makes tires for FF but I have only seen the A49 compound advertised here in the states, I'll try and contact Avon through the info given above (thank you Purple Frog). It appears looking at Avon's site there are a couple of softer compounds as well that may be useful for solo. I'll share any info I get with you guys, and if we test a set you guys will see them anyway. :) I hope you are able to make more of the Cendiv events next year Gary.

Steve Elzinga

[buggsb]

Gary,
What is this rear tire bounce you are talking about?

Steve,
Sticking to one manufacturer does not guarantee the same diameters when they switch construction of the tire. I had bad experience with my second set of R25A's in that they took a couple of events to come on while the first set was fast right out of the box. As a precaution, I ordered a set before Nationals to scrub at a local event but these were the R25A C2000. At the local event, tires were sticking really well but the handling balance was off. When I got home, I noticed that the car was sitting 1/4" higher which was attributed to the taller tires in the C2000 construction.

Alex

[PortlandCARTfan]

Alex,

We have been fighting a rear tire bounce for several years on the Reynard with Hoosier tires, which is why we have been running GY. Once we would turn in, the rear of the car would bounce and we would spend the rest of the corner countersteering the car to catch it. I have seen many cars have this issue, including Saunders. The GYs were so much easier to drive on that we never fully developed the car for Hoosiers. Testing Gieger/Cary's car on them gave me hope that we can overcome the bounce with carefull shock tuning.

If you have never driven a solo car on GYs on sticky concrete, it is a treat. You do not lead them at all as they transition extremely quickly and consistantly and give you the confidence to run over the base of a cone every lap and not knock it over. They are damn near inch perfect, which is something I cannot say for Hoosiers.

On the down side, the GY 6.0" front is extremely sensitive to set-up and they do not have the construction and compound softness needed to run their best in the cold or on less than optimum surfaces.

Steve,

I will be testing Hoosiers next year. It will take me alot of developement to get the car to drive as well on brand H as it does on brand GY, but ultimately it may be faster. I have been wanting to take brand H contengency money for a long time. Now that I am willing to try them, the competition level is too high to allow me to win it. It is a vicious circle. :confused:

[Tim]

[quote]Originally posted by achiu:
[b]Steve,
Sticking to one manufacturer does not guarantee the same diameters when they switch construction of the tire. I had bad experience with my second set of R25A's in that they took a couple of events to come on while the first set was fast right out of the box. As a precaution, I ordered a set before Nationals to scrub at a local event but these were the R25A C2000. At the local event, tires were sticking really well but the handling balance was off. When I got home, I noticed that the car was sitting 1/4" higher which was attributed to the taller tires in the C2000 construction.

Alex[/b][/quote]Hi Alex, thanks for the heads up on that. Unfortunately the Goodyears haven't been the same diameter even sticking with the same construction. Getting a set has involved mounting several tires and measuring them to find a pair that match each other. Then there is also this issue where some of them have a deep cupping in the center of the tread. This has all been with the 6" fronts.

Gary, if you saw the possibility of good results for the 7" maybe those are worth trying. Don was under the impression that you didn't like the 7" fronts when you tried them out. Brent and Steve have been a lot faster the last two Cendiv events, one was on asphalt and the other was at Grissom in the rain one day (not enough for rain tires) and very cool and windy the next. It looks like they are getting pretty dialed in with the Hoosiers which is great. I had a good event in the cool/wet weather at Grissom and won even with the Goodyears, but the majority of my time advantage was on the wet day rather than the really cool one and Pete Calhoun was still faster that day. I think Pete runs a softer setup than us which probably helped and the rest was just his excellent driving skill, I didn't look to see what tires he was running that day.

Steve Elzinga

[Tonis Kasemets]

Pete was on Hoosiers the first day, like I was. I posted a similar time as Steve, but a cone knocked me down a few spots. >8-( We again ran about equal the second day.

I think Pete has recently softened the rear on his Swift, amd I am still running it stiff. I have also experienced the bounce after running GY and H back to back at a T and T. The bounce is there. Tommy's is quite a bit softer at the rear than mine as well, and I saw his suspension working very well to cancel out a lot of the bounce. I will be trying to find the right frequency at the rear as well to keep running Hoosiers since the quality issues and cold performance remain issues with GY. I certainly liked the feeling of the GY's during my testing....very confidence inspiring. I look forward to next year when I can run them again in comparison. (I only ran the GY's once at a Test and Tune)

[PortlandCARTfan]

Steve,

It is the 6.5" GY that did not work at all in the solo environment on the Reynard. The car bounced on the tire, not the suspension, and I had to lead the car approximately 1/2 mile before the turn-in. The compensation in set-up is stiff springs, tons of camber, and pressures as high as 21 psi. The tire behaves like a radial. Unfortunately for us autocrossers, the transitional charactoristics of the front and rear tires need to match somewhat, and this combination is not even close.

The 7.0" GY is not as precise as the 6.0", but it is not bad. Transitionally, it is probably comparable to the brand H 7.0". The car did much better than I expected in a brief testing experiment on these tires with no changes. I did not want to run too much as these were my 2 cycle R160 road race tires. We can try them in the spring when I am not afraid to tear them up.

[Jon C Brand]

I wonder if this "Hoosier Bounce" phenomenon is really a side effect of springs that are too stiff. The springs don't give, so the tire has to, and perhaps it has less internal damping than the Goodyear.

I've never experienced the Hoosier Bounce, but then I also haven't followed the trend towards a stiff setup. I'm still running the same very soft setup as I was running in 1997 (which isn't quite as soft as Tommy ran on his Van Diemen before he sold it to Gary).

Frankly, I think you guys are all going the wrong direction on springs (or you went the wrong direction, and now it seems like many are coming back down). My car is certainly far easier to drive, much more confidence-inspiring, with the soft setup.

I've also never tested the Goodyears, so maybe I just don't know what I'm missing?

Mark

[Tim]

Mark, do you know what your ride frequency is? I don't have the numbers in front of me right now, but when Don calculated ours I think the rear was around 2.3 Hz or thereabouts. I can't imagine going any softer without raising the ride height somewhat, we already bottom in the front sometimes and had to raise the rear a little recently. I know you were running a pretty low ride height at Nationals, do you bottom out much? I got a face full of cement dust this past weekend at Grissom as I modified the raised edge of one of the cement pads with the leading edge of the belly pan on my last run. :) We have never tried Hoosiers so I haven't experienced the bounce either, but we don't bounce on the Goodyears at all. Maybe as Gary alluded to earlier with the Hoosiers alot of it is in proper shock settings?

Steve Elzinga

[Tonis Kasemets]

Steve, I'm running the stiff "road race" setup and I did not bounce on the Goodyears either. I would not expect you guys to. My previous note basically alluded to the stiffenss/ Hoosier bounce connection. I think Mark is right, softer may be better. My car is pretty stiff, and I find it to be a handfull and very un-forgiving. (Everyone else hates my car and can't drive it, so there must be something to that!) I figured all FF's were this way at first, but as my *** gets more acclimated, I think softer will be more drivable. The fact that this also seems to correlate to the tire bounce problem is just more encouragement to go softer, among other things. Too bad it's SNOWING right now...I'll just have to wait until Spring!

[Jon C Brand]

[quote]Originally posted by Steve:
[b]Mark, do you know what your ride frequency is? I don't have the numbers in front of me right now, but when Don calculated ours I think the rear was around 2.3 Hz or thereabouts.[/b][/quote]I don't know, at least by that term, but I know most of the numbers that go into it. Is it just a function of unsprung weight and spring rate or something?

[quote][b]I can't imagine going any softer without raising the ride height somewhat, we already bottom in the front sometimes and had to raise the rear a little recently. I know you were running a pretty low ride height at Nationals, do you bottom out much?[/b][/quote]Almost never. Occasionally if under hard braking while going over a bump. We run 1.5" under the skid plates, both front and rear.

Mark

[buggsb]

Gary,

Back to the bounce thing. You mentioned it happens right after turnin and I am assuming once the outside rear loads up. Does this happen primarily in sweepers or transitions? We've seen something similar on our car during transitions but it never occured to me that it was a tire characteristic. I've always attributed it to overdriving the corner entry (ie too much trail brake) or car setup. Also, we found that old tires will exhibit this problem more so than new ones. How many runs do you get out of the Goodyear R120's? Blake and I might be interested in at least testing them next season.

Alex

[PortlandCARTfan]

Mark/Pat,

I think the brand H bounce is more a shock tuning issue and not a spring rate phenomenon. Geiger/Cary's car is stiffer than my car by 100 lb/in all the way around. I finally got to dyno my shocks at Nationals...it was ugly. I had much more bleed affect and a lot less low speed rebound than I thought I had. The rear bump adjusters did not function at all....I though I didn't feel much of a difference. Knowing what the shock curves are for Steve and Brent, I have a much better idea how to approach this issue. :confused:

Alex,

The bounce that I sensed was on both sweepers and transitions, but it is much easier to detect in sweepers. The sensation that I got in transitions was that the car was extremely pitch sensitive....any combination of gas and/or brake would cause the car to over-react. I could not attack with the car. Everything had to be a measured manuever. After running the car like that thru most of its first year, the Goodyears seemed like a dream....but I also did not have adjustable shocks at that time to play with. [img]redface.gif[/img]

Washburn,

What makes your car so difficult to drive, besides the uncomfortable seating position, is the slow steering. I physically could not turn the wheel far enough fast enough to keep up with it. Add in the Hoosier bounce, and it is damn near undriveable, at least for me it isn't. :mad:

I can't remember, did you drive the Reynard at Grissom?

[Chapel]

[quote]Originally posted by Gary Godula:
[b]Steve/Don, :confused:
Does Avon has cantilevered rear tires for FF?[/b][/quote]Gary,

Avon offers 7 bias tires and one radial that they say are suitable for 5.5x13" rims. None of them are cantilevers. Not sure which they recomend for FF. See [url="http://www.avonracing.com/frames.htm"]http://www.avonracing.com/frames.htm[/url]

Don

[Chapel]

[quote]Originally posted by Mark Sirota:
I don't know, at least by that term, but I know most of the numbers that go into it. Is it just a function of unsprung weight and spring rate or something?

Mark[/QB][/quote]Mark,

Ride frequency (in Hz) is the square root of ride rate (lbf/in) over corner weight (lbf) times 3.1285, and wheel rate is spring rate times motion ratio squared.

f = (k/w)^0.5 * 3.1285

Don

[Tim]

Don corrected me on our ride frequency as well, we are running about 2.7 Hz in the rear. The ride frequency is basically the natural frequency of the sprung mass. Using it allows you to compare setups between cars with different weights and motion ratios. Don knows a lot more about it than I do though, I ask him for explanations all the time. :)

Steve Elzinga

[B Burke]

I just put a set of the GY 080's on my Zink Z10, which I run in Solo. Only made two events so far, but they are a vast improvement on the 120's I had run in the past. One feature of the 080's that convinced me to try them is that,as noted, they are uncut rain tires. As such, they have a thicker tread depth than the normal slick and for this reason tend to hold heat in them more easily. This feature is desireable in Solo, while not so much in roadracing. As for different diameters, when the Goodyear reps mounted them they measured them and assured me that they were within 1/8" (diameter) side to side. I've got an event this weekend on a concrete site where the speeds should be higher than what I've tried them on so far.

[Tonis Kasemets]

[quote]Originally posted by Gary Godula:
What makes your car so difficult to drive, besides the uncomfortable seating position, is the slow steering. I physically could not turn the wheel far enough fast enough to keep up with it. Add in the Hoosier bounce, and it is damn near undriveable, at least for me it isn't. :mad:

I can't remember, did you drive the Reynard at Grissom?[/QB][/quote]Yeah, but just like you I could not get comfortable enough to really see what it felt like. I did notice the quicker ratio.

I put a note on this forum about the rack ratio, but haven't been able to get any answers. Can anyone help? New pinion gear, or is it a whole new rack?

[Rick Brannon]

Shorten the steering arms.

[timmy]

Washburn,

Did you call Doug Learned 831-899-3636 ?

[Tonis Kasemets]

Thanks for the contact...I'll try him. (Yes, I know I'm getting off topic!) 8-P Roland, can you explain how does using shorter arms quicken my steering ratio? I'm not sure I understand. Thanks!!

[Tonis Kasemets]

[quote]Originally posted by washburn:
[b]Thanks for the contact...I'll try him. (Yes, I know I'm getting off topic!) 8-P Roland, can you explain how does using shorter arms quicken my steering ratio? I'm not sure I understand. Thanks!![/b][/quote]Never mind! Dopey me....I mis-read your note. Shorter lever arms of course make for a quicker ratio.

Just trying *not* to contribute to the notion that I'm a dimwit! [img]smile.gif[/img]

[Racer23]

Data Point regarding what Gary Godula describes as "Hoosier Bounce". I've been running Hoosiers for 10 years. For many years I ran wheel rates about half the corner weights. For a few years I ran much softer wheel rates. Both with OEM Van Diemen Bilsteins. A couple of years ago I changed to Koni 3011/12's and went to wheel rates equal to corner weights. I've never noticed anything like the "bounce" that Gary and others have experienced so I cannot even be sure what it is. Is it something similar to what ground effects cars do when they "pogo stick" sometimes? Basically the change to stiff springs and better shocks simply allowed me to transition the car faster while making it less sensitive to the Forbes Field kind of bumps. The high shaft speed shock valving must be fairly compliant since the "ride" with the stiff springs doesn't get disturbed by bumps any more (maybe even less) than it did with the Bilsteins and softer springs. Plus I can run a lower ride height without bottoming the chassis as often without having to "simulate" rising rate springs with silasto bump rubbers (the only way I know to keep the chassis off the ground with soft springs). Basically the car is really fun to drive and I suspect very easy to drive (it is easy for me). The car just does what I want and "misbehaves" only when driver input makes it do so. The shock valving is whatever Mark Ball at Koni thought was appropriate for springs half as stiff as what I ended up running. Bump and Rebound are set "middle" of the available range. CORRECTION:I have run this setup at Peru and tested with Hoosiers and with GY's. The GY's definitely responded faster than the H's . . . until I peeled both rear GY's off the rims:) An additional comment as an FYI: When I first tried the stiff springs I set the bump valving to minimum. Think FRONT wheel hop when braking over bumps! I could literally see the front tires "hop". Dialed in a few clicks of bump and the problem went away. For what its worth. Dick

[size="1"][ October 23, 2002, 09:09 PM: Message edited by: Dick R. ][/size]

[Tim]

What is your ride height Dick? Mark said his was 1.5" which is just slightly lower than what we run in front (I recall about 43mm) and we bottom out in front at sites like Peru, and Rantoul in our car. I don't recall it ever bottoming at Nationals this year though. That's why I was asking Mark what rate he was running, because unless he is running on a lot smoother sites than we are he must be stiffer than us to not ever bottom out running even lower than us. We have some rake in the car so the rear is higher yet and never bottoms out.

Steve Elzinga

[Racer23]

Steve,

My car is an 85 Van Diemen. The ride height is about 1.75 front (floor pan) and 2.25 rear (bellhousing). The front is actually about 1.5 under an "angle iron" that protects the front of the frame. This is what typically bottoms due to hard bumps under braking. Note the correction in my post above. When checking my notes I found that I did have the stiff springs when I ran at Peru. In regard to Mark's car not bottoming, Maybe Mark is running silasto bump stops. Dick R.

[size="1"][ October 23, 2002, 09:53 PM: Message edited by: Dick R. ][/size]

[Tim]

Dick, we were also measuring from under the angle iron on the leading edge of the frame. The actual floor pan is a couple of millimeters above that. When we bottom out it is usually the leading edge that hits first. I suggested trying some bump rubbers at one of the events and everyone thought it was a bad idea. For me it was causing the front end to wash out when it happened in a corner, just as you would expect it would. One reason I could see for not using them was that usually the bottoming is not due to suspension travel issues but rather uneven pavement, so chances are you would not even be on the bump rubbers when the nose hit on the uneven section.

Steve Elzinga

[Jon C Brand]

[quote]Originally posted by Dick R.:
[b]In regard to Mark's car not bottoming, Maybe Mark is running silasto bump stops. Dick R.[/b][/quote]I do have bump stops on the shock shafts, but the chassis (actually, steel skid plates mounted under the chassis) will hit the ground before the bump stops come into play, except perhaps when cornering.

In other words -- if someone heavier than I am jumps up and down on the front of the chassis, the chassis (skid plate) will hit the ground. But it almost never hits on course, just a couple times per year when braking hard over nasty bumps.

As for the ride frequency we were discussing earlier, I'll have to go calculate that. I still don't understand why it's a more useful number than wheel rate, though. Can anyone explain that to me?

[Tim]

Mark, I think it is more useful than wheel rate when trying to compare cars of different types or significantly different weights. My brother is an ME so he uses it all the time when talking about and comparing different vehicles so he has me thinking in those terms as well. I think using wheel rate is fine for our discussion. I was only asking to see if we were significantly different than you are to address our occassional bottoming issues. I am about 45 lbs. heavier than Don so I think it is probably more of an issue for me than it is for him, the car does ride lower with me in it. Hopefully I will be able to close that gap a little for next year. :) When Don asked around before it seemed like we were kind of middle of the road with some people stiffer than us and some running softer. We were actually considering going just slightly stiffer but haven't really decided yet.

[Chapel]

[quote]Originally posted by Mark Sirota:
[b]As for the ride frequency we were discussing earlier, I'll have to go calculate that. I still don't understand why it's a more useful number than wheel rate, though. Can anyone explain that to me?[/b][/quote]Mark,

Like Steve mentioned, it's a way to normalize the wheel rate to the mass of the car. It also gets you in the ballpark WRT having the front and rear of the car balanced. For a non-downforce racecar, 2 Hz is really soft and 3 Hz is pretty stiff. Passenger cars generally run in the 1.2 - 1.5 Hz range with the rear slightly higher than the front. Early high-downforce F1 cars were up around 10 Hz, which was brutal on the drivers.

My car came with GoodYears, and that's all I've run on it. So I haven't experienced the bounce firsthand. Could be, as Gary suggests, more of a damping thing than a wheel rate thing. I know the data sheet I filled out when I ordered my shocks included tire rate info.

Don