Hoosier Street TD & GTA Alignment Questions

[italcarguy]

I just got accepted into General Racing's "Coronado Festival of Speed" with the GTA. Their rules require that I run Hoosier Street T.D. tires. Where are the best deals at for these tires. I'll be looking for 205/60-14. I am also told that on a bias ply tire, I don't use as much negative camber. What specs are you GTA [and GTV] guys running on your alignment with Hoosier Street TD's? Also, what PSI should I run or use as a basis? I've never run these tires before.

[jrclem]

The Wheel Source <http://www.wheel1.com/> is usually a little cheaper tan anyone else. Very good service, and the shipping comes out to less than the Sales Tax you would pay locally. The Hoosier web sight has a lot of info and recomendations on set up. Talk to me, I might have a little wisdom as well.**

[Tigaman]

You'll really be able to hang it out, Anthony!

1/2 degree negative, plus or minus a half degree. Normal to see slight spike in tread temps 2/3 of the way in on the tread face due to carcass distortion (nylon plys). Slight toe-out in the front (no more than .125" total)

Start at 22 psi all around. I used to use more, but all the fast guys (Bernardo Martinez, Jr., Peter Stark, Ceasar Cone) use this figure.

Let them go! It can be disconcerting at first, but just trust them.

They are done after eight or ten heat cycles, even though you may have tread...

Great news on Coronado! Keep your nose clean and you'll get to go to Monterey next!

[Alleggerita]

I haven't run Hoosiers but generally the GTA likes negative camber - I have run a variety of radials and Dunlop Racing. If you have a fairly standard front suspension, I would try to maximize negative camber and then proceed to maximize caster - offset caster bushings help with that. If you are running knuckle risers, bumpsteering the car will make it drive a lot better.

[Tigaman]

If you look at the recommendations from Hoosier for their bias-ply racing tires and from Dunlop for their L-section and M-section bias-ply tires, you will find that they desire much closer to vertical than either standard street radials or competition radials.

In our tire test conducted for Grassroots Motorsports magazine and reprinted in Classic Motorsport magazine, we had on hand tire engineers from Avon, Dunlop, Kumho, Goodyear and Hoosier. They were quite insistent that the radial on a competition car required a minimum of 2 1/2 degrees negative and preferably 3 1/2 degree negative.

While I agree with maximum caster recommendation for maximum mechanical grip, the manufacturer and personal experience recommendation is not to add too much negative camber for the application Anthony requires.

-Peter

[Alleggerita]

The old ARI Competition Manual gave -1.5 for the Dunlop Racing and -2.5 for the Goodyears, both of them bias plies. Indeed the Hoosier is more similar to the Goodyear than to the Dunlop.

If I remember correctly that was for a suspension set-up with knuckle risers which have a different camber gain curve than the stock suspension, that is you gain negative camber when you compress the spring whereas on the stocK set-up camber becomes more positve as the spring is compressed.

[genericwood]

Peter is right, -2.5 degrees is WAY too much negative camber for the Street TD's. On my car, I have arrived at -1.5 degrees as optimal. I started with -1 degree but tire temps suggested I needed a little more. I do run maximum castor and 1/8" toe out as Peter suggested. Also as Peter suggested, 22 pounds is a good place to start. But your ultimate goal is about 28 pounds hot. I have had to start as low as 19 pounds on various corners in hot weather to keep the pressures from going over 29-30 pounds. I really like the tires. As Peter said, let it hang out. They are very predictable and can be driven hard. By the way, I run 225/50-14 or 225/45-15. The 225 15's are slightly narrower than the 225 14's if you have clearance issues. The specs are on Hoosier's web site.

Erik

[alfa-sport]

"offset caster bushings"

Please explain better. Would the bolt hole be offset to one side - if so which?

alfa-sport

[Tigaman]

Yep, and the CRH recommends springs a third as heavy as we're using now...

[genericwood]

A couple more comments may be useful. The "offset castor bushings" would effectively lengthen the castor arm. This just allows you to run more castor without running out of threads on the adjustment. On my car they are not needed. The amount of castor I can run is limited by the chassis. If I run more than about 2 degrees the upper suspension arm will interfere with the chassis as it moves up and down.

As far as negative camber and knuckle risers, don't forget that most of us are running 2 liter type spindles. In essence, the factory "built in" the knuckle riser that had successfully used on the earlier shorter spindles. With the later type, a knuckle riser is not needed. At least on the later type, even the stock suspension goes to negative camber as the suspension is compressed. How much will depend to some degree on how much the car has been lowered with shorter springs.

Oh yeah, one last thing. As far as the original question regarding the amount of negative camber to run with the Hoosiers. Even though I think -1 1/2 degrees is right for my car, Peter says more like -1/2. Don't forget that he was significantly faster at the Glen than me!

Erik

[Tigaman]

Erik,

Surprised me, because I've never driven anything quicker than a Ferrari Testarossa at the Glen, and that was fifteen years ago. I enjoyed all of my eleven timed laps, though!

The starting recommendation I should have made for anyone for the Hoosiers should be about 1 degree negative, plus or minus a half a degree.

The reason I run less is because I'm running 1500 lb springs in the front (with a big front bar rear of the crossmember) and 375 lb springs in the back (with no bar). My roll angle is not very much, as you can imagine. As a contrast, the Sports 2000 Lola I run uses 180 lb fronts and 220 lb rears!?!?! It can go the equivalent of 2:02's at the Glen! All that on 140 bhp!

Most W&D set-ups (or those derived from them) seem to be 1100-1200 lb front, 225-275 lb rear and for that, you'de need more negative to keep up with the roll angle on the chassis.

Just goes to show, everything affects everything else!

-Peter

[ECARRILLO]

Quote:

Originally Posted by Tigaman If you look at the recommendations from Hoosier for their bias-ply racing tires and from Dunlop for their L-section and M-section bias-ply tires, you will find that they desire much closer to vertical than either standard street radials or competition radials. In our tire test conducted for Grassroots Motorsports magazine and reprinted in Classic Motorsport magazine, we had on hand tire engineers from Avon, Dunlop, Kumho, Goodyear and Hoosier. They were quite insistent that the radial on a competition car required a minimum of 2 1/2 degrees negative and preferably 3 1/2 degree negative. While I agree with maximum caster recommendation for maximum mechanical grip, the manufacturer and personal experience recommendation is not to add too much negative camber for the application Anthony requires. -Peter

[Tigaman]

Eliseo,

I'll get that information in the next couple days.

Two years ago, at the SVRA event at VIR, a track I know well , I conducted a very non-scientific test with the GTV I drove at the Glen. First, I used some older (six cycle +) Street TD's in 225/50-14 on 14 x 7's during the first session, then I ran some 225/50-14 Toyo RA-1's that were about 30% worn on 14 x 7's, then I ran the Avon 8.0/22.0-15 ACB-10's on 15 x 7's, all on the same day with a transponder (doesn't eliminate timing errors but is more consistent than the stop watch operated manually.) I have done one or two 2:19's but most of the time, from five years of running there, I average low to mid 2:20's, any time of year, every year.

I did the same time, within 4 tenths, with all three tires on the same day, albeit without adding the negative camber recommended by the Toyo...

Who knows?!?!

-Peter

[genericwood]

Eliseo, I haven't raced on the radials yet, so I don't know. My next tires will probably be Hoosier Street TD's again. I asked Roman Tucker about this choice at the Glen. His cars run TD's. He said they have considered doing some testing of the radials, but would not run them until they have some good data to support their use. You might ask Brian Stark for his opinion. I think he ran radials for the first time at the Glen. Just make sure you remind him that his kid is a lot faster than him so it might be hard to determine tire differences!

Erik

[italcarguy]

Hi guys, thanks for the input. Yesterday, I ordered a set of 205/60-14 Steet TD's. The cheapest I could find them for was $138 each....is that a good price for them? Everyone else I called was $10-$15 more.