What are some good recommendations/observations for tires and alignment to help me set up for track racing?
The following is commentary on track setup, compiled and edited from personal E-mails by 2 of the VCA's successful Solo1 Viper Days Challenge Series participants in the Stock and Prepared classes.
Thoughts on Tires and Alignment ,by W W Racing (Woodhouse and Word) [ R1s, XGT-Zs, MXX3s, Hoosires, and G-Force ]
Tires and Pressures:
Woodhouse (who ran Hoosiers at Savannah) - We were starting at 29psi and looking for a working pressure of 34 to 36. It was cool so we started a little higher and as you would expect, the left front picked up the most pressure. We began the weekend on the last half of a set of R-1s in stock sizes. I think they are a great tire, but I was still two seconds off your pace by the end of their useful life. It was Sat. noon when the dreaded flat spot occurred. We went to the slicks temporarily while Bobby Archer mounted up some Hoosiers (315 all around) for us. I had no intention of doing this except there were no alternatives, but it turned out to be a very driveable combination - especially for your style of driving Deano. They took the two seconds back that we were missing to get competitive with you. Actually give the tires credit for half and the other for the smoothness training I recieved driving in the rain on slicks Saturday afternoon.
Word - I run R1s starting at about 26-27 psi. I end up with hot pressures around 41-42f, 36-37r. With no brake ducting, I get quite a bit of heat transfer off the front discs which pushes the front pressures up. I've run both 275s and 315s up front. The narrow tires like minimal steering input and constant loading (Bob's style - thank you) while the fat ones seem to work better with lots of steering angle at turn-in and throttle steer on exit (my style.)
With MXX3 Pilots, I start with higher pressures, but end up about the same. They go really greasy with more than 135F temps, but you sound and look like a real hero with squalling tires in 4-wheel drifts. They give loads of notice at the edge - very forgiving and fun (albeit expensive) to hammer. They work nicely for autocross because the tread compound is formulated for good performance at relatively cool temperatures.
XGT-Zs are very darty and unforgiving at the limit, but that limit is noticeably higher than the MXX3s in shirtsleeve weather and they don't get greasy. They seem to thrive and survive at temps up to 170-180F - (about where I find my R1s most of the time.) Again, I seem to like the hot pressures in the low 40's f, around 36 rear. The XGTs are very prone to snap-oversteer on slow corner exit. Dropping the pressure a smidgen helps soften the bite, but ya gotta be easy on the sidewalls. (I think shock valving would do wonders to tame this type of behavior.)
Now for my latest discovery - the g-Force R1- which I ran at Savannah: 7 ply tread construction (3 steel!) and 3 ply sidewalls - so you know it's gonna be stiff! They remind me a lot of the XGTs, now that I've had time to reflect. Very hard to keep on the limit, and somewhat difficult to get there. I've tried 'em soft (lousy) and I've tried 'em hard - better. I guess I'm just too comfortable with the old R1s' more compliant outer shoulder. The g-Fs are MUCH MORE camber-sensitive. I'm still learning how to drive them and can't offer any good advise on optimum pressures. BFG says the temps should be close to the older R1's (about 170-200F). Team T/A also stongly recommends heat-cycling them properly.
I can't say much about slicks except that I like 'em A LOT! In 4 years of Viper road course work, I have logged exactly 4 laps on slicks. They were FUN laps though - 9 full seconds faster than the very old XGTs I had just taken off, and 2 secs faster than R1s! However, I would discourage their use by novices because they hide so many driver mistakes. Master the street rubber first!
Alignments:
Woodhouse - "Won't take long, so here goes in short form" Front caster: [lots] is pretty good but if messing around we think 6 degrees is good. If you like a lot of neg. camber, then this number can be less. Front toe: not critical, 0 to slight toe-out up to 1/8 inch. Front Camber: I like neg. camber. When the tire will wear equal at the end of it's useful life then that is the right amount (not a rule just an indicator). Camber setting will vary based on the brand and type of tire. The various tire carcasses are engineered differently. R1 has 3/4 degree built in. Others I am unsure. 1.5 to 2.0 neg camber is what we think works up front on these tires. Some slicks will need more. I do not use different camber settings from side to side, the driver has enuf to think about. When you set up with lots of negative camber the driver could tend toward more flat-spotting and it does hurt the braking G slightly. Caress the pedal is my thought, not the right one perhaps. Brakes slow you down anyway. This next comment will start an argument::::::::::: the rear camber should be more than the front. Now I am not absolutely sure of this but if my tires are not lying to me they want 0.5 degree more negative than the front. That will put you in the -2 to -2.5 area. I've found this to be more critical on the softer sidewall tires. With stock rubber, camber back there is OK at -1 degree or more. When dialing in your first set-up, think about the tires. If you run slicks with a lot of sidewall they will tend to move over more on high g turns and may require more camber than a short stiff-sidewalled narrower tire. Anticipate bushing defection on stock suspensions too. Some of the diagnostics methods I use are: how is the tire wearing edge to edge, the look and texture of how the rubber is tearing as it gets scuffed away, where the "bubble gum" piles up on the tire when it gets greasy, and what the pyrometer is telling you. (see Carrol Smith's books) Rear toe in: My opinion is we can be aggressive here. It allows you to keep the throttle in and drive out of a mistake. It also keeps the back end behind you when braking hard. A good starting place is 3/8".
OK Word, half these guys are gonna think I dropped off the turnip truck but there is too much subject to cover here.
Word - I'm gonna defer to Bob's expertise on this one, but I do have some opinions based on my limited experience. Toe settings: I pretty much ditto Bob's sentiments. Caster: Should stay reasonably close to factory spec. and within 0.2 degrees side-to-side unless you are oval tracking, which is something I really don't relate to. (if you let go of the wheel and it steers for the ditch, something's seriously wrong IMO ) Camber setting: Is governed by the following variables: tire construction, how long you are in the corners relative to the straights, and how many g's you are able to generate in the corners. Insufficient negative camber will cause rapid wear and excessive heating of the outer shoulder of the tire. Too much negative decreases tire footprint available for straight-line acceleration and braking. The "ideal" setting for the whole track is, by necessity, a tradeoff. Where is more time lost or made - corners, or straights? Read the tire. Each one has a story to tell. When you have it right, all 4 tires tell the same story. Bump steer: The Viper is one of the few cars that allow you to adjust this. I've known a Winston Cup crew chief since high school and he swears by controlling bump steer on road courses. I haven't ever checked or fiddled with it on my car- mainly because it adds another 2+ hours on the alignment rack at $50 an hour.
Reflections on Savannah Finals:
Woodhouse - At Roebling, with all the large radius turns it would appear mid-corner speed is the ticket, had we had time to mess around I would have pumped in more camber. The outside rear tire edges were getting worked hard, the pressures in the tires were running about right but we were piling stacks of rubber on the inner third. At the rear, we were off by 0.5 degree at least. On Friday nite I did not think I would find the 3 and a half seconds that separated us. Saturday I found only one. Then it rained, that really made the difference, no traffic we went out there and just went around on slicks for about an hour. Found the decel accel points and polished a few confusing spots. Turn one I think is where I finally realized the second straight away began at the end of the long straight away's braking point, or over in the farthest away point on the track. [past the "0" marker]
Word - As for different camber settings side to side, (based on my experience there last year with a stock alignment) I experimented with it for the first time at Savannah. 5 of the 8 corners were right-handers. The most important ones (8, 2 and 7) led onto 4th and 5th gear straights. So, I felt the cornering loads needed to be better accommodated with more negative camber on the left side. Turn 3 (a left bend) was very fast but it didn't take long to get through and therefore wouldn't heat the outside rights too much. 5 was too slow and slippery with concrete patches and asphalt crack seal to get any useable camber thrust, so I felt less camber wouldn't hurt. I, like Bob, also went too conservative on camber - both sides and both ends - by a much greater margin. As for piling "chewing gum" on the inner third, this can be misleading. If your camber settings are fairly aggressive, this portion of the tire carries more of the loading on the straights and coming slow into the paddock. I would guess that about half the junk is due to tread roll-off, while the other half is pick-up from other tires and driving off-line.
Final thoughts -
We recommend the use of pyrometers and tire pressure gauges. Always use the same pressure gauge. Consistency is the key. Keep notes at the track and think about cause-effect relationships on handling from the small changes you make. Don't change more than one thing at a time.
We don't have all the answers, but maybe some of this can help you. We encourage your input and questions. We'll answer until until you are beating us, then it's your turn to author one of these.
For The Sport, (GTS)
Dean Word/Bob Woodhouse