Concrete vs. Asphalt

[ChrisInAtlanta]

Well, now that Nationals is to be held on a concrete surface again, we need to start thinking about driving on concrete again. Some members are lucky enough to be able to run a lot of events on concrete surfaces, others find it quite difficult to do so. I have a concrete autocross pad available once a month, but it is ultra high grip (I once corded a set of DOT Hoosiers in EIGHT runs in my Bimmer). A five hour drive. With grass growing in the joints. And I can do the Peru tour in July, an 11 hour drive.

The issue, I believe, is being able to shift mental gears and realize that you have more grip. Some folks do this easily, others - like me - find it a difficult switch. I get the impression that Lincoln is not ultra high grip, but still. . .

And car setup is different. Given more stick, shocks need to be stiffer. My data acquisition points me towards setting my primitive suspension based on surface roughness/bumpiness. Tire pressures need to be higher. I would assume that roll bar balance changes. In all, the biggest changes I make on my F500 are based on surface smoothness, not stick, though I do up my tire pressures.

What changes do you make when you are going to be running on concrete, and why?

Chris Eckles
Atlanta

[Jim Garry]

You're correct in noting "I get the impression that Lincoln is not ultra high grip, but still. . . ". I don't think we'll be experiencing the grip of Salina or Forbes. But I could easily be wrong on that since it's just a guess based on reports from the test event held in October. But the airport authority there reportedly has some serious pavement "grooming" equipment which should help improve grip over the levels experienced in October. There will be a Pro Solo there in May and we'll all be interested in hearing the reports of those competitors.

As for setup changes, I haven't had access to concrete sites since before I got my car handling well (with a big thank you to Gary Godula for help with shock valving). But I do go from the relatively high grip Devens site to the lower grip Seneca site (not to mention the dearly departed HPT pad). The primary changes I make between those sites is to sway bars with some minor shock adjustments (but no revalve). Certainly a very high grip site might require shock valving changes but for 2009 at Lincoln I'll be running what I've got. There's no chance for me to make the long haul out there prior to September so I hope to qualify for the Pro Finale and will enter the Warm Up event too in order to check out grip levels prior to the Nationals later that week.

Jim

[Viperklr]

I typically run at Seneca which is a medium grip asphalt site with a section of pretty high grip concrete. Not wanting to upset the apple cart too much going in, I used my same Seneca set up when I went to Topeka and it did not work at all. I think the car was way too stiff there and mechanical grip was poor. While my bars adjust easily enough, my shocks need to come off to adjust. I think that the Seneca set up may be closer for Lincoln than for HPT.

I may end up going to the "East Coast" championship in Arkansas (I gotta laugh every time I see that) and that may help me get some indication of where I need to be for Lincoln.

[raisin racin']

If you'd like to experience some high grip concrete, look at events scheduled for the Grissom (Peru) Indiana Air Guard base. Several Great Lakes regions hold events there, and there is typically a Tour event there. Large site, with room for high (relatively) speed and technical course.