Takes too long to come "up to speed"

[two_tenths_off]

This weekend I had an opportunity to watch our car take about 50 consecutive practice laps with a live timing system.

Our fast laps came at about lap 40. These fast laps were about 1/10 to 15/100's faster than the laps around lap 20. For example we were turning 5.66 around lap 20 and down to a fast lap of around 5.5 at lap 40.

Obviously this is effecting our Qualifying performance. How do we make the car come in faster?

What is causing this? Is the heat and pressure buildup in the tires altering the spring rates once the tires get good and warm? Can this process be accelerated with pressure or spring rate changes?

Any ideas?

[ssssmoke]

you will get about a hundred different opinions on this. what kind of car? tires? track and outside temp?  i would say softer tires or tighten the car up a scoach.

[sfreitas20]

Good questions from ssssmoke...also were the tires brand new before this run or were they already scuffed in?

[BuckeyeQMDad]

Is it a young driver? It sometimes takes them longer to really get themselves going in a groove. Mine was especially bad about that when he was younger and still isn't great w/ it even after 3yrs of racing. I can see a noticable difference in his driving from the beginning to the end of practice- Even in the middle of the summer when he's in the car and average of 2-4 days a week.

[Swartz]

Bassed on the limited information I'm going to make two assumtions. 1. you are not using nitrogen in your tires and 2. Your hubs and birdcages are not clearanced for the bearings. The only thing you are adding with additional laps is heat in the rotating components that tends to make the bearing housings expand, freeing them up, and building pressure in the tires. Check the air pressures with the tires at operating temperature and I'll bet it's 2 to 4 pounds higher than where you started. How do the times compare to other cars in the same class?

[two_tenths_off]

Swartz - thems are some mighty fine assumptions on your part!

1) I am using air - and not the dryest air either.
2) I am guilty of purchasing the car used and running it two years without touching the rear axle bearings.

Yes the right side pressure is 2-4 lbs higher when we come in, for example up from 12 lbs to 15-16lbs.

Other cars were turning 5.3, 5.4, 5.5's in Qualifying and we typically only see 5.4x in the race, our best qualifying might have been 5.56 or so this year.

[Swartz]

Well, there ya go. Use the air pressures that are fastest for qualifying and back them down to give room to build for the race. Get in the habbit of removing, cleaning and relubing ALL the bearings every race if you can. Fast is a lot of hard work.