CMRA F4 Sprint Round 7 at Texas World Speedway

[zvonler]

Here's onboard from my sprint race this past weekend. I'd never raced on this track, and it's a little unique because the start happens on pit row instead of on the track itself. I hadn't practiced going into Turn 1 at full blast from pit row, so I lost a few places and was in 8th coming out of T2. It took me about half a lap to shake that off (felt like I was at the back of the pack!) but then I found my groove and ran some good laps. There's a decent battle in the 4th lap with #770 that almost puts me in the grass.

Link to original page on YouTube.

[gt_turbo]

great riding! how is that you can blow by the other 250's so easily on the home straight?

[cuong-nutz]

Congrats!

[zvonler]

Originally Posted by gt_turbo

great riding! how is that you can blow by the other 250's so easily on the home straight?

Some of those bikes are tuned differently; this is the F4 class, which allows 250s with some minor engine mods (degreed cams being the most significant). Some of these bikes are tuned for E Superstock and are racing up a class, which means they aren't allowed to touch the inside of the motor at all. That plus taller gearing on my bike allowed me to hit higher speeds on the straight.

Drafting is also important, the pass I make for 2nd at the start of the sixth lap is made much easier by being able to draft about half the length of the straight.

[MKlein3004]

Hey zach,

I was out there, got 15th place in Formula 4. I went down in practice so I was a little hesitant to go full bore, plus my front end was pushing really bad. What tires are you runnning? BT003F up front? How many hours do you put on that tire? Or if your running a different tire, what is your setup.

Obviously your rider skill is greater than mine, just trying to get a baseline, considering this was my first sprint weekend.

I have a couple questions for ya:

What chain and sprocket setup do you use? 415? 520?

What sprocket sizes do you use for each CMRA track. I got an answer from someone early this year on the gearing for the 1.3 and it was different than the original information I received. I am just trying to get things set up, parts wise.

If you could help me out with these things, I will hopefully see you towards the front soon. Thanks

[zvonler]

Originally Posted by MKlein3004

What tires are you runnning? BT003F up front? How many hours do you put on that tire?

What chain and sprocket setup do you use? 415? 520?

What sprocket sizes do you use for each CMRA track. I got an answer from someone early this year on the gearing for the 1.3 and it was different than the original information I received. I am just trying to get things set up, parts wise.

Using Bridgestone R10 front and BT003RS rear, I get them from John Hutchinson at South Central Race Center. I've been getting around 15-20 hours from each tire at race pace.

The gearing is from Sprocket Specialists. I'm using a 428 pitch, non-O-ring chain. At Cresson I used 17/59 gearing and at TWS I was running 18/55. I think a 56 rear might have been slightly better at TWS, since I never managed to hit the rev limiter all weekend. I use gearingcommander.com to see what different gearing does to the top speed, it's really helpful.