Birel DD2

[Marc Miller]

Baseline set-up for Birel Rotax DD2:

Axle: 1040x40x3-F
Hubs: 100mm hubs, rear track set at 54 ½”
Seat Struts: one seat stay each side (but we normally run without the seat stay on the right side)
Side Rail: Start with side rail in and test w/o
Front Bar: short front bar
Front End: spindles down, .5 degree caster (I would say .5 degree positive camber would be the next step for more front grip)
Front width: front hubs set at two thick spacers wide.

The inherent problem with the DD2 is the use of a 40mm axle. The axle is so soft that the kart will release the inside tire momentarily then set it back down and create a push from the center of the corner off. We tested different combinations of standard axle with the side rail in and hard axle with the side rail out. One thing that I wanted to try and ran out of time was hard axle, short rear hubs, side rail out, move the seat forward…

Seat Position: Standard

*Thank you to MRP-Birel Engineer, Chris Lobaugh, for this information.

[Brian Leadingham]

Marc,

Can you post the baseline setup for a Birel DD2?

Thanks,
Brian

[Marc Miller]

posted above - thanks for your patience.

[Brian Leadingham]

Thanks Marc and Chris! I noticed that the MRP DD2 kart had an M axle. Given what you've provided here it wouldn't seem like I would want a softer axle. What should I experience with a softer axle?

[Marc Miller]

An "M" axle is a harder axle. Chris points out that the harder axle might give the kart a "set" for longer so it wouldn't be so quick to create a push mid-corner to exit.

Typically, the DD2 kart would have lack of rear grip on exit. The "M" axle might also remedy that as well.

[Brian Leadingham]

Thanks again! You guys are awesome with the support to the racing community.

[Garry Lobaugh]

Brian, thanks for your feed back and compliments. You are a valued asset at the track. For 2010, what do you think we can do to attract more DD2 racers?

[william keyes]

There is no real feeder program in Rotax for the DD2 class. That is where it has to start, with the kids. Right now if a kid has an interest in shifting he will likely end up in a different organization and will likely climb the ladder of shifter classes. You loose this kid. These other organizations realize this and have recently doubled down their efforts with the addition of a Junior Stock Moto class.

I think you need a Junior DD2 class to successfully fill the DD2 class in the future. Just a guess but 1 of 100 Jr. Rotax kids may choose DD2 instead of Senior Rotax. That will never fill.

Garry, Tim, Chris, is it mechanically possible to do this? Say, a junior cylinder or pipe/carb restriction, limited internal gear choices etc.

I see two results...initially you may see an increase in entries as some will choose to run Jr. Rotax and Jr. DD2 and ...ultimately you will feed your DD2 Senior class.

What do you think?

[Garry Lobaugh]

Great innovation Bill.

I'll share with Austria. Thanks for taking time out to share this idea.