AR28Z high grip adjustments

[Tony Durbin]

Hi,

We bought a new AR28Z chassis earlier in the season to run Yamaha Junior Sportsman. This is our first season. (my son just turned 9)

During the year, we have used longer hubs in the morning, went to the shorter ones in the afternoon, softest 30mm axle, 2mm toe out (on the stand), and 2 front spacers (the kart came with neutral pills). We had found the hubs always worked best from 1/2 to 1" from the end of the axle. Seat is in the recommended position.

This weekend, we struggled as we saw high temps and by far the most track grip we saw all season. The kart tightened badly as the day went on.

Is it normal in high grip situations to run the hubs all the way to the end of the axle without changing the front end? Or in these situations, should I look at getting camber/castor adjustments? We're going to have a full day of practice later this week, so I'll obviously try some things out. Just looking for some suggestions on starting points, or what you've found that normally works.

Thanks,
Tony

[Marc Miller]

Hi Tony-

We field these questions regularly. Hopefully you won't mind the delay in the answer, but first I must ask a few questions.

What track are you running at?
What tires are you running?
What starting pressures?

I assume you are using the short Freeline mag hubs?

30mm axle? What length and modulus?

What was going on at the track to increase the level of grip? regional event?

I assume prior to this - the balance of the kart was good and you weren't experiencing any of these issues prior to this?


I am certain we can help - but just so you aren't sent down the wrong direction - it is better to have all the information possible.

[Tony Durbin]

Marc,

Thanks for the quick reply. Here are answers to your questions.

Track: New Castle, Indiana
Tires: Bridgestone YHC
Pressures: Started with 14 (cold) in morning practice, went to 12 (cold) for qual. and 2 features. Douglass rims.

Yes, short hubs, 30mm 1040 B axle.

Over 30 TAG karts in 150 lap Ironman race the prior weekend, then Route 66 practice day Friday and racing Saturday. We raced Sunday.

Yes, the balance of the kart looked good prior to this. I could always loosen it up before.

Thanks,
Tony

[Marc Miller]

Thanks Tony-

The engineering staff is on their way to Shawano for the Stars race, let me discuss it with them and I'll try to get you some thoughts soon.

[jody emmons]

this is going to sound way out there for new castle, but if you doubt this talk with mark harrison at the track. start at 16 to 18 psi in front and rears about the same. there are some real long straightaways there. you will then have less rolling resistance and grip should drop a little with these air pressure. i know this sounds very odd, but i have run there and did those air pressures, picked up at least 1 sec.

[Chris Lobaugh]

Tony,
To answer your original question...yes we have run the rear hubs all the way out on the end of the axle and have even hung the hub off the end of the axle by 5mm and not touched the front of the chassis. It certainly would be worth a try, but, it is possible (especially in the heat of the summer) to make the rear of the kart too soft and as the day goes on you just get slower and slower. Are you running with the front torsion bar in? What is the front track width? Do you have any eccentric bushings that you can test with?

[Chris Lobaugh]

Tony,
One other thing that I forgot to ask...Have you tried moving the axle up yet?