Jr. National Chassis Selection

[Chris Lobaugh]

The first round of Stars East was held in Ocala, FL the weekend of March 14 and 15. We had 4 Jr. drivers under the MRP/Birel America tent this weekend with 3 different 30mm chassis and all posted strong results despite some rather unfortunate racing incidents.

Danny Formal raced his RY30S1 with a very standard set up; 1040 F axle up, no middle bearing, 85mm rear hubs at 54", no side rail, one set of seat stays each side, seat at 59 and 60cm, 21cm from the top of the axle to the top of the back of the seat. 25mm spindles at standard height, .5 degree caster in, 0 camber, 2mm toe out. 75mm front hubs set at one thick and one thin spacer wide. Danny was within a couple of tenths right out of the box and was always in the top 5. He got shuffled back to start the final and managed to drive back to 4th position.

Louie Pagano raced an RX30SE with the help of Dave Thompson of Dave's Performance Karting. Louie was extremely fast right out the box and they had to change very little through the course of the weekend. I am fairly certain that they raced a 1040 F axle up, middle bearing in, 100mm Aluminum hubs, spindles down, short front bar, 75mm front hubs. I am not sure on the seat position or the front end settings but if Dave wants to add anything please feel free. As I said Louie set the pace out of the box and had it not been for a certain driver putting him off twice in the final he would have finished in the top 3 for sure.

Sage Karam and Jake Cole both raced R30CY's. It was the first time with the Leopard engine package for both drivers, Jakes 2nd race of the season and Sages first race since October. Jake struggled with engine and carburetor issues but made progress over the course of the weekend. Sage qualified 13th, ended 6th, 7th, and 8th in his heats which put him 6th on the grid for the pre-final. He was punted in the first corner of the pre and went back to last...he drove back to 13th. In the final he made it two corners before got punted and again went back to last...he drove back to 7th.

Sage raced a 1000 M axle, middle bearing loose, 85mm hubs at 54" wide, one seat stay each side, Tillet SCD seat at 60, 60.5 and 22 with the bottom of the seat flush with the bottom of the frame rails. We had 10 lbs on the front of the seat, 10 lbs on the left side of the seat, 5 lbs on the right, and 25 lbs on the back of the seat. Spindles in the middle, standard front bar, 75mm hubs on 17mm spindles two thick and one thin spacer wide, 2mm toe out and 12mm negative camber.

[Lance Z]

Is the 12mm negative camber correct? What was the reasoning behind Sage and Jake running the R30C-Y, as opposed to the other chassis available? What was the minimum weight for the class they were running in? If I am running a the same chassis in the Yamaha SSX can class at 305lbs, on YDS tires, M axle, any suggestions for setups?

[Marc Miller]

Lance,

The 12mm was supposed to be 2mm of negative camber. Apologies, Chris has fat fingers.

Also - I am assuming both drivers were on the R30CY because they are easy to tune out of the box and we had several of them available. With both drivers being small and light, the all 30mm chassis was a good choice and being their first time out, the main focus was seat time and experience rather than time tuning the chassis. Simply - the R30CY chassis is well-known and we have a lot of data on it to make it go well.

As far as set-ups... take a look at the new "BASELINES" section and post additional questions there.

[Chris Lobaugh]

12mm negative camber is correct. This is not a base line by any means, but, this is where we ended up at Ocala...thanks Marc but my fingers are actually quite slim.

[Chris Lobaugh]

Sorry...I neglected to answer the rest of your questions. The minimum weight was 330 lbs. What was the reasoning behind running the R30CY? We had a hunch that the chassis would work well at Ocala and as Marc said Jake and Sage are small drivers and the R30CY is a chassis that works well in low grip situations. Pagano uses the RX30SE in California so that was an easy choice for him to make. Formal has been on the RY30S1 since he switched back to Birel...again it was a no-brainer as to which chassis he would race.

We ended up with 12mm negative camber because we were looking to decrease front grip from the center of the corner to the exit of the corner. Ocala has a number of long sweeping corners where we were lacking rear grip. Sage was also having a problem with the rear of the kart breaking loose in the fast corners as soon as he touched the steering wheel. We tested with a bit of caster out but then he experienced an entry push in the slow corners so we started testing negative camber. First we went from positive 2mm to negative 2mm, then we went to negative 6mm, then we went all the way to negative 12mm for the practice session Sunday morning and it was the best the kart had been.

In regards to suggestions for YDS tires: Are you using a 40mm or 50mm axle? If it is a 50mm the M axle might be a bit too stiff for such a hard tire. I would test with the middle bearing tight vs. loose and if it is better with the middle bearing loose I would try a softer axle. If it is a 40mm axle then I would still test the middle bearing but you are probably on the correct stiffness axle. If you are experiencing a loose condition from the center of the corner off I would test some negative camber keeping in mind that a 2mm change will make a considerable difference. I would also test .5 degree of caster out vs. in and possible moving the spindles up. Hope this helps...

[Dan Schlosser]

How did you get to 12 degrees negative camber Chris? An interesting concept to try, just not sure how to accomplish it with our standard 1 degree pills top and bottom.

Flipping the spindles over and swapping sides??

[Andy Seesemann]

12mm negative Dan, not 12 deg.

It can be done.

A

[Marc Miller]

12mm negative camber is correct. This is not a base line by any means, but, this is where we ended up at Ocala...thanks Marc but my fingers are actually quite slim.

haha... sorry Chris. I should have called to double check.

[Dan Schlosser]

12mm negative Dan, not 12 deg.

It can be done.

A

<sigh> Reading comprehension must go somewhere between eyesight and memo....

What were we talking about?

Thanks Andy.

[Lance Z]

Thanks everyone for your helpful responses. I am running the 40mm rear axle, with the middle bearing zip tied. Alex seems to like a high corner entry speed, but on some of the medium speed tight 180 degree turns, the cart doesnt want to turn in, then goes loose at the rear from the middle of the corner to the exit. I will try the 2mm neg. camber also. We are currently running the rear width at 50", should we go a little wider? Would trying the front bar in be advisable? All in all, we really like the kart (R30C-Y) and his times have improved, even though we have only had one test day so far, but it responds well to changes, and is easy to tune. I hear the boys and girls from Wisconsin are going to be running down there this Friday, wish we could have come down......Thanks for all your help.

[Chris Lobaugh]

50" with 6.0" tires is a bit narrow. The first thing I would test is increasing the rear track width 1/4" per side at a time. If this helps but the driver is still lacking front grip I would definitely install the front torsion bar. If adding the front bar makes the rear of the kart slide on high speed corners I would test with the middle bearing tight or with the lower crash bar (on the rear bumper) tight.

[sage karam]

The middle bearing change worked well yesterday. Thank you MRP for the lesson. Sage learned a lot yesterday. We look forward to putting more time in the kart this year and getting back up to speed.

Thanks,
Jody

[Lance Z]

Tested with front bar in, and the turn in was better. I will try the bearing suggestions the next time out. I forgot to say that we are running the 4.5 inch tires all the way around. Tried the rear at 51" wide, made the rear looser, so returned to 50" which was better. The M axle seems to work better than the F, at least at the 47 degree temps we had on Friday. Anybody tested the Ilmor mount yet, we have one and it is a very slick piece, just wonder if anyone else has tried one yet. Also, what type of pedal extenders work well with the Freeline pedals, just need about 1/2 and inch closer or so. Thanks again.