New To Slack-Jr2 help?

1fasttiller

1fasttiller

Member
Hi Gents, Never been on a Slack or set one up in my life. A local kart shop here in Central Fl picked my son up as a factory driver this year and has him on a '18 X-Pect. We scaled it to the numbers Slack provides in the book and got the numbers spot on but it just seems to be lacking... I know tires are 99% of it and we feel we got a pretty good handle on them so I was just looking to see if any of you Slack Experts can offer some advice outside of the norm? My son is 54" tall and only weighs 60lbs. We have a TON of lead on this thing to hit the 290lb Jr2 weight. Unfortunately there aren't any slacks in this region that I've ever seen so comparing notes hasn't been easy....

Current set up:
57% Left
51.7% Rear
62% Cross

Total weight- 293lbs.

Seat is 10" off the axle.

Mostly on Vega yellows and Maxxis P&B.
 
1fasttiller said:
Hi Gents, Never been on a Slack or set one up in my life. A local kart shop here in Central Fl picked my son up as a factory driver this year and has him on a '18 X-Pect. We scaled it to the numbers Slack provides in the book and got the numbers spot on but it just seems to be lacking... I know tires are 99% of it and we feel we got a pretty good handle on them so I was just looking to see if any of you Slack Experts can offer some advice outside of the norm? My son is 54" tall and only weighs 60lbs. We have a TON of lead on this thing to hit the 290lb Jr2 weight. Unfortunately there aren't any slacks in this region that I've ever seen so comparing notes hasn't been easy....

Current set up:
57% Left
51.7% Rear
62% Cross

Total weight- 293lbs.

Seat is 10" off the axle.

Mostly on Vega yellows and Maxxis P&B.
Click to expand...
What are your cambers ? How far out is the RR & LR from inside edge of wheels to the frame ? what is your toe out ? How big is the track ?
Front Stagger & rear ?
 
My bad- Camber is at -2.75RF and +.5LF

I'd have to measure the wheels on the axle, don't have that off hand but it was set to Slack's recommendations.

Toe out is a strong 1/16"

Stagger has been 7/8" to 1" rear and 1-1/4 to 1-3/8 front depending on track. We're running tracks ranging from 1/8 mile to 1/4 mile.

We only have two races on this kart so not a ton of time on it yet, just was hoping to find some Slack "gurus" that maybe knew of some magic lol

This Saturday we're headed down to a very fast track outside Tampa (FDMS for those that may be familiar) its usually a very high bite Maxxis track. I have a fresh set of Pink and Blues ready to go, cut flat and punching around 55. Also have an older set punching almost 60.
 
I wouldn't call myself a "gurus" but have been tuning slacks for kids since 2010 with plenty of wins, You should not need 48 + on the nose, 47.5 max should get it, You should be able to increase left a little 57.5 % , But numbers are close of course gearing has to be right, 1" rear stagger is low for 1/8 mile, I know you say you think your tires are 99% there but I'd say the rest of your speed is tires especially the Maxxis game it has really changed, Example we took an xpect for Jr 3 last fall to Paradise that was spot on all year lots of wins, thought we had tires covered 90 % with a bunch of fresh rubber, was 7th off the pace all day, come to find out Fresh was not the ticket 4 month old Sr take offs re rolled was needed, got on a borrowed set for the final race picked up half second, I'd spend more time researching tires an prep choice than chassis with where your at.
Good Luck !!
 
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1597436235894.png
 
1fasttiller said:
My bad- Camber is at -2.75RF and +.5LF

I'd have to measure the wheels on the axle, don't have that off hand but it was set to Slack's recommendations.

Toe out is a strong 1/16"

Stagger has been 7/8" to 1" rear and 1-1/4 to 1-3/8 front depending on track. We're running tracks ranging from 1/8 mile to 1/4 mile.

We only have two races on this kart so not a ton of time on it yet, just was hoping to find some Slack "gurus" that maybe knew of some magic lol

This Saturday we're headed down to a very fast track outside Tampa (FDMS for those that may be familiar) its usually a very high bite Maxxis track. I have a fresh set of Pink and Blues ready to go, cut flat and punching around 55. Also have an older set punching almost 60.
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If its a big race you know you are behind the ball only having 2 sets. That is likely your down fall. If its a weekly show 2-3 sets will probably be fine.
 
Well, quick update for anyone thats still following!
Overall, had a killer day! Ran lap times with the fastest Jr2 kids in the state and almost won both the trophy race and the money!

Kart was wicked fast all day, had so much corner speed he had to learn how to drive!

Some bad luck and a hung throttle started us in the rear with 9 karts, worked all the way back to the front, led a few laps and ended up a solid 3rd. We were every bit as fast or faster than the leaders all day but due to some driver errors and dad being off a tooth on gear we salvaged a great day!
 
Did not touch the setup other than pulling a 7lb lead puck off the left side of the seat because we were quite heavy according to their scales.

I had some new Maxxis done up by Tim Krohn that were wicked. We had to soften them a bit at the track because of the rain that showed up earlier in the day left the track a little on the moist side. We went out on our Vega yellows in practice because it was so wet. Lap times at the end of the night were within 7/10's of track record.
 
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1fasttiller said:
Did not touch the setup other than pulling a 7lb lead puck off the left side of the seat because we were quite heavy according to their scales.

I had some new Maxxis done up by Tim Krohn that were wicked. We had to soften them a bit at the track because of the rain that showed up earlier in the day left the track a little on the moist side. We went out on our Vega yellows in practice because it was so wet. Lap times at the end of the night were within 7/10's of track record.
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I assume this was a different track than last run when you posted this thread ? Or did the rain just make for different track conditions ?
 
Same track but a ton of southern Florida rain really changed things!

My post above was a little misleading.... I only practiced on the Vegas lol were were on the Maxxis the rest of the evening.
 
1fasttiller said:
Same track but a ton of southern Florida rain really changed things!

My post above was a little misleading.... I only practiced on the Vegas lol were were on the Maxxis the rest of the evening.
Click to expand...
Bottom line NOTE the differences which made you better, From here in PA looks to me like your tires were better suited for the condition, and most likely your current set up more suited for the more moist condition, when you race there again IF conditions are back to more like last run there I'd say you can can drop some nose and get that Left side weight back up to where it was or even a little more, still Tires are most important compare where you were last run and this run keeping in mind different track conditions and again from here in PA looks to me like you were bite up ( maybe ) little to much last run, and to low on air ( maybe ) but take a real good look at the difference in tires VS track condition.
Good Luck !!
 
racing promotor said:
Bottom line NOTE the differences which made you better, From here in PA looks to me like your tires were better suited for the condition, and most likely your current set up more suited for the more moist condition, when you race there again IF conditions are back to more like last run there I'd say you can can drop some nose and get that Left side weight back up to where it was or even a little more, still Tires are most important compare where you were last run and this run keeping in mind different track conditions and again from here in PA looks to me like you were bite up ( maybe ) little to much last run, and to low on air ( maybe ) but take a real good look at the difference in tires VS track condition.
Good Luck !!
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Absolutely! And thank you so much again for all your responses and help! We're definitely making some headway!
 
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