Tire pressure/setup questions

ZFracing

ZFracing

Member
Hello all,

So i was able to get some practice in yesterday at a track at my buddy's house, dirt with banking. I finished scaling out the car yesterday, 58.4% cross, 57.7% left, 55.5% nose, Im running 1/4 spacers on both inside front hubs, and 1/4" rear spacing on the rear. Total weight of the car is 375, I needed to be 370 for the class. And the tire pressures I went with where 8 on the left and 10 on the right. The car felt great overall, the only issue I had was on entry. I think one of my main issues was I was locking up the rear before entering the corner, I believe I need to move the brake rod down closer to the piston to fix that issue? The drive off felt good, but since I was sliding going in it made my exits not to favorable sometimes.

What would be your 2 cents on what I should do moving forward?
my initial thoughts are to move the brake rod so I'm not locking the rear, and add cross to the kart. I wont know really if my tire pressures are correct till the first race on the 13-14th of this month.
 
If indeed you had 55.5% nose YA it was loose in, but I think you meant 55.5 % rear maybe ? your air pressures were most likely to high and you didn't need a 2 lb split.
 
racing promotor said:
If indeed you had 55.5% nose YA it was loose in, but I think you meant 55.5 % rear maybe ? your air pressures were most likely to high and you didn't need a 2 lb split.
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sorry meant 45.5 nose, i basically went off ultramaxes setup sheet they provide on their site for a good base. I leaned toward the hvy/super hvy column. Also im running burris dirt treaded tires.
 

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Yea on them treads i would be more like 3-4 , 4-5 maybe even try 5-5 or 4-4 .
I've always ran a split . So i would be trying that now .
What happens when you don't mash the brake ?
 
flattop1 said:
Yea on them treads i would be more like 3-4 , 4-5 maybe even try 5-5 or 4-4 .
I've always ran a split . So i would be trying that now .
What happens when you don't mash the brake ?
Click to expand...
the kart turns great, feels great on entry and exit, the track was pretty wet. When i let it coast more into the corner I felt good, I did have some wheel spin coming off though.
 
Consider moving the seat back to get some more rear percentage if you are spinning the tires under throttle. Bigger HP applications on treads like more rear % than stockers. Lower air will help some as well.


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flattop1 said:
You on big power ?
Yes : moving the rod down would slow the brake effect a little .
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Predator 212 class, its built a little but not to much our rules are strict. Here is how the kart currently sits @CarlsonMotorsports, seat it as back and low as I can get it.
 

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racing promotor said:
You don't want less nose with that motor package, how low is as low as you can get it
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from top of seat to top of rear axel im at 9.25", i had to add around 55 lbs to the kart to make 370 lbs. I added 10lbs to the nose to get nose weight.

edit: im almost resting on top of the brake shield
 
flattop1 said:
That lft rear looks pretty big . A 600 might be better there .
Click to expand...
ill look into that as well, was hoping to see how it went the first race. most guys i race with are running qrc frames. im one of the few with a offset frame like an ultramax, or prc ect. I was thinking I needed to add more cross weight in it, in legends I always run a little bit of a push.
 
Lower air
Change your driving line so as not to stab the brakes .
Highly doubt changing will help but its a simple task to lower the rod .
maybe adjust the rod longer also . So the toe is on the pedal , insted of the middle of the foot .
 
flattop1 said:
Lower air
Change your driving line so as not to stab the brakes .
Highly doubt changing will help but its a simple task to lower the rod .
maybe adjust the rod longer also . So the toe is on the pedal , insted of the middle of the foot .
Click to expand...
Will do! Yea first race in a kart is in two weeks, should be fun!
 
I'm surprised that a fairly stock predator is able to spin the tires. Your track must be very poor condition for that to be possible.
Generally that only happens with bigger HP opens, etc. then we go up on rear % (down on nose %.) With a Predator you should not have to do that. Seat position sounds fine.
You should never have to "stab" the brakes to set the kart in the corner. With being so underpowered, you are killing all of your momentum and likely disengaging your clutch. Try arcing the corners more and keep your momentum up. If you are needing to stab the brakes to get the car to turn in, then it doesn't have enough rear stagger in it. There's also a chance that you have mixed up your RF tire from your LR tire. Generally (although not widely accepted amongst the QRC guys (YET)) you run two wide tires on the right sides and two narrow tires on the left sides (same as with a standard flat kart.) If you're trying to run a 7.00 LR, it'll push like a dump truck with any cross or weight on it at all. Also check to see that your staggers are correct. If you have little to no stagger, chances are that you mixed up the RF for the LR.
 
CarlsonMotorsports said:
I'm surprised that a fairly stock predator is able to spin the tires. Your track must be very poor condition for that to be possible.
Generally that only happens with bigger HP opens, etc. then we go up on rear % (down on nose %.) With a Predator you should not have to do that. Seat position sounds fine.
You should never have to "stab" the brakes to set the kart in the corner. With being so underpowered, you are killing all of your momentum and likely disengaging your clutch. Try arcing the corners more and keep your momentum up. If you are needing to stab the brakes to get the car to turn in, then it doesn't have enough rear stagger in it. There's also a chance that you have mixed up your RF tire from your LR tire. Generally (although not widely accepted amongst the QRC guys (YET)) you run two wide tires on the right sides and two narrow tires on the left sides (same as with a standard flat kart.) If you're trying to run a 7.00 LR, it'll push like a dump truck with any cross or weight on it at all. Also check to see that your staggers are correct. If you have little to no stagger, chances are that you mixed up the RF for the LR.
Click to expand...
The track I was running on was in poor condition since it rained here the day before, it wasnt prepped ect. I wouldnt say I had to hit the brakes to get the kart to turn, it was more when i hit the brakes to slow down for the corner I was sliding, but that could of been the track. I will check stagger tonight and look into moving the wider LR to the RF. Thank you for your help!
 
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