Roll Speed

MAS

Member
I’m looking for a little bit of information... we are running a small flat bullring style track. I’m running a 11/70 gear, hitting 7000 rpm at the end of the straightaway. I’m rolling the scales at around 470. I’m currently running 2 inches of stagger on the front and rear. The last race of the season I put 15lbs of air in the RR, 12 in the RF and 9 on the LS. My kart felt wicked in hot laps, and I spun out running 2nd in the heat due to what I thought was too much air. I dropped the pressures back to 8 on the RS and 6 on the LS. The kart tightened right up.

My question is, how high is to high for air pressure and stagger? What will kill my roll speed through the corner? Being a big boy I can’t copy what the little guys are doing with 5/4 psi.
 

1fasttiller

Member
If it was somewhat working at 15/12psi, I wouldn't have dropped back so drastically. You should have just went down 1-2psi at a time until it tightened up. Higher pressure does reduce friction and adds roll speed especially on a heavy kart. But its a balance between grip and no grip at those pressures. I would have even kept the 15psi in the RR and upped the LR to match it taking out the split. That would tighten it up also!
 

MAS

Member
If it was somewhat working at 15/12psi, I wouldn't have dropped back so drastically. You should have just went down 1-2psi at a time until it tightened up. Higher pressure does reduce friction and adds roll speed especially on a heavy kart. But its a balance between grip and no grip at those pressures. I would have even kept the 15psi in the RR and upped the LR to match it taking out the split. That would tighten it up also!
Thanks for the recommendation. I just got into karting in July so I’ve had a big learning curve. It’s funny because guys look at me like I have 4 heads when I talk about that high of air pressure.
 

1fasttiller

Member
It is very unusual on dirt for sure, even for heavier guys I know that we race with, they aren't much over 8-9psi ever. But if it works!
 

MAS

Member
It is very unusual on dirt for sure, even for heavier guys I know that we race with, they aren't much over 8-9psi ever. But if it works!
How does stagger affect roll speed? I was running 1.5 inch on front and back and noticed a huge difference going to 2 inch stagger. But should I be concerned about too much stagger on the front?
 

Pops90

Member
How does stagger affect roll speed? I was running 1.5 inch on front and back and noticed a huge difference going to 2 inch stagger. But should I be concerned about too much stagger on the front?
More rear stagger will cause the kart to bind more when trying to go in a straight line, since it has more of a tendency to try to turn left. This slows you on the straightaway, but you have to get through the corners before you worry about finding straightaway speed. Basically, if you could drop rear stagger without causing any binding in the corners or causing another handling issue, you should be faster overall. Also, increasing Rear Stagger decreases cross weight, and vice versa.

Front Stagger does quite a few things, but if you don't want to get too far into the weeds, think of it as a cross weight adjustment. Increasing Front Stagger increases cross weight, and vice versa. There should be a post in the Chassis Setup forum right now called "It's All About the Little Differences" that goes into more detail with this. Front Stagger shouldn't affect roll speed directly, since the LF and RF aren't on a common axle.

I have ran very high air pressures on dirt before as well, up to 12 pounds on a clay track with lots of banking and grip. Regardless, get your kart handling like it is on a rail, and then try to find that little bit of extra speed.
 
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racing promotor

Moderator
I’m looking for a little bit of information... we are running a small flat bullring style track. I’m running a 11/70 gear, hitting 7000 rpm at the end of the straightaway. I’m rolling the scales at around 470. I’m currently running 2 inches of stagger on the front and rear. The last race of the season I put 15lbs of air in the RR, 12 in the RF and 9 on the LS. My kart felt wicked in hot laps, and I spun out running 2nd in the heat due to what I thought was too much air. I dropped the pressures back to 8 on the RS and 6 on the LS. The kart tightened right up.

My question is, how high is to high for air pressure and stagger? What will kill my roll speed through the corner? Being a big boy I can’t copy what the little guys are doing with 5/4 psi.
If you have to run that kinda pressure splits to make kart feel right, you have set up issues, what chassis are you on, and what are your current set up numbers including cambers.
 

MAS

Member
If you have to run that kinda pressure splits to make kart feel right, you have set up issues, what chassis are you on, and what are your current set up numbers including cambers.
60% left
53% cross
46% nose
.5 LF camber
-2.5 RF camber

Im running a 2013 Slack Axiom
 

racing promotor

Moderator
I’m a little confused on what you’re saying. Are you talking about the tire pressures I was running?
No he's talking individual weights over each wheel pay no attention to it, he's just doing math.
I agree usually at your weight the set up ends up low cross but have you ever tried higher cross ?
 

paulkish

old fart
I’m looking for a little bit of information... we are running a small flat bullring style track. I’m running a 11/70 gear, hitting 7000 rpm at the end of the straightaway. I’m rolling the scales at around 470. I’m currently running 2 inches of stagger on the front and rear. The last race of the season I put 15lbs of air in the RR, 12 in the RF and 9 on the LS. My kart felt wicked in hot laps, and I spun out running 2nd in the heat due to what I thought was too much air. I dropped the pressures back to 8 on the RS and 6 on the LS. The kart tightened right up.

My question is, how high is to high for air pressure and stagger? What will kill my roll speed through the corner? Being a big boy I can’t copy what the little guys are doing with 5/4 psi.

"My question is,"

I'm thinking your asking the wrong question.

You said in your next post you are new and in your first post told us the kart was wicked and you were running second. From that I assume your kart was good, great and wicked in the heat until you spun out.

I think your question should be about why you spun out and you should be looking to fix the reason you spun out and ride that wicked kart on to first place. ... :)


Where on the track did you spin out? entry, mid turn, exit?

Tell that and folks may be able to relate to it and help you fix the reason for your spin.
 

MAS

Member
"My question is,"

I'm thinking your asking the wrong question.

You said in your next post you are new and in your first post told us the kart was wicked and you were running second. From that I assume your kart was good, great and wicked in the heat until you spun out.

I think your question should be about why you spun out and you should be looking to fix the reason you spun out and ride that wicked kart on to first place. ... :)


Where on the track did you spin out? entry, mid turn, exit?

Tell that and folks may be able to relate to it and help you fix the reason for your spin.
I looped it midway through the corner. I was just hoping to get some suggestions on getting a little more roll speed was all. My weight puts me at a severe disadvantage so I’m looking for any gains I can get. I’ve only run 5 races and the last couple that I finished I was running close to mid pack with about 11 to 14 other drivers
 

racing promotor

Moderator
I looped it midway through the corner. I was just hoping to get some suggestions on getting a little more roll speed was all. My weight puts me at a severe disadvantage so I’m looking for any gains I can get. I’ve only run 5 races and the last couple that I finished I was running close to mid pack with about 11 to 14 other drivers
The added 3 lb in the RR would explain looping it.
 
First off id ask what tire you are on as theres huge differences between tire brands.
At 470 lbs. id be on quite a bit more RF camber. The 60 left side, that more will be along what brand of tire and amount of bite in track, but its in the ball park im thinking. Cross is low.
Next, if the front guys are at 4-5 lbs. of air, a guy at 470 lbs. would be only about 2 lbs. more air, again depending on brand of tire and assuming you are talking a Super heavy class to begin with. With that being said, im agreeing with Race Promoter that theres a set up issue, RF camber, cross is 2 i see right off the bat.
 

alvin l nunley

Site Supporter
I’m a little confused on what you’re saying. Are you talking about the tire pressures I was running?
No, I was talking about your corner weight percentages. The point being, they're quite a bit different from what I normally see. I make no judgment on whether it's right or wrong, if it works, it works, and apparently your setup works.
 

racing promotor

Moderator
I agree with Earl on the tires and pressures, and I'll add sounds like your tires might be to soft or your over prepping them or both. I would try Increasing cross to 62% and RF camber to 3 with air 2 lbs more than the 350 lb classes, and with a 1 lb split to start but not over a 2 lb split.
Don't worry about rear stagger hurting roll speed on the straight If you have NO corner speed you'll never have any roll speed anyway.
 
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