2012 Impulse Help to get more cross

R

reg-man

New member
Hello Folks,
Maybe someone can point me in the right direction on this subject and yes I am new to Gokart Racing!!
Having trouble getting my 2012 Impulse cross number up!
Last scale numbers are:
Left side =58.4 %
Rear = 54.6 %
Cross = 63.7 %
Stager was front 1 1/2 and rear was 1 1/8. both left side tires are 33 in.
Tires were at LF-5lbs, LR-6lbs,RF-6.5 and RR-5lbs.
I was cheating on the above tire pressure to try to get every percent of cross I could. I normally run 5 lbs left side and 6 lbs right side.
Kingpin washers LF = 3 on top and RF 3 on bottom.
Total with Driver and weights - 374 lbs. No helmet and gear. (Pro Clone Heavy 375 class.)
Camber is set at LF is +.50 and RF is -3.25
Caster is set LF 6 degree and RF 10 degree.
Running on a 1/5 mile medium bite track with 9 and 11 degree turns.
These are suppose to be High Cross Karts but I just can't get the number up any higher. I did find a top kingpin bearing crushed but I had already replaced all front bearings before I scaled this last time.
Like I said, I'm new to Karting this year and I'm just trying to learn.
Thanks for any advise.:cool:
Reg-man.
 
Sorry just saw this. First thing I would do is resize my tires. Shrink the LF to 32.5" and get both rights to 34". LR is fine at 33". Looks like you already know this, but most will run same pressure in both lefts and both rights. Some use a 1 lb split between left and right sides, some use a 1/2 lb split and some no split at all. Just have to see what works best for you. I like a 1/2 lb split. The only number that looks way off to me is the front, which is too low. Get the front to at least 47 and maybe even 47.5. Left looks close, maybe go to 59-59.5. RF camber looks a little high, but some like it there. I'm usually around -2.75 on RF. See where that puts you on cross and you still have a few washers you can move. See what axle bearing cassette pills you have in the back. Most like to run 0's, but you can use the 1/16 or 1/8" pill to help get more cross. 66-68 is a good starting point and adjust up or down based on track. Good luck... it's a good kart. And after you get all this down, you'll find that by far the most important thing is getting your tires right! :) Good luck.
 
More nose, less rear stagger, and check for a bent spindle in the front. If nothing else, get some pills for the rear to get the cross up
 
What you haven't said is; why do you want so much cross? You already have a big percentage on the LR, more cross will just increase that. Not that I know anything about this stuff, but, numbers are numbers.

Something I've always wondered about; what happens to your cross when you turn the wheels to the left?

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Thanks Guys for your info and insight, Here's a quick update on what I found.
First I want to answer Al Nunley. I really enjoy reading your comments on the forum I guess mainly because my friends say I'm too meticulous about things like this but I also believe the numbers won't lie.
Quote; What you haven't sais is; why do you want so much cross?
Answer; These are High cross karts and this is a 2012 that I bought used and once I started going thru it, I could see that it had been raced a Lot!!! I mainly wanted to get the cross up in to the High 60% range just to prove that the frame wasn't bent. I was getting worried when I had everything almost maxed out and was still barely at 64 % and I'm happy with 63 to 64 % as long as it is my choice, Not because that's all I can get out of it.
I first talked to badhabbit77 on the phone and he advised to possibly replace the spindles. I did have the 14X left spindle so I replaced both front spindles with new ones. unfortunately this only helped the cross number by approx. 1 to 2 % more.
I finally went back and read the Impulse PDF Manual for the 50th time!! and realized I hadn't checked the pills in the rear cassettes.
The manual states LR Pill for Jr sportsman classes is Zero and for Adult Classes who need more cross, use a 1/16 Pill.
Haykeye79 and Zach,
You were right!! When I went to the 1/16 Pill my cross went up to 68 %. I was then able to change washers and weight to get 64% cross with the nose at 47.5% and the left side still 58.5%. This is the numbers I wanted as a starting point. I haven't got to take it to the track yet but maybe next weekend I'll see how it does.
Thanks again,
reg-man.
 
inpulse98,
The Left L Block is 14 degree with a brand new 14X spindle.
The right L block is a 10 degree also with a new spindle.

Thanks.
 
Reg-man you should be in the ballpark with those numbers. If the track gets hard and fast, don't be afraid to add even more cross. Let us know how it goes after you hit the track. Good luck.
 
Hey,
I reset the Cross to 68% and the camber to LF-+.50 and RF -2.75.
Question is that there is now 153 lbs on the Left Rear. Thats seems to be a big percentage out of 373 total lbs. Is it too much on the Left Rear?
Thanks,
 
If you changed the cross to 68, you might have changed the Left.
Total Kart&Driver
373
Front
45.4
Left
58.4
Cross
68
Left Front %
17.90%
Left Front lbs
68.44
Right Front %
27.50%
Right Front lbs
101.29
Left Rear %
40.50%
Left Rear lbs
146.91
Right Rear %
14.10%
Right Rear lbs
48.37

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
reg-man said:
Hey,
I reset the Cross to 68% and the camber to LF-+.50 and RF -2.75.
Question is that there is now 153 lbs on the Left Rear. Thats seems to be a big percentage out of 373 total lbs. Is it too much on the Left Rear?
Thanks,
Click to expand...

I'm not saying Al is wrong about taking corner weights into consideration, but most would say don't worry about it as long as the percentages are where you want them. I'd go with it and see how it works for you.
 
Hawkeye79 said:
I'm not saying Al is wrong about taking corner weights into consideration, but most would say don't worry about it as long as the percentages are where you want them. I'd go with it and see how it works for you.
Click to expand...
You don't say I'm wrong, but you do infer it!

You put your kart on the scales. I've never seen a set of scales, so I'm only guessing, but I assume you can switch the readouts to show corner weights, or percentages. Or maybe it shows both at the same time. Let me know.

From some source, you got the percentages you should run. Let's say, front 46%, left 58% and cross 63%. With you and your kart on the scales, the percentages read 44%, 55% and 60%. Now I'm sure there are people out there, with lots of experience with scales, who could fix this with no further information. Could you? That is, "could you", or anybody, with just those numbers. Wouldn't you have to look at the corner weights to see how much you would have to change them to get the percentages you want? I'm sure you could guess, just keep changing things until the percentages came up right, but wouldn't it be nice if there was an easier way?

With my software, you can put in the total weight, and the percentages you want, and the software tells you what each corner has to weigh to achieve those percentages.
The percentages will only be right when the corners are right.
Click to expand...
Or, you could just put in the corners and the software will tell you what percentages you now have and the total weight. (Which reminds me, in the first example, you don't know the total weight yet. Oh, you do know it from the last time you weighed at the track, and you could use that, but then you don't know how accurate that is.) With my software, you can play with the corner weights, (right in the computer) adding or subtracting, until the percentages are what you want. Then it's just a matter of adding or subtracting from the actual corners until the corner weights add up to the right percentages.

My point is, you have to know what corner weights you have, right now, to calculate (either you or the scales) what the percentages are. You then have to know how much you need to change the corner weights to get the percentages you want. If you can do that in the scales software, which I don't know if you can, that would be great, but the software is still easier I would think.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Geez, Al... I guess you've been battered on here so much that you are conditioned to see "slights", even when none exist or are intended. I wan't inferring anything, just making an accurate statement that most just worry about the percentages. I haven't really given your theories enough thought to form an opinion as to whether I think they're right or wrong. However, if there is a certain weight for each corner that gives you the percentages you want, wouldn't it also mean that if your percentages are where you want them, your corner weights are also correct?

To answer your question about scaling a kart, yes scales do give you the 4 corner weights as well as the percentages. Unfortunately, it's not as easy as changing this corner to this weight and changing that corner to that weight. Making a change in one area affects the others as well. We can move washers, weights, the engine, the seat, etc., but each change affects more than just one corner. It's a balancing act where you make a change and look at your percentages. When the percentages are where you want them, you're finished. Again, I'm not saying you're wrong. I simply don't know any way to get the percentages I'm looking for and worry about the wheel weights at the same time. I'm certainly no "expert", so if there is a way I'd love to know it.
 
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