Running box stock predator with grooved tires. Been fooling with the gearing. It was said that on the track I should be looking for 4800 to 4900. I finally figured that I need to be on a 14/58. We had a test and tune last night. I went on the track several times. The last time I went out was my fastest laps. 11.35 with a 700 rpm drop I was a few rpm shy of 5000. On the other hand another time out I was at a 11.65 with 1300 rpm drop and turning 4650. I see that if I lose that much rpm drop I probably won't turn the 4900 or 5000 at the end of the straightaway. It finally makes sense. Now I just have to figure out what I am doing different from lap to lap.
Light finally went off on rpm drop
- Thread starter bullerman
- Start date
It don't sound like a lot of RPM at 4900, it took us a while to figure out these predators don't like RPM. Coming from the old flathead days it just didn't make sense to us, we would keep running big gear to get RPM up and we were getting outrun, we went to about 5200 on the track and looked like we were cheating because we got so much faster, we even went down to about 5000 and were better at that RPM.
Colt sr
Member
Short answer is you are running a different line or lifting off the throttle a different points of the turn each time around the track
paulkish
old fart
Just a wild guess.
Your not unloading your left rear tire in the turn.
And your changing your line to keep it from pushing and make it turn better coming off the corner?
Maybe the reason it's better at lower rpm is because your going slower in the turns and the straight is taking care of itself?
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Your not unloading your left rear tire in the turn.
And your changing your line to keep it from pushing and make it turn better coming off the corner?
Maybe the reason it's better at lower rpm is because your going slower in the turns and the straight is taking care of itself?
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Yes I am sure I am not running the same line everytime. I am running close to the same distance. Usually around 575 feet and I am sure I am on and off the gas at different points. One question so. I am running a Hossier 11.0 x 6.5 x 6 on the left rear. It has a 35 1/2" roll out. I run a Burris 11.5 x 7.00 x 6 on the right rear with a 36 1/2" roll out. Gives me 1" of stagger. Tread width is close to the same. Does this make any difference as long is the stagger is ok? Could it be the left rear is to large? I did raise my seat for comfort. I am at 10 1/2 " off the top of axle. I was at 9 1/2". I thought with the large size right tires it might help.
Guess I need to get a set from Brian Carlson that are what I should be running. He says he can mount smaller tires with a 34" right side roll out.
Thanks for the suggestions.
Guess I need to get a set from Brian Carlson that are what I should be running. He says he can mount smaller tires with a 34" right side roll out.
Thanks for the suggestions.
Did the trail braking thing last night. My rpm drop was lower and lap times were good. Still turning about the same max rpm on laps. They say to turn the box stock in the 4800 to 4900 rpm range which is where I am at. I am wondering if the motor will pull better in the 4600 to 4700 rpm range. I will just have to try it and see. We have two races left. If I have the points championship won next race I will try it the last one.
racing promotor
Moderator
Not saying it wouldn't possibly work for you , BUT if it did it would be the minority by far We've already put it to the test and 4825 is pretty much the sweet spot, Now I will add this we can achieve that RPM with 1 or 2 less teeth on the rear because our tire program is solid, our set up has been tweak, and our driver is great at maximizing momentum.
paulkish
old fart
If you win the points then at the last race put your bigger RR tire on the LR and the smaller LR on the RR.
When the kart comes in after practice, fix what ever you think needs fixed to make it go around better.
Then before you go out for the first heat swap the rear tires back to where they should be.
... try it.
When the kart comes in after practice, fix what ever you think needs fixed to make it go around better.
Then before you go out for the first heat swap the rear tires back to where they should be.
... try it.
Finished second the other night. They checked our motors on the stand. We have the 5500 rpm rule. The kart had set probably 40 minutes or so before they checked us. I undid my tach so they could use the one the track has. It's a mychron 4. It wouldn't work so they used mine. I reved it up and held it for three or four seconds. I was at 5478rpm. I had checked on the stand here at the house. I was at 5377rpm and motor surging. I thought I had it set. The motor wasn't hot like after a race. The last couple of times I adjusted it I did it by adjusting the nut on the accelerator stop spring. I am turing 4800 to 4950 on the track. If I back it down to 5200rpm on the stand Wonder if it will hurt me that bad on the track. It may put me in the 4600rpm to 4700rpm on the track.
Don't want to get DQ.
Don't want to get DQ.
SoCo Tire Treatments
Moderator
Its one of the checks they do for stock Predator, its an RPM rule with some wanting the surge as well.
Colt sr
Member
I revved one of my flatheads on the stand once. After that engine completely shut down and wouldn't kick over again I never have and refuse to Rev on the stand again. I sent the engine to my builder who told me that the valves were bent. That was stupid on my part and a costly mistake. I had just got that engine back probably 2 weeks before I done that.