Track Tac

proper rim width for the tire

foreverfaster

foreverfaster

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I have a new set of tires. i have the right sides mounted.. no brainer.. 11x8.1-6 on 10 inch wide rims

what to do with the left side
Bruiss 33A tires
11x6-6 and 11x5-6 what rim for which tire and when it's done which in the front and which in the back??
as a note.. i have NO intention of cutting or preping these tires..
will likely run 1/6 wet dirt oval with them when done.
 
You just got the right wheels sizes, but If it's a WET dirt oval and you have NO intent on prepping don't figure on running up front, unless it's a 33 only rule your on the wrong compound to start with for wet dirt, then NO prep on top of that your gonna be looking for a lot more grip than your gonna have.
Now what you call wet and I call wet may be different I guess but wet is wet.

Good Luck !!
 
thanks you two.. the track is yet to run karts, currently they are running micro sprints and mini sprints up to 650ccs.. we are hoping to start karts there soon and run maybe a sunday show following the saturday sprints. Jackson speedway jackson michigan.. they just pulled 18 to 24 inches deep of the track up all the way around and pulled all the stones and rocks out.. added more clay and put it all back in..
i've not had the pleasure of actually racing my kart yet.. the reason i mentioned the "wet track" is the sprints like it on the wet side.. Hoping that by sunday race time i will be packed some and some of the wet will be out..
 
If the track stays wet, i would put the left rear on a 8 1/4" wheel to give you a little softer sidewall in that tire, which will give you a little more forward bite off the corner where you need it. I have ran the right sides on 9" wheels and left rear on 8 1/4" wheels alot when we go to wet tracks and have always been up front with that combo, because the taller/softer sidewall will give you more sidebite in the corners on a wet track like that, especially when you have the tires uncut, full rubber tires. If the track usually dries out some and doesnt stay wet, i would definitely be on 10" right sides and 8 1/4" left rear. If track dries up and has good bite, 10" right sides, 8 1/2" left rear. All our left fronts are on 6x6.5" wheels, i do keep 8 1/4" and 8 1/2" left rear wheels on hand for when i need to change stagger or need more forward bite off the corner. If the track is smart, they will leave the track packed after saturdays race and not dig it back up, then just water it on sunday before you guys race and roll it in, that should make for a decent bite track if you have 30-40+ karts running 5 or more classes. Keep in mind, running 33's, you will need to be prepping them just about every time you go out if you plan on being competitive. If there is no tire rule, i would be on SS11's or SS22's instead of SS33's since you do not want to cut or prep the tires at all. Make sure your kart is set up with low cross and low left percentages and lower right front camber if you dont plan on prepping tires, that will help get you some bite out of the chassis and get the tires into the track a little more in my opinion. Keep your air pressure very low when the track is wet, i would start out with 2lb on all 4 corners or 3lb on all 4 corners, and as the track gains bite, raise the air about 1/4 or 1/2lb in each tire. I usually start on 3lb all the way around for wet tracks and as the track gets bite, i will go up 1/2lb in all 4 tires and usually will increase the air pressure split from the same on all 4 corners to putting 1/2lb more in the right side tires than i put in the left side tires, if that makes sense. On a good bite track, i use a 1lb split from the left side to the right side tires. Lower air will give you more bite and keep you planted on the track more so you arent sliding around
 
W5R, thanks for all the input.. i'll print this out and put in my book of notes..
that was my thought on racing sundays.
"If the track is smart, they will leave the track packed after saturdays race and not dig it back up, then just water it on sunday before you guys race and roll it in, that should make for a decent bite track "

Thanks
 
Rear rim width has to do with what you want to do with it. Put the tire on a narrower rim, it affects the spring rate of the tire. Meaning it makes the tire lazier to transfer weight. So, given all remains the same, a narrower rim means weight transfer will be the same but more weight will transfer at the front and less weight will transfer at the RR giving the LR more grip. This is fine if the track has little grip. In this case you have to "plant" the LR into the track to get the drive off. W5R nailed it spot on. The only thing disagree with is the air pressure. Lower air pressure equals "greater" rolling resistance. That means the kart will be bogged down. An example: I was helping a guy out that weighed 435 kart and him. Made adjustments to his air pressure and tire prep. Went from 4 psi to 10 psi with less prep. He went from the back of the pack to running stock medium times!

Here is where everyone messes up, say for any class, the max weight is 350 lbs. The setup, tire pressure, tire prep, will be different for a 6'0" man at 200 lbs, than a man 5'8" at the same weight. It has to do with the CG and VCG. The stiffer the tire the greater the spring rate which equals more weight transfer to that tire.

Mike McCarty
The "Original" Chassis Manual
 
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