Building a 2000 sunfire for dirt track - Racing Forum

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Building a 2000 sunfire for dirt track
Saturday, February 06, 2010 7:01 AM
I am building a 2000 Sunfire for the local 3/8 mile dirt track. I am looking for someone
to help me with tire sizes and pressures recommendations. I am completely new
to the world of race car building so your input will be greatly appreciated. I have read
in this forum that a lot of guys are running 14's my car has 15's. Should I change them?
Any setup info you can give is needed. Thanks in advance. I will try to get some pics up
soon.

Re: Building a 2000 sunfire for dirt track
Saturday, February 06, 2010 8:59 PM
Hi Shaun on a 3/8 ntrack what works best is 14 inch tires dont know what your track rules allow you to do we run 195/60/14 Falken Azenis they work well on dirt or asphalt being this is your first car get someone with expernce to help you and dont be afraid to ask questions .take your time and do it right the first time spending all raceday fixing problems is not a fun day of racing and will leave you with a bad taste for racing not a good way either good luck any way Ican be of help let me know.
Re: Building a 2000 sunfire for dirt track
Sunday, February 07, 2010 7:16 AM
I have attached wheel and tire rules. Short of this there are no mods allowed accept
after market intake. Is cold air worth the money? Or just a good quality air filter? Which
models can I pull 14" wheels from at the salvage? Do you run stagger or same size all
the way around? Do you have any pressure recommendations?
I know I am full of questions but the local guys won't help due to I will
be the competition. I am sure I will have more, and thank you for your help.

15. TIRES AND WHEELS:
DOT tires only.
OEM steel or aluminum wheel only.
Maximum width 55 series and must fit 8 hoop.
Grooving allowed, but no mud tires.
Any offset wheel allowed.
RIGHT FRONT 60 series or wider only with 40 lbs minimum air pressure.
Right front must durometer 45 after the main event, no cool off period.
All cars in top 5 will be checked for durometer rule.
Re: Building a 2000 sunfire for dirt track
Sunday, February 07, 2010 9:29 AM
You'll definitely want some stagger in the tire sizes. It will help the car turn. A good rule of thumb is the tighter the turn, the more stagger you want, but too much will make the car want to turn in the straights and also it takes a little power away since the inside tire will want to drag itself down the straights. If you are allowed, definitely get an LSD in your transaxle. Asking for tire pressure and stagger recommendations from someone that isn't familiar with your track, or a similar track probably won't help you much. It may get you a very basic idea, but you will have to experiment, or walk around the pits and look at the tire sizes other people are running.

Your best bet for the tire pressures is to get a tire pyrometer. You can dial in your tire pressures and even your alignment specs using it. If your tires read otter in the center of the tread than on the edges, you need less pressure. If they read hotter on the outside of the tread than on the outside, then you need more camber. The goal is to have even temps across each tire. that tells you that you are using the tire efficiently. The right side tires will be hotter than the left side, and the fronts hotter than the backs.

Find someone who has a spring rating machine and try to find some springs that are slightly stiffer than the ones you have. Run the stiffer springs on the right side. Even a 25# rate change can help handling. If you can find factory sway bars for your car,then add them too. Use the biggest factory sway bar you can find in the front. Move as much weight to the left side of the car as you can legally.

More caster will help the return the steering wheel to center coming out of a turn, but will make it a little harder to turn the wheel. It's usually not a big deal for short races, but otherwise fatigue can be a factor. Play around with the caster angles until you find your comfort zone. Set the toe in to between 0 and 1/16 toed out.

I know it will be hard to find different offset rims, but find the ones that give you the widest track width. If you can find rims with more offset, run them on the left side. That will give you more left side weight and help your cornering.
Re: Building a 2000 sunfire for dirt track
Monday, February 08, 2010 10:30 AM
Chris wrote:



Find someone who has a spring rating machine and try to find some springs that are slightly stiffer than the ones you have. Run the stiffer springs on the right side. Even a 25# rate change can help handling. If you can find factory sway bars for your car,then add them too. Use the biggest factory sway bar you can find in the front. Move as much weight to the left side of the car as you can legally.

quote]

This sounds more like a RWD set up. I would NOT do this. Run soft spring on RIGHT side, unhook sway bar. You said this is a dirt track, not asphalt right? You want to roll your front end going into the turns this will give you bite. Stiff spring on FRONT RIGHT will cause crazy push. Look at any videos of fast FWD cars they cary there left rear tire up through the turns, not going to do this w/ stiff right front and sway bay. This is just my Two cents!!!
Re: Building a 2000 sunfire for dirt track
Monday, February 08, 2010 6:28 PM
Yes it is a flat 3/8 mile clay track. We are not allowed any suspension, engine, or brakes.
Re: Building a 2000 sunfire for dirt track
Monday, February 08, 2010 7:11 PM
Well than you better get a hold of Fred Flintstone because I can't help you!
Re: Building a 2000 sunfire for dirt track
Monday, February 08, 2010 10:05 PM
Thers not a whole lot of difference between 14's and 15's we ran both on our grand am to try to get a better gear ratio. I would run a tube in the passenger front if you can. We usually run 28 in the rear, 32 lf and 35 rf with a tube. We ran 40 accidentally in a heat race and the car just wanted to run into the wall it was a real hand full on a slippery track. As for rims Neons, Caravans, 98 I think and older Grand Ams, Berettas. If your running a steel wheel the caravan are really tough.
Re: Building a 2000 sunfire for dirt track
Wednesday, February 10, 2010 4:27 AM
I meant modifications to those items. Guess I should proof read a little better.
Fred and Barney were pretty fast in that old rock wheel car though.
Re: Building a 2000 sunfire for dirt track
Wednesday, February 10, 2010 6:40 PM
Diamond racing wheel has any offset you want pretty much fo a 5x100 bolt pattern. We race a cavalier and fun 16 alum wheels. We haven't tried off set wheels yet. You think a higher offset would work best on left front? I was considering on the right front.??
Re: Building a 2000 sunfire for dirt track
Monday, February 15, 2010 12:36 PM
I was curious what the offset wheels run like $80??

Re: Building a 2000 sunfire for dirt track
Saturday, February 20, 2010 8:19 AM
Thanks for all the thoughts and Ideas. I have read on 4m.net that those guys are running
40+ psi in the rear to loosen it up in the turns. What do you guys think?
Re: Building a 2000 sunfire for dirt track
Sunday, February 21, 2010 11:34 AM
The only reason to run 40 in the rear would be to help with weight transfer, but I think running lower pressure will help the car slide more. With 40 psi your gonna have a small contact patch and that just sounds dangerous to me.
Re: Building a 2000 sunfire for dirt track
Sunday, February 21, 2010 11:08 PM
Andrew Ruschmann wrote:

The only reason to run 40 in the rear would be to help with weight transfer, but I think running lower pressure will help the car slide more. With 40 psi your gonna have a small contact patch and that just sounds dangerous to me.


Disregard that!

The reason why FWD racers are running high pressure in the rear on dirt is so the car "slids" through the corners. If you have a bad push, which you will w/ FWD, over-inflated, worn out tires will slide through the corners helping to get the car to come around. Does that make sense?

If you are too loose then lower the air pressure in the rears and that will tighten the car up.
Re: Building a 2000 sunfire for dirt track
Monday, February 22, 2010 5:36 PM
Yeah that makes great sense to me. I am thinking of running 14's on the car with about 1" stagger in the front and 2" in the rear. I was thinking 185/65-14 lf, 195/65-14 rf, 205/70-14 rr, and 185/65-14 lr. what do you think?
Re: Building a 2000 sunfire for dirt track
Wednesday, February 24, 2010 9:52 AM
Trial and error!!! You will need to experiment to find out whats going to work for your car and track. One thing to keep in mind when talking about stagger, this is not a RWD car. Any info from any one who has experience running RWD cars wont do you any good. I have run reverse stagger on the rear of my car many times. Don't be afraid to try something that makes no sense, just try different set ups. 4m has good info on general FWD set ups.
Re: Building a 2000 sunfire for dirt track
Friday, February 26, 2010 3:05 AM
Thanks for all the help guys. I really appreciate it.
Re: Building a 2000 sunfire for dirt track
Saturday, February 27, 2010 1:57 AM
Cavaliers don't push if there set up right. 40 pounds is asking for trouble. Maybe thats why so many people are annihilating thier rear hubs? We've raced for 5 years and never run over 30 pounds in the rear. I like to set it up that way cause we have to run factory suspension. You put 40 pounds in the factory setup and something is gonna give in the back and cause a rollover. Not to mention people like to run up underneath the backend at our track anyway, don't want the car jacked up any higher. But like everyone said setup is different from track to track. Alot of it the setup is personal preference.
Re: Building a 2000 sunfire for dirt track
Friday, April 30, 2010 9:36 PM
Shaun, as for the question of 14 or 15 inch tires, There are a lot of size choices and usually cheaper 15in tires , a lot of 14 and 15 tires roll out the same depending on what series you are running so you will have to figure out what roll out you need to match your track , a larger roll out gives you a higher gear ratio same as a smaller roll out gives you a lower gear ratio so you will have to size your tire to the track , wont help to tell you what we run , if you are on the rev limiter before the corner then you might try a larger tire , where the 14 inch and 15 inch come into play is sidewall flex , you want some flex in the sidewall to create slip angle, slip angle creates side bit , so very low profile tires are not the best on dirt but too much side wall flex allows the tire to roll enough that you are running on the side wall with no tread which is definably not good , so that is what you have to keep in mind when selecting tires, I would actually recommend staying with 15 inch tires and starting with around a 195-65-15 on a 3/8 track as for the stagger if you are not locking the trans-axle stagger doesn't mean much on the front as the trans allows the wheels to turn at different speeds around the turns and the lack of stagger will help your straight away speeds and handling , although if you are running a locked trans you could use stagger if you cant get the car to turn but we run no stagger and have two cars with 25 plus feature wins . as for the rear..... stagger means basically nothing as the tires turn independently , now what stagger will do for you on the rear is ...... if you run a smaller tire on the left rear it will add weight to the left front corner , really a nice adjustment if you are running a non locked trans axle . You will find it beneficial to run tubes in the right side tires or you will roll them off the beads. also try to get negative camber up to 4.5 depending on banking and speeds ,in the right side tires so when the tire rolls the contact patch stays in contact with the track and positive camber in left side , up to 2.5 . and toe it out 1/2 an inch , as you get more experienced you should experiment with spring rates Pm me with how your car is handling and I can give you some suggestions, Good Luck and have fun
Re: Building a 2000 sunfire for dirt track
Friday, April 30, 2010 9:50 PM
To the OP I read the post about getting rid of the swaybar for fwd racing and you saying no suspension mods. I just wanted to say that some basemodel j's didnt come with a swaybr so technically removing it could still be stock suspension. Idk if that helps but its my .02



Re: Building a 2000 sunfire for dirt track
Friday, April 30, 2010 10:01 PM
or what i do with the sway bar is remove the bolt and rubbers from the sway bar to the lower control arm on the left side if anyone questions it ...... well it must have fell out on the track but I agree i have had no luck with the sway bar on a dirt car , might be a benifit it you are running a non locked trans axle though I dont know

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