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Author Topic:   How to Chnage Bump Steer on Small Metric Chassis
Raceman17
Dirt Maniac

Total posts: 165
posted May 01, 2005 10:33 AM  
I tried to post this question in the bomber section but I havent got any feedback so I have decided to post it here.
I have did hours of research on how to correct the bump steer on a metric. This is what I have found out. Get a 83 Iroc camaro drag link and shortin it 1.5 inches in the passenger side. Then trim back the outer tie rod on the passenger side to get the toe correct. Then maybe bending the idler and pitman arm down 3/8". Is the all that has to be done. This is assuming ALL STOCK uppers and lower control arms along with metric spindels. Also if I start messing with the front roll center of the car after I fix the bump steer, will the bump steer be off again. In other words should I work on bump steer first or the front roll center.
Thanks

tom waara
Dirt Roller

Total posts: 19
posted May 01, 2005 08:00 PM  
[QUOTE]Originally posted by Raceman17:
[B I think you should check your bump steer, but, if your goin to change ball joint heights, spindles, etc. do that first. sounds like your planning on doing lots of work with out knowing the what kinds of problems your trying to fix in the firts place. maybe buy some books and read about front end geometry, . if you apply your efforts to other parts of your car like spring rates, shocks, New tires, stagger, Gearing, sway bar, pitting next to class winners and becoming there friends . if you want to be faster , watch what faster cars do. altering the factory stuff , Ball joint, spindles, etc , should be last, and you should only be doing it because you Know what the outcome will be or what your goal of the change is.
for example ,what benifit is raising your roll center going to have on the track verses having new tires... or having scaled your car and adjusted ballast placement . do you have higher mounting holes in the rear for ballast when its dry slick? do you know what that does? ... it puts more vertical load on your right tire . read. read. read. and mimick the guys who win. and if that don't work cheat, Just kidding

bobaluuu
Dirt Freak

Total posts: 474
posted May 01, 2005 08:36 PM  
thats some excellent advise, goes right along with my theory of K>I>S>S> concerning this sport. most of this stuff your talkin about has minimum effect if any unless you have the total pkg 100% correct. Also if theres a wreck and damage then all your work is for naught. Go have fun and make your priority driving it back on the trailer.
Even if I won the race driving it back on the trailer was another victory to me.

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Light it up, Baby!

Raceman17
Dirt Maniac

Total posts: 165
posted May 01, 2005 08:39 PM  
I won 6 features in a row last year. I have got a fast car. I am a front runner. I just bought 1200 dollars worth of scales so I can get better. Yeah yeah, if its not broke done fix it. Well i know its not right. My car just was faster than the others. I want to start working on the the front syspensions to improve my car. Now, I know for a fact that the bumpsteer on metric car is not good. Also I know that the front roll center on these cars are down in the dirt. This is not where it needs to be. So changing the ball joints will raise the roll center and I know that. Also the bumpsteer on these cars are bad. So, if I can do something about it, I wanna do it. So, can someone tell me if I am going in the right direction. I appreciate your advaice and yes I have done just about all of what you have suggested I was just wanting some confirmation on what others are doing.
Later

quote:
Originally posted by tom waara:
I think you should check your bump steer, but, if your goin to change ball joint heights, spindles, etc. do that first. sounds like your planning on doing lots of work with out knowing the what kinds of problems your trying to fix in the firts place. maybe buy some books and read about front end geometry, . if you apply your efforts to other parts of your car like spring rates, shocks, New tires, stagger, Gearing, sway bar, pitting next to class winners and becoming there friends . if you want to be faster , watch what faster cars do. altering the factory stuff , Ball joint, spindles, etc , should be last, and you should only be doing it because you Know what the outcome will be or what your goal of the change is.
for example ,what benifit is raising your roll center going to have on the track verses having new tires... or having scaled your car and adjusted ballast placement . do you have higher mounting holes in the rear for ballast when its dry slick? do you know what that does? ... it puts more vertical load on your right tire . read. read. read. and mimick the guys who win. and if that don't work cheat, Just kidding


tom waara
Dirt Roller

Total posts: 19
posted May 01, 2005 08:57 PM  
[QUOTE]Originally posted by Raceman17:
[ sounds like you need to CHECK bump steer first. its sound like you have a good car and your a good driver, if you change your roll center height, your required set up set is going change, isn't easyer to just keep winning as you are, and just look at you car, drink a beer are two?

Raceman17
Dirt Maniac

Total posts: 165
posted May 01, 2005 09:11 PM  
Come on guys, can I get some directions. Its my car, I'm the one working on it. I understand that changing everything in the frontend is not easy. If it was easy then everyone would do it. Isn't it good to try new things to make the car better. The track i race on is real bumpy and I know it would help make the car more stable in teh corners.

quote:
Originally posted by tom waara:
if you change your roll center height, your required set up set is going change, isn't easyer to just keep winning as you are, and just look at you car, drink a beer are two?


pdub25
Dirt Full Roller

Total posts: 57
posted May 02, 2005 01:06 PM  
Raceman,
I use 1/2 ton chevy pickup lower ball joints, moog #6117 i believe, and the stock upper ball joints. You will have to ream your spindle to use the lower ball joints. I also did all the modifications to the drag link and tie rods you listed. It definately helps the car in the corner, I highly recommend it over the stock stuff.

Raceman17
Dirt Maniac

Total posts: 165
posted May 02, 2005 01:49 PM  
Thank you for the reply. Do you think I need to look at the angles of the upper and lower arms to decide which arm needs the raised ball joint?

quote:
Originally posted by pdub25:
Raceman,
I use 1/2 ton chevy pickup lower ball joints, moog #6117 i believe, and the stock upper ball joints. You will have to ream your spindle to use the lower ball joints. I also did all the modifications to the drag link and tie rods you listed. It definately helps the car in the corner, I highly recommend it over the stock stuff.


stockcar5
Dirt Forum Champ
Total posts: 578
posted May 02, 2005 07:10 PM  
it doesnt matter where you decide to install a longer ball joint. both upper and lower will only affect the upper control arm angle. to change the lower a frame angle you would have to change ride heights or mounting points. remember though...when you install a longer lower joint it will change your bump steer. installing a longer upper wont

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Raceman17
Dirt Maniac

Total posts: 165
posted May 02, 2005 07:47 PM  
Stockcar5
Am I correct when saying that the reason the longer lower ball joint will change the bump steer is because it moves the tie rod mount up more in relation to where is was previsoly mounted lower. And since this point is moved up, it is on a different arc than when it was mounted lower.
Later

quote:
Originally posted by stockcar5:

...when you install a longer lower joint it will change your bump steer. installing a longer upper wont



tom waara
Dirt Roller

Total posts: 19
posted May 02, 2005 08:46 PM  
[QUOTE]Originally posted by Raceman17:
[B] stockcar5 your wrong, changing the upper ball joint WILL change your bump steer, this happens because now, the upper control arm is at a different angle, this changes the arc it will travel in , affecting the arc the spindle moves in, which affects the steering arm arc which changes bump steer. didyou ever check bump steer on a car? then change things, then check bump steer again? i doubt it

crc1124
Dirt Maniac

Total posts: 143
posted May 02, 2005 08:59 PM  
Check into Steve Smith Autosports. He has written several books on Street Stock Chassis setups and has some computer programs that will help in calculating bump steer. Check out www.ssapubl.com . I agree with you and working on your car to make it better. If you ever get too comfortable eventually you will lose your edge. Good luck, I hope this helps out.

Eljojo
Dirt Forum Champ
Total posts: 968
posted May 03, 2005 04:37 AM  
Build yourself a bumpsteer guage. Remove the spring and replace andy componenets that may alter the roll center. Hook all the tie rods up and install the gauge plate and measure the bump thru three inches of travel in bump on the right side and three inches of rebound on the left. You will probably find that replacing the pitman and idler and rebuilding the drag link will get you very close. To get it to "dead nuts" you will have to do some major work on the spindles, which you will probably opt not to do, as the metric spindles aren't overly strong and seldom survive crashes anyway.

rico 08
Dirt Forum Champ
Total posts: 1139
posted May 03, 2005 06:05 AM  
I'd post this in the modified section...those guys play with bump steer 'till they are wacky

stockcar5
Dirt Forum Champ
Total posts: 578
posted May 03, 2005 10:48 AM  
you are corret raceman17. the upper has very little if any effect on bump steer. dont pay any attention to tom...he just gets off on causing trouble.

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speedyd1
Dirt Maniac

Total posts: 170
posted May 03, 2005 03:29 PM  
instead of loking for solutions - why not figure it out for your self. buy the software. it allows you to change the lengths , angles, etc to see exactly what it does. it was far more valuable to me than any advice i got from fellow racers. i paid 100 bucks for mine at a local speed shop and bought a book for 30 bucks that went with it. it is so simple to use that all you do is take the measurements of what you have and enter them. it has a provision for each figure to be changed so you can see each result for each change. let me know if you are interested and i'll provide you with the proper information where to buy it. we modified the stock parts to work as well as they could and achieved pretty good results. it made all the difference in the world. the best money i have ever spent. other than my digital scales.

yenko
Dirt Full Roller

Total posts: 28
posted May 04, 2005 06:24 PM  
What kind of software is it?

bobaluuu
Dirt Freak

Total posts: 474
posted May 06, 2005 09:23 PM  
I have a good bumpsteer guage I'll sell ya if you need one.

    

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