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Author Topic:   fine tuning chassis question
Dirt Roller

Total posts: 15
posted June 22, 2004 04:41 PM  
hey i'm looking for some suggestions on fine tuning my car. it's fast but could be faster. i'd like to tighten it up or get more bite between the center and exit of the turns (mostly exit)without screwing it up anywhere else on the track. car is a 4 bar lr, z link rr. here's the numbers
springs: 650 lf - 750 rf - 225 lr - 225 rr (on swingarm, 188 lbs at wheel)
weights : total 2341 (no driver) lf - 502 rf -472, lr-721, rr-647--58.4 rear, 52 left, 51 cross
shocks lf- 76, rf-76-4, lr-94, rr-94

i was looking to try some different shock combos, pull bar adjustments, and rr z link adjustments as i think the rest of the car is close and i'm not as experienced with these. any suggestions would be nice to see. thanks--------smoothshoe

Dirt Full Roller

Total posts: 45
posted June 22, 2004 10:18 PM  
how is your spring mounted on the 4 bar ? clamped up or on top of the housing?

Dirt Roller

Total posts: 15
posted June 22, 2004 11:48 PM  
hey jason, the lr spring is on the birdcage behind the housing. thanks in advance

also we have a progressive spring in the pullbar. were thinking of trying something else. any experience?

Dirt Freak

Total posts: 209
posted June 23, 2004 02:44 AM  
it will always be a compromise, i don't think you can change any part of the car and have it effect just one area, but you're right that you can always make the car better.

* indexing your left rear birdcage (lower the top rod on the birdcage).
* lift the left top rod one hole at the frame.
* a little more cross weight (left rear bite)
* shorten the left upper link
* raise the left lower rod at the frame

try one at a time, each will have a little different reaction and side effect.
this is what we can do on our 4-link latemodel.

Dirt Forum Champ
Total posts: 796
posted June 23, 2004 06:56 AM  
Try working with your shocks more, there the easy-est thing to change while at the track during racing. I think this is one of the most overlooked adjustments.

Easier up shocks on the front (more fwd bite, promotes a push out thou), a drop down shock on LR (loads left rear tire and keeps it loaded longer, promotes oversteer on entry thou). Runnning lighter dampening all around will help roll the weight faster (sometimes hard to drive if your not smooth with the wheel) and load the tires up faster.

Plus shocks are more of a subtle change. Changing bars and location alot of times your out to lunch or dialed, one or the other usually. Seems like there often to much or not enough.

Also you may expieriment with some ride height changes. 1 inch higher on our car and its like a different car, rake fwd to aft (front lower then the rear) makes a huge difference as well.

Dirt Roller

Total posts: 15
posted June 23, 2004 04:33 PM  
those are some good ideas. I've never moved the top link down at the birdcage. does it spin the birdcage faster than moving the link up at the chassis?

I gotta get some new shocks as i don't have the shocks i would like to try. i have a 76-2 that was on it to start the season, but this is our first season on this suspension, so we changed a bunch of things cause the car was tight all over, but i may stick that shock back in and see what happens.
thanks for the ideas...

what do you guys like to run for shocks?

[This message has been edited by thesmoothshoe (edited June 23, 2004).]

Dirt Freak

Total posts: 209
posted June 24, 2004 05:26 AM  
i can't comment on the shocks as we don't change them (maybe we should???) we just run the manufacturer's recomendations wich a straight valvings.
lowering (indexing) the left top rod on the birdcage will have less of a "bite" effect coming off the corner than raising it on the frame. our car tends to just loosen up slightly when you first get off the gas to enter the corner as the car sort of settles/comes back down which unwinds (deindexes) the birdcage unloading the spring more than normal. this reaction took me by surprise the first few times and i looped it, but once you get the hang of keeping the car straight and under you as you enter and brake for the corner it seems to work well. it would be worthwhile trying, you may not like it or you may decide it to be a valuable tuning option.

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