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Author Topic:   rr kicking out on straightaway
washeduptoo
Dirt Maniac

Total posts: 155
posted October 10, 2005 07:14 AM  
Metric clip car,4-z rear suspension. 225lr spring on b/c behind, rr 200 on top, I believe 850 across the front. About 60 lr bite. Rear end is square in car. We added some more lr 3rds and car was better, still not there. 58% rear wt.,ls 53% 49% cross. These were the numbers before we added the lr Saturday. We not going to run but 1 more race and we are going to scale car again, just need input before we scale. Thanks guys for all the help. We were running the 4-2 before our bracket broke. Going to run 4-z last race.

GRTWallbanger
Dirt Maniac

Total posts: 196
posted October 10, 2005 12:16 PM  
Our 4 bar z-link did that exact same thing when we went to a half mile track.I flattened out the RR, rear trailing arm and it fixed the problem.

washeduptoo
Dirt Maniac

Total posts: 155
posted October 10, 2005 04:18 PM  
The rearward facing bar is almost level at ride ht., it probably is angled upward alittle, that is where we run it on dry slick. Thanks for the input. Do you or anyone else have any other thoughts on what causes it not to run straight down the straightaway, the rear end is not following the front end, not bad but it is doing it.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted October 10, 2005 04:36 PM  
is the car losing its traction or just the rear end tracking???? If its losing traction, it could be the pullbar spring is too stiff or too much downhill angle. Might decrease angle or preload.

washeduptoo
Dirt Maniac

Total posts: 155
posted October 10, 2005 04:46 PM  
The driver said it had good traction, it just feels to him the right side is pulling more than the left down the straight and you can see the rear end not tracking with the front if your watching from the back of it, its not bad, but it could be better.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted October 10, 2005 04:51 PM  
have you checked your wheelbase on both sides??? Basically what your saying is the RR is getting more thrust than the LR, correct?? Check the wheelbase, also is the pull-bar centered in the car or offset? If its offset right, it could cause that. With the RR rear bar almost level, thats cutting most of the RR thrust (from what I understand on a z-link, cause I've never ran one) so decreasing angle there isn't gonna help. Where is the RR lower bar mounted, in terms of angle?

washeduptoo
Dirt Maniac

Total posts: 155
posted October 10, 2005 05:33 PM  
We have markings on the underslung from chassis builder that we use determine if rear end is straight in car, I guess something could be bent causing our markings to be off. The forward facing bar on rr is also level at ride ht. The pull bar is not centered, it off set to the right a little on the rear end. I hadn't thought about the pull bar might be causing it, we moved it over to get some more side bite. Thanks

[This message has been edited by washeduptoo (edited October 10, 2005).]

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted October 10, 2005 05:45 PM  
that might be your problem.

moldy97
Dirt Roller

Total posts: 6
posted October 10, 2005 05:51 PM  
With the 4bar. Tucking in on the left rear under power is rear steer you can take some of it out unless you need it to turn on the left side or add more stagger to compensate for the angle taken out.You can also if you want the angle on the left for tight tracks move the right lower bar up a hole bringing in the right rear but this will tighten up the car. Usually you only notice the rear ned walking around on a dry slick track and could use tightening up

washeduptoo
Dirt Maniac

Total posts: 155
posted October 10, 2005 06:15 PM  
I thought that raising the rr forward bar would loosen the car up all thru the turns and give it more forward bite? I also thought the lr lower bar worked the same way. Please someone correct me if I am wrong. Thanks

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted October 10, 2005 09:40 PM  
yep your right washeduptoo.

Kromulous
Dirt Forum Champ
Total posts: 796
posted October 11, 2005 07:54 AM  
What Moldy is saying is, if your on a 4 bar on the LR it promotes alot of rear steer. The rear end may be square in the car sitting in the pits, but when its up on the bars going down the straights, it will have some degree of rear steer in it.

The driver has to compensate that by coutering it with the wheel, so the car in essence will be dog tracking down the straights. Only cars i ever see that dont do this is 2 links and double Z's mostly.

If the RR is out pulling the LR it will continue to come around, which can be quite handy going into a corner on a tight track. Anyway thats telling you the RR is out pulling the LR. Bar angles and panhard bar offset will be the culprit.

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted October 11, 2005 09:25 AM  
Yes, the car will dog track reguardless with a 4 link if the rearend is square in the car at ride height. It sounds like you need to drop the Lower RR bar down a hole or two. This will tighten the car some, but will lose FWD Bite. If he drives through the pits at an Idle with a peice of tape on the wheel straight up, on the track to go straight that tape will be between 1 and 2 o'clock.

washeduptoo
Dirt Maniac

Total posts: 155
posted October 11, 2005 06:10 PM  
I now understand what yall are saying. I'm afraid if we drop the lr bar lower it might get too erratic, it is already running down hill. We are running the straight pan hard bar under the center of the pinion now. It worked well the other night on dry slick, and wasn't as erratic as the short bar was earlier. We might give lowering the bottom lr a try during hot laps to see how it works, thanks a bunch.

Kromulous
Dirt Forum Champ
Total posts: 796
posted October 12, 2005 06:37 AM  
Remember the less upward angle in the LR lower bar you have is less LR drive. This could be an issue, also make the car tight in.


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