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Author Topic:   Throttle push or side-bite???
dluna
Member
posted July 24, 2002 02:04 PM
Hello again everybody.
We have a 2-link dirtworks car. Last week was the best we have ever run on dry-slick. We finally got our rear % up to 60%. The cross comes out to be 51 to 51.5. This is pretty much a fine-tunning question. When running low, once we get back on the throttle, the rear-end will start slipping sideways toward the top of the track and the only way to keep it from coming all the way around is to let the car glide (push) on up the track, allowing others to get on the low side to challenge for the position. Does this sound like a throttle push? or is it more likely a problem w/ side-bite? We only had about 80lbs of bite in the car. The prior week our RR was burning hot after the feature...so we hung weight up high near the RR wheel. Should we try to go w/ a lighter spring instead (RR is 150) and put the lead on the LR? THANKS in advance.


hm
Member
posted July 25, 2002 08:08 AM
It's not a throttle push, a throttle push will occur when you are using your LR (mostly) when you get to the gas. That will force the front end up the track (1st), What your doing is chasing the rear end, if your RR is burning hot like you say it was, your loose. I don't know that I would recommend a lighter RR spring if your already at 150, there is lots of things you can change, but I would move that lead from on top of the RR to the LR, but try and keep it a little lower. This will not fix your problem, it will only help. If you get your cross % higher you will most likely fix the whole problem.


dluna
Member
posted July 25, 2002 08:35 AM
Thanks for the reply.
I do have another question though. If the RR is burning hot without any lead on the right side, what does putting lead low on the left side help? Not questioning your theory, just would like to understand. If I was going to put the lead on the LR, I would have put it up high so when you go in the turn, more weight would transfer (than if it was low on the LR) to the RR, in turn making it work instead of spin. I'm confused...but what's new
Thanks again.


race8k
Member
posted July 25, 2002 11:33 AM
The tire is not hot because you are spinning it.It cannot spin any faster than the left tire since they are hooked together.The tire is hot because it is doing more work.Jack some weight to the left rear and the right should cool off.


dluna
Member
posted July 25, 2002 12:47 PM
See I was in the mind-set that since the RR was so hot...the LR was getting traction and the RR was not getting traction (spinning instead). When it was really hot, we had a chunk of lead on the LR, but the rear % was only like 57.5%. So should we just add more lead to the LR to get up to 60% again and see if that will keep the RR from getting so hot? How much LR bite do you want to have on a dry track? Does anybody know on average what the wheel weight difference would be going from a 150 to a 125 RR spring (RR on top of rear-end, LR in front)
Thanks again!


nvracer
Member
posted July 25, 2002 01:09 PM
It might help to decrease the stagger this will increase you cross and help the loose off condition.


dluna
Member
posted July 25, 2002 01:17 PM
We only run 1/4" of stagger in the rear and about 1" - 1 1/2" in the front on dry-slick. Does this sound ok?


dirtbuster
Member
posted July 25, 2002 02:34 PM
We are having the same problem. We also moved lead from over right rear to left and it didn't seem to help much. Running with 50# lr bite. Seems like when we ran less bite this helped the car come off better. We are going to try 20-30# this week and see what happens.


Race8k and HM

You are saying that since the right rear tire only was hot that the car was loose right. Because it was doing all the work

If both rear tires are hot and within 20-30 degrees of ea other then I would think both tires are spinning? Does this make since. This is the problem we have.


hm
Member
posted July 25, 2002 03:50 PM
Unless your really (really) spinning tires, the heat is coming from the tire that is doing the most work, even temps are good. The idea of moving the lead lower on the LR was only to prevent the car from rolling over on the RR as much, it really only has a minor affect, but it will help. If the car was better with more rear % (should be on dry/slick) then I would leave the rear % there, just add bite, problem should go away.


MOD RACER#93
Member
posted July 25, 2002 07:07 PM
Thanks for the reply!
Our car hooks up really well on tacky. We run a J-Bar whenever it is tacky, and we have tried both a long bar behind the rear-end and a short bar in front on dry-slick. We just run a cheesy 406, but can hook EVERY bit of it up on the tacky. When it turns dry, not so much love! We even went down to 2-barrell last weekend to see if that would help (didn't seem to hurt or help either way). May try setting out timing back this weekend to see if that will do anything for us. I thought adding air to the tire would add weight to that wheel. Maybe it helped for a different reason than that. MOD93, do you run short, long, or combination (short LR, long RR) trailing arms? I am thinking for this weekend we will try to keep the 60% rear, and just put 100+ lbs of bite to see if we can get the LR to do it's job Does this sound like a decent idea? Maybe try and put the LR on top this coming week to see if it will help.


MOD RACER#93
Member
posted July 25, 2002 10:09 PM
28,

Where do you run your jbar at? That can affect sidebite getting in. We run ours low.. bottom hole on the pinion mount and about 9 inches up on the frame from the bottom of the frame.

Also rearend placement. Running the rearend offset to the left or using wheel offsets tomove the tires to the left will help with sidebite.


dluna
Member
posted July 26, 2002 10:22 AM
28,
we have tried 3 different panhard bar types in the last 2 weeks. We added brackets to put the long panhard bar mounted to frame on RR and rear-end on LR. We tried running the j-bar when it is tacky (and the car is great like you say Mod93), and when it turns slick, we either put the long bar behind the rear-end, or flip the bracket on the pinion and put the short bar on. SO far, we have had the most success w/ the short-bar on dry-slick. BUT, we didn't get a chance to try the long bar with our rear % in the 59.5 to 60 range. Gonna try it this weekend. THEN, may try what I heard others talking about sometime soon. 30lb of RR bite, short-bar, and lead the LR by 1 inch. sounds FUN

Can I get others opinion on heat in the RR? I was almost convinced by previous post on this thread that if the RR is hotter, it is doing more work, UNTIL I went back to basic physics. If something is rolling, it creates LESS friction than if something is sliding. SO, w/ the rear tires 'hooked' together, if the RR is hotter than the left, it MUST be spinning (friction) more than the LR...not doing more work! I could be wrong here, but it makes more sense to me this way.

Thanks everyone!



dirtbuster
Member
posted July 26, 2002 11:03 AM
dluna,

I am not sure here but i think you may have it backwards on the rolling versus sliding friction. I beleive a rolling tire has more friction at the contact pont than a sliding tire. Think about antilock brakes. They allow you to stop quicker by keeping the wheels from locking up and sliding. Therfore i would think there is more more friction between a rolling tire and the ground.

I spoke with dirtowrks about the problem of driving off the corner (we have it too). They told me that with that much rear % (59-60%) the car falls on the RR and then there is not enough spring to hold it up and push it back on the left rear to drive it off the corner. They told us to take out our 150 RR and put in a 175RR nad 200LR and try that or take off weight which i dont think we want to do. If it helps we may even go to a 225LR and 200RR.

Do you have a lot of preload on your RR spring? I know we do, that is also a good indication that we should have changed to a stiffer spring.

Anyway we are going to try a stiffer spring this weekend and see what happens. I will post what happens

28
Member
posted July 26, 2002 12:38 PM
Ok here i go!! After reading all the post above most of these things i have tried this year with big affects. First i would like to say that what was said above about moving the rear over by offsets or moving the rear will make a huge affect on the entry and sidebite if all else is were it needs to be.(dont try this on a heavy or real tacky track feels like your gonna go over) The spring preload on the rr seems to be very important also allot more than the lr and if it is allready preloaded to much, on entry it will slide the rear from not enough roll in it, or you make changes to get more roll out of it making the car erratic in the middle as it took the first shot of weight going in then rebounding it from the over preload on the rr spring. Now i also found that the more angle in the pullbar on the tacky track and lots of roll in the car as soon as you touch the throttle it lifts the chassis keeping the LR up making the rr feel like its not stiff enough so bringing the bar down allows less lift and lets the car maintain threw the turn and off. We have been working on all these changes this year to see what we will get for affects and been tring to keep it all sorted to help us in the future with fast changing track conditions. We have gone from keeping the lf up all the way down the track to sliding the rear up the track with a few small changes with the springs that are in the car to save time. I hope some of this makes sence and could go more into detail on 1 certain thing if you need, I could ramble on for a bit but ill stop here.


I run a 26" panhard behind.

[This message has been edited by dirtracer14 (edited July 26, 2002).]

dluna
Member
posted July 29, 2002 10:24 AM
Just to let you all know...I spoke with Dirtworks this Satruday and they informed me that, the tire that is the coolest when you come in is doing the most work. I was thinking about the tires being hooked together. The LR COULD be getting traction and the RR could NOT, so spinning instead, right???. To me, this would seem to make the car want to turn right. Just an FYI to anybody that cares.

28,
I am still no expert on panhard bars, even though I have tried 3 different ones. With the shorty, the car got great initial bite, but is very sensitive to any kind of bumps. We run the J-Bar the most. Sounds like you could possibly do the following. Put more angle in the J-Bar for side bite like you have tried, but also try a stiffer RR spring to keep the car from laying on the RR through the whole turn. As for as the long bar behind the rear-end. Since dry-slick is pretty much like ashpalt, that is why we decided to try it. We run ours pretty much level and it seems to hook up on the dry if we have about 60% rear in the car. Not much help I know, just giving you our experience w/ them.


28
Member
posted July 29, 2002 12:14 PM
Dluna....friction causes heat. The friction between the ground and the tire are what makes a tire hot. The more force(weight) on a tire, the hotter that tire will become. Your target on the rear of the car is to get the tire temps relatively close in temperature, which basically says that the the weight is distributed equally between the tires. As far as Dirtworks, maybe they need a new counter person if they are misleading people like that.(Happens all the time). As far as the spring location goes, I completely disagree with putting springs on top of the rear end. You are losing too much weight movement capability when you do this. Some will disagree, and it will make the car a static setup if you do, but I personally feel like I should use everything possible on a car to make it go faster.

As far as the panhard bar goes....this will actually depend on the track you are running. When you go into the turns, the lateral force on the specific locations on the rear end will make the car do different things and make it act as it has more weight on it than it does statically.

My two cents.

jammin


dluna
Member
posted July 29, 2002 03:33 PM
Thanks Jammin.

I agree w/ you about the DW comment. We purchase their car, they want their cars up front, they should give us correct information! We had thoughts about running RR bite possibly this past weekend and called DW to get their opinion...we had to practically beat any comments out of them.

The tire/heat issue...well I have changed my belief back and forth 100 times . Your logic seems correct now that you explain it that way. I just felt that when a tire spins...it has to get hotter than if a tire was not spinning. BUT, the SIMPLE fact that the tires are indeed hooked together, your logic must be correct.

On the panhard bars...I am just as lost as most people on that. It would be nice to have a site, or somebody to post a thread, explaining how each bar differs, etc.

28
Member
posted July 29, 2002 04:19 PM
We put in a stiffer right rear spring and driver said the car didnt really feel a lot different so we raised the jbar 1" on bothe ends and put 20 more LR bite in it. He said this felt a little better but still not much drive off corner. A friend of ours told us that according to some tire secrets book you want no more than 15 degrees difference between lr and rr tires. We had about 40 and according to the book we needed more cross. Cranked in about 50#LR for the feature (total of 100) and he said it was a little better but still not there. Tires were only 20degrees different so maybe this is astep in the right direction. Maybe we need 150LR. Beginning to think we are transfering too much weight to the RR and may try raising the Jbar again to try and keep more weight on the left rear to drive out.

any ides????


28
Member
posted July 29, 2002 07:46 PM
I am having the same type of problem. we have been told to move the pull bar over to the right some on the rear end to get the right rear to bite more and take out the throttle push.


cd2
Member
posted August 04, 2002 12:15 AM
We run a three link car on a high banked 3/8 dirt track. This track will run dry slick.Too get the car where it hooked up real good from center out we had to run L.F 100# stiffer than R.F.Also L.R. is 75 # stiffer than R.R.The L.R. has 250# more weight on it or bite.Driver said car will set better going in and will pull the wrinkles out of his eye's getting off.When i checked temp. on tires both rear and R.F. were with in 6 degrease of each other and L.F.ran 8 degrease cooler. The hotter a tire is the more it is sliding.On a tackey track we run the pull bar in the center. When on dry we move it 2-3" to the left. cd2


PEDDLER
Member
posted August 04, 2002 11:09 AM
I agree with Jammin, except, If one doesn't understand the workings of some of the suspension systems out today, a simple static two link with a pull bar, long panhard bar behind the rear and springs mounted on top of the rear will make a person faster just because he is comfortable and the lack of infintesable adjustments he has to worry about.