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|Subject: Review #2 - "Getting a Handle on Handling" Page 1 Next Last |
|Gus||Posted on 3/27/2002 12:49:25 AM|
(Click here to read the article review)
Help me out racers! Can these apparent contradictions be explained? I'm anxious to hear your replies to my review. Or if you have additional questions, ask away, and we'll try to get some answers for everyone.
|SLEEPY GOMEZ||Posted on 3/28/2002 11:56:05 PM|
Hi Gus, With all due respect to Steve Smith, after all his were the first and only books for years, some parts of his books tend to be dyslexic. In simple terms more right front weight and more cross weight mean the same thing. When you jack in right front weight you are also adding left rear weight. Weight can only be adjusted diagonally across the car unless components are moved. More right front weight is an easy tool to cure a push going in. Other things can affect the push or lack of it but the weight jack is the easiest and most effective. In those classes where weight jacks are not permitted, adjust cross weight (more right front) with left front tire size. It works just like the weight jack except it messes up the a-frame angles. Cross weight is much more important. Hope this helps, SLEEPY
|Gus||Posted on 3/29/2002 12:15:25 AM|
Wow! Talk about straight from the horse's mouth! I sure wasn't expecting to get input directly from the source of the article! Thanks for your contribution, Sleepy!
How 'bout the rest of ya out there? I know you are all busy getting your cars ready for the season and all, but take a break and put in your two cents to help out a poor, confused mechanic (and I use that term loosely!).
Or maybe some of you have more questions Sleepy could address while we've got his attention??
The Rookie Wrencher
|TAZ||Posted on 3/29/2002 8:20:06 PM|
I always wondered about the weight on the front corners (Late Model) Many I have asked said dont worry about it. So if thats the case then cross dosent matter. But accordingly to Sleepy is does matter. Thus the front corners are very important. So how about some input on this subject. Which is also related to the subject at hand!
|proam88||Posted on 3/30/2002 11:16:30 AM|
Gus, I'm kinda with you. I have always thought that when the car is tight you remove cross. But what we are really speaking of is the cars condition on corner entry. This means the the weight is being transferd forward. My guess is if you break it down to entry-mid-exit you are talking about three different condiditons. If you simply look at entry, Sleepy is right. IF the car is not turning you need more weight on the front of the car. But when you add cross you also add what I call bite. This is the difference of the weight between the left rear and the right rear. The added cross will result in added bite and create a push on acceleration. So the trick is....Adjust the cross for corner entry and then adjust the bite in the car so it won't create push in the middle of the corner when you are picking up the throttle. If you look at a corner in three different sections Sleepy's adjustment is dead on. Just remember to remove some of the bite you added and you should be fine. Of course, thats just my opinion...I could be wrong!
Brian Scott LLM #88
Edited on: 3/30/2002 11:24:20 AM
|Rusty Nutz||Posted on 3/30/2002 12:31:58 PM|
But how do you both add bite and remove it???
Where's the WD-40?
|proam88||Posted on 3/30/2002 1:14:27 PM|
Rusty, That question is exactly why I don't win vey much! JK. I think you would have to adjust both using scales and not only adjusting the weight jack but also moving ballast around. That way you could get the cross and the bite where you would want it. But I have another question.....I thought that an entry push can be caused by a RF spring that is too stiff and not allowing the weight to transefer forward. This is the old "stiffest part skates first" deal we have all heard about. With this being the case wouldn't putting even more weight on the RF worsen the situation? The only cure would be to put a softer spring on the RF. I have really gotten myself confused(which is very easy to do)and now am not sure of the right answer. Somebody help!!!!!!!
Edited on: 3/30/2002 1:16:44 PM
|proam88||Posted on 3/30/2002 1:25:37 PM|
OK so it's slow at work today! I went back and reread The question. Sleepy stated that "with the rest of the suspension being close to right.....So if the spring rates are correct Sleepy's response would be right. The problem I see is most of the time when we have a push in out dirt cars it's due more to a too stiff of spring or too much cross not allowing the chassis to transfer weight to the RF. Sleepy's fix would actually worsen this condidtion. Am I on the right track now?
|Gus||Posted on 3/30/2002 4:15:35 PM|
Hmmmm... interesting points! One thing that I seem to hear differing answers on when I ask different racers is this whole issue with how changing spring rates will affect the weight transfer. We touched on this on my first review of Doug Gore's article in Speedway Illustrated (click here to read it). Doug states that the more you stiffen a particular spring (right front for example), that causes more weight to transfer to that corner during cornering. But then I hear almost the opposite explanation from other racers I have talked with at the track, like PA88 brought up above about "too stiff of spring not allowing the chassis to transfer weight to it". So which is it? Does a stiffer spring cause more weight to be transferred to that corner or less?
|proam88||Posted on 3/30/2002 4:49:05 PM|
Man! I'm so confused!
|SLEEPY GOMEZ||Posted on 3/30/2002 5:58:11 PM|
Hey guys, let me have another shot at this. I know I don't have all the answers butI have probably made all the mistakes at one time or another. I do what i can to learn from them.
You're right about dividing the corner into segments. When speaking of push, loose, tight or whatever we have to be talking about the same spot on the track.
Putting a stiffer spring on the right front will keep weight from transfering to the right front. Conversly, a softer spring on the right front will allow more weight to transfer to the right front on corner entry. I can understand how one can get confused by all this, I spent many years confused.
The point when a softer spring stops weight from being transferred is when the suspension on that corner bottoms out. I spent a couple of seasons with this problem before figuring it out.
The car must turn in on corner entry. That sets everything for the rest of the corner. Fix that first and then work on the exit.
Now, lets go to another part of this discussion. First the car must turn upon corner entry. Use the correct spring (should allow 3 -4" bump travel) and jack in enough cross weight to achieve this.
On corner exit cross weight has a minimal effect. Stagger is the best and most efficient way to control corner exit. With too little stagger the car will push on exit, Offset wheels can help also. Pulling the wheel in on the right rear will tighten the car on exit. Setting it further out will tend to loosen the car on exit. Go softer on the right rear spring so that the weight shifts to the right rear quicker. Most of the time the left rear spring will be stiffer than the right rear for this reason. This loosens the car on exit.
I hope this gives you something to work with and helps out a little. SLEEPY
|proam88||Posted on 3/31/2002 1:08:14 AM|
Thanks Sleepy, See we were all heading the same direction, just taking different pathes!
Brian Scott LLM#88
|Double K||Posted on 4/1/2002 3:36:51 PM|
Maybe something we need to consider when dealing with the right front spring is this theory. And I'M SORT OF ASKING A QUESTION HERE! LOL
Let me use the right front shock as an example to get to my question. I was under the understanding that a stiffer compression right front shock actually tightens up corner entry. Now on the opposite corner, LR, you use a lighter extension shock to transfer that weight to the RF quicker. The theory further being that the stiffer front shock plant more weight to the ground. Imagine if instead of using a shock, you used a solid piece of steel. That RF would plant extremely hard then!!!!
Using that philosophy, wouldn't it be safe to say that the rear springs really don't do anything for you for weight transfer on corner entry. In other words, when you decelerate or brake, the weight just goes due to the spring wanted to rebound all the time. So, if you have a light RF spring, wouldn't the spring just simply compress and absorb the transfer of weight, or would a stiffer RF spring theoretically "plant" more weight to the ground. In other words, the weight of the car transfers onto the RF spring, and due to the springs stiffness, it transfers more weight to the ground/tire??? The reason I ask this is because if you take a set up, say with a 1300 lbs RF spring. Then change it out with a 1400 lb spring without changing anything else, your crossweight is going to go up, obviously. So isn't it safe to say that a stiffer front spring will plant more weight to the ground when you throw or transfer that weight upon it going into the turns?
Maybe we're saying the same thing again, like 88 said, but I thought someone above said stiffer front RF would keep the weight transfer more minimal?
Just pondering these things. Let me know what you guys think?
Edited on: 4/1/2002 3:39:45 PM
|proam88||Posted on 4/1/2002 6:23:50 PM|
My guess is that a stiffer RF spring will increase static weight on the RF and increase the cross also. It actually DECREASES the amount of weight that is dynamicly transfered. All else being the same the upward force of the LR spring is not enough to over-come the upward force of the RF spring thus no weight transfer will take place. So in the long run even though you start with more weight on the RF you will actually lose weight during corner entry because the RF will no longer GAIN any weight during cornering. Makes sense to me...but I could be wrong!!!
|racer31x||Posted on 4/1/2002 6:59:38 PM|
Great discussion, glad to see Gus finally getting some feedback! A few points I wanted throw in, first regarding KK's theory that a stiffer shock plant's more weight to the ground, is that a shock doesn't effect how much weight is transfered, it only effects the speed of the weight transfer. A stiffer right front shock could possibly tighten a car going into a corner, if the shock it replaced was too soft on compression and allowed the weight to transfer to the tire too quickly and sheared the tire's contact patch. From my experience, generally a softer right front spring tends to cure a push, as long as you don't go too soft(which can be determined by shock travel). In most cases also, a stiffer right front spring won't increase static crossweight, since you should reset the ride heights when changing a spring(I realize in KK's theoretical example he said "adding a stiffer spring with no other changes"). I'm not sure on this, but I think that weight transfer is mainly due to the actual dynamic forces working on the mass of the vehicle much more than any opposing force caused by the spring at the wheel opposite of the direction of force. The speed at which that weight transfers is controlled by the shocks though. I'm going to have to dig into my pages and pages of notes I took at the Larry Shaw/AFCO clinic this winter and see what they had to say about this subject. They went through so much info that it's hard to remember off the top of my head, but this subject was well-covered. One thing I do happen to remember though is on the subject of stagger(which happens to contradict slightly with what Sleepy said in an above post), is that stagger mainly has an effect in the middle of a corner, as opposed to exit. I'm sure it does affect exit and other points in the corner somewhat however.
Edited on: 4/1/2002 7:02:36 PM
|Double K||Posted on 4/1/2002 9:23:17 PM|
I stand a little bit corrected . You're right, I used the wrong terminology. The shocks do indeed affect the rate at which weight is transfered, and not the amount of weight, that is true.
But, I still read and went by the theory that a stiffer front shock (compression side) would "push" harder down on the RF because of it's resistance to the inertia of the forward moving weight transfer. Therefore, pushing down or loading the RF tire. Like I said before, imagine a solid bar mounted instead of the shock and the amount of force that would be planted at the RF.
31x, I'm with you, I'd have to do some diggin'. Been awhile since I stuck my nose in a chassis book.
I think Gus has kinda got us on this one, and the jury's still out to a certain degree.
"I was NASCAR.....when NASCAR wasn't cool!!!
|SLEEPY GOMEZ||Posted on 4/1/2002 11:02:13 PM|
Hey guys, The "stiffer" shock will act like a stiffer spring as it affects weight transfer. Yes, the spring controls the amount and the shock controls the speed of weight transfer. The softer spring will let more weight transfer to it and a softer shock will let it happen quicker. Get the right spring to control the amount then fine tune with a shock to have it happen at the right time. Always when changing spring combinations watch the bump travel. Ideal is probably close to 4". Make sure NOTHING in the suspension is bottoming out. It took me a whole season to learn that one. SLEEPY
|proam88||Posted on 4/1/2002 11:47:15 PM|
I agree that shocks only control the compression or rebound rate on the spring. Fine tuning on the "when" of these adjustments is a big help. Sleepy and Racer31x is right on that. Installing a softer RF spring to cure a push is the correct but now we create a different set of problems. Now the softer RF will not push back as quick as a stiff spring. When the car is accelerated in the middle of the corner weight may not transfer to the rear as quickly. This may cause the car to go into the corner right but be very loose in the middle and the exit. One way(I learned this from KK) is to speed the weight transfer with a split valve shock. The split valve will slow the transfer to the RF when going in(hard compression,thus making th car loose on entry)and speed the transfer to the rear when on the throttle(soft rebound thus making the car tighten up on middle and exit). It's a fine tuning adjustment and will not work if the springs or not right for the car or track. I also agree the watching your shock travel is VERY important. Not enough may mean you need a lighter spring. Too much and you may need a heavier spring. It's a great gauge on what the chassis is doing. Always check and make sure that the suspension is not binding anywhere in it's full travel. This will give you false shock travel reading and cause you to make the wrong changes. Remove springs and excersise the suspension fully to check for binds. Sorry for the rant but this is just getting good.
|STOCK64||Posted on 4/2/2002 9:00:28 AM|
wow, this is some good stuff, we need more of this type of discussions... hope you don't mind if i drop a few things... i drive a imca stockcar, small 3/8 semi banked track.. anyway... i ve been to two seminars, and at both were talking about swopping the front springs around w/ no more than 100# split...they said this would help on entry, and exit...i was having a big problem w/ being extremly loose on exit. so this last year we changed them. 1200#LF,1100#RF(no sway bar). that was a night and day difference... then went to bilstein split valve shocks... wow...LF:50/50; RF:30r/60c; LR:50r/30c (or) 70r/30c(dryslick); RR:45r/55c... correct me if im wrong but what this allowed me to do was go into the corner, the soft spring let the car roll over, but w/ a 60 on compression RF and a 50 or 70 rebound on LR, slowed it down so it wasn't just dumping it on the RF. Then once i was back on the throttle the RF 30 rebound and LR 30 compression allowed the car to transfer the front weight to the LR easily, planting the LR.
if the car was a little to loose b/c i threw the car too much or i got bumped in the corner, i found if i throttled the car it would pull it straight..... great right...well the new problem was at mid-corner. the setup allowed me to get on the throttle sooner (at the apex) but there the car was hooked up to tight and would drive me to the wall. not good. i had to wait to after the apex to get back on the gas. so we started taking cross out of the car... started w/ 53%. we found that about 50.5-51% help that, but also a little less rear about 52% and higher ride heights to get the car do rollover, and it did....
Maybe im way off base but it seemed to help...alot... i know people say some of these things are crutches for the real problems... i don't know... i think what i was doing kind of supports pa88's ideas...thanks
WINNING ISN'T EVERYTHING, WANTING TO IS!!!
|Double K||Posted on 4/2/2002 9:24:47 AM|
I'm thinking instead of changing the cross, which don't get me wrong, might of been the right way to go, especially if it feels right driving it.
But you may have wanted to mess with you shocks a little more to slow down the weight transfer from RF to LR under acceleration. For instance, you said you had a 30c LR shock and a 30r on the RF. That may have caused too fast of a transfer.
Just a thought, but it sounds like you're on the right track. Experimentation, and not being afraid to try new stuff as long as it's smart decisions are the way to go.
I like what you said about raising the car up. Too many guys I see, especially newbies, lower the car. On dirt, that can be a very bad thing. I know on the Camaro's, you lower too much, and you're bottoming the suspension.
IMO, the guy who figures out tires and shocks, is going somewhere.
Edited on: 4/2/2002 10:02:13 AM
|STOCK64||Posted on 4/2/2002 10:09:52 AM|
Thanks, yea that probably would of helped i never thought of that... i was just obsessed w/ planting that LR tire to get off the corner... year it might have been to fast...so do i do both the shock or just one... im thinking maybe raise the rebound on the RF a little allowing the LR to still compress fast once the car is straight and the RF will control more of the weight transfer in the middle of the corner... not sure...what do you think? what was your opinion swopping the front springs..??? good/bad?? thanks...
WINNING ISN'T EVERYTHING, WANTING TO IS!!!
|racer31x||Posted on 4/2/2002 10:16:46 AM|
This is good! After a winter of cleaning parts, assembling parts, bending body panels, etc., it's finally time to start thinking about the fun stuff!(of course it's ALL fun!)
I agree with KK's statement that maybe the combination of split valve shocks at both rf and lr on stockcar64's situation may have allowed weight to transfer a bit too fast. But, since he adjusted crossweight and it worked, that's great- and adjusting crossweight is cheaper than experimenting with shocks. Another minor point I'll throw in here is that the chassis seminar I went to never once mentioned crossweight- they only mentioned wedge- the difference in weight between the rear tires. Of course wedge does affect crossweight. Stockcar64 in saying that if he went in too hard or got crossed up some other way that caused him to get loose, brought a couple other somewhat related things to mind. First is caster in the front end. Putting more caster in the rf causes weight to transfer to the lr when you backsteer in a loose conditon, which will help tighten a car back up. And caster split(less on lf than rf) will help a car turn in, so it is important. The second thing is something they talked about in the school, which is the importance of the corner entry. Getting entry right will affect the rest of the turn. It's easy to get confused on this because most drivers will fool themselves by pitching a car in too hard when the car is too tight on entry making them think it's actually loose. On stockcar64's problem of throttle push in the middle of the corner, I had that problem last year as well, and that's where the theory of stagger helping in the middle of the corner comes in. I don't know what their tire rules are, but if he can get more stagger in the rear it will help eliminate the throttle push. Well, I've been rambling again-so much to talk about, so little space! NEXT.....
|BEEK||Posted on 4/2/2002 11:17:21 AM|
Good stuff guys. If Stockcar 64 is running a metric based car he my have a problem getting the caster that racer31x mentioned. And can you say BUmP steer!! These cars don't work right with a low ride height.
|proam88||Posted on 4/2/2002 11:28:08 AM|
I with everybody else. I think the split valve on the LR might have been to much. But what if the car is going in fine you might not be that far off. On S64 situation, the car goes into a push on throttle up. This tells me he has either too much stagger or too much bite(wedge) in the car. If you could keep all your rates and percentages close and dercrease the bite across the rear it should loosen the car up in the middle. Adjusting the cross is doing just that but not as great as moving some ballast around. See if you can move ballast and keep your cross where you have it and lower the bite and it should work better for you. What do ya think guys....Are we going the right way?
Brian Scott LLM#88
|STOCK64||Posted on 4/2/2002 11:43:57 AM|
GREAT STUFF GUYS KEEP IT COMING... I CAN USE ALL THE ADVICE I CAN GET.. yes, it is a metric car...85 monte carlo. i just sold my last years car but just bought a destroyer chassis from texas.. they've been doing some work w/ the front end geometry to help w/ the bumpsteer, ect.. not sure exactly yet...suppost to go get it in a couple weeks.
anyway back to the shock... the reason i had split shock on the RF and LR was at all the seminars i attended they were saying to get the shock to work together....granted i might have went to far w/ 30c and 30r, but the track i race on has
really tight corners, and you scrub off so much speed that getting off the corner is the key to passing and winning... so thats why i tried what i did...to get the weight to transfer quickly and with out spinning the tires....
anyway keep them coming.... thanks.
WINNING ISN'T EVERYTHING, WANTING TO IS!!!
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