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Author Topic:   To be or not to be Clamped Up?
Mastersbilt05
Dirt Roller

Total posts: 21
posted May 18, 2005 06:31 PM  
I recently attended a 3 day race in fayetteville, ark. It seemed like everyone that was fast was clamped up on the lr. I just got a clamp bracket that I am going to try on my dirtworks 4 link. I am not changing anything except putting a clamp bracket on the lr everything else is going to stay 4link. What has been your experience with this on a short slick racetrack?

Ego Racing
Dirt Forum Champ
Total posts: 724
posted May 18, 2005 07:21 PM  
It hooks the car up under power. You will need a spring about #25lbs stiffer as you loose the indexing of the birdcage.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted May 18, 2005 07:36 PM  
We found the car to be a lot tighter in the middle on the gas, compared to spring behind. Last year we had the car clamped and fought it being tight all the time, with sprign behind car is a lot freer and havent had to fight the tightness any yet.

just our experience though...

rocket36
Dirt Freak

Total posts: 209
posted May 19, 2005 04:33 AM  
we have run it some on our late model but have tended to move away from it. personally i found it quite hard to drive consistantly because it can be quite aggressive on the throttle. we tended to run a slightly softer spring to try and smooth the reaction out a little and also ran longer on the lift-arm.
it is a good setup if you feel comfortable running it, but i'm not sure it would be too good on a dry slick track that you mentioned. normally there needs to be some traction in the track so that the lr tire has something to get hold of when you hit the throttle. if you see some dust coming off the track, i'd take it off the clamp and put it back behind.
running the clamp you will also run less wedge and you will likely find it to be quite sensitive to wedge changes. likely run less left rear upper bar angle too.
make sure you got a 9/1 axle damper on the rear end too.
if the track is real tacky or has rubber and if you've got some horsepower - HOLD ON

STICK01
Dirt Maniac

Total posts: 164
posted May 20, 2005 07:37 AM  
If the race you attended had the mods on the AR G-60 tires I have been told that the only way to get really good FWD bite out of that hard tire is to clamp it up and gas it!

I did this to my mod on Hoosiers this weekend and it was the tightest car I have ever driven in the black slick...it still wanted to push! But was very driveable and even easy to move around. It was a handfull early on in the night, as I could not get enough RPM's out of the car to turn it!

My 2 cents.

STICK

zeroracing
Dirt Forum Champ
Total posts: 1875
posted May 20, 2005 10:45 AM  
I am a firm believer in spring floated behind. clamped up has its place, like tacky tracks. but on slick it can led to inconsitant handling, also if you take two cars with good drivers, but one car with spring in front clamped the other spring behind floated... the clamped car maybe faster to begin with but come lap 15-20 the spring behind car will start coming on strong. it is very consitant, and easy on the tires.
if you look at it from a physics standpoint, my choice is always spring behind.


Kromulous
Dirt Forum Champ
Total posts: 796
posted May 20, 2005 11:58 AM  
I always wanted to try spring clamped up front LR, never have. To me it seems very dependent on the pull bar, aka if it doesnt travel enough, you dont get the mechanical bite via the LR spring being compressed due to axle wrap.

As well very dependent on chassis roll, if you go in to fast and the car rolls over bad technicly speaking you should have less bite available.

Seems to me that the LR clamped would be very sensitive to how you drive and have the car set up, but i've seen guys fly with them like this.

[This message has been edited by Kromulous (edited May 20, 2005).]

rpm20
Dirt Freak

Total posts: 338
posted May 20, 2005 12:35 PM  
i tried clamped up in front on the left side of my dw8 and i didnt like it, it was tight and pushy. i moved to bc behind witha coilover and the whole car freed up through the entire corner and the control comes from the gas pedal which works for me in all track conditions. swweeeeet !!!

Larry Lundin
Dirt Full Roller

Total posts: 45
posted May 23, 2005 04:42 PM  
All of this is very interesting to me and I'll throw my 2 cents in for whatever its worth. I have a GRT that came with rayburn style swing arm suspension. I ran the car using various set-ups including a 1050lbs AFCO pull bar. After numerous outtings to several different tracks, I had no success with this particular set-up even though others were having some success. After being frustrated with a mid-turn push which led to being loose off, I went old school. I clamped the LR, installed a 225lbs spring and mounted the shock behind with the spring still mounted on the swingarm. I clamped the RR as well, dropped the spring removed the swing arm in favor of a straight link and mounted a 200lbs spring on top of the housing. I also mounted the shock to the rear. I canned the 1050 pull bar spring for an 800 and added 100lbs of ballast to the RR rear, put some gear in the car and what a difference!! Pull bar travel is right around 2" using a 90/10 shock as well. This car is now bad fast using very smooth throttle control especially when the track slicks up and gets black, its also very easy to drive while tacky!! Why any of this works? I'm not sure but like the other guy said...Clamp it, Gas it and go!!

Kromulous
Dirt Forum Champ
Total posts: 796
posted May 24, 2005 07:38 AM  
So you went to a 2 link swing arm LR, 2 link RR set up. When you say clamped, and the spring is still on the arm, you must of clamped the BC to the axle and removed the top z link i guess.

Mark Noble, Jack Sulivan and some others are always fast and they are pretty exclusive on what they run, 2 links / swing arms.

Larry Lundin
Dirt Full Roller

Total posts: 45
posted May 25, 2005 09:10 AM  
Yes, thats exactly what I did. The LR spring is still mounted on the lower swing arm and I removed the upper link and clamped the bracket to the housing. I placed the shock to the rear of the BC bracket by welding a new mount behind the BC bracket. On the right side, I took a upper spring plAte that has the large diameter slider groove in it, and placed it over the top of the BC bracket and tack welded it. The spring now sits on top of this bracket directly over the upper mount that use to connect the upper link. I then clamped this bracket as well with the spring on top of the housing. I also moved the shock to the rear just like the left side. I have the option of unclamping either side and reinstalling the original swing arm set-up but the car is so fast, I don't see going back to that any time in the near future. I live in Pleasanton California and have run the car twice in this configuration with geat success on slightly banked dry tracks as well as very tacky hooked up tracks without changing anything on the car besides J-bar angle and stagger. I might also point out that this car (GRT) is very sensitive to the location of the rear end. The car had a tendency to lose a little grip at the mid straightaway point. I put 1/2" lead in the right rear and this seemed to help quite a bit. I'm going to back some gear ratio out of it and I think that will help to totally eliminate this slight irratation which hasn't really hurt me. I also run the biscuit type J-bar down in the bottom hole on the pinion bracket and at 6" on the frame side. Not alot of angle here. When its tacky, I move it up 2 holes and a corresponding amount on the frame side. I've read lots of comments regarding J-bar angle and panhard bar angle on dry tracks but I think alot of guys miss the point regarding roll center. A bunch of bar angle RAISES the roll center and greatly INCREASES lateral force on the RR contact patch. I believe this is more detremental to DRY SLICK handling than any benefit gained by high amounts of bar angle. It can be of benefit on a wet or hooked up track but I've noticed alot of cars on dry slick tracks with gobs of bar angle. Guess it looks cool lifting the front wheel but I just shake my head when I go by them!! Having said all that, ultimately it comes down to what works for the driver and his car. I have found that this set-up works for me and my GRT metric car on either a tacky track or one that has slicked over.

bachshute
Dirt Maniac

Total posts: 118
posted May 25, 2005 07:57 PM  
Larry Lundin
I am about to try the same thing , cant believe i found this post , i am currently running swing arm on both sides but have it clamoed on the LR , just made my bracket to clamp RR ,
My question is , Will i need a lot more stagger to get the car to turn ? also do i need to trail the RR ? Any other info you suggest ? Thanks for any help

Larry Lundin
Dirt Full Roller

Total posts: 45
posted May 26, 2005 10:40 AM  
I run no stagger when the track is dry and I have tried 1/2 lead in the RR which seemed to correct a mid straight away loose condition. I run the rear end straight up when the track is tacky with about an 1 and 1/2 inches of stagger. My car turns in very good and I can usually get a nose under guys on initial entry, after that its all driver. I have not tried trailing the RR but its something to maybe play with during a heat race. Funny thing about this set-up, is that the car is equally as fast through the corners under wet or tacky conditions. Where it really performs though is on the smooth hard surface or slicked over track. Remember the added ballast I mentioned, J-bar location and gearing. I can't emphasize enough to be smooth with the throttle application and adjust your throttle linkage to provide the longest amount of travel you can get out of it. In other word, drop the throttle link rod down where it bolts to your pedal arm. This will help you keep the car hooked up on corner exit if the track is slick with a minimal amount of traction, Good Luck!!

doghouse racing4
Dirt Forum Racer

Total posts: 91
posted May 26, 2005 12:41 PM  
Larry..........what is the length of your lower trailing arms? LR and RR the same length? What angles are you running them? What is your cross and LR bite? Sounds interesting... Have you ever tried the RR behind instead of on top?

Larry Lundin
Dirt Full Roller

Total posts: 45
posted May 26, 2005 02:10 PM  
Both arms are 15" in length and in the #2 hole which would place them in about a 6 degree angle uphill. Cross is about 50.7 to 51%. I've run the car twice like this and still working on some fine tuning with shocks and roll centers. I want to max out this particular set-up before trying anything else. 15" arms are the standard GRT metric swing-arm lenghts. I use a straight arm on the RR to make adjusting lead/trail at the track easier.

bachshute
Dirt Maniac

Total posts: 118
posted May 30, 2005 08:18 PM  
Larry
I tried this set up on a very slick track this past weekend , i still lacked forward bite but the car was better .

i think maybe i should have changed the spring rates , could you tell what springs you would recomend - front and rear , my clip is metric also .

This car has 17 inch lower arms and my rr spring is mounted to the front of BC

I really like the feel this set-up had but i think i need to go a little further with it -- thanks for any help


WPP
Dirt Freak

Total posts: 451
posted May 31, 2005 03:53 AM  
What spring rate was you running what pullbar was you running

bachshute
Dirt Maniac

Total posts: 118
posted May 31, 2005 05:10 AM  
My spring rates were LF-900 RF-1000
LR-325 on the arm RR-225 on the front of BC .
I run the biscut bar with new rubbers.
Thanks

Larry Lundin
Dirt Full Roller

Total posts: 45
posted May 31, 2005 09:39 AM  
Bachshute, I run a 225 on the LR swing-arm and a 175 on the RR mounted on top of the housing. I run an 800lbs. AFCO pull bar which produces 2" of travel. Make sure you run a good 90/10 shock with that soft of a pull bar spring. I use 900's across the front for springs. I also use easy up shocks on the front to help facilitate weight transfer to the rear wheels on corner exit. Remember roll center heights! I keep my down low so the car transfers weight to the RR quicker. Not alot of angle, just a lower roll center. If your track is smooth enough, soften up your car and give it another go!!

Larry Lundin
Dirt Full Roller

Total posts: 45
posted May 31, 2005 10:03 AM  
Further Bachshute, after reading your comments, it occured to me that your car may not be 2-linked like mine now is. If it is, your springs are way too stiff in the rear and it sounds like the rates you are using are typical for the swing-arm/Z-link set-up.

bachshute
Dirt Maniac

Total posts: 118
posted May 31, 2005 02:43 PM  
Larry
Yea , your right , i run the typical swing arm z-link set-up - this set-up works good when there is a little bite in the track - then if the track slicked over a little i would clamp the LR BC. and leave the same springs on the car , it worked good enough to run top 3 most of the time , BUT , lately our track has been very very slick so i tried clamping both birdcages , like i said earlier , the car was better but still lacked forward bite , ( i am thinking because of the stiff springs ) I will try it again with the softer springs if the track slicks over again ,
Another question - Would i be better to put the spring on the arm on the RR when clamping both sides ? Thanks for all the help .

Larry Lundin
Dirt Full Roller

Total posts: 45
posted May 31, 2005 04:27 PM  
I haven't tried that because I like to make rear end lead/trail adjustments on the RR so I put the spring on top and replaced the swing arm with a straight link. You can also use a lighter spring by mounting anywhere off the swing-arm which I beleive is key to making this set-up work on a dry slick track. You'll have to stay with the springs you have if they are mounted on the swing arms but I'm down to a 225 on the LR although its still mounted on the swingarm. had another good run this week at a different track (2nd) with this set-up. Like all different set-ups, give it a fair chance, mine still performs well even when the track is tacky or heavy but I move the J-bar up a good 2 and 1/2 inches during that type of track condition.

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