New M/T Drag Radials = Major Wheel hop.

[thehueypilot]

I installed new drag radials and my 60' went from 1.68 to 1.63. Everything was great until the wheel hopping started without warning. Here is my question: On a hard launch on leaf springs which way does the rear pinion move (axle housing twist), up or down? Is it action/reaction where the pinion moves opposite of the tire direction? I have under rider traction bars that are adjustable so do I push the pinion down or up to restrict leaf spring twisting?

 

[raeandy]

Action/Reaction - When you launch the rear tires, axles, and ring gear are initially stationary. As power is applied and the pinion starts to transmit power to the ring gear it tends to want to climb the ring gear. This causes the rear axle housing to rotate up and towards the back of the car causing the leaf spings to distort and creating driveshaft/u-joint misalignment. Eventually the spings "wrap-up" enough that they overcome the torque applied by the pinion and un-wrap causing wheel-hop. This pattern continues as power remains applied. The torque also tends to shift weight onto the rear left tire so the wheel hop effect is not equal on both sides. As a result for straight-line purposes you will likely have your traction bars adjusted differently. Hope this helps.

 

[iskwezm]

have you checked your pinion angle????

 

[12sec67]

what kind of suspension mods do you have to get those 60' times with drag radials.

my suspension is pretty stock and not really set up for drag but i can pull high 1.80's with et streets but your and 10secgoals 60' foots are really impressive!!

 

[302 coupe]

I've never seen adjustable underriders, could you post a pic? If they mount like the regular underriders, it may just be the floorboards deflecting, especially when you're cutting 1.6x 60 foots. I used to run the normal underriders when my car was a daily driver, but lately I've been building it into more of a racer. I switched from the underriders to Cal-Tracs and immediately noticed a huge difference. That makes me question the efficiency of the underiders and their design....

With that being said, whatever you have seems to be working pretty good. I'd add in some preload (move the pinion down) and see how it reacts.

 

[thehueypilot]

what kind of suspension mods do you have to get those 60' times with drag radials.

my suspension is pretty stock and not really set up for drag but i can pull high 1.80's with et streets but your and 10secgoals 60' foots are really impressive!!

I think the stroker motor has a lot to do with it, but I have a 9" Currie with 4.11 gears and a Detroit Locker and TCP sub-frame connectors. The under rider traction bars are now adjustable but I having trouble getting them adjusted correctly (no wheel hop). I just installed KYB gas shocks which helped a little. I am getting new leaf springs (Magna) with the 4 1/2 leafs to eliminate wheel hop. The M/T drag radials worked very well until the hopping started.

 

[iskwezm]

Arent the KYB's too stiff?

 

[302 coupe]

they're just right for my setup, for the rear that is. Most "drag shocks" allow the rear to squat too much, which is just a waste of energy. Drag shocks are good for the front though.....

 

[thehueypilot]

Here are some pics of my adjustable under rider traction bars. I have found that the better your 60' times the closer you can get to a perfect .500 reaction time. Of course consistent dial in times help as well. When I put the new M/T drag radials on I made it down to 6 cars and some money which had not happened yet this year. The wheel hop started the next days race and my reaction time and consistency disappeared. The KYB's do not ride rough but were a pain to install because they are a lot stiffer then the GR-2 shocks I replaced.

 

[302 coupe]

Ok, thats kinda how I figured they would look. I'd try more preload and see what that does, then maybe try an air pressure adjustment in the tires.

I think you might start having some stress issues where the front mount of the underriders is welded to the car. Time will tell, keep a close eye on that area for cracks and/or distorted metal. Looks like a nice car from the bottom.

 

[thehueypilot]

Thanks.....I will be removing the stress when I put the new 4 1/2 leaf, leaf springs under it. They are supposed to eliminate traction bars and wheel hop so we will see.

 

[coolblue65]

Thanks.....I will be removing the stress when I put the new 4 1/2 leaf, leaf springs under it. They are supposed to eliminate traction bars and wheel hop so we will see.

When I only had the 4 1/2 leafs, I had horrible axle hop, so I wouldnt count on that fixing your problem. Mine went away after I put on the traction bars (non-adjustable) although granted either way my G-Force KDW tires are no were near as sticky as you drag radial's because all I do is spin now....my 60ft times are like 2.4. Good luck!

 

[mustangdave]

That is one heavy duty setup under there! Is that a rear sway bar inboard of the leaf springs? I wonder what effect it would have removing it for drag racing?

 

[10secgoal]

I don't know how stiff the caltracs are. But my landrums are pretty stiff. I got them from summit. The biggest advantage caltracs have over those is the bellcrank on the caltracs. On Caltracs, when the bar moves forward, it pushes on a triangle, which puts pressure on the weak part of the leafspring. this is where the wrap up comes from. I would spend the dough on the caltracs before buying new leafs that may be too stiff for what you want.
I like my drag shocks. KYB's would be nice because they are siff, but not adjustable. And since they are gas charged will tend to throw the ass in the air and unload the tires. I have mine set to 70/30's right now I think, and they work well, and only 27 a peice

 

[thehueypilot]

That is one heavy duty setup under there! Is that a rear sway bar inboard of the leaf springs? I wonder what effect it would have removing it for drag racing?

I ran it all last year without it and installed it this year to limit the rear end sqwat and single tire lifting. The guy I race with bought some Caltracs ($325) and took them back off after about two weeks and sold them for $200. He could not get them adjusted correctly and his 60' suffered. What are landrums?

 

[10secgoal]

The landrums are drag springs for the back. No offense to your friend, but he didn't do something right. Many a stock suspension cars have gone eights and nines with leafs out back. I find it kinda hard he was over powering them if they were setup right. I don't run a sway bar in the front or back. I think your sway bar is some what of a bandaid. The best 60 I have pulled is a 1.52 and she leaves perfectly straight as long as the wheels don't stay up too long. In your second pick, are the back of the leaf spring clamped like that in the back also ? If not that can cause alot of wrap up also.

 

[thehueypilot]

The landrums are drag springs for the back. No offense to your friend, but he didn't do something right. Many a stock suspension cars have gone eights and nines with leafs out back. I find it kinda hard he was over powering them if they were setup right. I don't run a sway bar in the front or back. I think your sway bar is some what of a bandaid. The best 60 I have pulled is a 1.52 and she leaves perfectly straight as long as the wheels don't stay up too long. In your second pick, are the back of the leaf spring clamped like that in the back also ? If not that can cause alot of wrap up also.

I think your right about the Caltracs not being adjusted right, but to his credit he went back to his old set-up which gives him a 1.48 60'. Are you talking about the spring wrap (also know as a Military wrap)? Your saying they should not be clamped tight so the leafs can slide without binding. I will check this.....I did go back to the track last night and the same thing happened, major wheel hop so I put it back on the trailer and got a broke pass for next week. I adjusted the traction bars to give both sides the same amount of pre-load (two turns to lengthen the bars to push the pinion down). I was told that the drivers side should have no preload and the pass side about one turn to lengthen the bar. Does that sound right?

 

[10secgoal]

The adjustments you mentioned are for a starting point. The pass side should have more preload than the drivers. That helps with the twist. The wrap I am talking about is the way the springs actually look when you are launching. If you were able to look at them from the side you would actually see a wave action going on. The front would be bowed up, and the back down. The leafs don't actually slide, but if you keep the leafs from seperating from each other( on the backside), this will help stop the wrap up. And the caltracs keep them from bowing in the front. All yours is basically doing is moving you IC (instant center) forward, which does help with traction, but becomes null and void when wheel hopping starts. PHHT, a broke pass ?!?! Dang, lucky
P.S. If you can, have someone sit in the car when you adjust them. If you so it with no weight in the car, the adjustment will be off. The rear will move backwards when there is weight in the car, removing any preload you thought you had.

 

[thehueypilot]

Good point....... Thanks! My new leafs are here so I will be ready for the weekend to assault the track with some new found traction..........I hope!

 

[thehueypilot]

New rear springs installed, and under rider traction bars adjusted and wheel hop is as bad as ever. Next step is to ditch the under rider traction bars and install "Lakewood" traction bars. Running out of ideas.......suggestions?