BIG wheelhop! Please critique my launch

-
mshred

mshred

The Green Manalishi
Joined
May 2, 2008
Messages
3,255
Reaction score
132
Hey guys,

took the scamp out today for my first pass ever down a dragstrip (probably its first pass ever too)..needless to say i had a blast and with the mild setup i have managed to run a best of 13.6 (mild 360 with a 5 speed stick)...my best mph was 102, which equates to a 13.3, which i know i could have had with better tires and no wheel hop (running on average 13.7-13.9 with a couple 14's in there too)

However, every single launch i made had HUGE wheel hop and lots of tire spin...I took lots of video of my launches as im very concerned about this. The tire spin can be credited to my sportsman tires (even aired down to about 20 lbs didnt make much difference...tires were spinning on the rim slightly as well...running tubes), but the wheel hop is very serious.
Here are some clips...For all the videos i was launching at 3500rpms off the two step...Im thinking my CE 3 ways arent long enough (maybe truck shocks instead), i need a different spring setup (stock 6cyl leafs with one leaf added to each) or my pinion angle is way off (i already know it is, but im wondering if its affecting wheel hop...i think its around 2 degrees nose up...i know, dont ask how)

[ame="http://www.youtube.com/watch?v=75Bx_Bu3T34"]YouTube- 1971 scamp at the strip[/ame]
[ame="http://www.youtube.com/watch?v=iU2tVVCeR1M"]YouTube- First ever pass in the scamp[/ame]
this one is my best pass with the 13.6
[ame="http://www.youtube.com/watch?v=gDn73jb_q5g"]YouTube- 1971 scamp dragstrip pass[/ame]

Im open to all suggestions here! the wheel hop was crazy and id like to fix it so i can get back out to the track...im luck i didnt grenade my t5 or 8-3/4 with this severity

thanks!
Matthew
 
im definatly no expert, but are you dumping your clutch or slipping it till you get good traction?

and it looks like you have ZERO weight transfer, as in the rear doesnt squat. at all.

you say your pinion is 2 deg nose up? are there any sort of spacers between the rear and the springs?
 
Did you add the leafs? It's wrong on the right side... Need more spring. The shocks are not long enough... If you have something now, you may be able to find shock extensions... On the pinion angle... Yes, you NEED to correct it. You are more likely to have wheel hop that way. Do you run a snubber?
 
Like i said in the original post, dumping the clutch at 3500rpm off the two step

As far as squat goes, the body is seperating real good from the rearend it seems, which is what i thought you wanted on a mopar? didnt know/think squat was desirable? not sure which is right though now

As far as rear shocks go, they are competition engineering 3 way adjustables on the stiffest setting...im thinking they are not extending long enough
 
moper said:
Did you add the leafs? It's wrong on the right side... Need more spring. The shocks are not long enough... If you have something now, you may be able to find shock extensions... On the pinion angle... Yes, you NEED to correct it. You are more likely to have wheel hop that way. Do you run a snubber?
Click to expand...

no, i had a spring shop add them...when you mean its wrong on the right side, what do you mean? (sorry if thats dumb)

as far as shocks go, im thinking of just going with the long truck shocks if that will help and shocks are the problem...As far as pinion angle goes, it is going to be corrected this week, car is off the road until then...im sure it has something to do with it, but i dont think its everything

I am also currently running a snubber, about an inch and half away from the floorpan if im not mistaken
 
your are correct that the rear will seperate, you will probably need a stiffer leaf spring, soft springs or soft shock settings will cause a wheel hop, you probably need a superstock leaf spring or a cal trac set up, your et will improve with a new rear set up, your weight transfer looks good in the vid too
 
Yeah it looks like you're running out of shock length, and definitely correct your pinion angle.

As far as springs I would get the mono leafs and cal-tracs from Calvert racing. If you don't want to go with cal-tracs I would at least find a set of springs from a 340 car, worked fine for me into the mid 10s with a 9" tire. You can help them a little with extra clamps in front of the axle and removing all the clamps behind.
 
I mean the right spring isn't right. The car lifts on the left side, kind of tries to squat on the right. SS and Hemi leaves have extra on the right to prevent that. I's remove the extra leaf on the left and add it to the right side. I agree the shocks are not extneding enough. On the "soft" or "hard"... I think setting them on the middle 50/50 IIRC is where they should be. With regard to the snubber... The reason the rear rises is the snubber. You need to first correct the pinion angle (should be 2° "down" relative to the transmission's output shaft angle) at rest with you in the driver's seat and a full load of fuel) Once you've done that and replaced the shocks, then set the snubber to be 1/4-1/2" from the floor.
 
You need to set the rear suspention up alittle differently with a stick car vs. automatic, looks to me 1 or more are happening, not enough shock length, rear hangers are extending & maxing out, It looks like the car seperates & then stops abruptly!! This will cause wheel hop, another posibility is the shocks are too soft on the re-bound "compression", you can abviously tell the extention is there, but the 1st. thing the rear will want to do once it hooks is throw the rear back up (re-bounding), if the shocks are too soft this will happen, but the 1st. things i would check is the shocks travel & the rear hangers position.
 
i think the left side lifting thing has to do with the car twisting more than the weight shift it looks real good i think you just need to tweak the shocks some do you have sub frame connectors if not that would help alot that way the weight of the car will shift more evenly. and help keep the tires loaded rather than wanting to twist towards the right
 
Looks like the /6 springs are killing you.Plus the Pinionb Snubber is way to far from the floor.

I would suggest,SS Springs or XHD Springs
Adjustable Pinion Snubber 1/4"-1/2" from the floor.
Good set of drag shocks.

If you need more traction,Cal-Tracs.
 
Fix the pinion angle, set the shocks on 50/50 in the back and 90/10 in the front and lose the snubber, then see how it does. Your springs may be your biggest problem though.
 
hey guys, thanks for the replies

the snubber is probably closer than 1" (its REAL close) to the floor, i was just giving a guesstimate since i never measured it (this setting is the only setting it will fit at).. The springs have been clamped extra in the front, with only one clamp in the back...front is slant 6 t bars and original worn out shocks, but i may go to a calvert 90/10 as the big end is kinda squirrely

I think my pinion angle is possibly killing me more than anything and the car will not be driven until i fix it. What do you guys recommend for pinion angle on a street/strip stickshift car? I think if i fix the pinion angle and get a longer shock for the rear (i.e. truck shock) i will solve most of my wheelhop worries...If it comes to having to buy new springs, id almost rather go with caltracs, though i dont know how well they work without the monoleafs and how streetable they are, since i dont really have the money for the monoleafs ontop of the caltracs themselves

thanks so far for the help guys! much appreciated!
 
Pinion angle is the difference between the centerline of the transmission's output and the pinion gear. The rear pointed up or down is fine so long as it isn't any different from the transmission's angle under power. Under power is the key... This is so the smallest amount of stress and wear occur to the Ujoints. It also uses the least amount of power to spin the joints so if it's way off, even without any vibration or other stuff, you will go faster. So you need to get your car level and on it's suspension where you can work safely under it. Put some weight in the driver's seat to be "you" and a full tank of fuel. Then use an angle finder or magnetic protractor on the ujoint flange on the slip yoke. take a reading. Then go to the side of the yoke on the rear and do the same. Make sure when you take readings the surfaces of the flange and yoke are parallel to the ground. The difference of those two is you pinion angle. When you goto set it, you will want to use shims under the spring perches. 4WD shops usually have them in 1° - 6° increments, I use Mr Gasket, Moroso, and Lakewood most of the time. For a street car I'd go 2° down. For a drag car with the typical factory type suspension I'd go 4° down. For a road race or fast (as in top speed and handling) car I may go dead even. All depends on the suspension and power level.
 
Upgrading the leaf springs will help alot. I wound up a pair of six leaf HD springs so much they ended up looking like question marks. Now with SS springs, rear sway bar and an additional pair of kicker shocks mounted horizontally, I run 1.70's for 60 foot with no hop and minimal spin while dumping it at 4000 (stick shift).
 
65_valiant said:
and it looks like you have ZERO weight transfer, as in the rear doesnt squat. at all.
Click to expand...

MoPars should NOT SQUAT when stock or S/S springs are used....ever. No way, no how!

mopar340dave said:
Fix the pinion angle, set the shocks on 50/50 in the back and 90/10 in the front and lose the snubber, then see how it does. Your springs may be your biggest problem though.
Click to expand...

I agree, though it's been awhile, I normally do the whole car suspension in one shot. Theres a pinion angle kit (Shims) that go between the leaf springs and where they mount. They come in 1-2-3 degree angles. I've used nuts in a pinch before, but, I really don't recomend it for actual use much less drag racing.

Good run, nice all around, keep at it. This is where the fun begins!
 
id be very cautious with stock leafsprings and no pinion snubber as iv had my pinion(u-joints) bang against the floor pan, luckily it didnt tear up the u joints and drivshaft grinding against the floor pan, i have ladder bars now, but adding more pinion angle will help prevent this. a high biteing tire will need a stiffer spring or your goin to warp the springs, if your running a hard tire then keep the soft springs, some guys use no snubber with super stock springs as they are quite stiff.
 
The snubber is fine for moderate acceleration but we're talking drag here. The snubber hitting the pan can cause the tires to load and unload=wheel hop. Your springs are not strong enough to deal with the torque with or without the snubber, I think. you did the right thing clamping the fronts but a stiffer set will pay dividends bigtime.
 
Can you mount a camera under the car to see what your rear end is doing under load?

My buddy fabbed up a simple bracket and did this to solve his launch issues.

SS springs are a proven way to get your traction but avoid the high arch springs unless you want the *** end wayyy up in the air.

Mancini racing sells the longer drag shocks relatively inexpensive.
 
Purple Haze said:
I say get some SS springs and fix your pinion angle first.
Click to expand...

Agreed! Keep it simple. A set of 002 003 Superstock springs are less than $250 and the correct length shocks will make a world of difference. Then check your pinion angle and adjust as needed. If the car sits too high you can also get adjustable front spring hangers or flip your existing hangers. There should be no need to get fancy at this point. There are plenty of guys out there in A, B and E bodies running into the 10s with SS springs.
 
Looks like the leaf springs are hurting you, I would suggest SS springs I think on the #'s the last digits are 002 and 003. Use a longer shock and tire pressure down to 15lbs and no pinion snubber.
 
What part number are your rear shocks? CE does make a set for the ss sprung cars....I have em. They are part number C2735
 
You must log in or register to reply here.
-

Back
Top