pinion angle

[David Eastman]

I have some wheel hop when I accelerate and when I mis a down shift. According to the GTS Manaul the pinion angle should be between 3 and 5 degrees. My drive shaft is 3 deg and pinion is 0 deg. If I adjust to 5 deg. will this get rid of my wheel hop?

David

[glenbinegar]

Hi david, I think the pinion angle is adjusted to minimize the angular deflection in the universal joint between the differential and the driveshaft, as the rear suspension allows the differential to move up and down. A wheel hop solution must be found elsewhere. G;-)

[NZGTRA17]

Originally Posted by David Eastman

If I adjust to 5 deg. will this get rid of my wheel hop?
David

David, my car currently has 3 degs as well (cant remember the combination between driveshaft and diff). The GTS manual suggests that increasing the pinion angle 'may' increase traction, up to the max of 5 degs. Given this it is worth a try but look out for any vibration issues that may result as you could prematurely wear out the universal joints.

Another avenue to kill the wheel hop would be to try changing the rear shock absorber settings, try going stiffer initially.

One change at a time of course.

[Gatorac]

Pinion angle should be equal to output shaft angle.

look at this pic. http://www.carcraft.com/howto/91758/photo_08.html
For more information than you can use, try here http://www.google.com/search?sourcei...q=pinion+angle

[David Eastman]

Thanks for the suggestions guys. The reason I was looking at the pinion angle to fix my problem is because I had another car that had wheel hop issue and I fixed it by adjusting the pinion. However I may have other issues with this car. I will ask Gary this week and see what he says.
NZ your suggestion makes sence.

Jim, thanks I read that earlier.

David

[Cobra4B]

Bumping an old thread as I need to set the pinion angle on the car. Should this be done with the suspension set at static ride height?

I read that the angles should be equal to outputshaft angle as well, but I guess it really depends on the resulting driveshaft angle which would depend on ride height/load.

My engine is angled 3 degrees downward toward the rear. Not sure where the driveshaft will end up yet.

[NZGTRA17]

Originally Posted by Cobra4B

Bumping an old thread as I need to set the pinion angle on the car. Should this be done with the suspension set at static ride height?

I read that the angles should be equal to outputshaft angle as well, but I guess it really depends on the resulting driveshaft angle which would depend on ride height/load.

My engine is angled 3 degrees downward toward the rear. Not sure where the driveshaft will end up yet.

Brian, I would finish the car off and set the pinion angle along with the rest of the suspension when you do the full corner weight routine. Just set arms up to be in the ballpark at this point.

Kel.

[Cobra4B]

Originally Posted by NZGTRA17

Brian, I would finish the car off and set the pinion angle along with the rest of the suspension when you do the full corner weight routine. Just set arms up to be in the ballpark at this point.

Kel.

I never adjusted the arms when I took them off so it only took a tiny amount of tweaking the upper driver side to get the axle 100% square in the chassis. I made a post on NASA forum in the section for American Iron racers (lots of stick axle cars) - http://www.nasaforums.com/viewtopic....02390&p=437024

Their feedback and lots of self-educating got me to understanding that there are basically two schools of thought.

1. Make pinion parallel to trans output then angle it nose down from there 1-2 degrees. This would have my pinion 1-2 degrees up from horizontal.

2. Always make the pinion a little down from driveshaft... similar to the diagram above. This would put the pinion 1-2 degrees down from horizontal.

Option 1 would have the pinion and crank operating on the same plane under acceleration.

Option 2 would have the driveshaft and pinion in alignment under acceleration which increases power transfer, but may cause vibration from the front and rear U-joint angles not being in the same plane.

I'm leaning toward Option 1. I jacked the rear axle up to estimated ride height and the pinion angle now shows + 1.5 degrees which would mean it's about perfect. Not really knowing any better I didn't take any of these measurements before I took it all apart.

[Panoz60]

David,

Pinion angle is (in my opinion) a tuning tool and can dramatically affect the car's behavior, especially on track-out. I'll try to keep this short....
1. I have always judged pinion angle by the difference in degrees between the driveshaft and the pinion itself. 3-5 degrees is a good baseline. if the car is getting too much forward bite, it can lift the front and cause understeer on track-out after the apex. If there isn't enough angle, you can spin the tires.
2. If you are experiencing wheel hop, you ARE spinning the tires. A few possible culprits a) not enough pinion angle. b) too much rebound in the rear shocks. c) rear tires are toast (too many heat cycles) or not enough air pressure in the rears. (yes, with too much rear pressure it can spin the tires, but it shouldn't wheel hop) Wheel hop is normally caused by the tire deformation under acceleration, so increasing the pressure can marginally stiffen the sidewall and decrease the deformation. This is all assuming you have your rear springs dialed in, and the only real way to do that is with a 7-post, a skid pad, or lots of track-time tuning.

If I were you I would add a degree or two of pinion angle, not going past 5 degrees. If that improves it but doesn't solve it, I would adjust the rebound in your rear shocks. If there is too much rebound resistance, it won't allow the spring to react quickly enough. If your shocks are not adjustable, it's time for a rebuild.

Hope this helps ??

[Cobra4B]

Mark... I bumped an old thread to further discuss pinion angle.

[glenbinegar]

Hi David,

[glenbinegar]

still chasing the wheel hopping?

[glenbinegar]

I do not think I clearly stated my opinion on differential angle. Which is that it should be the same as the engine inclination to minimize driveline vibration due to the universal joints being misaligned (coplanar). I think wheel hop is best managed by Increased shock damping (especially rebound but not exclusively), varying tire pressure and modulating the loud pedal. If you are searching for more traction out of the corners I'd think about relocating the forward suspension pivots upward which has an added bonus of providing some antidive during braking, on the down side it will also increase the for/aft differential movement during normal single wheel suspension travel (transient toeout in bump and toein on droop)which may result in a darty/nervous condition over rough pavement.

[Panoz60]

The beauty of racing is there is no "one" cure for anything and opinions vary greatly.

Pinion angle does effect traction. It is a tuning tool. While they will not fit a Panoz, there are numerous types of upper links (Bisquit style and spring style) that are manufactured specifically to control and tune pinion angle and therefore forward bite/traction. You can commonly see these on GT1s and SPO cars. http://pitstopusa.com/i-10286991-afc...rque-link.html Since these devices will not fit without major chassis modification, your adjustments are limited to what I mentioned in my previous reply.

As far as initial set-up, glenbinegar is correct. Here is a grea article that explains it a littel better http://www.hotrodhotline.com/md/html..._harmonics.php What I am talking about is tuning the driveline after the the intial set-up. Once you have established a baseline for your car, you rarely have to change the pinion angle +/- one degree for tuning.

Also, in my opinion, you should be able to clear the apex of a turn, mat the throttle, and turn/aim towards the furthest point of track out. If you are having to modulate the throttle to compensate for wheel hop your lap times will suffer terribly.

[Cobra4B]

Originally Posted by Panoz60

The beauty of racing is there is no "one" cure for anything and opinions vary greatly.

Pinion angle does effect traction. It is a tuning tool. While they will not fit a Panoz, there are numerous types of upper links (Bisquit style and spring style) that are manufactured specifically to control and tune pinion angle and therefore forward bite/traction. You can commonly see these on GT1s and SPO cars. http://pitstopusa.com/i-10286991-afc...rque-link.html Since these devices will not fit without major chassis modification, your adjustments are limited to what I mentioned in my previous reply.

As far as initial set-up, glenbinegar is correct. Here is a grea article that explains it a littel better http://www.hotrodhotline.com/md/html..._harmonics.php What I am talking about is tuning the driveline after the the intial set-up. Once you have established a baseline for your car, you rarely have to change the pinion angle +/- one degree for tuning.

Also, in my opinion, you should be able to clear the apex of a turn, mat the throttle, and turn/aim towards the furthest point of track out. If you are having to modulate the throttle to compensate for wheel hop your lap times will suffer terribly.

Any pictures of that crazy contraption installed? I can't visualize where it goes.

2nd... tuning wheel hop with shocks. One post above says increasing rebound can help control it. However, in an old post I made about setting up the standard Konis, Gary Jones posted:

I would set the REAR shocks at full stiff rebound to keep the back of the car from raising up under breaking...This keeps the rear end down and weight transfer to the front at a min under hand breaking...If you get any wheel hop at all then go the other way one click at a time...

Set the front ones in the middle for starters...You want the car to squat or raise up in the front when you pick up the throttle...This will transfer weight to the rear tires...If the car picks up a bad push on exit ( all of this is after you put the correct springs under the car ) you will have to put a click of rebound back into the fronts to slow down the weight transfer....Keep in mind this is just a starting point

I set the car up like this. Full rebound in the rear and #2 click in the front. The standard Konis have four settings 0, 1, 2, 3 clicks. So rear is 3 and front is 2.

His suggestion is opposite of the one made above in that softening rebound will control hop. This makes sense as stiff rebound would make the shock slower to extend when the hop is compressing it right?

Never had wheel hop in this car, but it putting it back together I found the previous shop had it backwards. They had the rear shocks on full soft. Fronts were correct at #2 setting.