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Location:
Finland
Registered:
June 2002
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Location:
Eskilstuna, Sweden
Registered:
May 2002
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Re: lowered suspension - rwd loss of traction in launch
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Mon, 09 December 2002 01:07
 
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The issue is essentially in relation to the change to the diff pitch post lowering. That is the face of the diff - tailshaft join has been rotated so that the diff pitch is no longer set to 3 degrees.
In order to correct this issue you need at least a set of upper and or lower (don't really need both, unless your really low) control arms to re-rotate the housing back to a 3 degree setting.
Cheers.
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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: lowered suspension - rwd loss of traction in launch
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Mon, 09 December 2002 01:10
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Is this where someone is supposed to start a prolonged discussion about pinion angle? How lowering a car alters pinion angle, with potentially worse off the line bite? And then by using adjustable upper control arms, the pinion angle can be altered, potentially improving traction?
The drag boys are right into this.
I, too, look forward to some juicy discussion.
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Location:
Cabramatta, NSW
Registered:
May 2002
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 Re: lowered suspension - rwd loss of traction in launch
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Mon, 09 December 2002 01:11
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When you upgrade the springs, you get less weight transfer to the rear. That gives you less squat, and therefore, less traction.
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Location:
Eskilstuna, Sweden
Registered:
May 2002
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Re: lowered suspension - rwd loss of traction in launch
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Mon, 09 December 2002 01:19
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Yes Giant T,
This will be a pinion angle picnic!...  I think it needs to be changed post lowering myself.
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I supported Toymods
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Registered:
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Re: lowered suspension - rwd loss of traction in launch
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Mon, 09 December 2002 01:23
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Correct pinion angle depends on the type of rear end. For a leaf spring rear end, normally this is 6-8 degrees, but for a modern multilink rear end this should be about 1-3 degrees. This reason for this is the relative 'tightness' of the rear ends. As a car accelerates, the diff will want to rotate up - a multilink rear end is mounted to the car at 4-6 points, so it is very tightly held to the car and the amount of upward rotation is minimal. During full acceleration, the diff rotates upwards about 1-3 degrees bringing the diff into alignment with the rest of the drivetrain. Leaf springs are much sloppier and less accurately postion the diff, and the springs also develop a degree of bind, so the diff rotates upwards much more, hence the bigger angle. The leaf spring bind is the reason for 'axle tramp', and tramp rods are fitted to minimise this bind in the springs.
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Location:
Gold Coast
Registered:
May 2002
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Re: lowered suspension - rwd loss of traction in launch
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Mon, 09 December 2002 01:42
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I'm with NArk on this one. Altering geometry angles only chews out your uni joints quicker IMHO. The weight transfer has changed (reduced) hence the wheel spin off the line. This is why the drag boys run 90/10 shockies etc (or is it 10/90??) to allow the front to lift quicky transferring weight to the rear wheels for extra bite off the line.
My 2 cents worth.
Steve
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I supported Toymods
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Registered:
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Re: lowered suspension - rwd loss of traction in launch
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Mon, 09 December 2002 01:48
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"Little from column A and a little from column B." Abraham J. Simpson
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Location:
Finland
Registered:
June 2002
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Re: rwd loss of traction in launch - pinion angle - post lowering susp.
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Mon, 09 December 2002 01:53
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Now we're getting somewhere. Thank's for the interest thus far 
Pinion angle 'eh?
Someone care to specify which way 3º. As we're looking from diff face point of view, is pinion input shaft pointing in 3º angle downwards or up?
I take it should be downwards - right? Since in launch it'll presumably crawl up a touch (due to axle rotation) thus ending up well aligned towards tranny and all.
I bet a small amount of dosh on the following.
If we would alter top support arm bolt holes on rear axle in such way that static pinion angle would be zero - it would not affect tyre bite in launch.
For this statement to be true, the top arm angles (compared to sea level, bubble gauge or whatever) should be identical as prior to bolt hole altering.
This is how adjustable 4-links work. We change link angles.
If we were to change link attacments onto rear axle in such manner that oem pinion angle is maintained, but alter link angle from oem setup - we get different tyre bite in launch.
This is my understanding on this issue thus far. Looking more info on this 'tho.
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Location:
Eskilstuna, Sweden
Registered:
May 2002
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Re: rwd loss of traction in launch - pinion angle - post lowering susp.
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Mon, 09 December 2002 02:43
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Hi,
It is 3 degress closer to ground for multilink as Giant T said. In my case I have adjustable uppaer and lower arms as well as multiple mounting points on diff/axle housing. This allows me to run the links in the OEM position or in another position.
Once the car has been lowered a fair amount you use different mounting points so that the link arms are near factory angles and at the same time you change the lengths you set the pinion angle.
You also make some Panhard rod changes - but that's a little off topic. This way I end up with a near factory set-up as far as angles go but heaps lower. Best of both worlds IMHO.
Cheers.
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Location:
Sydney
Registered:
May 2002
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Re: rwd loss of traction in launch - pinion angle - post lowering susp.
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Tue, 10 December 2002 06:41
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anyone who is after it.. I was talking to noltec the other day(one of our sponsors) and they do a adjustable upper arms for the old celicas, as they do for most cars.
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Location:
Finland
Registered:
June 2002
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Re: rwd loss of traction in launch - pinion angle - post lowering susp.
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Tue, 10 December 2002 11:05
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Could someone explain in great detail just how the lenght adjustable links would address this problem.
There is an age old racing trick for live axle support.
To restore bottom link attitude we'd need to lower attacment location on axle as much lower as we've lowered the suspension. With 50mm's lowering job we'd be happy with at least 50mm lower mounting point on an axle.
I have seen on a Japanese Toyota site special brackets for rear axle which relocate mounting holes just that much lower.
Here are linked pictures I spotted on american 4AG forum (where I posted this same suspension dilemma).
Factory stock rear axle mounting bracket. An extra fixing hole drilled:
Special relocating bracket istalled on stock rear axle:
Closeup on installation when complete:
Entire article here:
http://www.k2rd.com/Online_Catalog/AE86/products/r ear.html
In a proper fully adjustable 4-link configuration top links need adjustment as well in similar manner. I am currently looking into this. Will install modified rear axle in several months time.
To present info I have on link attitudes they can be divided into 2 main categories; optimised for either launch traction, or neutral performance in mid curve (in racing environment).
-A.
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Location:
Finland
Registered:
June 2002
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Re: rwd loss of traction in launch - pinion angle - post lowering susp.
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Mon, 16 December 2002 01:06
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First I have to say - Youngy, your setup sounds thus far the proper way of doing things. Good job!
I myself will not stretch as far as having multiple hole brackets. I shall most likely just restore attitudes close to factory angles and leave it at that.
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I have found some material in the net that supports my view on the pinion angle issue. (What it's worth, I gather almost anyhting can be proven if we hold 'stuff found in the net' as absolute truth on the matter.)
After ploughing quite a bit in American drag racing forum world, these two quotes sum up well info I've gathered on this pinion angle (PA) issue. I found these at: http://www.hardcore50.com/
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more pinion angle discussions
NoSlix
Rookie
Registered: May 2002
Location: Texas
Posts: 40
Dan at Wolfe Racecraft told me last week that he doesn't know why people are so anal about pinion angle. He said their cars go the same no matter what pinion angle they use. I have to agree with that. I've tried anywhere from -5 to +2 and 60ft'd the same. What I did notice was that anything positive produced drivetrain vibration.
__________________
Shane Hill
9.12 at 151mph
1990 LX T76/glide/igloo
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Bulletracing1
Junior Member
Registered: Dec 2001
Location: Markle, IN
Posts: 10
In my testing, what NoSlix said that Wolfe told him is true. The only thing you are trying to do is reduce friction in the driveline, it will not affect traction or the car going left or right. Yes, the reason you adjust the pinion angle down is because of upward pinion movement under accel. As for your comment on the ladder bar/4 link advantage, PA will still change as the suspension travels but because the ladder bar/4 link has solid mounts it won't deflect. With rubber bushings they have to deflect or the suspension will just bind up. One last thing, another place that you can measure engine/trans angle is the starter, it's bigger than the damper and easier to stick an angle finder on, unless your headers are in the way which is highly possible.
__________________
Trent Braden
NMRA REN #7 in '00
NMRA Hot Street 3114 in '02
http://www.bulletracing.net
[Updated on: Mon, 16 December 2002 01:17]
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