Pulls To Right When Power Is Applied

[dkirk]

Just when I thought my '88 was all sorted out, I'm now realizing that it wants to go (very slightly) to the right when power is applied. This is especially noticeable when on a smooth, lightly crowned road, in 3rd gear, engine turning around 3000 rpm, and full throttle is applied. Car just nudges slightly to the right, requiring a couple of degrees of left steering wheel input to remain straight. When throttle is closed (for the next gear), car will then nudge to the left.

My prognosis is as follows:
1) Rear spring plate bushings need replacing
2) Rear trailing arm bushings need replacing
3) All of the above, as they're all original

Has anyone experienced this and what were the offending parts that needed replacing?

[rickybbear]

has it been aligned recently? I guess# 2

[Noah930]

Are all 4 tires fully aired up?

[rnln]

- right rear is toe in a little more than left wheel?
- one of the right brake caliber is slightly stuck?

[fastfredracing]

Wheel bearing with some play in it.

[BK911]

Check your thrust angle.
Attach a string to the back of your rear tire and stretch to a jack stand in front of the car.
Move the jack stand until the string barely touches the front of the rear tire.
Measure distance from string to center cap of front tire.
Repeat on other side.
Measurements should be VERY close.

Quick alignment check.

[hcoles]

Originally Posted by BK911

Check your thrust angle.
Attach a string to the back of your rear tire and stretch to a jack stand in front of the car.
Move the jack stand until the string barely touches the front of the rear tire.
Measure distance from string to center cap of front tire.
Repeat on other side.
Measurements should be VERY close.

Quick alignment check.

Thanks, never thought of that. Quick/easy.

[5String43]

An alignment issue?

[rsscotty]

I have seen this before...the alignment was good. It ended up having the corner weights way off. After re-indexing the left rear torsion bar to get the weights where they should be everything was fine.

[HelmetHead]

Do you hear any growling noises at high speeds (+100)? You may have a rear axle bearing going out.

[hcoles]

a proposed alternate to testing at 100, jack up one side at at time place wood dowel or auto stethoscope on arm at hub and spin wheel, might give an indication of bearing condition especially if both sides sound significantly different, can also try cocking the wheel to see if any play

[dkirk]

Thanks guys, for all the great suggestions. The following has been ruled out:

Tire pressure - 29 psi front, 36 psi rear, both sides equal
No dragging brakes
Front end is aligned to spec
Corner balanced with side-to-side weights being very close

Could possibly be a wheel bearing. I hear a change in sound quality when off vs. on the throttle. Will perform the stethescope test plus wheel cocking test.

Rear wheel alignment was performed during set-up several years ago. Probably worth doing the string test again just to check.

She's going on the rack tomorrow and I'll let you know what I find.

[hcoles]

something just occurred to me... what if a brake pad got contaminated or ? somehow became different than the others, easy to pull and look, clean and reinstall

[tharbert]

"slightly crowned road" ???

[calling911]

I wanna know the answer to this...

[911pcars]

"Corner balanced with side-to-side weights being very close"

How close? Road-going 911s have a driver and a battery not symmetrically located.

Many consider "corner balanced" as either:

a) LF + RR = RF + LR
or
b. LF/LR % = RF/RR %

Or, previously "repaired" collision damage?

Sherwood

[bfunke]

A little rudder is required to overcome engine torque and p-factor...oops - wrong air cooled ride!

On your Porsche I'd carefully check tires, bearings, bushing and allignment specifications.

[hcoles]

adding confusion:
total right vs total left can't be changed
total front vs total back can't be changed

you trade off right vs left front against right vs left rear, when braking hard you want the fronts to be close ( within 50-80 pounds?) of each other. I think that is what a guy told me when he did the corner balance. I'm not an expert, just throwing in my 2 cents. In any case, what ever he did has been great for 8 years or so.

[fastfredracing]

You stating that it changes sounds when on throttle, and off throtle tells me that it very well may be a wheel bearing. Jack the rear up, and carefully look for any play in the rear wheel, grab it , and try to move it in and out from the two sides, and then from the top bottom. I also like to put my hand on the caliper, and spin the wheel by hand. A bearing that is on its way out can often be felt as roughness transmitting through the metal parts. Sometimes hard to tell, but if one side is smooth, and the other is rough and scratchy feeling, then there you go.
I have fixed more than one 911 with this condition, and I found that there was noticeable play in the rear wheel bearing . As stated above, also look for worn, or loose bushings , spring plate bolts etc...

[dkirk]

Here's my set-up:

Chassis –

• Lowered and corner-balanced (full fuel, 175 lb dr. side, 140 lb pass. side using sand bags, fuel tank 1/2 full)
o Ride height-to top of fender-front – 62.9 cm (L), 63.7 cm (R)
o Ride height-to top of fender-rear – 63.7cm (L), 64.8 cm (R)
o Angle of attack @ door sill – 1.3 deg (nose down)
o Front caster – 6.0 deg (L), 6.0 deg (R)
o Front camber - .7 deg (L), .7 deg (R)
o Front toe-in - .125 deg (L), .125 deg (R)
o Front tire load – 593 lb (L), 586 lb (R)
o Rear camber – 1.7 deg (L), 1.7 deg (R)
o Rear toe-in - .1 deg (L), .1 deg (R)
o Rear tire load – 856 lb (L), 842 lb (R)
o Total weight at setup condition – 2878 lb
o Distribution: Front – 41%, Rear – 59%, Cross – 50.1%
• Tires – Toyo Proxes
o Front – T1R 205/55/16
o Rear – T1R 225/50/16
• 6.5 mm rear wheel spacers

"Crowned Road"...Paved roads aren't flat (or shouldn't be). They are actually formed as a large radius (crown) in cross-section, with center of the road being higher than the edges. Here in WI, considerable crown is noticed on some roads, probably to better shed water from melting snow in winter. Most cars will tend to drift to the right, hands off, due to road crowning. I'm no civil engineer, so someone with more knowledge on the subject please chime in.