Manual steering

[RonnieP]

I read the tread on the twitchy power steering. I have the similar problem with my manual steering.
Going down an exit ramp with quick acceleration if you hit a bump the car acts like it has play in the
steering.I was thinking that it was me bouncing in the car moving the wheel.Now I am not sure. This is
a m3 . Could the caster be what is causing this also? Sometimes it is straight as an arrow .I have checked
everything over and over.Everything is tight and nothing is in a bind.

[edwardb]

You're describing bump steer. Specific details about your front suspension components and front alignment specs used may help to diagnose how it can be reduced.

[AC Bill]

Sounds somewhat like bump steer to me as well, but your toe can also play a major role in how it handles. What toe are you set at currently?

[RonnieP]

Thanks for the reply. I have a 3 link set up with ff front upper and lower control arms and koni shocks. I have adjusted
the shocks to the 3rd setting to eliminate porposing. The ride height is 4.5 on passenger side and 4.625 on drivers side.It was
aligned at what ff reconmended.However I noticed that the driver side wheel leans out more than the right side.I am thinking
that when I sit in car than it should go back to zero or close to the right wheel.There is no scuffing or wear on the tires
Goodyear 15" tires. I did find that the tire pressure was low on all four tires. 20 lbs all the way around .I put 32 lbs in all
of them and I have not had a chance to drive it yet. I don't understand how the tire pressure got so low. I ALWAYS CHECK
THEM. The steering rack is 2.75 left to right.

[Brian Z]

The body mounts could be shifted slightly to the driver side. You can move the 3/4" front body mounts over slightly if you take the body off. You can tap over the mounts using a board and a hammer or rubber mallet. Just make sure if you move the body mounts over the distance between the 2 mounts stays the same.

That is one sollution to your front wheel sticking out. It is alot of work though if everything is already mounted...

[RonnieP]

Hi Brian,
I think you misunderstood. The driver side wheel has positive camber and the passenger side wheel has close to
zero degrees camber. The body fits fine.

[FFRSpec72]

Was the bump steer checked when you had the car aligned? Does the car have a bump steer kit installed?

[RonnieP]

Hi FFRSpec 72,
I know he did not check the car for bump steer. At the time I did not think that the m3s had a problem with bump
steer. I am thinking that I may need to lower the rack a little.I'm doing some research right now. The books I have
been reading on chassis, shows the lower control arm level at ride height. That can't be with 4.5 " on my car.The tie rods
are not level either with the lower control arms.I am not sure that installing a bump steer kit will help.Dropping the rack
will put the tie rod and lower control arms parellel .Then I will need to check for bumpsteer. Isn't this fun?

[AC Bill]

The driver side wheel has positive camber and the passenger side wheel has close to
zero degrees camber. The body fits fine.

IMHO, camber, caster, and toe should be set the same on both sides. Ride height should also be the same, right and left. I suppose you could allow for drivers weight in setting things up, but then what happens when a passenger hops in?

32lbs psi may cause loss of traction, if you put your foot in it, as well the ride will be harsher. The rule of thumb has been to run 1lb psi for every one hundred pounds the car weighs. IE 2200lbs=22lbs psi..
That being said, I am running 15" tires and set psi at 26lbs (cold) and the handling, ride, and traction is still fine.

Colder temps may have reduced the psi reading. Did you last fill them in the summer, or after driving the car, while the tires were still hot?

[RonnieP]

AC Bill,
Your reply has very good points. Car was aligned with no one in the car. I adjusted the ride height a little
on the drivers side later. Car is better handling with a passenger in the car. It could just be me , a friend of mine who
knows cars swears there is nothing wrong with the car. Yes the tire pressure was checked during warm weather. I ran
25lbs in the rear and 28lbs in the front. I changed the pressure to 32lbs resently and have not driven the car yet.
This car has no problem breaking the tires loose. thanks

[rich grsc]

Alignment should be done without you in the car, your weight wont change the alignment. If you can see a difference in camber, then it needs to be redone. make sure you have toe in, not toe out.

[RonnieP]

Just an update,
I drove the roadster this weekend. Took it out on the interstate and car did fine. With 32 psi it was a little harsh
when I hit a rough spot in the road. However it recovered very quickly. I kept my arm resting on my leg so when I got
bounced around I didn't move the steering wheel. Car tracked very well without wandering. Go figure.( air pressure)
Thanks for your suggestions
Ronnie

[edwardb]

I think you're running the tires too hard. AC Bill had it right in his post #9. You should be closer to those numbers. Over 30 is just too much. I think something else is going on. With the quick steering these cars have, always have to concentrate and not be too relaxed. But mine is very settled and not jumpy at all at highway speed. I run the tires (17's) 24 psi front, 27 psi rear. Assuming the alignment, toe-in, etc. are correct, have you done an actual bump steer check? I wouldn't call it good until you do.

[Jeff Kleiner]

Just echoing the other guys. 32# is way high on these cars. At that pressure you're just running on the centers. Low to mid 20s are more like it.

The 3rd notch in the FFR Konis is too stiff on rebound unless you are running some monster stiff springs. You should probably be all the way down to zero in front and either zero or up one in the rear.

Are your adjusting collars on each end pretty consistent side to side, i.e.; LF and RF within ~1/8" and the same in the rear? If you have the springs cranked tighter on diagonal corners your ride height may be correct but the corner weights can be wonky which can cause some odd and/or evil handling.

As mentioned check and measure for bump steer. Mk3s with the usual combination of components are usually not bad but you really need to know what you actually have.

Assure that the rear axle is centered in the chassis, not the body.

Finally, verify and/or correct the alignment. For a manual steering street car you need to be 1/2 degree negative camber, 3 degrees positive caster and 3/32"-1/8" toe in.

I think the car's nervous behavior is just going to come down to a combination of adjustments. Good luck with it.

Jeff

[AC Bill]

Car was aligned with no one in the car. I adjusted the ride height a little
on the drivers side later.

That statement could be an important factor. If you in fact did adjust the ride height after you had the alignment done, your alignment will now be out of whack. Once an alignment is done at a set ride height, you have to keep it at that ride height. (unless you do another alignment) This may explain why the camber appears different on either side as well.

New shocks/springs do tend to settle after a few miles of driving, so if the ride height changes from settling, you "can" adjust it back to the ride height, the car was at when the alignment was initially done. Other than that, any ride height adjustment done after an alignment, requires another full alignment..

It may be that the increased air pressure is simply creating less tire drag, as there is less road contact, and it isn't pulling as much. As Jeff mentions the shock setting will also create issues with our cars, as light as they are. Many builders have found the ride improves, using the lighter setting. least for street driving anyways..

I hope you get it all sorted out.:)

[RonnieP]

AC Bill,
Thanks for the advice. The more I think about it you are right about the ride height. The springs (shocks) did settle
after a while and I had to adjust the ride height back to when I first had it when I had it aligned.I am going to have the
alignment checked again also. As far as the lighter setting on the shocks . At 60-70 mph going over a bridge on the interstate
it pogo so bad I couldn't stand it.Now on the last setting it's not an issue.This is with the springs that came with the kit 350
-500 lb .True ,I need to lower the air pressure on the tires.
Jeff,
When adjusting the shocks The collars are the same .Yes the rear axle is the same on each side of the chassis.I'm
going to recheck everything.I even thought about putting it on scales.

[RonnieP]

I put the cars on scales last weekend . With 26 psi in all tires with no one in the car.
left front 525 right front 525
Ride height 4.5 -4.25
left rear 641 right rear 611
total weight 2302 cross weight 50%
I don't have the figures with me ,but the driver in the car I still have a 50% cross weight. There was a 90lb difference
between the left a right side.I'm going to take it back to the alignment shop and have it check again.