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I am restoring what used to be my dad's 75. He became too busy to drive it an it kind of fell into disarray. He told me that one of the things he did not like about the car (probably the only thing) was it's tendancy to walk up and down the tire grooves in the highway. Does the width of the tires in relation to the width of the grooves in most highways cause this sort of tendancy? I have not yet had the pleasure of driving the car, and wont until my resto is complete, so I am curious if this actualy happens and how severe it is.

On a side note, I will be posting a very extensive library of pics of the car shortly. It is currently sitting in three pieces... Body, Frame, and Engine. This gives me a great opportunity to document the car from the inside out.
 

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Not sure about the tire question, I'm sure someone will jump in with some help. Would love to see the pics tho. I had a 68 convertible that I restored from the ground up. I have a complete photo history of the restoration. You'll enjoy looking back at all the pics when you get it done. :)
 

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mga said:
worn suspension parts will cause that.
I had that on my 96 vette, shortly after a 4-wheel alignment. They set the front end up to aggressive, and the car followed the grooves, and I'd have to fight the car to get it to change lanes!

Anyway, I brought it back and they re-aligned it to factor specs, and then the car was perfect.

Of course, I had 275's in the front and 285's in the back, which probably exagarated the problem.
 

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Patric what do you call aggressvie? The stock specs call for about 1 degree positive caster and I run 5 degrees positive. The stock specs also call for positive camber and I run negative .75. They make the car extremely stable at high speed. As for toe the old specs of 1/8th toe in were for bias tires, when radials came out the toe should be cut in half or 1/16th toe in.
I have been reading articles on setting it to toe out with negative camber and right now run 1/8th toe out.
But this keeps changing week to week as I play with the toe.
My next modification will be with extended spindles.
I agree with the worn suspension parts including the steering box. The pitman bushings to pitman shaft clearances are too large at around .006 and should be reduced to a tight .001.
I run 265 front tires without a problem following road grooves.
 

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norvalwilhel said:
Patric what do you call aggressvie? The stock specs call for about 1 degree positive caster and I run 5 degrees positive. The stock specs also call for positive camber and I run negative .75. They make the car extremely stable at high speed. As for toe the old specs of 1/8th toe in were for bias tires, when radials came out the toe should be cut in half or 1/16th toe in.
I have been reading articles on setting it to toe out with negative camber and right now run 1/8th toe out.
But this keeps changing week to week as I play with the toe.
My next modification will be with extended spindles.
I agree with the worn suspension parts including the steering box. The pitman bushings to pitman shaft clearances are too large at around .006 and should be reduced to a tight .001.
I run 265 front tires without a problem following road grooves.
Norval, I do not know what they set it up as. I went to a place that sets up race cars for road racing.

The other problem I had with that initial alignment was bump-stear. I would go around a sweeping bend, and the car would jump all over the place, and I'd feel it through the stearing wheel. Not fun!

But, I went back and said, "no good" and to just do factory specs.
 

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Discussion Starter #8
Thanks for all the input. The alignment is comming up quickly on my todo list while I restore the entire suspension. Having not heard of this problem from other owners I did not think it was a problem with the car in general. I guess I will just have to wait and see.
 

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Patric you can do alot for bump steer by lowering your outer tie rods about 1 inch. You can do it with a stud and heim joint form Coleman racing or I will spell this worng Gulstein? He has blocks and different tie rod sleeves. Either makes a big difference in bump steer.
If I was getting your car aligned I would try for 2.75 caster, negative .75 camber and 1/16 toe in. The most important is not just within specs but the same side to side. If one side is on the low side but within specs and the other side is on the high side but still within specs both sides are in specs but the car will not steer right.
It is important, more important to be the same side to side.
 

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rgevers04 The problem is very common and you A arm bushings are probably also shot. I would replace everything as routine maintenance but the steering box is a specialty item that many can not do. A rebuilt box is only seals and bearings and does not address the pitman bushings. Stock replacement bushings still give about .003 clearance to the pitman arm and that is too much. YOu really have to go custom fit on the bushings.
 

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norvalwilhel said:
Patric you can do alot for bump steer by lowering your outer tie rods about 1 inch. You can do it with a stud and heim joint form Coleman racing or I will spell this worng Gulstein? He has blocks and different tie rod sleeves. Either makes a big difference in bump steer.
If I was getting your car aligned I would try for 2.75 caster, negative .75 camber and 1/16 toe in. The most important is not just within specs but the same side to side. If one side is on the low side but within specs and the other side is on the high side but still within specs both sides are in specs but the car will not steer right.
It is important, more important to be the same side to side.
I wish I could figure out the current setup. They place that did it used a regular rack, I know at goodyear they give you a nice printout of the before and after settings.

But, the alignment is perfect now, I wouldn't change a thing.... until I get coil overs!
 

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norvalwilhel said:
rgevers04 The problem is very common and you A arm bushings are probably also shot. I would replace everything as routine maintenance but the steering box is a specialty item that many can not do. A rebuilt box is only seals and bearings and does not address the pitman bushings. Stock replacement bushings still give about .003 clearance to the pitman arm and that is too much. YOu really have to go custom fit on the bushings.
Norvel, I have developed a lot of play in my pitman arm bushing. The power steering pump went out and I had to drive it for a while, putting a lot of stress on the bushing. After replacing the pump, I found the play was so bad at highway speeds (as described above in someones previous post) it wandered back and forth on the highway lane.
Now to my question. Where do you recommend getting the parts to replace this bushing (custom built bushing you speak of). As I have not done this before on my '75, breifly describe the procedure and any helpful hints to replace this bushing.

Thanks
 

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Norvel, I have developed a lot of play in my pitman arm bushing. The power steering pump went out and I had to drive it for a while, putting a lot of stress on the bushing. After replacing the pump, I found the play was so bad at highway speeds (as described above in someones previous post) it wandered back and forth on the highway lane.
Now to my question. Where do you recommend getting the parts to replace this bushing (custom built bushing you speak of). As I have not done this before on my '75, breifly describe the procedure and any helpful hints to replace this bushing.

Thanks

If you pull the steering box out and take it apart you will find the pitman shaft is held in the case by 2 bushings plus a bushing in the cap. The shaft wears slightly and so do the bushings. I polish the shaft in a lathe to remove all rough marks, mike it for diameter. I then check the bushings in the box, use a internal mike, mike them and found .006 differnece. This will never do.

GM sells replacement bushings but they still gave .003 clearance. They were easy to replace. Still too much clearnace.
I then bought bearing broze in blank form. The OD of the bushiings are almost stands size so a little clearnup on the lathe and they would press in. But first I machined the inside ID to about the same dimension as the bitman shaft.
I also left the bearings longer then stock because there is lots of room. I then pressed the bushings in which also shinks the ID a littel. I then used a long hone and honed, test fit, honed etc until it was a perfect tight fit.
For the cap I removed the old bushiing, mashined a new one, chuched the cap in the lathe again and turned the ID to match the shaft.
The last thing is the washer under the bolt in the cap. It must also be perfect to prevent the pitman shaft from riding up and down. Find a washer, sand it if necessary until there is almost no play under the bolt head.
I installed new bearings, seals and adjusted to specs.
Feels like a new box, Wait a miniute it is a new box.
Any mahcined shop could do this easily.
Norval
 
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