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Front spec alignment for radial Tires

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Looking for specific specifications for front end alignment for radial Tires on 63 Riviera

 

 

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From the search feature:

 

Read the last post in this thread. Then do a search for 'positive caster' and see what Tom T. and others are doing to achieve that.

 

 

 

 

 

Edited by RivNut (see edit history)

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Certainly, there are a few things which are more critical on radial tire alignment than on bias-ply or bias-belted tires . . . both of which were available when the first-gen Rivieras were still "new" or "used cars".

 

The toe-in adjustment is something of a "pre-load" adjustment to take into account the actual "rolling toe-in" of the vehicle.  How much the rubber in the suspension pivot points will compress as the tires roll down the pavement, for example.  End result should be a "zero" rolling toe, as close as possible, generally, but a slight amount of "toe-in" can help stabilize the vehicle.

 

In general, I don't recall any magazine articles on the best alignment setting for radial tires, back then.  There was agreement that Camber was less critical with radials due to the greater flexibility in the sidewall area.  Plus that toe-in adjustments might be best if set toward the minimum of the factory specs.

 

Reason for the "min-spec" setting?  The radials have less rolling resistance than bias or bias-belted tires, generally.  Therefore, less pre-load is needed in the settings to achieve the zero-toe-in rolling toe-in ultimate goal.

 

When GM started to use the All-Season radials in the middle 1980s, that was the start of the modern era of tire alignment, so to speak.  For some "chunkier" tread designs, the existing toe-in setting resulted in poor tread life and wear patterns.  In this "modern era" of front end alignment, that was when toe-in settings could be expressed in either "inches" of toe-in, OR "degrees" of toe-in (usually decimal numbers!).  I don't recall any other significant changes in the front suspension components, just the change in specs to account for "harder" tires and less tread compliance, compared to prior tire designs.

 

Increasing the Caster adjustment toward max can have a few affects.  One would be more forceful self-centering of the steering wheel after completion of a turn.  The other might be (especially in the non-power steering days!) increased steering effort, not a big factor in the power steering eras.  But the other thing can be that it adds more negative camber to the outside wheel in the turn, with increased positive camber to the inside wheel in the turn.  Why is this significant?  As the body leans into the turn, depending upon the particular suspension geometry, the wheel can lean in the same manner as the car body/chassis does.  The additional negative camber on the outside (greater load bearing) wheel helps brace the tire against the greater forces it now sees, by keeping the outside tire more vertical to the road surface.  Similar with the inside tire, as to keeping it more vertical to the road surface as the car body/chassis leans.  How much this helps can be dependent upon how much this sort of thing is designed-into the basic suspension geometry of the vehicle.  I  believe that a max of about 2 degrees of positive Caster is about all that can be achieved, unless the design has more built into it from the start.  In any event, more positive Caster is generally associated with greater straight-line stability as it keeps the front tires "centered" in their side-to-side turning arc.

 

In prior times, if a car could have both manual or power steering, the power steering models had alignment specs with positive camber, the manual steering model of the same vehicle would have negative Camber settings, especially on the heavier cars, for easier steering efforts.

 

In cases where "radial tire lead" happened in the middle 1970s, the Caster adjustment was used to balance that, deviating from the factory specs in the process.  Just as when highly-crowned roads existed in prior times, the front wheel with the highest Caster was the side the vehicle would "lead" toward, keeping a centered steering wheel rather than having to consciously counter-steer "up" the crown to stay "in lane".  "Cross-caster" is that spec allowance.

 

In general, to me you can look at the factory specs or you can use some basic generalities.  With radial tires, toe-in needs to be toward or at the low end of the factory spec, possibly just a tad above "zero", especially with recent-new suspension bushings.  For bias ply, use the factory specs.    Camber should be pretty much "zero", too.  Caster?  Aim toward the factory specs "preferred" setting or the upper end of the spec.

 

Then . . . to complete the situation, aim for a minimum of 28psi in the rear tires.  Back then, the "soft ride" pressure was usually 24psi, but many stated that for "highway speeds" to increase that cold pressure by 4psi, which is 28psi.  For the front, which is where the majority of the car's weight is carried (unless the car's trunk and/or rear seats are occupied, I found that an additional 2psi would balance the weight-carrying capacity of the tires with the weight each axle-end of the car carried.  So,, 30 front/28 rear.  From there, add air pressure to maintain that f/r balance.  Steering response is a little sharper and each tire should wear "flat" across, no thin spots in the middle or edges as a result, especially with bias-[ly tires.  If more weight is carried in the trunk, add at that end only.  The whole orientation is to help decrease "understeer" in turns.  Proceed at your own discretion in these areas.  It worked for me, but your results might vary.

 

NTX5467

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36 minutes ago, NTX5467 said:

Certainly, there are a few things which are more critical on radial tire alignment than on bias-ply or bias-belted tires . . . both of which were available when the first-gen Rivieras were still "new" or "used cars".

 

The toe-in adjustment is something of a "pre-load" adjustment to take into account the actual "rolling toe-in" of the vehicle.  How much the rubber in the suspension pivot points will compress as the tires roll down the pavement, for example.  End result should be a "zero" rolling toe, as close as possible, generally, but a slight amount of "toe-in" can help stabilize the vehicle.

 

In general, I don't recall any magazine articles on the best alignment setting for radial tires, back then.  There was agreement that Camber was less critical with radials due to the greater flexibility in the sidewall area.  Plus that toe-in adjustments might be best if set toward the minimum of the factory specs.

 

Reason for the "min-spec" setting?  The radials have less rolling resistance than bias or bias-belted tires, generally.  Therefore, less pre-load is needed in the settings to achieve the zero-toe-in rolling toe-in ultimate goal.

 

When GM started to use the All-Season radials in the middle 1980s, that was the start of the modern era of tire alignment, so to speak.  For some "chunkier" tread designs, the existing toe-in setting resulted in poor tread life and wear patterns.  In this "modern era" of front end alignment, that was when toe-in settings could be expressed in either "inches" of toe-in, OR "degrees" of toe-in (usually decimal numbers!).  I don't recall any other significant changes in the front suspension components, just the change in specs to account for "harder" tires and less tread compliance, compared to prior tire designs.

 

Increasing the Caster adjustment toward max can have a few affects.  One would be more forceful self-centering of the steering wheel after completion of a turn.  The other might be (especially in the non-power steering days!) increased steering effort, not a big factor in the power steering eras.  But the other thing can be that it adds more negative camber to the outside wheel in the turn, with increased positive camber to the inside wheel in the turn.  Why is this significant?  As the body leans into the turn, depending upon the particular suspension geometry, the wheel can lean in the same manner as the car body/chassis does.  The additional negative camber on the outside (greater load bearing) wheel helps brace the tire against the greater forces it now sees, by keeping the outside tire more vertical to the road surface.  Similar with the inside tire, as to keeping it more vertical to the road surface as the car body/chassis leans.  How much this helps can be dependent upon how much this sort of thing is designed-into the basic suspension geometry of the vehicle.  I  believe that a max of about 2 degrees of positive Caster is about all that can be achieved, unless the design has more built into it from the start.  In any event, more positive Caster is generally associated with greater straight-line stability as it keeps the front tires "centered" in their side-to-side turning arc.

 

In prior times, if a car could have both manual or power steering, the power steering models had alignment specs with positive camber, the manual steering model of the same vehicle would have negative Camber settings, especially on the heavier cars, for easier steering efforts.

 

In cases where "radial tire lead" happened in the middle 1970s, the Caster adjustment was used to balance that, deviating from the factory specs in the process.  Just as when highly-crowned roads existed in prior times, the front wheel with the highest Caster was the side the vehicle would "lead" toward, keeping a centered steering wheel rather than having to consciously counter-steer "up" the crown to stay "in lane".  "Cross-caster" is that spec allowance.

 

In general, to me you can look at the factory specs or you can use some basic generalities.  With radial tires, toe-in needs to be toward or at the low end of the factory spec, possibly just a tad above "zero", especially with recent-new suspension bushings.  For bias ply, use the factory specs.    Camber should be pretty much "zero", too.  Caster?  Aim toward the factory specs "preferred" setting or the upper end of the spec.

 

Then . . . to complete the situation, aim for a minimum of 28psi in the rear tires.  Back then, the "soft ride" pressure was usually 24psi, but many stated that for "highway speeds" to increase that cold pressure by 4psi, which is 28psi.  For the front, which is where the majority of the car's weight is carried (unless the car's trunk and/or rear seats are occupied, I found that an additional 2psi would balance the weight-carrying capacity of the tires with the weight each axle-end of the car carried.  So,, 30 front/28 rear.  From there, add air pressure to maintain that f/r balance.  Steering response is a little sharper and each tire should wear "flat" across, no thin spots in the middle or edges as a result, especially with bias-[ly tires.  If more weight is carried in the trunk, add at that end only.  The whole orientation is to help decrease "understeer" in turns.  Proceed at your own discretion in these areas.  It worked for me, but your results might vary.

 

NTX5467

NTX5467, thanks so much for explanation of what, why, and wear regarding front end alignment of 63 Riviera running radial tires. I’ll summarize your info for my tire guy, who is a real car nut that collects Aldo Romeo cars, when I take the car in for alignment. The last set of 4 tires had plenty tread and no wear patterns but were 10 years old. I’ll take the 63 back for alignment check.

thanks again,

Red Riviera Bob

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MANY newer cars run as much as 10*+ of positive caster. I like to get as much as possible within the design limitations as possible. I run +4* positive on my ''64 for yrs. now. Like like to be around +1/4 to -1/4 on camber. Whatever the toe, let's say 1/8th." - 1/4_ I adjust in the middle at 3/16ths. for BOTH sides. So divide that 3/16ths. in half for each wheel. The other positive effect of more positive caster is better resistance to cross winds as well as what was previously mentioned.

 

 

Tom T.

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Re tyre pressure, I'm  doing an interstate trip next weekend, two other passengers but minimal luggage.

 

Have been running 35psi all round on 235/75 R15 but now think this might not be correct.

 

Is this too high, as NTX5467 mentioned 30 front and 28 rear?

 

What pressures do others run in theirs?

 

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2 hours ago, rodneybeauchamp said:

Have been running 35psi all round on 235/75 R15 but now think this might not be correct.

 

In the 1980s, when radial tires became popular, nearly every 60s, 70s, or 80s American car in the country (USA) had 35 pounds in the tires. That was also the maximum pressure listed on the sidewall.

 

The factory would deliver the cars with a sticker in the door advocating some ludicrous low pressure, like 24 or 26 pounds. The proud new owner would then drive from the dealership to the nearest gas station complaining about the flat tires. I or some other fellow would pump the tire pressure up to 35 pounds where it would remain through every set of tires that the car ever wore.

 

You certainly can fine tune tire performance with pressure. NTX5467 gave a very good explanation of how. If he thinks 30/28 is better on a Riviera, I am inclined to believe him.

 

You wont hurt anything with 35 though. Everyone did it.

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Bloo, I’m no hot rod, nor am I a kid. The GM cars I drove in the 60’s with power steering came right back to me the minute I got behind the wheel of my 63 Riviera. I’m not saying it is bad, but a person has to pay plenty of attention to speed, braking, turning -you know driving a 63 Buick Riviera. The Riv I bought is solid and straight. Nonetheless, the feel in the Riv is much different than my 2013 Toyota Highlander, or that matter my 1997 Ford F-250 pick up.

im going to review all the good information I have and experiment with different tire pressures. I always liked my Tires at what the car specified, of course within range of the tire spec as well. I did not expect the Riv to drive any different than it did with 225/70 R 15 when I first bought the car. I put on new radials of the same size just different brand. The shocks are good and the front end tight, still I’m going to experiment with a new alignment and tire pressures in front and back. The country roads in Maryland are pretty good and well enough maintained you don’t need a Humvee to travel, but with the Riv I want to keep my speed well in check.

Thanks again, 

Red Riviera Bob

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Bob,

 

   One of the BIGGEST improvements you can make to your STOCK '63 Riv. is to install a newer steering box with LESS turns lock-lock.  You WON'T believe the diff.  Adding to that is Bilstein shocks or at least KYB's, a bigger front sway bar, poly bushings in certain areas ONLY, MAKING SURE the center link is tight. Adding to that is rear shocks of the same make as above, a rear sway bar, & poly track bar bushings.

   You WON'T believe the diff. in the way the car handles & feels. Almost like a modern day car with rack & pinion. It will feel better than your F-250 & almost as good as the Highlander.

   Just my thoughts as I've done them myself over the yrs. & have told MANY about the same.

 

 

Tom T.

 

 

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3 minutes ago, telriv said:

Bob,

 

   One of the BIGGEST improvements you can make to your STOCK '63 Riv. is to install a newer steering box with LESS turns lock-lock.  You WON'T believe the diff.  Adding to that is Bilstein shocks or at least KYB's, a bigger front sway bar, poly bushings in certain areas ONLY, MAKING SURE the center link is tight. Adding to that is rear shocks of the same make as above, a rear sway bar, & poly track bar bushings.

   You WON'T believe the diff. in the way the car handles & feels. Almost like a modern day car with rack & pinion. It will feel better than your F-250 & almost as good as the Highlander.

   Just my thoughts as I've done them myself over the yrs. & have told MANY about the same.

 

 

Tom T.

 

 

Tom, great! All this is brand new news to me. I would not mind in the least doing some improvements to improve the handlings. Thanks a lot yet again. I’ll paper copy your recommendations and place them in my Riviera log book. Helps to keep records of what you’ve done to the car.

Red Riviera Bob

 

 

 

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Tire Pressure --  The numbers I mentioned were with pre-P Metric tires, which had a max inflation pressure of 32psi.  And tires whose tread width was generally equal to the wheel's rim width, or thereabouts.

 

If the tires can go higher than 32psi, to 35psi, I don't think that's too much to get excited about.  Main difference might be a little more impact harshness and such at the higher pressures.  Key thing is the front/rear pressure relationship.  If the base pressure was 24psi, then the recommendation of "+4psi for high speed driving", then that's 28psi.  Then "+2" for the front".

 

The other consideration is making sure the tires were sized correctly for the load being carried.  In my case, it was H78x14 on a 4200 lb car, or similar.  Or a similar 15" size on a similar car of similar weight.  P225/75R-15 is kind of between the old H78-15 and J78-15 size, dimensionally.  The P235/75R-15 is the old L78-15 equivalent and a little larger than the P225/75R-15 size.  Theoretically, with the larger size, probably 2psi lower would work ok.  Again, just depends upon the "feel" that difference might make in ride and such.

 

The old recommendation was to run the P Metric tires at 2psi more than what you ran in the prior tires you had that were not P Metric.  Expanding my earlier pressure bias, then, would be 32/30, under that orientation.  Most cars, back then, were 55/45 front rear weight distribution, so my pressure bias would be pretty close.

 

If you normally use 35psi in 35psi-rated tires, going down to 32psi might make for s little smoother ride and still adequately support the car's weight . . . in general.  Now, IF you're going to run 90+mph for extended periods of time, higher pressures might be better.

 

NTX5467

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Thanks for that info.

 

I recently fitted Gabriel gas shock absorbers all round, have put in new Moog poly sway bar bushes front only. Tyres were new 12 months ago, but still have few miles on them. 

 

Car came from factory with oversize whitewall and heavy duty springs and shocks.

 

The ride now is firm, almost harsh so thinking a lower tyre pressure might make for a bit more comfort. Certainly before the shockers were changed it felt softer, almost squishy at low speed over spoon drains and bigger bumps.

 

 Rear shockers were leaking on one side, fronts were old but still working.

 

Be interested to play with pressures this trip. Will try 32 up front and 30 at rear.

 

cheers Rodney ????

 

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