2007 Tahoe wheel alignment question
February 14th, 2016, 1:50 PM
#11
very true. a vehicle can be set up to within spec and still not be set up properly. there is a lot of room for movement within the spec range. proper cross caster and cross camber are important to maintain.
February 14th, 2016, 3:05 PM
#12
for most trucks...the manufacturer lists no alignment spec's for the rear axle. If something from the rear end is causing tire wear or tracking problems ....usually, the axle or axle tube is bent or located incorrectly. Part replacement is the only fix. This is a rare condition and would take a hard direct hit for this to occur. the truck would probably be a write off. Axle tube and axles are strong and other parts would crush before the axle tube.
the thrust angle can be out, Generally, anything over 0.4* is excessive. Adding blocks to the rear leaf springs can put it out slightly sometimes....and that is why a thrust angle is important. It will align the front to match the rear thrust angle.
there is no caster adjustment for the rear on any vehicle. On the front, caster can only be indirectly calculated by measuring camber change as he steering is sweep through a 10 degree sweep right to left and then left to right. Since you can't steer the rear tires...you can' measure it and its a non factor.
the thrust angle can be out, Generally, anything over 0.4* is excessive. Adding blocks to the rear leaf springs can put it out slightly sometimes....and that is why a thrust angle is important. It will align the front to match the rear thrust angle.
there is no caster adjustment for the rear on any vehicle. On the front, caster can only be indirectly calculated by measuring camber change as he steering is sweep through a 10 degree sweep right to left and then left to right. Since you can't steer the rear tires...you can' measure it and its a non factor.
the only way anything on the rear would be out is if it was damaged or bent, the thrust alignment will only compensate to a certain extent so if there was damage on the rear axle in most cases it would still need fixed before you could do a proper adjustment on the front. I personally have never done just a front/2 wheel since its basically a waste- just like the "toe and go" believers. In my opinion if that's all you're going to do then don't even bother.
Contrary to the publics belief there is a lot more to a proper alignment then just matching the numbers up on screen so having a lot of questions is normal for someone actually trying to understand it instead of just rolling with it.
Contrary to the publics belief there is a lot more to a proper alignment then just matching the numbers up on screen so having a lot of questions is normal for someone actually trying to understand it instead of just rolling with it.
Many thanks to you both!
February 14th, 2016, 7:35 PM
#13
Administrator
February 14th, 2016, 11:51 PM
#14
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I'm going to be the odd man out. I'm from old school, find a frame shop that has a PIT alignment rack. Reading should be directly from the spindle, and not the wheel, their not all the same. Forget the so called THRUST ANGLE ALIGNMENT. have them set CASTER/CAMBER/TOE-WHEN DONE CORRECTLY, VEHICLE MUST BE DRIVEN TO CENTER THE STEERING WHEEL, then adjust 1/8" toe-in on the rack. A lot of $$$$ is wasted on alignments daily.
Look @ my Tahoe, 196k miles, never been aligned except @ factory, original shocks, just put on third set of Michelins last Fall, rotate every 5,000 miles. I take care of it, always garaged. good luck, JMHO.
David g.
Look @ my Tahoe, 196k miles, never been aligned except @ factory, original shocks, just put on third set of Michelins last Fall, rotate every 5,000 miles. I take care of it, always garaged. good luck, JMHO.
David g.
February 15th, 2016, 1:14 AM
#15
there are a lot of ways to skin a cat. I can't speak of the pit alignment method as I am not familiar with it. Some of the new clamp on tire alignment heads do give me cause for concern. I can say that all modern bodyshops have gone to conventional wheel alignment methods. Body shops need to see both front and rear angles to find hidden damage.Thrust angle is very important as the thrust angle steers the car from the rear. Secondly, if you ever drive a car with with out of spec total toe in the rear...on slippery road conditions, you can't get about 30ph or you would be in the ditch. Ignoring what the rear end is doing isn't a good idea. They certainly don't do this at the assembly plant. probably 10% of vehicles that come off the line are sent for alignment to verify correct set up.
Last edited by tech2; February 15th, 2016 at 1:17 AM.
February 15th, 2016, 1:26 AM
#16
I knew some one would catch me on that. Honestly, I have never aligned one so I don't know offhand. I have driven one gm p/u and on Nissan 240 with the hicas system and they are truly amazing systems. I speculate that only toe is adjustable in the rear and caster could not be read for the rear wheels. I will have to check into that.
February 15th, 2016, 3:14 PM
#17
Administrator
Wasn't trying to "catch" you. Just curious about those trucks as I never saw one. Suspect caster is not adjustable as there's not any reason for the rear to be as self-centering as the front which is what caster does.
February 15th, 2016, 3:27 PM
#18
were too
and yep, makes sense to me.
if ypu ever get a chance to drive one; do a high speed lane change...
Last edited by tech2; February 15th, 2016 at 3:30 PM.
February 15th, 2016, 9:06 PM
#19
Administrator
IIRC, both sets of wheels turn in the same direction at high speed so the truck steps out as opposed to low speed where they turn opposite to reduce turning circle.
April 1st, 2016, 10:14 AM
#20
UPDATE:
Finally decided to put on the new wheels and tires yesterday. I was fearing a flat on our road trip we took a week ago, and said if I make it through this short trip with no tire issues, then I'll throw on the new wheels and tires, lol. I got about 76K miles out of the Continental Ecoplus in the 275-55-20 size. I was expecting more since the treadwear rating is 740.
But anyways, the new wheels are OEM GM off of a 2015 GM truck or SUV, not sure which model, since the Silverado, Tahoe and Suburban share this wheel, but it does have the Continental Eco plus on them so I think that narrows it down to a 2015 Tahoe or Suburban. Then today got the Tahoe 4 wheel aligned. I forgot to mention I wanted a 2 wheel thrust alignment, but I did point out that the front right wheel sticks out a bit more. I was only able to talk with the tech after the alignment was done, and all he said was that both front wheels stick out a bit. I didn't want to make a big deal about it, so I let it be.
Granted, after the alignment it def. sticks out but not as much as before. I already knew that front right wheel had to much of a positive camber, it was wear out the outer edge on the tires pretty fast. It doesn't help that I drive the thing like its a corvette, lol. So I guess the camber was partly to blame for it sticking out, but it def. still is sticking out.
Here are some pics and a scan of the before and after numbers. I was surprised to see that the front right wheel camber before alignment was +.5 and is now in spec at +.3, I wouldn't think that 2-tenths of one degree could make such a difference in outer edge tire wear. I tired to get the pics of each front wheel at about the same angle so I wouldn't skew anyones opinion on whether it sticks out further or not, the angle of the pics are perfectly matched, but close enough.
Any comments on the before and after numbers? The tech said everything was in the green as far as the numbers went. I'm slightly irked about the wheel sticking out, but if the tire wears evenly I'm ok with at least until my OCD kicks in, lol.
Finally decided to put on the new wheels and tires yesterday. I was fearing a flat on our road trip we took a week ago, and said if I make it through this short trip with no tire issues, then I'll throw on the new wheels and tires, lol. I got about 76K miles out of the Continental Ecoplus in the 275-55-20 size. I was expecting more since the treadwear rating is 740.
But anyways, the new wheels are OEM GM off of a 2015 GM truck or SUV, not sure which model, since the Silverado, Tahoe and Suburban share this wheel, but it does have the Continental Eco plus on them so I think that narrows it down to a 2015 Tahoe or Suburban. Then today got the Tahoe 4 wheel aligned. I forgot to mention I wanted a 2 wheel thrust alignment, but I did point out that the front right wheel sticks out a bit more. I was only able to talk with the tech after the alignment was done, and all he said was that both front wheels stick out a bit. I didn't want to make a big deal about it, so I let it be.
Granted, after the alignment it def. sticks out but not as much as before. I already knew that front right wheel had to much of a positive camber, it was wear out the outer edge on the tires pretty fast. It doesn't help that I drive the thing like its a corvette, lol. So I guess the camber was partly to blame for it sticking out, but it def. still is sticking out.
Here are some pics and a scan of the before and after numbers. I was surprised to see that the front right wheel camber before alignment was +.5 and is now in spec at +.3, I wouldn't think that 2-tenths of one degree could make such a difference in outer edge tire wear. I tired to get the pics of each front wheel at about the same angle so I wouldn't skew anyones opinion on whether it sticks out further or not, the angle of the pics are perfectly matched, but close enough.
Any comments on the before and after numbers? The tech said everything was in the green as far as the numbers went. I'm slightly irked about the wheel sticking out, but if the tire wears evenly I'm ok with at least until my OCD kicks in, lol.
Last edited by Typerod; April 1st, 2016 at 10:18 AM.