Replaced front-end - Alignment Tuesday

[TMyers]

I've had an expensive weekend so far. New Dynatrac ball joints, wheel bearings, MOOG steering linkage assembly with Drag Link and Tie Rod Ends, Bilstein shocks, leveling springs and lastly, new front axle u-joints. I dreaded the ball joints, but they were a piece of cake. The originals with 140K came right out. I cleaned up the holes and used a little anti-seize on the new ones and they went right in. U-joints on the other hand were a cuss fight! It was a last-minute decision to order them and glad I did as one was completely dry and rusty inside one of the caps. Me and a helper (I was his helper!) worked 5 hours last night and about 4 more today. Sadly, I can only look at it because it needs an alignment. I measured the best I could on the new linkage assembly, but my steering wheel is slightly to the right and I'm sure the toe is out as well. Are there any special instructions I need to give the alignment shop Tuesday?

 

[Ozymandias]

Yeah, give him the famous Thuren specs.

 

[TMyers]

Yeah, give him the famous Thuren specs.

I have them printed to take with me. I would assume it will make sense to these folks.

 

[Ozymandias]

Absolutely, it's easy peasy for them to dial these numbers in.

 

[AEdelheit]

I have them printed to take with me. I would assume it will make sense to these folks.

Check the spec print out after, I have seen many shops say they aligned it to Thuren specs and when checked they were not even close. If the shop says they got the toe as close as they can but they couldnt get it to the Thuren spec run and find a confident shop.

 

[TMyers]

Check the spec print out after, I have seen many shops say they aligned it to Thuren specs and when checked they were not even close. If the shop says they got the toe as close as they can but they couldnt get it to the Thuren spec run and find a confident shop.

I had the alignment done yesterday. We compared the Thuren specs to their final numbers. My numbers are within Thuren's range but there is one contradiction in Thuren's specs for my truck. Thuren states that if you have the heavier Cummins, Caster should be set to the lower end of the range. However, their specs also state that if you are running stock or tucked wheels, you should stay to the upper end of the range. Which is it? I'm running stock 20's with a Cummins.

My final numbers were:
Left Caster 3.5 (Thuren Range 2.40 to 3.80)
Right Caster 4.0 (Thuren Range 3.40 to 4.80)
Total Toe 0.02 (Thuren Range 0.00 to 0.05)

The truck drives just fine but I'll be keeping a close eye on my tires for uneven wear.

 

[Ozymandias]

Your tires will wear just fine, you have almost Zero toe.
Caster doesn't make tire wear, and your number looks just fine to me.

The point with caster is, the more you have, the heavier the steering feels and the better it tracks straight down the road. But to much makes it feel bad, turning into corner needs to much force then. The heavy engine comes into play here. Usually the heavier the axle is loaded the less caster it has and needs to track straight.
Semi front axle can be as low as 1° or less.

 

[AEdelheit]

Your tires will wear just fine, you have almost Zero toe.
Caster doesn't make tire wear, and your number looks just fine to me.

The point with caster is, the more you have, the heavier the steering feels and the better it tracks straight down the road. But to much makes it feel bad, turning into corner needs to much force then. The heavy engine comes into play here. Usually the heavier the axle is loaded the less caster it has and needs to track straight.
Semi front axle can be as low as 1° or less.

Correct with weight playing into Caster but also wheel offset, while its poorly worded essentially wheels with less offset , stick out further , put more leverage on the steering and ball joints so require less caster then wheel with more offset such as stock.

The numbers look good, If you are happy with how it drives then run it!

 

[Ozymandias]

Correct with weight playing into Caster but also wheel offset, while its poorly worded essentially wheels with less offset , stick out further , put more leverage on the steering and ball joints so require less caster then wheel with more offset such as stock.

The numbers look good, If you are happy with how it drives then run it!

Kingpin axis should always be center of tire contact patch.
Everything else is just bad engineering.
That's what I learned in engineering class.

 

[AEdelheit]

Kingpin axis should always be center of tire contact patch.
Everything else is just bad engineering.
That's what I learned in engineering class.

Perfect engineering scenario and reality are often 2 different things ....... but yes the scrub radius should put the ball joint axis in the center of the tire, but still puts more leverage on the ball joints.

 

[Ozymandias]

Perfect engineering scenario and reality are often 2 different things ....... but yes the scrub radius should put the ball joint axis in the center of the tire, but still puts more leverage on the ball joints.

Aren't all todays Cars/Trucks built like that from factory? Just wondering, you have more experience in that field.

 

[AEdelheit]

Aren't all todays Cars/Trucks built like that from factory? Just wondering, you have more experience in that field.

From factory yes but when people install larger tires on aftermarket wheels most do not factor in scrub radius so it goes out the window. Even if the scrub radius is correct for the tire size there is still more leverage over the ball joints so less caster is needed.

 

[p-Bar]

I just had my alignment done at Ram dealership and they set to thuren spec. I am pulling my fifth wheel trailer and pulls like a dream. Tracks on road excellent. Thanks Ozy and the rest of you guys.

 

[crispyboy]

That surprises me that a dealership would use a different alignment specification from the factory manual.

 

[p-Bar]

I fought with the writer on the phone. Then when I showed up the writer I was working with said no problem.

 

[Ram4Sam]

I fought with the writer on the phone. Then when I showed up the writer I was working with said no problem.

Inquiring minds want to know.....What dealer was it....and what service writer was it......

Sam

 

[Ozymandias]

That surprises me that a dealership would use a different alignment specification from the factory manual.

A RAM dealership in Maine did mine to in 2019, no problems to use Thuren specs.

 

[p-Bar]

James at Jack Powell Ram in Escondido CA.