Tweaking Front Alignment for Towing?

[dsfra]

I have 38,000 miles on set of BFG T/A KO's, and am seeing bad wear on the fronts:





Probably 40% of the miles were while towing, causing to the front end to be somewhat unloaded. When hitched up with ~ 280 lbs of tongue weight, the 4Runner is dead level - the rear settles down on the Timbren bump stop /helper springs; when static the diff is just starting to touch the Timbrens. On pavement I run at 44 psi, and ~ 26 psi in the rocks. The rears have noticeably less tread depth remaining than the fronts, but are worn evenly.

I'm scheduled for an alignment tomorrow morning, and have chatted with one of the dealer service guys (he seemed quite knowledgeable - he actually knew what camber, caster and toe were), and we talked about tweaking the alignment to help compensate for the unloaded fronts. Sitting on the ground (with no trailer), the fronts have some amount of negative camber; up on jack stands unloaded there is a noticeable amount of positive camber. I had to do this qualitatively with a 1x6 held horizontally against the sidewalls and then a bubble level held vertically against the 1x6 - no way to easily get the degrees since I don't have a degee-calibrated level available. The bubble indication was definitive - there was an obvious and repeatable displacement of the bubble as described - no way was it uncertain or inconsistent. I'm referring to positive and negative camber in the usual sense - negative is closer at the top and further apart at the bottom, and positive is closer at the bottom and further apart at the top. Seems like people sometimes reverse the terms, maybe cuz they think it looks kool with the wheels splayed out at the bottom, and that must be "positive".

Anyhow, I'm thinking of having the camber set at the negative edge of the acceptable range (-.12 degrees +/- .75 degrees, i.e. -.63 degrees thru .87 degrees), so when I get some unloading droop on the front suspension I'll end up close to the middle of the range. Anybody played around with such things, and/or have any insights into such matters?

When the 4Runner was new it would wander all over the place on the freeway, and per lots of discussion on this forum I had the castor set to 4 degrees which really really really helped it track straight, so I know that the dealer is willing to take alignment requests - at least they were 5 years ago.

Anyone have any ideas about tweaking toe and/or castor settings w.r.t. unloaded front suspension while towing, in addition to camber? Any input would be appreciated.

And what about needing to do a zero point calibration after an alignment? What's that all about?

Oh yeah - another thing... The dealer wrote it up as a 4-wheel alignment, but I can't find any eccentrics, cams, slotted holes, etc, etc, on the rear suspension. Is there anything that's really align-able on the rear end? Are they saying that they will reference the front end alignment to the center-line of the vehicle, based on the rear end? But not really change any alignment at the rear...

Thanks!

 

[philsey]

OK, here's my .02: I think you're trying to solve a problem the wrong way.

Sure, your 4R 'sits level when hitched up', but that is not it's normal attitude. It looks level, but it's actually squatting to get there from it's normal slight rake. Setting your front alignment to a compromise of specs won't be right for loaded or unloaded - IMO.

I'd suggest doing the alignment to proper specs unloaded, and using airbags to keep the normal attitude when loaded. Toyota builds the rake into the design to accommodate temporary (my opinion) loading - your tire wear is an indication that your "level-looking" suspension needs to addressed, not the front alignment.
[MENTION=65614]Antman[/MENTION] tows a lot, with bags .... curious Jeff, what your take is.

 

[philsey]

On another note, you state 280# tongue weight ... what's your loaded trailer weigh?

 

[johnbt]

"The rears have noticeably less tread depth remaining than the fronts, but are worn evenly."

I'm curious, how many times have they been rotated in 38,000 miles? I would expect them to be worn a little more evenly.

Another thought, have you actually measured the tongue weight with all of your traveling gear loaded in the trailer?

John

 

[jwkilgore]

What johnbt said. If you rotate every 5k miles there won't be "rears" and "fronts" because you'll be constantly swapping them around.

Totally ignoring trailering, if you never rotate your tires the fronts will wear noticeably heavy on the shoulders with extra tread left in the center. Your rears will look like they are wearing straight but really that means you have more wear in the centers because most tires are manufactured with a curve.

 

[catrains]

you have 40K on these tires they look good to me. your comment front tires look bad means ya you do not rotate the tires.

I rotate my tires every 10K miles... Toyota says 5K miles. these vehicles if driven some way may require a 5K tire rotation ..

My tires are all worn the same but I do rotate and I check the air pressures every month.. when time for new tires they are all worn down the same ..

towing will cause the tires to wear faster as well as heavy loads .

where I live the tires on the curb side wear more than the driver side front rear.. this is a wear issue because of roads crap wearing the tread near the curbs.

when towing hauling loads you have to increase tire air pressures..

 

[salong53]

If you're looking to do an alignment that accommodates some rear squat, load the back end with 100-200 lbs of gear as far against the rear hatch as possible. Or even better, if you have a hitch carrier, throw 100 lbs on there before you take it to be aligned. That should give you the static stance with some rear squat and front high weight distribution to better align it for towing. Or even better, just rotate your tires more often :thumb3:

 

[dsfra]

Thanks for the feedback guys.

Sure, your 4R 'sits level when hitched up', but that is not it's normal attitude. It looks level, but it's actually squatting to get there from it's normal slight rake. Setting your front alignment to a compromise of specs won't be right for loaded or unloaded - IMO.

I'd suggest doing the alignment to proper specs unloaded, and using airbags to keep the normal attitude when loaded. Toyota builds the rake into the design to accommodate temporary (my opinion) loading - your tire wear is an indication that your "level-looking" suspension needs to addressed, not the front alignment.

I understand what you're saying, and may certainly consider air bags in the future. Three reasons I went with the Timbrens: (1) When starting to tow with the 4Runner, I was in the middle of having a ruptured disc in my lower back and didn't feel like doing anything more ambitious than the 4 bolts that hold on the Timbrens, (2) Less stuff to go wrong, and (3) Generally too lazy to install air bags.

On another note, you state 280# tongue weight ... what's your loaded trailer weigh?

Trailer is 2,900 lbs empty and dry, 3,200 lbs loaded, and as much as 3,700 lbs depending on how full the tanks are (68 gals total capacity). I know I'm maybe a little light on the tongue weight if you follow the 10%-15% formula for tongue-weight-to-total weight, but it tows just fine.

I'm curious, how many times have they been rotated in 38,000 miles? I would expect them to be worn a little more evenly.

What johnbt said. If you rotate every 5k miles there won't be "rears" and "fronts" because you'll be constantly swapping them around.

The bad wear would just be spread over 4 tires rather than 2 - still the same amount of bad wear going on, just evenly applied to the 4 tires.

you have 40K on these tires they look good to me. your comment front tires look bad means ya you do not rotate the tires.
I rotate my tires every 10K miles... Toyota says 5K miles. these vehicles if driven some way may require a 5K tire rotation ..

If you're looking to do an alignment that accommodates some rear squat, load the back end with 100-200 lbs of gear as far against the rear hatch as possible. Or even better, if you have a hitch carrier, throw 100 lbs on there before you take it to be aligned. That should give you the static stance with some rear squat and front high weight distribution to better align it for towing. Or even better, just rotate your tires more often :thumb3:

Busted - Guilty as Charged - old age and bad knees don't help. I usually wait till there is a noticeable difference in tread depth between fronts and rears and that means it's time to rotate, but I know it hasn't been every 5.000 miles. I think I've rotated 4 times in the 38,000 miles, so every 9,500 miles on average.

Anyhow, I got the alignment done, and they found that the camber was within the specified range (at -0.15 degrees) and castor was within range (at 3.1 degrees), but toe was way outta wack at -0.77 degrees left and -0.55 degrees right. They reset it at 0.1 degrees left and right, just about in the middle of the range, so we'll see what happens.

And yes, I rotated the tires when I put them back on!

 

[catrains]

my toe was also neg with 5 miles on it... that will cause the tires to wear uneven and harder to control vehicle.