Tires rub body mount after LR UCA install, will more castor help?

I searched and could not find the answer to my question.

So I put Light Racing UCA's on my truck and since I did this I get tire rub on the body mounts when I hit a small bump while turning. Here are my alignment specs.


Now my question is, if I increase my castor will that help stop this rubbing? I read some where that when you increase castor it pushes the tire more forward due to the how it adjusts from the lower control arm. Or do I have it backwards? Before the UCA's I did not have this rubbing.

 

full lock? or while turning? going over bumps at the same time?

 

yes. On my current application of 285 km2s I did not in normal driving with 2.6. I have mine set for 2.9 on both sides and have the body mount chopped.

 

More caster actually moves the tire toward the rear of the fender so you would rub more with more caster. If you look at the tire from the side, the more caster the further the tire runs behind the axis of the upper strut mount.

 

^ actually the way I understand it, more caster tilts the spindle assembly towards the rear of the fender moving the tire forward.

http://www.ozebiz.com.au/racetech/theory/align.html

but the tilt they are talking about is in relation to the spindle so if it is backwards tilt the tire would actually be forward and + caster number.

 

When adjusting the lower control arm for castor, wouldn't that move the lower control arm forward changing the axis and postion of the upper ball joint. Not moving the tire more towards the rear?

I know that when my castor was at 1.6 before my UCA's I did not have this. So the increase in castor must move it more backwards I guess.

jr114
It doesn't rub at full turn, only while turning and hitting bumps or going up my angled drive way with my wheels turned.

 

+ caster moves the tire forward, - caster moves it back. The further back it is, the better is steering is, however you need to find a compromise.

My caster is 3.4 degrees with the body mount chopped and pinched. With 285's I still rub a little on the rear mount when flexed but not bad.

In your case I'd try another degree forward from 2.3 to 3.3. Also get them to dial that camber to 0 or slightly negative.

I've tried it all. 5 degrees is too much and you'll hit the front plastic, 2.6 is too far back, so I've found the best success with 3.2-4 degrees caster.

 

Here's the deal. A good example of positive caster is the front wheels of a shopping cart. Notice how they follow the direction the cart is going. It's because the center of the wheel is behind the mounting point. If a UCA is used to get more caster it would move the ball joint toward the front of the truck. If the lower control arm is used to increase caster you would move it toward the rear of the truck.

 

I was just in the same boat as OP. I was starting to rub drivers side on the rear fenders by the pinch weld. Took it in and caster was 1.5 drivers side and 3 passenger. There was my answer. Already had the cab mounts chopped and still did the pinch weld mod since I off-road frequently. I would say chop them....you won't even notice! And get your caster at least 3.

 

well here is my set up i have the ball joints adjusted +2 foward....
and was able to obtain perfect #'s with no body mount rubbing
'with no chop"

 

There you go OP!

You guys have the same uca's?

 

Bama and BenJammn you guys said two different things. Which is correct?
Postive castor with adjustment of the lower control arm will move the tire to the rear or front of the truck. Front right? And the LR upper control arm moves it towards the rear.

 

i am at -2.0 on each side
ball joint rotated all the way to front.....
no rubbing anymore with some front fender trimming.....
and i have wheeled it many times hard....

 

This is what I was saying. Below is using the upper control arm (not stock) to adjust caster. Moving the upper mount forward increases caster. If you are using the lower control arm for adjustment, moving the control arm rearward increases caster.

 

Ok, your illustration and this one I found below prove that I am completely backwards in my thinking.

 

^No worries friend, you get the picture now

 

Caster will help but probably not eliminate the problem. High amounts of flex and lock just put the tires into the cab mounts. Best solution is to chop and box.