Does More Caster Actually Equal More Pinch Weld Clearance? (1 Viewer)

[GTV]

Just had my '07 aligned, it drove perfectly fine but was having some excessive tire wear on the outer edges up front. I thought it was a good opportunity to have some additional caster dialed in since I will be going up on tire size once these 285/70/17's are done. Theory is that will give additional pinch weld clearance, correct? The alignment shop I chose was recommended by Torfab, they don't come cheap but they do highly detailed work. They even wanted to know what my weight was and if I usually drive alone to simulate driving weight in the cab. I like that sort of attention to detail.

Anyway, after discussing caster with the tech (who was no first timer) I decided to stick with factory specs. His point was since the only way to increase caster on the front of a 100 is to move the UCA adjustment back (towards the pinch weld) that it would reduce clearance, not increase it. Makes sense to me, but there's a lot of dynamics going on that I haven't fully wrapped my head around.

What says Mud? My suspension is 100% stock AHC other than a 3/4" sensor lift and the above mentioned tires. Before and after specs:

 

[JunkCrzr89]

I agree with the tech. Also, there’s zero reason to worry about the pinch weld with the tire size you’re running. Those tires aren’t large enough diameter to ever hit the pinch weld.

 

[hoser]

Yes, more caster via UCA equals less clearance at pinch weld. I'm at 4+ caster and true 35's and it's very close. Would certainly like to move the lower control arm forward but it is a lot more work.

 

[GTV]

I agree with the tech. Also, there’s zero reason to worry about the pinch weld with the tire size you’re running. Those tires aren’t large enough diameter to ever hit the pinch weld.

For sure, I’ve got heaps of room right now but I will be upsizing in the next 10k or so, enough that I’m certain it will become a contact point.

 

[jLB]

As you shift/adjust the UCA/ball joint to the rear, for more caster, it should shift the top half of the tire towards the rear of the wheel opening, but I suspect that it would be a much smaller movement than the typical spacers, or bad wheel offsets that we currently see people do on this forum.

By raising the axle with a taller tire, wouldn’t that increase caster by moving the steering axis further in front of the vertical centerline?

Are you trying to add caster, or add clearance with caster?

 

[GTV]

Are you trying to add caster, or add clearance with caster?

The intent was to add clearance by increasing caster. I've never experienced ill effects from increasing caster so it seemed like a reasonably good idea.

 

[MongooseGA]

Mine gets aligned at an excellent race shop in Atlanta. I took it by a few weeks ago for exactly this. Was advised that basically, to add any more caster would have stated to screw with the steering and ride. So I cut my fender and pinch weld. No rubbing, steers great.

 

[suprarx7nut]

Just had my '07 aligned, it drove perfectly fine but was having some excessive tire wear on the outer edges up front. I thought it was a good opportunity to have some additional caster dialed in since I will be going up on tire size once these 285/70/17's are done. Theory is that will give additional pinch weld clearance, correct? The alignment shop I chose was recommended by Torfab, they don't come cheap but they do highly detailed work. They even wanted to know what my weight was and if I usually drive alone to simulate driving weight in the cab. I like that sort of attention to detail.

Anyway, after discussing caster with the tech (who was no first timer) I decided to stick with factory specs. His point was since the only way to increase caster on the front of a 100 is to move the UCA adjustment back (towards the pinch weld) that it would reduce clearance, not increase it. Makes sense to me, but there's a lot of dynamics going on that I haven't fully wrapped my head around.

What says Mud? My suspension is 100% stock AHC other than a 3/4" sensor lift and the above mentioned tires. Before and after specs:

View attachment 3164623

What's your planned tire size? My 295/70/17 on ET40 wheels required only minute tweaking of the liner so you might not have too much to worry about.

 

[GTV]

What's your planned tire size? My 295/70/17 on ET40 wheels required only minute tweaking of the liner so you might not have too much to worry about.

I was originally planning on 295/70's as well but tire size is a slippery slope!

 

[jLB]

The intent was to add clearance by increasing caster. I've never experienced ill effects from increasing caster so it seemed like a reasonably good idea.

Except, decreasing caster would be the way to (minimally) increase clearance at the rear of the wheel well.

Increasing caster might help, if you’re rubbing on the washer bottle in the DS front.

 

[JJ_SC]

Mine gets aligned at an excellent race shop in Atlanta. I took it by a few weeks ago for exactly this. Was advised that basically, to add any more caster would have stated to screw with the steering and ride. So I cut my fender and pinch weld. No rubbing, steers great.

I'm curious as to why you needed to cut your fenders. Seems like most people are hammering the pinch weld and adding a 1/2 bump stop or body lift. Did you cut the fenders to avoid the lift/loss of upward articulation?

Damnit, I am jonesing for 35s.

 

[MongooseGA]

I'm curious as to why you needed to cut your fenders. Seems like most people are hammering the pinch weld and adding a 1/2 bump stop or body lift. Did you cut the fenders to avoid the lift/loss of upward articulation?

Damnit, I am jonesing for 35s.

My pinch weld was flattened for 34s but that wasn't really sufficient for the 35x12.5s. I didn't want to do a body lift. Below you can see where the tire was relative to the body even after the pinch weld mod. It's actually the bottom little "scoop" that catches. If I turned the wheel a hair from where it is in this picture, that scoop caught the tire. So I cut it and the lower part of the fender and formed the cladding around to match.

 

[hoser]

I ran 35x12.5’s with 28mm offset and 2 degrees of Caster for awhile and it was fine in that area with the pinch weld knocked down and the scoop trimmed. Versus your 12mm offset, it’s 16mm of extra clearance.

 

[spressomon]

Ditto @hoser: The optimum combo when running 35's would be for matched upper and lower control arms to allow up to 4-5º of caster and decent clearance at the rear of tire-to-lower fender clearance/better centering of the wheel/tire as well as pushing the wheel center forward.

Factory caster with 35's was no-bueno on my set-up (1" body lift, but near stock suspension height); too sensitive steering/tracking at highway speeds. Having said all that...I'm at 3.6º caster and with my current General Grabber X3 295/70R18 tires ("34.3") and no interference between tire & rear lower fender area (pinch weld area).

 

[ClassyJalopy]

I am running 34.5 (295/70/18) at 2.1º caster and 1.5" spacers on stock tires. Pinch weld had to be hammered flat and the liner heated up and molded back. Was still rubbing on the washer bottle cover, so removed the cover. Stock AHC suspension with taller bump stops!

As everyone else said, you will need to take off a bit more of the pinch weld area for 35" tires or for more caster!

 

[MongooseGA]

I ran 35x12.5’s with 28mm offset and 2 degrees of Caster for awhile and it was fine in that area with the pinch weld knocked down and the scoop trimmed. Versus your 12mm offset, it’s 16mm of extra clearance.

Yup, my lower offset is definitely a factor compared to other set ups. I did try running without the spacer to see how it went and the tires actually touched the UCA.

 

[JJ_SC]

Hmmm… maybe I’m jonesing for 34s after all.

Thanks for all the info, guys. Good stuff.