Caster Angle: BM Rub vs Bumper Rub?

[JpAdct]

Hey gang,

I'm dealing with caster issues and rubbing issues on my lifted '17. I have read and read and have always thought more positive caster meant you were moving the wheel away from the body mount. I have aftermarket UCA's and my caster is in the mid 3's, positive caster. I was hoping for more but have always been adamant about keeping my camber at 0.0. My current guy says that's the best he can get and I haven't had time to find another trustworthy shop in SE Pennsylvania.

But.....................

I recently called the manufacture of my aftermarket UCA's, no names mentioned, but they are a well respected manufacturer on this forum. Anyway, I told them all about my set up and asked how much caster they recommended to get away from the body mount rubbing, which I'm experiencing with the wheel spacers on stock Trail/TRD Off Road rims and 285's. The gentleman I spoke with told me that more positive caster moves the wheel BACK in the wheel well.

What???

I told him that went against everything I have learned from the others' experience on this forum and that I had always believed more positive caster was actually moving the wheel towards the front, away from the body mount. He told me I was incorrect and they find that all 4Runners with 285's require the BMC, which we know is not correct. Confidence lost.....

I see many 4Runners on here with less caster than I have and they are rubbing the front bumper/fender liner, not the body mount. I never put much thought into this because "all vehicles are slightly different from the factory" and most of us are running different backspacing/wheel spacers/tire widths/etc. But now I'm wondering, would less caster help my body mount rubbing?

So did I get bogus information from an employee with little knowledge or would less caster put me more towards the bumper and away from the body mount? I have removed my wheel spacers for now and am considering smaller tires, simply because of the other losses I'm experiencing with the 285's. But if I do go to 255/75 or 265/70 with my wheel spacers back on, and still have the same rubbing issues, I'm going to be less than happy since I'm already losing money on the 285's.

I love the way the 285's look with wheel spacers on, but I don't care to do the BMC when already dealing with the MPG loss and acceleration loss. Plus I'm not happy with the look without the wheel spacers. 1.25" Spidertrax by the way.

Either way, I'm still going to be looking for smaller and lighter tires as this won't see heavy off-road use until she's paid for. I'm just trying to understand what's up with this new caster theory that I've never heard before, before I drop coin on another set of tires.

Any help is appreciated, thank!


http://www.toyota-4runner.org/5th-gen-t4rs/144626-caster-angle.html

http://www.toyota-4runner.org/5th-g...g-caster-lifted-toyota-4runner-stock-uca.html

 

[wfo9]

Not sure who you spoke to.. but he is wrong.. unless he is talking about adjustable UCAs.. In that case adding caster via the UCA adjustment can move the wheel closer to the body mount... Doing the normal LCA adjustment with more + caster is moving the wheel forward.

Anyway, your problem is probably not alignment as much as scrub radius. Wheel spacers increase the fore and aft movement of the wheel as you turn.

I've never seen a 5th gen with 285s that really needs a body mount chop. Unless it has wheels or spacers that are out of bounds. A good starting point is 17x8 4.5 back spacing. That will clear the most tire with the least trimming. Same width with abot 4.0 backspacing is pushing it.. Beyond that you probably need a BMC.

What are the rims specs. Can't remember if they changed throughout the years...

 

[gm350reratliff]

The person you spoke to at whatever UCA company is partially right, at least in their world of UCAs. To gain more positive caster from the UCA, the upper ball joint actually does move towards the rear of the vehicle. However, to gain more caster from the LCAs the lower balljoint needs to move forward towards the front of the vehicle. The pic below may help explain what is happening here.

I also believe the wheel spacers is what is causing your rub. The stock trail wheels have roughly 4.5 inches of backspacing so even a 1.25" spacer will make it seem as if you are running a wheel with 3.25" of backspacing. You will have to decide if you want to trim more to keep the stance or ditch the spacers to keep from trimming.

FWIW, I'm running 285/70/17 Nitto RG's on some 17x8 wheels with 4.5" backspacing and I don't have any rubbing anywhere.

 

[JpAdct]

Thanks for the incite Friends. I agree the 1.25" wheel spacers are throwing the scrub radius off causing the rubbing on the body mount. Also, my aftermarket UCA's are not adjustable but what gm350reratliff explained does make sense now regarding the top angle actually coming back while the lower goes forward.

I'm running without wheel spacers for the time being, but I foresee smaller aggressive AT's in my future and possiblly less lift. Hopefully I can widen the stance back out with the Spidertrax then. I like these 2017 wheels too much to swap them out for a better backspacing scenario.

I might have some near new 285's Duratracs and 2" Icon rear springs coming up for sale soon. #GoingBroke

Happy Labor Day.

 

[wfo9]

Thanks for the incite Friends. I agree the 1.25" wheel spacers are throwing the scrub radius off causing the rubbing on the body mount. Also, my aftermarket UCA's are not adjustable but what gm350reratliff explained does make sense now regarding the top angle actually coming back while the lower goes forward.

I'm running without wheel spacers for the time being, but I foresee smaller aggressive AT's in my future and possiblly less lift. Hopefully I can widen the stance back out with the Spidertrax then. I like these 2017 wheels too much to swap them out for a better backspacing scenario.

I might have some near new 285's Duratracs and 2" Icon rear springs coming up for sale soon. #GoingBroke

Happy Labor Day.

Just to clarify what I meant. An alignment tech will be moving the wheel forward and therefore adding more clearance in the rear if he is adding + caster using the typical adjustments. Unless you have adjustable UCAs. At that point it is possible to actually move the wheel back while still adding caster....

Bottom line, more caster adjusted into the alignment always results in more body mount clearance when you are using a fixed UCA.

Also be aware.. alignments will move around. Plus, there is quite a bit of defection in all the bushings. So static clearance does not always equal dynamic clearance....

 

[Presa Canario]

I love the way the 285's look with wheel spacers on, but I don't care to do the BMC when already dealing with the MPG loss and acceleration loss.

Can you explain what you mean here? The way its worded you make it sound as if a BMC is going to further increase MPG loss and power loss.

 

[classicinjection]

I thought stock TE wheels where more like 4.8 backs spacing? Did they change the money in 17?

 

[dot_tom]

I ran my 2017 TRD OR wheels with 1.75" spacers and 2.5" lift with 2.5 deg of caster without any body mount issues. I had to do the fender liner mod and trim the bumper to match. Other than that, no issues.

Now I have Method NVs 17x8.5 and 4.5" backspacing with 1.75" BORA spacers and a body mount trim and no issues at all on and off road.

 

[JpAdct]

Can you explain what you mean here? The way its worded you make it sound as if a BMC is going to further increase MPG loss and power loss.

That is not what I'm saying. What I was referring to is that since I'm already regretting the mpg and acceleration loss that came with 285's, I hate to throw more money into a BMC when I'm already not happy with the current sacrifices made for only visual gains.

Since I'm not doing trails much while making huge payments, I only added 285's for aesthetics at this point. And in my opinion, 285's with stock rims need wheel spacers and in my case, this requires a BMC.


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[Presa Canario]

That is not what I'm saying. What I was referring to is that since I'm already regretting the mpg and acceleration loss that came with 285's, I hate to throw more money into a BMC when I'm already not happy with the current sacrifices made for only visual gains.

Since I'm not doing trails much while making huge payments, I only added 285's for aesthetics at this point. And in my opinion, 285's with stock rims need wheel spacers and in my case, this requires a BMC.


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I understand what you are saying. On the '16 that I had, I started with 255/75's and they were great. Then I moved up to 285/70's. I did rub a little on the body mount when at full lock. Yes, there was some MPG loss and a bit of acceleration loss. However, when I pulled the 285's off and went back to the 255's, I was never happy with the way it looked. On my new one, there was no question that I would run 285's no matter the MPG loss or the need for a BMC.

 

[83Mule]

I run 275's with 4.0 caster and no rubbing. SPC UCA's. Put spacers on and had to do a BMC or adjust some caster out. Went with the BMC so I never need to worry about rub even when I go 285's next time I get tires. I cut a ''window'' in the mudflap so I could keep them. I really can feel the caster as it returns to center and is ''steady'' feeling compared to stock.

 

[S54MCoupe]

My plan for optimal wheel location is to use Rokmen adjustable UCA. Going to set the spacer for -1 caster and then max out my caster with the LCA eccentrics. Then adjust the heims to bring camber back in to zero. That's the plan at least, not sure if it's going to work or if it's worth the effort but I'd like to avoid cutting in to the fender mount to run big tires.

 

[JpAdct]

I ran my 2017 TRD OR wheels with 1.75" spacers and 2.5" lift with 2.5 deg of caster without any body mount issues. I had to do the fender liner mod and trim the bumper to match. Other than that, no issues.

Now I have Method NVs 17x8.5 and 4.5" backspacing with 1.75" BORA spacers and a body mount trim and no issues at all on and off road.

It's people like you Sir that I am hating and cussing right now! Ha congrats though. Wish I had gotten so lucky. I can't believe there is so much wiggle room on these trucks. I didn't come out so well.

 

[JpAdct]

My plan for optimal wheel location is to use Rokmen adjustable UCA. Going to set the spacer for -1 caster and then max out my caster with the LCA eccentrics. Then adjust the heims to bring camber back in to zero. That's the plan at least, not sure if it's going to work or if it's worth the effort but I'd like to avoid cutting in to the fender mount to run big tires.

My money is on that you'll be fine. Those with Light Racing seem to do well due to the extra adjustability, and you've gone even better.

 

[S54MCoupe]

My money is on that you'll be fine. Those with Light Racing seem to do well due to the extra adjustability, and you've gone even better.

Yeah 285's will be fine but I'm interested in stuffing 295 or 34 without having to destroy the pinch weld and cut the lower fender mounting point. I have no problem doing a BMC but I know some taco guys had water intrusion after beating the pinch weld even after sealing it up. So I'd like to avoid that if possible.

 

[wfo9]

Yeah 285's will be fine but I'm interested in stuffing 295 or 34 without having to destroy the pinch weld and cut the lower fender mounting point. I have no problem doing a BMC but I know some taco guys had water intrusion after beating the pinch weld even after sealing it up. So I'd like to avoid that if possible.

Should not be a problem. I have 305s 34.1" no rubbing at all under any conditions. BMC and I may have cut a little tab off on the lower fender mount (not enough to cause any issues though), also relocated the washer bottle to clear the front. Never touched any pinch welds...35s will be my next tire, but LT front going on first. And then I'll probably have to fiddle with the rear axle and links some to clear those as the 34s are super tight back there now when stuffed.