Is 5 degrees of caster too much?

[alphabeast]

Because there is a downside, the extra material is there for a reason.

This downside of which you speak is much debated and never proven. A proper BMC only removes a small portion of the BM and if plates are welded in I can't see a downside or the structure being severely compromised...

With that being said I can't prove my theory either. We just need a willing 4runner owner that has a BMC to participate in a offset front crash.. any takers?

Depending on your UCA, caster, wheel offset and width, and if your running spacers or not, you may rub with 285's. I have JBA UCA's, 3.5 caster and when I was running stock trail wheels with spacers (Spidertrax) I did rub on the passenger side in reverse with 285's. Bottom line.. your mileage may vary...

 

[wfo9]

Something doesn't really make sense. I have FN wheels FX Pro with 3" of lift, 295/70/17 Ridge Grapplers, 1* caster which is much worse than yours, and I have zero contact with the body mount. Not sure how you can be at 4* which would move your tires about 3/4" or so further forward than mine and you're rubbing? What are the specs on your wheels? Do you have wheel spacers?

That is probably because you have stock UCAs... As stated earlier, The caster number has nothing do with wheel position when comparing trucks with different UCAs. On the same truck, increasing caster without touching the UCAs will help. Anything that moves the balls further aft will cause more rubbing... and that is exactly what aftermarket UCAs do... but you typically need them to get it to drive right. The key is getting it moved back the right amount with the LCA more forward to result in good wheel placement for bigger tires along with good + caster numbers for it to feel stable and not twitchy on the road.

 

[2016 4Runner SR5]

That is probably because you have stock UCAs... As stated earlier, The caster number has nothing do with wheel position when comparing trucks with different UCAs. On the same truck, increasing caster without touching the UCAs will help. Anything that moves the balls further aft will cause more rubbing... and that is exactly what aftermarket UCAs do... but you typically need them to get it to drive right. The key is getting it moved back the right amount with the LCA more forward to result in good wheel placement for bigger tires along with good + caster numbers for it to feel stable and not twitchy on the road.

I actually plan on getting the JBA arms in the near future. The ride is quite comfortable however I chase the truck all over on a crowned road. From what I have read, that's mainly due to the 1* caster which is not a good thing. I just fear that adding the JBA arms and adjusting to the 4* mark will cause rubbing issues on the body mount.

 

[wfo9]

I actually plan on getting the JBA arms in the near future. The ride is quite comfortable however I chase the truck all over on a crowned road. From what I have read, that's mainly due to the 1* caster which is not a good thing. I just fear that adding the JBA arms and adjusting to the 4* mark will cause rubbing issues on the body mount.

Yes, 1* is crap and will make it twitch like that.
The JBAs may cause rub.. Too many factors at play to know for sure. Never touched the JBA UCAs. But I would guess it would be fine.

 

[Jetboy]

FWIW - I have JBA arms and had no problems with 285 - I even had the mud flaps on still and didn't rub. Set at about 4* caster. With the caster maxed out on OEM UCAs I could only get about 2* caster. With the JBA I have about 4* and the hub center is nearly the same location. I think the geometry is basically the same as all the other common aftermarket UCAs. By my calculation it *should* be 0.2" further back in the fender well. Either way 285/70/17's fit easily without the BMC.

With the JBA arms and 285 75 17 (34" tall) tires - I ended up having to do the BMC.

 

[Agent_Outside]

This downside of which you speak is much debated and never proven. A proper BMC only removes a small portion of the BM and if plates are welded in I can't see a downside or the structure being severely compromised...

With that being said I can't prove my theory either. We just need a willing 4runner owner that has a BMC to participate in a offset front crash.. any takers?

Depending on your UCA, caster, wheel offset and width, and if your running spacers or not, you may rub with 285's. I have JBA UCA's, 3.5 caster and when I was running stock trail wheels with spacers (Spidertrax) I did rub on the passenger side in reverse with 285's. Bottom line.. your mileage may vary...

The downside has nothing to do with structural integrity of the frame. The reason for that piece to stick out from the frame is passenger protection. Those steel protrudes out so in a severe impact the wheel/tire/suspension can not get pushed into the passenger compartment and crush your legs. That is not up for debate, that is a fact. That IS the function of the piece people cut off.

I’m not saying don’t do the modification, I’m saying understand the risk you are adding to yourself and your passengers.

 

[alphabeast]

The downside has nothing to do with structural integrity of the frame. The reason for that piece to stick out from the frame is passenger protection. Those steel protrudes out so in a severe impact the wheel/tire/suspension can not get pushed into the passenger compartment and crush your legs. That is not up for debate, that is a fact. That IS the function of the piece people cut off.

I’m not saying don’t do the modification, I’m saying understand the risk you are adding to yourself and your passengers.

Im not debating the purpose of the protruding portion of the BM, I am just debating that doing a BMC and then welding a plate will be the difference of protecting the passenger or not. Now the BMC I am referring to is the one that is illustrated by Relentless Fab and not cutting the entire end of the BM and wrapping a plate around the mount.

 

[TeeDub21]

. Either way 285/70/17's fit easily without the BMC.

Apparently not.

Goes in Monday for a BMC and plates welded in. I want it right for any situation. Some people that post photos with a 1/4”or so of clearance I guarantee you’d have problems when articulating the suspension while turning.

 

[wfo9]

Apparently not.

Goes in Monday for a BMC and plates welded in. I want it right for any situation. Some people that post photos with a 1/4”or so of clearance I guarantee you’d have problems when articulating the suspension while turning.

He is right (with the right wheels...), I've ran them without a BMC and done a few others.. never had any rubbing under any situation.

Once you go up to a true 33, or 34... The BMC becomes mandatory. But again does depend on your UCAs and alignment.... Hard to find someone that knows how to set it up right even though it is very simple.

 

[TeeDub21]

He is right (with the right wheels...), I've ran them without a BMC and done a few others.. never had any rubbing under any situation.

Once you go up to a true 33, or 34... The BMC becomes mandatory. But again does depend on your UCAs and alignment.... Hard to find someone that knows how to set it up right even though it is very simple.

Yeah, an 8” rim -0- offset probably fine. My alignment specs are perfect with 4 degrees of caster. Not sure how else you could set it up. They say every truck is different and I guess mine proves that.

 

[Mitzer]

I actually plan on getting the JBA arms in the near future. The ride is quite comfortable however I chase the truck all over on a crowned road. From what I have read, that's mainly due to the 1* caster which is not a good thing. I just fear that adding the JBA arms and adjusting to the 4* mark will cause rubbing issues on the body mount.

This is why I decided to stick with SPC UCAs with an adjustable upper ball joint design. I'm running 285/70/17 Nittos but could only get 2* of caster with stock UCAs. SPC UCAs allowed me to max the caster with the LCAs without worrying about out-of-spec camber at that point. This pushed the tires forward in the wheel well. Setting D on SPC gained me 2* of caster without touching the LCA. Once installed, I was at 4.5* of caster when we put it on the alignment machine. We dialed the caster back to slightly to 4.2* using the LCAs. Once at 4.2*, we locked down the LCAs and used the alignment machine to jack and hold under the lower control arms so we could correct the camber using the upper ball joint (this takes two people - one to manipulate the tire and the other to lock it down with the 1.25" nut on top) . The last step is to set toe.

I lurked here for weeks and looked at all the aftermarket UCAs. I felt the fixed UCA design, with built-in caster, still forced me to make all adjustments with the LCAs. Since camber must be correct to prevent tire wear, the caster setting is the compromise. I don't run my vehicle hard and off-road it much, so my opinion was the adjustable ball joint design of SPC gave me the best option to position the tire in the wheel well as I saw fit.

I have no affiliation with SPC but I have used them on my son's truck 5 years ago for the same reasons and have had good luck with them. However, you have to find an alignment shop that can READ the instructions and be willing to work with you to align them properly. Most tire shops only know to do what the alignment machine tells them to do.

All the above is FWIW. I hope you find an acceptable solution.

Mitzer

Edit: Afterwards, I did have to mod the passenger fender liner up front but I felt this was much easier and more acceptable than a BMC if the tires were rubbing up front.

 

[Jetboy]

Yeah, an 8” rim -0- offset probably fine. My alignment specs are perfect with 4 degrees of caster. Not sure how else you could set it up. They say every truck is different and I guess mine proves that.

Something is still "off" IMO. Every truck is different. But the distance from the LCA mounting tabs to the body mount is within .001 or less. This is a significant anomaly and deviates a lot from my setup that is nearly identical. My street tires are 33.01 tall and still fit with the mud flaps, but with stock wheels - and even fit with 1" spacers (I don't like spacers, but I do have a custom made 1" set)

Has your vehicle ever been in a major collision?

Can you take a picture of your lower control arm cam locations?

Also take a measurement from the hub center to the bottom of the fender.

There's really only a few possible explanations that I can think of:

Toyota changed the frame spacing (unlikely),
your wheels are offset more than stated (unlikely),
you have spacers that you're not telling us about (? I don't know you - but seems unlikely),
the alignment isn't actually 4* (Possible - either alignment shop misled you, or didn't torque cam bolts enough and it has moved.)
or the tires are not the size we think they are (? maybe just double check, they do make them in a 285 75 17 - or maybe you have 285 70 18?)
or something is bent (also possible).

I don't think anyone else has had this issue with 285 70 17s, low offset wheels, and any common UCA. It's very common. Hopefully if it's something we can help you figure out you could save a few $ on paying for a BMC you don't need. Nothing wrong IMO with doing it - but I'm guessing you're going to drop $500 on it that you'd probably rather spend on something else.

 

[zonzin]

,,,, I have JBA UCA's, 3.5 caster and when I was running stock trail wheels with spacers (Spidertrax) I did rub on the passenger side in reverse with 285's. ...

My same build and issue. I have learned to live with it. It only rubs when in reverse with wheels fully cranked. So far the only impact is the noise of the tired rubbing and the polishing of the body mount.





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[wfo9]

Yeah, an 8” rim -0- offset probably fine. My alignment specs are perfect with 4 degrees of caster. Not sure how else you could set it up. They say every truck is different and I guess mine proves that.

Still think it is most likely your alignment. Rare to find someone that does it right. You have to do multiple sweeps to get accurate numbers.... Also roll vehicle forward and back. Rare to find someone that takes the time to do it right.

 

[TeeDub21]

Still think it is most likely your alignment. Rare to find someone that does it right. You have to do multiple sweeps to get accurate numbers.... Also roll vehicle forward and back. Rare to find someone that takes the time to do it right.

Had it done at the dealer and the tech has been there 20 years. Service writer I’ve known for years said he was the best. Truck drives way better than the alignment I had my local Indy guy do.

 

[Offwidth]

For what it worth, after installing 6112/5100 1.75"/1" lift with JBA UCA got it back from alignment with 4.8/5.2 deg caster (and everything else on spec). Seems to drive just fine, and this reputable shop assured me no harm. I run 275/70, so no rubs, but may go 285/70 route on next set of tires..