BMC vs UCA

[the_fornicator]

So, I searched and searched ... and since the way 4runners respond to lifts is unique for every 4runner, I figured this warranted a thread. Either that or I'm not searching hard enough.

Long story short is that I'm getting rubbing issues after putting my 285s on. I'm running bilstein 5100s in all four corners, fronts are set to the top hat (2.5") and the rear is lifted with toytech superflex springs (2"). OEM UCAs.

I just installed 285 duratracs and got some rubbing. After 15 minutes with a heat gun, I realized that wasn't going to do the trick so I just removed the front mud flaps. Still, at full lock, I only seem to be rubbing on the driver's side body mount by 2-3mm. Odd, right? Just one side?

So, my question now is how much clearance do aftermarket UCAs provide? I've included pictures to show how much rubbing there is. It's almost as if the tire just rubs against the overlapping sheet.

I'm struggling over the BMC since I live in a part of Canada (Edmonton, Alberta) that has started to use an acidic calcium chloride solution during the winter -so an acidic solvent is constantly tryign to find its way through weak points throughout the winter.

The 4runner is 4500 kms old so it's new and the BMC seems to expose things to potential rust issues so early on in it's life. People will say, "if you do it properly, there should be no rust" but you're never guaranteed anything rust -you could get some moisture trapped in the weld seam and it could rot from the inside out. The hard part is spraying the underside of the weld seam in its entirety with every solvent you want to hit it with.

Given the pictures, do you think aftermarket UCAs will provide enough clearance? Or am I forced to go with the BMC? Or, should I just cut the bit that's rubbing and don't bother welding anything back in? Just seal with it por15 and rubberized sealant?

Any suggestions or advice is appreciated. Even if it's on how to use the search button lol

 

[Big Daddy K]

If you remove the lower body mount bushing when you are doing the modification there is plenty of room to paint the backside of the plate/welds. FWIW I have aftermarket UCAs and still needed to do a BMC. Now it just rubs all the inner fenders and flares...

 

[ScarfaceT4R]

Kind of already see a spot of rust on that mount. I say do the chop & cover in paint/rubber like you suggested.

OR you may be getting rub on the driver side only because of the lean. Does your truck have a DRL?? If so, you may be able to throw a little spacer between that top plate...

1/2" Thick Single Strut Top Plate Spacer, for 05+Tacoma, 03+ 4Runner, 07+ FJ Cruiser (WHE TPS12-B or WOR TPS12A-B)

 

[the_fornicator]

Thanks guys!

I do have DRL and I definitely do have some lean going on. For the fandangling, I might as well do the chop. Thanks for your input, gents! I'll wait until it gets a touch warmer to do the chop.

 

[4runnin4mylife]

Thanks guys!

I do have DRL and I definitely do have some lean going on. For the fandangling, I might as well do the chop. Thanks for your input, gents! I'll wait until it gets a touch warmer to do the chop.

You could easily get by with high caster aftermarket UCA's if you wanted to go that route instead of chop! It's up to you, but my opinion is upgrade the UCA's and keep everything intact! Both ways work, you will be good to go either way!

 

[mrblah]

I would do aftermarket UCA's before cutting up the truck, and squeeze as much clearance as you can get away from the body mount.

The BMC does require you to be diligent for rust. I inspect it once every few weeks, because the paint doesn't last long with all the road grime and salt, etc..... It's not bad, its just one more thing you have to check periodically.

Also, if you do a BMC, you will be really tempted to get bigger tires once you see how much room you have to work with....never ends

 

[SD2808TR4]

My vote is for new UCAs. Read up a bit on BMC on this forum. Although there are pros and cons...in my own opinion I just didn't wanna chop off the metal. Costs a little more but at least you didn't chop metal.

 

[JSparky]

Right off the bat, have you had an alignment since you installed the tires?

Someone correct me if I'm wrong, but aftermarket UCA's alone won't help when it comes to rubbing on the body mount. Without an alignment they might make it worse.

Aftermarket UCA's that are caster-corrected will help restore positive caster after a lift, pushing the upper control arm-to-spindle mount "back", augmenting positive caster relative to the stock lowers. This is necessary to achieve appropriate caster for higher lifts, aiding overall alignment.

To clear the body mount for larger tires you have to shift the whole a-arm assembly forward, which may or may not be possible with an alignment. It's been echoed here a lot, but when you have an alignment performed you want to specify that your lower control arms be adjusted as far forward as possible, that's what will get you maximum clearance from the BMC. It doesn't always provide the necessary clearance though, which is why a lot of us with 2-3" of front lift, caster-corrected UCA's, and big tires also require a BMC.

To ease your concerns, there's no reason a BMC should compromise rust potential. Find a good shop that's done it before and bring your primer/paint/sealant of choice, they should be more than happy to accommodate. If not look elsewhere. There's so many other areas on a vehicle I'd be concerned about with rust... the BMC would be the last of my concerns.

From what you've shared, I'd focus on finding a shop that has done this before so they know exactly what they're doing, it'll go a long way to alleviate any concerns. Best of luck!

 

[borfoo3]

Right off the bat, have you had an alignment since you installed the tires?

Someone correct me if I'm wrong, but aftermarket UCA's alone won't help when it comes to rubbing on the body mount. Without an alignment they might make it worse.

Aftermarket UCA's that are caster-corrected will help restore positive caster after a lift, pushing the upper control arm-to-spindle mount "back", augmenting positive caster relative to the stock lowers. This is necessary to achieve appropriate caster for higher lifts, aiding overall alignment.

To clear the body mount for larger tires you have to shift the whole a-arm assembly forward, which may or may not be possible with an alignment. It's been echoed here a lot, but when you have an alignment performed you want to specify that your lower control arms be adjusted as far forward as possible, that's what will get you maximum clearance from the BMC. It doesn't always provide the necessary clearance though, which is why a lot of us with 2-3" of front lift, caster-corrected UCA's, and big tires also require a BMC.

To ease your concerns, there's no reason a BMC should compromise rust potential. Find a good shop that's done it before and bring your primer/paint/sealant of choice, they should be more than happy to accommodate. If not look elsewhere. There's so many other areas on a vehicle I'd be concerned about with rust... the BMC would be the last of my concerns.

From what you've shared, I'd focus on finding a shop that has done this before so they know exactly what they're doing, it'll go a long way to alleviate any concerns. Best of luck!

Listen to this.

UCA won't solve it. It will get you more travel (droop specifically) + more coilover clearance.

 

[mteolus]

I have SPC UCA's with 285 KO2s. No BMC.

 

[4runnin4mylife]

Right off the bat, have you had an alignment since you installed the tires?

Someone correct me if I'm wrong, but aftermarket UCA's alone won't help when it comes to rubbing on the body mount. Without an alignment they might make it worse.

Aftermarket UCA's that are caster-corrected will help restore positive caster after a lift, pushing the upper control arm-to-spindle mount "back", augmenting positive caster relative to the stock lowers. This is necessary to achieve appropriate caster for higher lifts, aiding overall alignment.

To clear the body mount for larger tires you have to shift the whole a-arm assembly forward, which may or may not be possible with an alignment. It's been echoed here a lot, but when you have an alignment performed you want to specify that your lower control arms be adjusted as far forward as possible, that's what will get you maximum clearance from the BMC. It doesn't always provide the necessary clearance though, which is why a lot of us with 2-3" of front lift, caster-corrected UCA's, and big tires also require a BMC.

To ease your concerns, there's no reason a BMC should compromise rust potential. Find a good shop that's done it before and bring your primer/paint/sealant of choice, they should be more than happy to accommodate. If not look elsewhere. There's so many other areas on a vehicle I'd be concerned about with rust... the BMC would be the last of my concerns.

From what you've shared, I'd focus on finding a shop that has done this before so they know exactly what they're doing, it'll go a long way to alleviate any concerns. Best of luck!

Listen to this.

UCA won't solve it. It will get you more travel (droop specifically) + more coilover clearance.

They absolutely make it worse if you just put them on and don't get an alignment! If you do any suspension work you need to get an alignment. I just assumed he would be doing that and he knew he would need to dial in as much positive caster as possible with the LCA. With factory UCA's i could only get +2.8 caster and with after market high caster UCA's i was able to achieve close to +5 on both sides. That amount definitely moved my wheels more than just a couple of mm which the OP is asking about. If he needs just a couple mm UCA's should give him more than enough movement of the tire forward to get away from the body mount!

High Caster UCA's with an alignment will no doubt get your wheels a couple mm forward in the wheel well and probably way more than that. Fitting 285's should be no problem fitting from the body mount. Once again, that's if you get an alignment and dial in as much positive caster as possible from your LCA. Go bigger and the body mount may still be an issue!

 

[shrub1]

I have SPC UCA's with 285 KO2s. No BMC.

Same with 285 RGs. No BMC, No rub.
I credit the SPCs.

 

[the_fornicator]

Right off the bat, have you had an alignment since you installed the tires?

Someone correct me if I'm wrong, but aftermarket UCA's alone won't help when it comes to rubbing on the body mount. Without an alignment they might make it worse.

Aftermarket UCA's that are caster-corrected will help restore positive caster after a lift, pushing the upper control arm-to-spindle mount "back", augmenting positive caster relative to the stock lowers. This is necessary to achieve appropriate caster for higher lifts, aiding overall alignment.

To clear the body mount for larger tires you have to shift the whole a-arm assembly forward, which may or may not be possible with an alignment. It's been echoed here a lot, but when you have an alignment performed you want to specify that your lower control arms be adjusted as far forward as possible, that's what will get you maximum clearance from the BMC. It doesn't always provide the necessary clearance though, which is why a lot of us with 2-3" of front lift, caster-corrected UCA's, and big tires also require a BMC.

To ease your concerns, there's no reason a BMC should compromise rust potential. Find a good shop that's done it before and bring your primer/paint/sealant of choice, they should be more than happy to accommodate. If not look elsewhere. There's so many other areas on a vehicle I'd be concerned about with rust... the BMC would be the last of my concerns.

From what you've shared, I'd focus on finding a shop that has done this before so they know exactly what they're doing, it'll go a long way to alleviate any concerns. Best of luck!

Thanks, man. Holy shit that's useful information. I haven't gotten an alignment since installing the tires. I did after the lift, but completely spaced on it after installing the tires -even if I had remembered, I wouldn't have known enough to ask about the positive caster re lower control arms.

Question due to ignorance: Say I get an alignment now after installing the 285s, when I swap in the winter set up (265/70/17 blizzaks) come winter time, would I have to get an alignment every time I switched to/from my winter set up? Or can I rock a lot of positive caster in the LCA with the stock sized tires as well?

Appreciate the help!

 

[krisztjan]

Same with 285 RGs. No BMC, No rub.
I credit the SPCs.

What size wheels are you running? I'm looking for UCAs that will accommodate my ICONS (17x8.5 0 offset 4.75 bs). I was originally looking at JBAs but feel i might run into rubbing issues..

 

[4runnin4mylife]

Thanks, man. Holy shit that's useful information. I haven't gotten an alignment since installing the tires. I did after the lift, but completely spaced on it after installing the tires -even if I had remembered, I wouldn't have known enough to ask about the positive caster re lower control arms.

Question due to ignorance: Say I get an alignment now after installing the 285s, when I swap in the winter set up (265/70/17 blizzaks) come winter time, would I have to get an alignment every time I switched to/from my winter set up? Or can I rock a lot of positive caster in the LCA with the stock sized tires as well?

Appreciate the help!

You don't need an alignment if you are just changing out tires. I would definitely get ANOTHER alignment and tell them to dial in all the positive caster they can. Not because you just swapped tires though, because you didn't know to tell them about positive caster to possibly eliminate rubbing issues. Most techs get your alignment within spec, they aren't there so move your wheel in the wheel well by adjusting caster so its a request you have to make. The lower control arms are what the alignment technician uses to adjust your settings during an alignment... that's not a special request, that's how they do it. Make sure you tell them to dial in all the positive caster they can. If they can get it where you want it, then good. If not, then i vote high caster UCA's while others vote BMC. It's up to you! Good Luck!

 

[matoolie]

You shouldn't need a BMC with your wheel specs. and tire combination, assuming your 285 are 285/70R17 and you do not have wheel spacers. Try and get another alignment.

Everyone says to get all camber possible, etc......but realize CAMBER is also only done with the lower control arm. Something has to give if they cannot get both camber and caster. You may get the caster but have positive camber and the tires will be obviously angled out at the top and have very fast tire wear. Or more neutral camber and negative caster. With 2.5" lift you SHOULD be able to get both with factory UCA's. Noted... positive camber will push the wheel further back in the wheel well and tire closer to the body mount. Aftermarket UCA's can make this even worse.

I did not need a BMC with 285/70R17 Wildpeaks on FX Pro wheels with same specs as your six shooters. This is with 3" lift and Dobinson UCA's

 

[Cajun_TRD]

I have SPC UCA's with 285 KO2s. No BMC.

Same with 285 RGs. No BMC, No rub.
I credit the SPCs.

What are y'all SPCs set at? Middle "D" setting (+2)?