Should I do a CMC?

I know this has been asked a lot but im wondering if I should do a CMC for my current setup. I have Kings in the front I just installed to replace a RC 3.5" lift and the drop in height has me rubbing pretty bad on reverse turns and while off-roading.

Looks like it rubbing on the frame based (see pics). Easiest solution would be to do a CMC chop but ive also read many people saying they dont need it for 33s. I did change my tires from 285/75/16s to 255/85/16s but still rubbing, probably due to -12mm offset.

Are there any other solutions besides a CMC? Can I have an alignment shop try to align my tires more forward? Should I just grind off that one section of the frame that its rubbing on? Or just do the full CMC?

 

Your wheel offset is the culprit. Thats a very aggressive negative offset. You have dramatically increased your scrub radius vs stock. With 255 wide 33s you should be running a +20 offset or more. If you don't care about the "look" of wheel poke, you want to run as much positive offset as you can while still clearing all the steering components and UCA. You could probably get some OEM TRD OR wheels somewhat cheap. They are 16" +25 offset.

On our trucks, dropping the lift actually helps move the tire forward in the wheel well. More lift gives less cab mount clearance. I can't believe you weren't rubbing on your 285/75/16 tires but now are on your 255s.

I just dealt with this issue. I was really trying to avoid getting the CMC (just personal preference). I have 34s (more like a slighter larger than average 33) and I had 0 offset. I was rubbing the cab mount a little. I went with +20 offset wheels and now the rubbing is pretty much gone. Ever so slight rub in extreme flexing situations. If you rub in reverse you are going to rub like crazy off road.

It seems too often people just go directly to "I need a CMC" when there are other components that are causing the issue in the first place.

TLDR: much more positive wheel offset and a good high caster alignment.

 

To be fair my 285s were very worn down from use, plus the 255s increased the total width to 33.1" so it makes a little sense that they are rubbing, but I was hoping the skinnier width would counter that enough.

If I were to do new wheels at that point id rather just do the CMC as itd be cheaper than a new set of wheels. When I bought the wheels I didn't know enough about this stuff to discern that the negative offset was going to cause issues.

With that being said I barely every rubbed on the 3.5" lift with the 285s, only in extreme flexes offroad, and I still had my front mud flaps then.

 

More lift does not increase tire clearance at the cab mount. If anything, dropping the lift should have helped clear give more tire clearance.

You are talking a negligible difference in tire diameter. On brand new tires its .25" larger diameter, so only .125" increase in radius. Your tires being worn down definitely helped, but you must have been rubbing when they were new. If you weren't , then your cab mount clearance margin must have been razor thin. Width doesn't play as big of a factor as diameter and offset for cab mount clearance.

If you don't care about the CMC from a safety (debatable) or resale standpoint then go for it. You can get a set of TRD OR wheels for around 500-600 bucks. CMC will cost you about $300 or so. You could also sell your current wheels and re-coop a little more cash.

People run that tire size on stock trucks without issue and no CMC. Only minor plastic trimming. The key factor here is wheel offset.

If you haven't already seen this its a good watch:

 

Whats the frame warranty from toyota? Is it 12 years?

 

I believe so. I doubt they could say a frame problem in the back of the truck was caused by a CMC up front, but it's more ammunition for them to try and deny any warranties.

I didn't want to do a CMC simply from a resale and safety standpoint. Safety has been a very debatable (and sometimes heated) discussion, but to me you are cutting out metal that engineers designed to keep you safe and went through many crash tests and safety certifications. To be frank, people that claim it does not affect safety at all are just talking out their ass. Not saying they are wrong, but as far as I know there have not been any actual crash tests or experiments to determine if a properly done CMC is any less safe than an unmodified one.

That being said every modification we do changes the intended design and function of our trucks.

It's risk vs. reward. I would rather spend a few hundred extra bucks and fix my wheel offset instead of going for the chop. Its up to you.

 

How is your alignment? You are on the very high end wheel offsets to clear with no chop. However your swap to skinnies should of helped not make things worth even with the drop in lift. As lift will only create clearence at ride height.

 

I had it aligned after I installed the suspension, I cant remember what my numbers were though. I think I asked them to get as positive of a caster as they could like 3-4 degrees and keep the rest in spec but they couldnt get the caster that high without pulling the other things out of spec. Rides straight though so Im not out of alignment.

 

If you can, you might be better off taking it to an offroad specific shop for the alignment. With aftermarket UCAs I'm surprised they couldn't get it in spec with 3-4 caster. Do you know how many degrees of caster your UCAs add? I have Dobinsons and it adds back 3 degrees. I was able to get 3.5-4 caster while keeping camber very close to 0

 

I have the poly performance UCAs, according to their site:

• Increases caster between 2.5 and 3.5 degrees over stock
• Negative camber increased 1.5 degrees

I gotta see if I can find my alignment sheet or if I threw it out. Would increasing my caster to 3.5-4 bring the tire forward at all or help in this situation or is that more of a performance/responsiveness benefit?

 

Interesting. I have never seen a UCA advertise add negative camber. I honestly don't know if all UCAs do this and just don't advertise it. Camber is a function of caster, so I guess they must all add negative camber since we are increasing caster.

If you can find your alignment numbers that would help see where you are at.

 

Damn thats crazy

 

Go to a better alignment shop. With those ucas getting what you wanted should not be an issue.

 

I’ve got eibach stage 2r suspension about 1.5” front lift and 1.5” rear lift. I got 285/70/17s ko3 with no rub on the cab mount. I have white line UCA that increase between +2.5 and +3.5 degrees of caster and up to 1.5 degrees of negative camber. I have 0 offset methods though! I think a good alignment will help I went to a reputable shop for that I’ll attach a pic of my measurements. I did rub alil bit on the front plastic but only when it was highly articulated a heat gun quickly fixed that. Maybe u can sell ur rims to help out with some more positive offset ones. In my opinion 0 offset is a max offset for tacomas also mentioned in a latest tinker video.

 

Will a more positive caster move my tires forward?

 

Yes. This will help with your issue, but like @Daulll said those wheels are really hurting your clearance. 0 is the most your should go negative and only for wide tires. For your 255s, go with a positive offset.

You can only move the wheel forward so much with caster while keeping everything else in spec. Your biggest problem right now is scrub radius.

 

Isn't that more of a CMR (cab mount relocation) issue/thing than a CMC?

I watched a Maxx Powell YouTube video a long while back where a CMR was done on his Tundra and later it was explained that crash/crumple zones were now irreversibly modified/ruined from it.

CMC is just a little slice on the front of the frame on the Tacoma's.

https://www.tacomaworld.com/threads/3rd-gen-cmc-quick-diy.618098/

I've got 2 sets of -38 offset wheels, one of which is going to be mounted on my 2017. CMC and pinch weld mod are gonna happen sooner or later.