Road Active Suspension, CB Drop Needed?

I'm considering RAS for my 2021 Tundra Crewmax. At the moment it is sitting on 6112 a 1.25" and 5160 in the rear. I think I have a .5"-.75" rake. Looks great, rides great. Just have a bit of squat when I haul stuff (concrete, dirt bikes, wood, tow, camping gear, etc). So considering RAS HD.

I'm not necessarily going after a rear lift though .5" wouldn't hurt. Just looking to reduce squat when loaded up. Will a CB drop be needed? I had a lift on a tacoma years ago that had the take-off shudder and even with a CB drop I couldn't fully get rid of the shudder. I'm really hoping not to mess with the CB and a drop, so hoping someone can advise on if one will needed based on current specs.

 

But RAS will (or could) lift the rear, and thats what puts the drive line out of whack causing the shudder, right? How much lift can I expect? I see folks talking about up to an inch even, but then they have their truck on shackles or blocks and all other stuff so I cannot determine what the impact will be simply adding RAS to stock rear (other than shocks, but stock height).

 

On that note, would they work with aftermarket leaf packs and lift shackles such as the Alcans? This question has come up a couple of times in the last 2 weeks.

 

This post might help answer some of your questions.

https://www.tundras.com/threads/roadmaster-active-suspension-review.103453/

 

Duh, that makes sense. Appreciate the input.

 

Based on how I set it, RAS lifted my rear an inch and I did need to spacer the carrier bearing to stop shudder on take off. Install RAS, if you have any shudder just get a CB spacer kit.

 

Yeah. That is my concern. I get the CB Spacer kit is there to address that but back to my experience with my tacoma, I could never really get rid of it. Just trying to avoid back and forth with a spacer kit and chasing down a shudder.

 

The CB drop is no biggie and super easy ( 5 minutes) to add anytime if you need it. And you may not need it, not all Tundras get shudder when lifting the rear. Or like me, it can happen with as little as an inch of lift. For RAS, you do want the HD version. And RAS does exactly what they say it does, I have been very happy with it on my truck.

 

What size carrier bearing drop did you install to stop the shudder?

My HD RAS is set to the thicker black disc and has the shudder on takeoff. I’ve tried both the 0.75” and the 1.25” Coachbuilder carrier drop kit and STILL have this annoying shudder from takeoff to about 20 mph.

Got any ideas?

 

I actually had some aluminum spacers in leftover parts. No idea what they came from but I tend to keep little odd parts like that in case I ever need them. I would guess they are about an inch. They worked great and appeared to be very similar to any CB spacers I would purchase so I just used them. You can also use stainless washers and stack them.

I used a quarter to get my RAS HD, quarter is in between the white and black disk sizes and it raised the rear an inch.

Do you have stock height leaf springs or aftermarket with some lift or different load rating? Are you only running RAS or do you have any blocks or shackles for some lift?

 

Stock leafs with 78k miles on them. TRD rear sway bar, stock shackles and no other lift parts in rear besides RAS set to black disc, which resulted in 1.5” lift.

 

Same set up for the rear as me then. There are some dedicated threads for RAS, you could search RAS and also active suspension and find them. Could be some nuggets of into on the CB drop. There will also be some thread on CB drop in shackle lift threads here.

Look for any details/threads on CB drops for use when the rear is lifted 1.5 to 2 inch. You might find something worthwhile. My only suggestion would be to play with the amount of CB drop, maybe use some washers to try out different drop heights and see what reduces the vibration the best.

 

Thanks. I searched all RAS and driveline vibration threads I could find. I’ve been chatting with David at Coachbuilder who also finds it odd that I still have the shudder with either drop kits and stacked combinations of fender washers.

I’m going to dial back the preload on the Ras so that it’s at a quarter thickness and see what happens.