I see that there is a different part number but I can't see what would be different other than axle length. I'm gonna grab the K wheels today and let you know what happens and how it changes the width. Guess maybe I should call the Associated tech guys first?

The length is different and the space between the pin hole and the end of the threads is different. I think the offset would be out of whack and you might not be able to fully tighten the wheels. I would wait until all pieces are available.

SO apparetly I am getting some chasis slap after the biggest jump on my current layout at my local track . Not to concerned about it , the layout is being changed this weekend . But their will be another big triple , their always is . Besides driving better , and downsiding the jump cleaner , what would be the set up change to prevent chasis slap ? Or would you not set up your buggy to prevent that ?

Sorry for the repetitive newbie questions . Have only had a handful of track days with my buggy .

What makes the kysosho spings so popular with this buggy . I see alot of people running them . Are they more linear than the AE springs ? More choices as far as spring rates ?

I am running FT box stock settings still . I seem to be having some traction issues at times . My rear end is looping out in the corners . I am sure the driver has something to do with it . Proabably braking and turning to hard . How could I set up my buggy to handle a more aggressive driving style ??

Can anyone with a B4.1 rear shock tower measure the distance between the two inner shock mounting holes for me, so that I buy the correct one and not an old B4 one without the new mounting position?
Measuring the inside radius to inside radius is fine, just to help identify a new B4.1 from an old B4 rear shock tower

Chassis slap comes from jumping high, and overshooting the landing. In order to totally prevent chassis slap when overshooting a jump, you would need to comletely stiffen the spings and oil in the car (rear mostly), which would make the car handle like poop everywhere else on the track. One small change you can make is go from a #2 piston in the rear, to a #3, and drop the oil wight by 2.5. That will add a little bit of pack in the rear, which will help. But, if you are WAY overshooting the landing on a super large jump, it wont necessarily keep the back end from bouncing up and spinning out on you. The key, is to practice your trigger control so you land on the downside properly.

They are more progressive, and they don't rub the shock bodies like the AE springs do. At your level, I wouldn't worry about it.

The typical solutions to this (increasing oil weight, smaller piston) would probably make your car unresponsive and loose traction. I suggest just leaving the kit suggested oil weights and pistons in it, they aren't arbitrary... AE and all of the other manufacturers (except for Losi, who if they wanted their customers to go fast would have just kept making the XXX-CR) actually puts an effort into making sure that its kit setup suggestions are good ones.

Offroad set up is about balance. Optimizing for one part of the track, or one jump/landing area, often compromises performance in all other portions of the track.

Considering you're running the box set-up and not something really "off the wall", adjusting it to try and get rid of the chassis slap isn't normally done or really a good idea IMO. Trying to adjust for the chassis slap is going to hurt the rest of the set-up more than it's going to help with the slap, IMO. Making the b4.1 less aggressive isn't something I've wanted to do so I'll let others help you with that one, other than the obvious tire choice option...

2.95" or 75mm roughly, center to center on the inner hole.

if your rear gets a little funny add 2 quarter ounce weights behind the toe in block- it sits in the rear behind the battery and holds the rear hinge pins for the arms, also add one quarter ounce weight in each of the rear triangles, If your radio has exponential dail it back to about -15 it will make the car easier to drive, set your travel or epa to 90 for throttle as well, should help alot.

New out of the box B4.1. Electronics mounted, AE weight in the rear suspension brace, .5 oz on the receiver side, and 1/4 oz on each side of the chassis in the rear triangles. No body or wing mouted.

With the kit AE green rear springs, I have them cranked all the way up to the top of the shock body. The minimum ride height I can get is 27mm which is 3mm shy from the 24 that most people seem to run.

I'm not familiar with AE springs, is it possible I got rear truck springs? Any suggestions?

Have any weight in front of the trans and behind the suspension block?

Yes

How heavy is your lipo? The springs may simply settle a little after a couple runs. I can get 24mm with silver springs and the collars all the way up, my greens were about 2-3 turns down. And I assume you're running no rebound in the shocks..?

truck rear and buggy rear springs are the same.