Xray FK 05
 

I have an FK 05 that the rear is very loose. running white springs, 2.5 degrees toe. 30 wt oil. no sway bar Please HELP!!!

I'm assuming rubber tires but we need more info. Camber, droop, piston, shock position, camber link position, tires used, where in corners it's loose.

Xray T1FK05 5,400 posts will help you dial in the car. Also the xray forum on their site has a ton of setup info.

05
 

4 holes open in the shocks, shocks in the middle and the outside on the a arms with the a arm mod to run 28mm double pink foam tires. camber link is has a 2.5 mm shim on the inside of the block and the upper hole of on the tower.

Sounds like it might be too much rear droop. It may be transfering too much weight to the front. The FK05 is overly sensitive to droop settings. Still love it though. Just out of curiousity, what are your settings in the front? White springs in the rear is way too soft. Somethings goin' on.

front
 

6 Degree caster blocks, 30 wt oil and 30 lb springs running the shock in the middle of the tower. I am not sure if I set the droop properly. I set the ride height at 5 all the way around then to set the droop I put the car 1 mm higher in the rear and set the screws until I can just slide a piece of paper under in the rear I do the same with .5 mm.

Alright. Here's my setup.

Front:
4.5 caster
Inner hinge pins middle
5mm ride height
2mm droop
Camber link down and short on tower
1mm shim under link on c-hub
shock middle on tower
non-eccentric hinge pin holders
0* toe out
3 hole spindles w/ steering link in third hole
1.5* camber
50wt Assoc shock oil no limiters
3 holes open on piston
30 or 28lb springs
small swaybar
med-tight diff
parma indigo half sauce

rear:
inner hinge pins middle w/ eccentric holders
low diff height
5mm ride height
long wheel base
down and short camber link on tower
3mm shim under link on hub
3mm droop
1* toe in
shock 1 in on tower outer on arm
4 holes open on piston
1.5 camber
40 wt assoc shock oil no limiters
dk blue springs (can't remember lb off hand)
parma magenta full sauce

That's all I got bud. Maybe check your rear diff. Good luck.

I had the same problem and I had too much rear droop. I fixed it to 2.5mm and ran awesome. Just a common mistake the springs should be good on a low grip track. I have the same setup as you and it runs great on asphalt. good luck!

also diff position in the rear makes the car toltaly different. The higher the more the rear is going to roll. The lower the less. I go low on foams and high grip tracks on rubber and medium for rubber on medium grip and high for super low grip tracks.

Yes, that is the correct way to set droop. But if the rear of the car is sliding around with 1mm droop, you don't have enough. In effect the droop you have is inhibiting the car from rolling enough side to side. I would lower the rc of the car in the rear, done by either hingepin blocks or getting the upper links more parallel to the lower arms. But I suggest lower blocks as it will give the car kickup making it slower to transfer weight to the front during corner entry, then I would go to 2mm of droop.

thanks
 

I starting looking at the car and noticed that my diff is in the low position. I will raise it up and maybe give it some more droop. I am curious to know you set your diffs? How tight is too tight and how loose is too loose? How do you know if you need to go one way or the other front or back?

I have my rear diff set in the middle position. As far as setting the diffs, if you hold both outdrives and try to spin the drive between the outdrives with your thumb, it should be hard to spin. that should get you started. You will have to make small adjustments until you find the right setting. I usally run my front diff about 1 turn more than the rear. Hope that helps.

diff
 

so is this considered a loose or a tight diff?

A loose diff will slip slightly under hard acceleration, a tight diff is on the borderline of locking it. I run my rear diff just tight enough to where is doesn't slip from a standing start. On the bench this is achieved by what Rc guy suggested but will require a little tinkering on the track. In general I run my front diff slightly tighter than the rear, for me about a half turn. These setting I would call a slightly loose rear diff and a medium front diff.

diff
 

What are the symptoms of a loose or tight front or rear diff? What does tightening/loosening the front/rear diff do for handling?