XRAY - Model racing cars

AD you're right, that is just the downtravel mod. I'm looking for a chart that shows the relationship between kickup and front roll center in terms of keeping those arm pins parallel.

I do understand about the shims on the upper inner pins and how to set them. However, after splitting about 4 upper inner arms (using any shim combination) it seems to me that the problem is directly related to this parallel relationship between the upper and lower arms. The pins on my CRT are parallel due to the upper and lower rear blocks (A or B) and then there are three upper roll center settings you can choose based on either A or B (I haven't broken an upper arm yet).
Perhaps the reason people have gone to an upper arm mod is that this chart does not exist in the original XB8 manual?

It looks like me and the Hudy board are going to be spending some time together today. I'll post the results if I can figure it out.

The link above is not what I am talking about. On the very last page of the XBTQ supplementary instruction manual there is a chart with the info I believe you are looking for.

I think David Joor also posted this sometime ago:

It isn't exactly spoken very clearly about how the upper arms should be positioned in relation to the kickup. So I would like to clear this up for everyone. Justin Mann and I debated over which setting was correct and I believe he won so here is the data that should give the least amount of bind to the upper arm through the compression stroke, I have found this to help keep everything functioning normally and the life of the turnbuckle is extended.
Kickup: Front Upper | Rear Upper 1down: 1up | .5up 1down: .5up | 0 1down: 0 | .5down 1down: .5down | 1down

So this is just an example, here are the rule of thumbs. Justin Mann and I built this up on the premise that 0 kickup placed the lower and upper hingepins were parallel using all 0 bushings. We also did testing on which caused the arms to be the most free (this is what we debated on, thanks Justin)

KICKUP | RULE FOR FRONT UPPER BUSHING POSITIONS 1up (3.0) | front bushing should be .5 lower than rear .5up (3.5) | front bushing should be .5 lower than rear or same 0 (4) | front bushing should be same as rear .5down (4.5) | front bushing should be .5 higher then rear or same 1down (5) | front bushing should be .5 higher then rear

Hope this helps some.

I am not familiar with the XB8R so I don't know exactly how much of this applies. I think the kickup is fixed on that model so this may not be an issue. If you upgrade to TQ or XB8 specs later it will come into play.

However, after testing last night in Daytona my car was fantastic. I softened the front shocks (from 600 to 500 with 1.4) using mugen grey springs. The car no longer feels jittery and I could move along quickly through the woops and small jumps. The front suspension now compresses easily and feels free throughout its movement.

Using 5 degrees of kickup and 16 degress of caster I had to run the front roll center 1 higher in the front than in the back to make the suspension move freely and keep the lower and upper inner pins parallel.
So at max kickup
.5up shock tower and .5 down in the rear holder produced free movement. That would be the middle roll center setting. All caster clips in front after compressing the suspension and allowing the car to set itself.
If you have been splitting arms I highly suggest you take a look at this on your car. It is most likely the source of your problems.
I am racing at Mills Pond in Florida this weekend for the FSORS warm up race and will post my results on Sunday.

Yeah you guys got it .

AD - When you adjust the caster you just need to readjust the upper arm via the CASTER clips... kick up and front roll center does not matter and will not bind on any caster set up if the upper arms are positioned correctly.

The idea is just to get the upper and lower arm parallel. The reason for splitting those arms (like you discovered) is just having the improper front roll center position. Just like Joor's article states.