Mmm, the outdrive and bone are never parallel to begin with. Seen from above, the front diff/spool is pretty much always forward relatively to the wheel hubs. Not saying your reasoning is wrong though...

Anyway I like arm sweep too. Every time I've tried a car with 0 degree vs 1 to 2 degrees of arm sweep I've preferred the latter.

I've always thought of it in terms of reactive caster but not sure I can make a good argument to support that idea ... lol

Drive shaft angles do play a role though. The straightening effect that shafts tend to have do also create drivetrain bind and can affect the way the car rolls through a corner on power and the way it accelerates.

When the drive shaft is swept back, like most cars, this will tend to make the front end stay flatter under power, while if they are swept forward, they will make the car lift the front a bit more.

John Stranahan played around with this quite a bit a long time ago with his XXXS. I am sure you can find a bunch on it in his thread if you search for it in his XXXS tips and tricks thread. He used to say swept back was good for mod and swept forward was good for stock.

Jag to have reactive castor, the castor has to change as it compresses. In this case it does not. The outside pivot does not have an angle change under compression.

I think it does change. Imagine an extreme sweep angle.

Arms sweaped back might allow for a fraction of caster change at extremes of the suspention movement . so during corner entry and front suspention compressing it would have less caster . just just the car diving would probably affect caster more than the suspension

Yeah, I'm not sure now, having trouble visualizing it. I think it's easier to just not run arm sweep

When a car rolls into a corner the front arm sweep shortens the wheelbase on the low side of the roll and extends the wheelbase on the high side of the roll. It effectively transfers slightly more weight to the low side tire.
I run arm sweep on my tc6.1 and my t4'13. It seems to take away a little initial turn in but make up for it by turning better in the middle and out especially on power.

Don't most full scale cars have front arm sweep?

ok so i get how it all works now,thanks guys
however,i have a t4 14 ,when adjusting the eccentric bushings should i make the track wider,05mm on the ff?
or narrower 05mm on the fr?
for now i went narrower 0.5mm on the fr

No, typical sweep is slightly more narrow at the rear. If you make it narrower at the front you may get results opposing that of which folks generally use sweep for. With the pins more narrow forward of the arms you'll almost certainly encounter a more abrupt turn-in and a tighter exit (all other settings being equal of course).

thats not what i meant,read the post again,i asked should i go wider at the ff or narrower at the fr,i went for a .5mm reduction in track width as opposed to a .5mm wider track which the ff would give

I think you should be widening the front to increase front track width.
Widening will have the same effect as sweep reducing initial steering. I suppose this would compliment the sweep change, rather than counter react it.

I see. I misunderstood the post.

No need to be condescending. I've done nothing but try to be helpful and open minded in this thread.

I can't see 0.5 deg sweep having much impact on the bind effect, perhaps if you had 45 deg. My understanding of the theory is that sweep does increase castor as the car rolls into the corner because the arm is not hinging in a horizontal plane relative to the track.

On the track sweep makes the car steer more "round" in corners. I notice this mostly in on-power situations the sweep can help link together a few apexes rather than driving from apex to apex. I've also heard this described as helping "get the car into the corner".

Widening the FF vs narrowing the FR rear will depend on what you are trying to achieve. If you widen the FF block the track width increases and so does the shock angle, so you will get more skate on the way into the corner. Narrowing the FR block will keep the shock angle the same but narrow the track width and in my testing this gives more overall steering but can make the car too darty. Whichever way you do it ensure you reset check front camber and toe

And droop, and ride height...

-Mike