Can someone explain this statement? The height of the diff has no bearing (ha) on the roll center since roll center is defined by the upper links and the lower suspension arms.

Changing the angle of the drive shaft by raising/lowering the diff may alter the efficiency of the drive train at various suspension angles (+/- chatter, for example), but it won't alter the roll center.

Your statement is correct. The things that change the roll center is the lower suspension blocks and the upper link positions.

I guess most of us missed that statement. There is no such thing as a diff roll center. It is just a diff height change, which only affects how the car lifts or squats under power due to drive shaft angles.

Thanks - I've seen that statement made a few times in various places - glad I'm on the right side for a change

Raising the diff would of course raise the center of mass, which would introduce more roll (since the R/C would have a larger radius to work around), but you are *not* changing the roll center.

Perhaps that's what he's referring to?

The difference in weight of moving the diff is not that great. However drive shaft angles will have an effect on handling. A drive shaft has a natural tendency of wanting to straighten itself out under power, so the higher it is, the more the car is going to want to straighten itself and lift the a-arms. Opposite would be true if it was lower.

AE #1401 1.3" Ti turnbuckle

What creates the straightening force? Is it the rotation, or is it torque that's applied? i.e. Would the effect be relative to car speed, or would it be relative to whether you're on power / neutral / braking?

-Mike

I think it might be a combination of both, but lean towards torque. We did a lot of testing with John Stranahan like 10 years ago on dogbone angles. From our testing, we noticed most of the "straightening tendency of the drive shaft" happens when you apply power.

The effect can be achieved by having dog bone sweep and by moving the diff up or down. Typically when the dogbones are swept forward in the front the car will push the arms down and accelerate better on power which assists in rotation (more on power steering) which is better for slower classes. When they are swept back, it makes the car mellower and easier to drive, which assists in the mod classes.

Thank you for corecting me
Anyway, when I raised the diff and spool the car did realy calm down and was alot easier to drive

Hi All,

I am a bit lost and I hope you may help me.
I just received my brand new TC6.1 Factory Team Kit. I moved from Nitro Offroad to Electric Onroad. I want to use a GM 13,5T engine (no timing). And I am now totally lost regarding the final ratio and the pinion I should use.
The kit contains the 87T Spu Gear with 48Pitch if I am right.
I am driving at an indoor carpet track.
The diagram in the instruction manual shows min. 28T for an 87T Spur Gear. Total Ratio 6.21. But I read in a couple of articels as well as in some setup sheets to go with 4.5 total ratio.
I need some help from the community.

Thanks in advance
racer_hh

The 87t gear is for running mod. You will want a smaller one for running spec classes. I run a 96t 64p spur for spec

Just to throw a little something to the mix, raising or lowering the diffs will essentially raise or lower the CG a little therefore have a direct effect on the roll center, you haven't changed the roll center through the normal suspension geometry but in a sence the roll centers effects will change due to the relation with the cars CG.

Any way on a different note, I need to "flatten" the car out with relation to my tracks infield, any pointers on wich blocks and position to run, I'm runneing 13.5 boosted and have the suspension all sorted just need to dial out the excessive roll, my mates T3 picks up a third of a second every lap through our infield and it sits nice and flat.

Short links all around.
Stand up rear shocks.
Raise roll center.
Stiffer springs.

These all come at the cost of possibly removing grip.
Try one at a time.
D.

May somebody help me on finding the right ratio (as mentioned some posts before).
TC6.1 13,5t engine and carpet track. What spur gear / engine pinion should I take.
Thanks

May somebody help me on finding the right ratio (as mentioned some posts before).
TC6.1 13,5t engine and carpet track. What spur gear / engine pinion should I take.
Thanks

Are you running boosted or blinky?
This will have a massive effect on gearing.