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Q.I have a problem with the chassis under the bumper, I usually break the chassis there, can you give me an idea how to solve this problem?
A.Firstly I assume you are using the C4.1 plastic bumper that is recessed and partially protects the chassis.
What I do is file the front of the chassis on an angle, that is chamfer off the bottom leading edge at an angle.
Then use some medium super glue to cover the front edge of the chassis, this keeps the carbon layers from delaminating.
Q. When using the taller rear hub does everyone get reduced droop. ie. the link for camber adjustment binds before the rear arm is at horizontal. It is so limiting that if I have the inner position for the link to the top I can not set neg camber (the shorter the camber link the less travel I get)
A. Using the taller rear hub (standard) the top link will bind before the arm is horizontal, this is correct.
But once all the suspension is put together and the proper geometry is set up (For example: with the top link in the middle hole on the tower, with the tower in the lower position, about 5 mm ride height and 8 to 9mm droop and about neg 1deg camber) you don't actually want the arms to be horizontal.
With the droop screws set to attain about 3 or 4mm of droop (what I usually run) the arms are no where near horizontal and hence the problem of the top links binding doesn't come into play.
Q. When do you know you have the best spring tension combo?
A. The springs will determine the total amount of chassis roll you will get.
If the car is rolling a lot it will create a lot of grip due to more weight being transferred onto the outside tyres in the turn, which is good for slippery tracks. But on grippy tracks this will decrease the corner speed and slow the 'change of direction' responsiveness. At an extreme it could even make the car traction roll.
A characteristic of too hard a spring when the track has high grip is the car seems to hop or chatter across the track when cornering.
A characteristic of too hard a spring when the track does not have sufficient grip is the car will grip initially but part way into a corner well before apex the rear end will break away suddenly and substantially.
What I aim for usually is to limit the chassis roll as much as possible by using hard springs without the car chattering or the rear end breaking away unexpectedly.
To take this to the next level, torsion bars can be used to limit the chassis roll while also running slightly softer spings than would otherwise be possible, giving more steering going into a corner, more rear grip coming out of the corner and better stability and directional responsiveness.
Q. How do I fix understeer?
A. If your car is understeering a bit and you cannot get more corner
entry steering without the rear sliding then try going to a stiffer spring
at the front and also standing the front shocks up more vertically and moving
the lower shock mount point out as far as possible.
This should give the car an aggressive and twitchy characteristic entering
the corner, also you may or may not notice a slight understeer later in the
corner but by that time it doesn't really matter as your car will have already
rotated through the apex sufficiently.
Also this method maintains rear end bite at the same time.
Q.What is the most common gearing for 12 turn motors?
A.This all depends on the tyre diameter and the car's internal gearbox ratio. Given that we are all running rubber tyres (approx 63mm dia) I'll talk ratio
instead of roll out so as to keep this straight forward.
I would suggest to start at about 7:1 ratio which is calculated as:
spur / pinion X gearbox ratio = ratio
so for example with the gear box ratio of my Corally C4.1 it would be:
90 / 24 X 1.88 = 7.05
You should start here and then gear either way depending on the resultant
top speed/acceleration trade off for the track.
Q.How does anti squat work?
A.The purpose of anti-squat is to make the rear end of the car drop
less when accelerating.
More anti-squat (i.e. 3 degress compared to 0.5 degrees) will give more
pressure initially on the rear tires as you accelerate. It will also provide
more on-power steering. The downside here is that the rear end of car will
tend to become unstable when turning into the corner.
Tip: Corally Front Shock Tower
I have now tested my new front shock tower design and found it to be rather good.
I simply took the rear shock tower and filed the bottom holes off where it
mounts to the gearbox and then used the 3rd hole up (counting the original
hole now removed) to mount it to the gearbox.
The centre section also needs to be filed so the diff pulley clears it.
I run the shocks in the inner (normal) hole on the arm and then in the second
hole in on the shock tower. I run the white spring all round and have even
tried the yellow (harder) spring on the front, normally I don't do this but
I think I have been wrong about that idea.
The stiffer the front spring the more initial response the car will have,
making it twitchier and more aggressive, even if a little mid corner understeer
is the result in theory due to the decreased total weight transfer, in reality
the car has already rotated and turned in more by this time and is ready to
straighten up out of the corner anyway.
I found this new shock configuration gives a lot more steering entering the
corner and seems to add rear end bite mid corner.