Setup Advice — HamiltonRC

The foundation

Roll centre

The roll centres (RC) are the foundation of the car, and the entire setup is built around them. Changing the RC balance will require you to re-work the setup around the new foundation.

High RC — "on the track"There is a jacking effect, which raises the car up as it corners. Entering a corner too fast — or cornering too fast on power — can cause the car to "jack up" and flip over. The benefit is more initial grip and a higher peak of traction, so on loose tracks you can gain response and speed with a higher RC.

Low RC — "in the track"Low jacking effect, or even one pushing the chassis down into the track. Enter or power through a corner too fast and the car rolls down towards the track — it feels "in the track" and safe to drive. The downside is less initial grip and less response, with more overall grip: a safer, smoother feel. On low grip this can make the car too lazy, or cause it to fishtail when accelerating.

Ways to adjust the RC

Upper link angle — the main balance adjustment. A larger angle (lower on tower and/or higher on hub) raises the RC; a smaller angle approaching parallel (higher on tower and/or lower on hub) lowers it. A higher angle has more initial grip and is more on the track; a smaller angle has more overall grip and is more in the track.
Lower arm height — the other main balance adjustment. A higher arm raises the RC — more initial grip, more on the track. A lower arm lowers the RC — more overall grip, more in the track.
Upper link length — a minor RC change. Better to think of link length as tuning how fast the car responds: short links are more responsive (faster roll and load transfer), long links are calmer (slower roll and load transfer). Use it to fine-tune response speed after the RCs are set.
Axle height — changes the RC, but think of it this way: a lower axle height has more initial grip, a higher axle height has more overall grip. Use it to fine-tune initial vs. overall grip after the RCs are set.
Upper arm height (keeping the same angle) — a minor RC effect. A lower link height has more initial grip, a higher link height has more overall grip. Fine-tune with this after the RCs are set.

Order of operations: set the RCs with upper link angle and inside lower-arm height, front and rear. Then fine-tune initial vs. overall grip and response speed with link length, axle height and link height.

Roll centre balance

Balancing the front-to-rear RC relationship is important. A general rule of thumb you can follow:

Low front · high rear: the front end has smooth initial steering, good steering mid-corner and natural rotation. As you get on power the rear grips and supports the car while the front pushes slightly. This tends to be easier to drive — initial steering is smooth, the risk of flipping is lower, and the rear grips on power.

High front · low rear: the front has good response into the corner and less steering mid-corner, but the car rotates as the rear rolls. On power you have to be careful not to overload the soft rear — the car wants to keep turning out of the corner, and on a loose track the rear can fishtail. Harder to drive, but it can be very fast: responsive into corners, and it steers a lot from mid-corner to exit.

Whichever direction you choose, you then adjust the initial vs. overall grip and the "timing" of load transfer on each end around the RC balance with all the setup features of the car. You mainly set the RC balance with upper link angle and inside lower-arm height, front and rear, then adjust initial vs. overall grip with link length and axle height.

Keeping the balance: once you have a good balance, adjusting both front and rear RCs together — raising or lowering links or arms front and rear — changes the on/in-the-track feel without affecting the balance too much.

Geometry · Upper links

Upper links — front, rear and balance

Front upper link

The front upper link adjusts the on-the-track or in-the-track feel (angle), as well as the response of the car (length or angle). The recommended starting point is middle on tower, long top on hub. We almost always run long on the hub — only go shorter there if the car is already good and you just want a bit more response.

Top hole on tower — run this if you want the car more in the track, less likely to flip over, with smoother initial steering response.
Start high on the hub (and middle or top on tower, to preference) — the smoothest setting with the best overall grip.
Want more initial grip and steering into corners? Keep the same in/on-the-track feel by keeping the same angle and lowering the link inside and outside.

Avoid: lowest hole on tower with highest hole on hub, and highest hole on tower with lowest hole on hub. Only run the lowest tower hole with the low hub hole (hub with insert), and the highest tower hole with the high hub hole (hub with insert).

Rear upper link

The rear upper link adjusts the same things — on/in-the-track feel (angle) and response (length or angle). The recommended starting point is middle on tower, long top on hub (3mm height shims). Length on the hub is a common setup change, as it greatly affects handling:

Shorter link on hub — adds off-power rotation mid-corner, grips and squares up faster on power. Downside: the rear can lose grip suddenly.
Longer link on hub — reduces off-power rotation mid-corner, adds grip and stability, but doesn't square up and is prone to fishtailing when accelerating.
Top hole on tower — run this if you want the car more in the track, less likely to flip over, with more mid-corner grip.

Always start with the link high on the hub (3mm height shims) — the smoothest setting with the best overall grip. If you then want more initial grip — good rear grip on corner entry, a reduction mid-corner allowing more off-power rotation, then grip again on power — keep the same in/on-the-track feel by keeping the same angle and lowering the link inside and outside.

Avoid: lowest hole on tower with highest hole on hub, except on a smooth, loose track. Never run the highest hole on tower with the lowest hole on hub — only run the highest tower hole with the high or middle hub hole.

Upper link balance

The starting setup is middle for both links on the towers, and top long on both hubs.

Same balance, different feel: raise or lower both links on the towers together. Raise for in the track and more overall grip — especially good on high-grip or edgy tracks. Lower for on the track and more initial grip — especially good on smooth, loose tracks.
Change the RC balance: raise or lower only one end, or move both in opposite directions.
The end with the less-angled link (lower RC) — less initial grip entering the corner, more grip mid-corner, and it won't grip as much on power out of the corner. That end feels softer, more in the track, and handles bumps better.
The end with the more-angled link (higher RC) — more initial grip entering the corner, a loss of grip mid-corner, then it grips again on power out of the corner. That end feels stiffer, more on the track, and catches bumps more.

Grip rule: the higher the grip, the less angle you want on the links, and the higher the overall link height. On lower grip it's a question of preference — the same links as high grip, or more angle to generate more initial grip.

Springs & damping

Spring vs. oil — what each one does

Spring is positional: it sets how much the chassis moves and where it settles under load. Oil is velocity-based: it sets how fast the suspension moves and recovers. They feel similar in a static squeeze and behave completely differently once the inputs get fast or slow — which is why you can't fix a wrong spring with oil, or a wrong oil with spring.

Pick spring for gripChoose the spring for the support and mechanical grip the surface needs.

Lightest oil that holds itThen run the lightest oil that still controls that spring through your worst landing.

Front heavier than rearIntended balance on this platform — steering support up front, compliance at the rear.

One change at a timeIsolate the variable, run 3–5 laps, read it at one corner and one landing.

Reference

Spring rate chart (in play)

Kyosho / Lutz springs used in these baselines
Spring	Rate	Wire	End	Used for
Red 81	650	1.5	Front / Rear	Low-grip front (or rear). Soft, compliant family.
Red 70	713	1.5	Front	Low-grip nitro front. Loamy / loose.
Navy Blue 72	760	1.6	Front	Softer front — less response, more grip.
Brown 72	805	1.6	Front	Medium front. The "more steering" pair for Black 86.
Dk Blue 70	821	1.5	Front	High grip — more support deep in travel.
Black 72	860	1.6	Front	High-grip front. Stiffest, most responsive.
Lt Purple 81	592	1.5	Rear	Low-grip rear. Bumpy, loamy tracks.
Brown 86	620	1.6	Rear	Medium rear — when Black feels too stiff.
Black 86	645	1.6	Rear	Medium-high rear. Medium-to-higher grip.

Note: the number is spring length (mm); the color is the rate within that family. There is no "Red 72" — 72mm is the MP11 1.6mm front family (Black / Brown / Navy Blue) only.

Platform A

MP11 — Nitro

Nitro buggy

Power through a clutch

Softer mechanical hit, engine braking on release, and a weight that drops and shifts forward as fuel burns — so the damping is a compromise across a changing car, and tends to run heavier than the electric.

How it drives differently

Power delivery is tuned at the needle and clutch, not an ESC. The hit ramps in rather than arriving instantly.
Engine braking settles the car on entry when you lift — you don't add drag brake to get it.
Fuel burn lightens the car through a run and moves the balance, so heavier, steadier damping keeps it consistent tank-to-tank.

Springs & oil

Same spring chart, front heavier than rear. A proven low-grip nitro combo is Red 70 front (713) / Red 81 rear (650) — the soft 1.5mm family for loamy, loose clay. Nitro oils run heavier than the e-buggy, and that's fine here: the clutch's softer hit, engine braking, and changing fuel weight all want more damping to stay settled.

Center / Front / Rear diff: 30k / 20k / 15k
Pistons: 5-hole VRP
Shock oil (F / R): 900 / 800
Sway bar (F / R): 2.5 / 3.0 mm
Rear droop: −3
Ride height (F / R): 24 / 26 mm

Medium-to-high grip nitro baseline. The 900 / 800 oil belongs here — it is a nitro number, not an electric one.

Race plan · Nitro · HARC

HARC Plan 2026

A four-phase race-day plan for a glued, sauced track that climbs to a blue groove. The program opens soft on the 1.5mm Red family (Red 70 / Red 81) for the fresh, loose morning and firms up as the surface comes in — start a click compliant, build from there. Target: a good cornering car with excellent front-end response and a stable rear that squares up on power and drives off.

HARC · Nitro race day

Corner the front, square the rear

Geometry is locked — anti-squat / roll-center pills and every shock mount stay put all day. With anti-squat off the table, the rear is squared up through spring, diff and droop, with one shock hole held in reserve. Front response comes from the 72-family front spring, not from geometry.

Phase 1 — build it like this (red/red soft opening)

Front / Rear spring: Red 70 / Red 81
Pistons: 5-hole VRP
Shock oil (F / R): 750 / 700
Diff (C / F / R): 25k / 15k / 12k
Ride height (F / R): 24 / 27 mm
Rear droop: −3.5

The soft 1.5mm Red pair your guide calls the loamy/loose nitro combo — Red 70 front (713), Red 81 rear (650). Build the car here in the morning; the table below is what firms up as the groove comes in.

The four phases

HARC 2026 — red/red soft opening to blue-groove mains
Parameter	P1 · Red/red	P2 · Medium	P3 · High	P4 · Blue groove
Surface	Fresh glue, loose / soft opening	Glue worked in, line forming	Defined groove, high grip	Polished blue groove, mains
Front spring	Red 70 713	Brown 72 805	Black 72 860	Black 72 860
Rear spring	Red 81 650	Black 86 645	Black 86 645	Black 86 645
Pistons	5-hole VRP	5-hole VRP	5-hole VRP	5-hole VRP
Shock oil F / R	750 / 700	875 / 800	900 / 800	950 / 875
Diff C / F / R	25 / 15 / 12	30 / 20 / 15	35 / 20 / 17	35 / 20 / 18
Ride height F / R	24 / 27	24 / 26	23.5 / 25.5	23 / 25
Rear droop	−3.5	−3	−2	−1.5

Diff oils in thousands (k). The big jump is P1 → P2: off the 1.5mm Red family onto the 1.6mm Brown/Black, oil and diffs stepping up together. Oil and diffs are an AM-build / lunch-change item; springs, ride height and droop are your quick between-round changes. Sway bar holds at the 2.5 / 3.0 baseline — not a moving part in this plan.

How each target gets met

Excellent front response — Red 70 → Brown 72 → Black 72 up front, climbing to the most responsive 72-family spring on your chart for the groove. Front oil kept from getting too heavy so the front sets quickly, ride height low for bite, and the front spring always leads the rear in rate so the car turns before it drives.
Stable rear that squares up — the rear firms by wire, not rate: Red 81 (650, 1.5mm) and Black 86 (645, 1.6mm) are the same rate, so P1 → P2 swaps the lively rear for the supportive one. From there, center diff up (25 → 35k) for smooth stable power, rear diff up (12 → 18k) so it hooks and drives off the corner, and rear droop coming out (−3.5 → −1.5) so the rear stays flat instead of squatting away. The squaring-up job done without anti-squat.
Good cornering — the rear diff stays lighter than the front the whole way, so the rotation bias never leaves even as the rear firms up for drive.

Your one geometry move: if the blue-groove mains traction-roll, or the rear still won't square up at P4, stand the rear shock up one hole. Per IS2 that keeps the rear flat and stops the outside-rear from collapsing. It is the only mount change in this plan — everything else holds. If it doesn't need it, leave it.

Locked by choice: pills and shock mounts stay put across all four phases. The rear is squared up through spring + diff + droop instead of anti-squat — slower-acting than a pill, but it keeps the car predictable round to round, which is the point on a one-day program.

Platform B

MP11e — Electric

Electric buggy

Instant, tunable torque

No clutch — linear torque from zero, smoothed by punch, drag brake and turbo. Weight is constant the whole run, so you can match the damping precisely to the spring and grip instead of running a heavy compromise. Let the ESC smooth the power; don't tame it with thick oil.

Three-tier baseline — loamy AM to blue groove mains

MP11e shock packages by grip level
Parameter	Low	Medium	High
Surface	Loamy, loose, fresh (AM)	Groove forming, mixed	Polished groove, mains
Front spring	Red 81 650	Brown 72 805	Black 72 860
Rear spring	Lt Purple 81 592	Brown 86 620	Black 86 645
Wire / family	1.5 (MP10)	1.6 (MP11)	1.6 (MP11)
Pistons	8-hole 1.2F / 1.3R	8-hole 1.3	6-hole 1.3
Oil (F / R)	500 / 400	575 / 475	650 / 550
Sway (F / R)	2.3 / 2.6	2.4 / 2.8	2.5 / 2.9

Medium oil and sway are starting interpolations — confirm at the track. Everything moves the same direction with grip: stiffer spring, less piston flow, heavier oil, more bar.

Your current setup: Brown 72 / Black 86 is the "more steering" pairing — a valid medium-high blend. Keep the springs. The only thing off is the oil: 900 / 800 is the nitro number on an electric car. Drop to 650 / 550.

What 650 / 550 feels like vs 900 / 800

Where	900 / 800 (now)	650 / 550
Loamy / rough	Deflects, skates, packs down, harsh	Follows the surface, soaks chop, more grip
Turn-in	Slow to set, lazy to rotate	Quicker transfer, sharper, more rotation
Body movement	Locked down, numb	More roll, squat, dive — feels alive
Landings	Controlled, can feel jarring	Softer; watch a slight rebound kick on big hits
If wrong	Too planted, deflecting = lost grip	If too light on a polished groove: pitchy, slow to settle

Make it one change, same springs, back-to-back. Give it three laps before judging. Same oil brand both ways or the comparison is muddy — cSt scales vary between brands.

ESC — the power levers (do these first)

Low / loose grip: drop punch, no softening — cleaner power on loose clay.
Tight technical: kill turbo. EPA 100% (below 96% disables turbo anyway), drag brake 3–5%.
On the electric car, smooth the power here before reaching for diff or geometry.

Balance levers — one change at a time

Won't rotate / pushes: step the front spring down (860 → 805 → 760), then rear roll center up, then thin the rear diff.
Traction roll / planted on exit: drop punch first, then thin rear diff, then rear roll center — not a spring fix.
Bottoming on landings: shorter / more progressive spring (Dk Blue 70) or lay the shock down — not just heavier oil.

High-grip+ options

Dk Blue 70 front (821): lower initial rate than Black 72 but more support deep in the travel — landing support without a harsher initial feel.
Brown 72 on the rear (805): front spring on the rear for more support and corner speed on the smoothest, highest-grip days.

Roll centre

Ways to adjust the RC

Roll centre balance

Upper links — front, rear and balance

Front upper link

Rear upper link

Upper link balance

Spring vs. oil — what each one does

Spring rate chart (in play)

MP11 — Nitro

How it drives differently

Springs & oil

HARC Plan 2026

Phase 1 — build it like this (red/red soft opening)

The four phases

How each target gets met

MP11e — Electric

Three-tier baseline — loamy AM to blue groove mains

What 650 / 550 feels like vs 900 / 800

ESC — the power levers (do these first)

Balance levers — one change at a time

High-grip+ options

When to move tiers