Tuesday, July 28, 2015

RE-Xtreme Drift Bible - Steering Scrub Radius

Let's have a look at the newer trends in upgrades... Why do we need narrow scrub radius steering knuckles?

Focus on the steering here... the rest of the chassis doesn't change. These items are for Full Counter 4WD Drift and/or RWD. The principle is the same.

Doesn't look to different to a stock SSG DRB actually, but what we are doing is aiming to reduce geometry changes and chassis movement through the steering range.

The old parts I'm replacing here are Overdose KPI knuckles. not a bad item, but the distance between the pivot points (ball end) and the shaft thread is about 16mm

Yokomo Option Knuckle 20mm lower & 20mm Upper

Overdose KPI 8 16mm lower, 19mm Upper

NEW Yokomo Narrow Scrub KPI 7degree 10mm Lower 14mm upper. (top picture)
NEW Yokomo Narrow Scrub KPI 0degree 10mm Lower 10mm upper.

Old style requires a pivot point closer to the chassis.
Note the lower arm extension.
Upper Pillow Ball is clearly visible.

For the same track width the Wheel offset is 5mm wider also.

So Pivot point to Axle is 19mm + offset 9mm. 

Note: These MST rims have been adjusted +9mm Offset with the rim face barely visible.

The narrow scrub items place the pivot point  further away from the chassis.
Note the larger lower extension arm.
Upper arm is covered by the wheel.

The CVD dogbone changes from 45.5 to 51mm

The wheel offset changes to 5mm and the face is easily visble.

Pivot point to Axle is 10mm + Offset 5 mm

Note: These MST rims have been adjusted +5mm Offset with the rim face clearly visible.

Compare the differences.

Top Chassis is Wide Scrub with the wheel illustrated by red lines on the bottom. 
Lower Chassis is narrow Scrub with the wheel illustrated by red lines above.

Narrow scrub has a reduced distance for and aft when the wheel turns. This is great for body clearance.
The Lift from castor also is reduced with this setting

And basically we gain more response with a faster action. The wheel doesn't move as far.

You can also see this in this picture.

So is it worth the extra money for a setup like this.

In RC, every mm is valuable. I have upgraded many parts on this DRB. When they all work together, the results are noticeable.

But having said that... I have 4 DRBs.
I still uses C-Hub with Overdose 8-8knucles on two and they perform very well.
Sure it may not be as sharp in response, but depending on the surface, sometimes twitchy and stable are contradictory for good performance.

Narrow Scrub radius may allow you to cut less from your wheel arches on the body and gain in style with aggressive castor and other settings. 

If you have already spent $2000 on your machine, why not another $100

For now the Yokomo DRB with Overdose and other tuned accessories is complete.

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