🚀 TRUSTALIGN - Time Attack FL5 Build Journal

[alSpeed2k]

Thanks! Was running several different compounds, depending on tyres.

What works for you with fast 200tw tires?

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[tezzasaurusrex]

What works for you with fast 200tw tires?

I found the HC-CS bite too hard for my braking style, it was engaging ABS too much. That was with RE71RS too. I ended up moving back to OEM front pads which worked far better for me

I then moved to Racing N+ (lower bite), combined with a new aero package. This seems to be working well, the aero likely masking the issue. But since I've got the Alcon BBK now I'm unable to get the same pads. I'll be trying the Endless ME22.

What I find with the FL5 (and most modern vehicles) is that the ABS is very active, as soon as it detects a hint of wheel speed discrepancy it will start pulling brake pressure away from the line. So that paired with high bite/high friction pads tends to trigger the ABS excessively. If you have supreme braking technique you could get around this issue by modulating pedal pressure upon initial application, but I don't think my driving skill is quite there.
So to work around this, I found low mu pads with a soft initial bite works well, cause it almost acts like a pedal delay valve so you don't need to modulate your initial brake pressure as much to avoid locking up.

 

[tezzasaurusrex]

Pretty close to eliminated all the bump steer out of the front axle by maxing out the caster angle afforded by the AST strut tops

Additionally, the Spoon Zero Bump steer ball joint does work for the FL5 (always listed as FK8 on most websites).

From my toe mapping, it reduces toe in from static (-15mm from OEM) ride height to full droop (+50mm from static). From static to full bump (measured up to -30mm from static ride height) I saw very little difference. Does depend on a host of other factors so YMMV.

 

[CTR]

Additionally, the Spoon Zero Bump steer ball joint does work for the FL5 (always listed as FK8 on most websites).

Would you say these should be a requirement for ANY lowered FL5? I've been thinking of picking this up to throw in during my Spoon spring install.

I know the front end is incredibly finicky with any changes so I want to counteract any negative handling introduced by lowering it.

 

[tezzasaurusrex]

Would you say these should be a requirement for ANY lowered FL5? I've been thinking of picking this up to throw in during my Spoon spring install.

I know the front end is incredibly finicky with any changes so I want to counteract any negative handling introduced by lowering it.

I wouldn't say a requirement per se, but any time you lower the vehicle you should technically try your best to recover the roll center (RC) height to account for the induced body roll from having a lowered RC.

Everything has a cause and effect though, so changing the RC height will affect the bump steer curve if nothing else is done to solve that issue too.

 

[CTR]

I read through your whole thread. Any other mods that you think would make the biggest difference to eliminate the bump steer and negative handling? Mostly a street car application but after having a bad experience with a wheel swap I'm trying to make the car feel as close to stock but just slightly lower.

 

[tezzasaurusrex]

I read through your whole thread. Any other mods that you think would make the biggest difference to eliminate the bump steer and negative handling? Mostly a street car application but after having a bad experience with a wheel swap I'm trying to make the car feel as close to stock but just slightly lower.

In my opinion, the FL5's main inherent issue is the OEM ADS damping logic. It ramps the current sent to the shocks far too aggressively to try to control body roll, which then severely affects it's ability to absorb undulations/bumps. The result is the chassis starts skating across the track pushing wide as the load on the tyre is being spiked. Fix that in the way that best suits your budget, either with a retuned ADS with a milder lateral load curve, or moving away from the OE damper entirely and onto a good set of aftermarket coilovers. Solving the ADS issue should absolutely be your main focus because it is by far the lowest hanging fruit.

The bump steer on the other hand is not of major concern on this chassis, the curves are relatively mild on most sensibly lowered set ups I've seen (~ -15 to -20mm). I see it as a tool to gain that extra last few % of handling and, if we're talking about the front axle, to help reduce front tyre temps on the track. But again, there is much more to be gained by rectifying the ADS problems

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