What worked–and what didn’t–on our One Lap CRX

Sponsored by
Colin
Update by Colin Wood to the Honda One Lap CRX project car
May 14, 2024 | One Lap of America, crx, One Lap, One Lap CRX

Good news: The One Lap CRX survived the 2024 Tire Rack One Lap of America Presented by Grassroots Motorsports.

Better news: The One Lap CRX finished first in its class and 11th overall in a field populated with heavy hitters like Turbo Porsche 911s, Tesla Model Plaids and ZL1 Camaros.

[An 11th place finish for the One Lap CRX | One Lap recap]

Now that we’re back home, it’s time to dig into the CRX and figure out what worked well and what didn’t so we can start planning and making improvements for next year’s One Lap.

Catch up with the action in the One Lap live thread, and learn more about the One Lap CRX in the official build thread here.

Join Free Join our community to easily find more project updates.
More like this
Comments
Andy Hollis
Andy Hollis
5/14/24 11:13 a.m.

Greetings, and welcome to the post-mortem.  As grim as that sounds, all good race engineers do what's called a "set down" after every race.  Pretty much the opposite of set-up.

 Contrary to popular belief, a car does not usually come off the track in the same state it went on. Add in some 3500 miles on some of the "best" highways in the US (I'm looking at you, Indiana), and things get beat up pretty quickly.

 

Andy Hollis
Andy Hollis
5/14/24 11:21 a.m.

Being "that tire guy", the first thing I check out is our tires.  
 

Given sizing availability constraints, we were forced into a fairly aggressive tire choice, the Yokohama ADVAN A052.  At least we were able to make a larger size fit (225/50-15), so that gave us some sidewall relief over bumps and expansion joints.  
 

But, in order to combat accelerated wear, we pumped them up to 40 psi hot for transits. That mitigated the usual shoulder wear these exhibit on track.  We might have gone a touch too far on that idea, though.
 

Here's one of our rears, sporting less tread in the middle than the outer grooves...just over 2/32 vs over 3/33.  Most of this wear came from early in the week when these were on the front. We rotated F-R mid week at NCM
 

Andy Hollis
Andy Hollis
5/14/24 11:26 a.m.

With rain moving in for many of the track sessions and transits during the second half of the week after our rotation, the fronts have much less wear than the rears.  Easily 3-4/32 across the face.  Note that these start out at 7/32, so that's half tread depth.

We were also raising the ride hight 1" at the front for all of the transits, we takes out a degree of camber and moves the toe from our track setting of slightly out to slightly in.  This was successul in giving us more even wear, as the A052 like to wear the shoulders, especially the inside under heavy braking.

 

Andy Hollis
Andy Hollis
5/14/24 11:36 a.m.

One other wear note on the rears is the heavy inside camber wear shown here.  
 

We run a LOT of rear camber on track -- 4 degrees.  This actually delivers even wear when the tire is constantly loaded.  But for transits, it focuses load in a very small area.  
 

Our original plan was to mitigate this both with higher pressures on transits (which worked) but also to raise the ride height 1" at all four corners.  
 

But in an attempt to streamline the transit setup conversion process to save valuable time, we skipped that process for the rear after the first couple of transits.  Had it remained dry all week, that may have bit us with a corded tire. 
 

Andy Hollis
Andy Hollis
5/14/24 12:16 p.m.

Moving on to brakes, the situation is not nearly as rosy.  Leaks, boiled fluid, and accelerated pad wear top the list of challenges we faced.
 

We've been running this Fastbrakes kit since the car was first built 14 years ago.  Using Wilwood parts, it combines an 11.75x.81 curved vent Spec 37 rotor ring with an aluminum hat.  Basically, the largest you can fit inside of our 6UL wheels.

Calipers are the classic Dynalite 4-pot.  Without differential piston bores, the pads do taper.  But this was easily mitigated by flipping them every day when the wheels were off to adjust ride height. 
 

Wilwood provided fresh calipers with their trick Therm-lock pistons that keep heat away from the piston seals.
 

Early in the week, we started to see fluid seeping in the vicinity of the bleeders and onto our wheels and tire sidewalls.  Each time, we went in and tightened the bleeders some more.

The issue was not the bleeder itself but the adapter that threads into the caliper.  Once we'd get one to stop leaking, the issue would move to another in a never-ending game of whack-a-mole.

By the end of the week, we still had one leaking even with a LOT of torque on it.  We survived by topping off the master cylinder each session.

We did carry a fresh spare caliper, but it's always a risk when you open up the brake hydraulic system. 

Note: Wilwood no longer markets these calipers and encouraged us to update to the newer DynaPro design, but with limited prep time we decided to go with what we knew.

Andy Hollis
Andy Hollis
5/14/24 12:37 p.m.

For track sessions, we ran Hawk DTC-80...their most aggressive pad.  Mid-week, after the brake-intensive Hedge Hollow, we swapped to a fresh set.  
 

Our first set was nearly half worn and were grooving the rotors badly. These pads are very small, so there's not a lot of friction material.  

"Asking little parts to do big things"

 

Andy Hollis
Andy Hollis
5/14/24 12:50 p.m.

The other change in plan we made was transit pads.  For the first one, 11 hours, we ran Hawk HP+ street pads.  These smoothly removed the DTC80 transfer layer, which then had to be reapplied during the out lap of the next day's first session.  
 

That turned out to be harder to execute especially on wet mornings.  So we abandoned that plan, opting instead to run our track pads on the street.  Eventually, this caught up to us with braking shudders but it was after the final track session.  
 

The problem with track pads on the street is they do not evenly remove or add to the transfer layer as they are way outside of their temp range.

Once home, we used a set of old school, high metal content Hawk Blues to fully scrape/clean off that uneven layer from our rotors.  Works a treat. 
 


 

Andy Hollis
Andy Hollis
5/14/24 2:46 p.m.

Hedge Hollow is where the brakes really became an issue.  Tom went out first that day, and there was significant brake fluid coming out of yet another bleeder adapter fitting.   We cinched that one down and refilled the master for my session.  
 

Nearing the end of my afternoon session, the pedal started to go long.  Just as I took the checker and tried to brake for Turn 1, the pedal went to the floor. Pumping got some back and I took that turn VERY wide using all of the paved runoff.  The in lap was full of brake pumping to get back.

Once back in the garage,  we did our usual routine to ready for the transit.  Again, I cranked down on the offending bleeder.  Once cool, the pedal was back solid so we left for NCM.  
 

-------

Did the fluid boil?  It was brand new Castrol SRF, so not likely but?

Given that the pedal came back we never bled it all week ("if it's not broken, don't fix it").

Curious, I did a quick bleed once home.  All fluid, no air bubbles. 
 

Andy Hollis
Andy Hollis
5/14/24 2:52 p.m.

Upshot of the whole brake thing is that we added a lot more grip capability due to the new aero, which also changed the airflow around the rotor because of the splitter tunnels.  So while we gained a ton of grip, which the brakes could then use, we also created a new problem...more heat & less cooling.  Yay race cars.

So we'll be upgrading our braking system soon.  There are now new wheels available that allow for more clearance (Clarence), and NA/NB Miatas can now fit 11.75x1.25 rotors, which cool way better.  If a Miata can fit it, we can too.  So that's our next braking move.  We'll be needing different pads, too.

Tig
Tig New Reader
5/14/24 3:19 p.m.

So, I had similar terrible experiences with the old Wilwood dynalites, including different iterations of them (another platform). Endless seeping and weeping even with new fittings into which the small bleeders thread, including 1 catastrophic failure, which was ultimately attributed to a flaw in the caliper itself (early ones were cast, later forged billet supposedly). Anyhow, I bit the bullet and went to AP (all round) and never looked back...forgot about the brakes. 
Congrats on the class win and overall placement!!

You'll need to log in to post.

Sponsored by

GRM Ad Dept

Our Preferred Partners
GCau34sD2fTDFiJefGBsDTtatr15ESsCnkSGUcV965fOcsySeoQu4IwCDd5jZ7R1