johnjw

one of the last races we did at the Ridge we had a pretty severe lockup when trailbraking. I would smoke the tire for 100 yards? Anyways I wasted that tire pretty quick.

I run an open diff (rules) so we keep the front of the car pretty compliant with no front swaybar. It helps with putting power down out of corners and keeps more grip on the inside front tire.

I know the front swaybar would help with keeping the rear from lifting under trailbraking but would like more ideas.

I was thinking along the lines of limiting droop travel in the rear (anti-dive) or stiffer springs up front.

btw the rear of our car is stupid light and I'm relocating the battery back there instead of upfront. Our scales show the RR@<400# :O

Xian

I'd look at: stiffer springs up front, less aggressive rear pads, or a bigger rear bar (to get the inside rear well and truly off the ground vs dragging along). Any of these options should help out or fix it.

rice_classic

It's tough.. do I compromise setup to keep from dragging a tire or do I potentially compromise brake setup?

I would setup the car so that it's fast and consistent. After that, I would address the dragging tire with brakes via pad choice or even a bias controller. If the problem can't be solved that way then I would go back to compromising the fast setup to solve the issue.

Pad balance has been key for me. I would change front pad compound and then immediately recognize the rears were either doing too little (because the front pads were very aggressive) or they were doing too much and I was leaving the track backwards on corner entry.

What pad are you running up front? You may be able to step up to a more aggressive compound which will require less pedal effort which means you can slow the car down the same but less pedal effort, less pressure is getting applied to rear brakes. Additionally, you can also buy the cheapest, organic rear pad compound you can find. If you're still dragging you can use a brake bias controller but if that's against the rules then as a last resort you can take a cutting wheel and cut a few grooves in the rear pads so less material is contacting the rotor face.

Somewhat unrelated:
Some of the best rear pads I've run on the CRX were the $9 Chinese special from CarQuest. I told the manager I needed the lowest quality rear pads they could find even the brand name was "Shitty brake pads". He ordered me 2 sets. When I picked them up I saw he had written "Shitty Brake Pads" in black marker on the box. I chuckled.

johnjw

Running porterfield endurance compound at all 4. No rear bar (rules). I wonder how a oe style pad will hold up. Might be worth a shot.

Running the PF pads as Hawk's only last 18hrs depending on track. PF's will last nearly 50hrs at race pace.

I'm going to up the front spring rate 50#, hard being in Montana I have no way to test until a race.

btw. Our biggest lockup was from turn 10 through to 11 @ the Ridge.

Xian

Yeah, that's way too much rear pad. I've always had good luck with the Napa/Autozonr ceramic's for the rear. They last plenty well and should be fine for enduro's.

If that doesn't work, yeah... droop limiters or higher rate springs/bump stops.

Sccacivic1997

iTrader: (2)

X2 on the napa pads

shane(showtime)

iTrader: (1)

I Found a combo of Hawk Hp Plus on the outside of the caliper and just OEM replacement ceramics on the piston side worked well for me on the rear of my EG.

rice_classic

For years my preferred rear pad was the OEM (organic) pad from the Honda dealership. Then I got lazy (and cheap) and started buying organic and/or rear pads from carquest or napa. The rear brakes do very little on our cars.

Lock up on T10/11 makes sense, as those are heavy trail braking zones and have a lot of grip.

The R4 Enduro pad is not very aggressive so you're putting more pressure on the pedal (applying more fluid/line pressure) so your rear pads are a bigger part of the equation. You should find a much less aggressive pad for the rear or change the front pads or both.

Go buy the Raybestos ST43 for the front and lockup should be reduced because you won't need to push on the pedal quite as hard, but I still suspect you'll you want an organic/ceramic pad in the rear so show up to a test day and sort it out.

dirty19

iTrader: (1)

Anyone think that maybe there is a problem in the rear?
Id check the trailing arm for cracks.
I've seen that cause rear brake lock up too.

rice_classic

Tell me more about this.

miamirice

X2

dirty19

iTrader: (1)

I've seen a few cars have cracks in one trailing arms.
The cracks were no bigger than a half inch and were located in the aft part of the trailing arm. I don't have any pictures, sorry it wasn't my car.
This caused a lockup under hard braking situations, on the affected side.
Replace trailing arm lockup disappeared.

johnjw

Our car is thoroughly prepped/inspected/adjusted. We don't have a local track so making a 900 mile trek to the Ridge/Pacific/PIR is very important to us.

Sounds like we need to try a basic rear pad. Thanks for all of the suggestions!

Still interested in the trailing arm cracks and where they might form?

Kozy.

Front bias will certainly address the problem, but even shitty brake pads will lock up that wheel if it's totally unloaded. Even getting it down, it's going to have a couple of pounds of load on it at the most, so a couple of pounds of brake force is all it can handle before it smokes up and you'll be easily generating that even with the crappest brake pads.

I'm going with a different theory. Get that inside wheel up. Right up, well clear of the tarmac. Then you can brake hard and deep, keep the outside rear working hard and not worry about smoking the inside rear up as it's not touching the tarmac whilst locked. More rear roll stiffness should do it, either stiffer rear springs or softer fronts, since you said you can't have a rear bar.

You get more front end grip as a bonus, better rotation, better brake bias for shorter stopping distances.

Adding front bias will be the opposite to all the above.

Xian

IMO and all that but I'll bet that we're looking at an instance where the outside front is already running on the bumpstops. I don't see that reducing front spring rate will substantially change (increase) front roll when the car is already bottomed out...

I think the OP is on the right track with the droop limiters. Less aggressive rear pads to delay inside rear lockup (possibly in combination with more aggressive fronts) and then droop limiters to get the rear tire up off the ground. Alternately, if you can loosen the car up enough that you don't trail brake as much, it should be faster around the track and solve the problem at the same time...

johnjw

I'd be willing to try stiffer springs in the rear but not softer up front. I don't like the whole idea of lifting the rear tire, even though its inherent to FFwd. In a sprint race I wouldn't care as much but over the course of an endurance race that tire will eventually turn to crap from lifting and coming back down to a potential flat spot. We're always chasing flatspotting the rears and having a crazy vibration during the race.

I'm gonna try some shitty pads and figure out a way to build some diy droop limiters. I'm just scared the droop limiter might be a harsh transition.

Lo-Buck EF

more front spring, more rear droop travel. its not a pad issue.

rice_classic

CHANGE EVERYTHING!

This is definitely an example of more than one way to achieve a desired outcome.

Looking forward to what works or better yet.. what combination of things work.

Kozy.

Yes, you'll get that little chirp every time the tyre comes back down, but that still much better than dragging it for the entire braking event, or basically disconnecting the rear brakes which is what you'd have to do to stop it locking up.

Is giving up 20% of your braking efficiency really an ideal solution?

hufflepuff

Having the same issue; would be interested in hearing potential resolutions. I got RR lockup in a straight line, not even trail braking (although I get it there too), so i'm starting with a less aggressive compound.

rice_classic

I have been going through this same thing this year (again damnit) after adding a splitter (only coincidental) and I have an extremely aggressive front compound (raybestos ST45).

I had been buying bargain basement ceramic and semi-metallic pads thinking they were still shitty street pads but alas, I was wrong. They both left grippy transfer layers on the rear rotors and would easily lock up the inside rear. I changed spring rates up front, shock settings, addressed rear-droop, re-lubed all suspension points, yada yada yada yada... I got to the point at ORP where I had changed the setup so many times trying to address this issue I finally got desperate and was actually taking the pads out and soaking them in oil so that I could do at least a few laps without lockup, but once the oil burn off, lock up came back. I simply couldn't drive the car at the limit.

Got home, went on Amazon and found $8 organic pads and bought new rotors. Next race weekend with no setup changes.. lock up was entirely eliminated. I could once again drive the car at the limit, attacking every braking zone, every lap. It was a wonderful to be back at 10/10ths again.

So in summary: "It's the pads stupid". I'm going to write that on the inside of my toolbox so I don't forget next time because forgetting that has cost me $$$ in tires.

donut.

Stop driving so fast

Whats the rush?