Braking instability on new track build - Solutions?

[dogbone]

Originally Posted by tsk94

Was thinking the same thing actually. Might hold off on installing the wing and just try to see if it was ABS related issue without the module. But the wing has been ordered so later this summer we'll drive it with the wing and see how it does.

Still got 5-6 track days left so lots of time to continue testing this year

You know what else you could do: install the whole wing setup at home. Then remove the wing and leave the uprights installed. Then, during the middle of the day, you put the wing on the uprights. That way you could drive back to back sessions and feel the difference.

[tsk94]

UPDATE:

Had a track day on Sunday. Didn’t get a chance to install the wing - only came in a day or two before the event so no go on the wing. However, I did reinstall the DSC module and I’m very happy to report that the issue is basically gone! The braking is very much improved and the car was exhibiting stable braking 95% of the time. The removal of the module obviously impacted the proper functionality of the ABS. Next track day is on the 30th - the wing will be installed by then and I’ll see if that makes any noticeable differences as well.

Thanks everyone for the replies to help me with this issue.

[SYT_Shadow]

that is great news!

[OG Shark]

Originally Posted by tsk94

UPDATE:

Had a track day on Sunday. Didn’t get a chance to install the wing - only came in a day or two before the event so no go on the wing. However, I did reinstall the DSC module and I’m very happy to report that the issue is basically gone! The braking is very much improved and the car was exhibiting stable braking 95% of the time. The removal of the module obviously impacted the proper functionality of the ABS. Next track day is on the 30th - the wing will be installed by then and I’ll see if that makes any noticeable differences as well.

Thanks everyone for the replies to help me with this issue.

Awesome - good you just about got it all worked out. Interested to see if the wing gets rid of the rest.

[Richbot]

Awesome...but y tho? Is this the car sending a varying pulse in the rear lines under braking if it doesn't have a DSC signal for yaw or something?

[gmx]

I'm going to guess it actively controls fluid flow from the master and manipulates bias, potentially on the fly as well. Quite common in modern passenger cars actually.
I see a lot of cars with the same bore for each master cylinder output. So we're pushing the same hydraulic pressure to each axle. The only thing distinguishing the bias from there is each axles respective piston area, disc dimensions and pad height.

Some other manufacturers have the hydraulic circuits setup diagonally from the master/controller. In case one bore fails for whatever reason, you're not stuck with either just front or rear brakes.

[Richbot]

That was my initial thought on page 2 - Active bias/brake force distirbution doing something weird - which is whyit's annoying this problem didn't persist long enoughh for him to log what the damn thing was doing at each wheel, lol

[fsmtnbiker]

The ABS in almost all modern cars does electric brake bias, and it relies on many inputs (including yaw) to determine how to split brake pressure front and rear. Glad that reinstalling the DSC got yours happy again!

[tsk94]

Rear wing has been installed and ready to go! Next track day is next Saturday, curious to see the difference it will make.

[tdott]

Interesting.

On the track my car on stock brakes used to dance around alot under braking, I always thought that was because it was on the limits of grip. But after my M4 brake upgrade the car has become much more stable under high speed braking.

[tsk94]

Update:

Finally had a chance to run the car in the dry with the wing. Also changed to a staggered tire setup. Previously was running 275 square NT01's, now 275/295 Toyo RR's.
Well.. downforce works! I'm sure the larger rear tires are playing a role, but the car is now very stable under braking. Adding the DSC module made the car much better, but there was still a bit of wiggle sometimes from the rear under hard braking. That's now gone. There is so much more stability that trail braking is now an option - before it was a definite no-go.

Thanks everyone for their input, and those that suggested a rear wing, you were right - what a difference!

[///Mobbin]

Originally Posted by tsk94

Rear wing has been installed and ready to go! Next track day is next Saturday, curious to see the difference it will make.

Sweet track car and congrats on getting this issue sorted!

I know we'd all love to hear/see more about your car when you get a chance.

[tsk94]

Originally Posted by ///Mobbin

Sweet track car and congrats on getting this issue sorted!

I know we'd all love to hear/see more about your car when you get a chance.

Thanks
I've thought about making a build thread, the entire build from street car to where it is now was done at home by my dad and I. If people are interested that's something I could put together..

[dogbone]

Originally Posted by tsk94

Thanks
I've thought about making a build thread, the entire build from street car to where it is now was done at home by my dad and I. If people are interested that's something I could put together..

Do it! Do it! It's great when people talk about what they've done to their cars. Everyone approaches it in a different way. Lots of great ideas out there.

It's a bit of a time commitment to put a thread together that details the process of a whole build, but I have found it to be rewarding.

[dparm]

Late to this party but glad to hear you got it worked out with the DSC controller. Just goes to show how much the computers are doing behind the scenes.

To a point made earlier in this thread, one of the things that helped me with a squirmy feeling under hard/high speed braking was to adjust my technique a bit. I was coming off the gas too fast and getting onto the brakes too fast, which causing a very rapid weight transfer. It took me a while to break my old habit but when I did, I found I didn't have to fight the car quite as much when hauling it down from 120+.