Does anybody know if the brake bias was changed between the '93 models and the '94-'95 models? I'm trying to figure out the difference between my FD's and enuttage's braking dissimilarities. The different spring rates may have a small effect on the braking delta, but I'm still having difficulty understanding what else could cause the difference.

 

What ... is this a stupid question? Or just nobody knows.

 

spring rate may have some effects, its about weight transfer too right?

Did you try to look at the service manual of 93 to that of 94/95 to see if the parameters for testing brake is different?
I know there is a brake bias valve near ABS mentioned in the manual.

Reza

 

That's essentially the whole bit, right now. I'm trying to figure out why my car bites down harder on braking ... the nose dive on my '93 R1 is much more pronounced than in enuttage's '94 (?) Touring. We have differences in suspension setup, so there's some variability in there that could be contributing ... but it's the brakes, so it's gotta be something with the brake system.

You might be onto something with the brake bias valve. I don't have my manual handy ... I take it this is an adjustable valve?

 

The only things that affect static weight transfer (like you get under constant braking, more or less) is CG height and wheelbase (braking/accel) or track width (in the turns). Sway bars affect weight transfer at one end of the car, but the total always depends on the CG and width/length, so you are just shifting it around with sway bars.

The amount of dive you get is not necessarily an indication of weight transfer. Two cars with the same ride height but very different spring rates will have the same weight transfer (or very close to it) but the stiffly sprung car will dive less.

Do the two cars in question have very different spring rates (dive) or ride height (weight transfer)?

-Max

 

Ah ... I thought it might have something to do with the swaybars, but it didn't make logical sense. So here's the comparo:

'93 R1
Koni Yellows
1993 model springs (290# F, 210# R)
Tri-point Front Swaybar (set btwn 2-3)

'94 Touring
Tokico 5-way Adjustables
1994 model springs (240# F, 200# R) - (???)
Swaybar - (unknown ... but probably stock)

The ride height may actually be higher on my car, the R1. I have the Koni's mounted on the very top perch mount. On the rears, you can see the Yellows by just sitting level with the tires.

Now that I think about it, I'm still wavering on the swaybar bit. Under straightline braking, the swaybar should have no effect on front-back/back-front weight transfer. And agreeing that the stiffer sprung car will dive less, I'm still miffed how the Koni Yellow/'93 spring combo dives more than the Tokico/'94 spring combo. If we say they're equal, then it must be the ride height. That's gotta be it.

 

are you actually measuring dive, or are you going on the subjective feel? those two setups are night and day with regard to how they will "feel".....

my point is that if the car feels like it's diving more than another, it doesn't mean that it actually is. you need to measure it somehow.

sometimes a good old fashion polaroid or digital pix of the two cars doing the same maneuver is very illuminating....you might be surprised that what you are feeling is not what you think.

the diffierent feel of the two cars under braking is unlikely to have anything to do with the brakes in this case.

good luck
fabian

 

Red, you are right: sway bars won't affect weight transfer at all under accel/brake, just when you turn. And it will only change the proportion of weight transfer front or rear. They won't change the total weight transfer at all. Weight transfer is different from body roll & pitch, too, so be careful not to confuse one for the other.

The higher ride height on your car would increase the amount of weight transfer for everything.

-Max

 

redrotorR1, did you guys play with the shock adjustments? It seems to me that with similar spring rates, ride height and weight, then you're probably looking for differences in compression damping, particularly if you are both running stock brakes & pads.

Aren't both sets of shocks at least single adjustable? And is the adjustment for compression, rebound, or both? You could map brake dive vs. shock settings on each car for fun. Maybe the compression damping curves coincide at some point for both cars. If they do, then you may be able to set them up to "dive" the same amount.

But then of course, there's the question of why you care-- what are you trying to achieve? Do you just want your car to dive less under braking?

 

I vaguely remember reading somewhere (Truechoice catalog?) that certain single adjustable Konis only vary rebound damping, while compression damping is fixed. If your car has such shocks, then you could try (as an experiment) maxing out the rebound damping on both rear shocks, which I believe would slow the rate of weight transfer to the front, and therefore may reduce dive. Try testing that against a minimum setting to see whether it makes a difference.

If I recall correctly, the Tokicos have a single adjustment ****, but it varies compression & rebound damping simultaneously...

 

fabian, it's kinda subjective but more from driving both cars. My R1 feels like it bites down harder and can brake a lot later than the Touring. I have some digipics, but I don't have a website to host them at .... you can see the difference in both the nose dive and the body roll. And since we both have identical brake setups, I figured it was either a bias issue or a suspension difference.

max, that affirms my suspicions. (If only I could post these pics!) You can see how the rear in the R1 picks up more than the Touring ... I've convinced now it's a ride height delta that's causing the braking difference.

artowar2, we did play with the shock adjustments. And you're right, Koni's are rebound-only adjustable and Tokico's have the pseudo-double-adjustables. I actually like how my R1 dives under hard braking. It's makes it easier to setup for quick transitions. But the real goal here is trying to figure out why my car brakes so much shorter than the other. Our local auto-x has a tight 180 that requires you to shutdown ... but the later you can push that braking point (with good turn-in and placement), the less time you spend down there. I have noticed that I can brake later in my car, and it has no signs of push. But I have also noticed that my car dives harder than enuttage's ... so I assume (with brakes being equal and shock settings having only secondary effects), the greater dive is what is allowing my car to brake so well.

Thanks for clearing that up, fellas.

 

redrotorR1, don't forget that your tires and alignment settings also affect your results. Your better turn-in may come from the complex combination of weight transfer helping to plant the front end plus the stiffer springs and roll bar maintaining a camber setting more ideal for your tires.

Has anyone shared any detailed testing of the bump and roll effects on the FD's alignment?

 

I would think that one of the cars may have a tired master cyl. I think that would be the amount of clamping force difference. Are all the other variables the same? Pads? Bleed? Miles on brakes? Track use?

 

Pads are the same, Hawk HP+'s. I'm using ATE Super Blue ... the other car's brake fluid is pretty old and of unknown source. (I highly doubt that it would make a difference for auto-x applications.) It's possible his pads were not bedded in properly ....

 

hmmm.....it seems here that the issue is your turn in performance rather than brake performance. is it possible that the car you think is "braking" better (judged by a later brake application) is actually just able to tolerate a higher entry speed? you should compare entry speed on the two cars. also, brake application point comparisons are only valid if you are consistently using threshold braking (which in an abs car is essentially as hard as you can push on the pedal.)

good luck
fabian