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View Full Version : Evo RS: wheel lockup under braking



redvolution
12-01-2005, 12:57 PM
On an '05 RS, what happens when just one wheel locks up? How does that affects the front/rear LSDs? What does it take to stall the car when wheels lock up? I have some theorys but I wanted to throw out the question.

Planning to go play in the rain and refine my wheel-lockup sense...

Dr. Evo
12-01-2005, 01:14 PM
Well, you don't have ABS, so lockup under hard braking would be normal. LSD only effects acceleration, not braking.

earlyapex
12-01-2005, 01:30 PM
You can flat spot your tires pretty fast locking the brakes up. Get your threshold braking down.

Dr. EVO is right, LSD has nothing to do with braking, it only comes into effect on acceleration.

Not sure what you mean by what takes it to stall the car when the wheels lock up.

redvolution
12-01-2005, 02:20 PM
Ok - I understand that the diffs only act when accelerating (wasn't completely sure - now I am - thanks).

I'm well aware of flat spots (watching F1) but my question is this:
At what point will the car stall? Obviously if you lock all 4 wheels and don't depress the clutch you're hosed but what about if you lock just one or two or three wheels?

drunk monkey
12-01-2005, 02:26 PM
stall the car if one wheel is locked up? if one wheel is locked and the others are still going i would think you will go into a circle. haha.

methods4
12-01-2005, 02:27 PM
http://www.picpop.com/gallery/albums/userpics/10002/bunnypancake.jpg

earlyapex
12-01-2005, 02:33 PM
I still don't understand what you mean by stalling when the brakes lock.

Why would it stall? Are you locking all 4 of your wheels up at 5mph or something? Stop doing that.

ZK
12-01-2005, 02:47 PM
Ok - I understand that the diffs only act when accelerating (wasn't completely sure - now I am - thanks).

I'm well aware of flat spots (watching F1) but my question is this:
At what point will the car stall? Obviously if you lock all 4 wheels and don't depress the clutch you're hosed but what about if you lock just one or two or three wheels?

Huh? Locking up your wheels won't stall your car. I think you're trying to say that if the wheels lock up, it will cause the engine to stop spinning so your car stalls?

redvolution
12-01-2005, 02:52 PM
Here are some hypothetical scenarios:

1:
I'm driving in the rain and I jam on the brakes without depressing the clutch. All 4 wheels stop rotating. Presumably the car will stall.

2:
I'm driving on a partially wet road, jam on the brakes, and 3 wheels stop rotating. Does the car stall?

I know these are kind of bonehead questions but I'm trying to get an idea of the boundary conditions.

redvolution
12-01-2005, 02:53 PM
[qoute]Huh? Locking up your wheels won't stall your car. I think you're trying to say that if the wheels lock up, it will cause the engine to stop spinning so your car stalls?[/quote]

Yes - of course.

vtluu
12-01-2005, 02:55 PM
1:
I'm driving in the rain and I jam on the brakes without depressing the clutch. All 4 wheels stop rotating. Presumably the car will stall.

2:
I'm driving on a partially wet road, jam on the brakes, and 3 wheels stop rotating. Does the car stall?
In both cases, whether or not the engine stalls is the last thing you should be worrying about. :P

earlyapex
12-01-2005, 03:19 PM
Only a truly bonehead uber-panic stop would get close to having all 4 wheels lock up at speed.

Even more boneheaded would be to stay on the brakes being all locked up till your engine drops from 4k or above, unless you drive around at 1,200rpm.

You bought a car with no ABS, you need to learn how to threshold brake. If you do, then you won't have to worry about any wheel lockup.

A panic stop is a panic stop, try not to do it.

redvolution
12-01-2005, 03:30 PM
[ducking...]
I know how to threshold brake. I have 25+ car track days and ~15 motorcycle tracks under the ole' belt. I was just trying to ask a hypothetical question.

turbotiger
12-01-2005, 03:33 PM
Only a truly bonehead uber-panic stop would get close to having all 4 wheels lock up at speed.

Even more boneheaded would be to stay on the brakes being all locked up till your engine drops from 4k or above, unless you drive around at 1,200rpm.

You bought a car with no ABS, you need to learn how to threshold brake. If you do, then you won't have to worry about any wheel lockup.

A panic stop is a panic stop, try not to do it.

Oh come on, you know you've done it before. Step on the brakes and clutch at the same time, except the brakes lock up before the clutch disengages, resulting in a stalled engine. Usually involves a panic stop or spinning situation.

Oh, and if you do lock up the brakes while going straight without depressing the clutch, your engine will stall, and will start again when you release the brakes provided you are still moving.

I thought the RS's had viscous LSD and locked with speed differences no matter which direction they were rotating?

earlyapex
12-01-2005, 03:37 PM
Oh come on, you know you've done it before. Step on the brakes and clutch at the same time, except the brakes lock up before the clutch disengages, resulting in a stalled engine. Usually involves a panic stop or spinning situation.


I have only locked up all 4 on snow. Then I got off the brakes instead of doing a deer-in-the-headlights move. Then I got back on them, back off, back on, back off, back on, back off, back on, back off.

Wait, that kinda sounds like what ABS does right?

redvolution
12-01-2005, 03:37 PM
Oh come on, you know you've done it before. Step on the brakes and clutch at the same time, except the brakes lock up before the clutch disengages, resulting in a stalled engine. Usually involves a panic stop or spinning situation.

Oh, and if you do lock up the brakes while going straight without depressing the clutch, your engine will stall, and will start again when you release the brakes provided you are still moving.

I thought the RS's had viscous LSD and locked with speed differences no matter which direction they were rotating?

Ahh - I forgot about bumpstarting...

earlyapex
12-01-2005, 03:39 PM
[ducking...]
I know how to threshold brake. I have 25+ car track days and ~15 motorcycle tracks under the ole' belt. I was just trying to ask a hypothetical question.

And we are trying to answer it, even if it does sound like blasting. 8)

Btw, I see you live in oakland, we should meet sometime, since we are fellow track whores.

ZK
12-01-2005, 04:14 PM
Hmm.. this is my first car with ABS and I've never had a problem before with braking. Actually I would have preferred my Evo didn't come with ABS - feels artificial.

earlyapex
12-01-2005, 04:19 PM
Hmm.. this is my first car with ABS and I've never had a problem before with braking. Actually I would have preferred my Evo didn't come with ABS - feels artificial.

You'll get used to it and learn to absolutly LOVE it, on track espically. I was in the same boat as you when I went to my first ABS car. I thought it felt horrible but now I love it, espically when late braking with r-compounds. :twisted:

The sports-ABS on the 05 evo is pretty killer.

dohcvtec
12-01-2005, 04:23 PM
The sports-ABS on the 05 evo is pretty killer.
The 03/04's have a differen't type of ABS correct?

vtluu
12-01-2005, 10:40 PM
Wait, that kinda sounds like what ABS does right?
Kinda but not quite. ABS senses sudden deceleration in the wheel, so technically the wheel never quite locks up because ABS can react and release brake pressure much more quickly. It can also pulse the brake a lot faster than you can pump--and do so independently at each wheel (EBD).

I generally agree ABS is a good thing, though I had the general impression that I had better feedback through the brake system when I was driving Navid's RS.

earlyapex
12-02-2005, 01:12 AM
Wait, that kinda sounds like what ABS does right?
Kinda but not quite. ABS senses sudden deceleration in the wheel, so technically the wheel never quite locks up because ABS can react and release brake pressure much more quickly. It can also pulse the brake a lot faster than you can pump--and do so independently at each wheel (EBD).


Jayzus fugging krist. I know ABS is eleventy billion times faster than a human, I know it never locks up. I was making a general statement for gods sake.

Gaw damn engineers! :oops:

So what would you do in snow when all 4 lock up? Just keep the pedal down and hope for angel care bears from the sky to help you out of the situation? C'mon you are from Canada, what did you do when a moose ran out in front of you on a snow covered road?

redvolution
04-10-2006, 05:14 PM
better feedback through the brake system when I was driving Navid's RS.
I agree with this. The feedback is better than on my '03 but I wish the RS's came with cockpit defeatable ABS because I'm sure the computer can brake better than I can, especially in the wet.

Anyway, I went out for a drive on Sunday and aggressively locked up the wheels without depressing the clutch. The car stalled and then bump-started with a loud 'clunk' when I eased off the brake pressure.

RgistRdShowoffIX
06-11-2006, 12:04 PM
Quote from: vtluu
Quote from: earlyapex
Wait, that kinda sounds like what ABS does right?

Kinda but not quite. ABS senses sudden deceleration in the wheel, so technically the wheel never quite locks up because ABS can react and release brake pressure much more quickly. It can also pulse the brake a lot faster than you can pump--and do so independently at each wheel (EBD).


Jayzus fugging krist. I know ABS is eleventy billion times faster than a human, I know it never locks up. I was making a general statement for gods sake.

Gaw damn engineers! Embarassed

So what would you do in snow when all 4 lock up? Just keep the pedal down and hope for angel care bears from the sky to help you out of the situation? C'mon you are from Canada, what did you do when a moose ran out in front of you on a snow covered road?

lol god i'll miss those two.

and on subject. I miss NOT having ABS. But I guess i'm over it. =P

evo_dadi
06-11-2006, 03:58 PM
ooookay.....