mackei23b
|
| posted on 8/11/06 at 08:49 AM |
|
|
Brake Bias
Hi there
I'm building an MK Indy with a ZX9R Bike engine. I'm about to make up the brake pipes, but I just want to check how many BECs have used a
bias valve for the rear brakes. I have a fiat brake valve on standby, but I'm wondering whether I should fit it or not.
I'm running with standard vented discs on the front and solid discs on the back with the standard sierra calipers.
Let me know your experiences.
Many thanks
Ian
|
|
|
|
|
ReMan
|
| posted on 8/11/06 at 09:34 AM |
|
|
I put an adjustable bias valve in my rear line. So far it's still wide open!
At SVA, admittedly with brakes barely bedded in all round, the balance front to rear was fine.
On the road and track so far I've not yet cosidered that the rears are locking up at all.
So my conclusion at the moment is I wasted my money, but it looks nice
|
|
|
PAUL FISHER
|
| posted on 8/11/06 at 09:37 AM |
|
|
With the standard sierra brake set up on a Indy,you tend to get a slight over bias to the rear brakes,in wet weather on track,under hard braking the
rears can lock before the fronts,I would recommend fitting of a ajustable brake bias valve,it would give you better control over the bias in all
conditions,I will be fitting one on my next MK.
Just add MK sportscars are now fitting ajustable bias valves to there track cars.
|
|
|
ReMan
|
| posted on 8/11/06 at 09:40 AM |
|
|
quote:
Originally posted by PAUL FISHER
With the standard sierra brake set up on a Indy,you tend to get a slight over bias to the rear brakes,in wet weather on track,under hard braking the
rears can lock before the fronts,I would recommend fitting of a ajustable brake bias valve,it would give you better control over the bias in all
conditions,I will be fitting one on my next MK.
Just add MK sportscars are now fitting ajustable bias valves to there track cars.
I think you're probably right Paul.
As you say it probably is slight too so will show up more in the wet.
I'll have to try harder next time out on the track and re-assess
|
|
|
mookaloid
|
| posted on 8/11/06 at 10:04 AM |
|
|
Having experienced a sprint day in the wet with no bias valve, I can confirm that repeatedly having the rears lock up just as I was about to turn in
to the corners was not my idea of fun!
I think it needs a valve......
Cheers
Mark
"That thing you're thinking - it wont be that."
|
|
|
skydivepaul
|
| posted on 8/11/06 at 11:04 AM |
|
|
yes i also agree.
The rears can definatley lock up first under less than ideal conditions. As Mark previously stated, NOT FUN
http://www.smartideasuk.com
http://www.smartmapping.co.uk
HD CCTV
3D design solutions and integration
IP security systems
access control systems
|
|
|
Hellfire
|
| posted on 8/11/06 at 01:11 PM |
|
|
Just trying to get this clear in my head. IIRC, the brake test carried out at SVA ensures that the braking forces of the vehicle induce the fronts to
lock up before the rears. If it passes this criteria, then unless you alter your brakes after SVA, they should have the same characteristics
regardless of the weather conditions ie, fronts locking before rear (in a straight line).
If it's a combination of the cornering forces during braking that induce the rears to lock before the front, you're going round the corner
too fast.
Phil
|
|
|
tks
|
| posted on 8/11/06 at 01:39 PM |
|
|
thats not true hellfire
You are not right...
It depends wich tyre size you have on the front and the rear and also the weight on the rears and the fronts..
It all depends on if the applied force is bigger as the grip yes or no!
if in the wet the rear has less grip.. (because wider tyre or less weight etc. etc.) then if the grip is lower it will lockup allot earlier then the
fronts...
imagine you go on ice! who will locup first?? or the rears or everything..
Tks
The above comments are always meant to be from the above persons perspective.
|
|
|
mookaloid
|
| posted on 8/11/06 at 01:50 PM |
|
|
quote:
Originally posted by Hellfire
Just trying to get this clear in my head. IIRC, the brake test carried out at SVA ensures that the braking forces of the vehicle induce the fronts to
lock up before the rears. If it passes this criteria, then unless you alter your brakes after SVA, they should have the same characteristics
regardless of the weather conditions ie, fronts locking before rear (in a straight line).
If it's a combination of the cornering forces during braking that induce the rears to lock before the front, you're going round the corner
too fast.
Phil
Hi Phil,
In my case (I have rear disks) this occurred with a change of brake pads at the rear which improved the braking by quite a lot - enough I guess to
alter the F/R braking ratio as measured at SVA. Although I cannot say if there was a problem before the change of pads as that particular sprint was
one of my first outings on a track in the car.
I don't feel this would be an issue with drum braked cars.
There should be no cornering forces during braking as you should only be braking in a straight line
For anyone looking to improve their cars braking after SVA and making changes which could alter the F/R braking ratio I think a valve to give some
control is a good idea
Cheers
Mark
"That thing you're thinking - it wont be that."
|
|
|
Hellfire
|
| posted on 8/11/06 at 09:49 PM |
|
|
quote:
Originally posted by mookaloid
There should be no cornering forces during braking as you should only be braking in a straight line
You never heard of trail braking?.....
I agree that a bias valve would be useful for adjusting braking forces, I just can't understand why the rears would lock up before the fronts in
a straight line, (regardless of weather conditions) unless the brakes had been altered after SVA or the car hadn't quite been set up
properly.
Phil
|
|
|
mookaloid
|
| posted on 8/11/06 at 10:20 PM |
|
|
Trail braking? go on then enlighten me
"That thing you're thinking - it wont be that."
|
|
|
Hellfire
|
| posted on 8/11/06 at 10:26 PM |
|
|
Trail braking
While the general rule for road driving involves separating braking and cornering there is a notable exception called trail braking. Trail braking is
originally a racing drivers' technique and describes continuing to brake as your turn into a bend. When applied with suitable skill this method
confers some significant advantages:
* Braking can be left later, which allows for more fine tuning of cornering speed. In particular you have seen much more of the bend before you
have finished adjusting speed.
* When your vision is shortest if an obstruction appears your foot is already on the brake pedal saving 0.2 seconds
* Forwards weight transfer from braking enhances front tyre grip at the turn in point.
* Adjustment of the braking force can be used to control the relative proportions of front grip and rear grip, and hence the attitude of the
car.
* If you are confident and competent to brake in the early stages of a bend you have better options if the corner has been misjudged. In other
words, trail braking is excellent for disaster recovery.
In practice, trail braking works like this: You brake on the approach to a bend in the normal way. Instead of releasing the brake before you turn in,
you continue to brake during the turn in phase, and perhaps all the way to the apex. As you travel through the bend you gradually blend out the
braking and smoothly transition to the throttle. Typically you might well be back on the throttle after perhaps 1/3rd of the bend.
Trail braking is a difficult and subtle technique. It is dangerous to try to learn it on the public road. If you brake too hard or at the wrong time,
trail braking can (and does!) easily cause a spin.
|
|
|
mookaloid
|
| posted on 8/11/06 at 10:38 PM |
|
|
ok I can see that could have it's place from time to time, although I would have thought in order to make such a technique meaningful, you would
need to be able to adjust the brake bias to se the car up to be able to use trail braking effectively (too much rear and you would spin) (too much
front and it wouldn't do anything)
The only times I have braked (deliberately) in a corner has been under conditions of big understeer when I have tried a left foot dab mid corner (with
the throttle on) to try to get the front to dig in a bit to get around the corner.
Cheers
Mark
"That thing you're thinking - it wont be that."
|
|
|
zxrlocost
|
| posted on 9/11/06 at 09:02 AM |
|
|
the best bit of advice I can give is keep your brakes bog standard for the sva I had happy shopper pads and at the most vented dics
I went to the sva with performance stuff the first time and the brakes were terrible
then no bias no nothing worked a treat
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
.jpg){kind=avatar}
