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not locking up all 4 wheels

Printed From: Official Baja SAE Forums
Category: General
Forum Name: Design Discussion
Forum Description: Discuss Design, Tech, Cost, and related issues
URL: http://forums.bajasae.net/forum/forum_posts.asp?TID=2036
Printed Date: Mar/28/2024 at 3:35pm


Topic: not locking up all 4 wheels
Posted By: Lokesh
Subject: not locking up all 4 wheels
Date Posted: Jan/28/2015 at 1:23am

Hi guys this is lokesh from india. we are using 19.05mm TMC, 25.4mm callipers on each wheel,200 mm disc, X split circuit, pedal ratio 6:1 and DOT 4 brake fluid. Although we have done bleeding so much time and there is no leakage in the circuit, we couldn't yet achieved the all 4 wheel lock condition.so please give me suggestion to achieve 4 wheel lock.





Replies:
Posted By: Nate
Date Posted: Jan/28/2015 at 1:46am
Bigger master cylinder (more fluid displacement) or  http://www.tirerack.com/brakes/tech/techpage.jsp?techid=85" rel="nofollow - http://www.tirerack.com/brakes/tech/techpage.jsp?techid=85

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Iowa State University Cyclone Racing 2013 - 2016
Tech Director, DAQ, Media, Manufacturing, Radios
2016 - S&T, Maneuv, & Endurance Driver
"Because BAJA" "Because RACECAR"


Posted By: FelixB
Date Posted: Jan/28/2015 at 11:26am
There's a whole set of things you can try

Try playing with different setups...
Perhaps the pads are only efficient once they're hot... Can you find wheels with less inertia? Can you improve the leverage somewhere (pedal, disc, etc.)? Do you have custom discs (are you sure they're made of the right material?)


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Felix Belanger
Université Laval


Posted By: Aztec Warrior
Date Posted: Jan/28/2015 at 9:40pm

Those master cylinders are plenty big, we run a 1/2" master and 1" dual piston caliper, and have no problem locking up (even with a bent rotor.) Also, I have never bedded the brakes on a Baja and never had a problem with that.


You still have Air in the lines. I am guessing it is your rear tires that are not locking up. somewhere, your brake lines are flat or have a hump and you cannot pass the bubble. I have found the best method is to lift the rear of the car (with a forklift, or engine hoist) to near vertical. Then, use a "vibrating device" (ask your girlfriend or female member of the team to borrow hers) touching the brake line, working your way from front to rear. This should work the bubbles all the way to the rear calipers. Then bleed once more. Kinda wish I didn't give that secret away, always fun watching teams bleed quarts of oil in SAE parking lots struggling to pass brakes..Haha 

Also look to make sure the bleed points are at the highest point on the calipers (as mounted.) I have seen numerous team mount their calipers at an angle, making it impossible to bleed all the air out of the caliper without removing it.



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"To finish first, you must first finish"

SDSU Baja 2010 and 2014
McMillin Racing 2005-present


Posted By: sweeneyp
Date Posted: Jan/28/2015 at 11:45pm
Originally posted by Aztec Warrior Aztec Warrior wrote:

.... Then, use a "vibrating device" (ask your girlfriend or female member of the team to borrow hers) touching the brake line, working your way from front to rear. This should work the bubbles all the way to the rear calipers......

Hahaha just wow hahaha

.75" is a big cylinder? We are running 7/8" for the front (2 dual piston calipers) and .75" for the rear (single dual piston caliper), works great. We've never had lockup issues and it doesn't take much force to lock up.

Sounds like air in the system. Squishy pedal?


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The odd EE that does baja


Posted By: Richie_Dagger
Date Posted: Jan/29/2015 at 1:49am
3/4" is pretty big to me. Our brakes will lock up extremely easily with 1/2" masters. We have only ran as big as 5/8" in the past. 3/4" is the size of the master cylinder on my 1600lb VW Beetle, I can see how a master that big with some little 1" piston calipers would make for some stiff brakes. 


Posted By: njgedr
Date Posted: Jan/29/2015 at 8:37am
Tell me you have a picture of that! 

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Rowan Baja 2009-2012
Auburn 09
Peoria 11
Epreuve Du Norde 12
Auburn 12
Wisconsin 12

Mubea Development Engineer


Posted By: ankitk
Date Posted: Jan/29/2015 at 8:42am
I have a feeling that the recommended fluid fr your system is DOT3 and it will make a difference.
Though I may be very wrong.

there is one point in the braking system where the hard lines meet the flexible lines. The bleeding point of your caliper must be higher than this point.

Also, when you bleed, try lifting the calliper higher up than the master cylinder (or TMC). The bleeding point should be at the heighest in the braking system. If the caliper is at a height lower than the MC/TMC you will have difficulties getting air out.

The solid steel lines you have been using must have many bends in them. These bends usually entrap air. The method mentioned above of inducing vibrations seems to be the best to tackle this. 

The flexible hose you have been using may have some microcracks which you can not notice easily. Put sand over the hose so at to make it dirty. now pump the brakes a few times and check if minute fluid particles come up to the surface of the hose.

what method are you using for bleeding? the one with the transparent pipe or without?

Have you PROPERLY cleaned your rotors after bleeding? 


Posted By: zglazer
Date Posted: Jan/29/2015 at 7:25pm
Originally posted by ankitk ankitk wrote:

I have a feeling that the recommended fluid fr your system is DOT3 and it will make a difference.
Though I may be very wrong.
You're wrong. The only difference between DOT 3 and DOT 4 fluids is that DOT 4 has higher boiling points. They are otherwise interchangeable.


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Zack Glazer
McGill Baja Racing Alumnus 2009-2013 http://baja.mcgilleus.ca/" rel="nofollow - http://baja.mcgilleus.ca/
2012-2013 Drivetrain Designer


Posted By: krowx
Date Posted: Jan/30/2015 at 1:28am
Yeah DOT 4 is definitely not needed for Baja and 3/4"MC should be more than enough. I would bleed again with raised Calipers and check all fittings. The tiniest leak in a fitting wont necessarily leak fluid but will let air in and the tiniest air bubble can prevent good brake pressure. Also consider cleaning or even resurfacing rotors to help with lock up. Also some pads need to be broken in to provide the best friction. We always do a run around the parking lot dragging the brakes good and then bleed them a second time before attempting the brake test.


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Karson
ODU BAJA

2011 Kansas
2012 Wisconsin
2013 RIT
2014 Illinois


Posted By: ankitk
Date Posted: Jan/30/2015 at 4:26am
Originally posted by zglazer zglazer wrote:

Originally posted by ankitk ankitk wrote:

I have a feeling that the recommended fluid fr your system is DOT3 and it will make a difference.
Though I may be very wrong.
You're wrong. The only difference between DOT 3 and DOT 4 fluids is that DOT 4 has higher boiling points. They are otherwise interchangeable.




One last note on the DOT ratings: Systems designed for a particular type of fluid (especially prior to the wide distribution and use of DOT 4 fluids) should continue to be filled with that fluid. For example, in a car that was delivered with DOT 3 fluid, the internal components of the system (seals, brake hoses, and fittings for example) were specifically designed and tested for compatibility with the chemical composition of DOT 3 fluid. Because the DOT 4 grade fluid typically contains a different chemical composition, compatibility of system components may be an issue.

Source: stoptech.com
source 2: experienced this in a previous baja


Posted By: akss_bellatore
Date Posted: Jan/30/2015 at 4:42pm
I too would suggest a look into your method of bleeding . Do it with a transparent pipe and not the way the mechanics do it , they work on stock cars with perfectly laid out brake lines .

Also last year we blew our TMC off coz the guys responsible for bleeding were a little too enthusiastic and they destroyed one of the seals, make sure thats not the problem

There must least possible bends in the bundy tubes and also check if any of them is clogged (has happened with us).  Also a lot depends on how you bend ur tubes , sometimes u may change the CS area of the tube on one of the bends, look for that. 



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AKSS
A BAJA enthusiast pissed off at the gits running BAJASAE India


Posted By: nsievers
Date Posted: Feb/02/2015 at 7:28pm
A little tip for you guys. When your bleeding an initially dry system (no fluid in the lines), do a reverse bleed.
Basically, put your fluid in a bottle with a nozzle on it. Put a piece of flexible tubing on the end of the bottle's nozzle and the other end of the tubing on the bleeder valve. Flip the bottle upside-down, crack the bleeder and squeeeeze! Stop when the fluid makes it to the reservoir and manual bleed from there. It will save you a whole lot of time and pedal pumping. 


Posted By: Aztec Warrior
Date Posted: Feb/02/2015 at 7:59pm
not a bad idea. I have bled mountain bike brakes in a similar manner. I would imagine that if you were using this method it would be important to bench bleed the masters. If not, the air pocket from behind the piston could introduce a bubble anyways.

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"To finish first, you must first finish"

SDSU Baja 2010 and 2014
McMillin Racing 2005-present


Posted By: sujandinesh
Date Posted: Feb/03/2015 at 9:57am
With a pedal ratio of 6:1, i'm thinking you have a custom made pedal assembly. Are you sure you are getting complete master cylinder piston displacement for your full pedal travel? 



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RVCE BAJA: 2011-2015
General Motors: 2015-2016
Tyre Testing - University Racing Eindhoven: 2016-2017
Tyre Dynamics - TASS International: 2017-2018

Tyre Engineer - Apollo Vredestein
The Netherlands


Posted By: Lokesh
Date Posted: Feb/05/2015 at 12:05pm
Thanks guys for sharing your secret suggestions. I have almost done so many things but still it seems that all tires are not locking simultaneously.front tires are locked up quite further than the rear tures.I think there must be the phenomenon of weight transfer causing the front tires to locked up quite late.
Now again guys I need your help to find out a way.....I'm about to change the circuit from X to I, if it also doesn't work then do suggest me another way...
May be proportioning valve or
Brake baising.


Posted By: njgedr
Date Posted: Feb/05/2015 at 1:25pm
Lokesh,

Front and rear or side to side should be separate circuits, Typically, with a balance bar to adjust bias depending on how you setup your brakes.  

The rules require separate circuits that will work independently of each other. Not sure what you mean by X or I.  It sounds like you have a bias or bleeding problem. The fronts should be harder to lock than the rears because of the weight transfer all things symmetrical. 
 


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Rowan Baja 2009-2012
Auburn 09
Peoria 11
Epreuve Du Norde 12
Auburn 12
Wisconsin 12

Mubea Development Engineer


Posted By: FelixB
Date Posted: Feb/05/2015 at 3:44pm
nope he says he has a TMC (Tandem Master Cylinder) so he has no balance bar 

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Felix Belanger
Université Laval


Posted By: Lokesh
Date Posted: Feb/05/2015 at 11:38pm
Guys X circuit means diagonal split in which one circuit connect the front left and rear right while another circuit connects front right and rear left.and in I circuit both front tires are connected with one circuit and both rear tires are connected with another circuit.
Guys for baising I have to use two TMC and complex linkages and really I don't want to make this complicated. So help me out to find solution for this weight transfer phenomenon.


Posted By: sujandinesh
Date Posted: Feb/06/2015 at 4:31am
According to me, this has nothing to do with the load transfer. I have used the same setup you have described, last year (though the cars might weigh differently) and didn't come across any such problems. With the same caliper and disc at all four wheels, the effect due to load transfer shouldn't be much. 
I also used a proportioning valve last year and didn't make much of a difference. With the competition just two weeks away i don't think you should be planning on that.
However if all wheels are locking, then it shouldn't be a problem passing tech. The rulebook doesn't say they should lock simultaneously. 
Still to me, it still looks like its still a bleeding issue. 



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RVCE BAJA: 2011-2015
General Motors: 2015-2016
Tyre Testing - University Racing Eindhoven: 2016-2017
Tyre Dynamics - TASS International: 2017-2018

Tyre Engineer - Apollo Vredestein
The Netherlands


Posted By: Lokesh
Date Posted: Feb/06/2015 at 7:25am

thanks bro but if you don't mind could you please tell me of which car's proportioning valve have you used???



Posted By: Elpwnage20
Date Posted: Feb/07/2015 at 5:58pm
I've thought of an alternative to using a balance bar. I was thinking of offsetting the location of the front and rear master cylinders using spacers. So the cylinder that needs less travel to lock up it's wheels would be attached a bit further from the pedal. Would this be a viable option?


Posted By: sujandinesh
Date Posted: Feb/08/2015 at 3:32pm
Well he's using a tandem master cylinder so I don't know whether that could be done here.
And lokesh, you can search online, there are many stores that will provide what you need.

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RVCE BAJA: 2011-2015
General Motors: 2015-2016
Tyre Testing - University Racing Eindhoven: 2016-2017
Tyre Dynamics - TASS International: 2017-2018

Tyre Engineer - Apollo Vredestein
The Netherlands


Posted By: Elpwnage20
Date Posted: Feb/08/2015 at 6:07pm
Originally posted by sujandinesh sujandinesh wrote:

Well he's using a tandem master cylinder so I don't know whether that could be done here.
And lokesh, you can search online, there are many stores that will provide what you need.


But would that work with dual cylinders?


Posted By: Lokesh
Date Posted: Feb/09/2015 at 10:04am
You can use balance bar with two MC if you have significant weight transfer, but first you should check that all tires must lock no matter whether it is simultaneous or not.If braking comes with huge weight transfer then I would suggest you to go with proportioning valve first. If it doesn't help then go with balance bar.
And guys thank for your suggestions, I have succeeded in wheel lock.and ready to rock in BAJA.


Posted By: sujandinesh
Date Posted: Feb/09/2015 at 10:07am
I have very less experience with dual cylinders but according to me, that should work.
You'll face problems while bleeding though.
But it would be better if someone more experienced with balance bars could answer.

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RVCE BAJA: 2011-2015
General Motors: 2015-2016
Tyre Testing - University Racing Eindhoven: 2016-2017
Tyre Dynamics - TASS International: 2017-2018

Tyre Engineer - Apollo Vredestein
The Netherlands


Posted By: FelixB
Date Posted: Feb/09/2015 at 10:40am
why not use a balance bar???



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Felix Belanger
Université Laval


Posted By: Elpwnage20
Date Posted: Feb/09/2015 at 5:40pm
they're expensive


Posted By: zglazer
Date Posted: Feb/09/2015 at 5:42pm
Not as expensive as the $1150 in registration fees you'll have wasted if you can't pass brake check.


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Zack Glazer
McGill Baja Racing Alumnus 2009-2013 http://baja.mcgilleus.ca/" rel="nofollow - http://baja.mcgilleus.ca/
2012-2013 Drivetrain Designer


Posted By: FredC
Date Posted: Feb/09/2015 at 8:38pm
Why not make your own balance bar design? We did this to save few $, it isn't hard to do... and even a balance bar is not what I call expensive... unless 50$ is expensive for you.


Posted By: FelixB
Date Posted: Feb/09/2015 at 9:59pm
Like Fred says, they can be pretty inexpensive... we've made some versions with threaded rod, a rod end and whatever we could find for spacers...

Not too hard to machine either


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Felix Belanger
Université Laval


Posted By: Lokesh
Date Posted: Feb/11/2015 at 9:30pm
Ya this is expensive and quite bulky but nevertheless the easiest way to lock the wheels.. You can built your own assembly it's not a tough task..it is already used in Indian tractors, two MC one for the front wheels and another one for rear wheels..just check out the image below.. uploads/2770/Screenshot_2015-02-07-03-21-49.png" rel="nofollow - Screenshot_2015-02-07-03-21-49.png


Posted By: ankitk
Date Posted: Feb/13/2015 at 12:38pm
what Finally did the trick Lokesh?


Posted By: Lokesh
Date Posted: Feb/13/2015 at 6:05pm
I just change the master cylinder from four port TMC to two port MC. Just make sure that bleed screws are in upper most position, and there is no leakage in the circuit.your pedal arrangement must ensure full travel of MC piston.slight rubbing of pad surface and disc could also help by increasing friction b/w them.


Posted By: nitin narayan lataye
Date Posted: Jul/28/2018 at 2:16pm
means you use 2 master cylinder with balance bar ??
and what diameter of master you used ??


Posted By: sujandinesh
Date Posted: Jul/28/2018 at 3:34pm
I strongly suggest you look at the time stamp of the old post before reopening the thread, especially with questions like these. 

The diameter of the master cylinder depends on your vehicle parameters and hence must be calculated yourself. 


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RVCE BAJA: 2011-2015
General Motors: 2015-2016
Tyre Testing - University Racing Eindhoven: 2016-2017
Tyre Dynamics - TASS International: 2017-2018

Tyre Engineer - Apollo Vredestein
The Netherlands


Posted By: satyen
Date Posted: Jul/29/2018 at 1:10am
hey! Can you please help me with the basics of proportioning valve, i am designing a valve, we have TMC where should be the valve attached like for the rear system or the front system,
Mostly i think it would be  attached in rear..can you help me with its effects in rear and also onto the front system??



Posted By: sujandinesh
Date Posted: Jul/29/2018 at 9:08am
Definitely. 

First, I would suggest you look at why you want a proportioning valve in your brake system, this should tell you where it must go and also its effects on the circuit its being connected.

Further, a proportioning valve can only proportion the amount of brake pressure given to it, so its effects on the circuit to which it is not connected will be none.  


-------------
RVCE BAJA: 2011-2015
General Motors: 2015-2016
Tyre Testing - University Racing Eindhoven: 2016-2017
Tyre Dynamics - TASS International: 2017-2018

Tyre Engineer - Apollo Vredestein
The Netherlands



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