Rear disk convertion questions...

[NeX]

RE: RE: Rear disk convertion questions...

No asbestos is used in cars any more its been totally outlawed for a while now. Also everyhing does change size due to heat, you cannot avoid that however clearences will be designed to accomdate this (one of the resons shims etc are used)

oh right, that makes me feel alittle bit better. i was cleaning the sunny brakes with a drill and brush atachment, and ended up breathing in alot of the black brake dust. i was waring a mask but i only found out afterwards that it was crap!

Shims?

so if i do hard driving and then park up, the amount that the disk shrinks and the pad could be enough to let the car roll?

 

[Andrew]

RE: RE: Rear disk convertion questions...

Andrew

2. Pad area has nothing whatsoever to do with force applied, it is down to the area of the piston. Frictional force is independant of area, at least if you are talking about static friction.

since the braking force is dependant on the pressure being delivered........how can u say that the brake pad size doesnt matter!? pressure if force/area.........so if the pad was bigger then there would be a larger area, but less pressure, an if there was a tiny pad then there would be all the pressure accros a small area, so there has to be a ballanced striked between getting the rite amount of pressure and the right amount of friction, you my friend are a grade A retard

You are confusing the issue of pressure in the hydraulic system and pressure between the pad and disc. You do realise that the pad area is not the same as the piston area?

If there is 100psi in the hydraulic circuit, and the piston area is 1 inch^2, then there is 100 pounds of force being exerted on the pad. There are no two ways about this, this is fact.

Frictional Force = Coefficient of Friction x Normal Force

This is another formula that for static friction holds true. There is no concept of area in it. I realise that brakes are not static friction, but dynamic friction is far too complex to deal with.

If you apply a force of 100 pounds on a 1 inch^2 surface, the pressure is 100psi. This pressure will cause a large amount of friction over an area of 1 inch^2. If the surface is 100 inch^2, then the pressure will be 1 psi, causing a smaller amount of friction per unit area, but because the area is proportionally bigger, the total frictional force remains the same. There are other factors, but if you want simple, this is actually pretty accurate.

This lecture gives a relatively good analysis of the torque and power transmitted in a disc clutch. A clutch is the same as a disc brake, except it acts over a fraction of the circle.

http://theduchy.ualr.edu/classes/asci5335/clutches.pdf

Look at the formula - it has force, coefficient of friction, and the inner and outer diameter of the clutch disc (due to angular velocity). Nothing to do with pad area. Even if it did, your maths is flawed.

If you want properly complicated, there are finite element analyses of the entire brake system, including thermal expansion, gassing, dynamic friction, and so on all available on the web.

It's normally pretty widely accepted that the first person to resort to insults, or take the argument off on a tangent, is losing, and can't argue anything relevant anymore.

Andrew MEng (Hons) ACGI (employed by P&O Nedlloyd as a marine engineer).

 

[Beachboy]

RE: RE: Rear disk convertion questions...

from experience i found it instantly recognisable when the rears lock up. i can feel it, i can hear it. due to how my car is it gives me lots of feedback from the chassis and the steering wheel.

There is the key difference - "from experience". Very, very few drivers have experienced this. The car manufacturers don't want the average driver to wreck their car because of this behaviour. I would also think, when it came to the crunch, and you stop thinking and just acting, as you do when something really bad is happening, you too would prefer a car where the front wheels lock first, and you can intuitively deal with the situation.

i hate it when the rears lock up 1st. thats why i changed the bias on my micra to give more front force.

 

[quickdraw]

soooooooooooooooooo.....

which is better..

ricardo..
please. in lahmanns terms (sp?)

for a nissan micra k10/k11 pushing up to and beyond 150-200bhp. do you recomend that discs are used over drums.

as i in my perseptiopn of things etc believed and had for ages that discs were overall a better brake to have at the rear. no matter what the brake ratio is.

since if you simply look towards ANY car that has up and over 1.6 they are more than normally always have discs to the rear. (one way of identifying a bigger engine within a car without actually lifting the hood.)

and if so. and seens though it seems you have some knowledge of this.
what would be the way to go around changing from drums to discs and how would you combat the handbrake situation etc!!

ricardo you have some very valid points. but please dont lower yourself into personal vendetta against, what u believe also. the dissagreeing is not what is outlawed it is the vendetta itself and the harshness it brings. so please. wihtout creating personal attacks please state your case as i personally would REALLY like to hear what you have to say.

along with the dissagreement of ED and Andrew (who normally are in co-ordance with each other on most subjects)

please dont let this thread go out of hand as it is one of the most enjoyable and interesting reads for a long time. with actually technical issues at debate. sumthing that needs o be more enforced.
things that bring out the best info hidden away within people.

DONT shoot that person down for speaking their mind. simply inform them (if they are wrong) of why they are wrong. dont attack them!!

ED you should know this also, so please dont speak about ricardo also as if he is not here reading it. YOU should know better as this itself insites anger and frustration. YOU would not like it enforced your way, please dont enforce it towards others

wayne

 

[Beachboy]

RE: RE: Rear disk convertion questions...

Beachboy this wasn't when you put incredibly dangerous and thin tyres on the back to stop understeer was it ?! lol

no it was with standard setup allround.
the 12" 145/80 tyres i have on the back at the moment are a bit wild. not enough grip. very light though. i'm only using them now to use up the rubber over summer. i may dispose of them after, or get 165/60 sport tyres for them.

 

[Ed]

oh right, that makes me feel alittle bit better. i was cleaning the sunny brakes with a drill and brush atachment, and ended up breathing in alot of the black brake dust. i was waring a mask but i only found out afterwards that it was crap!

Be warned that older cars MAY have old pad dust left behind that did have asbestos. I dont know the exact cut of age, but certaintly some K10s could have this.

Shims?

so if i do hard driving and then park up, the amount that the disk shrinks and the pad could be enough to let the car roll?

No that will never happen, the handbreak cable will streach a whole lot more than any disk could shrink. youll never have the car roll away by the rear disks shrinking.

 

[Titch]

the amount that the disk shrinks and the pad could be enough to let the car roll?

Couldn'd you just leave the car in gear so that there is no worry about it running away from you?

 

[NeX]

from what i'm getting it's better for a small car with high speed to have all round DISKS (come on people get it right)

like the porche boxter,

were as low speed high momentum vehicals like lorrys and busses have drums....



am i close

 

[quickdraw]

from what i'm getting it's better for a small car with high speed to have all round DISKS (come on people get it right)

like the porche boxter,

were as low speed high momentum vehicals like lorrys and busses have drums....



am i close

yes. as to what i have gathered and what i had as my general perseption this is bout as close. AND simple as it can get.

 

[Ed]

Wayne, for you If I were to build a car from scratch I would personally choose disks all round. Main reason they are generally more reliable and quicker to service. However you already have the Drum brakes and you must ask youself the question is are the gains in converting them worth it for your application. For road driving I would definately say NO. Even upto 200bhp.

 

[NeX]

RE: RE: Rear disk convertion questions...

Be warned that older cars MAY have old pad dust left behind that did have asbestos. I dont know the exact cut of age, but certaintly some K10s could have this.

it was a 1993 2.0 nissan sunny GTi.... so should be ok

No that will never happen, the handbreak cable will streach a whole lot more than any disk could shrink. youll never have the car roll away by the rear disks shrinking.

good thats nice to know hehe

Couldn'd you just leave the car in gear so that there is no worry about it running away from you?

i don't like leaving it in gear because i sometimes forget to put the clutch in when i start it and bad things happen...

 

[Beachboy]

i was worried awhile ago about asbestos dust from cleaning up some 1980's calipers. shouldnt worry too much because i read that the abestos fibres when burnt from brake temperatures the fibres are broken down and not that dangerous. its when mechanics used to rub down and service the pads/shoes of older brakes there was a high danger.

 

[Andrew]

oh and by the way people its Disk not disc, we're no American

Disc is English, disk is American English. SAE wants us to spell it disc as well. Porsche, Ferrari and the other sports car manufacturers spell it disc. I'll stick with disc

 

[ricardo_swarez]

i dont just do breaking, i do a lesson were we do all aspects of a car, like taking the car apart completly and working out all torques and pressures within all the major parts, i do appologise to andrew tho, after reading his post my coment sayin he is a grade A retard, was wrong, he has a great understanding about brakes, and to do with thermal expansion, expansion is minimal, pads are composite and are made up of many abrasive materials, they are made this way so they dont expand to a degree that it actualy matters, but friction is dependant on heat, hence higher temperatures mean increased chance of locking, because disks have a greater area an twice as much pressure and torgue they create more heat and so lock, andrew is rite tho, tyres stop you car, not brakes, but disks are still better because they create twice the force an four times the torque

 

[Andrew]

i was worried awhile ago about asbestos dust from cleaning up some 1980's calipers. shouldnt worry too much because i read that the abestos fibres when burnt from brake temperatures the fibres are broken down and not that dangerous. its when mechanics used to rub down and service the pads/shoes of older brakes there was a high danger.

Asbestos is dangerous because the fibres are really really small anyway. The dust worn off by braking would probably break it down enough anyway. Non-asbestos brake dust isn't much good for you either, but won't cause cancer. Best just to avoid breathing it at all.

 

[NeX]

RE: RE: Rear disk convertion questions...

i was worried awhile ago about asbestos dust from cleaning up some 1980's calipers. shouldnt worry too much because i read that the abestos fibres when burnt from brake temperatures the fibres are broken down and not that dangerous. its when mechanics used to rub down and service the pads/shoes of older brakes there was a high danger.

few

Disc is English, disk is American English. SAE wants us to spell it disc as well. Porsche, Ferrari and the other sports car manufacturers spell it disc. I'll stick with disc

are you sure? damn now i'm gonna have to find a dictionary


just checked the web
[Latin discus, quoit, from Greek diskos, from dikein, to throw. See deik- in Indo-European Roots.]

huh what does that mean :S

 

[ricardo_swarez]

i understand what your saying andrew, i did finite element analysis in my thesis, you are rite, im not desputing that, but my maths isnt flawed, in my actualy equations i take into account piston sizes, but i can hardly post 8pages of pure maths on this site, so i took the simple parts and posted those, i thort you were saying that pressure has nothing to do with area, were infact pressure is derived from area, i'e appologised for calling you a retard, ed's arogance realy pisses me off, but my maths isnt flawed

 

[NeX]

see all friends here,

so AGAIN

for a micra, disks/discs or drums?

sounds like disks/discs to me....

 

[ricardo_swarez]

my mate, kristian has a gx with disk/drums, and a super s with disk/disk, he'l probley post an give you an idea from experience, he's in london at the minute, but i spoke to him on the phone an he's goin to try an read this post

 

[NeX]

cool, i got a GX with disk/drums and it's not great at stopping but i think this is because the pads need changing,

also it skids if i brake too hard but i don't think the back locks up just the front...

 

[Ed]

In response to your maths is not flawed your project is most probably fine, but taking out small chunks and putting them in a post missing out many of the equations makes your post over simplified and meaningless HENCE flawed.

One thing to bear in mind NeX dave had to have his car examined by an engineer afterwards to satisfy the insurance company that the conversion was safe. you will need to make the same checks.

Ed

 

[ricardo_swarez]

no it dont make it meaningless, i stated values, then used them, the maths is rite, i no it is, so it isnt flawed, the maths of the entire case study is 8pages long, i can hardly post that, an some is irreleant, so i posted sections that are easy to follow and understand, the only thing flawed is you inability to comunicate in a non arogant way

 

[NeX]

RE: RE: Rear disk convertion questions...

In response to your maths is not flawed your project is most probably fine, but taking out small chunks and putting them in a post missing out many of the equations makes your post over simplified and meaningless HENCE flawed.

One thing to bear in mind NeX dave had to have his car examined by an engineer afterwards to satisfy the insurance company that the conversion was safe. you will need to make the same checks.

Ed

well i don't know the first think about brakes which i'm sure shows so i'm getting an pro to do the job and check it

but if it all goes ok then i would have thought the insurace company would be happy that my car can stop quickly... they'd rather it wasn't moving at all but you know

 

[ricardo_swarez]

insurance companys dont like uprated brakes :s they think your goin to need them, an are goin to be racing or something, plus there an added cost for the insurance company to pay out on, so i'd ring unp your insurance company first an ask them how much it would go up.....insurance=pure piss take imo

 

[NeX]

RE: RE: Rear disk convertion questions...

insurance companys dont like uprated brakes :s they think your goin to need them, an are goin to be racing or something, plus there an added cost for the insurance company to pay out on, so i'd ring unp your insurance company first an ask them how much it would go up.....insurance=pure piss take imo

ok well i need to check with them about a few things... i think i might go adrian Flux

 

[Beachboy]

insurance company will see it as you have better brakes and will approach dangerous corners faster and be more liable to be in dangerous situations. and charge accordingly. they will see it in any way that generates them more income. and the brakes will make the car more desireable and more liable to theft or vandalism. and charge you accordingly.


same logic as having a roll cage will make some premiums go up not down.
i wonder at what point their logic get turned around. fit a £150 anti theft device visibly inside the car. hmm thinks insurance, leaving valuable item on display in the car. will have to increase your premium.

 

[NeX]

Bstards!

 

[Craig]

To get asbestosis you need exposure over a long period of time don't you?

 

[Ed]

No, one unlucky fiber can do it apparently. (though clearly you have higher chances over more exposure)

 

[Andrew]

To get asbestosis you need exposure over a long period of time don't you?

You only need one fibre to become embedded in your lungs to cause mesothelioma (cancer caused by asbestos). Asbestosis is a bit different, and is generally caused by heavy exposure. Both are untreatable, and really disgusting.

 

[Craig]

That really sucks then - so much for progress.
Back on topic, is the main advantage of disks their heat dissipation characteristics?

 

[NeX]

sounds like it, and the fact that they are open air...

 

[Dr Zoidberg]

after reading this and becoming confused, i gather its worth keeping the rear drums as its not worth the money and effort to change to discs. as on a micra the drums are spot on even up to 200bhp?

will the rears drums lock up with a lightened, lowered car?

:S

 

[Beachboy]

yes they do. but you just need to change the bias.
you would benefit from discs in a fast motorsport application.

 

[NeX]

RE: RE: Rear disk convertion questions...

you would benefit from discs in a fast motorsport application.

Muhahaha perfect :devil:

 

[Dr Zoidberg]

RE: RE: RE: Rear disk convertion questions...

you would benefit from discs in a fast motorsport application.

Muhahaha perfect :devil:

heh heh heh fixed

is it hard to change the brake bias? and how much does it need to be changed by?

cheers

 

[NeX]

i think the bias totally depends on your system and has to be fine tuned to each car, i would have thought this could be done on a rolling road?

as for how to do it, check the haynes apparently

 

[Beachboy]

yes check haynes how you do it. can do it by trial and error to see what adjustment suit you best.

 

[Dr Zoidberg]

ok cheers