Caliper Selection

[packtim]

I am still trying to select the calipers for my braking system, but seem ot be going round in an endless loop trying to do it.
The problem is not so much the calcultions, its physically getting a disc and rotor that will fit together.

I have looked at many other FSAE car specs, and almost every uni has designed their own brake rotors, thus making it easy to fit the rotors and calipers together. However, I dont have the time to design the rotors (project CAD has to be done in 2 weeks), and my project supervisor has said its not really an option.

I decided on using the rear rotor from the CBR600, but am struggling to find a caliper that will fit it. I could use the standard CBR 600 rear disc caliper, but this seems to be made by a Honda in-house company, Nissin. Therefore, its very difficult to find mounting dimensions, bore, etc of the caliper.

I want to use Wilwood Billet Dynalite Single's, but the pad is too big to fit on the CBR 600 rotor, even though Wilwood website says it will fit between 6 and 13 inch rotors.

Anybody got any tips for matching calipers to discs?


Thanks

Tim

[Psychosis]

Originally posted by packtim:
Therefore, its very difficult to find mounting dimensions, bore, etc of the caliper.


Do what everyone else does and use a set of vernier calipers to measure it. in all honesty you should do that with everything you buy to make sure your CAD model is as accurate as possible, plus drawings arent always accurate (except for torsens which are fantastichttp://fsae.com/groupee_common/emoticons/icon_smile.gif

the dynalites have a pad height of approximately 40mm if that helps. as you say they probably wont fit your rotor. the rotor diameters wilwood quote are diameters, they dont factor in pad height.

[Buckingham]

If the only thing holding you back is that the pad is too big, machine or laser cut the pad (provided the backing plate still contacts the entire piston).

[packtim]

Originally posted by Psychosis:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by packtim:
Therefore, its very difficult to find mounting dimensions, bore, etc of the caliper.


Do what everyone else does and use a set of vernier calipers to measure it. in all honesty you should do that with everything you buy to make sure your CAD model is as accurate as possible, plus drawings arent always accurate (except for torsens which are fantastichttp://fsae.com/groupee_common/emoticons/icon_smile.gif

the dynalites have a pad height of approximately 40mm if that helps. as you say they probably wont fit your rotor. the rotor diameters wilwood quote are diameters, they dont factor in pad height. </div></BLOCKQUOTE>

Thing is I cant buy one/get hold of one before hand, and defintaley wont be able to get hold o fit by the end of next week. This is a design project for my finaly year, the whole car gets designed before xmas, but nothing actually gets bought until after xmas.


Having said that, from their website, I was assuming the pad was 50mm high. The OD of the disc is 220mm, and mounting bolts are on a PCD of 125mm(10.5mm through), leaving me probably about 40mm of gap left. Will have to consider this though, sounds risky.

Thanks for your help


Tim

[Psychosis]

it does indeed sound risky. is there no way you can go to a bike breakers and ask nicely to measure it. if not wilwood do some nice aluminium rotors to match the dynalite calipers. all the dimesions are on the website, the discs weigh a reasonable 700grams and are made of al-mmc.

http://www.wilwood.com/Products/002-Rotors/012-Alum/pmar/index.asp

go for the twin piston dynalites to match the discs and the poly-Q pad compound to match the rotors. the friction curves are on the website which should help your project. brakes on the car never ran in excess of 250C (based on measuring after a number of heavy brake applications on multiple laps. i dyno tested them to 450C and they didnt disintegrate. they provide a good base for the designing your own rotors in future.

[packtim]

Originally posted by Psychosis:
it does indeed sound risky. is there no way you can go to a bike breakers and ask nicely to measure it. if not wilwood do some nice aluminium rotors to match the dynalite calipers. all the dimesions are on the website, the discs weigh a reasonable 700grams and are made of al-mmc.



http://www.wilwood.com/Products/002-Rotors/012-Alum/pmar/index.asp

go for the twin piston dynalites to match the discs and the poly-Q pad compound to match the rotors. the friction curves are on the website which should help your project. brakes on the car never ran in excess of 250C (based on measuring after a number of heavy brake applications on multiple laps. i dyno tested them to 450C and they didnt disintegrate. they provide a good base for the designing your own rotors in future.

Thanks a lot. Problem is we are running 12inch ID rims. so may be a bit of a squeeze with the caliper+these may be larger than are really required for the job. Most teams seem to use aroun 8-9 inch rotors all round the car. I figured out this leaves me with 2mm inbetween rim and edge of caliper(very risky!) Having said that, have you used this combo before for your car, or is this what you recommend?


Another thing is these rotors are 7.9mm wide. Wilwood have 4.8mm calipers or 9.?mm dynalite single calipers. Is it possible to get them to fit these still, as I guess the cylinder isnt easily adjustable?
Thanks


Tim

[Psychosis]

we've run that set up before on our rims (13s) and also had very little clearance, nothing a file cant sort if you have problems http://fsae.com/groupee_common/emoticons/icon_wink.gifGo for 9mm calipers. i wouldnt worry as the pistons are self adjusting to compensate for pad wear and alignment. the pad material is about 10mm thick and you wont use that unless you do a huge amount of testing. note, the alu rotors will wear about the same rate as the pads, roughly just incase you buy them and start getting worried.

[Agent4573]

we currently use the dynalite singles designed for the 9mm thick rotor, on 4 mm thick rotors. Haven't had a problem yet. Possibly if the pad starts getting extrememly worn down we may have a problem and we might have to make spacers to sit behind the pads, but if that day ever comes, ill just change the pads.

[packtim]

Originally posted by Agent4573:
we currently use the dynalite singles designed for the 9mm thick rotor, on 4 mm thick rotors. Haven't had a problem yet. Possibly if the pad starts getting extrememly worn down we may have a problem and we might have to make spacers to sit behind the pads, but if that day ever comes, ill just change the pads.

So ho come they arent so dependent on the thickness? I thought I would have real trouble if i put a 5.1mm caliper on a 4.5 disc, for example. I suppose i can just adjust master cylinder sizes accordingly

[Psychosis]

Originally posted by packtim:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Agent4573:
we currently use the dynalite singles designed for the 9mm thick rotor, on 4 mm thick rotors. Haven't had a problem yet. Possibly if the pad starts getting extrememly worn down we may have a problem and we might have to make spacers to sit behind the pads, but if that day ever comes, ill just change the pads.

So ho come they arent so dependent on the thickness? I thought I would have real trouble if i put a 5.1mm caliper on a 4.5 disc, for example. I suppose i can just adjust master cylinder sizes accordingly </div></BLOCKQUOTE>

this has no influence on the size of your master cylinders. they will auto adjust the pads to make contact with the discs. im not sure why they offer two different caliper sizes.

[Agent4573]

They make two different calipers to fit the rotor thicknesses because right now, if we let the pads wear down on our brakes, we would probably pop the pistons out of the calipers. They give you a rotor size because the pistons were designed to work in a certain range. If you put to small of a rotor into a caliper you may exceed the range of motion of the pistons. Like I said before though, the trade off is that we can only wear about halfway through our pads before we have to replace them. If we wore our pads down fully, the pistons and calipers would get seriously damaged.

[Alan S.]

i ran some calcs and im a frosh so im woundering in the bal park, my front system is useing a .625 master and ether dual piston 1.75 bore or single 2.75 does that make sence to you other break guys out there?

[Agent4573]

alan: a few other specs need to be known before anyone can agree or disagree. Whats your rotor size(need to know braking radius), what torque did you estimate to lock up your wheels, what pedal ratio are you shooting for.

A .625 w/ a 1.75 dual sounds about right for a system assuming a 20 inch tire and that a 4 to 1 or a 5 to 1 pedal ratio can be achieved.

[Alan S.]

8" rotars, around 800Nm torque(i built in safty factors to the cars weight) pedal ratio of 5.5 and 18 inch tires

[Alan S.]

also what is a resonable clearence between the rotars and the break pads under the asumption were makeing our rotars so they can be any size

[Agent4573]

what clearance are you talking about? Between the pad and rotor, you'll have a few thou i guess, depending on how far out of round your rotor is(leading to pad knockpack).

[Alan S.]

thanks agent, this stuf is pretty complex to jump into