| Author | Message | ||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 521 Registered: 5-2002 |
Bill, Agreed, that's why it's called braking torque  When you do the free body diagram the reactions at the ball joints or a-arm mounts are independent of caliper mounting location. The only thing that changers are the internal stresses in the carrier. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 466 Registered: 5-2001 |
Charles, I don�t think the conclusions you draw in your post concerning loads transferred to the suspension, are correct for breaking loads due to the caliper. The suspension is not directly affected by break application, only by weight transfer due to the chassis center of gravity. When the caliper clamps down on a disk, the retarding force acting on the disk is balanced by the caliper, which in turn is solidly bolted to the hub carrier. The result is the hub carrier will want to rotate with the disk but cannot because of the suspension arms. The force applied to the hub carrier is rotational in nature. There is no up or down or fore and aft force applied to the disk, no matter how the caliper is oriented on the hub carrier. I think the only real constraint in orienting the caliper is the pain one is willing to endure with regard to break fluid bleeding. The break bleed fitting should be situated at the highest point in the hydraulic system to facilitate removal of entrapped air. | ||
| Rob Baylor (Baylor308)
New member Username: Baylor308 Post Number: 32 Registered: 11-2002 |
I you can send me a sample of a 360 parking brake I will produce a similar design for a lot less than Brembo would charge. Rob Baylor www.ultimatepedals.com [email protected] 310 798-1434 | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 177 Registered: 3-2002 |
well back to the drawing board on the parking brakes--Some of you may remember Eric Dahl from Brembo. He posted here a few times about brakes so I contacted him looking for a set of 360 Modena parking brakes. He quoted me on them but has since left the company and Brembo is now trying to charge me tripple the cost...grrrrrrrr. Anyway--Anyone know of any mechanical calipers other than the Wilwood design? | ||
| Dr Tommy Cosgrove (Vwalfa4re)
Intermediate Member Username: Vwalfa4re Post Number: 1167 Registered: 5-2001 |
That explanation sounds logical. I realize now that you stated earlier the REAR was the one you moved, not the front. I was confused for a moment until I re-read your earlier post. Thank you | ||
| Rob Baylor (Baylor308)
New member Username: Baylor308 Post Number: 30 Registered: 11-2002 |
Another reason is the caliper needs to be oriented with the bleed screw at the top of the caliper to remove any air from the system. Bleeding the brakes with a top mounted caliper would require removal of the caliper from the upright, a PIA. Rob Baylor www.ultimatepedals.com [email protected] 310 798-1434 | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 176 Registered: 3-2002 |
from an engineering standpoint calpiers should always be either in front or behind--NEVER top or bottom. Follow me here-- a brake pad presses against a rotor with lets say 5000lbs at a distance of 10 inches from center of hub(this would be a huge wheel but the numbers are easy to work with). producing a torque or anti-torque if you wish of 50,000in-lb...NOW the rotor itself will also be applying an initial 50,000 in-lb counter force to the pad (equal and opposite reaction) thus forcing the caliper and pad to move somewhere. if caliper is on top or bottom--teh suspension is trying to move front or back--BIG NO-NO. Ideally--front calpier mounted in rear helps push front of car UP and a calpier on front of rear rotor helps pullcar DOWN in the back--thus acting counter to the nose down-ass high braking attitude of all cars.---granted--THIS IS A GREATLY OVERSIMPLIFIED DISCUSSION AND THERE IS A LOT MORE TO THE CALCULATIONS BUT THE PRINCIPAL IS SOUND.  | ||
| Dr Tommy Cosgrove (Vwalfa4re)
Intermediate Member Username: Vwalfa4re Post Number: 1166 Registered: 5-2001 |
Charles, I have a question: You mentioned that you moved the calipers to the front of the rotor "where they should be". I remember reading a tech Q&A letter to Road and Track a few years ago that the caliper position on the rotor made no difference and I have always wondered about it. What difference do you feel it makes? BTW, I am not disagreeing with you, I am just curious. I really don't know enough about these things. | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 175 Registered: 3-2002 |
probably about 3000/ 4 wheels. but I am concerned about if i need to get liability insurance here--I could also sell my bracket drawings and kit plans for a lot more reasonable figgure and let you build them yourself. hoping to get some local folks to try out the car soon for some feedback | ||
| John_Miles (John_miles)
Junior Member Username: John_miles Post Number: 78 Registered: 7-2001 |
What kind of price point are you aiming for, Charles? | ||
| Paul Sloan (Sloan83qv)
Member Username: Sloan83qv Post Number: 569 Registered: 3-2001 |
Charles, I am still interested in complete Kit! Paul [email protected] | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 173 Registered: 3-2002 |
I am considering making this as a kit--anyone interested? | ||
| John_Miles (John_miles)
Junior Member Username: John_miles Post Number: 77 Registered: 7-2001 |
That looks like a beautiful piece of work, Charles. I recently had my 308's calipers "rebuilt" by a highly-respected local (Seattle) shop. Unfortunately, instead of rebuilding them, the shop replaced the calipers and pads with some cheap non-OEM parts. Now I get a loud clicking/clunking noise from the wheels about every fourth time I step on the brakes. The shop owner: "Oh, that's just excessive play in the pins that hold the pads. All 308 brakes do that." Um, yeah, all of them except for the ones I've put about 50,000 miles on.  So I'm eventually going to have my regular tech put OEM-spec calipers and pads back on the front wheels.... unless there's a tried-and-true, non-clunking aftermarket alternative that doesn't cost an arm and a leg. | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 172 Registered: 3-2002 |
PS--even with a background in mechanical and automotive engineering--It took me about 8 months to get all this put together--probably 20-30 hours just doing measurements and CAD drawings | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 171 Registered: 3-2002 |
Alan--am still trying to figgure out how to get the willwood mechanical to work--plus it is a royal pain to build a bracket for it since it is a "floater" A bit of a warning here--If you decide to upgrade brakes--- 1) adding new brembo (or other) rotors will do no good unless you get better calpiers and/or larger rotors. 2) if you go with a new system--do the calculations and comfirm that you are not changing the bias ratio. and lastly 3) if you have 14" wheels--make sure that they will fit inside the rims--i had a 14" spare and had to sell it off and get a spare with a 16" rim. | ||
| Alan Ing (Alan)
New member Username: Alan Post Number: 5 Registered: 2-2002 |
Charles, thank you for the information. I was under the impression that the Wilwood spot parking caliper uses a forward/back cable pull and not a cross pull like the 308. Did you come up with some sort of scheme to redirect the cable? Just if anyone is interested. I happened across precisionbrakes.com the other day (I have no connection with them) and called the guys up. They feel they can provide a 308 front brake set up using Wilwood calipers and a custom rotor/hat combination for a 308 for approximately $1,300 including pads (Providing I send them my spindle). For the rear brakes, they thought they could provide a cross pull style PBR caliper set up and rotor/hat combination for around $1,500 or so. Seems like they also do group buys. I'm not trying to sell anything for them, but it is the first site that I came across that is willing to make a custom big brake set up at a reasonable cost. They seem to have all sorts of options. | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 165 Registered: 3-2002 |
Parking brake--NO. I currently have 1 set of willwoods and also have just ordered a set of Brembo 360 Modena Mechanical calipers to try. On the hubs of the 308's there are "ears" on front and back. I had to drill and tap the extra set of ears anf am currently working on bracketry to see which will be easier to use. By the way. I moved the rear calipers to the front of the rotor where they should have been anyway and will be locating the parking caliper at the rear --perfect for using the existing brake cable. | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 164 Registered: 3-2002 |
keeping it in the most simple form--you need to calculate the torque applied by the caliper piston to the rotor. Use the caliper piston diameter and the length from center of hub to the center point of the brake pad. The size of the brake pad actually makes little to no difference except for heat dissapation. For example--308 gtsi rear uses a 10.9" rotor and the center of the pad is about 4.45" from the center of hub. The front numbers are slightly different and comparing these you come up with a ratio to work with....NEXT.. select new calipers that close to this ration and ALSO will fit without major modifications(this is the hard part). Then lastly, calculate the exact daimeter to have the rotors machined to get the ratio just right. | ||
| Rob Baylor (Baylor308)
New member Username: Baylor308 Post Number: 28 Registered: 11-2002 |
Charles, I would also appreciate as much detail as you can on the components you selected. Also when you say you "backwards calculated everything to keep the same ratio so no change in master cyl or bias valve" could you provide the details as well. My 85 308 QV brake system is as follows: front rotor diameter 280mm front caliper piston diameter 44mm front pad outer swept diameter 280mm front pad inner swept diameter 173mm front pad area 3779mm^2 rear rotor diameter 280mm rear caliper piston diameter 34mm rear pad outer swept diameter 280mm rear pad inner swept diameter 196mm rear pad arae 2416mm^2 How do these US 85 QV stock system measurements compare with the stock measurements from your car? Thanks, Rob Baylor www.ultimatepedals.com [email protected] | ||
| Alan Ing (Alan)
New member Username: Alan Post Number: 4 Registered: 2-2002 |
Charles, I would very much be interested in the details of your brake system. Since I have to rebuild my whole brake system, it might be nice to just upgrade and replace. By the way, were you able to mount a parking brake? | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 162 Registered: 3-2002 |
I designed and built my own system 12.2" rotors in front, 12.0 in rear with 4 piston calipers all around. backwards calculated everything to keep the same ratio so no change in master cyl or bias valve needed.  | ||
| Lawrence Coppari (Lawrence)
Member Username: Lawrence Post Number: 618 Registered: 4-2002 |
Atlantaman, do you go to driving events at Road Atlanta? | ||
| Dr Tommy Cosgrove (Vwalfa4re)
Intermediate Member Username: Vwalfa4re Post Number: 1160 Registered: 5-2001 |
I just installed the Brembo kit on my 308. BIG BIG difference on the track. (The new Barber's Motorsport track to be exact - 4.1 miles from my house :-) | ||
| John_Miles (John_miles)
Junior Member Username: John_miles Post Number: 75 Registered: 7-2001 |
What brake system did you install? I may be in the market for one. | ||
| Charles I Claussen (Atlantaman)
Junior Member Username: Atlantaman Post Number: 161 Registered: 3-2002 |
Finally got my car back on the road with my new brake system and WHEW WHAT A DIFFERENCE. I know several of you were waiting to see how it worked out( Paul in particular )--- Well it stops faster than my 911--damn near launched me thru the windshield. Paul, call if you wish, or if you get to atlanta come see it. |