Front Brake Caliper ???

BlackSC

Registered User
Hey maybe somebody on here can help me out on this one. I was getting a pretty bad back and forth shaking of the steering wheel under braking, so I got in and took the rotors out, had them turned. I guess the guy who turned them for me said only one of them was warped - he thought maybe one side's caliper wasn't traveling correctly.

I put it back together after cleaning the two long-shouldered bolts that the caliper travels on and I put a little lithium grease on those. None of them looked rusty or anything. Anybody want to give me an idiot's guide explanation as to what is going wrong with my brakes? or how exactly they work, for that matter? Am I thinking correctly on both of these situations?

Brian

BTW the car stops smooth as silk (after grinding the rotors)...I just don't want to have to buy new rotors until I can put some real stopping power under the car!
 
Did you check the pins on both sides? Also, your caliper piston on that side might not be as free moving as the other side. Maybe an overhaul of that caliper might be in your future. But, I have heard in the past that not all pads/rotors wear exactly evenly. In fact, one of these quick change brake places guy told me that every vehicle he's worked on has the left front brake pad/rotor wears sooner. I'm not sure why, but two cents. If I were you, I would start pricing new stock replacement rotors, because I have heard once you turn our stock rotors, they will warp SIGNIFICANTLY sooner than they did before. After years of reading posts on this board exactly about this, I bought new rotors as soon as my old rotors warped (3Xk miles). New rotors can't be that bad as far as cost...I think they are like 30 bucks each? I know turning them is cheaper (I paid 6 bucks/rotor but I had crossdrilled after market stock replacements), but you might be taking them off in less than a year. I hope that helps.
 
Yeah, checked all four pins on the front, two per side. They all looked good. Yeah I've read that same thing, that the rotors will warp sooner. If they'll go good for about a year and a half (10k miles) or so I will be putting on something a little bigger anyway.

Forgot to mention, the rubber dust boot on the left side's top pin is ripped. But like I said the pin looked good so I didn't think that was the problem. I was quoted something like 50 bucks for a new caliper, I assume that would have a good dust boot attached. Pads looked good and even, I didn't measure but they all looked like they were even. Not even thinner on the front end, which I've seen sometimes.

Here's another question - whoever did this last had so much loctite on the bolts holding the little caliper frame on that I just about killed myself getting them out...I cleaned em up and stuffed them back in without any new loctite - bad idea? Man I just hate bolts when they're on like that, especially in the wheelwell where you can't get any leverage. Course I'd hate to have my caliper go loose too...is loctite a necessity?

Brian
 
I don't know right now (at work). I can check when I get home, but I do know if you do use it, you are only supposed to put a drop or two (not much) at least three or four threads from the bottom. FYI, I don't even take my pins out when doing pads/rotors. I unbolt the entire caliper and slide it off. Before I put it back on, I open up the gap between the pads with a C clamp.
 
Thanks...

Yeah, that'd be good...I need to get back under there again anyway. Didn't have time to fix it but whoever replaced the speed sensor last put the brake line on the wrong side of the speed sensor wire and now it's rubbing. Guess it wouldn't be hard to put a few drops on those bolts at the same time - just not as much as the last guy slathered on!

Maybe that's half my problem, I was taking everything apart to get it off, probably not good for keeping dust and dirt out of the pin channels...

Brian

BTW Get back to work! :D :D :D
 
Last edited:
Well, I only take apart what I have to (ususally, except for the problem I'm having right now for mine). But, you can't beat following the manual. I can't tell you how many times I have not followed the manual as far as dissasseembly/assembly and ended up scratching/denting/mutilating something that wasn't. I am a technical writer for aircraft and I know when I put something in manuals, you HAVE to do it! Now, the people at Helms probably don't follow the same policies and I do think that the manual does tell you to slide those pins out to take it apart, so I think you are doing it right.
 
BlackSC said:
Here's another question - whoever did this last had so much loctite on the bolts holding the little caliper frame on that I just about killed myself getting them out...I cleaned em up and stuffed them back in without any new loctite - bad idea? Man I just hate bolts when they're on like that, especially in the wheelwell where you can't get any leverage. Course I'd hate to have my caliper go loose too...is loctite a necessity?


How hard do you drive your car? Brake pads and rotors do not actually stop the car, they transfer forward motion into heat. When the rotors (or drums) are turned they lose mass which allows them to heat quicker when compared to the previous mass. If you drive hard on OEM brake rotors that have been turned you will warp them easily. The basis for a big brake kit is not to stop the car better but rather to keep the brakes cooler longer so that the car will last an entire race versus a few laps. If you look inside the wheels of the top autocrossers in the country you will see itty bitty rotors with teeny tiny pads to reduce the weight because they do not the heat transfer resistance of the larger rotor. I plan on using the larger brakes from the later M cars on my 6 series because I plan on using it on track days.
 
Not too hard....

My car lives like a policeman...hours of boredom punctuated by sheer moments of terror :D . But usually not too hard on the brakes. I really haven't looked into aftermarket brakes too much but I thought bigger was better? What you're saying makes perfect sense physically though.

I'm not sure if these are the oem rotors because the car has just over 80k miles on it and the rotors measured out to stock thickness - I think at least, they were well over the minimum (24.7 mm).

But like I said this car rarely is driven too hard. The only part the front brakes probably don't like is keeping the car stationary while I burn off the rear tires! But then that's static friction and so it's probably not that bad on the rotors.

Brian
 
A good buddy of mine is a brake system engineer and I fought the bigger is better fight to the death... after I was reincarnated he whooped my hiney a little more then let me off the hook (for the time... you know how engineers are :rolleyes: )

One recommendation that I have for people who do not drive their cars a lot (10k in 18 mos? I run 10k in 4 mos!) is to annually flush the brake system. I bought a vacuum bleeder just for that task. It really makes everything last longer and the pedal feel is fantastic.
 
How much did that brake bleeder cost? My pedal feel has always been fine, but I'll try anything (if it's cheap!)

Yeah I have a Chevy to beat on for the rest of my mileage. I run quite a bit but manage to keep the SC off the streets. Mostly because the Chevy is the only one that will drive five thousand miles and not break down eighteen times.

Brian
 
The basis for a big brake kit is not to stop the car better but rather to keep the brakes cooler longer so that the car will last an entire race versus a few laps.

I will have to disagree with this to a certain extent....all the rest of what you said was correct.

Bigger brake kits are so bigger rotors can be grabbed at a distance farther away from the centerline of the rotor, there by requiring less force to slow down same mass but, bigger brake kits also usually have brake pads that dissappate heat better. Bigger brake kits do not reduce heat. Pads, crossdrilled or slotted rotors, brake cooling deflectors, etc. reduce heat. Think of a bicycle tire spun by you as you hold it off of the ground. To stop it, would you grab the wheel somewhere around the axle, or would you grab it at the most furthest radius from the axle?
 
That's true...torque is directly proportional to radial distance, and that's basically what the brakes are doing, providing reverse torque against the direction of motion of the rotor. But as for cooling, a lot of it has to do with the angles and number of finned spaces in between the rotor sides, right? I know in Nascar they run different numbers of cooling fins depending on the track...don't know if they change up the sizes of the rotors too.

Brian
 
Seldom do you see slots on racing rotors or drilled rotors, you will see internal vanes on vented rotors. The reason for slots was to help the pads degas at temperature, the rotor acts as the heat sink the pads as the conduit for energy transfer. One of the possible benefits of a larger rotor is anti-torque, but in the same reference you used, If you used the same clamping force with your finger to try to stop a bicycle tire spinning at 100 RPM the length of time required to stop it would be determined on the resistance your skin had the the frictional heat created by the energy transfer. Generally the energy reduction would be the same. if you stick your finger in a ceiling fan near the rotational pivot the torque you would experience would not be the same as if you would have stuck the finger in at the end of the axis. The leverage from the lenth of the blade would amplify the torque. The heat energy created from transferring that torque would be absorbed more easily by the larger rotor resisting warpage but not necessarily stop the car in a quicker manner. Please call Grassroots Motorsports at 888-676-9747 and ask for back issues, when the guy or gal in circulation picks up the phone askto order the Feb 2001 and Dec 2003 issues of the magazine. Inside these articles there are basic brake system information articles by James Walker Jr., who is another brake system engineer that is also an ITA racer in the SCCA.
 
Back
Top