Cutting retainer clip grooves into caliper pistons?

I have a fast franks quick change front on my 09 zx6r. Its super easy to get the wheel off without removing the calipers. However, I have never been able to get it back on without taking the calipers off...

I never beveled my pads or anything so that may have something to do with it. the 09-12 zx6r calipers have 4 pads, and they seem to move around a lot in the caliper, this catches the rotor on the way in. I have a set of 13+ calipers, but those are illegal to run in super stock, and I would then need to buy 3 sets of rotors for all my wheels..

I am going to buy some magnets to put into the pistons, but i'm not a big fan of using silicon or rtv to keep them in place. So I've been thinking of buying larger magnets, machining them down to a close fit to the ID of the piston, and then cutting a groove near the top of the piston to install a retainer clip. This should keep the magnet in place and i would have to worry about cooking RTV/Silicon out of my calipers. Its also cleaner and serviceable.

Have any of you done this? Thoughts? Am I just thinking too hard about this and I should just put a small bevel on the leading edge of the pads and glue the magnets in like every one else?

It's just my wife and I running the show, shes not wrench savvy at all... For WERA events I run 4 races a day and CCS events I will run 4-6 classes. So, changes in weather like we had at PIRC are kind of stressful switching wheels and what not. Just looking to help myself be more efficient.

 

machining magnets will be a b1tch. you could wire edm them, but magnets being so brittle, you can't even properly hold them in a vise...

 

It is a bitch to machine them.. I've had some success using collets instead of the jaw vise though. I don't really know the size i'd need off-hand anyway. I may be able to just purchase something close enough, and the retainer clip would draw the magnet close to the face anyway..

 

Why not use some heat resistant foam and adhesive (double sided tape) to secure the magnets? You really only need to keep the magnets secured to the back of the piston to prevent them walking out, right? I would think that there has to be a reasonable foam and tape combination that could be used to keep the magnets inside the piston. Or machine a plastic insert (3D print?) with an embedded magnet, just make it an interference fit to the piston as well as a snug fit to the magnet. A design might be an inverted piston with a lip that secures the magnet in place. Bunch of ideas rattling around in my head, involving springs, levers, molly screws, a couple of ball bearings...

 

Think the method I would use is to turn an aluminum disk to a light press fit to the caliper piston ID. Add a threaded hole to the center, and bolt a magnet to that. Add an extra hole to the aluminum so you're not trapping air behind it.

Or maybe find a flexible strip magnet that could bend to the ID of the piston. If the piston is magnetized, wouldn't it grab the brake pad plate well enough?

 

Don't the magnets eventually shatter from all the heating and cooling? Glue may keep the pieces from being a real problem while riding.

 

Upon reflection, you likely wouldn't have to machine a groove in the piston for an internal C Clip to work. Just get one that's 10-15% larger than needed and friction will likely do the rest. You don't need a lot of retaining force in this application. If the piston has an internal diameter of 25mm, just get a 27-30mm internal c clip, circlip, snap ring, or retaining clip of your choice, and have at it. You will need a magnet with a diameter that's similar to the piston, but you already knew that.

 

I would be nervous about the clip somehow working ts way out though. I feel like the magnet would do well at keeping it wedged between the pad and magnet if that were to happen. However, I can't guarantee that. A groove wouldn't be hard to do. I was more curious and made this post because to me, it seems like a really good idea to use a retainer ring instead of glue/silicon. But I only ever hear of people gluing them in. I have 8 pistons from a spare set of calipers just sitting around, and I feel like I cold prolly knock them out in an hour on the HAAS TL.. I just didn't want to waste good pistons...

 

What you need is a filler to keep the pads in place when a rotor isn't present.
A couple simple sandwiches, with the "meat" being a piece of plastic(?) that is the thickness of a rotor and the "bread" being some means to align itself around the pads/pins, would give you something to wedge between the pads as you push the rotors out of the calipers with your new "tools". When you put the wheel back on, the rotors push the wedges out from between the pads.
A shit-ton less work than machining grooves in 8 pistons, finding magnets, not fucking them up as you attempt to size them, finding clips, etc., etc., etc.

 

heat is the main point where at over a certain temp the magnetic effect will be rendered ineffective

spacer when rotor is out sounds like the best option

 

Also interested in this topic. Not being able to change from rains to slicks quick enough cost me a race at PIRC.

Just did my own captive rear caliper to help with the rear but the front has me scratching my head. I'm looking at the FF conversion to not have to remove a caliper, but the pads are finicky by themselves. The spacer idea is interesting...

 

I'm surprised that FF, EMR, some shop like that doesnt already make them. Id buy a set right now.

 

Go for it! I like the groove idea, but since I don't have a HAAS at my disposal I need to limit my ideas to my constraints.

 

I just use a small cardboard spacer. You could get more elaborate/use something more robust. They keep the pads apart. When the rotors go in they push the spacer out. Easy.

 

does your cardboard at least have a Brembo sticker on it or something?

 

Funny! Before the spacer, I had the same problem - "wtf, how hard is it to get these rotors back in". Looked at the magnets, asked around - too much of a hassle. Cut 2 pieces of cardboard, 30 sec later, that was easy. Still use the same pieces after so many wheel swaps.

 

Cardboard for me if I remove the front wheel (mountain bike)

 

I think I'll do this...with a sticker.

 

Cardboard or wood, yeah that all works awesome. But on TV at the Suzuka 8 are you cool? Sorry not so much. The $300 custom metal piece, yeah that looked cool but didn't work so good.

I don't have any secret for you. Maybe expanding foam? Don't know what it's temp range is but would look into it.

While our endurance caliper had magnets they also were custom machined pistons that we only used at Daytona in the US. "extra weight..." everywhere else.

A good rider is worth 5 seconds, but 5 pounds is only worth 0.5 seconds. I know pro riders worth at least 100lbs, either way. So a magnet isn't worth the time you think it is.

 

This. Don't modify the piston, build a press-fit insert. Make it out of steel, not Al, so that the expansion rates are the same. Turn the insert so that the OD is .002" larger than the ID of the piston, bore and ream a hole in the insert to accept the hi-temp-glued magnet (that way you don't have to machine the magnet), then heat/freeze and press in. Drill several air relief/lightening thru holes. Jolly day.

I think I'll try doing this myself.