I'm pretty sure I got this from Lee C. years ago
I noticed that the pads on the inside of the front caliper always seem to wear out faster than the outside pads. So, I started to rotate the pads every few thousand miles to get more even wear and longer life.
The inside pad from one caliper rotates to the outside of the other caliper, same for the other inside pad. This keeps the pad face wearing in the same direction on its new disc.
Anyone else do this? Any opinions on why this would be a bad thing to do?
DavidR.
I have not heard of anyone doing what you mentioned. I can see the logic in rotating the pads. Could maybe get a few thousand extra miles out of a set of pads.
Fred
Unless your discs are new they will have a profile which the face of the pad is worn to. When you swap them around it takes a while for the pad to wear to the new shape. During this time the brakes will not be very efficient due to the reduced contact area.
Also, pads should wear close to even.
Pads cost less than a couple of tanks of fuel and last a very long time.
I would not want to be needing my brakes in an emergency just after I had swapped them around.
Noel
Any resurfacing done on your discs? I just rebuilt my front/rear and because one cannot get discs turned, I resurfaced them with an angle grinder [~ 11,000 RPM] and a 100 grit paper. Turned out real nice and 100 grit leaves a rough enough surface that will break pads in faster. Of course I am putting on new pads. Should break in used pads better also.
That RPM with 100 grit??? I would have burnished it with 600 or higher. The 100 sanded surface will act like a file to your pads longer than your pads will smooth out the 100 grit.... Watch your pads frequently just to be safe... Now lets hope you did not make any low spots big enough to induce a pulse effect... You will see them as spots that are not effected by the brake pads after a few 100 miles or so.... Maybe more....
Quote from: bigbore2 on September 10, 2012, 08:44:22 PM
Any resurfacing done on your discs? I just rebuilt my front/rear and because one cannot get discs turned, I resurfaced them with an angle grinder [~ 11,000 RPM] and a 100 grit paper. Turned out real nice and 100 grit leaves a rough enough surface that will break pads in faster. Of course I am putting on new pads. Should break in used pads better also.
I'm speechless. Why?
Did you have the wheel spinning while you, er, um resurfaced it?
I will verify the rpm of the angle grinder. Yes I have done this before on my 900 disc and had good results. 125 grit paper I felt left the disc surface too smooth, as that was the grit I started with. Will keep you posted how this turns out as I am currently having a little problem bleeding front.
Quote from: bigbore2 on September 11, 2012, 06:15:02 PM
I will verify the rpm of the angle grinder. Yes I have done this before on my 900 disc and had good results. 125 grit paper I felt left the disc surface too smooth, as that was the grit I started with.
Err, Ummm, what is the shank size of said grinder and or the disc diameter????
Hi David.
I have not noticed uneven pad wear on my 86 over the years.I wonder if uneven wear is common on the later floating disk/four pot caliper design?,or maybe a caliper rebuild may be in order?
Cheers :drinks:
Jeff P
Quote from: flips on September 12, 2012, 02:51:25 AM
Hi David.
I have not noticed uneven pad wear on my 86 over the years.I wonder if uneven wear is common on the later floating disk/four pot caliper design?,or maybe a caliper rebuild may be in order?
Cheers :drinks:
Jeff P
No, on my '93 when 1 of the 4 pads hits metal the other 3 are about cigarette paper thickness.
I did o'haul them when I bought it because they were seized, the PO never used them, "especially in an emergency" !!!!!!!!!
They have worn dead even ever since. If you think about how they work, so they should, unless something's sticking.
Noel
I see this on auto pads all the time, but with their low tech calipers, the inside pads wear quicker because the piston(s) are pushing directly on them.
I don't remember if I saw this with the stock 2-piston calipers, but I have noticed it with the monoblocks. Also, I don't usually have to replace front pads all that often. My '85 is still using the pads that came with the monoblocks when I installed them about 10 years ago.
Just over the weekend, I did this rotation (actually more accurately a shift in position) with the pads on my FZ1. Still using the stock pads at 20Kmiles and the inside pads were slightly more worn that the outside pads. It's not a big difference, but it is noticeable.
I'm not sure why, but the front brake performance seemed to be getting a little "spongy" lately. After the pad swap, the brakes feel much better. Probably the result of exercising the pistons a bit and cleaning a little of the crud off of them.
One of these days I'll get around to installing the SS lines on that bike.
DavidR.
Angle grinder is small with the disc of the 4 1/2" size. RPM is 6000. I used 100 grit because even the 125 grit took too long to get anywhere. 100 grit does the surface reduction quickly and easily, but not too aggresive. I either just used the weight of the grinder itself or light pressure on the grinder to remove metal. The disc surface is very hard when polished for years with pads. I will keep an eye on pad wear as the surface may need to be finish polished with a finer grit as was suggested. I had the disc off the wheel sitting on a pail for the resurfacing.
The Cycle Brake people recommend "cleaning" the surface with 600 grit. Just an easy swirl over the entire surface and a flush with water.
I don't think you need to remove rotor material, enough of that gets done gradually by the action of the pad. The desire is to simply clean the surface of the disc when installing new pads.
DavidR.
I hear you, but I had a lot of grooving in my discs and wanted to eliminate most of the grooving. I agree that some say grooving gives one more surface to brake with. But I had enough material to refinish this even after a bike with 34,000 miles on it, with the back disc having the deepest grooves. PO was a back brake user and i finally learned from riding motocross to be dependent on the front. I know 100 grit sounds extreme, but it is not, as I just looked over my discs and the surface is just rough enough to detect with running your fingerpad over it. When auto brake discs and clutch discs are turned, the surface is not left with any kind of a polished finish, it also has a surface roughness detectable by running your fingerpad over it, left there for the break-in of pads. I tried to simulate that and guess I got it just a little more rough than if it was turned. But I can refinish if it appears my pads are wearing to fast in the first 100/200 miles. I just also needed a project to do since I am not working at the present and had the time. And then my rear shock came in today and ... If anything, this web site is to blame for giving me the options of doing this in the first place. I can't just read about easy upgrades and then go to sleep at night.
Quote from: bigbore2 on September 12, 2012, 07:15:51 PM
I hear you, but I had a lot of grooving in my discs and wanted to eliminate most of the grooving. I agree that some say grooving gives one more surface to brake with. But I had enough material to refinish this even after a bike with 34,000 miles on it, with the back disc having the deepest grooves. PO was a back brake user and i finally learned from riding motocross to be dependent on the front. I know 100 grit sounds extreme, but it is not, as I just looked over my discs and the surface is just rough enough to detect with running your fingerpad over it. When auto brake discs and clutch discs are turned, the surface is not left with any kind of a polished finish, it also has a surface roughness detectable by running your fingerpad over it, left there for the break-in of pads. I tried to simulate that and guess I got it just a little more rough than if it was turned. But I can refinish if it appears my pads are wearing to fast in the first 100/200 miles. I just also needed a project to do since I am not working at the present and had the time. And then my rear shock came in today and ... If anything, this web site is to blame for giving me the options of doing this in the first place. I can't just read about easy upgrades and then go to sleep at night.
This is the very thing that worries me about someone reading this.
In experienced hands and with an understanding of what your doing you might get away with it, but the thought of someone attacking their discs with an angle grinder, because they read it on the forum, with a "100 grit cut off wheel" thinking hey, I can do that too and it doesn't even cost anything, is terrifying.
Perhaps it should carry a "DO NOT TRY THIS AT HOME" disclaimer.
People are free to post what they like, no matter how loopy, but we have a responsibility and should be cautious when it comes to suggestions on safety items.
Of the several thousand members here, there's bound to be a few bored, broke and itching for an FJ play owners who's mechanical knowledge is limited and could see somehting bizarre like discs being offered up to bench grinders or angle grinders with inappropriate discs being used inappropriately.
Noel
Perhaps I was unclear here, angle grinder with 4 1/2 inch plastic pad attachment one attaches pre-cut round sanding paper made for the plastic attachment for the purpose of finishing metal. NOT a grinding wheel, that would be impossible, I believe.
Quote from: bigbore2 on September 17, 2012, 04:13:43 PM
Perhaps I was unclear here, angle grinder with 4 1/2 inch plastic pad attachment one attaches pre-cut round sanding paper made for the plastic attachment for the purpose of finishing metal. NOT a grinding wheel, that would be impossible, I believe.
I wasn't suggesting YOU used a cut-off wheel, my point was, in the absence of detailed instructions, someone else reading the post might.
Impossible to use a grinding wheel you say? I've been a mechanic for 40 years, you would not believe what people do armed with little experience on the tools they're using, no understanding of the parts they're working on and just enough self confidence to have a go.
And, even a plastic mounting pad, as opposed to a rubber one (which is what I assumed you used), is pretty harsh and likely to gouge the metal.
I just have a problem with brake rotors and angle grinder in the same sentence.
A point we differ on and likely to remain so.
That's what's great about the forum, we are all entitled to state our views, even the pink stripers and ambulance drivers.
Noel
My point is that with the use of a grinding wheel, it would be impossible to get a flat, smooth surface on the disc, I believe. I am sure someone might try a grinding wheel, like you say, its amazing what people will try.
They no longer make a rubber pad at the store I bought my parts, only a plastic one. It is a little stiffer than I wanted, but it still flexed enough to satisfy me and get the surface finish I was looking for. I only wish I had a camera to do a photo of this work. I decided that if one cannot get a disc turned, this may well work as an cheap alternative to buying 3 rotors. We shall see how it turns out. Hope to have my shock mod. completed this weekend so I can put some miles on and see.
Maybe there's a good reason these disks are not allowed to be turned. They start out pretty thin and turning them may make them under-spec and subject to warping. What is the disk thickness now that you've 'sanded' them flat & smooth?
Arnie
Quote from: bigbore2 on September 18, 2012, 01:38:49 PM
I decided that if one cannot get a disc turned, this may well work as an cheap alternative to buying 3 rotors. We shall see how it turns out.
Unless they are horribly warped, I NEVER turn a disc. I stopped turning them on cars about 20 years ago. Usually the idiot running the machine just screwes them up. Haven't had any brake problems since then; bike or car.
DavidR.
Quote from: Arnie on September 18, 2012, 09:02:56 PM
Maybe there's a good reason these disks are not allowed to be turned. They start out pretty thin and turning them may make them under-spec and subject to warping. What is the disk thickness now that you've 'sanded' them flat & smooth?
Arnie
Quote from: bigbore2 on September 18, 2012, 01:38:49 PM
I decided that if one cannot get a disc turned, this may well work as an cheap alternative to buying 3 rotors. We shall see how it turns out.
New bike discs are only about 1mm thicker than min spec. No meat for turning.
I'm with David, turning modern car discs, which are now rubbish, is a waste of money and only makes them thinner and even more likely to warp.
Car discs are now made from crap metal (I know this) and are throw away parts, they have become consumables.
There was a time when you could expect discs to last the life of the car, our last car was getting new fronts yearly, and you can't even buy good ones if you're prepared to pay.
Porsche, for example, include rotor replacement at certain service intervals, regardless of condition.
I'm all for trying to eke out a few more K's from components but that doesn't include taking a handheld power tool to your discs.
I have never found the grooving that rotors develop over time reduces brake performance anyway, so there's nothing to be achieved.
Noel
Let's start with some technical data, here. 84-1100 with 34,000 mi.
[all info from 84-89 service manual]
Appendix lists new disc at 7.5mm
My before prep on rear disc was 7.38mm
Prepped disc is 7.34mm
In the chassis section, on page 5-5, min disc thickness is listed at 6.5mm however on page 5-13 in the exploded view, brake disc wear limit is shown as 7mm. I believe the 6.5mm the correct value as I read somewhere there is 1mm of total wear availble.
I am suprised that with 100 grit paper, I only removed .04mm, however as I was working the metal, I could tell it was VERY hard metal. I guess the grooving was not as deep as I thought it was. Also even though I started out with 100 grit, the paper wears down quickly and I finished with much smoother grit.
I am doing a rear shock mod. and could not get front discs measurement yet as back of bike is all torn apart and I did not think it a good idea to try and balance bike with rear wheel and front wheel off bike.
Hope to have mod done this weekend and will get that measurement first thing next week. FJMonkey- will follow your advice and watch wear on pads as they break in. It may be necessary to re-refinish with a finer grit.
It took about 300 mi to break in the pads. I just got back from a 3300 mi. trip and brakes are excellent. No pulsing. I put in stock Yamaha pads. Wish I had a camera to have posted this rebuild. All this for $28 as I had to rent a 4 1/2 in. die grinder and buy the disc adapter and the paper. Harbor Freight 4 /1/2 die grinder is less than $20. New Makita is $40.