Spacers for mounting brake calipers

[spokewrench]

My Radmission became my backup bike 8 months ago, when I bought a new e-bike. I'd ride it several times a month. When hot weather came, I brought the battery indoors so it would stay cooler. That meant I rode the Radmission less.

A few days ago I put in the battery and rode it. The mechanical brakes had always worked very well, but now they were very poor. Braking several times from 20 mph improved their performance, but the pads wore incredibly fast.

I've discovered that automobile pads should be stored between 10 and 25 C and between 40 and 60% humidity. Hotter or damper storage will cause them to soften. Colder or drier storage will make them brittle. I guess a few weeks of high humidity without riding to heat the pads up allowed moisture to soften them. I guess a bike ridden less could wear out pads faster than a bike ridden more.

I've always removed calipers to change pads. I can clean and inspect and, before tightening the mounting screws, adjust and align the calipers with the new pads. On several occasions, I've had spacers repeatedly fall off the screws each time I tried to put the caliper back on. Those spacers are weird to me. The ones on the Tektro Aries have a metal cup over a sort of metal washer. If an assembly falls off I have to figure out the proper reassembly. A dab of silicone RTV can hold them in place.

How do these spacers work? When I remove a caliper, would it be better to install new spacers? Are they available?

 

[m@Robertson]

You mean the little metal clip things that look like two 2-pronged forks joined together at the 'handle'? Usually those come with a set of pads.

edit: here I just googled 'tektro brake pads' and this came right up. These are the pads I bought way back when I used brakes with Tektro style pads. You can see the spacer thingie comes with them.

Amazon.com

 

[spokewrench]

You mean the little metal clip things that look like two 2-pronged forks joined together at the 'handle'? Usually those come with a set of pads.

edit: here I just googled 'tektro brake pads' and this came right up. These are the pads I bought way back when I used brakes with Tektro style pads. You can see the spacer thingie comes with them.

Amazon.com

Here's what I mean. Mine looked like a cup and washer, while this is a concave washer with a convex washer. In this case, I'd have to buy 4 screws for $24.

Shimano 32.1mm Disc Brake Caliper Fixing Bolt with Adjusting Washer

Check out the deal on Shimano 32.1mm Disc Brake Caliper Fixing Bolt with Adjusting Washer at Bikeman

www.bikeman.com

If they're aluminum, I guess they're made to deform, so replacement sounds like a good idea. It looks like nobody does.

 

[m@Robertson]

Here's what I mean. Mine looked like a cup and washer, while this is a concave washer with a convex washer. In this case, I'd have to buy 4 screws for $24.

Shimano 32.1mm Disc Brake Caliper Fixing Bolt with Adjusting Washer

Check out the deal on Shimano 32.1mm Disc Brake Caliper Fixing Bolt with Adjusting Washer at Bikeman

www.bikeman.com

Ohhhh ok totally different thing than I thought you were talking about. Those are called semi-hemispherical washers and they should not need replacement, ever. If your brakes use those, its important to know that your brake caliper mounting adapters have been downsized to accomodate the extra height those things require. A mismatch of a caliper mount that wasn't shortened to account for those things (or the reverse, using a shorter one without the adjustable washers) can make your life miserable trying to get the caliper to properly face the rotor.

The washers are meant to snuggle up together so they sorta kinda spoon. Then you tighten down the M6 bolt that hold the caliper and washers down onto the adapter mount.When you have half-snugged down the whole assembly, the theory is you can use the play they give you to align the caliper just right on a side to side axis so it doesn't rub the rotor.

In my personal experience they are far more trouble than they are worth. A proper brake mount should be square by bolting directly down onto the mounting adapter. And if its not, you have a much bigger problem. Magura calipers and adapters are both squarely faced so mounting is very straightforward and never needs these things. I was aware that Avid brakes and adapters were sized for use of these things, but I thought that was it.

If they're aluminum, I guess they're made to deform, so replacement sounds like a good idea. It looks like nobody does.

No they are not made to deform at all. You are thinking of crush washers. If you crush one of these poor little things you're going to have some serious problems.

 

[m@Robertson]

Also if I google 'Tektro brake mounting kit' from what I am seeing Tektro does not use this kind of washer system. Maybe Rad decided to improve things, by which I mean screw them up. Certainly not the first time Rad has made the wrong choice insofar as brakes are concerned on their products.

Also I googled up the Tektro Aries caliper and they have flat, squared surfaces on the caliper. So having just one cupped washer is not something you have to do because the caliper underside is curved (based on current non-oem Tektro Aries).

 

[spokewrench]

Also if I google 'Tektro brake mounting kit' from what I am seeing Tektro does not use this kind of washer system. Maybe Rad decided to improve things, by which I mean screw them up. Certainly not the first time Rad has made the wrong choice insofar as brakes are concerned on their products.

Also I googled up the Tektro Aries caliper and they have flat, squared surfaces on the caliper. So having just one cupped washer is not something you have to do because the caliper underside is curved (based on current non-oem Tektro Aries).

Thanks. I didn't find "tektro brake mounting kit," but I did find Tektro Aries MD-300 kits, and the screws don't have spacers. My back caliper screws have two 4.5mm spacers each, under the head and under the caliper. Changing spacers could move the caliper + or - 4mm radially. Maybe the bike was made that way to accommodate caliper brands that aren't identical. I don't know why they made the spacers that way. I could make one with three 1.5mm M6 washers.

The front caliper uses four screws: two to mount the adapter bar to the bike and two to mount the caliper to the bar. It has no spacers. Maybe you use a different bar for a different radial distance.

 

[m@Robertson]

Yeah it sounds like Rad kludged together their mounting setup. I'll bet they had a supply of undersized adapters and rather than buying properly sized ones they cut those spacers.

I didn't find a Tektro mounting kit either thats just what I googled, followed by image search and using that to see the underside of the calipers, and the bolts Tektro uses factory stock.

If you google 'Avid brake mounting kit' you will see exactly what I was looking for, knowing that Avid sells them.

Here's a result from Jenson USA. I also see that Shimano uses these as well, but only for a 170mm rotor which must be a special thing. You can see linked products if you scroll down a little.

SRAM/Avid Disc Caliper Mounting Hardware | Jenson USA

www.jensonusa.com

The header says SRAM/Avid but I think SRAM only uses them on a specific caliper. I had a set of quality SRAM hydros on my BFD and they had none of this extra crap hanging off the mounts.

 

[spokewrench]

With bedding and adjustment, the old pads work great, but they appeared to be down to 1.5mm. The new ones will arrive soon.

Four months ago I bought some eye screws rated at 650 pounds. Hoisting a bike makes a job like this easier.

 

[spokewrench]

Ohhhh ok totally different thing than I thought you were talking about. Those are called semi-hemispherical washers and they should not need replacement, ever. If your brakes use those, its important to know that your brake caliper mounting adapters have been downsized to accomodate the extra height those things require. A mismatch of a caliper mount that wasn't shortened to account for those things (or the reverse, using a shorter one without the adjustable washers) can make your life miserable trying to get the caliper to properly face the rotor.

The washers are meant to snuggle up together so they sorta kinda spoon. Then you tighten down the M6 bolt that hold the caliper and washers down onto the adapter mount.When you have half-snugged down the whole assembly, the theory is you can use the play they give you to align the caliper just right on a side to side axis so it doesn't rub the rotor.

In my personal experience they are far more trouble than they are worth. A proper brake mount should be square by bolting directly down onto the mounting adapter. And if its not, you have a much bigger problem. Magura calipers and adapters are both squarely faced so mounting is very straightforward and never needs these things. I was aware that Avid brakes and adapters were sized for use of these things, but I thought that was it.

No they are not made to deform at all. You are thinking of crush washers. If you crush one of these poor little things you're going to have some serious problems.

I read online that Shimano invented the concave/convex combination to go under the bolt head. The purpose is to apply even pressure on the caliper even if the bolt is bent or otherwise misaligned.

I removed both calipers from my other bike to be sure the factory had mounted them correctly. The front one was right. The back one had only a concave washer under each bolt head. One convex washer was missing. The other was between the caliper and the mount. I put that with the concave washer, remounted the calipers, and painted a section of each disc with a red felt-tip pen to see where the pads were sweeping. The rear pads were about 2mm farther from the axle than the front pads. Both were within the "braking band" of their discs, so I guess the system allows the bike manufacturer a little leeway.

 

[m@Robertson]

Yeesh. How do you bend a brake caliper bolt? I guess you could hit it with a hammer or bounce the bike off of a rock, but at that point you'd replace the bolt, which is nothing special: Just a garden variety M6 socket cap whose length is in the 15-20mm range. And with no washers, there's no length of exposed bolt to bend... Creating a washer system to salvage a bent 50-cent bolt doesn't sound right.

Here's a pic of a BB7 caliper with the bolts and washers threaded on in the proper order. The lighter-colored ones are the concave side. The ones in direct contact with the caliper are the convex side. Convex side faces away from the caliper.

 

[spokewrench]

Yeesh. How do you bend a brake caliper bolt?

I believe I read that Shimano started using a concave/convex combination for rim calipers. Those bolts look more likely to bend.

I think with disc calipers, the alignment problem comes from using an adaptor to raise a caliper for a larger disc. In the photo, the adaptor raised one end 10 mm and the other 15mm. The surface of the caliper may be 3.8 degrees out from the heads of the bolts.

 

[m@Robertson]

I think with disc calipers, the alignment problem comes from using an adaptor to raise a caliper for a larger disc. In the photo, the adaptor raised one end 10 mm and the other 15mm. The surface of the caliper may be 3.8 degrees out from the heads of the bolts.

A properly matched adapter should account for any realignment thanks to change in diameter (making sure the pads contact the rotor surface fully, still), BUT all adapters are not the 'good' kind. I've had that experience enough that, several years ago, after I moved to and standardized on Magura brakes, I also standardized on Magura adapters. Back when I was using SRAM, Tektro and AVID brakes (the pictured BB7 was actually the last not-Magura caliper I bought), I was mixing and matching adapters, buying whatever size gave me a good price or availability of the moment, and as a result I had all sorts of weird-ass fitments thanks to the misalignments that come from doing that. Was not unusual for me to have to stack a few washers in between adapter and caliper, with a longer bolt needed to make that work right... or to put up with a caliper whose pads didn't quite line up with the rotor inside and I'd end up with a percentage of rotor with zero pad contact.

When I started matching brands for both the caliper, adapter and rotor, all that went away. Fitment works perfectly every time, and on the first try. The one exception has been my use of the Tektro 2.3mm rotors with the Magura parts as that just happens to be a perfect fit, rotor face to caliper.

From that picture, you've got good alignment to the rotor since the entire rotor face looks scored, and it doesn't extend down into the rotor spokes.