The pin in the Brembo

It’s way past time for the rear brake pads on the Guzzi to be replaced. I’ve been putting it off for too long think­ing that I don’t real­ly use my rear brake that much any­way. Of course, that’s ter­ri­ble rea­son­ing for at least three reasons.

First, it’s ter­ri­ble rea­son­ing because I ought to use my rear brake. The front brake is always going to do more work, but why not let the rear brake do its part too? Novice rid­ers fre­quent­ly rely too heav­i­ly on their rear brake, which can lead to nasty high-side crash­es. Inter­me­di­ate rid­ers who like to pre­tend that they are bet­ter than they real­ly are fre­quent­ly show off how lit­tle the novices know by going to the oth­er extreme: nev­er using the rear brake at all. Well, OK. So the front brake has (depend­ing on who you ask) between 75% and 85% of a motor­cy­cle’s brak­ing pow­er. Well, that means that using both brakes yields between 18% and 33% more brak­ing pow­er. That’s noth­ing to sneeze at.

The sec­ond rea­son it’s ter­ri­ble rea­son­ing is much the same as the first. Even if I don’t rou­tine­ly use my rear brake, I may encounter emer­gency sit­u­a­tions where that extra brak­ing pow­er is not just nice, but nec­es­sary. Even the guys sit­ting in Star­bucks drink­ing lat­tés while wear­ing full leathers know that there are times when grab­bing some rear brake is nec­es­sary. If I need it, I want the brakes to be there.

Third and per­haps most impor­tant­ly, it does­n’t mat­ter if I’m not using my rear brake. The brake calipers have small springs that hold the brake pads against the brake rotor all the time. The springs hold the pads only light­ly against the rotors but they are still always touch­ing the rotors. This pre­vents the brakes from need­ing greater trav­el when the pads are worn down. This is a prob­lem that’s easy to see on a bicy­cle: adjust your brakes so that the brake shoes have just a mil­lime­ter clear­ance on each side, then ride for a few hun­dred miles. If you’ve been using your brakes the brake shoes will be worn down a cou­ple mil­lime­ters each. Instead of 1mm clear­ance, your brake shoes will now be 3mm away from your rims and you’ll have to pull hard­er on your brake levers just to get the same brak­ing pow­er. It’s not a huge prob­lem, but motor­cy­cle (and I assume auto­mo­bile) brakes avoid it by mak­ing sure the brake pads always light­ly graze the rotor.

That means that once the brake pads are worn sim­ply avoid­ing the use of the rear brake does­n’t help. The pads will con­tin­ue to wear until there’s no brake pad mate­r­i­al any more and you have met­al on met­al, which will quick­ly dam­age the brake rotor.

So it is high time I learned to replace my brake pads. The rear brakes are the best place to start any­way, because on my bike I have two sets of pads on the front and only one set on the rear.

The instruc­tions for replac­ing the rear brake pads in the Guzzi shop man­u­al (yes, I keep the shop man­u­al on my iPad) are fair­ly clear. One pops off a cov­er shield, extracts a pin by hit­ting it with a push rod and a ham­mer, then removes a reten­tion spring, slides the old pads out, the new ones in, and puts it all back togeth­er. Piece of cake, except when it isn’t.

The trou­ble came when the pin would not budge. Heed­ing my father’s advice (don’t force it, get a big­ger ham­mer) I set down the rub­ber mal­let and screw­driv­er I’d been using and retrieved a five pound ham­mer with a flat-head tapered punch. The pin with­stood some might­i­er blows with­out budg­ing so it was time for me to uti­lize the uni­ver­sal tool for find­ing solu­tions to prob­lems oth­er peo­ple have prob­a­bly encoun­tered: Google.

Unfor­tu­nate­ly, though a Google search led me to sev­er­al accounts of peo­ple with exact­ly the same prob­lem with Brem­bo brakes, most of the forum respons­es were the same: reit­er­at­ing the stan­dard instruc­tions. The unspo­ken mes­sage was clear: though you’re doing what we say you should do, you must be doing it wrong, because it always works this way. Some of the solu­tions offered involved dremel tools, blow­torch­es, and replac­ing the entire brake sys­tem. The one good piece of advice was to hit the pin with a very small amount of a pen­e­trat­ing oil and go at it again in a few min­utes. While this did not free the pin to pop through under the force of the ham­mer, I did find that I could rotate the pin eas­i­ly with a pair of pliers.

I had tried hit­ting the pin from the right side of the bike rather than the left, but the major­i­ty of the time I was work­ing from the left. From the left the brake is more eas­i­ly acces­si­ble, but also the pho­to in the shop man­u­al shows the brake from the left side of the bike. After find­ing that I could rotate the pin with pli­ers, I tried pulling on it. To my sur­prise, it came out eas­i­ly about 2mm (see pic­ture at the top of this post) though I could not pull it any fur­ther than that. This proved that the pin had not seized but fur­ther it was obvi­ous that the pin had a head on it that would pre­vent it from going far­ther through the hole it sat in.

When hit from the right side (per­haps for the first time since apply­ing the pen­e­trat­ing oil) the pin slid eas­i­ly out the left side after just a few taps, just like it was sup­posed to.

Some­one, whether the last own­er or the shop I usu­al­ly take the bike to, had put the pin in from the wrong side1. On reflec­tion it seems like an easy mis­take to make. After push­ing the pin through from the left, one might eas­i­ly not think to cir­cle to the oth­er side of the motor­cy­cle to push the pin back in from the right when done. The pin-hole would be right there, an obvi­ous place to return the pin to what seems like its orig­i­nal position.

More impor­tant is to get this infor­ma­tion out where future searchers with the same prob­lem can find the solu­tion, espe­cial­ly because most of the forums that have threads about «stuck Brem­bo pin» are auto­mo­bile forums. The design of the brakes them­selves may be sim­i­lar, but on an auto­mo­bile it is not any­where near as con­ve­nient to sim­ply walk around to the oth­er side to try and tap the pin out from the oth­er side. I imag­ine the temp­ta­tion to replace the pin from the side one is look­ing at would be greater as well, and for the same reason.

Yes, get the pen­e­trat­ing oil (but use it very spar­ing­ly — you don’t want oily brakes!) but before you fire up that blow­torch or start to dremel the pin out, try tap­ping the pin from the oth­er side to see if it was put in from the out­side. And a reminder: when you are done replac­ing your brake pads, put the pin back from the side oppo­site from the side fac­ing you. It’s going to be a lit­tle awk­ward, but much eas­i­er than try­ing to ham­mer the pin in a direc­tion that it won’t go next time you have to replace the brake pads.

  1. Whether there is such a thing as a wrong side in this case seems some­what sub­jec­tive. I’m call­ing hav­ing the head of the pin on the left side of the motor­cy­cle «wrong» only because it is oppo­site of what is expect­ed after read­ing and look­ing at the pho­tographs in the shop man­u­al. The pin will do its job equal­ly well insert­ed from either side. 

3 Replies to “The pin in the Brembo”

  1. Springs?????

    Are there real­ly springs press­ing the pads against the disks in Brem­bo brakes? I have nev­er seen a disk brake sys­tem that used any­thing like that. Usu­al­ly the pads just rest against the rotors unless some­thing push­es them away. Sub­arus used to have pis­tons that screwed them­selves in as they were used, but that is the only case I have ever seen where the pis­tons weren’t free to retract under pressure.


    1. Maybe not springs

      …but some­thing is keep­ing ten­sion on the pads. Once I got the pads out of the calipers, the pis­tons closed down to where I could­n’t fit a busi­ness card between the bare pis­ton and the rotor, nev­er mind fit the new pads in. Once I removed the calipers entire­ly I was able to push the pis­tons back in using a flat piece of met­al and push­ing with both thumbs. It was a lit­tle tricky (sort of a sit­u­a­tion that requires three hands but in the space I could fit two fin­gers) but with some patience I did even­tu­al­ly get the new pads fitted.

      It’s nice to know that I can do this myself. The first time may have tak­en a few days, but the sec­ond time will take an hour or so. I’m very glad my first attempt was on the rear brake. The front brakes may be a bit eas­i­er to get to, but there are two of them and each one is a four-pis­ton brake instead of a two-pis­ton mod­el like my rear brake. Now that I’ve done the rear brake the added com­plex­i­ty of the front brakes won’t be a big deal. But if I’d tried the front brakes first that would have been a lot more frustration. 

  2. Hydraulics

    Every disc brake I have seen sim­ply relied on the hydraulics to keep the pads from push­ing back. If they closed up by them­selves when you removed the pads, they must be dif­fer­ent from any­thing I have seen. Unless, of course, you hit the brake ped­al by mis­take while the pads were out. Or per­haps you have a boost­er sys­tem that retains a lit­tle hydraulic pres­sure. (I have nev­er seen one like that, but it cer­tain­ly is pos­si­ble.) The rea­son that the pads are hard to retract is because the design of the hydraulic sys­tem gives you mechan­i­cal advan­tage when apply­ing the brakes, and that means mechan­i­cal DIS­ad­van­tage when push­ing flu­id the oth­er direction.

    It is always very sat­is­fy­ing to me to fix things. It isn’t just about the mon­ey, but more about under­stand­ing how things work. Of course, you get to save a bunch of mon­ey, too.


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