Brakes pulsating, out of true wheel or warped rotor?

[Weeksz]

Hi all,

Is it possible that an out of true spoke wheel could cause pulsating while braking? I only notice the brake pulsations significantly at slower speeds, higher speeds (30+) it is not really that noticeable. The rolling (not under braking), however, seems smooth with no wobble in the handlebars or bike in general. I;m looking into getting a new set of rotors to try and solve the problem but I want to explore other possible sources of the pulsating. The spoke wheel is off a 77, I'm on a 81. Spoke wheel hasn't been trued since I've owned it.

Thanks

 

[Agemax]

clamp a DTI on the fork leg and measure any run out on the rim or the rotors.

 

[8ball]

Raise the front wheel off the ground, so it can spin. Hold a screwdriver or rod perpendicular against the fork so the end of the screwdriver just touches the rotor. Spin the wheel, while holding the screwdriver in place. You will be able to see any warpage of the rotor where the screwdriver touches the rotor. The more accurate method would be to set up a dial indicator, but I am assuming, by the nature of your question, you don't have one.

 

[eil]

More likely a warped rotor. I've heard worn or damaged brake pads can cause the same pulsating feel as well.

 

[dorkburger]

My rotors were slightly bent while my bike was being towed....bit of a story there...Anyway, I didnt notice it at speed, but as you are experiencing, it could be plainly felt when coming to a slow speed stop, such as slowly braking to a stop at an intersection.

 

[Weeksz]

Well yesterday I completed a front brake service on the bike to inspect and see if I could reduce or remove the pulsations. Pads looked good still, no damage or uneven wear, greased all the slides and slapped them back together. I used the method that 8ball recommended and it turns out my rotors aren't warped at all. I taped a small flat head screwdriver to my fork so it just nearly touched, spun my front wheel and sure enough no touchie on either side. Not even the slightest wobble I could see.

I then began to look at my wheel and I think I found my problem, its slightly off true and fails the same screwdriver test. So this must be the reason for the pulsations, right? If so, does anyone attmept to true themselves? I have done it on my mountain bike before with success but it wasn't perfect, I also realize its a bit different.

Thoughts?

 

[eil]

If your wheel has spokes, yes it can be trued. I would imagine that the procedure is the same as for bicycle wheels but don't quote me on that.