Warped rotor replacement

I have a pulsing in my front brakes and after taking to the dealership service dept I am told it is the rt side rotor that is warped. They suggest replacing both rotors and pads to the tune of about $1k. I am not the most mechanically inclined guy in the world but am learning. This is a project I'd like to take on. Any ideas as to what aftermarket rotors I should look at? I already have pads. For some background this is an '03 ST1100P, non-abs. The 'pulsing' was there when purchased it a year ago and has not worsened but is pretty annoying. Guessing my braking would also improve with the repair. Any insight would be appreciated, especially with which rotors would be a good replacement.

There is no reason why you would need to replace both rotors if only one is warped. A good friend had one of his rotors bent at the dealership when they were changing the front tire and he ended up getting a new rotor out of it. I believe he had more than 50k miles on his ST1100 when this happened. It was always interesting to look at his front wheel after that because you could see a small difference in the thickness between the two rotors. Didn't make any difference in his braking capability.

Some might disagree on this point but if the pads are relatively new on that side I wouldn't replace them right away either. Try replacing just the rotor and see how the brakes feel. You can always change the pads later if you don't like the old ones...

Its better to replace the discs as a pair, and new pads, this way the braking will be balanced. If you use old pads, it can introduce uneven wear patterns in the new discs.

In the end its up to you what you do. I will be replacing both front discs on my 1100P soon, and will be fitting new pads as well.

I would look for a good used rotor and replace the one warped rotor and move on. Good luck.

Avtrician said:

Its better to replace the discs as a pair, and new pads, this way the braking will be balanced. If you use old pads, it can introduce uneven wear patterns in the new discs.

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But: it actually depends on the wear of the (remaining) old rotor...
If the difference is neglect-able, and the pads are nearly new, you might get away by just replacing the damaged rotor with an OEM part (and bevel the edges of the pads before installation)

If you get after-market parts I'd strongly suggest replacing both rotors due to friction coefficient...

In any way would I strongly suggest to get a good toque-wrench for attaching the rotors properly to the wheel.
And IIRC a medium thread-lock for the bolts.

Replace only the defective rotor unless the other is close to minimum limits. There is no reason to replace the good one- it will not affect braking.
If the pads still have a lot of material left there is no reason to replace them. Rub them in a figure 8 pattern against some sand paper on a flat surface to even them out so that you start out with straight pads against a straight rotor.
Just in case it has not been checked make sure that your caliper is moving freely on the bracket slider pins. If it is sticking badly enough any movement in the rotor is transmitted directly to the piston because the caliper is not moving with the rotor. This is felt as a pulsation in the brake lever. If this is the case your rotor may still be warped (most usually are to some degree) but may not be bad enough to require replacement unless it is beyond limits. It is easy to check and worth a look.

JRob said:

I am not the most mechanically inclined guy in the world but am learning.

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First step to this is to verify that the dealer or whomever was correct in the diagnoses. Check to see if the rotor is really warped. Is the warp visible where no work is needed to see it? This can be done without special tools. With the bike on the center stand, put a floor jack under the oil pan and lift the front of the bike up enough to spin the wheel freely. Spin the wheel can you see the warp? If yes replace what is needed. If no then further diagnostics is needed. Again no special tools because you just want to determine if it is warped not how much. Use a pencil or marker and hold it against the lower fork tube in a fixed position with the tip touching the rotor near the outside edge where there are no holes. Spin the wheel and see if the marker/pencil leaves a complete or broke line on the rotor. Slight pressure is used on the surface of the rotor as sometimes the warp is slight and you don't want so much pressure that you cannot see the broken line. If it is found that the rotor is warped then special tools would be required to determine how much warp there is. (such as a dial indicator). Although the same process would be used but the dial indicator would need to be clamped to the lower fork tube.

All of this can be done without removing the wheel from the bike.

Others here can help answer the question about all what should be replaced.

I am not sure about this but if they are the floating disc type make sure the buttons that allow the disc to move are not full of dirt and crud holding them in an offset or warped position . They should have a little movement and be able to spin .

Also worth a shot is to loosen the bolts that hold the rotor on, then re-torque them to spec . (Gradually tighten each bolt and sneak up on the spec torque value..)

gmtech94 said:

I am not sure about this but if they are the floating disc type

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I believe the 1100 has fixed rotors and the 1300 has the floating type.

Same thing happened to me, right rotor warped causing pulsation on braking, especially just before coming to a complete stop. After some back and forth Honda, they eventually replaced it under warranty. The left disk was fine. Unless, as others have said, you are at the service limit for thickness, I would leave the left one alone. I would change both if you decide to go aftermarket with EBC or Galfer otherwise.

Agree one should verify if it is indeed warped or has dirt in the floating rivets.
A little experience of mine if you're on a budget... My rotors were worn too thin, and had to be replaced. I wanted to go with the nicer-to-me wave rotors EBC has, but with some skepticism, I decided to try some made in China stainless rotors on the FJR. I did as best I could to determine the vendor was a good one, material used, etc... I bought a pair for $170 and it took a couple of weeks for them to arrive. They look good and have slots to help them vent well. They seemed thicker, although to be honest I did not measure them at the time. Been on there two years, and I'd say they stop a bit better because of the venting, no abnormal wear or scoring, pads are not wearing abnormally. I'm quite happy with them.
There are some used ones on ebay, but best to ask if they have measured thickness with a micrometer. You could just replace one in that case.

Thanks all for the insight. I'll do some double checking of the rotor and then start a search for a proper replacement if needed.