Replaced rear rotor and pads - Weak brakes & hot rotor | GTAMotorcycle.com

Replaced rear rotor and pads - Weak brakes & hot rotor

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Krime

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Over the weekend I finally got around to replacing my rear worn out rotor and pads on my K4 GSXR. Brand new OEM Suzuki rotor with EBC pads.

I cleaned the calliper pistons, removed some of the brake fluid with a syringe from the reservoir before compressing the pistons and installing the new pads. I re-mounted the wheel with the new rotor installed and hooked everything up... pumped the rear brake until the pads made contact with the rotor. I put the brake fluid that was left in the syringe back in the reservoir, but the level was quite a bit lower than the full mark it was at before due to some spillage from the reservoir. The fluid now sits above the low mark, somewhere between the low and mid mark.

I took the bike out for a test ride. The braking power was significantly reduced. I don't mind it as it will be harder to lock up the rear, but was surprised by it considering the new rotor and pads. After 10 min of riding I pulled to the side of the road and felt the rear rotor and it was hot as hell. Is this normal? Concerned it was slightly dragging I rode another 5 min without using the rear and pulled to the side of the road and it had cooled down a lot. Interestingly, the original front rotors were barely even warm and they were doing all the braking.

When I got home I had a look at the rear rotor and the inside edge (about a quarter inch thick) has a lighter colour to it . The rest of the rotor from that point to the outer edge was darker in colour where the pad met the rotor. I was concerned the pad wasn't making full contact with the rotor but when I took a pic with the flash on my phone (which I can upload later), it did look like there were some grooves from the pad meeting the rotor on the lighter coloured portion of the rotor as well.

Any ideas? A bit concerned the excessive heat will cause the rotor to warp. Regarding the hot rotor and odd discolouration, I'm thinking the pad may not be evenly distributing its contact with the rotors maybe? Could the lower brake fluid level have anything to do with the weak braking?

Thanks.
 
I can't speak to the hot rotor but low fluid could lead to air in the brake lines which would cause weak braking. Buy some fluid, flush the lines and that will bleed them at the same time.

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If you have ensured that the brake pads are installed correctly and not seized or hanging up on anything.

Sounds like the brakes may just need to be bedded-in. Basically, for the brakes to work optimally there needs to be material transfer from the brake pads to the rotors. Until that happens, the brakes barely work. If you ever replace front and rear pads and rotors on a vehicle, you're in for a surprise on the first drive/ride.

I would suggest just riding the bike, with increased emphasis on using the rear brake and see what happens, maybe drag the brake in a straight line as well.
 
Did you clean the guide rods where the pad ride on? You might need to do clean your brake piston
 
Sticky piston in the caliper. You don't mention it, did you bleed the rear brakes? It might help (and you should do it with new pads anyway). You can try working the pistons just by pumping the brakes a lot (use some force, bike does not have to be moving). If none of that does anything, I would take the caliper apart.
 
First things first, put the rear on a stand, apply and release the rear brake, then spin the rear wheel and make sure it's not dragging.
 
1. New Pad and Rotor - its going need to be bedded in so it works as well. Until they 'bed' in, they will feel like they won't have much 'bite'
2. Post pictures of the rotor and the colouring you were describing
3. Sounds like you have pads they are dragging, or caliper isssue. Since the rotor is hot.
 
Thanks for the comments.

Here's the photos of the discolouration on the inner portion of the rotor as discussed (taken without and with flash):

i-x4xjsh9.jpg

i-sVsx4Dw.jpg


I'll be taking the bike out tomorrow for a ride to work and will report back with any updates. It's good to hear that the weak stopping power is normal. Hopefully the hot rotors aren't a big issue. I did a test after the rotors and pads were installed by rotating the wheel on the rear stand, and it did flow freely - just the normal dragging sound of the weak contact between the pads and rotors, but nothing that felt as though it was stopping the wheel from spinning freely.
 
did you thoroughly clean the rotor with BRAKE CLEANER ? it sounds like there may have been some contaminates on your rotor. Preservative oil on the rotor, or perhaps some brake fluid smears on the rotor from dirty fingers (you do mention a fluid spill). it doesn't take much more than traces of oil/fluid to mess up the brake pads. If this is what happened you may be able to run the pads over rough sandpaper resting on a perfectly flat surface, skimming off a layer of the brake pad material to remove contaminates.

you want everything perfectly clean. Oil / fluid contamination can cause the rotor to overheat as you keep applying more and longer brake pressure in the search for braking power.

your quote - "Concerned it was slightly dragging I rode another 5 min without using the rear and pulled to the side of the road and it had cooled down a lot." - this makes sense if the pads/rotor are contaminated with oil/fluid, more so than a sticky caliper / slide.
 
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^^I think bouboy is right on the money. That dark shade on your rotor sure does look like some sort of burnt fluid, probably as he said the preservative oil that comes on new rotors
 
boyoboy said:
did you thoroughly clean the rotor with BRAKE CLEANER ? it sounds like there may have been some contaminates on your rotor. Preservative oil on the rotor, or perhaps some brake fluid smears on the rotor from dirty fingers (you do mention a fluid spill). it doesn't take much more than traces of oil/fluid to mess up the brake pads. If this is what happened you may be able to run the pads over rough sandpaper resting on a perfectly flat surface, skimming off a layer of the brake pad material to remove contaminates.

you want everything perfectly clean. Oil / fluid contamination can cause the rotor to overheat as you keep applying more and longer brake pressure in the search for braking power.

your quote - "Concerned it was slightly dragging I rode another 5 min without using the rear and pulled to the side of the road and it had cooled down a lot." - this makes sense if the pads/rotor are contaminated with oil/fluid, more so than a sticky caliper / slide.
Click to expand...

Thanks for your thoughts. I rode into work this morning and noticed the rotor got hot right away after applying some rear brake going down the hill from my street (so in no time at all).

I didn't clean the rotor originally as it was in a plastic seal, but maybe there was some contaminants from the manufacturing process or from fluid spillage as you'd mentioned. There is a good chance I had some traces of brake fluid on my fingers when handling the rotor (when placing it on the wheel). Also, I used Simple Green to clean out the callipers before installing the new pads, but I'd imagine that shouldn't come in to play here.

What's the best way to clean this up? Can I apply brake cleaner to the discs while they're mounted to the bike or do I need to take out the wheel again?

For the brake pads, should I try to clean them as well or just focus on the rotors? If so, should I remove them and sand them down as suggested or is it safe to apply brake cleaner to the pads?

Trying to figure out the most efficient way to clean this up.
 
Break cleaner on the mounted disk is fine, but you might as well sand down the pads. No point in doing a half job.
 
Brake rotors will rust in no time - MFG's don't want product to rust on the shelve, so they will apply a preserving oil on the rotors to prevent this.
So they will need to be cleaned free of any oil or any other matter.

Brakes are suppose to get hot when used - the friction what is generating the heat.

Take it apart, clean and dry everything with brake clean. AND BED In the pads!!
 
Thanks guys.

Riceburner said:
Were the new disks cleaned with brake cleaner before mounting?
Click to expand...

No they weren't. Didn't realize I had to but makes sense in hindsight especially after what Frekeyguy's explained. I'll take your advice, clean the rotors with brake cleaner and sand down the pads. Any idea what grit sandpaper? I'm imagining the best way will be to lay the sandpaper on the floor and graze the pads back and forth over it keeping the pads as flat as possible in the process?

Also, is there any benefit to spraying brake cleaner on the pads as well? I tjust picked up the Candian Tire non-chloride brake cleaner but noticed some of the brake cleaners specifically said not to apply to brake pads. I get the idea of keeping it away from the callipers due to the rubber seals, etc. but thought it was onkay on the detached pads themselves.

Thinking of removing the pads to sand them down, and dropping the calliper and applying the brake cleaner to the disc with the wheels still mounted. Bad idea or okay? I'm imagining i'll need to cover up the painted rims to avoid contact with the brake cleaner if I go this route.
 
frekeyguy said:
Brake rotors will rust in no time - MFG's don't want product to rust on the shelve, so they will apply a preserving oil on the rotors to prevent this.
So they will need to be cleaned free of any oil or any other matter.

Brakes are suppose to get hot when used - the friction what is generating the heat.

Take it apart, clean and dry everything with brake clean. AND BED In the pads!!
Click to expand...

Thanks. When you say bed in the pads are you referring to sanding them down?

Thinking of cleaning the discs with Simple Green and water then applying the brake cleaner (while still mounted if possible).
 
beddng in pads is not sanding them......

have a read ...

https://ebcbrakes.com/articles/motorcycle-bed-in/


Bedding in new motorcycle pads and rotors

After 35 years as the worlds number one brand, EBC Brakes has accumulated massive experience on how to guide its customers to enjoy their brake products safely.
Bedding in new motorcycle pads and rotors is an extremely important process – please follow these guidelines:

Fitting New Disc Pads To Used Brake Discs/Rotors

First of all, there are two different types of brake pad on the world markets which are sintered copper alloy or organic types. The sintered types are of course much harder and take 3-5 times longer to bed in GEOMETRICALLY to any hollow areas or ridges on a worn brake rotor. Organic pads being slightly softer bed in more quickly but also suffer from what is known as “green fade”. Green fade is explained as a heat curing of the brake material which happens over the first heavy heat cycles.

To bed in sintered pads, drive the vehicle carefully allowing extra braking distance for the first 300 miles. Please be aware that brake performance during the bed in period may be significantly less than you have been accustomed to. What you are looking for is to see a 90%+ surface area contact between the pad and the disc or rotor before optimum braking will be achieved.

Once your pads are 90% surface area bedded after the 300-400 miles, on a safe road, use the brakes 10 times in succession stopping your motorcycle from 60mph to 20mph to get the brakes deliberately hot. This is particularly important with the organic versions (Kevlar® types, carbon based pad types and semi-metallic pad types). After this process, the pads should settle down and normal riding and brake performance can be safely achieved.

Fitting New Disc Pads With New Brake Discs/Rotors

Although the brake disc/rotor surface will be perfectly flat when using a new rotor, it is still extremely important to “condition” the brake discs and match them up to your pads by driving gently for 200-300 miles. After this period, perform the heat bedding of organic pads as above in blue text.

Always remember not to contaminate your brake pads with any fluids or greases (even brake fluid) during the install process.

If you experience any vibration or serious loss of brake during this process, contact a professional motorcycle dealer for assistance.

Bedding In New Brakes for Trackday or Race Use

If you are using your motorcycle for a trackday or race event, bedding in the new pads is even more important. 99% of racers use sintered pads for trackday and race events because they do not require chemical bedding as in blue above, but these pads still need to be matched to the rotor and therefore a bedding in process of 2-3 laps gentle brake use gradually increasing brake pressure and load after that has been completed is advisable.

EBC Brakes make some excellent trackday pads such as their EPFA range or the full race GPFAX range.
Click to expand...
 
Taking the pads off and running them on some medium grit sandpaper on a flat surface should be fine. Spraying brake cleaner with the disk mounted is fine. I've never had any issue with it and painted rims.
 
Riceburner said:
Taking the pads off and running them on some medium grit sandpaper on a flat surface should be fine. Spraying brake cleaner with the disk mounted is fine. I've never had any issue with it and painted rims.
Click to expand...

Good to know, thanks.
 
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