Rear pads start to wear too fast

[ogri]

Hi, 

I replaced my rear pads when I fried them on the second motogymkhana session, I replaced and bleed fluid. Then I have been on 5 more motogymkhana sessions and replaced another set of rear pads. Year later I am not participating motogymkhana but I am still replacing rear tires and the rear pads as I did in motogymkhana time.

historically:

24000 miles fried disk, pads and fluid/replaced. (OEM yamaha pads)

26000 miles replaced rear pads (Galif or misspell, but something like this)

28000 miles replaced again (now EBC)

I rode today two miles around the city using only front brake and noticed rear disk is almost equal hot as the front one, why? Rear brake pads are dragging my disk? I am thinking about slider grease, do I have to stuff it full with hi-temp grease and wipe excess off after assembling or I have put just a little bit on a slider to prevent it from rust? My concern is about probably brake caliper is not retracting back by itself.

I will appreciate any links, explanations or ideas what it can be and how properly replace brake pads. I never had this problem on all my cars I serviced before.

Edited March 3, 2020 by ogri

[mossrider]

Just now, ogri said:

Hi, 

I replaced my rear pads when I fried them on the second motogymkhana session, I replaced and bleed fluid. Then I have been on 5 more motogymkhana sessions and replaced another set of rear pads. Year later I am not participating motogymkhana but I am still replacing rear tires and the rear pads as I did in motogymkhana time.

historically:

24000 miles fried disk, pads and fluid/replaced. (OEM yamaha pads)

26000 miles replaced rear pads (Galif or misspell, but something like this)

28000 miles replaced again (now EBC)

I rode today two miles around the city using only front brake and noticed rear disk is almost equal hot as the front one, why? Rear brake pads are dragging my disk? I am thinking about slider grease, do I have to stuff it full with hi-temp grease and wipe excess off after assembling or I have put just a little bit on a slider to prevent it from rust? My concern is about probably brake caliper is not retracting back by itself.

I will appreciate any links, explanations or ideas what it can be and how properly replace brake pads. I never had this problem on all my cars I serviced before.

First off, good for you for having fun and enjoying your toy. 

Second get a service manual if you don't already have one. 

You are plenty hard on back tires and especially brakes at your current rate. And that rear wheel/brake is a mess, get it cleaned up. There appears to be plenty of brake dust on your wheel. It's your neck. 

"This is what I do routinely and is in no way mechanical advice to the person of another for use on their brake system which is mission critical on your motorbike."

I would disassemble the brake in it's entirety, including from the backing plate on the rear. I then soak it (everything) in a near full strength solution of Simple Green from a spray bottle. While that's soaking I take the pins (I have already removed the pads, pins, spring clips etc)  and rub them down with steel wool to deburr and smooth them for like-new function. Using the brake lever I carefully move the brake piston(s) out a bit in their respective bores so I can clean around their circumference with a tooth brush and healthy wash of Simple Green. Anything else that slides, rubs or moves gets careful attention and cleaning as well. Then I finish scrubbing the calipers, stay arms, mounting points and bosses with more Simple Green. Rinse with fresh water, blow dry carefully (it's hard to find parts you've shot across the garage with 120psi) and reassemble with new pads in reverse order in accordance with the manual for your specific model. 

It's critical to keep the pistons and seals clean and newish since the seals resiliency/elasticity is the only thing 'pulling' the pads off the rotors in use. The little pins also get gunked up or rusty and should be kept clean, smooth or simply replaced when they're not.

The tiniest amount of high temp copper grease can be used on the slider bolts and pins but great care must be taken to keep it off the rotors and pads. Actually, if cleaned regularly you shouldn't need grease.

I clean mine after every race weekend and it only takes a few minutes if done regularly. On the street I'd do it at least every time I change pads or tires or once a season whichever comes first. 

My guess is that if you're not using your rear brake and it's still hot it's either dragging or you're resting your size 13 on the pedal or both. Maybe move the pedal down a wee bit after going through your rear caliper.

Have fun.

My $.02.

[cornerslider]

53 minutes ago, mossrider said:

First off, good for you for having fun and enjoying your toy. 

Second get a service manual if you don't already have one. 

You are plenty hard in back tires and especially brakes at your current rate. And that rear wheel/brake is a mess, get it cleaned up. There appears to be plenty of brake dust on your wheel. It's your neck. 

"This is what I do routinely and is in no way mechanical advice to the person of another for use on their brake system which is mission critical on your motorbike."

I would disassemble the brake in it's entirety, including from the backing plate on the rear. I then soak it (everything) in a near full strength solution of Simple Green from a spray bottle. While that's soaking I take the pins (I have already removed the pads, pins, spring clips etc)  and rub them down with steel wool to deburr and smooth them for like-new function. Using the brake lever I carefully move the brake piston(s) out a bit in their respective bores so I can clean around their circumference with a tooth brush and healthy wash of Simple Green. Anything else that slides, rubs or moves gets careful attention and cleaning as well. Then I finish scrubbing the calipers, stay arms, mounting points and bosses with more Simple Green. Rinse with fresh water, blow dry carefully (it's hard to find parts you've shot across the garage with 120psi) and reassemble with new pads in reverse order in accordance with the manual for your specific model. 

It's critical to keep the pistons and seals clean and newish since the seals resiliency/elasticity is the only thing 'pulling' the pads off the rotors in use. The little pins also get gunked up or rusty and should be kept clean, smooth or simply replaced when they're not.

The tiniest amount of high temp copper grease can be used on the slider bolts and pins but great care must be taken to keep it off the rotors and pads. Actually, if cleaned regularly you shouldn't need grease.

I clean mine after every race weekend and it only takes a few minutes if done regularly. On the street I'd do it at least every time I change pads or tires or once a season whichever comes first. 

My guess is that if you're not using your rear brake and it's still hot it's either dragging or you're resting your size 13 on the pedal or both. Maybe move the pedal down a wee bit after going through your rear caliper.

Have fun.

My $.02.

VERY sound advise @mossrider!!! I couldn't have said it better myself -

[fzar]

All of the above ^^ and. Have you checked  rear-wheel alignment? 

[ogri]

Thanks @mossrider for your advice.

I found full 564 pages service online manual 2014 Yamaha MT-07 Service which is perfectly fine for our North American version too.

I gave my bike a second full evening maintenance. Rear brakes were disassembled again and got cleaned/degreased completelly.

This that I found after one day riding:

The left pad had rainbow coloration already (after one day). Then I discovered (thanks to manual) for the first time that there is a small flat spring-plate-thing is hiding inside the caliper, behind the piston (page 211 in the mentioned service manual). The pads spring has two small lips and one was bent abnormally. I believe this was the issue, bent it back and checked pads sitting flush and evenly inside the caliper.

@fzar I counted small notches/grooves on the both swing arm's sides - looks equal.

 

 

 

Edited March 4, 2020 by ogri
syntax

[mossrider]

Excellent. The benefit of regular cleaning, close inspection and the manual, you'll find the tiniest anomaly. 

[fzar]

On 3/3/2020 at 1:46 PM, ogri said:

I rode today two miles around the city using only front brake and noticed rear disk is almost equal hot as the front one, why?

This is what made me feel something was amiss. I'm nowhere close to being an useful source of fixes. I too had a rear brake issue that was resolved by listening to @mossrider "check your work", "re-check it" again. If you have a rear -stand, put it on it and cold start should make the rear wheel go in a forward motion, or I found my issue by listening to the pads while turning the wheel and feeling a slight resistance.

Again don't take my word for it, you got the manual and fixed the problem. Well Done.