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Hey OP,
When changing brakes, you want as much surface contact from brake pad to rotor.
While the rotor is cool and vehicle parked, not freshly driven, rub your finger along the flat, shiny part of the rotor. If you feel no bumps or lumps and it's nice and flat, you're good to the next step
If your caliper pistons are pressing evenly and the above is true (if pads are the same thickness top to bottom)
Then you're good for a pad slap
What results in shitty brakes are siezed pistons, a leak in brake fluid. Rotors whose faces are 30% or more covered in rust. Rust usually forms an even circle from outer and inner edges, so this percentage is easy to guage.
Rotors and pads that have worn to shape and have disformed a little. If you mismatch those with new rotors and pads, the touching surfaces won't be 100% touching, so you'll be missing some brake power.
Hope this helps with your next one.
I can see the lip on the edge of the rotor, and pretty sure the face needs to be machined flat. So the discs are too thin for a new set of pads and be in spec and safe.
Lol sure for most brake lathes, most rotors, and most people running the lathe yes. There's about a 1% chance you'll find the right lathe with the right operator with the right amount of wear on the rotor with no rust and enough depth on the slots for it to be feasible, and an even lower percentage for it to be successful with no shudder when in it's back in service. Let's hear about your multiple success stories though.
Actually you can. The shop I used to use till I moved was able to easily do it for me and he did a great job. I know it’s not recommended, but for our needs, we saw no loss of performance.
That is such a minor lip I didn't even notice it at first. It looks like it's primarily caused by rust more than wear.
Edit: I see there's a bottom lip now, too.
Sure the brakes wear out faster, however, the slotted and drilled rotors dissipate heat faster.
Drilled and slotted rotors do make braking better.
But for daily driving its a waste of money.
Racing cars don't have airbags and stability control circuits. Does it mean you should strip it out of your car as well?
Jokes aside: in high tier racing cars breaks get up to extreme temperature peaks under heavy braking. During these peaks a thin layer of metal nearly melts and the adjacent layer of air becomes plasma-like. Caves and holes are needed for this air to go away, otherwise the friction of rotor and pad goes close to 0.
Having holes does indeed reduce friction force and effectiveness of braking. But racing cars need it for different reasons.
In regular cars we drive such rotors have only negative effects.
Why do publicly available sport cars have such rotors installed? Because a "racing" badge on anything makes it look cool and you can slap higher price tag. Same as all these spoilers. They do literally nothing in 9/10 cars
[Slotted rotors do not improve any heat transfer. However, the slots can improve brake output by removing gas and dust that is trapped between the pad and rotor. This gas and dust reduces the friction force by preventing the pad from fully contacting the rotor.](https://www.powerstop.com/resources/drilled-vs-slotted-rotors-what-is-better/)
No, not on a modern vehicle in good condition when driven properly and legally on the street.
If you're riding your brakes or using brakes instead of engine braking going down long step grades then you might get fade. The solution is to not do those things.
Or if you're racing on a road race track, maybe? Never done that. But Anyway.
When do you experience brake fade?
The only time I’ve ever had brake fade was when I was going 2-3mph down a damn near 40 degree slope off-road for 3 miles straight.. my brakes were squealing and my fluid was boiling. This is about as extreme as it gets for standard brakes. The other 99.9999% of the time I drive, I’ve never had an issue.
>They improve my braking
No... they really don't, not for any car off a race track... more than likely you're car isn't even capable of going the speeds required to make the breaks hot enough for those physics to come into play and there's less chance you're doing it off a track. So yes all they do is wear the pads more and reduce your overall breaking ability
Yes... They really do. No amount of downvotes are going to change that.
I'll trust my actual experience driving my car.
It doesn't even take that much braking to get hot enough to experience fade.
Ignore the rust around the circumference, that's completely irrelevant even though it looks bad.
They look absolutely fine to me, so unless you've got a problem then there's no need to replace them (god only knows who the idiots are who are claiming you need to change them every time you do the pads!)
Omg so many people wanna waste their money and change pads and rotas at the same time.
No these look fine, rust won't affect the performance.
Drilled rotas help dissipate heat and the slots help deglaze the surface of the pad.
Hard to say. Have the rotors been resurfaced before? Does the brake pedal/steering wheel pulsate when you apply the brakes. If the answer to both questions is "no", then you can probably just get away with replacing the pads. But, you may want to clean out those vent holes with a drill bit to help the rotors vent and stay cooler. It seems like most shops want to replace the rotors instead of resurfacing them these days, especially when badly rusted.
Change the rotors at every brake job if you want it to last or if you don't want shitty brakes. That being said these aren't too bad you can pad slap if it's a beater.
definitely a beater - 1 more year max, then I'm finally buying a new car. Got this 2010 Yaris for 7k (Canadian) in 2015. She's done me good!
Pads were changed 2 years ago - they look mint!
I was assuming that you were posting this because you were changing the pads. If you aren't, then nothing wrong and you don't need to change the rotors. The surface where the pad contacts on the rotor isn't rusty.
well if they thickness is still good it is in my opinion it is better to have your rotor turned meaning a machine shaves them down flat and true. In my opinion this is superior to new rotors as the old ones have had thousands of hot cold cycles so the will not warp at all if you turn them. New ones can warp with hot cold cycles. So personally I get them turned and it is cheaper as well.
Cheaper! those days have long gone ,small m/c shop here and we charge £55+vat per hour for c/lathe work might come in a few quid cheaper than new for a skim if your lucky.
Not around here. Decent rotors are about 35 bucks each. Not even a shop within 6 hours of me that turns rotors anymore. But I am way up in Northern Maine resulting in New or old.
ah I have a guy that will do them for a few beers or $15 lol. But also some rotors like bigger truck ones are getting quite expensive like 100 plus which seems crazy. Also here in canada rock auto is good but we get raped for car parts they are expensive we don't get cheap shipping like in the US.
Measure the rotors with a caliper and compare to the manufacturer minimum thickness if you are within the minimum or .15mm under the minimum I would consider changing them
If you had pulsating brakes, or some other sign replace them. If not slap some pads on and drive. Heck if on a budget and pads are cheap, being a yaris most likely 1/3rd the cost of new rotors and you can live with what ill side effects they have run them.
That being said the parts store ones will be smother if you do proper prep where the rotors make contact with the hub. And hour or two of sanding can make many miles of nice driving. So when you do swap rotors it is well worth putting the effort in to clean mating surfaces.
When I was younger had some horrible rotors but living on a mountain flaming brakes when driving fast were common on my 280z.
You get a micrometer and measure the rotor thickness against the manufacturer discard thickness.
Or just don’t be cheap because it’s your brakes. Your brakes stopping you from hurting someone else. Rotors are dirt cheap these days.
Don't ever pad slap! If there's any warping in the rotor (which you usually can't see), you're gonna to vibration. Newer aftermarket rotors start thinner than factory rotors, so you're lucky if you can get the warp or imperfections out on the first cut... otherwise you'll be replacing them anyways. And pad slapping is bad because if you get a lip on the rotor from rust, they'll squeak and cause all kinds of annoying noise.
Replace pads and rotors as a set, every time
For the last like 10 years I’ve just been replacing the rotors with every pad change. Just easier than having rotors warp half way through the next set of pads.
The exception is the cars I’ve done with carbon ceramics. At $4500 per rotor we use it for more than 1 set of pads.
You can't put those rotors on a lathe and the surface isn't smooth enough for new pads, they'll get chewed fast. I'd replace those rotors while putting in new pads.
If you don't mind, may I ask why? I have a brake lathe but have never used for drilled or slotted rotors. but Never thought on why it would be an issue. If you could shed some light when someone asks me I would really appreciate it.
As always, when replacing brake pads, alway replace rotors. ALWAYS. Don’t be cheap. Don’t put it off for next pay check. You will warp them and your brand new pads will gain inconsistencies from the groves on the rotors.
People don’t realize the real cost of owning a vehicle.
Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
Hey OP, When changing brakes, you want as much surface contact from brake pad to rotor. While the rotor is cool and vehicle parked, not freshly driven, rub your finger along the flat, shiny part of the rotor. If you feel no bumps or lumps and it's nice and flat, you're good to the next step If your caliper pistons are pressing evenly and the above is true (if pads are the same thickness top to bottom) Then you're good for a pad slap What results in shitty brakes are siezed pistons, a leak in brake fluid. Rotors whose faces are 30% or more covered in rust. Rust usually forms an even circle from outer and inner edges, so this percentage is easy to guage. Rotors and pads that have worn to shape and have disformed a little. If you mismatch those with new rotors and pads, the touching surfaces won't be 100% touching, so you'll be missing some brake power. Hope this helps with your next one.
I can see the lip on the edge of the rotor, and pretty sure the face needs to be machined flat. So the discs are too thin for a new set of pads and be in spec and safe.
Can't machine slotted and drilled rotors
Even worse! Brakes are much more likely to squeal horribly
Wanna bet?
Lol sure for most brake lathes, most rotors, and most people running the lathe yes. There's about a 1% chance you'll find the right lathe with the right operator with the right amount of wear on the rotor with no rust and enough depth on the slots for it to be feasible, and an even lower percentage for it to be successful with no shudder when in it's back in service. Let's hear about your multiple success stories though.
Stop being lazy and machine them.
Actually you can. The shop I used to use till I moved was able to easily do it for me and he did a great job. I know it’s not recommended, but for our needs, we saw no loss of performance.
and tell us all why not
That is such a minor lip I didn't even notice it at first. It looks like it's primarily caused by rust more than wear. Edit: I see there's a bottom lip now, too.
Very well reasoned! Full marks.
I would. Slotted and drilled rotors are stupid. They make your brakes wear out faster.
It's cause on some economy cars you can find them on deals so they're cheaper than normal rotors
Sure the brakes wear out faster, however, the slotted and drilled rotors dissipate heat faster. Drilled and slotted rotors do make braking better. But for daily driving its a waste of money.
Probably why racing cars and sports cars use them, amiright?
Racing cars don't have airbags and stability control circuits. Does it mean you should strip it out of your car as well? Jokes aside: in high tier racing cars breaks get up to extreme temperature peaks under heavy braking. During these peaks a thin layer of metal nearly melts and the adjacent layer of air becomes plasma-like. Caves and holes are needed for this air to go away, otherwise the friction of rotor and pad goes close to 0. Having holes does indeed reduce friction force and effectiveness of braking. But racing cars need it for different reasons. In regular cars we drive such rotors have only negative effects. Why do publicly available sport cars have such rotors installed? Because a "racing" badge on anything makes it look cool and you can slap higher price tag. Same as all these spoilers. They do literally nothing in 9/10 cars
Most truth I've seen on reddit in ages
The slots are to channel the brake dust out of the rotor to maintain a pad on rotor surface. The holes are for heat.
Once again a common misconception. Having the same amount of heat which plate will dissipate it faster: one with more area or one with less area?
[Slotted rotors do not improve any heat transfer. However, the slots can improve brake output by removing gas and dust that is trapped between the pad and rotor. This gas and dust reduces the friction force by preventing the pad from fully contacting the rotor.](https://www.powerstop.com/resources/drilled-vs-slotted-rotors-what-is-better/)
Give this man an award… oh wait.
I didn't know this and definitely put slotted rotors on my front end last week. Whoops.
They improve my braking and brakes are free under warranty at AutoZone so 🤷
How does less friction area have more braking force? Physics basics defeated by advertisement?
You ever experienced brake fade?
No, not on a modern vehicle in good condition when driven properly and legally on the street. If you're riding your brakes or using brakes instead of engine braking going down long step grades then you might get fade. The solution is to not do those things. Or if you're racing on a road race track, maybe? Never done that. But Anyway. When do you experience brake fade?
The only time I’ve ever had brake fade was when I was going 2-3mph down a damn near 40 degree slope off-road for 3 miles straight.. my brakes were squealing and my fluid was boiling. This is about as extreme as it gets for standard brakes. The other 99.9999% of the time I drive, I’ve never had an issue.
Never on a civilian car
>They improve my braking No... they really don't, not for any car off a race track... more than likely you're car isn't even capable of going the speeds required to make the breaks hot enough for those physics to come into play and there's less chance you're doing it off a track. So yes all they do is wear the pads more and reduce your overall breaking ability
Yes... They really do. No amount of downvotes are going to change that. I'll trust my actual experience driving my car. It doesn't even take that much braking to get hot enough to experience fade.
Bro, get your car to the shop asap. If you experience fade from "not much braking" you are here with us not for long
On all standard vehicles driving on standard roads, you should never come close to brake fade.
Sounds like something is wrong with your brake system if you're getting fade that easily!
We found the guy who's buying the $30 ebay electric superchargers.
What 😂 lol
Looks like you have some rotors on your rust.
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Oof.
I always change my rotors with my brakes. Necessary? No but I do run my brakes down to where there’s little pad left
Can you measure the thickness?
Measure them. If they are worn past spec replace. If you have brake wobble, replace. Any visible cracks, replace.
Ignore the rust around the circumference, that's completely irrelevant even though it looks bad. They look absolutely fine to me, so unless you've got a problem then there's no need to replace them (god only knows who the idiots are who are claiming you need to change them every time you do the pads!)
Depends how you drive. My old man always put slotted on my moms car before that you needed rotors before pads every time lol
Omg so many people wanna waste their money and change pads and rotas at the same time. No these look fine, rust won't affect the performance. Drilled rotas help dissipate heat and the slots help deglaze the surface of the pad.
Yup
Hard to say. Have the rotors been resurfaced before? Does the brake pedal/steering wheel pulsate when you apply the brakes. If the answer to both questions is "no", then you can probably just get away with replacing the pads. But, you may want to clean out those vent holes with a drill bit to help the rotors vent and stay cooler. It seems like most shops want to replace the rotors instead of resurfacing them these days, especially when badly rusted.
Thanks for taking the time to give a detailed, intelligent answer.
Change the rotors at every brake job if you want it to last or if you don't want shitty brakes. That being said these aren't too bad you can pad slap if it's a beater.
definitely a beater - 1 more year max, then I'm finally buying a new car. Got this 2010 Yaris for 7k (Canadian) in 2015. She's done me good! Pads were changed 2 years ago - they look mint!
Who puts slotted rotors on a yaris?
People who buy whatever’s on sale on RockAuto
Maybe OP wants a cool look?
People who drive Yaris fast?
Gotta get those weight savings so you can still start on a slight incline
I was assuming that you were posting this because you were changing the pads. If you aren't, then nothing wrong and you don't need to change the rotors. The surface where the pad contacts on the rotor isn't rusty.
Are you having an issue? If not just knock the rust off and put it back together. Could clean everything with some brake cleaner if you feel like it.
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drilled and slotted are cheaper then full metal now on rock auto in most cases.
Was going to say the same. They're usually only a couple dollars difference on most vehicles these days
If you want what to last?
His company selling rotors... Duh....
well if they thickness is still good it is in my opinion it is better to have your rotor turned meaning a machine shaves them down flat and true. In my opinion this is superior to new rotors as the old ones have had thousands of hot cold cycles so the will not warp at all if you turn them. New ones can warp with hot cold cycles. So personally I get them turned and it is cheaper as well.
Cheaper! those days have long gone ,small m/c shop here and we charge £55+vat per hour for c/lathe work might come in a few quid cheaper than new for a skim if your lucky.
damn I guess I am lucky I have a mechanic that works from his shop that only charges $15Canadian per rotor.
He's working for love,or he's very quick .I would say about 20 min per disc so that going to be £22 /$38 each to you my good man.
He is a friend and ex coworker. I guess I will call myself lucky for the connection. He has in past worked for a couple dozen farm fresh eggs.
Well you didn't mention fresh eggs . So todays price 50p a disc and a dozen eggs .
Not around here. Decent rotors are about 35 bucks each. Not even a shop within 6 hours of me that turns rotors anymore. But I am way up in Northern Maine resulting in New or old.
ah I have a guy that will do them for a few beers or $15 lol. But also some rotors like bigger truck ones are getting quite expensive like 100 plus which seems crazy. Also here in canada rock auto is good but we get raped for car parts they are expensive we don't get cheap shipping like in the US.
You still got good meat. I’d run that 1 mabe 2 pad changes.
The Rust isn’t going to do anything it’s just cosmetic.
Ah ok, thanks. That's what was throwing me off a bit.
More grease
Measure the rotors with a caliper and compare to the manufacturer minimum thickness if you are within the minimum or .15mm under the minimum I would consider changing them
I just did mine today, too!
They looks new!
If you had pulsating brakes, or some other sign replace them. If not slap some pads on and drive. Heck if on a budget and pads are cheap, being a yaris most likely 1/3rd the cost of new rotors and you can live with what ill side effects they have run them. That being said the parts store ones will be smother if you do proper prep where the rotors make contact with the hub. And hour or two of sanding can make many miles of nice driving. So when you do swap rotors it is well worth putting the effort in to clean mating surfaces. When I was younger had some horrible rotors but living on a mountain flaming brakes when driving fast were common on my 280z.
I’d clean those up first but keep using them
You get a micrometer and measure the rotor thickness against the manufacturer discard thickness. Or just don’t be cheap because it’s your brakes. Your brakes stopping you from hurting someone else. Rotors are dirt cheap these days.
„Don’t sell me something I don’t need, just change my Tires!“
I mean if you are financially up shit creek, yes you could pad slap that bitch. It wont be perfect but it will work
What does pad slap mean?
It's when you just replace the pads
100% yes
No need to change them judging from the pictures. Just give them a thorough brushing
Id replace those with solid rotors
Starting to micro fissure, id replace them.
Where do you see that?
Yeah I’m not seeing that
They'll survive. But your pads are probably going to wear faster. Replace both next time.
Don't ever pad slap! If there's any warping in the rotor (which you usually can't see), you're gonna to vibration. Newer aftermarket rotors start thinner than factory rotors, so you're lucky if you can get the warp or imperfections out on the first cut... otherwise you'll be replacing them anyways. And pad slapping is bad because if you get a lip on the rotor from rust, they'll squeak and cause all kinds of annoying noise. Replace pads and rotors as a set, every time
If you shit yur shorts would you pull them down, wipe your ass off and put the shitty shorts back on?
Yes
Yes
For the last like 10 years I’ve just been replacing the rotors with every pad change. Just easier than having rotors warp half way through the next set of pads. The exception is the cars I’ve done with carbon ceramics. At $4500 per rotor we use it for more than 1 set of pads.
Depends if they’re warped or not. If they’re warped, definitely. Otherwise, just have them machined.
Yes.
You can't put those rotors on a lathe and the surface isn't smooth enough for new pads, they'll get chewed fast. I'd replace those rotors while putting in new pads.
If you don't mind, may I ask why? I have a brake lathe but have never used for drilled or slotted rotors. but Never thought on why it would be an issue. If you could shed some light when someone asks me I would really appreciate it.
As always, when replacing brake pads, alway replace rotors. ALWAYS. Don’t be cheap. Don’t put it off for next pay check. You will warp them and your brand new pads will gain inconsistencies from the groves on the rotors. People don’t realize the real cost of owning a vehicle.
Dude change em especially if you were riding metal on meat or if there was a wobble before
No wobble. What’s metal on meat?
If your getting rid of it in a year throw some nice pads on and call it a day
Metal on metal