Just put on some DBA Slotted brake rotors on 80 series

[Red Rover]

Just though i would pass on some feedback. i wasn't all that haapy with the height of the pedal and the brake feel, i know a few guys have complained about brakes. I fiited them yesterday and took about 4 hours.

The difference is amazing. Now has a high hard pedal that pu;;s up sooo quick, and the pads haven.t even bedded in yet. Also used bendix 4wd pads. The rear rotors were down to 16mm and the front down to 28.5 which is 1.5mm under min tolerence.

In any case made a big difference.

Waiting for the new valve body to turn up now and fit this week to the auto. keep you posted, then low range transfer a few weeks later, then some longfields for insurance I think.

[Toli]

Mine came with them already on it. Compared to others I have driven it was a bit better. The guy I brought it off had tried everything except replace the entire brakes with that of a latter model Post 93.

[Gribble]

How does changing your rotors affect how high and hard your brake pedal is? Sounds more like you bled air out of it.

[Shadow]

How does changing your rotors affect how high and hard your brake pedal is? Sounds more like you bled air out of it.

have to agree with that. changing rotors will not change how high or how spongy your pedal is.

The pedal height is adjusted by taking slack out of the pushrod attached to the pedal which pushes into the master. Nothing to do with the rotors or calipers for that matter.

Also, the "hardness" of your pedal also has nothing to do with your rotor.

How does a slotted rotor help anyway? It should in theory be less effective since there is effectively less contact area between pad and rotor.

I can understand it helping the wet allowing water to get away quicker from between pad/rotor, but really dont see how it helps on a dry rotor.

do you by any chance have a hiclone?

[Red Rover]

Sorry, no hiclone...............the slots are supposed to keep the pads clean. I can tell you that mm makes a big difference on pedal travel. I can assure you that I did not blled the brakes. The only thing I did was change rotors and pads. In fact the new pads were on the old rotors for about a week and really only made a bit of a difference. The thinner the rotor and pads, the more the the brake has to travel because you get kick back or throw back on the pads as the rotor kicks the pads back, therefore when it does throw the pads back initially the piston has to travel more and therefore so does the pedal. You can prove this by the pressing the pedal down while driving with a quick release and depress again. The pedal will come up higer and harder on the second depress if you have worn pads and or rotors. If it has air in it you will know becuase when you pump up the pedal and hold it on the pedal will slowly go down, but not entirely to the floor, unless you have a big issue with air. The pedal was never spongy, the brake was like yeah the brakes were there but further down and not as much grip as i was looking for.

I don't think the slotted design makes an initial impact, the fact the rotors are far thicker has. The slotted is supposed to make a difference by keeping the pads clean and wearing them flat. Another guy in the club has them on his GQ on the rear and reckons the pads have worn even and lasted longer, which is strange, but maybe with the pads kept clean etc gives them more life. This in my experience with brakes and I may be wrong.

In any case I am really happy with the brakes now, but as time passes I'll post to keep updated on feedback.

[Shadow]

Sorry, no hiclone...............the slots are supposed to keep the pads clean. I can tell you that mm makes a big difference on pedal travel. I can assure you that I did not blled the brakes. The only thing I did was change rotors and pads. In fact the new pads were on the old rotors for about a week and really only made a bit of a difference. The thinner the rotor and pads, the more the the brake has to travel because you get kick back or throw back on the pads as the rotor kicks the pads back, therefore when it does throw the pads back initially the piston has to travel more and therefore so does the pedal. You can prove this by the pressing the pedal down while driving with a quick release and depress again. The pedal will come up higer and harder on the second depress if you have worn pads and or rotors. If it has air in it you will know becuase when you pump up the pedal and hold it on the pedal will slowly go down, but not entirely to the floor, unless you have a big issue with air. The pedal was never spongy, the brake was like yeah the brakes were there but further down and not as much grip as i was looking for.

I don't think the slotted design makes an initial impact, the fact the rotors are far thicker has. The slotted is supposed to make a difference by keeping the pads clean and wearing them flat. Another guy in the club has them on his GQ on the rear and reckons the pads have worn even and lasted longer, which is strange, but maybe with the pads kept clean etc gives them more life. This in my experience with brakes and I may be wrong.

In any case I am really happy with the brakes now, but as time passes I'll post to keep updated on feedback.

A disc brake caliper does not return, it only moves back due to disc runout so if your rotors are not warped the pad(pistons) only move away from the rotor a minute amount, thus on next application of the brake pedal you should only need to press the pedal a minor amount, enough to close the gap between pad and rotor.

The reason you get a harder pedal when you pump the pedal as you describe is because the pressure in the lines has not yet had a chance to bleed back through the master cylinder. Thus your next application of the pedal only requires a much smaller amount of fluid to be pushed down to the caliper resulting in a much higher pedal.

I can see that a slotted rotor will help keep your brake pads clean and may provide some gains there, but it certainly will not affect your pedal height. THis is soley a function of adjustments made to the pedal height adjuster, and slack in the pushrod atached to the pedal which pushes into the master cylinder.

[dow50r]

How does changing your rotors affect how high and hard your brake pedal is? Sounds more like you bled air out of it.

Hi a pair of warped rotors will give a low pedal....

[Red Rover]

True, i must admit I didn't bother to get to rotors machined as I know they would be undersized. Yes a warped rotor will cause a lower pedal so that may be been a contributing factor. But vibration etc will throw the pads back a little, but more run out will cause it to throw the pads back more, plus the calipers are on slides. But yes the amount is minimal, but like wheel alignments, it's a game of mm imo.

[Shadow]

True, i must admit I didn't bother to get to rotors machined as I know they would be undersized. Yes a warped rotor will cause a lower pedal so that may be been a contributing factor. But vibration etc will throw the pads back a little, but more run out will cause it to throw the pads back more, plus the calipers are on slides. But yes the amount is minimal, but like wheel alignments, it's a game of mm imo.

How much did you pay for slotted rotors, my rotors have done 400thousand k's and they machined up fine(first time theyve been machined).

They are now on the minimum tollerance but the braking has improved immensely since i got rotors machined (origonal toyota) new bendix 4wd pads, and rebuilt calipers. I also did all the wheel bearings etc while i was in there. It is probably a combination of all these things but the brakes are definantly 300% compared to what they were before i did the work.

[Red Rover]

On the back of the factory rotor on the front says min 30mm. Mine had done 230,000 assuming they are the original rotors. Rears were 16mm and the new ones were 18mm thick. MIne is also auto which probably will wear them out quicker perhaps as I need to ride the brake more (ok a lot), and the type of pad. A softer pad will not wear the rotor as much as a harder pad like a semi-metalic so i guess it depends. Yes machining will take the glaze of the rotors and take out the run out and improve braking. Therefore at min thickness yours should be at 30mm on the front. Mine were at 28mm so 2mm difference is quite a bit. I didn't realise they were so worn until I put a vernier on it and measured it. Yes %300 better, it feels like it after they are done. When you are going down a steep hill in an auto, in reverse in particular, you need all the help you can get.........

mmmm got a good price thru a mate but were $110 ea.


Ok i give up the real reason I put them on was to look a bit bling. Brake improvements were all done with smoke and mirrors

[Sixty]

Loose wheel bearings can also cause low pedal height. You wouldve 'tghtened' the brgs when you put everything back together

[carts]

Sounds good to me. I like having good brakes in my auto. Next job will be to change the rear rotors. I have changed the front already and it made a big difference. I am also running the Bendix 4wd pad.

Red Rover, how come you are changing your valve body in your auto? Are you trying to get a more responsive shift? 80 series auto's are lazy until you stick your boot into them....

[Red Rover]

Bearing were tight, in fact tightened up to the same spot as I didn't rebent the locking tab, but yes wheel bearing can cause it if the are loose enough

The valve body arrived today and putting it in this week. I am just bored and want to try something different with the auto, try a get a more positive shift out of it, whether it does or not i don't know until later in the week. If it's crap I'll say so but by all accounts should make a difference, want to for $800. I whole idea of the upgrades is to accomodate more power coming. I want to get everything else right first. Next is the head port & polish and see how much I can get out of a std motor before turbo upgrade. Ideally if I can get another 20hp or so I'd be real happy and not bother with a turbo, but if I do go down this path I know I 've got the brakes up to scratch, the auto upgraded to handle more power, done the computer for better tuning and then the head modded as well, so when or if the turbo goes on it's all done, so to speak. Having said all that the car goes pretty good after the retune and pulled 2nd gear along the beach on the high tide mark in high range so it was pretty soft.......drank the fuel though. some of my mates that drove it reckon it goes harder than their 80 series and I should be happy, but I guess you always want a bit more

[jimbo jones]

How does changing your rotors affect how high and hard your brake pedal is? Sounds more like you bled air out of it.

How does a slotted rotor help anyway? It should in theory be less effective since there is effectively less contact area between pad and rotor. quote]



no slotted rotors will run cooler and wont over heat there for you wont get brake fade

[Sic Lux]

Put a set of pads in a car at work customer supplied them fitted all sweet went to drive it out and had a real spongie pedal bleed them a kit through it. No good so thought maybe bad luck that master decied to let go when we done pads. Put a kit through it still no good racking our brains we thought why not look at what the pistons are doing. To a major surprise the pistons were pressing on the pad holdong pressure down when it was relised they moved back look at the pad material and it was actualy compessing so dont buy cheap pads put the old 1's in and not a drama so half a day wasted on crap pads

Slotted rotors help remove the gas that is caused from the friction heat when the pedal is aplied the reason for brake fade is the is that it is that hot the gas cannot escape fast enough there fore Brake fade this is where the drilling is the next step fo higher brake running temps on the road slotted and drilled rotors run to cold for optium brake performane unless your racing just run slotters drilled is only for looks or wank value on the road.

[BigMav]

I don't know what all this keeping them cleaner is about but the slotted rotors definitely run a lot cooler which will give you slightly better performance. I've had them on for a while now and occasionally they will clag up with mud.

[possum hunter]

I had slotted on my 4b and was very happy with brake performance but did hold mud.....wore good pads down to nothing on one very muddy track So i went back to std. Keep em clean and they will be great spesh on an auto