Brake pad question

Hey guys -

Just curious, at what point do you change pads? I was checking yesterday and my front pads are down to about 50% remaining, and I was debating whether to try and get one more weekend out of them. They've been on for a double school (Roebling) and the first three MARRS races (including two test days). I know the ability to dissipate heat goes down as the pads wear, but I'm not sure if the loss is proportional to the wear, or if the there is a point where it falls off dramatically. Btw, I'm using Blues on the front and HP+ on the rear.

One other question, do you always change rotors when you change pads? I have been, but am not sure it's necessary.

Thanks,
Earl

Earl, If you have half pads left you can definitely get the weekend out of them. Measure them now and after the weekend. I've seen pads come off of very competetive cars with as little as 1mm of material left at the end of the race and the cars did fine. Rotors don't usually get changed unless they get glazed or cracked.

See you at Summit.

Jason.

I personally change them once they get much lower than 1/2 pad left. And I certainly don't change the rotors each time I change the pads.

If I were smarter, I'd bring a spare set of pads with me to events. That way if they go beyond the "too low" point (not that I've ever gone to the metal), I could quickly change them at the track.

Earl,

At 50% is when I buy a second set of pads to keep in the parts box. Then check them after qualifing. Have other 240 guys look at them if your unsure there is enough left for the race. Luckilly I have others to base life off of based on what they typically get. I would never change rotors unless they are severly worn, cracked, or in my last case, warped very very badly.

Hopefully somebody else will chime in, but I don't think the pads have a whole lot to do with dissipating the heat. I think that's mainly done through the rotor and to some extent the caliper. I would think you can run the pads until they're pretty well used up. I'd get a new set to have on hand when the old set gets around 50% used. Brake pads are expensive so I want to get the most use I can out of them. I don't change rotors unless there's something wrong with them (warped, cracked, etc.).

David

Hmmm, sounds like maybe I've been wasting pads & rotors :( . I've been changing pads when they get down to between 1/2 & 1/3 pad left, and I've always put new rotors on when I change pads. Guess I'm a little too anal about that whole stopping thing :D . I'll run the old pads this weekend and just keep an eye on them. I always keep at least one set of spares (pads & rotors) with me, so if I notice any drop in performance it won't be a problem to change them out.

Oh, and you're right David, dissipate is the wrong term - insulate is probably the more appropriate word for what I meant. I was referring to the ability of the pads to retard heat transfer from the rotors to the calipers, which I believe declines as the pads wear?

Thanks guys. Jason, James, I'll see you at SP.

Earl

You can run the Blues down to nothing and you won't see a difference, at least that's my experience. You may consider getting a new set of pads and either bedding them in properly and taking them back off so you have some on the trailer already bedded or just install new ones, bed them in properly and keep the 50% set as spares on the trailer as they are alreay bedded. Same thing with rotors, keep a spare GOOD set that are already seasoned in the trailer just in case. I use AP600 fluid, Hawk blues all the way around and Brembo stock replacement rotors and easily get a season out of them with alot of events. The Brembos are the best I have tried and are about $35 new, I never turn or surface them, just throw them away and start with new. Good Luck, Chris

On a related topic, I'd like to know the interest in enduro take-off front rotors. That is, for every 12 hour enduro, I start with a new set of front rotors. We probably typically do less than 1/2 wear to them (especially at Nelson Ledges where it's probably 1/4 wear - if that). However, rather than risking a rotor change in the middle of the enduro, I always start with new rotors and pads.

So I now have a stack of rotors. I'll use a set or maybe two for sprints - but I run more enduros than the sprints use up rotors. So the stack will be ever increasing.

Would anyone be interested? The downside is that the rotors are for the ABS front brakes, and are the 4-lug style. And I think most people are running the non-ABS fronts.

Well, let me know anyway. I'm in the DC area (I doubt it'll be worth it to ship 'em).

(Also let me know interest on the brake pads - tho they go faster than the rotors seem to).

joe

Good topic - I am just a week late!

I run a 1989 240SX hatchback in ITA in ICSCC, the regional conference in the Pacific Northwest. I have the ABS front brake setup, and some excellent front ducts that Joe Harlan of TopTech Motorsports prepared and installed for me. The car stops very well, and may even have too much brake cooling on cool days (below 60F) which we get in early and sometimes late season up here. This duct setup has improved brake control and longenvity significantly!

I run Hawk Blues front and back, and the Brembo OEM rotors. This setup is proving to be very reliable and long-lived. I estimate that I am getting basically a whole season on the front rotors, and almost two seasons in the rears. This is an 8 - 10 race season. The front pads, which I replace at 1/3 original thickness (give or take a couple sessions) are lasting at least 5 race weekends. The rears are about twice that. The rears have no ducts, and don't need them.

I have tried Axxis MetalMasters, and can get away with using them on some tracks, but the Hawks are consistently superior and last longer, so I only resort to the MMs if I have forgotten to order the Hawks and find myself "in need" (hasn't happened in a couple years).

Mike Conatore

Thanks again for all the replies guys. Your comments bring up a couple of other questions:

1. For those of you using the ABS front brakes; did you switch from the non-ABS setup, and if so did you notice a big difference in stopping? I've thought more than once about switching, but when it comes time to order new pads/rotors I always seem to go the easy route - I mean heck, the car stops pretty darn well with the smaller setup, and there is only 5mm difference after all. By my calculations that's about 2 square cm difference.

2. I've asked this in previous threads, but it might be worth bringing up again - those of you running blues on both ends; are you using proportioning valves? I use the HP+ pads on the rear, and find that I still always lock up the rears first. Part of my problem may be that I haven't gotten around to installing ducts yet, but on tracks like Summit and VIR where there are only 2 - 3 hard braking zones that shouldn't be as big a problem, should it?

Earl even 2 heavy braking from high speeds is enough. But not as bad as other tracks. 2cm is not much advantage in braking and if your locking your rears first its time for a prop valve.

I changed over to the ABS setup very early in my time with the car, and relatively early in my driving career. It seemed to make a difference in that I could use the brakes harder before they got too hot. I suspect that with good ducts, the non-ABS setup would be more than adequate. (I have also learned not to overcook the brakes - I was kinda hard on the equipment early on..... :birra: )

I have never had a problem with locking up the rears before the fronts. I have been advised to use more aggressive pads in the front than in the rear, but I just don't seem to have a brake balance problem. I wonder if the coupes are different? I could probably use the MetalMasters in the rear, but have opted for my own perception of the "better pads". I did try the HT-10s (or was it -12s?) up front with Blues on the rear, but found that I didn't need the -10s, and they are more expensive, so the Blues are where I have settled.

Anyone out there tried any other brands on the 240SX?

Mike

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Thanks again for all the replies guys. Your comments bring up a couple of other questions:

1. For those of you using the ABS front brakes; did you switch from the non-ABS setup, and if so did you notice a big difference in stopping? I've thought more than once about switching, but when it comes time to order new pads/rotors I always seem to go the easy route - I mean heck, the car stops pretty darn well with the smaller setup, and there is only 5mm difference after all. By my calculations that's about 2 square cm difference.

2. I've asked this in previous threads, but it might be worth bringing up again - those of you running blues on both ends; are you using proportioning valves? I use the HP+ pads on the rear, and find that I still always lock up the rears first. Part of my problem may be that I haven't gotten around to installing ducts yet, but on tracks like Summit and VIR where there are only 2 - 3 hard braking zones that shouldn't be as big a problem, should it?
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I haven't been running a prop valve. I just swapped out the front calipers.

Perhaps the only thing to notice is that my car definitly locks up the fronts first. Is that a byproduct of using the ABS brakes?? I dunno! But in general, my co-driver comes in with the front tires squared, and the rears still round.

I don't run any ducting in the front either - and I wonder whether that affects things? I haven't done ducts since I don't seem to have any heat issues at any of the tracks you mentioned (Summit or VIR).

joe

I don't use a prop valve, never had any lock up issues. I have a set of hawk pads front and rears new in the box for non-abs set up if anyone interested? I also still have a 4.62 gear set and my S14 racecar for sale as a matter of fact..

I too can readily "square-off" my fronts if I am not careful, but I know that the rears are working also, based on pad/rotor wear and overall braking ability.

Slick - is that just the gear set, or is it a complete rear-end with diff?

Mike - [email protected]

Hi Guys,
Drivers of the 240sx need to listen to Mr.Newberry AKA "slicks14" concerning brakes....Having driven his car this past weekend, I've haven't stopped that quickly with the least amount of effort since falling out of a tree house many years ago.
Great brake pad combo. Well prepped car.

David

Thanks David but you did a great job driving so I think it was experience that matched the braking capability of the car!

Mike, The gear set is just the ring and pinion, it is like new and has only a couple of events on it, don't remember exactly how many but easily less that 5. Somebody on here was interested in it but I lost contact with them, I was supposed to get shipping prices but then I had a deth in the family and some other issues come up and I just put any racing business to the back. Anyways, the gear set is $375 plus shipping from 30341 zip code so figure up the shipping and call me, Chris Newberry, at 404-314-5042.

I know David is already aware, but I am in a position that I am selling my car so if anyone is interested let me know. I also have a pretty extensive spares assortment that will be fair game as pieces if it is not bought with car. We are fresh off a win at Lowes this weekend so the question of potential to win in these cars has been answered. The price is $17,000 for the whole enchilada...Spares includes fresh race prepped long block assembly, fresh trans, diff with Nismo LSD, Jim Wolf ECU, and much more...

Nothing much new to add, just throwing out another vote for Hawk Blues on all corners (perhaps HT-10s up front for heavy braking tracks (Sebring short course?) and Brembo OEM discs. I'm running the non-ABS setup on my ITA car and no proportioning valve. I've got ducting for the fronts but I've never done temp indicators with/without to see what their effectiveness is. Down here in Florida they've got to be worth something... I don't think I use the brakes hard enough (you know, they do slow you down :P ), but I would agree that my car tends to lock up a rear before the front when pushed hard. Some part of that may be the rear tires getting used harder also making them not stick as well under braking.
As for when to change pads/rotors: right before the friction material falses off the pad as you're installing new ones :) Yup, went through the car last week and the front pads were down to the rivets and one pad fell apart as I popped it out of the caliper; couldn't get any better than that. Ideally you should check the rotor thickness and runout to determine when to change them. The Blues are reasonably rotor friendly but they do wear out a rotor. And as was pointed out earlier, less rotor thickness = less heat discharge capacity. It all depends on usage, but anywhere from 6-10 hours on a rotor set would probably be typical (YMMV).
Also, I agree you shouldn't go racing on a brand new rotor. Make every effort to brandish the pad material on the rotor before a race.
Good luck have fun,
Michael