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Discussion Starter · #1 ·
Hey folks, just a word of caution when using slotted rotors.
"Applies to Baer & I-Rotors slotted rotors, and possibly others!"
"Pay attention to mfg's directions!"
"Slots may be directional!"
"Contact manufacturer if you are unsure."
At a recent tech day a couple of us noticed that our club presidents rotors seemed to be facing the wrong way, and we mentioned it to him.
Any way the next day he brought his car into the shop to re-do all 4 of his rotors, and they discovered that even though they(a different shop) had used locktite when putting on his rotors the caliper bolts had backed out to less than 3 threads on each of his right rear caliper, and the other 3 were all loose.
The mechanic called up Baer and asked a couple of questions and was told that when slotted rotors are put on backwards they create harmonics that will back out lugnuts and even locktited caliper bolts and could cause a disasterous accident.
So make sure your rotors are put on correct folks!!!
 
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Discussion Starter · #3 ·
It is also possible they re-used the bolts.

According to the FSM, the bolts are one time use only.
 
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Discussion Starter · #4 ·
Anyone got the p/n for the caliper bolts. And by "caliper bolts" on the REAR we are talking about the cailper to bracket bolts, not the larger bracket to rear end bolts, correct?

Are the front bolts supposed to be reused at all?

And are the slots supposed to be directional or anti-directional? I was never clear on that one but I didn't know it mattered.

Thanks,
Aaron
 
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Discussion Starter · #5 ·
Just what is the proper direction for the slotted rotors?

I have PowerSlot rotors and the air vanes are not directional. The rotors had stickers on them showing what side to put them on, so I did what they said and the slots were spiraling out when moving forward. In other words, at the top of the rotor, the slot starts at the hub and leans back towards the rear.

On websites of other brands, they always show the slots facing the other way. Sprialing inwards and giving a scooping appearance when moving forward.

Without the directional vanes, I guess they could technically be mounted either way. So which way is right?
 
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Discussion Starter · #7 ·
Originally posted by Aaron D:
Anyone got the p/n for the caliper bolts. And by "caliper bolts" on the REAR we are talking about the cailper to bracket bolts, not the larger bracket to rear end bolts, correct?

Are the front bolts supposed to be reused at all?

And are the slots supposed to be directional or anti-directional? I was never clear on that one but I didn't know it mattered.

Thanks,
Aaron


Dorman p/n 619001 - available from RockAuto plenty cheap. New brackets, pins, and bolts. Yee-haw.

And here's a handy discount code while we're at it.

210309206247
 
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Discussion Starter · #8 ·
SLOTS

On a straight-vane rotor, the direction OR rotation of the slots doesn't seem to matter. On a true directional-vane rotor, I'm of the opinion that having the slots run the OPPOSITE of the internal vanes is a matter of less compromise in the strength of the rotor, with the slots cutting ACROSS the vanes rather than in parallel with the (angled) vanes.

This seems to me to leave the rotor surfaces more stable when slotted. This is just my opinion, but look at how Baer does their slotting on directional rotors--and I;ve noted a number of race vehicles with slots running them as Baer does.

Other brands I'm not aware of how it is done--I do suspect the Autospecialty AR9501SL and AR9502SR slotted HD directional front rotors have the slots parallel to vane angle, more to be consistent with the rears, and more as a cosmetic than TRUE performance enhancement.


BOLTS

http://impalassforum.com/noncgi/ultimatebb.php?ubb=get_topic;f=33;t=001279

BRAKES

18022147 rear caliper guide pin
14067559 rear guide pin bolt
12337902 rear caliper bracket bolt
14067552 rear caliper guide pin boot
 
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Discussion Starter · #9 ·
I'll agree with most of that as I've stated much the same.

As for the comment on harmonics; yes this has been talked about by a couple of makers. The issue is having an equally spaced cut on the rotor. And one running at very high rate of speed. However the direction of the slot had nothing to do with it from what I have read.

This was addressed here:
http://www.wilwood.com/Products/002-Rotors/002-GT/gt_big.jpg
Where you'll notice the pattern is both non directional as well as staggered. See that the slots are NOT equally spaced? Look close, you'd think it's a mistake at first.

As for causing loose lug nots on a street car with the slots going one direction or the other? I'm not buying that one.
 
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Discussion Starter · #10 ·
Adding to Todd's comments, I think the racing community has modified its views on slotting considerably.

What EVER I may use the next time I renew rotors, they will be plain Or of a "slotted" setup that is considerably different from the standard full-width slots found in most aftermarket rotors for domestic cars (PowerSlot, PowerStop, Rotors-R-US, etc), as I believe there is virtually no advantage attribuatble to this type of slotting.

Here's an example:

http://www.performancefriction.com/pages/rotor_tech.htm

You can also see how this arrangement DOES parallel the vane angle, but the cuts in the rotor face are much smaller and shorter and result in far less compromise of the strength of the full friction surface.
 
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Discussion Starter · #11 ·
Hi Bill, It was Peter's car, this was the info given to me by Peter from the mech who re-did his brakes.
Maybe I should change my first post to say, "Applies to Baer & I-Rotors slotted rotors, and possibly others!"
"Pay attention to mfg's directions!"
Also, "That slots may be directional!"
"Contact manufacturer if you are unsure."
 
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Discussion Starter · #12 ·
It took Peter long enough to decide what to get!!! :D

I guess he thought it might be nice to have them for the Grand Canyon run....

http://www.baer.com/Support/FAQ.aspx#11

(quoted from above)
How do I know which way to install my new rotors?
Internally, all Baer rotors are directionally ventilated and they must rotate in the correct direction to obtain proper airflow for cooling of the rotor. An arrow is machined into the mounting surface of one-piece rotors, and laser etched into the hat section on two-piece units. Failure to install the rotor in the proper direction will cause an overheat condition and premature failure. This error is easily determined when rotors are returned to Baer for visual warranty inspection. To see which way your rotors must be installed, please use the link to our Tech Tips. This page will have all the information you need to ensure correct rotor direction.

http://www.baer.com/Support/TechTips.aspx?TechTipID=2
 
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Discussion Starter · #13 ·
Originally posted by Todd TCE:
I'll agree with most of that as I've stated much the same.

As for the comment on harmonics; yes this has been talked about by a couple of makers. The issue is having an equally spaced cut on the rotor. And one running at very high rate of speed. However the direction of the slot had nothing to do with it from what I have read.

This was addressed here:
http://www.wilwood.com/Products/002-Rotors/002-GT/gt_big.jpg
Where you'll notice the pattern is both non directional as well as staggered. See that the slots are NOT equally spaced? Look close, you'd think it's a mistake at first.

As for causing loose lug nots on a street car with the slots going one direction or the other? I'm not buying that one.
I was the guy who brought up the rotor slot direction to the member mentioned in the original post.

I also have the Irotors and last year had originally put them where the slots trailed from the center when rotating forward.
After awhile I started getting a popping noise when applying the brakes, usually under 30mph. I also now remember there was a intermittant high frequency vibration with brakes applied, usually at freeway speeds.
I traced the popping noise to the rear calipers, I believe when the pads were hot and applied, they would "bite" into the slots and be forced suddenly upwards in the caliper against the anti-rattle H spring. At lower speeds I believe that caused the popping noise and higher speeds the vibration. The front pads are tensioned different so not sure if the slot direction caused anything.

I went ahead and swapped the rotors side to side to correct the slot direction after that (same as in the last Baer link). So far no more popping noise or high frequency vibration.
 
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Discussion Starter · #14 ·
I won't disagree with the results, if it worked for you that's all that matters. But by moving the rotors side to side you also made other changes along the way. That negates the validity of the claim a bit. Just removing the the caliper, the rotor (dust cap, cotter pin, bearings) then futzing with the pads for a minute as you put it all together...it's tough to say you 'just switched the rotors'.

In both cases the pads would be lifted in the caliper. In fact any slot could be accused of doing that.

If it goes this way / or this way \ when it goes around the pad is swept. I guess you could claim that one of them starts at the nose of the pad and the other at the heel of the pad but both cover the same ground. I'm just having a hard time seeing how one would move the pad more than the other.
 
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Discussion Starter · #15 ·
Yes I agree the slots cover the same area but not at the same time. When angled / (going <), what I think happened is the bottom of the slot is encountered first by the pad and the angle of the remaining slot can push the pad up as it grips the rotor.
This is what I think happened on the rears, the noise was definitely from them and not the fronts.
 
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Discussion Starter · #16 ·
Guys, what pushes pads is the force resulting from making a 4000+ lb land yach (or a <2000 lb Lotus Elise) stop. Any possible force resulting from a slot "catching" an edge of a pad is negligible compared to the friction forces that result from the pad being pushed against the surface of the rotor.
A slot could possibly push a pad in some direction when the pad is first coming into contact with the rotor, but after the brakes are applied, the friction forces get to decide where the pad is pushed.
Tim
 
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Discussion Starter · #17 ·
I go back to what I said before; when you have a properly vented directional rotor with holes in it the drilling process must be done in a manner that vents all the air passages. Add to this the ever popular -yet redundant- gas slot and it to must be cut the same direction.

From a manufactures point of view you now have a rotor that is 'directional' in both design and appearance. So what do you do when you have a non DV rotor or you only sell the customer a slotted and not drilled rotor? You mill them the same way the program is on the mill for the other application. Or in my case- you have slots and holes in one direction and slots only in the other! Yea, it's messy and I'll probably convert it in the near future. Why? Nothing at all to do with function, only to keep the parts similar in appearance and avoid the questions.

Slotted rotors (with the vane as mine are) have been around for dozens of years. The effective but unusual looking tic-tac-toe pattern (that I used to use) was done by Tilton and Carroll Smith back in the 60s. Today angle slots, rings, circles, check marks, they all are the rage. Or the best- just ask the folks selling them.

An interesting side note to my discussion on the other thead about slot value in general- what's to be made of the hash mark (latest and greatest) from copanies such as PFC or AP?? Do a quick search and you'll see what I mean. A dimple or hash mark that is fully under the pad and of very small area I can't see being terribly effective. While not scientific, I'd place it's value between that of no slots and a full slot.
 
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Discussion Starter · #18 ·
BRAKES

18022147 rear caliper guide pin
14067559 rear guide pin bolt
12337902 rear caliper bracket bolt
14067552 rear caliper guide pin boot
How many of each part number would be needed to do both sides?

EDIT: I also read in another thread that I can get a whole rear caliper bracket from "Autozone for 18.99 per side (comes with guides, boots and lock bolts)" Price aside.. would that include everything that I might need? If I'm going to have it all off, I figure I'm going to replace this stuff and be on the safe side. I just want to make sure I get all the goodies I need.

How about seals or new front bearings? Anything worth having on hand and/or just replacing period?

Dave
 
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Discussion Starter · #19 ·
Hey guys this just happened to me. I installed the rotors correctly with the slots trailing to the rear see pic of the passenger side.



I was backing back and the car went no were. The bracket come off and it hit the rotor metal to metal. Now I did remove calipers to paint. I see someone stated that the FSM says bolts only use once. Is this the problem? Did the other guy this happend too remove his bolts too or just put the rotors on wrong?

I lost one bolt and have replaced it with a grade 5 bolt and put lock washers on both. Should I replace all bolts. I do think the lock washers will help some what. And I did use red permanent loctite meaning it shouldnt break unless torque is applied. Any replys?
 
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Discussion Starter · #20 ·
The Rear caliper bolts should be replaced, or you can use RED loctite on the old ones and sock them on good.

I believe new caliper bolts come with loctite already on them.

When I take off the RR sometime this week because Something is always squeaking on that corner, I am personally just going to loctite the caliper bolt.

--

Just buy new caliper bolts because one already fell out. They can't be that much $$.
 
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