While installing the $35 utility straight vane rotors I cannot help but to notice their quality. I order them because the price is right and until I have my ventilation sorted out I want to mitigate the damage to my wallet buying the expensive Spec 37 directional vane ones. The fact that these rotors has balancing cuts shows that they are well made, especially at this price point.

I also pondered as to the difference between straight vane versus curved vane at the end of the day, so to speak. I am no aerodynamic engineer but I have pretty good grasp on elementary physics. These rotors are basically like impellers in their air cooling. The impellers function largely by centripetal force of the mass of the air molecule when spun at speed. The air will circulate form the inner diameter to the outer diameter of the rotor with or without curved and direction vanes. The main difference is the quality of laminar air currents.

Assuming the cast iron material being equal (which I infer they are not) I suspect the cooling difference are not as huge as we tend to assume.


a balancing cut on the $35 utility rotor


after 3 sessions at PIR; not the coloration near the interface to the AL rotor hat showing the big temperature gradient



the back side of the rotor

And BTW, these cheaper rotors differ to from the Spec 37 that there is less meat at the mounting tabs, for what that's worth.

 

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I took MrBlah’s comment about covering his brake ducts to be in response to my comment about the BP30s gumming up the rotors when they were not warm/hot enough. I have seen the Wilwood temp curves and it seems that should not be an issue. I have been thinking about this since the issues I had on Friday, where when things were dry the BP-30s worked fine and not fine when it was rainy and clearly the brakes (rotors, calipers and pads all together) were cooling between heavy use. It seems that in heavy use with everything else cold, they get gummy and when everything stays at an elevated temperature they don’t get gummy. My two previous days with these pads were warm, clear days and the BP-30s worked fine. I have also been wondering if this was the issue with my Poly H pads that were gumming up my rotors. Maybe I really should have been using the Poly B pads. I know my stock car pals use the Poly H with no problems. So, it appears that in the right situation they are good. In mine, not so good. I had a similar experience with the Hawk DTC 60 pads during a track event where they didn’t have enough heat in them and they became really abrasive and wore out a set of rotors. But when they were hot (different track) they worked great.

Not sure if that makes sense or not.

As for bending your Torx driver - that surprises me. I had no issues when tightening the bolts at 25 Ft-# even with the cheap HF drivers. Now, when I torqued them to 55 ft-# (brain fart) the driver didn’t stand a chance. Do you heat the hats to loosen the Loctight when loosening the bolts?

I think I mentioned this before, but I’ll bring it up again - I had 3 or 4 of those Wilwood Torx head bolts where the head broke off. I replaced them all with Grade 8 hex bolts. Just a thought.

 

My experience with the BP-30 was they seems to be quite soft though I didn't find them lack of grip. They have nice modulation out of the gate, just didn't last. I am beating that horse to death. At least they were cheap for what I paid.

So I tested out the ST-35 for front at PIR and am happy with them. Raybestos production line is down and that leave a lot of very unhappy customers, and this includes Joe Blows like us, racing brake shops like my pad go to guy, and some big name performance brake companies. A little birdie told me that a lot of leading brands use their friction material (and I infer many are built by Porterfield). The smart ones had stocked up their pads in advance of Raybestos production line down. The only ST pads there are left are the ST-35 for our Wilwood fronts. I grabbed two more sets of ST-45 to tide me over to their resumption of production. They are much cheaper than Hawk DTC-60 and I was told they are nearly identical - so you can do your math.

I didn't need to heat up the hat to remove the Torx bolts with red Loctite, but they didn't come out easy. That is why I place the rotor on the vice. One set of the Torx tip I used were auto parts store junk but the other bit is a proudly made in USA. It however felt soft to me given how much I paid for the set. I think it is just crap and flag flying means jack ****. I couldn't find my other set that is HF and is quite good.

I swapped the rotor hat L to R to even out the wear of the 4 oversized lug holes.

I remember you replaced the Torx with hex bolts. Aren't grade 8 is next level down form typical 10.9 used in automotive? The Wilwood Torx looks like SS to me. I infer must be for corrosion resistance due to the AL rotor hat. SS is brittle typically compared to high medium carbon steel.

 

Learnt something new today on the designations of fastener grades which had left me wonder why 10.9 and 8.8.

"12.9 grade steel means that a component manufactured form this grade of steel has 12X100 N/mm^2 tensile strength and 9 is a multiplier means 90% of 1200 = 1080 N/mm^2 is the yield strength of the grade.
Similarly we also have grade 8.8 , 10.9 , 6.8 also. This is imperial method implied by engineers to differentiate between different sets of steel grade. "

The leading number is the tensile strength that is multiply by 100. The number after the dot is the yield strength. Now all make sense to me short of pulling one beyond yield strength with my hands.

With this table it is so much easier to understand.

 

This is a video that capture the moment (@15:00) I noticed something on the front end not right. I was driving Desire quite hard trying to fend off the red M3 and another BMW track cars.

I slowed right down and then limped back to the pit. Sure enough 3 bolts were many turns undone and the other one undone at least a turn. The left front wheel would have fallen off if I continued to drive hard and would not last pass that lap. I torqued the lugs to spec before this session. In retrospect I should not have limped back.

 

The replacement axle for the left front arrived to replace the one has a tiny puncture on the outer grease boot.


the new replacement left front axle

I examined the boots carefully this time; I only noticed now that the asymmetry of the folds with one side dome shape and the other flat to accommodate the sharp turning angle at full lock

no visible puncture so I proceed to pull out the defective one

to my amazement the inner boot also spread CV grease all over which I didn't notice before

I needed to use a small chisel to separate the ball joint from the steering knuckle


I couldn't budge the axle nut even with a long lever on a wrench


I then use this Ridgid 1/2" impact gun and it had no problem getting it loose


after cleaning off the grease I found a long slit on the inner CV boot


one mistake I made is to jack up only one side of the car and this put odd strain on the sway bar drop link; one of the ball popped out of the plastic socket but I was able to popped it back into place

There is no explanation for the big puncture on the inner CV boot. It could not possibly happen during or after the installation.

Again I could not seat the axle into the differential until I remove the C-clip and reshaped it. Fortunately for us we got the job done that afternoon. The night would bring downpours like we'd never seen before.

 

When I saw these set of bracket on Advanced Auto Fab site it has the appearance to be well designed and made. The bracket covers only the inner diameter of the rotor and direct air to the intake of the vanes. To be sure I called them up and asked if it is compatible with Wilwood. They arrived and I test fitted one while replacing the axle. I took ample photos and studied the constraints of routing a brake duct hose in the tight confines of the wheel well with these wide tires.





the nipple is at this angle for a very good reason; note the strengthening creases on the bracket



I had the foresight to save the three torx screws in their place after removing the stock rotor dust shield two years ago



you can see how little gap there is between the duct bracket and the rotor inner face



view from above and it is clear the reason for the slight angle of the nipple






at full lock turning right






view from above at full lock turning right



view from above at full lock turning left

These photos were taken with the suspension at full drop. I need to place Desire in the normal suspension position and check the cooling hose routing. I would do that on the Trailex trailer. These brackets are made for 3" dia silicone high temp hoses.

 

Oh, my new set of cut rate copper spark plugs just arrived from Rockbottom Auto via USPS. All four under $8 mighty Yankee dollars including shipping fee.

These are the cheapest NGK plugs money can buy and Desire likes them. Never miss a beat wide open throttle at the track shaming higher power cars.

 

The grade 8 I referred to is the SAE strength rating which (I think) is about the same as the 10.9 metric. Grade 8 is a high strength bolt and applies to the 5/16 bolts I used on the Wilwood hats.

 

Cool. That explained it. We are used to what the local HW store signs of there grade 8 fasteners and to get 10.8 I have to go across town to a large well stock store to get them. I know there are ME's spend a whole career specialize on nothing but fasteners. It is a huge field and so many standards, SAE, ASTM, and ISO just to name a few. SAE Grade 8 and HW store grade 8 are totally different animals. The whole Wilwood kit is Imperial down to the holes for the two metric bolts that mate to the steering knuckle. That is why there are the two strange aluminium (correct spelling) sleeves.

 

Grade 8 should be grade 8 no matter where you buy them. They will have the 5 hash marks on the head. But I got mine from Fastenal...
Here is a link that gives some basic. I sure there are more technical sites if I searched harder...
https://www.fastenermart.com/underst...d-classes.html

 

We drove at PIR this past Friday afternoon and Desire donned the Nitto NT01 *** slicks. I didn't want to switch wheels the last minute because there would always be a lesson to be learnt. In this event is to find out what is it like driving a set of tires with no tread left to channel water. It would turned out we improved over last season's lap time by over a second. Our lap times were also more consistent.

I have been using iMovie to stitch together GoPro files which typically are three for each ~20 session at 720p/60. The rendered files is more compact for uploading to Youtube unlike in the past Youtube always bitched about the size and CODEC. It is very fast now except iMovie would crash each time I drop three files into the media pool. It is just a minor annoyance and I can deal with it well.

This is the second session of three. The red Gulf R is faster due to significantly more power and torque but Desire gobbled up everything else on the track like PAC-MAN.


I relocated the external mic onto the dash and cover it to reduce the wind noise. Only the Hero 5 Black auto-detect external mic (there is no manual override) malfunctioned again as always. At least there is some sound.

 

I wanted to reduce the rattles and gearbox shifter noise the microphone picks up and I thought on the dash center very close to the windscreen would be protected most by the wind buffeting. The location should pick up a bit more of the supercharger whine too. When I examine the dash closely I realize the air vents make great cable tie anchors.


one tie securesthe stereo microphone



the second tie secures the cable and the third tidy up a few cables






old sock makes nice wind muffle; the ties would be trimmed flush

 

I went back and looked at my logs, it was the ST43 that glazed up when they ran too cool, not the bp30.

On the subject of lug bolts, autocrossing & constant tire changing got old quick! I put extended studs on right away they have a little flange (apex studs), that seems to prevent the rotor from twisting I've not seen or noticed the rotors twist, and I'm not even sure that rotor hex bolt is required I know people that run without it. I run with the hex bolt but I only tighten it a little bit, the stupid things seize on me.

Careful with those cheaper wilwood rotors, I only got a weekend out of them! On my setup the pad area crossed into the machined area, they only lasted a day, cracked in a scary spot! every single mount tab had a crack like this

 

Many of the smaller BMW (E30s and the like) run these Wilwood rotors and I have seen at least one rotor with that larger cutout with that same cracking. And, likewise, concluded it was a result of the pad running out in air over the cutout.

I get a little twist on my rotors and see some tread marks on the hats from the wheel bolts. But the rotation is minor and the Torx bolt has never been damaged. I too only put that bolt in hand tight and with a little never seize. You might be right that the 14mm bolts and the little flange on the studs is enough to keep that rotation to a minimum.

A side note on that subject - I have been told by an ST class IMSA driver that if you chalk mark the tire to the wheel, you will see that the tire slides (rotates) on wheel and that after a race the mark on the wheel and tire won’t be lined up. I’m not surprised that the wheel rotates relative to the brake rotor hat.

 

I marked my tires/wheels and they have not moved on me, but i'm not running hoosiers, and the 949racing wheels have knurling in the bead area. Some of my friends have seen movement, one moved enough to throw off balance. It is of the reasons (ok excuses) I used to justify a tire & wheel balance machine.

I'm using 12mm studs

APEX 75mm M12 BMW 4 Lug Bullet Nose Stud Kit - Black
SKU: APEX75STDM1215KIT4BLK-BL

 

On the subject of tire rotating WRT the wheel I only encounter it this past event at ORP. The SC Miata guy shared with me that he learnt to mark the tire and rim with the Hoosier R7 to detect the tire's slippage. The two wheels he showed me rotated by nearly an inch with his short drive that day. He said that happen because the R7 gets so gummy. He told me Hankook Z214 would not rotate.

The counter sink rotor retaining bolt does nothing except to prevent the rotor from falling out or skew before you put the wheel on. I lived with the bent ones and just not tighten them tight at all. All my 4 are bent as I swapped the rear to the front.

I went thru all my lug bolts and checked them with a caliper. There are two that are clearly stretch with one visible. I measured two diameters and the length. The bolt lengths varies a bit due to how they are cut by machine. It is hard to say if the bolt stretch is cause or effect thought. The new wheel smooth countersink finish might had been the cause. They are not painted but quite smooth.

I had a complete set of German brand coming.

 

I should add that the Konig Dail In are cut to support 14mm lugs too. All of these are factors that contribute to lessen the clamping force and increase the tendency to rotate (not the tire WRT wheel we discussed).

 

 

I wish there is a better track map that depicts the elevation changes of ORP. This is the only one I can find. Image credit - Ride Done Right. There are 400 ft of elevation changes each lap. We drive CW one day and CCW the next day and it is like driving on two different tracks. And there are many on and off camber turns so often the classic text book best lines go out of the window fast.



here is the official track map with many creative names for the segments of the track; the one I like most is Valkyrie Hill - cue Die Walküre



Die Walküre - strangely this Met production's cadence seems too fast

I prefer this one by maestro Baronboim with Berliner Philmonikar

 

I see at least 4 heavy brake zones too.

 

I don't know if you've looked into these or not, but I've had brake challenges too, but I like my fog lights. These look like a decent way to have brake cooling and fog lights, though loading/unloading the trailer might be complicated. https://new.minimania.com/part/NMB40...Mini-Cooper--S

 

For me it depends on CW or CCW. CW there are 4 but CCW 5. My times are quite close both configurations.

And by heavy braking zones we are referring to braking from high speed into a tight turn, where downshift(s) and threshold braking need to be carried out concurrently.

 

PNW Miniac's. If you sign up Portland BMW Club track day 30 days or more in advance you save $50. It is a well ran HPDE and one of my favorites. Next two events at PIR:

June 6
July 18

 

Desire is a Maniac. She tried to have us both killed in the last session at PIR this past Friday. A little bit of drama at 16:00 begun at turn 10 going in a bit too hot . Oh, and who turned on the cruise control?