Urge Flow Rear Rotors Experience
 

Hello, I wanted to post a short review on a problem I was having with my rear brakes and what I did to fix it.

A little background, I am running a AP1 with AP2 size Michelin pilot super sports and Ohlins DFV coil overs. For the brakes I was just running Stoptechs OE replacement slotted rotors and Hawks fairly new Street/Race pads. I try to track the car at least once a month.

I was at Buttonwillow raceway with a friend who tracks a BRZ and we had a infrared temp. gun with us. I noticed that my rear pads always seemed to be smoking a bit after each session and his did not (BRZs have vented rear rotors). taking temperature readings of the rotor face I noticed mine were 100 or more degrees hotter. (BTW I know they don't recommend infrared temp guns to measure temps on shiny surfaces but it seemed fairly consistent as I did it after multiple sessions.)

At home doing some maintenance I noticed my rear pads had some smallish chunks missing out of them. I sent pictures to Hawk and they replaced them but I figured the temps they were reaching were to high.

After searching around the best solution I could find with out having to upgrade the front brakes as well, was Urge Designs Flow Rear Rotors. The Rotors are very pricey but It’s cheaper than purchasing a whole BBK. Plus, they do look nice and they are lighter than OE.

With a new set of Hawk’s Street/Race pads I went back to Buttonwillow with Both OE rotors and the Urge’s. I ran a session with the OE rotors and then switched to the Urge ones between sessions. I took temperatures at 3 places; the rotor face, the rotor hat, and the back side of the knuckle next to the wheel bearing. My readings are bellow in Fahrenheit.

Rotor Face, Rotor Hat, Knuckle
OE 510, 261, 210
Urge 360, 220, 210

I didn’t do an uncertainty analysis or anything to determine the precision of my readings nor did I take the ambient temperature (It was at least 10 degrees warmer when running the Urge rotors) but it is clear the rotor face was cooler. On Urge’s website they claim the rotors will help save your wheel bearings as well but I didn’t notice any large temperature difference so if that is your main reason for purchasing the rotors take that into consideration. All in all I think these rotors will help bring my pad temperature down so I think it is a good upgrade.

Those are some surprising numbers. I would have assumed a cooler rotor would translate to a cooler everything in that region.

Did you happen to measure caliper temps as well?

Unfortunately I did not measure caliper temp. and yes I was surprised also that the knuckle wasn't any cooler.

Cool, nice to see some real numbers, thanks for sharing

Measured the same way, for me a vented 2-piece rear was good for roughly 200 degrees rotor temp reduction on XP8s. My vented rotors were larger than the Urge model, though, so that all adds up. As some of the vendors have correctly claimed, doing this mod also seems to improve the ability of the fronts to withstand fade towards the end of the session (you don't lose the rears as the session progresses, so the fronts don't end up trying to pick up the slack). 360 degrees is totally manageable, so looks like the Urge rotor is big enough for your use. :)

Units anyone?

I'm assuming Celcius...

While it's good that someone is trying to test their actual functionality, this test ultimately just leaves many with more questions than answers. Where/how did you measure the temperature at the knuckle, right where the axle nut goes on? Did you just do one session with each? What kind of times do you run at BW? What street/track Hawk pads are you running? Also, BW I don't think is very hard on the brakes correct? That affects how much heat you're putting into them also.. Too many variables to come to any conclusions but it does look like they're running cooler which is good.

I never bothered to check the temperature of my rear rotors with my IR gun (probably should have), but even getting near my rear wheels it was like putting my hands close to a fire. I can't see how the solid rotors aren't putting substantial heat into the rear bearings in my usage. This might be a "your results may vary" sort of thing depending on usage.

BW - assuming it's CW13 - is pretty rough on brakes. The only other configurations local SoCal tracks that might be rougher are ACS and SOWS (CCW - CW, not so much). There are 4 to 5 heavy braking zones going from 5th-->3rd gear or 4th-->2nd.

Sorry, Fahrenheit for me.