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AP Racing Radi-CAL Front Competition Brake Kit Review

Dangerous Fish

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@beastmode13 @MasterC17 I'm getting close to fitting these calipers to mine and the decision of whether to leave the anti knockback springs in needs to be made. I know they're easy enough to take out/in, but I'd like to get some more feedback from you both now you've lived with them for a while. It comes down to a noise/efficiency loss tradeoff I guess, but with them out did either of you actually get any pad knock off to speak of either on the road or track?
 

MasterC17

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Dec 3, 2015
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@beastmode13 @MasterC17 I'm getting close to fitting these calipers to mine and the decision of whether to leave the anti knockback springs in needs to be made. I know they're easy enough to take out/in, but I'd like to get some more feedback from you both now you've lived with them for a while. It comes down to a noise/efficiency loss tradeoff I guess, but with them out did either of you actually get any pad knock off to speak of either on the road or track?

Mine are in and always have been. I haven't had any noise, but I think @beastmode13 did. If the car is also your daily driver I would remove them. If it is not, I would leave them in.
 

Dangerous Fish

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Mine are in and always have been. I haven't had any noise, but I think @beastmode13 did. If the car is also your daily driver I would remove them. If it is not, I would leave them in.
If there's no noise the only other drawback would be some range loss then. Do you still think it's as much as 8%?
 

MasterC17

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If there's no noise the only other drawback would be some range loss then. Do you still think it's as much as 8%?

Like any range calculation, it's really no better than a guess. After driving two Performance 3's on the same route on similar tires a few times (275, 200TW), the difference averaged 8%. But, it was on different days and different driving.

I can tell you if I drive the car a few miles, don't use the brakes at all, park it and put my hand up to the wheel I can feel heat, so the pad is definitely contacting the rotor.

Tire selection will have a bigger impact on range; 8% is like going from the OEM 18's to the OEM 19's, a lot of people do it and sacrifice the range for the style.

I will try to get both cars out at the same time on the same tires to do a legit test, but it probably won't be for another month at least.
 

Dangerous Fish

Pilots the Millennium Milkfloat
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Yeah, so I think the decision for me is going to based mainly on whether there is much (or any) pad knock off with them removed.
Pad knock off can happen for a few reasons but in racing it's often kerb-hopping which I tend not to do on track days :rolleyes: (well maybe every now and then). Otherwise, if everything has been properly engineered and installed there shouldn't be a lot of knock-off happening on the road or track. Interested to hear what @beastmode13 says.
 

beastmode13

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Yeah, so I think the decision for me is going to based mainly on whether there is much (or any) pad knock off with them removed.
Pad knock off can happen for a few reasons but in racing it's often kerb-hopping which I tend not to do on track days :rolleyes: (well maybe every now and then). Otherwise, if everything has been properly engineered and installed there shouldn't be a lot of knock-off happening on the road or track. Interested to hear what @beastmode13 says.

I daily my car. The buzzing noise when the rotors are new drove me nuts, it gets louder with speed. Sounds like saccade. So I took them out. I finally had the opportunity to track the car without AKBS a few weeks ago it felt great. AP caliper is so direct to begin with, without the AKBS is still the most direct brake I have felt in all my driving experiences. After the track day, the buzzing noise is completely gone. So I think the buzzing was caused by the sharpness of the edges of J hook slots. A good day at the track seems to soften the edge to the point where it does not generate any more noise than solid rotors. I have not driven my car since the track day, so I can't say if it will stay quiet or not. I have a track day coming up this weekend, will report back afterward.

@MasterC17 tracks his car more often than me, but not heard of noises now. While it was new, he did report hearing the same buzzing noise. Further, boast my theory about the fresh edges is the cause of the noise.

FYI. My efficiency hit was ~15% with the AKBS installed.
 

Dangerous Fish

Pilots the Millennium Milkfloat
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Interesting. Thanks. On balance, I think I'm going to install them initially without the springs and see how it goes.
First chance to try them on track is likely to be the end of September, so I'll report my findings then.
 

beastmode13

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Thanks for the info @beastmode13, another quick question from me if I may. Have you noticed any efficiency loss with the AKBS removed, compared to the standard brakes?

Without AKBS, the efficiency is the same as with my previous setup of RB 380mm BBK and stock Performance+ red Brembo. I couldn't be happier with AP Competition brakes. The feel is very consistent from the first lap to the last lap of the day. The 9660 caliper is a very popular racing caliper, so there are tons of pad options from all the major players. The pad selection is a huge plus.
 

MasterC17

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@MasterC17 tracks his car more often than me, but not heard of noises now. While it was new, he did report hearing the same buzzing noise. Further, boast my theory about the fresh edges is the cause of the noise.

Good catch, I forget about that. I did have a rotational friction noise for the first few hundred miles of driving but it went away and has not returned.
 

Dangerous Fish

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Good catch, I forget about that. I did have a rotational friction noise for the first few hundred miles of driving but it went away and has not returned.

As I said in the other thread about brakes, cross drilled or slotted rotors always have the potential to generate a bit of noise and 'feel' in the pedal but it makes sense it would be worst when brand new and not fully bedded. Good to hear they've settled in for both of you and working as intended.

Looking forward to finding out myself :D
 

MasterC17

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As I said in the other thread about brakes, cross drilled or slotted rotors always have the potential to generate a bit of noise and 'feel' in the pedal but it makes sense it would be worst when brand new and not fully bedded. Good to hear they've settled in for both of you and working as intended.

Looking forward to finding out myself :D

You're going to love them. They're sooooooooooo nice!
 
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Dangerous Fish

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You're going to love them. They're sooooooooooo nice!

They've arrived. Fitting this weekend.
The OE rotor top hats are very thin. Has anyone worked out why they made them like that?
Fitting some 'proper' discs is going to affect the offset by 4mm or so. Has that caused anyone any issues with the stock -35 offset?
 

Mash

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They've arrived. Fitting this weekend.
The OE rotor top hats are very thin. Has anyone worked out why they made them like that?
Fitting some 'proper' discs is going to affect the offset by 4mm or so. Has that caused anyone any issues with the stock -35 offset?
I'm concerned about lug nuts engagement, other than that 275x35 r19 et30 was ok. I believe they don't use aluminum hats, so that's the reason it's thin. I don't think that aluminum is a good choice for rotor hats at all. It's just easier to make hats on CNC in small quantities, but there is no weight or thermal transfer advantage. OEM can invest in high precision stainless stamping mold due to volumes. It's cheaper and better.
 

Dangerous Fish

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I'm concerned about lug nuts engagement, other than that 275x35 r19 et30 was ok. I believe they don't use aluminum hats, so that's the reason it's thin. I don't think that aluminum is a good choice for rotor hats at all. It's just easier to make hats on CNC in small quantities, but there is no weight or thermal transfer advantage. OEM can invest in high precision stainless stamping mold due to volumes. It's cheaper and better.
Yes, good point about lug nut engagement. Guess I'll find out in a day or two...
 

Dangerous Fish

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upload_2020-9-26_18-26-14.png


Looking good. Bedding them in tomorrow...
 
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Dangerous Fish

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Do you have a different distributor in the UK? Rotors are slightly different. They look good! What pads did you go with?
Yes, Essex are N.America, we have a different one here.

I've gone with APF404 pads initially, as they are similar to the Carbotech XP10s I'm running in the stock rears.
The rotors are 378x34mm.

All ready for the track on Tuesday...

WhatsApp Image 2020-09-26 at 18.51.33.jpeg
 
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