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Bfranklyn86

Stoptechs vs AP racing 4 pot BBKs

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I had a number of issues with K-Sports, probably the most noticeable was the amount of pedal pressure required. They also got very hot

But Stoptechs also have an issue with the rear caliper pad retaining pins. These are meant to be held in place by a central groove which is located by the metal spring which holds the pads in place - I had a case of this pin coming out - literally - and the pads moving.

Abbey Motorsport have developed modified pins held in place by circlips and I would recommend this mod.

Spec K

 

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On 31/10/2016 at 5:22 AM, Special K said:

I had a number of issues with K-Sports, probably the most noticeable was the amount of pedal pressure required. They also got very hot

But Stoptechs also have an issue with the rear caliper pad retaining pins. These are meant to be held in place by a central groove which is located by the metal spring which holds the pads in place - I had a case of this pin coming out - literally - and the pads moving.

Abbey Motorsport have developed modified pins held in place by circlips and I would recommend this mod.

Spec K

 

That's interesting, thanks. I hadn't come across this when researching the Stoptechs - most people tend to swear by them. And the AP ones for that matter.

The Stoptechs would necessitate either some spacers or new wheels. I could get the Stoptechs and some fox fx005s for the price of the APs. Which would save a good amount of unsprung weight, but I'm not really a fan of the look (of aftermarket wheels).

The APs increase the front braking bias, whereas the Stoptechs do not. Having a big lump of a supercharger on the front has already moved the brake bias rearwards slightly from stock (by how much I have no idea) so the APs would compensate for this, but probably overcompensate moving the bias forward further.

I spoke to someone technical at AP racing yesterday who said they ensure all of their front road kits keep below 18% extra braking tourqe vs stock so as not to mess with the balance too much or upset ABS. They have tested this kit with with the stock 86 rear brake set up and were fine, but did recommend a DS2500 pad on the rear. He also said they had worked very hard to get this to fit under the stock wheel!

Anyone had problems with too much front bias?

 

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Did you speak to Pete Collen? 

The 332mm AP kit for the gt86 is almost exactly the same as the stock bias. My spreadsheet puts them at about 70% to the front.

Happy to send you the spreadsheet if you want to use it for other brake kits. You need to put in the piston diameters, disc diameter and pad swept area to compare to stock. 

 

 

 

 

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Under 18% bias change vs stock bias? "recommend use different brake pads in rear"?

These both bits would tell me to stay away from these kits, as i translate them that brake vendor haven't bothered about brake bias or has targeted with kit some very specific suspension & aero setup. Essex's Sprint & Endurance kits were within 1-2% from stock bias, other kits like willwood/RR and so on IIRC within 5%, and that's with same compound pads front-rear.

P.S.

Easier to loose traction with power-oversteer after installing forced induction has nothing to do with brake bias. FI doesn't impact it in anyway. Suspension parts, adjustments and front-rear downforce from aero parts does (striking out weird possibilities like staggered tire choice and front:rear weight balance, which i doubt to change noticeably from weight of FI parts).

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9 minutes ago, Church said:

Under 18% bias change vs stock bias? "recommend use different brake pads in rear"?

These both bits would tell me to stay away from these kits, as i translate them that brake vendor haven't bothered about brake bias or has targeted with kit some very specific suspension & aero setup. Essex's Sprint & Endurance kits were within 1-2% from stock bias, other kits like willwood/RR and so on IIRC within 5%, and that's with same compound pads front-rear.

P.S.

Easier to loose traction with power-oversteer after installing forced induction has nothing to do with brake bias. FI doesn't impact it in anyway. Suspension parts, adjustments and front-rear downforce from aero parts does (striking out weird possibilities like staggered tire choice and front:rear weight balance, which i doubt to change noticeably from weight of FI parts).

Sorry if my post wasn't clear. I think what he was saying that none of their road kits have more than 18% more braking power than the stock equivalents but I don't think this translates into an 18% shift in the brake bias, and for this kit apparently there is no change in bias.

Extra weight on the front (e.g. A supercharger) moves the bias towards the rear because, if all else remains equal, there is less braking power on the front vs the weight over it and the extra grip it can get.

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That weight is too small to be taken into account. How much SC weights? How much car weights? How big difference can be felt by human "butt dyno" (placebo aside)? I doubt you feel difference in weight shift of car vs full or almost empty tank, even though that weight difference is 3 times SC weight.

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It might well be imagined, but turning in to tight corners quickly is where I feel I notice the extra weight (20-30kg I believe, which is comparable to a tank of fuel) of the Harrop. One of my mates who'd seen the car before and after asked me if I'd had it lowered! Obviously the car is much faster than it was before though and I'm very happy with the kit, but just saying.

Anyway, I went with the AP racing 332mm kit. Very excited to get it on and get the car on track in the new year. I'll probably avoid doing any other significant mods for a while. This thing is fast enough and now should have the braking performance to match. Time to leave things be.

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1 hour ago, Bfranklyn86 said:

It might well be imagined, but turning in to tight corners quickly is where I feel I notice the extra weight (20-30kg I believe, which is comparable to a tank of fuel) of the Harrop. One of my mates who'd seen the car before and after asked me if I'd had it lowered! Obviously the car is much faster than it was before though and I'm very happy with the kit, but just saying.

Anyway, I went with the AP racing 332mm kit. Very excited to get it on and get the car on track in the new year. I'll probably avoid doing any other significant mods for a while. This thing is fast enough and now should have the braking performance to match. Time to leave things be.

Excellent Choice! :)

What pads did you order with it? 

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Wheel clearance is specific to brake kit and to specific wheel (of specific sizing) kombo. Check info on vendor's site or via email enquiry. Also you can search on brake vendor's site for brake fitment template, download that pdf, print, glue on carton & cut by contours, and then check on your wheels. Also you may try to search on forums, if someone by chance has specific brake kit and specific wheels. Sometimes some not-clearing brakes cases can be workarounded by using wheel spacers.

Specific wheel size of diameter/width/offset alone is not enough to ensure fitment, just increases chances to fit. After all, it may depend also on spoke shape, and that shape may differ between different wheel types and between different widths/offsets of specific wheel (like with offsets such and such it's one "face" of wheels of specific concavity, and for other offsets - different "face").

Increased braking power .. sounds like you are under impression of some populistic myths. Stopping distances mostly depend from tire grip only. If "less powerful" [tm] brakes are still capable to brake till wheels are locked/ABS triggered, car will not stop sooner. At most only brake pedal travel may differ. Main thing that "big brake kits" offer - increased heat capacity. They can "store" more heat and cool off at faster rate, resulting in longer heavy braking time before some issues pop up from overheat (eg. brake fluid boiling, brake pads overcooked/glazed and such, resulting in "brake fade"), thus eg. longer tracking sessions with rest being same, or eg. still acceptable brake functioning time even if you have to brake more (from eg. higher speeds due forced induction, or from higher speeds reached due grippier tires/more aero downforce mods). Nothing suspension related.

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4 hours ago, Darth Raknoor said:

Random questions about the AP's.... Would the increased braking power require a change of suspension and would they fit behind a set of Work S1R's sized 17x7.5 et35?

A church said, you do not require to change suspension to use a BBK however, if with you current choice of tyres you can lock the wheels its pointless fitting a BBK. If however your using stickier rubber and you cannot lock the brakes with them then a BBK will give you increased performance.

 

For reference have the Rayland 330mm kit:

http://www.reyland.co.uk/subaru-impreza/

 

It fits under my Rota Boost, 17x17.5 E48 with a 15mm spacer. It also fits under my XXR 527 18x8.75 E35.

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A church said, you do not require to change suspension to use a BBK however, if with you current choice of tyres you can lock the wheels its pointless fitting a BBK. If however your using stickier rubber and you cannot lock the brakes with them then a BBK will give you increased performance.
 
For reference have the Rayland 330mm kit:
http://www.reyland.co.uk/subaru-impreza/
 
It fits under my Rota Boost, 17x17.5 E48 with a 15mm spacer. It also fits under my XXR 527 18x8.75 E35.
Heat management is the main reason for bbk not braking force?

Sent from my COL-L29 using Tapatalk

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1 hour ago, sam534 said:

Heat management is the main reason for bbk not braking force?
 

Yup. Stock brakes can lock your tires already, so you literally cant gain from more braking force.

However, give it 15 or so 60to10mph hard brakes, and suddenly your stock system isnt stopping you as well as the brakes are fading.

BBK will take longer to start that fading process.

NB - Its also for looks.

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