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Author: Subject:  Braking & Gearing questions
MemberJak Rizzo
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posted on May 26th, 2015 at 01:28 PM
Braking & Gearing questions


Run last Saturday at Eastern Creek & within 2 laps had run out of brakes. Had new rotors & pads, fresh dot4 brake fluid, bled quite a few times leading up to the event, but with the high braking corners like the hairpin at the bottom of the hill & the left hander at the bottom of the other hill (hairpin in the long track) it just couldn't handle it. For example when I had cars 10 car lengths behind me , they could pull this gap back under brakes as I had to take it so easy. I bled the brakes after the first session, got no air out of them & they felt no better on the second session so I decided not to keep going.

I run Porsche turbo rotors with Nissan GTR calipers with EBC red pads on the front, Ford falcon rear disks & calipers with standard pads in the rear. All rotors are slotted & dimpled, fronts are also ventilated. All rubber lines have been changed to braided as well. Had this setup for some time now & never really had any dramas, but only ever raced on the Eastern Creek long circuit or Wakefield where high braking forces/corners aren't in quick succession. So now I think it may time to ditch the standard 19mm MC & go to a kombi 24mm MC. Any thoughts on this? did anyone else have brake problems?

Gearing. I did the whole track in 3rd gear, 2nd was too short for the left hand hairpin so I just left it in 3rd & dealt with it bogging down a little. I have always wanted to put a taller 1st & 2nd, this may now prompt me to do so. I currently run superbug 3.78, 2.06, 1.26 & kombi 0.82 4th with a 3.88RP
albins have a 3.0 1st & I will have to get a custom 2nd, but what ratio, currently at 6000rpm my car does 80kph in 2nd, so would it be better if it did 100kph in 2nd at 6000rpm to pull better out of corners rather than leaving it in 3rd. maybe a 1.8 2nd? Car is also a daily driver so it needs to be still tractable at low rpm as well.

Was anyone else leaving it in 3rd as well?

Any thoughts?
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posted on May 26th, 2015 at 05:59 PM



slow down?
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posted on May 26th, 2015 at 06:05 PM



Jack,
I find it,s allways better to change up a gear than hold the car at high rpm, because the max torque will be lower rpm than max hp.
What about a 4.11 r&p?
Can,t help much with brakes, hillclimbers don,t experience high brake temps.

Cheers Col
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posted on May 26th, 2015 at 07:11 PM



Hi Jak,

Given it was my first time on track I was working on my braking confidence, but could have pushed them more. I have a Boxster/911 combo up front and falcon at the back with standard mc. Due to air cooled engine and talent deficiency my times were also 7/8 seconds slower from memory so my velocity at those braking zones was probably significantly less than yours. I didn't have any fade or noticeable smell at the end of each run.

I have a standard L Bug box and by the end was changing into fourth going over the first hill and then down what might constitute the back straight (hence I probably also had engine braking going into the left hand as I went back to third). The rest of the time was third. I did try second in the downhill hairpin twice but I think I lost time so stayed in third thereafter. It was slightly boggy picking up from third which I tried to fix by going in faster at which point I ran out of talent and had a moment (or two when I tried it again)




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posted on May 26th, 2015 at 07:24 PM



Just saw the results. Make that 9 seconds or 12.5% slower! Certainly enough to fundamentally alter the ability of the brakes to cope.



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posted on May 26th, 2015 at 07:42 PM



Did you 'heat-cycle' the pads, and bed the new rotors in, Jak ?...you may have to 'up-grade' to drums. :smilegrin:

I was in 3rd most of the time, with 2 short 'engine saving' moments in 4th.




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posted on May 26th, 2015 at 09:25 PM



Hi Jak

On my sons bug Im running early Type 3 fronts with solid stock rotors and 944 rears with the factory vented rotor, with 911 twin piston Brembos and EBC greens all round.

I had no braking issues at all.

Its running the original L bug box, I went back to 2nd on the apex of T11 which gave me a really nice slingshot out of T12, I used 3rd the rest of the track.

As Greg said did you manage to bed the brakes in correctly?

Steve

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posted on May 27th, 2015 at 06:20 AM



maybe look into getting some ducting on the front brakes.



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posted on May 27th, 2015 at 06:57 AM



Quote:
Originally posted by HappyDaze
Did you 'heat-cycle' the pads, and bed the new rotors in, Jak ?.


Admittedly I did only get the new brakes & wheels/tyres on the car Friday morning, but I did go out & spend some time driving around a lot of the country side I have near me & bed the brakes in, I also had the whole M1 to myself driving down Saturday morning so I used some of the bigger hills to bedding in as well. I did think this may have been the problem, but still now after they have had a track day I still have a spongy pedal, not as bad as at the track though. I also bled the brakes when I got home again, just to be sure, still got no air out. very disappointing as during my second run I was counting down the time at turn 11 & turn 15 that cars from behind were catching me , it was about 2 seconds on both those corners, from there on I could hold the gap from them so it was a little frustrating. Still had a fantastic day though. It was worth coming just to see that Porsche truck!

I was pulling 6500rpm in third up to turn 6 which is 158kph, this seemed enough to keep up with the other cars in my group, even through 7 8 & 9 the car felt sweet, handling & tyres seemed very very reassuring. just the stopping was the problem.

I can't get rid of the 3.88 RP Col, I need the long legs for the freeway as the car is primarily a daily driver.

Do any of you use a bigger MC? I'm thinking this should be my first change?

Oh & what brake fluid are you all using? I use the Castrol DOT4 in the gold bottle
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posted on May 27th, 2015 at 08:07 AM



Hi Jak

I use Nulon in everything on all our cars including brake fluid. On my sons car Im running a stock m/c but on my car I went to a CSP 20.64 for a firmer pedal http://csplink.de/R2ni55zhBj  & http://csplink.de/TQWB7UOzQX 

Steve
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posted on May 27th, 2015 at 08:33 AM



Thanks Steve, does that 1mm or so larger really make a difference? You have even bigger pistons tham me to move I think.

I was thinking a 22mm Kombi MC, or even the 24mm version?
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posted on May 27th, 2015 at 10:30 AM



Going up one size of master is all you'll need. I made the mistake of going to big once and wore out my left by the end of a track day. But it sounds like there is another problem. The master is only going to make your pedal harder. Even if the pedal is a bit soft with the small master it should pull up fine. Do air come out when you rebleed them? If so maybe is somewhere it's sucking air.
3.0 1st gear and 1.8 2nd would be great. At least you'll have a usable 1st gear then with the 3.88. That's the same combo I have in my green car.
Cheers Adam
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posted on May 27th, 2015 at 10:39 AM



Thanks for your imput Adam, yes I have bled the brakes quite a few times now & still no air. The car was still pulling up, but as I'm so used to a high firm pedal it was a very disconcerting feeling, particularly at speed on the track

I have the car up in the air at the moment with the wheels off as my street tyres are going back on so I might give them another bleed just to make sure
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posted on May 27th, 2015 at 11:27 PM



Hey Jak if your master cylinder has done as many k's as your motor it is probably time for a new one!
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posted on May 28th, 2015 at 06:08 AM



LOL! so true Paul, I never thought of that!
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posted on May 28th, 2015 at 05:21 PM



time for a subaru gear box...I wish I had this option 15 years ago when I was circuit racing the beetle:tu::tu:
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posted on May 28th, 2015 at 07:54 PM



x2
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posted on May 29th, 2015 at 06:46 PM



Hi Jack Great to catch up on saturday what a great event. In regards to your brake issues aprocedure you might might want to try is by isolating one brake circuit and seeing how it affects pedal firmness. This is easy if you have rubber brake hoses, if you have braided lines they need to be plugged regards John L.
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posted on May 29th, 2015 at 09:20 PM



Sounds like a pads issue. With the size of the disks and rotors you have, braking power should not be an issue. I had a similar prob with one of my datto rally cars many years ago. Standard brake pads just will not cut it on that track. Esp on the back.1 really good stop, 2 if your lucky before you loose ability to stop. There is a lot of weight in the rear with a subi donk. I use and like the 3.0 1st and 1.9 2nd. issue for you is your car is your street/family car that gets driven every day and raced only a few times a yr. Tall 1st and 2nd gears are a pain in a loaded up car on a hill in heavy traffic. Hav a look at Subi ratios and go from there. late 90s and sti rexs ran a very similar ratios however with 4.4 diff. If you really want to change your ratios, stick with what the factory have spent many hrs and $$$ on trying to get right for the eng you are running.



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posted on May 30th, 2015 at 06:46 AM



Hi john, hopefully I now have the race bug again so we can do some more track days together.

Bat69, I agree about the rear pads & will change them to match the fronts. As for the soft pedal, I think I may have worked out the problem, my father aka the Maltese MacGyver is machining me up some parts now. I'll let you know how it goes.

With the ratios my 3.78 & 2.06 are gone in a flash, I can actually very easily start in second gear it's that low, my mate CT has 3.0 & 2.0 in his & it's not that noticeable, being taller that is, but his car is 250kg lighter than mine as well.
I did look into the Subaru gears & they are short like the mine currently, but the WRX on average is 500kg heavier than my car as well so I thought I could get away with the tall second
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posted on June 1st, 2015 at 07:22 PM



brake later but harder less time on the pedal the better cheers Rudi
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posted on June 12th, 2015 at 07:23 PM



lmfho...
hey Jak, I was disappointed I couldn't make it this year. man, you don't need a bigger master cylinder you need bigger cojones......:lol::lol::lol::lol::lol: (just kidding -i know you go hard.)

I am running type 3 calipers on the front with Sherman drilled discs and type 3 wagon drums on the back....... pulling up from 220kph into southern loop at lakeside after 6 laps is really scary!!

I think Rudy said it once before in an old post, "the more you use your brakes the slower you go"......




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posted on June 17th, 2015 at 06:08 PM



Whats the reason you'd stick with a bug gearbox opposed to going subaru? Just the cost or you like just 4 gears?

Just asking because im tossing up between the 2.
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posted on July 2nd, 2015 at 01:40 PM



Just installed a CSP 20.6mm master cylinder & wow! what a difference, nice high hard pedal. Thanks Steve

Also have EBC red pads to put on the rear as well, then hopefully get back to Eastern Creek

Thanks for all the replies
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posted on July 2nd, 2015 at 05:10 PM



happy for you Jak, all the pain was worth it


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