G4 8 piston brake review

Discussion in 'Technical' started by Blipman, May 23, 2007.

  1. Blipman

    Blipman Beer hooves totally work

    This is something I wrote for Skylines Australia but I've had some Z people also ask me about this product so here is a copy and paste of the post. This is obviously for these brakes on my Skyline, but this IS Z related as the brakes are very similar for the two cars, and I'm sure there will be some Z owners also interested in this, so there :)

    This is intended to be a reasonably diffinitive review of the G4 Racing 8 piston front brake kit as to date I'm yet to find one, so that people in future can make an educated decision when buying these.

    I've seen quite a few people who are interested in these brakes for track use but given the very cheap price and no name brand status everyone seems to be tentative about buying them. Like others I tried to do a bit of research online and hear people's opinions, but was only able to find one instance of someone using them on the track and although there wasn't a lot of detail, their feedback was positive.

    With so many people wanting to know what these brake kits are like I thought I'd take the leap, be the guinea pig and let people know what I think, I suspect there are a few people out there ready to go with these brakes if they just had a bit more info on how they perform.

    Prior to purchase I was pretty skeptical as I have bought parts manufactured in China (these brakes are made in Taiwan, to be precise) that were pretty disappointing and made to meet a certain cost rather than quality, but at the same time brakes are in reality pretty simple (I'd guess it's the quality of casting and metals that make the biggest difference for the hardware) so it's not impossible for a no name brand set to be good. Being 8 piston also concerned me that they were more show than go (well, stop), but with 2 piece disks, bigger diameter and slightly bigger pad the physics at least says there should be some sort of improvement.

    The car
    For people to compare, the car these are going onto is a 1993 Skyline GTS25t, weight is around 1400kg or so and at 250rwkW it's no slouch. On the track I will be running R-comp semi slicks, I would rank my abilities pretty much at novice so I'm probably someone who brakes earlier than absolutely necessary, and from lower speeds.... in theory I won't be hurting them quite as much as a better skilled driver. I'm also not running any ducting at the moment, though this may change in future.

    Those who know me will know that I work for J-Spec Imports but I'm just writing this in my capacity as a car enthusiast, I have no vested interest here nor do I have any bias one way or another with Just Jap... just trying to help out the community.

    The brakes
    The G4 brakes are sold under a few different brand names, as well as G4 (in blue) they are sold as D2 (in purple/pink) and possibly other brands. From what I understand the only difference between these is the colour and therefore the info in here on the G4 kit should be applicable to say a D2 kit. I chose to go with the G4's from Just Jap as they were helpful on the phone and were able to give me a bit of info about others who have used these brakes, and I've had good expreriences with them in the past. While I woulnd't hold them to it, I told Just Jap I wanted these in a hurry and they arrived the next day... not too shabby.

    The only real variation in kits for the front is that you can go for either a 330mm or 356mm kit. For around $300 difference in price I'd say the 356mm kit is well worth it, however this does need 18" wheels to fit, wihle the 330mm kit only requires 17's.

    The kit
    I don't know what I was expecting but I was fairly impressed with everything the kit came with. Although I didn't use them there were some brackets to mount the brake lines and some other extra parts which in reality they didn't have to include but do give you more options for mounting. It came with everything right down to washers and the like, so I didn't have to dig around for extra parts to get it all to work.

    The instructions are in dubious English to say the least and a lot of it is the usual legals and warnings that have little relevance to real life, I read through it all but didn't really need it. I was happy to see that it did have torque values for various bolts.






    I found installation pretty straight forward (brakes aren't really rocket science) and the whole job was done on a hoist in around 3 and a half hours, you could do it on the ground without too much hassle. However, the only complaint I have (and this at least doubled how long the install took) was that the brake lines were too long. Although they come with brackets to help you locate them, being too long meant it was quite difficult to avoid them interfering with the wheels at full lock. After a lot of stuffing around I eventually came to a solution which I'm only partially happy with, had the lines been a little shorter this would have been much easier. I've heard others also make this complaint.

    This is comparison with a 1993 Nissan Skyline R33 GTS25t:

    Standard disk diameter: 297mm
    G4 disk diameter: 356mm

    Standard max disk width: 32mm
    G4 max disk width: 30mm

    Standard min disk width: 28mm
    G4 min disk width: 30.5mm

    G4 pads have a 12% bigger surface area than standard R33 pads.

    I didn't weigh things, but being aluminium calipers the G4 units were lighter than standard. The bigger disks will weigh more but this is offset by being 2 piece, so overall I don't know the difference but I don't think it's significant one way or the other.

    Here are some photos showing comparisons.







    Yes I know one of the parts is missing from this photo


    Impression - street
    Right, down to the actual important bit. Note that this is in comparison to standard R33 GTS25t brakes which in fact are pretty decent to start off with (and I had Endless pads as well), on a car with poorer brakes to start off with the difference might be greater. On the street the difference isn't that great for normal driving. The pedal is slightly harder and under moderate braking you feel slightly more confident, however the difference isn't massive. You could have put these onto my car without me knowing and I wouldn't have picked it immediately, I think for regular driving you could get just as good a result from a good standard size disk and pad combo. Under hard driving on the street you feel a bit more confident but in reality you are traction limited long before the brakes run into problems even with a quality standard sized setup, so it's not really possible to experience anything extra the G4 kit might give you.

    I've found that the pads which came with the kit are a bit on the dusty side also, in about 3 days of driving I've got more dust than I did from my old Endless pads in 3 months of driving, on the track they are very dusty (I have white wheels!) I occassionally get a slight squeal at low speeds but overall I wouldn't say that the are particularly noisy.

    Replacement parts
    The pads seem to be a fairly common size and there are many brands out there that you can get if you don't like those with the kit or want to buy replacements elsewhere.... a friend showed my some spare EBC pads for his AP 6 piston kit and they looked identical, for example. Likewise for the disk, this is probably also a common size and a race brake specialist may be able to find the same size disk in other brands, but you'd need to do some research first as that's just my guess.

    On the track
    The debut for the brakes (and speed event debut for the car) was Phillip Island, overall I was happy. The brakes stood up to everything I threw at them with no fade (I'm using the 'street' pads) and they stopped hard fairly consistently. The only complaint I have is that when both cold or hot I don't find the initial bite of the pads to be that good (I think this is also why they aren't that impressive on the street), and a different pad would probably improve this.

    I did 4 sessions with 3 hot laps and was doing sub 2 minute laps which is respectable, however ultimately I wouldn't say the brakes were given that much of a hard time as 3 hot laps is not a lot per go, and Phillip Island is probably the easiest track on brakes of all in Victoria, there's only really one hard stop from high speed to low speed.


    After the brakes performed well at the track I was pretty happy. On the way home from the track the next day things turned for the worse. While cruising at 100kph there was a sudden knock and then very loud grinding combined with quite serious banging. I pulled over and stopped the car gently and looked at the front right where the problem obviously was. With the wheel off on the side of the road it was obvious what the issue was, one of the bolts which holds the caliper and bracket to the car was gone! My first suspicion was that the bolt sheared off however there was nothing there in the thread, it was completely missing. This is highly dangerous to say the least, there are only 2 bolts in total which hold the caliper on. The initial obvious conclusion is that I had failed to tighten the bolt correctly, however I do recall tightening this upon installation, and because I know that brakes are your life on the race track, I also tightened all 8 bolts that hold the brakes on AGAIN before putting the wheels back on.

    So I was stuck on the highway between Philip Island and Melbourne on Easter weekend (you can imagine how busy it was) with the sun going down and over 2 hours from home. A very good friend came and had a look at what the bolt size is, went and got the right bolts from home (no place would be open for 2 more days given the long weekend) and drove back, you certainly know who your friends are at times like these. When we went to put the bolts back on to attach the caliper and bracket again we found we couldn't get the second bolt to line up through the hub and into the bracket threads no matter how hard we tried and in our efforts damaged the thread in the bracket pretty badly.

    It ultimately turned out (it's now night time on the side of a busy highway so visibility with a torch is poor) that the holes in the bracket didn't properly line up with the hub holes... they were out by about 1 - 2mm, and these clearly ligned up previously when I installed the brakes. From here I have a *theory* as to what the problem was. I think the bracket material is not quite right and was warped or expanded due to heat, and this is why the bracket no longer fits properly when before it did. This expansion also made the threaded bolt hole bigger (I know it sounds counter intuitive, but bolt holes get BIGGER when metal expands) which caused them to loosen and the bolts over time work themselves out which caused my problem. After repairing the brakes I checked the other side to be safe and indeed one of those bolts was also loose, I think this also backs up the theory that it wasn't installation error... to miss tightening BOTH sides is really unlikely. The holes in the hub also had gouges in them from the thread of the bolts which must have been exerting a lot of force on them.

    After elongating the holes in the hub with a file (really strong metal as you can imagine) we were finally able to get the bolt to go in. Although tight, one of the threads is ruined in the bracket and while it was good to get me home once I pull it off I won't be able to use that bracket again, and adding to the frustration with the elongated holes if I ever want to fit standard brakes again or a new bracket I may have to replace the hub :( The caliper has been pretty scraped up and deep scratches have been gouged into the inside of the wheel, and this event also knocked off the wheel weights so I had to drive home on an unbalanced wheel with a bit of vibration, so I hope my brand new expensive semi slick isn't ruined. All in all, not much fun. Had this happened at high speed I don't think you'd consider it to be too good either. Justjap says I'm the first person to experience this problem.

    Just great....



    With the exception of the brackets being warped/expanded and possibly not being possible to put them on again once removed, I think this problem can be avoided in future by using a nut and bolt rather than just a bolt going into the threaded bracket. On my car with the 356mm disks at least there is the room for this, and with the right bolt, a spring washer and lock tighted nut on the other end there is no way it could come undone with expansion or warping of the bracket. This is how AP and other non OEM brake kits with an adaptor attach the bracket to the hub. I also found that the washer for these bolts was very bent and think that it was probably pretty useless, this washer provided with the kit really should be a much stronger grade.

    Conclusion from all this:
    I think when installing the kit you should lose the standard bolts that attach the adaptor to the hub and use a nut and bolt combination combined with a spring washer, and obviously some locktite as well. If the adaptor is expanding at different rates to other components this should not come loose, and if the nut somehow still did manage to come off, the caliper could move from side to side slightly but could not come off as happened to me as the long nuts are not through the hub holes, so there's an extra failsafe there. I'd also recommend using thicker washers than those provided with the kit.

    Non G4 brake pads
    Justjap have informed me of another issue they found with their Targa Tasmania car. Apparently the G4 pad size is very slightly different from the other brand pads that will fit with this kit. The G4 pad is a few mm smaller at the part which clamps to the outside of the disk, so when using non G4 pads they found that a small lip was forming on the pad where it went past the disk, this in turn got hot on the outside edge of the disk and the heat cracked the disk. They suggested using either the G4 brand pad only, or taking a mm or so out of the top edge of the pads you install (or bevelling the edge at least).

    Track day number 2:
    Last week I went to Sandown which is a little harder on brakes. 5 sessions of 3 hot laps all up, brakes felt good again, towards the end of some sessions I found the pedal getting a bit spongy but the car still pulled up fine.... had I been doing longer sessions they might have started to drop in performance. High speed stops (from 200ish) as you'd expect were a lot better than the standard brakes.

    A friend had a laser thermometer there, for comparison here are the brake disk temps with similar weight, power and lap time cars (another R33 and an R34). This is after a cooldown lap and dawdling into the garage so they will have cooled a bit.

    My R33
    G4 brakes (356mm disk, G4 'street' pads): 130 degrees
    Standard rear brakes (Nissan OEM pad) 280 degrees

    Another R33
    F40 Brembo brakes (340mm disk, Ferrodo 2500 or 3000 pads): 300 degrees
    Standard rear brakes (pad unknown): 150 degrees

    R34 GT-T
    CSC brakes (343mm disk, Ferrodo 2500 or 3000 pads): 150 degrees
    Standard rear brakes (pad unknown) 80 degrees

    I'll keep people posted on how things go as I do some more track days, so far (issues aside) I am reasonably happy with the kit, it still remains to be seen how they go if you REALLY give them a hard time, so far this is a moderately light, moderately powerful car which hasn't seen a hard braking track yet or very long sessions... 3 hot laps is very little.

    I hope this rather long read helps people make a decision, I know a few people were waiting for a bit of feedback before going ahead with these, if this assists with that I'm glad I could help.... I wish someone had done so before I decided to take the leap :)

  2. JEDI-77

    JEDI-77 Jedi Master


    just curious, but did just jap offer any form of compensation for what happened to you?? I'm assuming thats who you bought the brake kit from?

  3. 260DET

    260DET Active Member

    Great Feedback

    Thats a very well written and comprehensive report.
  4. akeizm

    akeizm New Member

    I know this probably wont have helped if the hole expanded. But did you apply Locktite to the bolts? I know in the FSM on the 300 it says to use some.

    But I agree with 260DET, great review...also how much was the kit compaired to other kits on the market.
  5. maTTz

    maTTz 500 Club

    brakes and rubber save lives

    sell your life to the lowest bidder? nope :)

    a classic example, your caliper bracket undid itself and your caliper nearly fell off - if it did it would have snapped off the brake hose, you would have lost your front brake fluid, and would have been trying to stop in a potential emergency situation with your rear brakes
  6. Vincent

    Vincent New Member

    Good write up. Stops me buying G4s for my beast.

    Now if I could only convince you to buy a set or APs and test them I'd be REALLY happy!

  7. vbevan

    vbevan Active Member

    Good review. For future reference for myself, could you just aligning to hole up and find something to hold it there (heck a bit of string even) and just driven home very carefully using the handbrake only? Or else removed that caliper, block off the hose and drive home on three brakes?

    Given you had the tools (as most people have a tool set but not spare bolts), would this have been an option?
  8. K-zed

    K-zed Secret Squirrel

    Added to Tech A-Z/Brakes :)
  9. Blipman

    Blipman Beer hooves totally work

    No they didn't

    I obviously let them know about the incident and we talked a bit on the phone, I dropped a few hints that it would be nice since I had stuffed the thread on one of the adaptors (not that it's now needed with the fix) but they didn't offer to replace it, and I couldn't be stuffed fighting for it since it wasn't totally necessary. It would have been nice if they'd shown a bit more concern, but I'm pretty easy going and didn't push the point.

    This kit was around $2,500 with the 356mm disks, for a similar spec kit (say similar disk size and 6 piston calipers) from a name brand will be around $4,500 and up. I used a small amount of locktite on the bolts.

    vbevan: I really wouldn't want to try that, in an emergency stop brakes can save your life, I wouldn't want them held on by string!

  10. maTTz

    maTTz 500 Club

    lol string holding your caliper on :) imagine if a cop saw that! it'd be his personal life mission hunting down import cars and yellow stickering them... maybe that's why we get targetted?
  11. vbevan

    vbevan Active Member

    Hehe, i just meant to get you home. So you drive like a grandma giving everyone heaps of room in front of you and only braking with the handbrake. Of course it's nice if you have someone to help out but if this happened at say midnight, might not be so fortunate.
  12. akeizm

    akeizm New Member

    So basically, they're alright for the price of them. But the caliper bracket has issues and should be fastened by nut and bolt, or get a new bracket machine up locally.
  13. RedZedMikey

    RedZedMikey RZM should now be DZM

    Good write-up Ben, though it will be a while before i go to the next step after Caz's GT-R upgrade. I'm intrigued with your temperatures - how come your rear brake temps were 150 degrees hotter than the fronts??? Have you got the figures round the wrong way? Both the other cars temp tested had significantly cooler rear brakes. Where was the laser temp targetting? Rotor surface?
  14. WhiteNight

    WhiteNight Littering and...

    i think veeban ment to wire lock the bolt in place so it cant twist on itself
  15. dattoman

    dattoman Learner

    What are the piston sizes in the calipers ?
    They look alittle small to me

    Do you find you need more pedal pressure to make them stop as well as the standard brakes ?
  16. WYKKED

    WYKKED <b><font color=red>2 Much Trouble</font></b>

    Nice writeup Ben. I should still have the AP installation instructions if you want to put together a more comprehensive article on your fix.

    Vincent, I have the AP 6 piston kit if you want to have a closer look at one before you commit to the purchase.
  17. Chrispy

    Chrispy Pretentious Upstart

    One of my mates dads is a cop and he pulled over a 4X4 Hilux that had his steering tie rods attached to the hubs with zip ties :eek: :eek: True story, had to get the car towed home :p
  18. ZX2NV

    ZX2NV Z Racing Evolution

    I was at Autosalon Circuit Battle today adn this beautiful BMW M3 with carbon fibre roof and bonnet nice big wide M3 wheels, full race seats etc etc and G4 Brakes on the front. Yep you read it right G4's on a 80k beamer WTF he seemed to like them though.
  19. Blipman

    Blipman Beer hooves totally work

    Yeah that's the short version basically :) A bolt, nut and spring washer to attach the adaptor instead of the bolts that come with it should be a good solution.

  20. Blipman

    Blipman Beer hooves totally work

    Temps are around the right way, I too was pretty surprised that the rears were hotter. The only things I can think of is that the pads are of a different compound (the rears are Nissan OEM pads that were left on after compliance, I actually have 2 other aftermarket sets for the rear that I should get around to installing) and that the temperature was taken after a cool down and maybe the one piece disks held their heat for longer.


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