G4 / D2 8 Piston Brakes - The Diffinitive Review

[Blipman]

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.

Preamble

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.

Installation

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.

Comparison

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.

Problems!

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).

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

[Blipman]

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

[B-Man]

Good write up - thanks

[ferni]

nice write up, thanks for taking the time to do that dude.

[tacker]

Just a little info,

i have just used the G4 track pad ( bright green ) and found it to be a lot less dusty than the street pad. i got through the street pads ( wasnt sure what they were to start with ) in about 800 kms of track work. The new green pads are lasting much better 500kms of track work and not much wear just yet.

But in saying that you will find higher temps on the rotors with these pads. Almost no difference to the DS 3000 compound i thought. You will need to duct some air to the discs to help with cooling. I also found that my rear discs were a lot higher temp than the front so i improved the ducting to the rears just in case.

I found the same with the brake lines just a bit to long.

I have just recently removed my brackets to install some new items as i am told that there was a clearence issue with the lower control arm and the rotor. I did not have to use the old item again so i amnot sure about if the problem you had happened to me when i re installed them, but all 4 mounting bolts were still tight when i removed them

[Roy]

Champion write up Ben.

[Blitz]

What an amazing write up - Excellent work Great to see some reviews from real-world use!

[Al]

Awesome reveiw Ben

[Kaido_RR]

awesome write up

So the issue you had? is this a manufacturing fault ? or just a one off problem?

[Ronin 09]

top stuff mate

[Benno31]

Excellent write up, thank you for taking the time to do it.

I am curious as to why your rear brake temps were so high, its almost like the spongy brake pedal was your fronts not working like they should which shifted load to the rears causing the higher rear brake temps on your car. Did you happen to notice if the other comparison cars had better cooling to their rear brakes?

Any braking experts on here care to comment on this?

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

[djr81]

I cannot be 100% certain from the photos, so I cannot be 100% sure about this but:

It is VERY POOR practice to use bolts to connect to blind, tapped threads. What should be done is that a stud bolts (Think threaded rod) be used & it be loctited in place. Only then should the nut be torqued up to the outside of the stud.

What typically happens is that if you try to use a bolt you either don't get enough tension on the one or other of the bracket or the hub. The result? The things rattles loose....

The problem is that you either don't get to use the full depth of the tapped hole or you don't get sufficient clamping force on the caliper.

Edited May 3, 2007 by djr81

[djr81]

Excellent write up, thank you for taking the time to do it.

I am curious as to why your rear brake temps were so high, its almost like the spongy brake pedal was your fronts not working like they should which shifted load to the rears causing the higher rear brake temps on your car. Did you happen to notice if the other comparison cars had better cooling to their rear brakes?

Any braking experts on here care to comment on this?

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

Simple: Different brake bias causing different temperatures. Also those temps aren;t that high (Rotors get much higher than that) hence you have to factor in different cooling rates.

[phunky_monkey]

Awesome write up, thanks a lot for doing that!

[Blipman]

djr81: I'm not sure I quite follow what you're saying.

This picture is showing the bolts that come with the kit. These go through the unthreaded hub and into the threaded caliper adaptor. These are the bolts which worked themselves loose.

What I am doing now (which I don't have a picture of) is to have a long threaded bolt going through the adaptor first (so the opposite direction to those in the photo), they then go through the unthreaded holes in the hub and there is then a spring washer and nut put onto that bolt which would be where you see the old bolt heads in the pic above. Does that make sense?

mrbenno: I think the high rear temps are just due to a different pad being used as i would imagine that plays a pretty big role. The car had the Nissan OEM pads on the rear which were left on the car after compliance, track work is probably a bit much for them.

Michael: I don't know if it was a problem with the design of the kit or a one off problem, I'm apparently the first to experience with it. If you use the solution I've mentioned above then you shouldn't have it happen again.

[tacker]

Blipman,

Great write up if i didnt mention that before. Have been thinking about your thoughts and actions with regards to the longer bolts and i think i am going to do the same as you as it seems to be a very sound idea.

I really pushed my set of G4's last weekend I had a set of old slicks (Michelin S8B 240 x 640 x 18 ) on that were on their last run due to the wear indicators just about being worn away. I found with both the DS 3000 and the track ( green ) pads i could lock the front wheels if i really push the braking to the last possible moment and then apply the brakes as hard as i dared too. We have some big stops on the track we run here as well, 240kph plus twice and a third about 200kph each lap (dubai autodrome ) this in a 400+ AWHP GTR which i have stripped out to just about all i can so i am not sure what weight that would be.

The rotors do get much hotter with these compounds, and we do a full 20 minute session which would also have an input to the rotor temps. I have had to increase the air flow to the front rotors to be able to use these compounds, and thought you should know before you try them out, if you use these compounds your next track day

Edited May 3, 2007 by tacker

[dangerous_daveo]

So ask a silly question, what is the advantage in having 8 pistons? I mean I understand the advantage in having bigger brakes. Just not in having 8 pistons.

Either way good write up! Wish more people would do it properly like you have.

[Ronin 09]

So ask a silly question, what is the advantage in having 8 pistons? I mean I understand the advantage in having bigger brakes. Just not in having 8 pistons.

Either way good write up! Wish more people would do it properly like you have.

they are some mighty small pistons too

[dontfeelcold]

In a nutshell, more pistons spread the load across a greater area of the pad. Hopefully someone more knowledgeable can point out some of the pro's of this as I don't want to say the wrong thing.

[B-Man]

I think there is also the stilhetto effect (what hurts more - when you get your foot stepped by a high heel shoe or a sneaker) - small surface area of the piston(s) = more force. Same reason, I think, that button (puck) clutches are effective.