JDM Brembo lacking in bite and very soft

[iampotato]

Hello all,

So I recently purchased a set of jdm brembo calipers for my dc5. I've put them in, no troubles there. Fully flushed the brake system with some new fluid. No air inside the system, however, my braking performance is very poor, along with very soft pedal feel. I initially thought it might be air in the system, but going at slow speeds, I would have thought there to be a long throw in terms of the pedal if there was air in the system, but the throw is short, just soft and not as responsive.

My thoughts:
- it might be the brake pads, since they are cheap TRW ones, as temp till my project mu's come. I haven't has a chance to bed them in
-I might need a prop valve

Any thoughts and help will be greatly appreciated

What do you guys think is the problem?

[Symphorced]

Machinr the rotors and bed in the pads.

Give the brake system another bleed too.

[iampotato]

Machinr the rotors and bed in the pads.

Give the brake system another bleed too.

The rotors are brand new. I'll bed the pads in tonight and I'll update how that goes.

It's weird that the brake feel is actually more mushy than the stock setup.

[tyk]

Did you do whole conversion or bolt on ?

My braking definitely improved especially hard braking after I bolted on the brembos but I also changed brakelines & stopper.

[iampotato]

Did you do whole conversion or bolt on ?

My braking definitely improved especially hard braking after I bolted on the brembos but I also changed brakelines & stopper.

Just changed the calipers and s2k rotors, i've already got braided brake lines

So anyway, i bed'd my brakes in, 4-5 times from 50km/h to 10, 5 minutes cooldown, and 3-4 times 65-70km/h to 10-15. The bias feels more towards the front, during cooldown, got outside to look at the brakes, fronts were very hot, rears were pretty cool.
After bedding in the brakes, the bite is definately better under hard braking, however, the brake pedal itself is very mushy.

[tuannn]

For you to get better feel, I recommend you changing the Brake Proportioning Valve to the JDM one. Under hard braking on the track, you might experience the rears locking up. This is due to our DC5R's proportioning valve is not optimised for the 4 POT Brembos.

[DaRKNT]

Bleed again after the bedding. It will help, and maybe get them a bit hot and report back how the pedal feel. Good work on the cool down and not glazing the pads. :P

[Stephen_AUS]

I will also highly recommend changing over the prop valve, that will play quite a bit with how it feels and brakes. Do a good bedding as it takes time for the pads to start working good. I recommend a good mountain run if you need to ...

Good brake fluids will do wonders also, I highly recommend Endless for $70 a can should get the brake and clutch done. Otherwise Motul RF650 is another choice as it is much easier to get. The Brembo 4 pot is great, I stop 100-0 in literally seconds with my setup!

[ChargeR]

Try to bleed again, it's strange that the pedal feel is poor with brand new pads and rotors. Typically that's as good as brake feel will get. Consider changing the proportioning valve to the JDM item, though that should not affect the initial pedal feel substantially. Have a read of Npcan2's comments in this thread: LINK

Silly question but did you bleed both sides of the calipers? And did you put them on the correct sides?

I will also highly recommend changing over the prop valve, that will play quite a bit with how it feels and brakes. Do a good bedding as it takes time for the pads to start working good. I recommend a good mountain run if you need to ...

Good brake fluids will do wonders also, I highly recommend Endless for $70 a can should get the brake and clutch done. Otherwise Motul RBF600 or RBF660 is another choice as it is much easier to get. The Brembo 4 pot is great, I stop 100-0 in literally seconds with my setup!

Brake fluid compressibility is not going to vary significantly when comparing any DOT 3 or 4 glycol based fluid, so putting in some overpriced fluid is not going to fix the issue. It is better to fix the issue first with a cheaper fluid before burning money on something that won't make any difference. As another data point my stock calipers on my DC5 also stop my car from 100-0 km/h in literally seconds .

[Stephen_AUS]

Try to bleed again, it's strange that the pedal feel is poor with brand new pads and rotors. Typically that's as good as brake feel will get. Consider changing the proportioning valve to the JDM item, though that should not affect the initial pedal feel substantially. Have a read of Npcan2's comments in this thread: LINK

Silly question but did you bleed both sides of the calipers? And did you put them on the correct sides?



Brake fluid compressibility is not going to vary significantly when comparing any DOT 3 or 4 glycol based fluid, so putting in some overpriced fluid is not going to fix the issue. It is better to fix the issue first with a cheaper fluid before burning money on something that won't make any difference. As another data point my stock calipers on my DC5 also stop my car from 100-0 km/h in literally seconds .

Oh never meant it would fix the issue. Just a recommendation if he ever wants to change fluids for something better

[ChargeR]

Oh never meant it would fix the issue. Just a recommendation if he ever wants to change fluids for something better

So knowing nothing of the threadstarter's driving habits or car usage you recommended $70 worth of brake fluid? This is the technical section remember, for technical things, not for recommending products without good reason.

[Norm]

For you to get better feel, I recommend you changing the Brake Proportioning Valve to the JDM one. Under hard braking on the track, you might experience the rears locking up. This is due to our DC5R's proportioning valve is not optimised for the 4 POT Brembos.

I'm gonna just add my personal experience on the prop valve. I've changed over to the 4 Pot AP Racing calipers without changing over to the JDM Prop valve (I still have the JDM prop valve in my garage). I have no issues with softness or braking bias problems. I have yet to feel this "rears locking up" feeling. At the track, under hard braking your vehicles weight is transfer to the front and this essentially lifts the rear and reduces your tyre contact and traction. Are you sure your not experience this effect? The reason i'm saying this is, a JDM prop valve is not only rare to come across and difficult to source but also costly at the same time. This may not even solve the problems his experiencing.

[iampotato]

I will also highly recommend changing over the prop valve, that will play quite a bit with how it feels and brakes. Do a good bedding as it takes time for the pads to start working good. I recommend a good mountain run if you need to ...

Good brake fluids will do wonders also, I highly recommend Endless for $70 a can should get the brake and clutch done. Otherwise Motul RF650 is another choice as it is much easier to get. The Brembo 4 pot is great, I stop 100-0 in literally seconds with my setup!

Thanks for your input, i'm already using penrite race brake fluid. Just did another bed-in session with the brakes. I'm not 100% if it's placebo, or i'm just getting used to the brakes, but when i put my foot down, there's more of a bite than when i first put the brembos in.

Try to bleed again, it's strange that the pedal feel is poor with brand new pads and rotors. Typically that's as good as brake feel will get. Consider changing the proportioning valve to the JDM item, though that should not affect the initial pedal feel substantially. Have a read of Npcan2's comments in this thread: LINK

Silly question but did you bleed both sides of the calipers? And did you put them on the correct sides?



Brake fluid compressibility is not going to vary significantly when comparing any DOT 3 or 4 glycol based fluid, so putting in some overpriced fluid is not going to fix the issue. It is better to fix the issue first with a cheaper fluid before burning money on something that won't make any difference. As another data point my stock calipers on my DC5 also stop my car from 100-0 km/h in literally seconds .

They're on the correct way i believe, nipples pointing up (at highest point) and bleed the inside nipple, then outside. I did the bleed with my dad and we were 100% sure there was no air in the system at all. Also, i have read npcan's comments on the brembo conversion, makes the idea of getting a prop valve sound pretty good, not sure if it will solve this.

I'm gonna just add my personal experience on the prop valve. I've changed over to the 4 Pot AP Racing calipers without changing over to the JDM Prop valve (I still have the JDM prop valve in my garage). I have no issues with softness or braking bias problems. I have yet to feel this "rears locking up" feeling. At the track, under hard braking your vehicles weight is transfer to the front and this essentially lifts the rear and reduces your tyre contact and traction. Are you sure your not experience this effect? The reason i'm saying this is, a JDM prop valve is not only rare to come across and difficult to source but also costly at the same time. This may not even solve the problems his experiencing.

How much did you get your JDM prop valve for? I'm in the process of sourcing these, I'm not really sure if they're going to be as effective as some claim, since a lot of people don't run it without any issues.

What are your guys thoughts on the JDM brake booster, reckon that would make a big difference in-turn of pedal feel?

[jdm.itr]

Will try your car soon and compare with mine, didn't realise it would be this big of a problem for you

[Norm]

How much did you get your JDM prop valve for? I'm in the process of sourcing these, I'm not really sure if they're going to be as effective as some claim, since a lot of people don't run it without any issues.

What are your guys thoughts on the JDM brake booster, reckon that would make a big difference in-turn of pedal feel?

Off memory I purchased mine around the $200 mark (Used). However I strongly recommend you inspecting all options including a proper bleed process first. Don't waste un-necessary money on items which may not address the problem. It is quite easy to dive into the mindset to buy all these fancy upgrades to address symptoms but not underlying problems.