You beauty!.........through engineering

[BEB]

Originally Posted by 400TT

Well done mate.

The Nissan calipers will help rectify the front -> back brake balance. Are your calipers the 4 piston jag ones, I know they are the worst for brake balance in a cobra as they have very large pistons. 48mm pistons from memory. The Nissan calipers have smaller 37mm pistons. Assuming you pedal ratio is similiar to mine, I've calculated with standard jag rotor, that Nissan calipers will give close to perfect brake balance. If you have a larger rotor(like I have bought), then you will need something in between the jag and nissan piston sizes. You can get Wilwoods that are perfect, just slightly larger pistons than the Skyline calipers or 2 piston PBR calipers that have 42mm piston sizes from memory, getting a little on the large size, but still much better than jag 4 piston.

The jag 3 piston calipers have a much better piston size and will help brake balance.

Is your pedal travel feel about right?

I would fix the brake balance first, then see how it all feels.

You can sit down and calculate this stuff, lots of info on the Internet on it. Very time consuming though.

Hi,

I'm following this post with much interest from the UK.

The front brakes on my Cobra lock up too easily and l would like to know more about the Nissan calipers you're talking about.
I have series 2 Jaguar brakes with standard size rotors and although l have looked at replacing the pedal box with twin master cylinder/adjustable brake bias, but can't find anything to fit so maybe the Nissan calipers with the smaller pistons would help.

What exactly are the Nissan calipers you are talking about - model, year, part numbers, etc.

Thank you.

[400TT]

Originally Posted by BEB

What exactly are the Nissan calipers you are talking about - model, year, part numbers, etc.

Nissan Skyline R32 & R33. You would probably find R32 GTS-T model the best suited as they come off a similiar sized & thickness rotor.

All the calipers are 4 piston. R32 GTR & R33 GTS-T have calipers that were off 300mm rotors.

Nissan 300ZX Z32 Calipers from same era are the same.

It's relatively easy to spot the smaller sized calipers(R32 GTST/Z32) as they have shallow ribs. All the other calipers have smooth housing.

Calipers are labelled with Nissan or Sumitomo.

Hope that helps.

I picked up this knowledge from building a Cobra with Skyline rear end, front uprights & Skyline brakes front & back.

The reasoning for changing caliper is that it will not only help correct the brake inbalance, but you also end up with a very small & lightweight caliper that will reduce unsprung weight and perform much better than the old Jag calipers.

[REPTYL]

Well done Steve,

Busy with work stuff so haven't had time to read all the posts, so forgive me if someone has already covered this.

Rather than a full brake upgrade. Maybe put in a Holden one toner master cylinder and add a wilwood adjustable pressure gate.
Why reduce your braking on the front when you can increase the rears to match.

Cheaper and manual adjustment for varying track or tyre conditions.

See you thursday night.

[Luke Gillett]

Well done Slowy
Not long to go now.

All the best,
Luke.....

[CHANMADD]

I use Series 1 Jag front calipers(3 piston),you could put a spacer between the caliper halves to account for the thicker vented rotor which would be much less money than Wilwoods or the like and they work!!,and a Alfasud pedal box assembly with master cylinders and my brake balance is near perfect.

[400TT]

Stephen, better late than never. My pedal ratio in the RMC is 4.1:1, which is bang on the money in my books for a boosted system.

Did you get a chance to measure your pedal ratio?

[BEB]

Originally Posted by 400TT

Nissan Skyline R32 & R33. You would probably find R32 GTS-T model the best suited as they come off a similiar sized & thickness rotor.

All the calipers are 4 piston. R32 GTR & R33 GTS-T have calipers that were off 300mm rotors.

Nissan 300ZX Z32 Calipers from same era are the same.

It's relatively easy to spot the smaller sized calipers(R32 GTST/Z32) as they have shallow ribs. All the other calipers have smooth housing.

Calipers are labelled with Nissan or Sumitomo.

Hope that helps.

I picked up this knowledge from building a Cobra with Skyline rear end, front uprights & Skyline brakes front & back.

The reasoning for changing caliper is that it will not only help correct the brake inbalance, but you also end up with a very small & lightweight caliper that will reduce unsprung weight and perform much better than the old Jag calipers.

Hi,

So it looks like either the Skyline R32 GTS-T or 300ZX Z32 calipers are the one's to go for.

Are the mounting points exactly the same as Jaguar - do they simply bolt on?

The current rotor size is 285 x 24mm.

Any other help/advice you can offer is appreciated.

Thanks again,
Simon

[400TT]

Simon, you will need to make adaptors for the calipers. The caliper mounting ears are no where near the same.

You will also need to put same spacer plates between the pistons and brake pad as you have a narrow rotor.

[stephen low]

Craig

Hadn't got around to measuring my pedal but I will tomorrow.

But for clarity from where to where did you take the measurements on the brake pedal?

Am I right in saying centre of pivot point to centre of brake piston versus pivot to end of pedal?

Let me know and I can make the same and thus comparative measurements.

Cheers

Steve

[400TT]

Originally Posted by stephen low

Am I right in saying centre of pivot point to centre of brake piston versus pivot to end of pedal?

Yep, that's it.

[stephen low]

Craig

Measured my ratio at 4.3:1 so not much different you your set up.

Thinking about this, setting a lower ratio by moving the booster connection point closer to the pedal pivot ie requiring more pedal pressure for the same outcome wont change the effect at the wheels as far as I can see.

So you need more pressure but are still only achieving the same effect at tyre, I think your suggestion re reduced piston size might have more merit.

Still think I need to see a brake specialist!

Cheers

[400TT]

Pedal ratio has a significant effect on brake feel & performance. Don't underestimate it.

But your pedal ratio is in the right ball park, so we've ruled it out as a major cause. Just something easy for you to check and soemthing that could be very wrong in kit cars.

I still reckon it's a brake balance issue. But that's only a guess as it's a bit hard to diagnose this here.

You definitely need a brake specialist. Brakes are something we all need to get right. Let us know how you go.

P.S. Plus I wanted to see if you could contort yourself enough to get in and measure the ratio. I was lucky and had the seats out at least.

[stephen low]

You Bast... Craig, my seat was in but not my steering wheel or shroud, it was still hard to measure!

[400TT]

Your steering wheel was out. Bugger, my (16") steering wheel was in and it certainly caused me all sorts of problems.

Looks like my plan might have backfired.

[stephen low]

Chased my engineer as to whether he has seen my VIN yet but no luck. Seems Vicroads must be going into Xmas mode early, damn bureaucrats.

But good news is that the process of making the VIN application locks my car into the system for compliance, presumably as of the date of the application or its entry into the system.

Also took the opportunity to re-question the engineer on the brakes and it is the balance he is suggesting as needing tweaking as the best way to reduce the early front wheel lock up tendancy.

Presumably there are simple brake balance systems out there that can be fitting into the system? Can anyone point me at a picture of something applicable?

Is it a case of just re-routing all brake line outlets on the master through the proportioning system and thence to each corner? Then playing on road to get a suitable balance?

Any information would be great.

Cheers

[Aussie Mike]

My VIN seemed to take an eternity to arrive. I think I waited nearly 4 weeks. Hang in there, you'll be registered before you know it.

Cheers

[400TT]

Sounds like you are going to have to be patient for that VIN. QLD is no different, it's months for QT to approve.

Stephen, you will have to modify/disable the internal proportioning valve in that master cylinder of yours, then fit an in-line manual adjustable proportioning unit. Speak to a brake master cylinder reconditioning place, they will know what to do and what's the best approach with your master cylinder. They might also be able to correct the brake balance by swapping you to a different master cylinder.

Or alternatively you can fit better front calipers that have smaller piston capacity, that will also fix your brake balance and improve front braking. Nissan Skyline calipers should perfect piston size for you, but you will need to make sure you can mount/adapt them. The location of the mounting tangs on the calipers could make them anywhere from easy to difficult to mount.

Your pedal ratio is right, so you should be able to get great feeling brakes.

[WKB]

Slowy.
My car took 19 weeks from engineering to registration. Customer service is not a strong point for Qld transport. You learn all about patience.

Warren

[stephen low]

Thanks guys.

Seems I might need to get another play permit for a short stint. I reckon vicroads won't be any better or worse than other Govt departments so I'll just have to wait!

Will talk the brake place I used to supply, recondition and repair some of my gear to get further advice. Fellow seems quite switched on and may have a solution.

Cheers

[400TT]

Originally Posted by WKB

Slowy.
My car took 19 weeks from engineering to registration. Customer service is not a strong point for Qld transport. You learn all about patience.

Warren

Warren, it certainly takes some patience. I think our wait was actually longer than that, can't remember now. It was long enough that we had actually just about given up hope.