FS: Front Brake Upgrade

[zep]

Right guys,

I talked to Peter at Hopper SToppers about the m/c and I'm going to need bigger front brakes (unfortunately for me!!!) damn it.

So I'm selling this kit again.

It's a Ben Wight option 2 kit with 258mm diameter 22mm thick ventilated discs and is a complete bolt on for a Gemini - and probably a Chevette too. Will have travelled less than 500km.

$350 to anyone from this forum. I gotta sell this to fund the new one!!

www.giant.net.au/users/wight/Option%202%20-%20Performance%20Disks.htm

[mikuni]

13's won't fit over them aye? Why did he think you need to upgrade? Maybe he just wants to sell you some more stuff! I can't see the reasoning behind it. You should talk to an unbiased brake professional, just to double check.

[zep]

I'll copy in my emails...

From me to Hoppers
Hi there,

I'm contacting you regarding how I am to set up a brake bias valve using one of your master cyclinders. I currently have one of your 1" bore 4 bolt Gemini m/c's for my car. My problem is that after the modifications I've done, my rear calipers are slightly bigger than my front ones (about 1cm squared more area on the rear). The front brakes are a Gemini big brake kit which includes 258mm vented rotors (I think these are from a volvo) and Commodore 1 pot calipers. The rear are XE Falcon disc brakes and calipers.

So my question is: am I able to run some sort of bias valve with your master cyclinder? Could you give me some reccommendations on where to start?

Thanks

Leon

Reply
Leon

I think you are going to have problems making this work at all.

Usually the front piston area is twice the rear caliper piston area, typicially Ford are 60mm front with 44mm rear and Commodore 54 front with 38 rear.

You will still have too much base rear brakes below the prop valve setting so it will still overbrake the rear on light braking.

I dont think a 258 front rotor with a 54 mm commodore caliper is much of an upgrade either.

Front VT calipers with twin 42mm pistons on 296 by 28 rotors sounds more like a better balance.

However if you are going to stay the way it is now all you can do is fit an adjustable prop valve and screw it all the way in and see if you can get it to go low enough.

regards
Peter Koning

my reply to hoppers

Hi Peter,

Thanks for your reply. I do want this to work properly and I was expecting to maybe have to get a larger front brake kit. I do need something which will fit over 15" rims.

What are you able to supply me with which you think would be a suitable upgrade to work with these faclon brakes, adn how much $$ would I be looking at? I also need to keep the 4x100 stud pattern.

Thanks,

Leon


reply

Leon

yep that easy, but I assumed the car is a Gemini?
If so what you need is our 296 by 28 VT kit in 4 stud pattern, all bolt onto std stub axle and fits 15 inch wheels ok

$790 with smooth rotors $890 slotted and $920 drilled and slotted

Regards

Peter

[gordo]

Three things set the braking torque - total area of pistons, effective radius of the piston (average distance of the pistons) from the point of rotation and co-efficient of friction between the pads and the disc.
The torque being directly proportional to each factor.

In this case, I would assume that the rears are also operating at a greater radius as well as being of greater area. This will compound the problem.

It is not that uncommon for the brake bias to be a little to the rear under light breaking, supposedly for stability, with a prortioning valve reducing the pressure ratio to the rear over a set point - NOTE, this is not a pressure limiting device which limits the pressure at a set point, although one may also be used to prevent lockup under extreme braking.

In your instance, you can experiment with a proportionating device, change your front brakes - perhaps just convert to larger or 4 pot calipers rather than the whole thing, check if a smaller rear caliper is available, or fit a pedal box with a smaller master cylinder to the front - yes, that's right, smaller master cylinder to increase line pressure.

What diameter wheels are you actually going to be using? I would probably factor that into the decision as clearance may be crucial.
Type of driving may also be worth considering.

[zep]

I'm running 15"s, as is said in those emails, the 296mm kit will fit under them.

I'm tending towards trusting this dude, his company is mega reputable and im sure they have done this type of thing many-a-time. Might just have to shell out and get it.

So someone buy my one!! Pleeeeaaaaassee

[mikuni]

zep said:

So someone buy my one!! Pleeeeaaaaassee

Nah, because according to that aussie dude they aren't much of an upgrade .

I'm sure there are better options than buying over a grand worth of massive brakes. It may be the easiest fix though, after reading gordos advice it sounds like it may be very difficult to get a set up working without putting massive brakes at the front.

So 13's don't fit over your ones then? If your not sure I'll come up and try them in a couple of weeks if you still have them then.

[zep]

Nah I'm not sure, you can definately have a test tho. They wont be going anywhere for a few weeks anyway.

[gordo]

zep said:

I'm running 15"s, as is said in those emails, the 296mm kit will fit under them.

I'm tending towards trusting this dude, his company is mega reputable and im sure they have done this type of thing many-a-time. Might just have to shell out and get it.

So someone buy my one!! Pleeeeaaaaassee

Sorry, already got vented and four spots with pedal box to go on the car - if I EVER get it done
IMO, if you're already on 15's, then go for the bigger brakes as, IMO, few things are as naff as big wheels with bicycle brakes behind them - you know about 7" discs

[zep]

Yeah, the bigger disc will look better anyway
Gonna get them I think, just gonna have to hold off on paint for a while. Will be a rat-gem(ish) with a mean engine

[mikuni]

Awesome, I'll put money towards some paint stripper and oven cleaner

[zep]

Hahah not that rat... prolly just a few primer patches to hold off the rust!