VT Brake upgrade - Long and Spongy Pedal

[HamaTime™]

So my VT brake upgrade went on yesterday.

• VT Calipers
• VT Slotted Rotors
• VT Pads
• VT Master Cylinder onto VS Booster (still using VT Reservoir because the VS one doesn't bolt directly on)
• VT modified brake lines (so they're long enough)

However, as I had a sneaky suspicion that this would happen. The pedal is now long and spongy, i.e. the top 40% of the pedal has no affect at all (as the bigger piston calipers need more fluid/pressure to push them out) and they aren't as responsive yet (even though I haven't worn in the pads/rotors yet).

I was just wondering how I can go about fixing this, or is this something i will have to fix by putting on the VT booster (which I planned to fit later, but I didn't expect the pedal to be this bad).

Any suggestions?

 

[88GreenVN]

Dunno - I just went for the VT M/C and booster with modified braket and left the standard callipers and rotor inplace.

Pedal is rock hard and light as to press. Is the booster that you have OK?

PS- Ive done this upgrade to all 3 of my VN's with no problems (1 V8 & 2 V6's)

 

[HamaTime™]

The booster is the stock one (VS). And it's pretty bad, as in when I had my stock VS brake setup on, the brakes were ****, even after the rotors were recently machined and new pads went on.

The only problem with the set up at the moment is the fact that there is a 40% play where there are no brakes, and I really want to get responsive braking right at the top of the pedal.

So, one step is to replace the Booster (in process of acquiring a fabricated mounting bracket) - I was just wondering if anyone else has had similar problems to me and if they have any tips to fix it.

Could it need another bleed?

 

[88GreenVN]

Not if its firm - at 60% on (ie the first bit slack only) The booster needs good vacum to work and if leaking - brakes will never improve.

You could also need to move the pin location on the booster rod - I did with all 3 of mine.

 

[HamaTime™]

Well it's firmish on the last part of the pedal where the brakes actually work.

How can I test to see if the booster is holding vaccum properly?

 

[88GreenVN]

It's hard to test in the drive way - My 88 wagon had a buggered booster after it was rear ended while my daughter had her foot on the brake. Brakes still worked just needed more foot effort to work. I was told by a mechanic that this often stuff the booster in cases like this. Once changed the brakes were soooo much better.

So I'm very sus about your booster because you are not getting any "help" as such when braking. And thats all the booster is ment to do.

After doing my wagons upgrade it took 5 or so mins to pump up the brakes and a trip around the block had them work real nice.

 

[HamaTime™]

Ahhh ok. Well I was rear ended a little while ago (actually a sandwhich accident, I got pushed into someone in front) but there was no body damage, i.e. a slight bump so I don't think that that could have buggered up the Booster. Anyway, from what your describing, it does sound like I might have a leaking/faulty booster.

I haven't worn the brakes in yet, but even at the pedal pressure where the brakes are actually working, they aren't very responsive....and maybe the lack of vaccum/assistance from the booster is what is causing that 40% play in the pedal?

 

[Not_An_Abba_Fan]

It will be the shaft in the booster. When you chnge the master cylinder but leave the booster, the shaft is shorter that comes out of the booster and goes into the master cylinder. You can either change to the VT booster, or get an adaptor that lengthens the shaft a bit. But I don't know by how much it needs to be lengthened.

 

[HamaTime™]

Really? I thought thats what the adaptor plate that goes between the M/C and the VS booster (that I got from Race Brakes Sydney) was meant to eliminate that problem?

But yeah I'm thinking I might as well just chuck on the VT booster.

 

[88GreenVN]

I got the line adapters from Race Brakes for both of the V6 upgrades - but thats all. I fitted the kit supplied by markovr on here.

He moved the pin hole on the booster shaft, made the adaper bracket to the fire wall and the spacer for the front of the M/C and added the AU resivour.