105 Brakes - Bonaldi Booster Options

[ACP]

Hi,

The 105 which I am about to receive has a problem in the braking department, pedal to the floor job(lovely really).

Anyways the master cylinder(single circuit) was checked, and replaced the seals there.  The front calipers are aok, the rear are sticking a bit but appear ok.

The booster is a Bonaldi, and I think that may be the problem. 

Can I simply remove the Bonaldi from the circuit?  The brake pressure required will be higher but has anyone tried it?

Also is there anything else which should be checked?

Cheers,
Andrew.

[MD]

Could it be the master cylinder itself? Does it use "O" rings instead of cups? When overhauled, did they use local or original rubbers? I am thinking blow by here..inoperative boosters usually just cause a heavy pedal.

BTW, if you cannot service the Benaldis, you could substitute VH44's and they are still available if a little pricey.

[ACP]

Thanks for the info, called up a fellow in Vic who said he could repair it for bulk $.  Hopefully some more progress can be made with the bypass of the booster.  The old man tried it last night but cross threaded the bypass pipe! 

The car has been sitting for a while (3+ yrs), and we knew the booster wasn't working properly before as it had a hard pedal!

So it is probably a challenge with the bleed first.

Cheers,
AP

[GTAM1]

I've run my 105GT without the booster for many years without any dramas.
The pedal does require a little more muscle to acheive the same level of performance as boosted brakes but i found it to provide better feeling pedal.

[ACP]

Well I got word back that the brakes have been bled properly, and it is currently running without the booster.

A few more leg exercises and I will be right.

I will get the booster and some of the other spares with the car anyway, so if it is too much I will send it away to get re-built.

Cheers,
AP

[1750GTV]

Yeah - the pedal to the floor is usually a system full of air. Glad it's all functioning again.

My brakes (twin circuit Bonaldi) shat themselves some time ago and over a couple of months I rebuilt everything but the boosters. I ran the car without vacuum boost until I could afford a pair of new ones ($$++). The brakes were fine - I had to push a little harder on the pedal, but they worked well and gave me no frights.

I believe that the earlier systems came with different bore master cylinders. A larger bore m/c for the non-boosted brakes and a smaller bore one for the single boosted systems. The larger bore just gave you a better hydraulic mechanical advantage. This may be an option for you to consider.

As you've discovered, the Bonaldi boosters are poisonously expensive to buy or repair. If I were you, and you don't mind the non-originality, I'd just drive an unassisted system. That is, if you can stop your Dad from cross-threading everything

Chris

PS: Welcome to the list.