Gemini brakes

[R100]

Well i recently bought this gemini coupe and want to know what is the widest rim (front and rear) i can fit without flareing the guards ?

Ideally i want to fit a 14 or 15" rim.

Car has a bit of lowerage aswell.

Also whats the best way to change the front stud pattern to the more common 4x114.3 or 4x110 as finding non gay wheels with 4x100 sux.

Changing the stud pattern would be a last resort but could be a good way to upgrade the front brakes if i decide to drop a heavier engine in.

Cheers

[Burntrubber]

Go on Ozgemini.com there's heaps of options for brake conversions on Gemini's there's an ozzie company called hopper stoppers they have a website they will make custom hubs that take VT commie brakes.

[matb]

had 15x8, 0 offset, stretched as fuk and still had to bash guards on a brown piece of shit gem we had here for a bit.

[Jase]

8.5s fit on coupe with correct offset

[R100]

8.5s fit on coupe with correct offset

Do the coupes have a slightly larger tyre well or are the sedans, coupes the same.

[CUL8R]

I would be inclined to think with the correct offset you could go 9" , with stretched tyres. My 185/60r13s (banded 13's) fit basically flush on the rear, however I've got about 1-1/2" back space clearance to the shocks/mounting points.

[RUNAMUCK]

best you go one inch wider on the rear then Chris! Just think how jelous Rob would be!

[Jase]

coupes have the smallest well,

wagons largest

sedans in the middle,

have cdt flares if you want to go wider

[R100]

Dragging up this post again as ive been doing a bit of research lately into brake upgrades.

Not interested in rear brake upgrades at the moment, just the front.

I really need to upgrade my front brakes as my engine conversion will be adding significant weight to the car.

I would like to, if possible stay with the 4x100 stud pattern and run 14" rims.

Ive read on "oz gemini" that people fit commy front discs, but some people use VL and some use VT etc. Unfortunatly they are a bit vauge in there descriptions on how and what to do.

I am also aware that piazza brakes bolt up except im not sure this is the type of upgrade i need.

Do the commy brakes fit inside the 14" rims. Does the caliper bolt up, how do you keep the stud pattern 4x100

Would be good to here from someone on here, first hand of what they have done to there car to upgrade the front brakes.

Thanks in advance

[Jase]

my vn has poverty spec 14" rims,

the brakes fit with a relatively fwd offset rim well

and with something zero offset you'll be fine,

i can get you a rim to caliper clearance measurement if you like?

steels will allow more room than alloys of course

[CUL8R]

@ R100 Use a complete Piazza front stub axle, caliper everything attached. I Replaced upper and lower balljoints. While mine was out I replaced the tierod ends and front end bushes as well..

230mm vented front rotors, and still single pot calipers, however surface area is easily double the chevettes original.

[Jase]

i feel piazza's may be enough with decent pads but getting rare now

[R100]

The following is taken from the hoppers stopper website. Pretty interesting stuff, but requires fitment of 15" diameter rims.

Brake upgrades Front, Rear, and Master Cylinders

for Holden Gemini’s

One of the more popular small cars amongst the modified car fraternity is the rear wheel drive Gemini. They lend themselves well to big 4 cylinder, turbo, rotary and V6 conversions. However those 250mm solid discs do leave a bit to be desired and most Engineers require a brake upgrade to match the increased power.

There are various brake improvements available, such as Piazza vented rotors, and adaptations to fit early Commodore rotors. Some need thin shrink sleeves under the wheel bearings, and this creates difficulties for the home mechanic as well as the known risk of the bearings not seating squarely or spinning on the spindle. Where ever possible Hoppers Stoppers fit original bearings in the bores of steel conversion hubs, and design the outer diameters to carry the upgrade rotor, making the brake upgrade a bolt on proposition.

Front Brakes

Hoppers Stoppers upgrades for Gemini’s utilize VT/VZ 296 diameter by 28mm thick vented rotors and twin piston calipers, with original Gemini wheel bearings, seals and grease caps. The holes on the VT caliper cradle bracket need a 0.5mm elongation, and then bolt right on with no brackets required.

The special part is then really the hub, and our ability to source blank rotors to drill them in 4 stud or other special patterns. 5 stud brakes in Commodore pattern use standard VT rotors. On full lock the caliper will just touch the lower control arm, to stop this we suggest you weld a 6mm block against the lower control arm where the steering arm touches, this slightly reduces the turning circle. 15 inch or bigger wheels are needed for this conversion.

One small think to watch is a small increase in wheel offset, as the hub face is now 10mm further out per side. Some find this helps with issues with wheels touching the shock absorbers, but if clearance is tight between tyres and mudguards the change might be of concern. If you haven’t bought new wheels then factor this into your plans. As a rule we find 15 X 6 standard Commodore offset wheels with 195/60-15 tyres clear nicely.

Rear brakes

A lot of Gemini owners do not realize that their standard rear drum brakes are in fact 4 stud versions of the Torana and Commodore rears used at that time.

The shoes, wheel cylinders and all spring and clips are identical, and Holden interchangeability being what it is, early Gemini’s used the same basic parts as Torana’s (incl V8) up to when the Commodores were released and then Gemini and Torana got the Commodore rear drum design, as used up to VL.

The differentials are all in the same family, and use the same wheel bearings, it is therefore easy to have a VL axle shortened and resplined, and thus convert to 5-stud rear.

Better still the Commodore rear disc brake assembly fits the Gemini axle housing ends, the only other difference being the wheel bearings sets are different between drum and disc rears, so you can have a Commodore axle shortened, fit disc brakes bearings, bolt on the full handbrake housing, and slip on Commodore rear discs and calipers. A bit of a fiddle to make the Gemini handbrake cable connect and its all done.

To do a 4-stud disc rear you can simply change the wheel bearings on the original axle to the disc type and bolt on the rest. This of course needs us to drill from blanks some 4-stud rear discs.

All this assumes you will not have issues with diff center strength, as the Gemini’s use a 23 spline axle. Anything stronger means a full diff upgrade such as a 28 spline Commodore conversion.

Master cylinders

Any big brake kit needs a bigger bore master cylinder; we recommend a 1-inch tandem master be used with VT brakes. How to go about this depends on whether you engine conversion requires relocation of the booster.

Gemini’s came in three basic types; the early TX cars used remote fill reservoirs and a four-bolt mounting between master and booster. If you can keep the booster then we have a 1-inch remote fill master that is a straight bolt on.

Later TC to TE cars had a horizontal two-bolt arrangement. Again if you can keep the booster we find an XB Falcon master fits, but you need to extend the output pushrod length to correctly preload the master and repipe to 3/8 ball flare fittings, or use 3/8 to 10mm adapters.

The TF and TG series used an angle bolt master cylinder with a plastic reservoir, and to date we have not found a 1-inch replacement for this unit.

You therefore have to fit an early booster to have a firewall fitted unit on this series.

V6 Commodore conversions VN to VP seem to need total removal of the booster, but it seems that VS and later Ecotech engines are narrower and clear. If you have to go to a remote VH40 booster we have a neat 1-inch bore tandem master, which suits this engine type. If going to four wheel discs you will need two remote VH40’s. Don’t forget that you should retain your brake fail warning light and that the original proportioning valve is the wrong pressure for rear discs. A HZ four-wheel disc unit will be right (now obsolete new) or an adjustable unit needed.

Some cars made in the 70’s worked acceptably with no boosters at all, albeit with higher pedal efforts. In fact rare poverty pack Gemini’s were sold without boosters. I remember one car coming in for a service, after a test drive was about to ring the customer to tell her that her booster had failed only to find it never had one! Bigger calipers and rotors of course stop better, so as long as you use soft high friction pads acceptable brakes can still be had with no booster. Not the thing to let your slightly built girlfriend drive.

[R100]

230mm vented front rotors

What is the size of the standard gem rotors and is the piazza only 230mm ?

[mikuni]

230mm vented front rotors

What is the size of the standard gem rotors and is the piazza only 230mm ?

I thought they were 256mm but I could be wrong. 230 sounds quite small, although I do know they are roughly the same size as factory Gemini ones, but are vented as cul8r mentioned, along with having a much larger caliper/pad size.

I run these on my Chevette and although its not particularly heavy I give the brakes a real hard time on the track and I am yet to be dissapointed. It pulls up very well from 180 clicks on Hampton and is ready again for the next hard braking area, which is apparently a real test for any vehicle's brakes. 13's also fit over them, so it leaves you with options of originality.

There are 3 down sides with Piazza brakes in my opinion. The first is their rarity, in that you need to kill a Piazza to get them because you need the stub axles. The second is that uprated pads aren't particularly cheap or easy to get hold of, but saying they are expensive is untrue. They are around $150 for semi-metalics and I would be surprised if you could get pads for VT disks for that price. And the third down side is that they don't look big and pretty behind open faced wheels.

Take all you read from hoppers with a grain of salt. They are a business that aren't out to help you out, they are out to MAKE MONEY first and foremost. They make Piazza and other bolt on upgrades sound near on impossible and make them out like they wouldn't stop a go kart.

[R100]

There are 3 down sides with Piazza brakes in my opinion. The first is their rarity, in that you need to kill a Piazza to get them because you need the stub axles.

Yes ive noticed that they are hard to find, altho if i can get my hands on a complete Piazza was hoping that i could bolt my old Gemini parts back on to keep the Piazza rolling. (easier to get onto car transporter)

The second is that uprated pads aren't particularly cheap or easy to get hold of, but saying they are expensive is untrue. They are around $150 for semi-metalics and I would be surprised if you could get pads for VT disks for that price.

$150 is not a big price to pay, considering its not as tho they need to be replaced all the time. Question is can you buy good Piazza pads off the shelf ? or do you need to get them made ?

And the third down side is that they don't look big and pretty behind open faced wheels.

Not a problem as im building my Gemini for speed, not looks. Will most likely run a 14" steel or SSR mesh so brakes wont be visable.

[CUL8R]

I could be wrong although Im 99% sure I measured them correctly when I got them resurfaced. Will measure Gem's roughly tommorow at work , then chevettes when I get home (has the piazza's) ...

Theres a cheap piazza in the north island on trademe, $50 starting.....

[Jase]

gem rotors 256

piazzas come in two sizes,

found out when they wouldn't mash back together after buying new from bnt,

[zep]

Tony Lynch does upgrades with E30 rotors and FD (I think) RX7 Calipers. He makes custom lower arms though, so I'm not sure if you need those as well to make this set up fit. I've been in his car and it stops in nanoseconds.

[R100]

Sorry if i sound stupid but who is Tony Lynch ? Te E30 with FD RX7 caliper sounds like it would work excellent. The main reason for my brake upgrade is due to the increase in weight ill be adding with the engine swap.