Information: This Hi Spec Motorsport Billet 4 conversion kit will fit your Vauxhal Astra Mk2. For small to medium weight road cars, a Hi Spec Billet 4 Conversion is the ideal kit. With disc sizes ranging from 280mm to 325mm giving increased leverage, higher rotation speed of the disc relative to the pad and more surface area to assist with heat dissipation when compared with standard set ups.
Pricing: Product pricing is for a 1 complete Hi Spec kit, (both front hubs).
What does a full conversion kit do? This full kit combines a Billet-4. 4-pot alloy caliper with large two-piece discs to give a significant increase in stopping power. The improved stopping power of the calipers join forces with the greater leverage and heat dissipation properties to take braking performance into another league.
Fitting these alloy calipers and light weight one or two-piece discs has the added benefit of reducing unsprung weight. This is more important than just losing weight from the car. Losing unsprung weight means better handling and response from dampers.
What is a Billet-4. caliper? As its name suggests the Billet-4. caliper is CNC machined from aerospace grade billet aluminium. The result is a super-rigid caliper with almost no flex, (a common problem with other alloy calipers). The Billet-4. features integral dust seals, internal fluid transfer galleries and a fully anodised finish in a choice of three colours.
Kit Content: This kit includes the following parts:
- 2 x Billet 4 Radial Calipers
- 2 x Aluminium Bells
- 2 x Straight Vane Rotors
- 2 x Brackets
- 1 x Rotor/Bell Hardware Pack
- 1 x Bracket Hardware Pack
- 1 x EBC Standard Road Pads (Upgradeable)
- 1 x Dot 5.1 Brake Fluid
- 2 x Braided Hoses (Optional)
Wheel clearance: Designed to clear 17″ wheels. Before ordering please check your wheel clearances. HiSpec calipers are wider than the standard sliding caliper, therefore we cannot guarantee fitment for every wheel on the market. You can check your clearances by clicking the wheel clearance diagram above. The wheel size listed is for the standard wheel.
Will it fit my car?
This kit is built for the car named in the listing, and the generation matters: hub design, hub bell shape, and caliper bracketry are car-specific even when the disc size looks the same. If your car is near a facelift year or an unusual variant, send us the registration and we will confirm the exact kit before you order.
Will it clear my wheels?
For this 325mm HiSpec kit, the minimum wheel diameter is 17in, and that figure belongs to the kit rather than the car, so it holds whatever you drive. Diameter is only half the story though: spoke depth is wheel-design-specific, so if you run aftermarket wheels with deep spokes, send us a photo and the wheel model and we will check clearance properly.
Do I need to upgrade the rear at the same time?
No. The front does the large majority of the braking, so a front kit alone is the normal first step and a balanced one. Upgrade the rear later if you want matched looks or you are building for sustained track work, and if the car has an electronic parking brake, read our guide on rear kits and electronic handbrakes before planning that side.
Which pad compound should I run?
It depends on use, not on the kit: fast road, track day, and race compounds behave very differently when cold and when worked hard. Our guide on brake pad compounds explains the choices for HiSpec kits in plain terms, and heading to a circuit, our track day brake prep guide covers pads, fluid, and bedding in.
What does the 4-piston caliper actually give me?
More pistons spread clamping pressure across a bigger pad more evenly, which improves pedal feel and pad wear rather than raw stopping power, and the bigger disc adds the leverage and heat capacity. The honest summary: consistency lap after lap, and a pedal you can modulate, not a party trick emergency stop.
Every brake kit here is built to order
We do not keep big brake kits on a shelf. Each one is put together for your car in the disc face, caliper colour and specification you choose when you order, so nothing is made until the order is placed. The site shows these as available because we can take the order and start it, not because it is boxed and waiting.
How long it takes
Brembo GT kits are made in Italy and run around six to eight weeks. Our UK built kits are quicker, and the exact time depends on the caliper and disc combination you pick. Ring us on 0115 989 3488 before you order and we will give you the current lead time for the kit you are looking at, not a general one.
Working to a date
If the car is booked in, or it is off the road, tell us the date when you call. We will tell you straight whether the kit will make it, and what the alternatives are if it will not.
Worth two minutes before you order
Wheel clearance catches people out. Send us your wheel make, size and offset and we will read it against the caliper clearance drawing first, because a kit that is already being built for you is not something we can simply swap.
