How To Choose The Right Hi Spec Big Brake Kit
Hi Spec’s UK made big brake kits are built across four caliper tiers rather than sold as one generic product, and picking the wrong tier is the most common mistake we see. The tier matters more than the raw disc size, two kits can share a disc and still be a full step apart on caliper stiffness and price.
This guide works through the tier ladder, why disc size and wheel clearance are two separate questions, and how pad compound choice finishes the job. It’s written from what we actually stock and sell, not a general spec sheet.
- Hi Spec kits run four tiers: Billet 4, Monster 4, Monster 6 and Mega Monster
- Prices below are live BigBrakes4u prices, checked 6 September 2026
- Every Hi Spec conversion kit on our site is made to order in the UK
- Free UK shipping applies on any order over £100
The Hi Spec tier ladder
Hi Spec’s UK big brake kits split into four tiers: Billet 4, Monster 4, Monster 6 and Mega Monster. The names describe the caliper, not the disc, so two kits can share a disc size and still sit a tier apart. Billet 4 is the entry caliper, a four piston design aimed at road use and fast road driving. Monster 4 and Monster 6 step up caliper stiffness and pad area for cars that see track days as well as road miles. Mega Monster is the biggest caliper in the range, the one we’d point at cars doing serious track work or heavier vehicles that need more clamping force.
The Volkswagen Golf Mk4 is a useful example because Hi Spec lists it across every tier at the same 335mm disc size. A Billet 4 kit is £1,357.50, a Monster 4 kit is £1,534.62 and a Monster 6 kit is £1,671.90, same disc, heavier caliper each step. Go up to the 360mm Mega Monster kit and the price moves to £2,033.82. That jump is the caliper tier doing the work, not the disc diameter.
| Tier | Disc size | Price (inc VAT) |
|---|---|---|
| Billet 4 | 335/28mm | £1,357.50 |
| Monster 4 | 335/28mm | £1,534.62 |
| Monster 6 | 335/28mm | £1,671.90 |
| Mega Monster | 360/28mm | £2,033.82 |
Volkswagen Golf Mk4 Hi Spec conversion kits, prices correct on 6 September 2026
Disc size and wheel clearance
Bigger discs need more room inside the wheel, and that’s a clearance question before it’s a performance one. The disc has to clear the wheel’s inner barrel and spokes, and the caliper, which usually sticks out further than the disc itself, has to clear the same spokes at full lock. As a rule of thumb, four and six piston kits in the 300 to 360mm range fit inside a 17 or 18 inch wheel with an open enough spoke design. Kits above 380mm and the bigger multi piston calipers usually need at least an 18 inch wheel, sometimes 19 or 20 inch depending on the spoke pattern.
The only way to be certain is to check your actual wheel, not a generic size chart. Send us a photo of the wheel face on with the make and model, and we’ll tell you if it clears before you order.
Pad compound choice
The caliper and disc are only half of how a kit stops. Pad compound decides how it bites cold, how it copes with heat, and how much dust and noise you live with day to day. Fit a track compound on a car that only sees road use and you get a cold, grabby pedal every morning until the pads warm through. Fit a road compound on a car doing regular track days and the pads will fade the first time you lean on the brakes for three laps.
We’ve written a full breakdown of the compounds we stock and which suits which use, read it before you order pads: Brake Pad Compounds Explained.
Road use vs track use
If the car is a road car that sees the odd track day, a Billet 4 or Monster 4 kit with a dual purpose pad covers most people well. If it does regular track days or full days on circuit, step up to Monster 6 or Mega Monster and run a proper track compound, and read our guide on getting your brakes ready for a track day before you go out. Bedding in matters as much as the kit you buy.
Call us on 0115 9893488 if you’re not sure which tier your car and use case needs. We’d rather talk it through than have you order the wrong kit.
Common questions
What's the difference between Hi Spec Billet 4 and Monster 4?
Both are four piston calipers, but Monster 4 uses a bigger, stiffer caliper body and more pad area, built for cars doing track days as well as road miles. Billet 4 is the road focused entry point.
Does a bigger disc always mean a bigger caliper?
No. Hi Spec lists the same disc size across two or three tiers on plenty of cars, the caliper tier is what changes, not just the disc.
Will a Hi Spec kit fit under my wheels?
Depends on the wheel, not just the kit. Send us the make, model and a photo of the wheel and we'll check clearance before you order.
Are Hi Spec kits made to order?
Yes, every Hi Spec conversion kit on our site is made to order in the UK.
Which pad compound should I run?
Depends on how you use the car. Read Brake Pad Compounds Explained or call us on 0115 9893488 and we'll recommend one.
What we would actually fit
For most road cars that see the odd track day, I’d start at Monster 4 instead of Billet 4, the extra caliper stiffness is worth the difference in price when you’re leaning on the pedal at the end of a straight. If the car is doing regular track days, go to Monster 6 or Mega Monster and pair it with a proper track pad, a bigger caliper on a road compound is wasted money. Whatever tier you’re looking at, call 0115 9893488 before you order, Garreth or the team can confirm the wheel clearance and pad choice in five minutes.