Which rotor hats take the GiroDisc 348mm Front Replacement Rings?

The GiroDisc 348mm Front Replacement Rings fit the hats of the GiroDisc A1-307 front rotors used on the GR Supra 3.0 and BMW G-chassis M Performance models. They are designed for GiroDisc hats only, so a vehicle on factory front discs needs the complete rotors first.

How thick are the new front rings and when are they worn out?

New rings measure 36mm thick. GiroDisc sets the minimum at 34mm, so a ring that has lost 2mm of material is due for replacement. Replace it earlier if a crack forms that runs to the outer edge, regardless of the thickness that remains.

Do the front rings come with new mounting hardware?

Yes. Each pair includes replacement hardware, so the old hardware is retired along with the worn rings. Only the anodized aluminum hats carry over, which is why a two-piece rotor costs less to keep running than buying complete discs each time.

Will these rings fit a Supra Final Edition?

No. GiroDisc excludes the GR Supra Final Edition from the matching A1-307 front rotor, so these rings are not listed for that model either. They are intended for the standard GR Supra 3.0 and the BMW G-chassis models GiroDisc names.

How do the curved vanes cool the front rings?

The 72 curved vanes inside each ring act as a centrifugal pump. As the wheel turns, they pull air in through the hub area and push it out through the disc, carrying heat away from the friction surfaces during repeated hard stops on track.

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Description

GiroDisc 348mm Front Replacement Rings for Toyota GR Supra and BMW G-Chassis M Performance Models

GiroDisc’s 348mm Front Replacement Rings for Toyota GR Supra and BMW G-chassis M Performance models renew the friction rings on GiroDisc A1-307 front rotors, keeping the anodized aluminum hats in service. Each ring is 36mm thick when new with 72 curved vanes, and GiroDisc machines it from its own high-carbon iron casting in Bellingham, Washington. Supra and M40i owners who track their cars will reach the 34mm limit sooner than road drivers, and this pair with fresh hardware is what goes on next.

Fitment and Installation

The rings bolt to the existing GiroDisc hats with the replacement hardware supplied, and nothing else on the vehicle changes. They suit GiroDisc hats only, not factory hats or other brands. Keep each ring on the side marked on it so the curved vanes pump air outward, and leave the cap screws at no more than 60 in-lb, or 7 Nm.

Features

348mm outer diameter, 36mm thick when new
34mm minimum thickness, per GiroDisc
72 curved cooling vanes
Pair of rings with replacement hardware
High-carbon iron cast to GiroDisc specification
Made in-house in Bellingham, Washington

What’s Included

Front replacement rings (L/R)
Replacement mounting hardware

Applications

BMW M340i with optional M Sport brakes: G2X
BMW M440i with optional M Sport brakes: G2X
BMW X3 M40i: G01
BMW X4 M40i: G02
BMW Z4 M40i: G29
Toyota GR Supra, excluding Final Edition: 3.0L

Notes

The 348mm Front Replacement Rings fit GiroDisc hats only; hats are not included
They bolt to the hats of the GiroDisc 348mm front rotors and fit those hats only
The rear axle uses the GiroDisc 345mm rear replacement rings
GR Supra Final Edition cars are not covered, as the matching front rotor excludes them
Stock photography may not depict the actual product

Frequently Asked Questions

Which rotor hats take the GiroDisc 348mm Front Replacement Rings? The GiroDisc 348mm Front Replacement Rings fit the hats of the GiroDisc A1-307 front rotors used on the GR Supra 3.0 and BMW G-chassis M Performance models. They are designed for GiroDisc hats only, so a vehicle on factory front discs needs the complete rotors first.
How thick are the new front rings and when are they worn out? New rings measure 36mm thick. GiroDisc sets the minimum at 34mm, so a ring that has lost 2mm of material is due for replacement. Replace it earlier if a crack forms that runs to the outer edge, regardless of the thickness that remains.
Do the front rings come with new mounting hardware? Yes. Each pair includes replacement hardware, so the old hardware is retired along with the worn rings. Only the anodized aluminum hats carry over, which is why a two-piece rotor costs less to keep running than buying complete discs each time.
Will these rings fit a Supra Final Edition? No. GiroDisc excludes the GR Supra Final Edition from the matching A1-307 front rotor, so these rings are not listed for that model either. They are intended for the standard GR Supra 3.0 and the BMW G-chassis models GiroDisc names.
How do the curved vanes cool the front rings? The 72 curved vanes inside each ring act as a centrifugal pump. As the wheel turns, they pull air in through the hub area and push it out through the disc, carrying heat away from the friction surfaces during repeated hard stops on track.

About GiroDisc

GiroDisc designs, manufactures, and sells 2-piece, fully floating brake rotors for a wide range of performance vehicles. Every major component, including the hats, rotor rings, and drive pins, is manufactured in-house at their facility in Bellingham, Washington, from domestically sourced materials. GiroDisc rotors use a proprietary high-carbon iron ring formulated for superior metallurgy and thermal performance, paired with reusable machined-aluminum hats that reduce the long-term cost of maintaining a high-performance brake system. The 2-piece floating design sheds unsprung and rotating mass while remaining street-friendly, delivering race-proven braking for track and street use alike.

Additional Information

The Bulletproof Automotive website contains many thousands of products purchased in multiple different currencies. All of the prices are entered manually and accurately at the time of entry. Due to the consistently fluctuating international exchange rates, at times prices may not be able to be honored at their original intended rate. We apologize for any inconvenience this may cause, unfortunately our website is unable to compensate dynamically for what can at times be volatile changes in the cost of items due to currency values fluctuating, changes in prices from suppliers, changes in shipping and import duties, and other factors. Rest assured that any order you place on line will be at zero risk to you in this area. If in the event your order cannot be fulfilled at the original intended website price we will offer you a 100% refund, no questions asked. We will continue to do our best to maintain updated prices and we will always continue to offer our price match guarantees as well to ensure our prices are always the best for you. In short, prices may change without notice. It is always advised to give us a call prior to placing your order online to confirm availability and to confirm current pricing.

Shipping Policy

Items that are in stock in the US, either at Bulletproof’s warehouse or at a supplier’s warehouse, are generally delivered within 7-10 days. Special order items from overseas take considerably longer. As a courtesy Bulletproof offers delivery estimates to our customers which take into consideration manufacturer availability and shipping schedule. These estimates represent our best guess based on previous orders from the manufacturer and do not in any way imply a guaranteed delivery window. Many manufacturers work in a “just in time” inventory system and often take 2-20+ weeks to produce an item once an order is submitted. All deliverable items are then sent to our Japanese warehouse. Bulletproof ships a minimum of one full ocean freight container every month from Japan, oftentimes more than one a month. Ocean freight takes an average of 4 weeks. Typically it breaks down to one week in Japan for paperwork and customs, two weeks by boat and one week in US customs/clearance. Due to the wide number of variables between manufacturer and shipping schedules, delivery estimates are simply just that – estimates. We attempt to estimate conservatively and we usually deliver faster than our estimates suggest. It is not Bulletproof’s policy to guarantee delivery time of any special order item, this is impossible for us to do. By ordering you acknowledge that there is no required delivery ETA and an order may not be canceled or altered due to manufacturing or shipping delays, all ETA’s are provided as a best guess only. Please review the full Terms & Conditions here.

BP Pricing Difference

We do pricing a little differently on our JDM brands and we believe in making things simple and clear. No hidden fees or surcharges. Every price you see includes the shipping cost to our office in Los Angeles, California and all the associated taxes/duties/fees for bringing the products into the US. The only shipping you ever pay is from our facility in the US to your location. Be wary of resellers that don’t include the cost of international shipping in their pricing on JDM parts. While we believe we’ll always have the lowest all-in price on JDM products, we offer a price match guarantee for all authentic parts purchased from authorized dealers as well. For many international customers, it’s much more affordable to ship from the USA than from Japan directly, as the air freight and ocean freight costs are typically much less. However, for customers looking to ship directly from Japan outside of North America, or domestically in Japan, we can provide pricing specifically for that scenario. Please do not hesitate to contact us with any pricing questions or concerns. Please email us at sales@bulletproofautomotive.com with any inquiries.

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GiroDisc 348mm Front Replacement Rings for Toyota GR Supra and BMW G-Chassis M Performance Models [D1-307]

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GiroDisc 348mm Front Replacement Rings for Toyota GR Supra and BMW G-Chassis M Performance Models

Fitment and Installation

Features

What’s Included

Applications

Notes

Frequently Asked Questions

About GiroDisc

Reviews