Speedwell Mudguards

Speedwell is a British mudguard maker that has supplied fenders, number plates and chainguards to the UK motorcycle industry for decades. Autocycle Engineering bought the Speedwell name, rights and original tooling in 1989. Andrew Gregory of Tri-Cor now runs the company. Speedwell still makes OE-style guards on the original tooling and machines in England. Modern British Iron and The Bonneville Shop sell Speedwell mudguards in the USA.

Yes. Every Speedwell mudguard is made by hand in England. Because the guards are formed on the original factory tooling, they match the OEM length, width, radius and profile. Many also have the correct cut-out channels for wiring and battery carrier clearance, which most generic fenders do not.

The MC number is the section, or cross-section profile, of the guard. Each section has its own width, height and curve across the tire. Speedwell offers about 30 universal sections. Pick the section that matches the width of your tire and the look you want. Each listing gives the well width and height, so you can compare them with your old guard. Every MC1 universal fender, MC2 universal fender and MC3 universal fender lists these measurements.

The R number is the radius of the guard in inches. An R14 3/4 guard has a 14.75-inch radius. Speedwell measures radius from the center of the wheel spindle to the center line of the mudguard. Production guards come in 1/8-inch steps, which is why sizes like R15 3/8 exist. On a universal guard, the radius matters most: it sets the clearance between the guard and the tire, and how the guard looks on the bike.

You need three measurements: section, radius and length. With the bike upright and the tire inflated, measure from the center of the axle to where you want the inside of the guard to sit. Then add clearance for suspension travel, chain movement and mud, especially at the rear. Measure the width of your tire to choose the section, and measure your old guard or the stays to choose the length. Autocycle Engineering’s guide says length is less critical than radius on a universal guard, because you can trim a guard but you cannot change its radius. If you are unsure, contact our tech support team with your measurements before you order.

The length is the arc length of the guard. A 36-inch guard is common for front fenders and short, bobbed or café-style rear guards. A 48-inch guard wraps further around the wheel, which suits a full rear fender or a front guard you plan to trim to length. If you are building a custom bike, ordering the longer guard and cutting it to fit gives you more choice over where it ends?

Mild steel guards are roll formed to the correct section and come bare, ready for you to prime and paint. Choose steel if you want to paint the fender to match your tank or for an original-style restoration. Alloy guards are made from 1.2mm aluminium. They are lighter, will not rust and can be polished to a bright finish, so they suit café racers and vintage racers. Wipe a steel guard with oil or primer as soon as it arrives, because bare steel rusts quickly.

No. Speedwell universal mudguards come without holes, so you can position the guard for the correct tire clearance before you drill. Fit the guard to your stays, check clearance with the suspension fully compressed, then mark and drill the holes. Deburr the holes and treat bare steel edges before painting. Our workshop tools and motorcycle hardware pages have the tools and fasteners you need to fit them.

Yes, if you choose the right part. Speedwell makes guards to original part numbers for vintage Triumph twins. The Triumph Bonneville Speedwell mild steel mudguard (MBI-S2) is a direct-fit option. For custom builds and modern Bonnevilles, Thruxtons and Scramblers, a universal guard sized by section, radius and length is the better choice. See our body, frame and trim parts for related parts.

Yes. We stock the BSA A50/A65 chromed front pressed-nose mudguard (PN 68-6536) for 1965–1970 models and the BSA A50/A65 chromed rear beaded-nose mudguard (PN 68-6856) for 1967–1970 models. Both are made to original BSA part numbers. Universal Speedwell sections also work on BSA, Norton and other British singles and twins when you match the radius and section.

Yes. Restorers choose Speedwell because the guards come from original tooling and keep the factory profile and channels. Custom builders like the wide range of sections, radii and lengths, which makes it easy to get a tight, even gap above the tire. Pair a polished alloy guard with a New Rage fender eliminator or upgraded lighting and indicators to finish the look. A fender still has a job to do, so leave enough length at the rear to keep spray off you and the riders behind you.

Add the guard to your cart online, or call 720-570-7884 or text 720-260-4271, Monday to Friday, 9 AM to 5 PM Mountain Time. If you know your bike’s original part number, or the section, radius and length you need, our team can find the right guard. See our shipping and returns policy for delivery times and return conditions. Do not drill or paint a guard until you have checked that it fits.