4SR Seam Technology
Built for Safer Racing Suits
At 4SR, we've always put a heavy emphasis on safety. We wanted to build something new, better, and smarter.
Even our first patent was about protecting the rider — specifically the knee and how knee protectors are mounted inside motorcycle trouser legs. Continuous development is often a demanding and complicated road, but comfort and safety have always come first in how we develop 4SR gear.
We regularly review the best protectors currently available in the segment and select the most suitable and safest options for our products. We test leather to make sure we're genuinely offering our customers the best available, and we listen closely to our racers, feeding what we learn straight back into production.
The result is first-class motorcycle racing suits with more than 18 protectors, leather that exceeded the strictest requirements of EN 13595-2:2002 Level 2 abrasion resistance testing by 60%, and a comfortable cut that delivers outstanding mobility even in extreme riding positions.
We've continuously refined the cut of our one-piece and two-piece racing suits for more than 12 years, always working to bring our customers an even better product.
After years of development, it was time to revisit one of the most fundamental parts of motorcycle suit construction: the seams.
Why Seams Matter in Motorcycle Racing Suits
So, what is a motorcycle racing suit actually built from?
Several dozen pieces of leather and other materials are stitched together following a precisely defined process. And because a chain is only as strong as its weakest link, the seams matter just as much as the quality of the leather, the Kevlar stretch panels, and every other material and component.
There are several types of seams used in the construction of protective motorcycle gear.
A simple seam — completely inadequate from a safety standpoint — is just one line of stitching running through two layers of material, simply joining them together.
A simple seam has no place on exposed areas or anywhere contact with the road is expected during a crash.
When sliding on tarmac, the thread can burn through, the entire simple-seam construction can fail, and a hole can open exactly where the seam was.
Double and Triple Safety Seams
Most riders have heard of double and triple seams.
These are safety seams designed to help prevent a protective garment from tearing open on impact or during a slide. Triple seams are generally considered among the safest, but they are more demanding to produce, which is why they are not used as often in protective motorcycle gear.
One of the main advantages of a triple seam over a conventional double seam is that it lies flatter, making it more comfortable for the rider.
This type of seam is often used in areas such as the back, elbows, crotch, or tailbone, where both protection and freedom of movement are especially important.
The 4SR Four-Times-Stitched Safety Seam
At For Street Racing, however, the number in our seam name stopped meaning simply the number of visible stitch lines a long time ago.
Our double-seam construction is actually stitched four times.
From the outside, you probably wouldn't notice anything unusual. Just like a standard double seam, only one line of stitching is visible.
The other three lines are hidden inside the construction.
You'll now find this reinforced, four-times-stitched safety seam in your own 4SR motorcycle racing suit too. The new stitching process was rolled out across our production last year.
Standard Double Seam
4SR Double Seam
Protection During a Crash
In a crash and the slide that follows, only the single outer line of stitching is directly exposed to the road surface.
That outer line may eventually be ground away, but the inner stitching never comes into direct contact with the tarmac and continues to hold the leather together.
In a higher-speed crash, however, the slide can continue for much longer. Real-world road surfaces are also far from smooth.
Potholes, stones, broken surfaces, and other irregularities can create sharp edges that catch on folded leather and place enormous stress on the stitching.
With only one inner line of stitching, a sufficiently sharp edge could tear through it and allow the suit to open.
That's why the second and third internal lines of stitching have to sit at exactly the right distance from one another.
The positioning is designed so that no single sharp edge can easily tear through two lines of stitching at the same time.
That additional backup at this critical point is what takes 4SR racing suit construction to another level.
Developed with Professional Racers
The fact that we take this work seriously is also reflected in the racers we have the opportunity to work with.
4SR has supplied racing leathers to riders including Karel Hanika, Oliver König, American Flat Track champion James Rispoli, Jack Kennedy, and Hannes Soomer.
For five consecutive years, we have also dressed Alastair Seeley, holder of the record for the most North West 200 victories.
The experience and feedback gained from professional racing continues to feed directly into the development of 4SR motorcycle racing suits and protective motorcycle gear.
