Ultimate Guide: Can You Swap Crutch Straps Between FIA 5/6-Point Harness Brands?
Harness question
A question we are asked regularly: can I use a crutch strap from one harness brand with the lap and shoulder straps of another? Usually it comes up when a sub strap is worn, cut or lost, and the rest of the harness still looks fine.
Our answer is no. An FIA harness is approved as a complete harness, and every part of it carries its own label. A strap from another make, or even another harness of the same make, turns it into something that was never tested or approved. This guide explains why, what the crutch strap does, and what to do if yours is damaged. Your championship's rules and the scrutineer have the final say on what is accepted in your car.
- FIA harnesses are homologated as a complete harness, not as separate straps
- Each part of an FIA harness carries its own FIA label
- Buckles and strap ends are specific to the maker and model
- The crutch strap stops the occupant sliding under the lap belt
- A worn or damaged strap means a new harness, or a genuine part from the maker if they offer one
- Never mix straps or buckles between brands or between harnesses
What is on this page
Why you cannot mix harness brands
The approval is for the whole harness. An FIA harness is tested and homologated as a complete harness: shoulder straps, lap straps, crutch straps, buckle, adjusters and fittings together. Each part carries an FIA label. Swap one part for another and the harness in the car is no longer the one that was approved.
The hardware is not the same. Buckles from Sparco, TRS, OMP, Schroth and Sabelt can look alike, but the tongues, latches and release mechanisms are made for each maker’s own harness. A strap end from one maker in another’s buckle may not lock properly, or may release when it should not.
The dates will not match. FIA harness labels carry a year after which they are no longer valid for competition. A strap from a different harness has its own date, and a harness made from parts of different ages has no single valid date.
Scrutineers check the labels. A harness with mismatched labels, or a strap with no label, is likely to be rejected at scrutineering.
What the crutch strap does
The crutch strap, also called the sub strap or anti-submarining strap, runs from the buckle down between the legs to an anchor below the seat. In a frontal impact it holds the lap belt and buckle down across the pelvis, so the occupant cannot slide forward and under the lap belt. That sliding, called submarining, can cause serious abdominal injury.
Five point harnesses have a single crutch strap. Six point harnesses have two, which run under the thighs and spread the load. Either way, it is a load bearing part of the harness, not an extra. A crutch strap made for a different buckle, or at a different length, will not do that job the way the harness was tested to.
What to do if your crutch strap is worn or damaged
If a crutch strap is frayed, cut, stiff, faded or has damaged stitching, or its label is missing or unreadable, stop using the harness in competition. Your options are:
- Replace the harness. The straightforward answer, and the one we recommend.
- Ask the maker. Some makers can supply a genuine replacement part for their own harness. Contact us with the make, model and label details and we will ask. If they cannot, a new harness is the answer.
Do not substitute a part from another brand, a generic strap, or a strap from another harness, even one of the same make and model.
It is worth checking the whole harness when one strap has worn. If the crutch strap has been rubbing on the seat or the floor, look at the lap straps and buckle as well, and check the expiry year on the labels. Our guide to how long FIA harnesses last explains the labels and dates.
Quick answers
| Question | Answer |
|---|---|
| Can I use a crutch strap from another brand? | No |
| Can I use a crutch strap from another harness of the same model? | No; the parts belong to one harness |
| Can I replace just the crutch strap? | Only with a genuine part from the maker, if they supply one |
| Can I mix buckles and straps between brands? | No |
| Can I add straps to turn a four point into a six point? | Only if the maker offers that as an approved option for that harness; otherwise buy a six point |
Complete FIA harnesses
The simplest way to avoid all of this is a complete harness from one maker, in date and correctly fitted. We sell six point FIA 8853-2016 harnesses from Schroth, Sparco, TRS, OMP and Sabelt, among others. If you use a HANS or other head and neck restraint, check the listing says the harness suits it; two inch shoulder straps are made for use with one.
Garreth’s advice is to buy the harness for the seat and the car together, so the slots, anchor points and strap lengths all work. Our guides to four point versus six point harnesses and the Sparco six point range are good places to start.
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Can I swap crutch straps between harness brands?
No. FIA harnesses are approved as complete harnesses, and each part carries its own label.
Can I buy just a replacement crutch strap?
Only a genuine part from the harness maker, where they offer one; otherwise replace the harness.
What does a crutch strap do?
It holds the lap belt down across the pelvis so the occupant cannot slide under it in a frontal impact.
Will a scrutineer notice mixed harness parts?
Scrutineers check the labels on each part, so mismatched or missing labels are likely to be rejected.
Is a worn harness safe to keep using on the road?
We would replace any harness with worn or damaged straps, whatever it is used for.
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The safe answerOne maker, one harness
Keep every strap, buckle and fitting from the same, complete, in date harness.
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