Tefzel wire is the standard choice for professional motorsport wiring harnesses. The insulation material is ETFE (ethylene tetrafluoroethylene) — a fluoropolymer related to PTFE, but lighter and with better mechanical toughness. In motorsport and mil-spec applications, cross-linked modified ETFE is used: radiation cross-linking tightens the polymer structure, improving abrasion resistance and cut-through performance without adding weight.
The primary mil-spec designation is MIL-DTL-22759/32 (SAE AS22759/32). Raychem (now TE Connectivity) manufactures the same wire under the brand name Spec55, part series 55A0111. Both names refer to the same specification: tin-plated annealed copper conductor, cross-linked modified ETFE insulation, rated to 150°C and 600 V.
Note: “Spec55” is a TE Connectivity product family that covers multiple SAE AS22759 sub-specifications. XTRA Motorsport stocks M22759/32 — the thin-wall, tin-plated, 150°C variant. For the silver-plated 200°C variant (also sometimes called Spec55 by builders), see the sub-specification section below.
Per SAE-AS22759/32 (OD values are min–max per specification). Working current is the recommended safe continuous load for a single conductor in free air with a 30°C temperature rise above ambient — derived from the Marmon Aerospace & Defense ampacity table. Bundle derating: ×0.72 for 3 conductors, ×0.53 for 7 conductors. DC resistance values per MIL-DTL-22759/32 (maximum, at 20°C).
AWG
Stranding
OD min–max (mm)
Conductor (mm²)
Weight (g/m)
DC resistance (Ω/1000ft)
Working current
12
37/28
2.54–2.69
3.31
29.3
2.02
27 A
14
19/27
2.08–2.24
2.08
19.3
3.06
21 A
16
19/29
1.68–1.78
1.31
12.4
4.81
15 A
18
19/30
1.47–1.57
0.82
9.7
6.23
13 A
20
19/32
1.22–1.32
0.52
6.4
9.88
10 A
22
19/34
1.04–1.14
0.33
4.2
16.2
8 A
24
19/36
0.89–0.99
0.21
3.0
26.2
6 A
26
19/38
0.76–0.86
0.13
2.1
41.3
4 A
Part number suffix: M22759/32-{AWG}-{colour} and Spec55 55A0111-{AWG}-{colour}, where colour follows MIL-STD-681: 0=Black, 1=Brown, 2=Red, 3=Orange, 4=Yellow, 5=Green, 6=Blue, 7=Violet, 8=Grey, 9=White. Two-digit suffix (e.g. -09) = white with black stripe.
AWG Selection by Circuit Type
CAN bus (CAN High / CAN Low): use Spec55 twisted CAN wire (55A0121) — twisted pair construction is required for CAN, not single-core
Main power distribution, high-current feeds: 12 AWG
Shielded trigger and knock sensor wiring: use M27500 shielded wire — M27500 uses M22759/32 conductors with an aluminium foil shield
M22759 Sub-Specifications
The SAE AS22759 family contains multiple sub-specifications. The difference that matters most for motorsport is conductor plating and temperature rating:
Spec
Conductor plating
Insulation wall
Temp rating
Typical OD at 22 AWG
XTRA stock
Primary use
M22759/16
Tin
0.013 in (thick)
150°C
~1.35 mm
No
OEM seal compatibility, abrasion-prone zones, street builds requiring standard seal bore fit
M22759/32
Tin
0.005 in (thin)
150°C
1.04–1.14 mm
Yes
Professional motorsport harnesses — Autosport, Souriau, Deutsch connectors
M22759/33
Silver
0.006 in
200°C
similar to /32
No
200°C zones, enhanced flex life
M22759/44
Silver
0.005 in
200°C
similar to /32
No
Near-exhaust routing, weight-critical 200°C builds — often called “Spec55 200°C”
Practical note: When motorsport engineers say “Spec55,” they may mean M22759/32 (the Raychem product name for the 150°C tin-plated variant) or M22759/44 (the 200°C silver-plated variant). For most ECU harness work, M22759/32 at 150°C is sufficient. Route away from exhaust and turbo outlet heat sources; for circuits that must pass through high-heat zones, specify M22759/44.
M22759/16 vs /32 — the OEM seal question: M22759/16 at 22 AWG (~1.35 mm OD) is close to typical OEM rubber wire seal bore sizes, making it a drop-in fit for factory connectors. M22759/32 at 22 AWG (1.04–1.14 mm) is thinner — it may need a short sleeve of Raychem SCL heat shrink to build up OD at an OEM seal. In motorsport connectors (Autosport, ASL, Souriau 8STA, Deutsch DT/AS), /32 fits correctly without modification.
M22759/32 vs TXL Wire
TXL (SAE J1128) is the standard wire for OEM automotive wiring harnesses. The comparison below is for 22 AWG, the most common gauge in motorsport ECU harnesses.
For a 200-circuit harness with an average 1.5 m per circuit, substituting M22759/32 for TXL at 22 AWG saves approximately 500 g — meaningful for a club or professional racing build.
Per metre: Ordering by the metre gives one continuous cut length — not separate pieces. 5 m ordered = one 5 m length, hand-wound loose.
Full spools: Factory spools are supplied wound. Contact us for spool pricing on high-volume requirements.
Worldwide Shipping
XTRA Motorsport ships M22759/32 Tefzel wire globally via DHL or UPS. Wire is cut to order and dispatched within 1–2 business days.
Region
Carrier
Transit
Europe (EU, UK, CH, NO)
DHL Express / UPS
1–3 business days
United States & Canada
DHL Express
3–5 business days
Australia & New Zealand
DHL Express
4–6 business days
Japan & Asia Pacific
DHL Express
3–5 business days
Rest of world
DHL Express
4–7 business days
M22759/32 Tefzel wire is used by wiring harness builders across the US (IMSA, NASA, SCCA, time attack), Australia (Supercars, WTAC), and internationally for GT3/GT4 OEM programmes. All wire ships with a batch certificate of conformance to SAE AS22759/32 on request.
FAQ
What is the difference between M22759/32 and Spec55?
M22759/32 is the mil-spec designation (SAE AS22759/32). Spec55 is the Raychem/TE Connectivity brand name for wire manufactured to the same specification. The part number series 55A0111 (Spec55) and M22759/32 are functionally identical for motorsport use. However, “Spec55” is also used informally to refer to M22759/44 — the 200°C silver-plated variant. XTRA Motorsport stocks M22759/32 (tin-plated, 150°C). If you need the 200°C silver variant, specify M22759/44 or M22759/33.
What is the difference between M22759/32 and M22759/44 — which should I use?
M22759/32 uses tin-plated copper and is rated to 150°C. M22759/44 uses silver-plated high-strength copper and is rated to 200°C. Both use the same thin 0.005 in ETFE wall, so OD and weight are nearly identical. For the vast majority of ECU harness circuits — sensors, injectors, I/O, power distribution — M22759/32 at 150°C is sufficient, provided the harness is routed away from direct exhaust heat. Use M22759/44 only for circuits that must route through sustained high-temperature zones (exhaust tunnel, turbo outlet area).
Is Tefzel wire the same as PTFE wire?
No. Tefzel is the DuPont brand name for ETFE (ethylene tetrafluoroethylene), which is a different polymer to PTFE (polytetrafluoroethylene, also called Teflon). For motorsport, cross-linked modified ETFE (M22759/32) is preferred over PTFE because it has higher tensile strength (38–48 MPa vs 13–25 MPa for PTFE), better abrasion resistance, and is significantly lighter.
What temperature can M22759/32 wire handle?
Continuous rated temperature is 150°C (−65°C to +150°C). The insulation passes an ageing test at 300°C for 7 hours without failure — this is a production verification test, not a continuous operating limit. For circuits requiring 200°C continuous rating, use M22759/44 (silver-plated conductor, identical wall profile).
Can I use M22759/32 with factory OEM rubber wire seals?
The thin ETFE wall gives M22759/32 a smaller OD than most OEM wire seal bores — at 22 AWG, OD is 1.04–1.14 mm vs a typical OEM seal bore of ~1.3–1.5 mm. A short sleeve of Raychem SCL heat shrink over the seal zone builds OD to fit. For dedicated motorsport connectors (Autosport, ASL, ASU, Souriau 8STA, Deutsch DT/AS/DTP), M22759/32 is the correct wire and fits without modification. If OEM seal compatibility is a priority throughout, consider M22759/16 instead, which has a thicker wall and larger OD closer to OEM seal sizing.
Can I use standard automotive wire strippers on Tefzel wire?
Standard blade strippers are not recommended. The thin ETFE wall (0.005 in) and 19-strand construction require precision strippers with a blade gap matched to the wire gauge. Incorrect stripping nicks the tin-plated strands and reduces pull-out strength at crimp terminations. The correct tool is the Ideal Ergo-Elite Stripmaster (part 55-1987) for 16–26 AWG M22759 wire.
How much weight does M22759/32 save compared to TXL wire?
At 22 AWG, M22759/32 weighs 4.2 g/m versus TXL at approximately 5.95 g/m — approximately 29% lighter. For a 200-circuit harness with an average 1.5 m per circuit, the weight saving over TXL is approximately 500 g. At 20 AWG the saving is approximately 17%. The combination of thinner OD and lower weight makes M22759/32 the standard choice for any build where harness mass is a design parameter.
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