Data sheet
Dimensions & weights
- Wet weight
- 179.3 kg
- Seat height
- 826 mm
- Ground clearance
- 127 mm
- Wheelbase
- 1403 mm
Engine & drivetrain
- Engine
- 744 cc · Parallel twin
- Cooling
- Air cooled
- Output
- 52 hp · 54 Nm
- Transmission
- 5-speed
- Final drive
- Chain
- Fuelling
- Carburettor
Fuel & range
- Fuel capacity
- 13.6 L
- Real world range
- 280 km
Electronics & rider aids
- Ride modes
- None
- Cruise control
- No
- Traction control
- No
- ABS
- No
- Heated grips
- No
- Heated seat
- No
Service intervals
- Service interval
- 5,000 km
- Chain lube
- every 500 km
Protection
- Bash plate
- None
- Radiator guard
- No
- Oil cooler guard
- No
- Hand guards
- No
Consumables & service specs
Every value carries its source.
Tyres
- Front
- 3.25 x 19Trojan Classics — 1973 Triumph Unit 750 Technical Data
Tyre pressures
- Front — solo
- 24 psiPer Hermit.cc Triumph 650/750 maintenance manual (1.68 kg/cm2); note the later 1978 T140E handbook gives a higher 28psi front figure — the earlier 24psi figure is used here as more contemporaneous to 1973, but a documented running change to higher pressures likely occurred later in production.Hermit.cc Triumph Unit Twin Maintenance Manual
- Rear — solo
- 25 psi1973 Unit 750 factory technical data, solo cold pressure.Trojan Classics — 1973 Triumph Unit 750 Technical Data
Engine oil
- Viscosity
- SAE 20W-50 (multi-grade, later spec); non-detergent straight-40 was period-correct at introductionHermit.cc manual notes multigrade 20W-50 for later unit-construction 650/750 models; earliest 1973 production likely still specified non-detergent single-grade oil per period British practice, with a 3,000-mile change interval on non-detergent oilHermit.cc Triumph Unit Twin Maintenance Manual
- Capacity
- 3.4 l7.25 Imperial pints, later-model oil-in-frame tank capacity per Hermit.cc manual; the 1973 factory technical data sheet separately states oil tank capacity as 4.8 US pints (approx. 2.3L) — a discrepancy likely reflecting different measurement conventions or a running change; both figures are presented for transparency, with the Trojan Classics 1973-specific sheet given priority as the primary year-specific sourceTrojan Classics — 1973 Triumph Unit 750 Technical Data
Brakes
- Fluid type
- DOT 3Front disc brake hydraulic system (10in Lockheed 2-piston caliper introduced on 1973 TR7RV); per later 1978 T140E handbook, likely consistent for 1973 given the shared Lockheed disc system1978 T140E Owner's Handbook (classicbike.biz)
Forks
- Oil capacity
- 190 mlPer front fork leg, per 1973 factory technical data sheetTrojan Classics — 1973 Triumph Unit 750 Technical Data
Final drive
- Chain
- Primary: Triplex, 84 links; Secondary (rear drive): 5/8 x 3/8in, 107 linksNew-for-1973 triplex primary chain (upgraded from earlier duplex); enclosed oil-bath primary chaincase, open non-O-ring rear chainTrojan Classics — 1973 Triumph Unit 750 Technical Data
Spark plugs
- Type
- Champion N3Also cross-referenced as Champion N-3 in Hermit.cc manualTrojan Classics — 1973 Triumph Unit 750 Technical Data
- Gap
- 0.635 mm0.025inHermit.cc Triumph Unit Twin Maintenance Manual
- Quantity
- 2Parallel-twin engine, one plug per cylinderTrojan Classics — 1973 Triumph Unit 750 Technical Data
Fuel
- Minimum octane
- 97 RON (period premium leaded); modern equivalent 91-93 AKI premium unleaded plus lead-substitute additive recommended for non-hardened valve seatsPer 1978 T140E owner's handbook minimum octane spec, carried forward as a reasonable reference for the closely related 1973 unit-construction 750 engine1978 T140E Owner's Handbook (classicbike.biz)
Tyre Library
Tyres for this bike and year
Start with this motorcycle’s front and rear sizes. Open a tyre to check the complete fit for this exact bike and year; a size or original-equipment report alone does not confirm it.
Sizes match, but more needs checking
Bridgestone BATTLAX BT46
Matching front and rear sizes exist, but some motorcycle requirements or the front-and-rear pairing still need confirmation.
Still needs checking: source information, load rating, any manufacturer restrictions, front and rear pairing, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
Sizes match, but more needs checking
Metzeler Lasertec
Matching front and rear sizes exist, but some motorcycle requirements or the front-and-rear pairing still need confirmation.
Still needs checking: source information, load rating, any manufacturer restrictions, front and rear pairing, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
Sizes match, but more needs checking
Continental RB 2 / K 112
Matching front and rear sizes exist, but some motorcycle requirements or the front-and-rear pairing still need confirmation.
Still needs checking: source information, load rating, any manufacturer restrictions, front and rear pairing, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Anakee Adventure
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Anakee III
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Anakee Road
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Anakee Wild
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Angel GT
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Angel GT II
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Angel ST
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLAX Adventure A41
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone Battlax Adventure Trail AT41
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLAX Adventurecross AX41
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLAX Adventurecross Scrambler AX41S
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLAX BT-45
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLAX Sport Touring T32
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLAX Sport Touring T33
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLE WING BW501 / BW502
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone BATTLECRUISE H50
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Avon Cobra Chrome
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Commander II
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Commander III Cruiser
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Commander III Touring
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiClassicAttack
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiEscape
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiLegend
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiMotion
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiRoad
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiRoadAttack 4
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiTour
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental ContiTrailAttack 3
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Cruisetec
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Diablo Powercruiser
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Enduro 3 Sahara
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Mitas Enduro Trail-ADV 2
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Mitas Enduro Trail-XT+
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Mitas Enduro Trail+
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone EXEDRA G853 / G852
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone EXEDRA MAX
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
IRC GP-21F / GP-22R
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Heidenau K60 Scout
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Dunlop K750
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Karoo 4
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Karoo Street
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler ME 888 Marathon Ultra
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli MT 21 Rallycross
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli MT 60 RS
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Night Dragon
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Road 5
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Road 6
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Road 6 GT
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Road Classic
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Road W GT
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Roadtec 01
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Roadtec 01 SE
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Roadtec 02
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Roadtec Z8 Interact
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Scorcher 11
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Scorcher 31
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Michelin Scorcher Adventure
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Scorpion Rally
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Scorpion Rally STR
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Scorpion Trail II
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Pirelli Scorpion Trail III
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Avon Spirit ST
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Mitas Terra Force-R
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental TKC 70
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental TKC 70 Rocks
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental TKC 80
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Continental TKC 80²
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Tourance
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Metzeler Tourance Next 2
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
No matching front and rear pair
Bridgestone Trail Wing TW101 / TW42
No complete front and rear size pair in this tyre range matches the selected bike and year.
Still needs checking: load rating, any manufacturer restrictions, approved rim width, speed rating, tube or tubeless setup, a named tyre match.
What breaks first and where.
High oil pressure / oil-in-frame tank pressure relief issues
MinorOccasionalOwner reports on the oil-in-frame Tiger/Bonneville twins describe instances of unexpectedly high oil pressure readings related to the frame oil tank's pressure release valve and feed configuration, particularly on 1973-model-year bikes. The pressure relief valve is located at the front of the engine; typical readings are approximately 80psi cold start, 65-80psi hot running, and 20-25psi hot idle — deviations from this range prompted forum troubleshooting discussions.
Symptoms
- Oil pressure gauge reading persistently above the expected hot-running range
- Uncertainty distinguishing a genuine relief-valve fault from a normal reading for the oil-in-frame design
Field repairableYes — Inspect and clean the pressure relief valve at the front of the engine; verify against the documented normal ranges (approx. 80psi cold start / 65-80psi hot running / 20-25psi hot idle) before assuming a fault.
Oil-in-frame reservoir leak points
ModerateCommonThe 1971-onward 'oil-in-frame' (OIF) Triumph twins use the steel frame's front downtube/backbone structure as the engine oil reservoir. The 1973-on frames used a different reservoir oil feed and gauze strainer configuration than the initial 1971-72 OIF design. Common leak points occur at the frame-to-oil-tank joints, the filler cap seal, and the return-pipe connection at the base of the frame; a further production change during 1977 extended the rigid oil return pipe to a position below the airbox. On the smaller-displacement 650 OIF frames, cracking around the swinging arm pivot was also a source of leaks, though the 750 frames (as used on this 1973 Tiger) are described by enthusiasts as notably improved in this respect.
Symptoms
- Oil seepage at frame downtube joints or filler cap
- Oil staining around the frame backbone near the steering head or swingarm pivot
- Gradual loss of oil level in the frame reservoir
Field repairableYes — Reseal frame joints and filler cap with fresh gaskets/sealant; inspect and clean the gauze strainer at the tank outlet; on 650 frames specifically, inspect the swingarm pivot area for cracking, which requires more extensive frame repair or replacement if found.
Where to find things
Common locations for jacks, filters, fluids and fuse boxes. Follow the reference link when a picture helps more than words.
Engine oil fill
Engine-oil filler and level-check point on the engine; use the referenced owner-manual level procedure and keep contamination out of the opening.
ReferenceBrake fluid reservoir
Front reservoir at the handlebar master cylinder and rear reservoir beside the rear master cylinder; use the manual's motorcycle attitude for level checks.
ReferenceBattery
Under the seat, in a side-mounted battery carrier within the oil-in-frame backbone structure
Reference