Fork and front end lengths and steering stem sizes – Honda CX500, GL500, CX650, GL650, CBR600RR etc.

Fork top refers to the top of the chrome tube, not including the height of any fork cap or adjusting screws etc.

Top triple vertical offset refers to the “gullwing” design of top triple clamp where the clamps are lower than the stem top; we will find a photo to explain. Shorter forks are lighter, and you can get the same functional height out of a shorter pair of forks by lowering the top triple tree clamp relative to the stem.

Things like axle diameter are also important if you wish to keep the wheels from your original front end; there are many more factors to consider when it comes to keeping the front wheel but that is outside the scope of this article.

Orientation refers to the orientation of the forks – whether they are right side up or upside down. Right side up means that the chrome stanchion is at the top of the assembly, upside down (shortened to USD or sometimes called inverted) means that the chrome sliders are at the bottom. There may be an advantage to having USD in that there is lower unsprung weight but they seem more commonly lusted after for their appearance!

Pay particular attention to the steering stem figures if you are considering a new front end – this can be the difference between simply getting a bearing kit or having to press out/in a steering stem (or have a stem modified or fabricated). This is part of the reason why some front end swaps are considered easier than others – if the stem is comparable and all you need is bearings it can be a whole lot easier. Note that there’s more to it than just the stem length – if the positioning of the two threaded sections on the upper part of the stem are different the length being the same may not help you.

Note that with some new forks there are top-out springs which prevent the fork from “relaxing” to it’s full length. Simply letting the weight of the wheel pull the forks down (i.e. lifting the front wheel off the ground while the forks are still on the bike) should be enough to get an accurate measurement of the length of the forks.

Click on any heading (somtimes you have to click twice to get it started) to sort the table by that column.

We are measuring the steering stem length from the flat surface that the bearing sits against (i.e. where the stem enters the lower triple) to the very top of the stem.

In the future we are planning to add a calculator where you can put in which front end you are swapping to, which bike you have and it will provide a figure for how it will alter your rake/trail. That’s in the works.

 

Finally, why should you care about the overall length of the forks when you are considering front end conversions? Picking a front end that is overall longer or shorter than your existing one will change the rake and trail of your motorcycle, which could profoundly affect the handling – and not always for the better. Scroll down for the table.

 

Year Model Fork diameter Fork top to axle center Orientation Axle diameter Steering Stem Diameter Steering Stem Length Top Triple Vertical Offset Wheel size Tyre size Tyre type Notes
1978 CX500 33mm Normal 15mm 223mm 19″ 3.25S (~100/90) Bias Ply
1979-1980 (USA)
1979-1981 (AU)
CX500 Custom 33mm Normal 223mm 19″ 3.50 Bias Ply
1981-1982 CX500 Custom (USA) 35mm 760mm Normal 19″ 3.50 Bias Ply Leading axle
1979-1980 CX500 Deluxe 33mm Normal 15mm 19″ 3.50 Bias Ply
1982 CX500E Sports 37mm Normal 15mm 18″ 100/90 Bias Ply TRAC on left fork
1982 CX500 Turbo 37mm Normal 15mm 18″ 100/90 Bias Ply TRAC
1981-1982 GL500 35mm 820mm Normal 15mm 222mm 19″ 3.50 100/90 19 Bias Ply Steering head height 177mm (ref)
1981-1982 GL500 Interstate 35mm 845mm? (ref) Normal 15mm 222mm 19″ 3.50 100/90 19 Bias Ply Steering head height 177mm (ref)
1983 CX650 Eurosport 37mm Normal 15mm 18″ 100/90 Bias Ply TRAC on left fork
1983 CX650 Turbo 37mm Normal 15mm 100/90 Bias Ply
1983 CX650 Custom 39mm Normal 19″ 100/90 Bias Ply Leading axle
1983 GL650 37mm 806mm (ref)
795mm (ref)
Normal 15mm, 241mm long 27mm 222mm ? 3.50 Bias Ply Steering head height 177mm (ref)
1983 GL650 Interstate 37mm 795mm (ref) Normal 27mm 222mm 3.50 Bias Ply Steering head height 177mm (ref)
1991-1994 CBR600F3 41mm 780mm (ref) 17″ 120/60 17
2000
2001
2002
CBR929RR/CBR900RR 43mm 725mm (ref) USD 222mm (ref) 17″ 120/70 17
2003 CBR954RR 43mm 725mm (ref), 717.55mm (ref) USD 25mm, 171.45mm long 30mm at base, 26.5mm mid-up 222mm (ref) 17″ 120/70 17 Stiffer than CBR929RR. Front forks have stepless preload adjustment along with compression and rebound adjustment.
Top stop of the CX neck has to be removed, bottom has to be shaved down a little
2001 CBR600F4i 43mm 750mm (ref) 17″ 120/70 17
2003 CBR600RR 45mm 725mm (ref) 17″ 120/70 17
2004-2005 CBR1000RR 43mm 710mm (ref) USD 17″ 120/70 17 Radial
2005 Honda CBR600RR 41mm 680mm (ref)
712mm (ref)
USD 22mm 17″ 120/70 ZR17 Radial Inverted HMAS cartridge fork w/spring preload, rebound and compression damping adjustment
2006-2007 Honda CBR1000RR 43mm 720mm USD 17″ 120/70 ZR17 Radial
2006 Honda CBR600RR 41mm 680mm (ref)
712mm (ref)
USD 22mm 17″ 120/70 ZR17 Radial Inverted HMAS cartridge fork w/spring preload, rebound and compression damping adjustment
2007 Honda CBR600RR 41mm 718mm (ref, ref)
710mm (
ref)
USD 17″ 120/70 ZR17 Radial Inverted HMAS cartridge fork w/spring preload, rebound and compression damping adjustment
1974-1979 Honda GL1000 Goldwing 37mm 785mm (ref) Normal 19″ 100/90 19 Bias Ply, Tubes
? Hyosung GT250 and GT250R 41mm 775mm USD 217mm Zero 17″ 110/70-17 54H Radial, Tubeless Shorter than CX500, not many threads for top nut – requires sleeve for one bearing
1998-2001 Yamaha YZF-R1 41mm 740mm (ref) USD 17″ 120/70 ZR17 Radial
2002-2003 Yamaha YZF-R1 43mm 725mm (ref) USD 17″ 120/70 ZR17 Radial
2014 Triumph Street Triple R 41mm 723.5mm (ref) USD ? 30mm 17″ x 3.5″ 120/70 ZR17 Radial Adjustable for preload, compression and rebound
2006-? Yamaha R6 ? 745.5mm USD 21mm left, 28mm right Top 29mm, bottom 30.5mm 232mm ? ? ? ? 210mm center to center (forks). 108mm radial brake caliper mount. Fork legs 160mm apart.
2004 G
SXR600
Top triple 50mm, lower 51.5mm 720mm USD 25mm 30mm at top and bottom bearings 233mm 30mm 17″ 120/70 R17 Radial Thanks Tim!

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