Front Fender - 18 inch wheel (2020)

Hi All -

I recently purchased a MKIII Commando that had been fitted with 18 inch CMA cast wheels and no front fender. The wheels are like new with only 73 miles on them, as the bike had been stored for 30 years.

I am looking for suggestions regarding a front fender that might work with an 18 inch front wheel as I would like to keep the CMAs on the bike.

Thanks for your suggestions!

Tom

check cNw website,,,,,i believe their front fender works well with an 18

To me, the stock fender setup doesn't look that bad. Sun 2.15 x 18 rim. Metzler Lasertec 100/90 18 tire.

You can always use a cheapo fiberglass fender like the one I have used for 43 years... It's lighter than a metal fender so it has a lower unsprung weight but it defiles your commando with the stench of non-stock parts, which is, of course, a sin...


here's 2 pictures with the fiberglass fenders in this thread... original and evolved into an interstate

Remember the original fender includes a fork brace that resists twisting forces.

I have what appears to be a chromed steel replica of a standard commando front 850 guard, but for a smaller wheel. Came on a bike that I bought and refurbished. I swapped it for standard SS for 19". can send you a pic if you like

I've collected some data pertinent to fitting an 18" rim and tyre and a suitable fender (mudguard) on a Commando, particularly the later models.

Commando models came off the assembly line with Dunlop K81 tyres, so I will use this tyre as reference.

K81/TT100 4.10Hx19 has a rolling radius of 674/2 = 337 mm.
K81/TT100 4.10Hx18 has a rolling radius of 651/2 = 325.5 mm.

1973-77 stock fenders had a length of 35" (889 mm), a secant line length (aka end to end length) of 26.5" (673 mm) and a width of 4.75" (20.5mm). The calculated blade radius is 354 mm and the enclosed angle is 2.512 radians = 144 degrees. Fender thickness is neglected in this calculation. The theoretical static gap between tyre and fender is 17 mm.

A fender which would look the same as the the stock fender and having the same gap needs to have a blade radius of 342.5 mm. The enclosed angle will be the same, 144 degrees. These data correspond approximately to a fender length of 860 mm and a secant line length of 650 mm.

I have yet to find a fender matching these data. The following fender comes close; it is too short (the enclosed angle is 67 degrees), but the blade radius calculates to 342 mm, so it will fit the tyre very well.

I hope this exercise is of interest to some.

- Knut

I just discovered the new BSA Goldstar silver shade model sports chromed or stanless 18in fenders and front/aft stays. Tyre is 100/90 R18. It think it will fit the Commando well.

- Knut

I’ve a Dunstall front mudguar / fender on my 18” Dymag . Drilled new mounting holes to close the gap and used some 18 gauge alloy to create an integral brace…works for me.