BMW forks onto a Commando.

[Simon Ratcliff]

Hi, looking for advice/experience on a project I'm about to start.

The project is grafting on the front end suspension off a BMW K1200R Sport on to a 1970's Norton Commando frame. The reason is to take advantage of the superior design of front suspension and obviously ditch the telescopic Roadholders - I think telies should have been binned decades ago. The suspension is based on the Norman Hossacks design featuring two wishbones (lower and upper). The fork legs are basically a inverted solid U-tube shape, suspension is via a single shock mounted on the lower wishbone and a point on the frame.

Any advice appreciated.

[iansoady]

The Commando frame was designed to use conventional teles, and even Norton got it wrong with the early ones which suffered frame breakage near the steering head. I would have thought that the frame would need a complete redesign to use the telelever layout as you need a point to anchor the lower wishbone fulcrum that it obviously non-existent on the Norton.

[Simon Ratcliff]

Ian, thanks for the comments.

Totally agree with your points regarding redesign of the frame, but only in the steering head area to support the lower and upper wishbone - it's the duo-lever design not the paralever. http://ridermagazine.com/wp-content/uploads/2005/09/2006_BMW_K1200R_front_wheel_Frame1.jpg

At the moment the idea is to remove the steering head entirely. Before cutting I'll check the swinging-arm axis is perpendicular to the frame centre-line and correct if necessary. The swinging-arm axis will then be the datum to work from to establish the new mounting points for the wishbones are parallel to that.

I'm aware that tele's were originally fitted to Commando's but as long as the front wheel trail and wheel base is fairly close to the original I don't for see any problems, unless anybody knows better - I'd be grateful for any more input.

[Rex]

Anything's possible given enough time and engineering nous, but it seems like one quick step in making a beautiful bike into a right ugly mongrel.

[Simon Ratcliff]

Beauty is subjective, personally I think the BMW design is a nice looking bit of kit. That it will out perform any telescopic is the main reason for the swap and performance takes priority over looks as the bike regularly does annual mileages of 5 - 6,000 miles. It dosen't do shows and I like mongrels!

[Simon Ratcliff]

More on the reasoning of the duo-lever suspension choice over telescopics. I'm of the opinion that nature is the greatest engineer. Millions, if not billions of years in research and development which continues to this day. The Norman Hossack design uses natures designs. The human leg, for example, consists of load bearing members (bones) articulated joints (ankles, knees) and spring/damper units (muscles).

I cant think of any example in nature where a telescopic design has been used to provide load bearing with sprung damping.

[Rex]

You do whatever you want, but if you want a seriously well-engineered motorcycle, why not just buy the whole BMW and have done with it?
The tele forks are of their time, the Commando engine stretches back to the 1940s, and the Isolastics back to the 1960s. You think the bike is going to be somehow transformed into something it's not by grafting the BM front end on?

[mini-me]

Call me rude and cynical, which I am, but if you have the skill to safely carry out these massive modifications, why are you asking other people instead of doing it and then showing it off?
Do you think this is some modification that's done a lot?

I am sorry if it offends you but I don't really care, bike forums are full of theoretical mechanics dreaming up these schemes trying to make a silk purse out of a sows ear, or a GPwinning bike out of a 1956 Pride and Clarke reject.
Do it, ride it,then show it off if you don't die on it.

By the way have you read your insurance quote where its asks "has this machine been modified in any way?"

Good luck, bring it back later.

telescopic design has been used to provide load bearing with sprung damping.

It's a machine not an animal, and 5000k mile a year [or 95 a week] is nothing, I used to do well over a 1000 a week as a long distance despatch rider in the 1980s, on a RT BMW, and a Honda CX, funnily enough both had the despised tele forks.

[Simon Ratcliff]

I'm not stupid enough to think I cant learn things from somebody with more experience or knowledge than myself, hence the request for advice. I like my Commando. I've owned it since 1987 and have always improved things that I was not happy with, hence the BMW front end.

The topic has obviously annoyed both of you so why not stop reading any further postings. If you don't really care why the f#ck are you posting?

[mini-me]

Another smart arse tetchy one.

If you don't really care why the f#ck are you posting?

why are you showing off with your wet dreams?

you had good advice, viz why bother?
try one of the blobber custardizing sites,they are good at building junk out of good bikes.

Or better still the Norton Commando site they'll love you.

[Simon Ratcliff]

'Why bother'? was a question, not advice.  I'm bothering because the Hossack fork design gets rid of all the problems associated with telescopics. It'll make it a better bike to ride, faster into and through corners, smoother all round. First thing to go when I bought the bike was the appalling front brake (Why bother?) I've now got switch gear and handlebar controls inc. master cylinder off a Honda CBR600 - far better than the standard junk and cheaper.

Tetchy? Your the one who chimed in whingeing about people modifying their bikes. There's too many people like yourself on forums harping on about what they used to do - probably because now they do sweet F.A, apart from droning on about when they were droning up and down motorways doing a 1000 miles a week. I bought my bike to ride, and if, in my opinion things need changing then they get changed. Couldn't care less about the sanctimonious arses towing bikes to rallies and then criticising somebody who's ridden their bike there because they've got Japanese spark plugs or non-standard light bulb.

Get the picture? 

 

[mini-me]

Get the picture? 

 Oh yes. The picture of you I had already is spot on.

I'm, nor is anyone else  whinging about what you do to your bike I couldn't care less.

Couldn't care less about the sanctimonious arses towing bikes to rallies and then criticising somebody who's ridden their bike there because they've got Japanese spark plugs or non-standard light bulb.

yep, that about confirms what I thought, you belong on a blobber site. You are just one of those who want to show off  their mechanical wet dreams and do not have the skill to do it.
Do come back soon and show me how wrong and misguided I am when you have finally carried out all these modifications in order to do your 95  ::)miles a week.
I will then grovel accordingly, but don't be too long son, 52 years of riding experience under my belt  this year, I shan't be around for ever.

[Simon Ratcliff]

Whatever you say. Hopefully some one will post something relevant to my original question.

[mini-me]

Hold your breath while waiting.

[whipirongeoff]

Simon, not being nasty, but when I first read your post I thought you was joking. It's sort of like coming here and saying ... Hey I've got a featherbed manx norton that I'm going to put a cantilever rear end on. The reaction you received was justified when you want to perform an abortion on a classic motorcycle. I only hope you're not planning to slice the cylinders down the middle, and stick them out each side of the motor.