Lowering the front end

Hi,
I would like to lower the front end of my 74 commando approx 1.5 inches to match the lower rear shocks I have installed. I think the bike will look better and it will help me as my legs are short.

What do I need to do to the front end to lower it?

Thanks,

Kber45

I used Atlas fork tubes. As I'm using Gold Valves instead of damper rods, it wasn't much of an issue. You could also go for aftermarket triple-trees that have pinch bolts on both yokes and just slide the fork tube through to your liking (while paying attention to clearance issues, of course).

A change to an 18" front rim will bring you down 1/2" assuming that you keep to the same width of tyre.

Dr_Hiller said:

I used Atlas fork tubes. As I'm using Gold Valves instead of damper rods, it wasn't much of an issue. You could also go for aftermarket triple-trees that have pinch bolts on both yokes and just slide the fork tube through to your liking (while paying attention to clearance issues, of course).

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I assume you are speaking of Race Tech Gold valves?

I didn't think gold valves could be adapted easily. I am getting a pair for a Showa front end off a Sportster I've adapted to a Triumph frame, but didn't think it could be done to Norton forks.

Is it a very involved process? I have no maching tools or skills.

Kber45 said:

Hi,
I would like to lower the front end of my 74 commando approx 1.5 inches to match the lower rear shocks I have installed. I think the bike will look better and it will help me as my legs are short.

What do I need to do to the front end to lower it?

Thanks,

Kber45

Click to expand...

check w/ frank - good stuff

http://www.frankmain.qpg.com/

No, it was a piece of cake. Debby posted a link to the instructions and they're spot on.

They're little buggers that just sit on top of the damper body.


All you have to do is chuck the damper rod and top cap assembly and drill six holes on the damper body.


I had Norbsa's kit in there before, but wanted to lower the front end and couldn't use the longer damper rod. See the difference in Atlas and C'do fork tube length? It's about 1 1/4 ".


They're pretty nice, but I'll need stiffer springs to really push 'em to their limits.

It is true that if you removed an inch form the stanchions on a stock bike without making other changes that the slider would just put you back were you started. Now if you shortened the dampener rod one inch the bike would come down but now you must remove the spring spacers and it will be harder to get the thread started on the top bolts at reassembly. You may need to shorten the spring just a bit for ease of assembly. I know a better way but each to their own.

It's not often that I disagree Ludwig or Norbsa - but, gentlemen... you're wrong about this one. This case, however, only applies to my installation where there are no spring spacers or damper rod.

In either the Commando or Atlas fork tube there is a fixed distance between the underside of the fork top bolt and the spring perch. Top-out is also fixed by the underside of the top-cap and fork bushing. By going with a shorter fork tube, you add preload to the spring, but the ride height will decrease.

The Commando fork tube, fully assembled, is on the left and the Atlas fork tube is on the right.


I'm using Progressive springs, which are too soft to begin with, so the bike still sags about 3/4" with me aboard - giving proper negative travel. I measured a loaded change in floor to "gascap" ride height of about 0.9" - which is what I would have assumed based on the steertube rake angle.

Ludwig,

For what it's worth, your English is just fine. I understand what you're trying to say. Maybe I'm not explaining things well enough in my case.

The stanchions, at any position in the slider's travel, set the relationship between the sliders and the triple trees. Shorter will be closer and longer will be further away. The former will lower the front end and the latter will raise it. Fork internals govern the movement between the extremes of slider travel.

I measured the fork travel before and after the conversion - and there is no difference from stock. I got nearly 6" with Norbsa's kit and I'm getting 6" now. That's due to the fact that the distance the bushed part of the stanchion can travel inside of the slider, between the top bushing and the bottom of the slider, hasn't changed. The free travel within the slider determines maximum possible travel. Coil bind is the second limiter, and so on.

I have no damper rods, so they're not part of the equation.

I mentioned pre-load because Norbsa noted that with the spring spacers (which I don't have - per lack of damper rods as stated above) it might be hard to thread the fork top bolt. Without spacers, damper rods and the associated hardware, there was no issue with threading the stanchion top bolt.

My understanding is that with a standard Commando fork tube, when the forks are fully extended the damper-rod is the element that prevents the forks extending more. In this state there is still well over an inch of travel available at the fork-tube-bush/top-bush interface, therefore fitting shorter tubes will simply take up some of this overlap leaving the fully extended position identical. The ride height is set by the fork spring strength and with shorter tubes and the same damper rod this will be identical and should theoretically give the same ride height, although the overlap of the fork bushes would offer less stability and strength at full extension. Since Dr_Hiller is not using damper rods in his setup then the difference between the long and short tubes will be apparent when at full extention although ride-height will remain a feature of spring strength. Norbsa has a fork kit that exploits this overlap, by using a longer damper rod and additional springs to extend the available fork travel, although the ride height I believe remains the same.

Like Ludwig I have nothing to prove. Already done many bikes. So Thanks Dave for the reality check.
So Kber45 yes the minimum is shorten the dampener rods one inch and the stanchions one inch.And buy some progressive springs to avoid coil bind. Is it the best way, no. You will find that you can drag your pegs very much easier in the turns. And that turn in will be a bit quicker. Same old stock 4 1/2 travel.
It depends on why you want to do this Mod.

Greg:

Not sure how this became such a mess, and I'm not trying to prove anything.

I'll give you that it's a situation with a lot of "ifs" because of the custom nature of many parts on my bike, but I was hoping to contribute to the knowledge base by sharing my experience.

I took the time to measure and document these things in photos and notes, and I'm certain the information is correct.

I'm not saying it's a more ideal solution than yours. I have your kit and ran it for a year without any complaints. I only removed it because I wanted to lower the bike's COG and steepen the steering angle and couldn't do so without either going to Atlas internals (not an improvement) or a Gold Valve damper. I went with the latter.

The result: it seems to handle a bit quicker - but that was the goal. For what its worth, my rearsets don't scrape with pretty aggressive street riding.

In the end, it's an option. It works exactly as I've stated. It's easy to do. Take it or leave it.

(I sure hope someone got something useful out of this thread, 'cuz all it's giving me is a headache.)

Gentlemen, this is not a mess, quite the contrary the discussion illuminates the fact that different approaches to an improvement in fork performance are available for our chosen marque (don't forget also the Covenant fork kit which many of us have used to good effect.). It also blows away the misconception that with a standard fork a simple change to a shorter fork tube and nothing else will achieve the desired result of lowering the bike. This could save some of our fellow enthusiasts some money during these times of economic uncertainty. I am personally interested in the performance benefits and availability of both the gold valve system that Dr_Hiller uses and Norbsa's modifications.

Dr_Hiller said:

Greg:

Not sure how this became such a mess, and I'm not trying to prove anything.

.)

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I'm with you here, the breed must be improved and the only way is to try. However, do be careful I am old enough to remember Roadholders breaking off just below the top bushes and at the time reported in the MCN and MCW. I'm sure the first breakage was in 1966/7 on a newist Atlas involved in a minor collision. I reckon the conditions needed to have a collision with the bushes close together will be rare but non the less there's a risk.
Best of luck.

Cash

Thank you all for your coments, I am overwhelmed. There is obviously a lot of expertise on this site. I will make some changes and then post some pictures.

And to think, I was going to ask an easy, none contensious question like "How did the british motorcycle industry fail?"

Thanks all,
Kber45

A reminder: if the front and rear heights are both reduced by the same amount, the apparent rake angle (vs. horizontal) is unchanged, but the trail is reduced, so handling will be slightly different.