Fork yoke enquiry

Well, this is why we have this forum. I think I'll take the plunge and order the RGM yokes, my concern as well is tank interference, as I have a 5 gal manx tank. The 3/8 difference in offset "might" be a problem, but the yokes RGM sells require the user to install steering stops, so I think tank interference can be mitigated

There are two extremes which can result from changing steering geometry. The handling can become more stable and the bike tends to run wide in corners, or the handling can become less stable and the bike tends to tighten it's line in corners. With the former, you might have to reverse steer to get the bike to tip in to corners, however it is safer. With the latter, the steering is much quicker, but you have to learn how to use it to best effect.
Changing the fork yokes is fraught with danger if you cannot recognise the symptoms which might indicate mishandling, because the crash might seem to come from nowhere.
The steering geometry is a combination of rake and trail. A Manx has 24.5 degree rake and fortunately, it is difficult to reduce the yoke offset because of the shape of the bottom yoke. The first commandos apparently had handling which was considered to be too quick for beginners, however my feeling is that it was probably quite good.
There seems to be a problem with the commando if the isolastics are not set up right and the steering is too quick - however If I owned one, I'd use the early steering geometry.

When you compare what yokes are used on various bikes, you should never assume that what works well at a certain rake, with work well at another. Also the wheel-base has an effect because when power is applied coming out of corners, the rear end squats and the rake changes - that is what creates the feeling of stability and either creates confidence or destroys it.

acadian said:

Well, this is why we have this forum. I think I'll take the plunge and order the RGM yokes, my concern as well is tank interference, as I have a 5 gal manx tank. The 3/8 difference in offset "might" be a problem, but the yokes RGM sells require the user to install steering stops, so I think tank interference can be mitigated

Click to expand...

After I installed the interstate tank on the modified brackets to move it backward, the dip switch lever still barely contacted the gas tank when the handlebars were fully turned using my narrow 24" wide "bmw style handlebars". They have a tiny rise and slight angle pull back to them. Since I was working on a yoke mounted fairing, I had the new steering stops welded to the face plate of the fairing bracket's yoke plate to limit the swing of my steering head. I also welded the new stops so they would rest against the old stops that are welded onto the yoke, so the old stops hold my fairing mounting plate centered so it can't move from side to side.

Modifying this bike has been a huge battle for me at every turn. I haven't had any modifications that were "Unbolt part A and bolt up part B". Every time I substituted a non-norton part, I was back on an expensive adventure trying to find the best place to make parts transition seamlessly. (the yamaha cast wheels, the interstate tank, and now the honda dunstall fairing) It's been an ongoing battle with excellent results because I persisted and spent a lot of money to make it right.

IF I had to bet that you will bolt up those new tripple trees without any issues from looking at the picture of the tank on your bike in your thumbnail photo, I would bet your going to have to modify your steering stops (as RGM says), but you might get luckier than I was.

As far as changes to your rake and trail, I like to think that small changes probably have small effects. I did a lot reading on how the sky was going to fall if I went to an 18" back wheel. The sky did not fall. My bike is handling better than ever (new tires probably made the most difference IMO)

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As far as changes to your rake and trail, I like to think that small changes probably have small effects. I did a lot reading on how the sky was going to fall if I went to an 18" back wheel. The sky did not fall. My bike is handling better than ever (new tires probably made the most difference IMO)'

You might make that assumption, however the generalisation would be false. Very small changes in yoke offset can make big changes to the handling depending on the rake. Most road bikes are set up to have handling which is on the stable side of neutral, so if you manage to quicken the steering slightly, the bike feels better. If the bike is already twitchy and you quicken the steering the crash can come from nowhere, and very small changes to the geometry can create that situation. Try riding around a corner with your front brake just dragging slightly. While the front of the bike is dipping slightly, it will tend to run wide. And the difference in rake is fractions of a degree.