Fork Slider cracking below the axle

Jonez69

Jonez69

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I have seen this on OIF triumph fork caps, now I find it on my new to me 73' Commando. This is not something to ignore, so I will be replacing and rebuilding forks over the winter. Is this a common problem? This is my first Norton. If it is not common, I will consider looking for a used replacement.
Thanks for your replies!
Fork Slider cracking below the axle
 
AFAIK it is not common on that side, it is the other side, with the pinch bolt, that is more prone to cracking due to the pinch bolt being over tightened.

It’s not obvious to think what could have caused your crack, all I can think of is a loose axle nut, allowing the axle to apply loads to the leg fore and aft rather than those loads be contained by being clamped tight (just a guess) ?
 
Last edited:
Fast Eddie said:
AFAIK it is not common on that side, it is the other side, with the pinch bolt, that is more prone to cracking due to the pinch bolt being over tightened.

It’s not obvious to think what could have caused your crack, all I can think of is a loose axle nut, allowing the axle to apply loads to the leg fore and aft rather than those loads be contained by being clamped tight (just a guess) ?
Click to expand...
The other two possibilities I can think of are that the fork tubes are not parallel and/or no in the same plane or that the nut was WAY over tightened.

I recently had one that with my longest breaker bar extended with a fork tube and with my ridiculous weight basically hanging from it finally got the nut loose. I have no idea how the previous idiot got it so tight. Also, my 6" wide plate glass had a 1/4" gap when flat on one tube and one edge touching the other tube - the forks were mis-aligned due to a bad bottom yoke. I can easily see either of those causing a crack - fortunately it didn't on that bike. It did crush the aluminum enough that I had to "unscrew" the spindle from the fork tube and then cleanup the hole to put it back together!
 
Jonez69 said:
I have seen this on OIF triumph fork caps, now I find it on my new to me 73' Commando. This is not something to ignore, so I will be replacing and rebuilding forks over the winter. Is this a common problem? This is my first Norton. If it is not common, I will consider looking for a used replacement.
Thanks for your replies!View attachment 116614
Click to expand...


There are signs:
 

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  • Fork Slider cracking below the axle
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Accident damage, the spindle has tried to bend upwards and so cracking the leg bottom. This slider was probably the only thing left from the front end that was anywhere near reusable.
 
Are two of those disc studs, grub screws fitted with nuts to act as studs? If so, another thing to have a close look see at and replace with the proper item. This new to you '73' commando requires a good going over as it looks like it has been chucked together to sell
 
Thanks for everyone's input. Could it not also be a case of over tightening the fork end clamping nut as opposed to accident damage? dobba99, yes, they appear to be. I'm about to pull the front wheel off just to have a look at everything. I haven't owned the bike very long so I the process of finding needed repairs goes on...:)
 
There are very few left that have been with the same owner for decades. 50 years old and multiple owners, so they need a good check through. Stating the obvious!

But, as you're finding, they're a cracking bike, even in modern road conditions. With excellent spares availability and lots of guidance (searches on this forum have solved a lot of my little problems). They can be very reliable. I thought I'd put about 1,000 miles a year on mine, but im running over twice that, would be more but for problems with my other old bike, meaning I run that to test it out when I'd been planning to use the Commando. They look great too. So a bike to be proud of, once you've gone through it.

My other old bike is a CB750K6. Great bike. But the Norton is made with better and thicker materials. Quicker too. Worth being persistent :)👍
 
dobba99 said:
Are two of those disc studs, grub screws fitted with nuts to act as studs? If so, another thing to have a close look see at and replace with the proper item. This new to you '73' commando requires a good going over as it looks like it has been chucked together to sell
Click to expand...
You are exactly correct. It does require a thorough going over. I made a good trade to acquire this bike from a friend, so my investment is very reasonable.
I have ridden it just over 1000 miles in the time I have had it. Over the coming winter months I will be getting it sorted. I have sorted several Triumphs for myself and friends, so I have some knowledge of what to look for and can spot things that just aren't right. I have already sorted out several small issues,
this fork slider problem got by me until yesterday when I was detailing and cleaning after a pleasant 90 mile run. The bike starts easily, performs well doesn't smoke, is oil tight, and has good compression. I think with more sorting and replacing some of the janky parts, it will be a good machine. I won't be upside down financially when it is all done, IMO.
 
Pull the axle and roll it on a flat surface to see if it it flat. If not replace or straighten.
Straighten? Let the wanking begin.
 
I pulled my front wheel off again this morning. The axle is true so no need for replacement. I am going to buy a set of new sliders so all new components there too. I think the springs are fine. Stanchions look good too. I am also rebuilding the brake caliper and putting on a new AN 13mm master cylinder. I'll be buying two new tires over the winter as well. I'm already piling up the old Norton parts!:rolleyes: Here's a pic of the axle bolt installed showing how the hole itself is out of round on the slider. Thanks again for everyone's help!
IMG_6652.jpeg
 
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dobba99 said:
Are two of those disc studs, grub screws fitted with nuts to act as studs? If so, another thing to have a close look see at and replace with the proper item. This new to you '73' commando requires a good going over as it looks like it has been chucked together to sell
Click to expand...
And yes, I am replacing those janky grub screws!
 
Jonez69 said:
I pulled my front wheel off again this morning. The axle is true so no need for replacement. I am going to buy a set of new sliders so all new components there too. I think the springs are fine. Stanchions look good too. I am also rebuilding the brake caliper and putting on a new AN 13mm master cylinder. I'll be buying two new tires over the winter as well. I'm already piling up the old Norton parts!:rolleyes: Here's a pic of the axle bolt installed showing how the hole itself is out of round on the slider. Thanks again for everyone's help!View attachment 116662
Click to expand...
Yup, def looks like either crash damage or hammering caused by a loose axle nut IMO.

Definitely a good call to replace.
 
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