Fork alignement

[volitan]

Hey guys,
 
I bought motion pro fork Alignement tool and found that my forks were off by approx 2mm.
 
Apparently your suppose to loosen the pinch bolt for the wheel axle and move the fork in or out, whatever you need to in order to be square with top of the forks and then re tighten the linch bolts.
 
My question is, would moving the forks to line end then up and tighten the pinch bolts cause an unwanted side load and wear bearings and seals prematurely?

Beta 300 2017

[lotus54]

I do not believe proper alignment would affect the seals/bearings.

I have been using that tool for many years- I noticed better response from the forks after using it.

[Baxter67]

This may help... 

 

[surfer-dude]

I was told recently that you set one leg where you want it, then adjust the other side by aligning it so the axle goes smoothly in and out. once its as good as you can get it, then you tighten the other side triple clamp bolts. mine is a difference of about a half mm out than both the same distance out from the top of the triple clamp.

Prior to this I had always made them the same distance from the top clamp using a little machinst tool for checking these kinds of things(I dont know what it's called right now) and would have to smack the axle in.

My wheel spins much better and rubs the brake less.

I was told that weird wear would happen, Ive done it the other way my whole life and I barely did it this way recently so I dont know...

[RudderFeet]

With the ridiculous stresses placed on dirt wheels, forks and frames, I’m thinking that finely tuned alignments are the least of what bearings and whatnot go through.

[GP]

The tool is a mechanical reference, it is more precise than your judgement or feel.   Used correctly, the fork is aligned, period.  That is the ideal situation for operation and minimized side loads on compression. 

[volitan]

So from what i understand in that video, he is saying to let the forks sit naturally were they want to sit.

 

[volitan]

I do not believe proper alignment would affect the seals/bearings.
I have been using that tool for many years- I noticed better response from the forks after using it.

When you used the tool. Did you have to push the fork in and then tighten the pinch bolts? Or were your forks pretty close to line up right off the bat?

With the ridiculous stresses placed on dirt wheels, forks and frames, I’m thinking that finely tuned alignments are the least of what bearings and whatnot go through.

Thats a good point

[FORMA MOTO]

15 minutes ago, volitan said:

So from what i understand in that video, he is saying to let the forks sit naturally were they want to sit.

 

This is based on an assumption that the triple clamps, and their machining, is all 'plumb', which it often is not.  

If you want to prevent fork binding, each fork has to be straight, NOT forced to be parallel at the lower half.....because if you have to tweak the forks to make them parallel, they are no longer straight, and then you get binding of the bushings......and again, if the triple clamp machining is not perfect, none of this matters.

The first time I remove the front wheel, polish the right side axle surface, and inside the fork, and grease everything, then with the front end assembled, I REMOVE the pinch bolts on the right leg (and put in a plastic wedge, if needed) and let the fork find it's own straightness by vigorously pumping the suspension and spinning the wheel and slamming on the brake. Then I mark the axle with a razor blade, creating a reference mark to use next time I change the wheel.

I have found the Motion Pro alignment tool to work correctly on some bikes because of the 'sticking' right fork lug on the axle, but have also found it to be completely inaccurate on other bikes, because the triple clamps were not plumb, and the MP tool was having me bend the fork to make them parallel......

Try measuring the forks with the front wheel removed, to see if they are parallel to begin with !  On some bikes you will be very surprised....

 

[lotus54]

51 minutes ago, volitan said:

 

When you used the tool. Did you have to push the fork in and then tighten the pinch bolts? Or were your forks pretty close to line up right off the bat?
 

 

 

I’ve found I’ve had to tweak slightly in general, not very much. The axle- even when the forks are vertically aligned tend to ‘stick’ a little, perhaps holding the forks slightly out of alignment.  So far, I’ve only had excellent results with that tool- sometimes definitely noticeable.   If the triples are not ‘true’ the forks will never work right, since there will always be some side force somplace in the fork travel from them not being parallel.

 I suppose another way would be to remove the caps- allowing the forks to bottom- then tightening everything up. But that would rather be a pain...

 

this is just my experience of course.  It doesn’t mean much.

mark

[Baxter67]

Lets try another video just for the fun of it... 

 

[GP]

Play in the fork lug, as its moved in and out on the axel, is from the small clearance in the bushings.  There will also be a natural position where this sits due to spring tension, and it will usually be to one side, not in alignment.  The tool simply allows correct positioning within that range of play.   I don't believe that T clamp tolerances are a factor at all, in the days of precision CNC machining this is far less than detectable.  Plus, both upper and lower would have to have the same error, or you would know immediately when sliding the forks in the clamps.  Highly unlikely. 

When I mount my forks, I fine adjust the height of right leg in the clamps so the axel can spin in the lugs with minimal drag.   With the wheel mounted and brake side tight, loose right side, forward pressure on the rear of the lower tubes with the tool is usually enough for the V blocks to center them, and a quick snug of one of the pinch bolts holds the adjustment. 

[volitan]

Play in the fork lug, as its moved in and out on the axel, is from the small clearance in the bushings.  There will also be a natural position where this sits due to spring tension, and it will usually be to one side, not in alignment.  The tool simply allows correct positioning within that range of play.   I don't believe that T clamp tolerances are a factor at all, in the days of precision CNC machining this is far less than detectable.  Plus, both upper and lower would have to have the same error, or you would know immediately when sliding the forks in the clamps.  Highly unlikely. 
When I mount my forks, I fine adjust the height of right leg in the clamps so the axel can spin in the lugs with minimal drag.   With the wheel mounted and brake side tight, loose right side, forward pressure on the rear of the lower tubes with the tool is usually enough for the V blocks to center them, and a quick snug of one of the pinch bolts holds the adjustment. 

So what i understand is that the spring tension is pushing the fork tube one way or another and by me pushing the fork tube in to get it aligned, it wont wear unevenly inside the forks?

[volitan]

T
“Try measuring the forks with the front wheel removed, to see if they are parallel to begin with !  On some bikes you will be very surprised....
 

I took the wheel and measured it. They were off by about 2 mm just sitting extended.
I have never checked this since ive owned bike, over 25 years. Only the compressing method with brakes on. Always assumed they were straight

[ToolmanJohn]

The axle system on the Xtrainer is s o similar to my old bicycle DH fork.  There is only one pinch bolt on the Xtrainer right fork leg. The sequence is to tighten the axle (the right fork leg is threaded, no nut), Then cycle the forks up/down, then snug the pinch bolt. Done. I tried the motion pro tool. The fork is in alignment. i imagine the only thing the motion pro tool could tell me is if the forks were bent.

[PIERRE SIMARD]

8 hours ago, KRAYNIAL said:

This is based on an assumption that the triple clamps, and their machining, is all 'plumb', which it often is not.  

If you want to prevent fork binding, each fork has to be straight, NOT forced to be parallel at the lower half.....because if you have to tweak the forks to make them parallel, they are no longer straight, and then you get binding of the bushings......and again, if the triple clamp machining is not perfect, none of this matters.

The first time I remove the front wheel, polish the right side axle surface, and inside the fork, and grease everything, then with the front end assembled, I REMOVE the pinch bolts on the right leg (and put in a plastic wedge, if needed) and let the fork find it's own straightness by vigorously pumping the suspension and spinning the wheel and slamming on the brake. Then I mark the axle with a razor blade, creating a reference mark to use next time I change the wheel.

I have found the Motion Pro alignment tool to work correctly on some bikes because of the 'sticking' right fork lug on the axle, but have also found it to be completely inaccurate on other bikes, because the triple clamps were not plumb, and the MP tool was having me bend the fork to make them parallel......

Try measuring the forks with the front wheel removed, to see if they are parallel to begin with !  On some bikes you will be very surprised....

 

In my opinion, improper machining in today’s world is highly improbable. CNC and modern manufacturing process...I wouybe surprised

[FORMA MOTO]

1 hour ago, PIERRE SIMARD said:

In my opinion, improper machining in today’s world is highly improbable. CNC and modern manufacturing process...I wouybe surprised

I know I was.

Protaper, Doug Henry/HRC, 2008 KTM 500 XCW, all had triple clamps that made the forks not parallel. And yes, I twisted them around to see if they were bent. 

The Betas, Yamaha's, and recent KTM's are perfect.

 

[Odysseus]

9 hours ago, GP said:

Play in the fork lug, as its moved in and out on the axel, is from the small clearance in the bushings.  There will also be a natural position where this sits due to spring tension, and it will usually be to one side, not in alignment.  The tool simply allows correct positioning within that range of play.   I don't believe that T clamp tolerances are a factor at all, in the days of precision CNC machining this is far less than detectable.  Plus, both upper and lower would have to have the same error, or you would know immediately when sliding the forks in the clamps.  Highly unlikely. 

When I mount my forks, I fine adjust the height of right leg in the clamps so the axel can spin in the lugs with minimal drag.   With the wheel mounted and brake side tight, loose right side, forward pressure on the rear of the lower tubes with the tool is usually enough for the V blocks to center them, and a quick snug of one of the pinch bolts holds the adjustment. 

I think some of the wear issues we are seeing is due to guys crashing and not  immediately and properly realigning the the front end.Twenty hours with a ton of tension in the wrong place has to have some kind of an effect.

Edited February 22, 2019 by widebear

[GP]

20 hours ago, volitan said:

 

So what i understand is that the spring tension is pushing the fork tube one way or another and by me pushing the fork tube in to get it aligned, it wont wear unevenly inside the forks?

Yes.  The overlap at full extension is small, so bushing clearance will yield much more play at the lug.  There is no way in hell you could expect this to fall naturally centered better than you can do with the tool. 

[GP]

16 hours ago, widebear said:

I think some of the wear issues we are seeing is due to guys crashing and not  immediately and properly realigning the the front end.Twenty hours with a ton of tension in the wrong place has to have some kind of an effect.

I agree its a variable for sure, on some but not all.  Some of the guys with these issues are smart enough to know that's a bad idea, especially after owning bad forks before.  IMO, there is something in the design and/or mfg tolerances that collectively is not tolerant enough of outside variables.   Its dynamic and complicated.  I don't think they (Sachs) really understand it yet.  Sure a lot of guys don't have a problem (yet anyway), but there sure as hell is greater percentage of issues per a given population of forks compared to say KYB or WP.