Conventional vs USD Part II

[Tmod]

Ok I know I will get some poo thrown my way as we all know that USD are leaps and bounds ahead and superior to conventional forks in every way shape or form. There I lied for you all.

Now seriously this came up on a different forum about how superior the USD forks are in comparison to conventional in regards to stiction or lack of on USD forks.

First let me say I am in no way opposed to USD forks or am I saying that conventional are better. I am just trying to relay the information I found to those that read different things on the web that may be false.

If you have seen where a conventional forks bends as opposed to the USD fork they are pretty much both the same in that it is right below the lower triple clamp, Makes sense since that is the point where the most leverage is and the most supported right at the base of the lower triple. If you take your bike that has USD forks and very gently put the front tire up against a wall and then gently apply the throttle and feather the clutch you will see that the USD do indeed deflect, Do the same to a conventional fork and it will deflect as well. Now here is where the issue lies with the USD fork, The bushings are fixed and as in the image below at 307mm apart. Since the bushings are fixed in the outer tube and the fork tube itself sliding inside any deflection of that outer tube will give you more stiction than a conventional fork would have.

Even if there was a movable bushing on the USD fork you would still have the same issue as the housing where the bushings are sliding is no longer straight. It only takes a few thousands of a inch to cause stiction. Now with the conventional fork the fork tube itself will deflect at the bottom of the lower triple so there is not any binding down in the lower leg to cause a stiction issue.

Here is the image you can see where both will bend and just as a note the conventional is a CBR600 F3 and the USD is off a R6. With the conventional as badly bent as it is I can still push down on the fork tube and it will slide freely but even with the slight bend that the USD fork has the tube is stuck in the bore.

If you agree or disagree post on back if you want to discuss this more.



Tmod

[92GSX750]

Thanks to the picture I can clearly see where this would be an issue with a USD setup. Basically any decent impact with that front setup will ruin the forks.

Now my question is this:

How much of a bend is really tolerable with a conventional fork setup? Obviously the forks pictured are both trashed, but are you saying that with conventional you can run with a sligh bend?

[Tmod]

Now my question is this:

How much of a bend is really tolerable with a conventional fork setup? Obviously the forks pictured are both trashed, but are you saying that with conventional you can run with a sligh bend?

I would not suggest running with any bend but I can tell ya this, I have had bikes in here with conventional forks and the rider didn't know there was a issue as they perform perfectly normal with the exception being the steering will be strange and the geometry will be off. If you had a slight bend in a USD setup they will bind.

I posted this in response to some info on the web stating that the USD have less of a stiction issue then a conventional fork would have.

Tmod

[Badfaerie]

Wow T, that makes total sense. I must be absorbing some of you suspension-speak.

I understand that one fork style isn't inherantly better than the other, but are there certain application/conditions that the individual fork types are better suited for, other than conventional keeping it's squishy better when bent.

[cintidude04]

How much of a bend is really tolerable with a conventional fork setup? Obviously the forks pictured are both trashed, but are you saying that with conventional you can run with a sligh bend?

I spent good money getting a set of kat tubes all set up with TiN coating. An due to a tiny bend that was only discovered when T measured the tubes, I now have an expensive set of table legs. These tubes went through several sets of hands, including a professional shop, with no one noticing this.
But in the end it was advised not to use them, and I went on to work on ideas for a different front end (due to Nancie calling me a copycat )

[scottynoface]

Just to clarify T, why are you arguing the benefits of which fork will work better when bent?

Who the hell runs with bent forks?

[cintidude04]

Who the hell runs with bent forks?

This is KR Taylor... you'd be suprised...

[Tmod]

Just to clarify T, why are you arguing the benefits of which fork will work better when bent?

Who the hell runs with bent forks?

People that don't know their forks are bent.

Not arguing which would work better when bent I just used that as my point to those that say the USD is superior and does not suffer from stiction like a conventional fork would. My point is that the USD flex just as the conventional do but the USD will have stiction when they flex where the conventional will not.

Tmod

[scottynoface]

People that don't know their forks are bent.

Not arguing which would work better when bent I just used that as my point to those that say the USD is superior and does not suffer from stiction like a conventional fork would. My point is that the USD flex just as the conventional do but the USD will have stiction when they flex where the conventional will not.

Tmod

Okay gotcha. I figured it was a flex demonstration, extreme examples but good proof of concept

USD forks look better though...

[Tmod]

USD forks look better though...

No doubt, I like the look of them myself.

Tmod

[arsenic]

This is KR Taylor... you'd be suprised...

I wouldn't

[Wreckie29]

Does anything surprise you anymore???

[arsenic]

Does anything surprise you anymore???

In the general population? Every day. On here? No.

[thetable]

Does anything surprise you anymore???

Fine line between surprise and disbelief... IJS!