"Rogered Forks"

[bigtwinthing]

i think its 347mm between centres

345mm is standard eye to eye so yes 347 would be as if you had a 2mm spacer in. 350mm is the recommended maximum not to exceed.

(:-})

thanks for that. That Roger knows his stuff!!!

[gl_s_r]

i think its 347mm between centres

345mm is standard eye to eye so yes 347 would be as if you had a 2mm spacer in. 350mm is the recommended maximum not to exceed.

(:-})

thanks for that. That Roger knows his stuff!!!

In which case I'm sure Roger will tell you the linkage works at a ratio close to 2:1 and the extra 2mm will be the same as a 4mm spacer...

[VTRDark]

Whether you slip a 2mm shock spacer in or adjust the shock height 2mm wouldn't that be the same.

Found the thread where I got my notes.
http://www.vtr1000.org/phpBB3/viewtopic ... mm#p264454

(:-})

[gl_s_r]

http://www.vtr1000.org/phpBB3/viewtopic ... ck#p239142

look at the fourth post down.. reply from the man himself

A 6mm lift is a high as the VTR wants to remain stable. Alternatively if you have an adjustable aftermarket damper you can increase the shock length "centre eye to centre eye" from 247mm to 250mm and as the rising ratio of the linkage is effectively 2:1 the effect of quicker turning will be the same. Ideally this should only be done on bikes where the forks that have had some degree of tuning as the OEM forks "bottom out" under hard breaking and any action that increases the loading on the front tyre can only exaggerate the problem. The effect would be most noticeable under breaking on the approach to high speed bends where the extra loading could push the front tyre away effectively losing the front end. The shortcomings and remedies of the VTR forks are well documented on all the VTR related sites and my personal recommendation is if you have not upgraded the forks to some degree then you are safer leaving everything standard and riding the bike within its capabilities.

As you can see from this answer the 3mm height of change of the shock is the same as a 6mm slip block... so going from the standard 345mm to 348mm would be the same as a 6mm slip block.

[AMCQ46]

Mark,
I am with Carl on this one.

a 2mm longer shock is the same as a 2mm spacer above the shock. but due to the linkage they both move the rear spindle 4mm [ie it lifts the back of the bike by 4mm], so a 2mm shock spacer has the same effect as dropping the forks 4mm.................well that how my brain works it out

[gl_s_r]

I can see what your saying and personally my brain says the same... as the length to the frame where the shock mounts is the same if it's a 347mm shock as it is with a shock 345mm long and a 2mm spacer.

If two bikes were set up as above they will have the same dimension for the rear spindle from a reference point as Carl mentioned.

The only difference I can think that with rising rates/leverage ratios etc that may change things in anyway is that the pivot point of the shock (where the bolt goes through) at the top most point is lower if you use a spacer compared to making the shock longer??

So as an exaggerated example and question, if I ran a 300mm long shock with a 47mm spacer at the top would the suspension work in the same way and give me the same suspension workings/geometry/behaviour as one set at 347mm long with the top pivot point where it should be compared to the pivot point being at bottom of the spacer 47mm lower?

In effect if we set up this bike with the shorter shock and 47mm spacer it would still have the same dimensions for the rear spindle from a reference point as the bikes in the first paragraph but I am sure this one would behave in a very different manner because of the leverage ratios etc.

I know we are only talking mm's but people say what a revelation it is to have the spacer so mm's seem to matter.

Anyway the main point that I posted this, is that Roger who was mentioned in the thread, had a different opinion and that is what his advice on shock length is... that the change in shock length is equivalent to a spacer twice as wide. It wasn't to create any arguments or prove anyone right or wrong.. just wanted to point out that the guy that they were talking about had a different opinion unless I have misread that post.. which is entirely possible!

[Jamoi]

I have to admit, I was a little confused about what the difference is between a shock and spacer measuring 347mm total or an extended shock measuring 347mm total.

Like you say Mark, the shock will have different "usable" lengths in the 2 setups.

Edit.. no there won't be any difference in the shocks avaliable stroke, as the adjuster simply extends the mounting eye.

So therefore there should be no difference between extending a shock by 2mm and a 2mm spacer...

I'm confused!

[Virt]

I'm confused!

Then stop slacking and get back to work

[Jamoi]

I am at work! I'm in the office today

[gl_s_r]

I have to admit, I was a little confused about what the difference is between a shock and spacer measuring 347mm total or an extended shock measuring 347mm total.

Like you say Mark, the shock will have different "usable" lengths in the 2 setups.

Edit.. no there won't be any difference in the shocks avaliable stroke, as the adjuster simply extends the mounting eye.

So therefore there should be no difference between extending a shock by 2mm and a 2mm spacer...

I'm confused!

I don't think I am saying anything about usable length of the shock but more to do with the leverage and rising rate ratios in relation to the anchoring position of the top point of the shock.

Maybe now I am a little confused or even maybe causing confusion??

[AMCQ46]

I think you might be reading the wrong meaning into Rogers words "6mm lift" . if he was talking about lifting the back of the bike rather than the size of the spacer, then it all makes sense.


Suggest we stop double guessing and wait for Roger to put us out of our misery when he next pops in

[Jamoi]

Hehe, I get you now

You make perfect sense Mark, putting a spacer in effectively changes the top shock pivot/anchor location.

I too would be interested to see if Roger has any more info this subject. As I haven't set my suspension up properly yet.

[gl_s_r]

I think you might be reading the wrong meaning into Rogers words "6mm lift" . if he was talking about lifting the back of the bike rather than the size of the spacer, then it all makes sense.


Suggest we stop double guessing and wait for Roger to put us out of our misery when he next pops in

That will be nice as I have read various threads about this and most supporting what you have said but then I have seen others where Roger says different.. just be nice to get to the bottom of it all.

here is another post that points to the way of thinking that there is a belief the changes to the shock are worth double on the spacer width... in this one he says nothing about lift.

http://www.vtr1000.org/phpBB3/viewtopic ... ld#p318660

If guys have had their forks tuned and are fitting an aftermarket damper with adjustable length facility I recommend that you set the shock length to 347mm "centre eye to centre eye" for improved handling.
Roger

Hi Paul,
This will raise the rear the equivalent of a 5mm slip plate to help quicken the steering.
I cannot say how it will feel with Renthal hi-bars having never ridden a bike with them fitted.
Regards
Roger

Like I said I am not arguing with anyone on this... just kind of lost in it all and would like to find a definitive answer.

[VTRDark]

arguments...where are they then. It's what I would call many brains coming together as one. Everyone input their data, do the working out and come to a final output. Multiprocessing.

It certainly would be nice to get it clear and made sense of. I just don't understand what the difference is between putting a shock spacer in up top compared to adjusting the shock if it's one that comes with height adjustment. I thought the whole purpose of a height adjustable shock is so you don't have to use a spacer. Wouldn't the pivot point be the same whether the extra is created up top or bottom of the shock, as they both move the position of the pivot point ie linkage the same amount. I totally understand that adjusting the height does not equate the same at the wheel because it's further away from the pivot point which is where the 2 to 1 ratio comes into play.

(:-})

[Jamoi]

Wouldn't the pivot point be the same whether the extra is created up top or bottom of the shock, as they both move the position of the pivot point ie linkage the same amount.

From what I can fathom,

If you have a 2mm spacer on the top of the shock, you are moving the top shock pivot point down by 2mm. Whereas if you have extended your shock by 2mm the top pivot point remains in the stock location.

I'm not sure moving the pivot point down by 2mm will have any impact on the geometry of the shock action, as it's such a small ammount.

Which brings me round to my potentially daft theory... extending an adjustable shock by 2mm (for example) is basically the same as using a 2mm spacer on top of a non-adjustable shock.

I think we need Roger... my brain hurts