Rear suspension geometry

[Mr Gazza]

Would anyone be good enough to measure thier rear suspension rocker please? If you happen to have one out of a bike.

Rather tricky to measure in-situ as you can imagine! This isn't important enough for me to strip mine out.

I am looking for the hole centres as indicated in my highly accurate technical drawing...:rolleyes:

http://i57.tinypic.com/bi1a3r.jpg

In millimeters please but don't worry about 6 decimal places...just spot on will do.

I am looking for the dims of a rocker from an M series Monster (hoop type)..I am assuming that all the hoop model rockers are the same in terms of these centres?...Does anyone know different?

Also could anyone give me the free length of a standard rear shock, eye to eye centers....Could measure mine but kinda tricky to do it with all the weight off.

Thanks....All will be revealed shortly pending getting the dims.....;)

[Albie]

Would anyone be good enough to measure thier rear suspension rocker please? If you happen to have one out of a bike.

Rather tricky to measure in-situ as you can imagine! This isn't important enough for me to strip mine out.

I am looking for the hole centres as indicated in my highly accurate technical drawing...:rolleyes:

http://i57.tinypic.com/bi1a3r.jpg

In millimeters please but don't worry about 6 decimal places...just spot on will do.

I am looking for the dims of a rocker from an M series Monster (hoop type)..I am assuming that all the hoop model rockers are the same in terms of these centres?...Does anyone know different?

Also could anyone give me the free length of a standard rear shock, eye to eye centers....Could measure mine but kinda tricky to do it with all the weight off.

Thanks....All will be revealed shortly pending getting the dims.....;)

Best I can do tonight without removing ( which I will do easily tomorrow as shock is off but need to remove air breather box )

A is 113
B is 78
c is 177 by tape rule tonight vernier tomorrow

My ohlins is 330 eye to eye.

[utopia]

Excellent plan Mr Gazza.
You're just about to save me a load of winter work, measuring my own suspension linkage.

My Nitron (M750) was also 330mm ..that's between the centrelines of the top and bottom pivot/bolts.

And I happen to have a hoop type, ally swinger hanging on the shed wall, if you need any measurements from that.

[Dirty]

I make it
A 110
B 77
C 175

[Dukedesmo]

Mine's fitted so can't accurately measure but I can confirm that a stock (Sachs) shock and also an aftermarket Ohlins are both 330mm eye to eye.

As far as the rockers go I believe they are all the same both for Monster and 851/888? although there was an adjustable racing version made for the Superbike (fits Monster) and they sometimes appear for sale but usually at very silly prices...

[Albie]

Ok its out and measured with a vernier where distance below 150mm

A is 111mm yes oddly 111mm

B is 77mm

C is 175mm

[Mr Gazza]

Albie, thank you....I hope you didn't take it out on my account just to measure it.

Thanks to Dirty too...I had a feeling you had a spare out off you bike.

So that's the rocker well measured, and the shock firmly established at 330 too...Thanks Utopia and Dukedesmo.

I think I can just about get the rest of the sizes from my bike with it together, but definately not the best way to go about it.

I'll soon be having some fun....I think Utopia has guessed what I'm up to..;)

[Albie]

Albie, thank you....I hope you didn't take it out on my account just to measure it.

Thanks to Dirty too...I had a feeling you had a spare out off you bike.

So that's the rocker well measured, and the shock firmly established at 330 too...Thanks Utopia and Dukedesmo.

I think I can just about get the rest of the sizes from my bike with it together, but definately not the best way to go about it.

I'll soon be having some fun....I think Utopia has guessed what I'm up to..;)

Kind of yes to prove the measurements in case I was wrong or right. It only took 5 mins and I hadn't yet bolted anything in for life. Loctite has not yet been used on anything other than brake discs.

[Mr Gazza]

I've had a go at measuring my swinging arm relative pivots in-situ, and come up with something, but I think it could be a little better.

Jeff if that one hanging on your wall is easy to hand would you mind?..:D

http://i62.tinypic.com/2dl6esi.jpg

I thought it would be good to use a centre line from swing arm pivot to wheel spindle as a datum to measure the offsets of the hoop and shock pivots.

Ta..:thumbsup:

[Albie]

I make mine

D = 235mm
E = 90mm
F = 55mm
G= 15mm

http://i1042.photobucket.com/albums/b423/ukmonster/Monster%20900/20151023_202818.jpg (http://s1042.photobucket.com/user/ukmonster/media/Monster%20900/20151023_202818.jpg.html)

http://i1042.photobucket.com/albums/b423/ukmonster/Monster%20900/20151023_202842.jpg (http://s1042.photobucket.com/user/ukmonster/media/Monster%20900/20151023_202842.jpg.html)

[utopia]

I will check mine just for reference, but I have no spindles for it so I'll have to arrange something.
I imagine Albie's measurements are reliable though.

Today, I did manage to get hold of another dimension.
Thanks to some info from Capo, and that Pythagoras fella, I can give you a measurement of 250.77mm between the centrelines of the swingarm pivot and the rocker pivot on the frame.
I believe that Capo's info is verified by matching received data with measurements from his S4R frame.
I was intending to check this dimension against my frame before posting it, but I can imagine you struggling to measure this dimension (maybe even now as I'm typing this) so I thought it best to post early.

[Albie]

I will check mine just for reference, but I have no spindles for it so I'll have to arrange something.
I imagine Albie's measurements are reliable though.

Today, I did manage to get hold of another dimension.
Thanks to some info from Capo, and that Pythagoras fella, I can give you a measurement of 250.77mm between the centrelines of the swingarm pivot and the rocker pivot on the frame.
I believe that Capo's info is verified by matching received data with measurements from his S4R frame.
I was intending to check this dimension against my frame before posting it, but I can imagine you struggling to measure this dimension (maybe even now as I'm typing this) so I thought it best to post early.

Its not easy without really specialist tools like a vernier height gauge but the swingarm is stock 3" section height so I tried to reference the centre line through. I don't think the tolerance would be so critical because there is so much adjustment within the operation ie pivots and springs and adjusters for height and swivel.

Please check yours Jeff because there may be a difference even in year production or materials but I bet they are close.

[Mr Gazza]

.
Thanks to some info from Capo, and that Pythagoras fella, I can give you a measurement of 250.77mm between the centrelines of the swingarm pivot and the rocker pivot on the frame.

Funnily enough I found this one to be the easiest to just measure with a tape...:chuckle:

Capo sent me those drawings too, and I was stuggling to work out those centres, but the frame info is brilliant.

Thanks again Albie your dims are close to what I got and make a lot of sense..I must say you are very obliging when it comes to dismantling stuff just to measure it for me....How thick is the white metal on your big end shells?.....:chuckle: No! ...Only kidding...:biggrin:

I think I have all the info, and also all the bits made. So it will be hole drilling tomorrow and play time...:woot: Pictures to follow.

[Albie]

Funnily enough I found this one to be the easiest to just measure with a tape...:chuckle:

Capo sent me those drawings too, and I was stuggling to work out those centres, but the frame info is brilliant.

Thanks again Albie your dims are close to what I got and make a lot of sense..I must say you are very obliging when it comes to dismantling stuff just to measure it for me....How thick is the white metal on your big end shells?.....:chuckle: No! ...Only kidding...:biggrin:

I think I have all the info, and also all the bits made. So it will be hole drilling tomorrow and play time...:woot: Pictures to follow.

Its only because its not assembled on the bike I can help. I will always try too and especially if someone is needing it for reference to others later including what could be me at some point.

Regards to white metal ..... NO IDEA at all but will be good now I hope. My 6th gear was ruined by it too and hardening worn away so that's another £200 plus on the bill.

Give me a shout if you need anymore before it gets built up.

[Mr Gazza]

Really only kidding about the white metal....I could just imagine a photo of your cases split and a vernier on shell....Oil everywhere...:chuckle:...and the comment, "There you go mate"..

Seriously, I appreciate the help. I've been slightly sidelined this morning so I hope to get this thing together this evening and start interogating it...Quite exited, been wanting to do this for a while.

Thanks everyone.

[Albie]

I did ask if I could see pics of engine being done but seen and heard nowt. I just know it's due back soon for me to dress back up with a nice finish again. No worries at all.

[Mr Gazza]

Well its all done. But it's clear that I will need to paint some bits to make it easier to photograph.

I have to dissagree with your figure for the rocker to swingarm pivots centres Jeff. I measured it at 260mm on my bike, so I made the model with those centres....But it can very easily be changed.

http://i59.tinypic.com/2qxpdau.jpg
http://i58.tinypic.com/11vmo0m.jpg

Top pic is with the shock at full 330mm stretch and bottom one shows 60mm of shock compression, giving 125mm of wheel travel.

Hoop is set at 245mm length which is about standard I think. As you see I can adjust ride hieght on the model.

The point at the end of the swingarm equates to the wheel spindle centre at mid adjustment.

So far I have seen that raising the ride hieght by 25mm does make the shock lean forwards a bit, as Taff found out on his 750.

I can't yet think of a way to find out if ride hieght adjustments effect pre-load. It seems that pre-load is not effected, but that was not my experience when I altered my bike...Perhaps I should say it effected the sag, which I restored by increasing pre-load??

So there it is....If you have any tasks for the model fire away..

[Mr Gazza]

I've been playing with it...:look:

I have plotted equal wheel movements against shock travel, and yes it does work progressively. As the shock compresses the increments get larger by a tiny bit...I will measure this and draw a graph eventually....When I've finished watching this apple go brown!

I want to find out why my sag increased when I slightly raised the ride hieght.
So I extended the hoop on the model, holding the swingarm.. The shock compressed.

But then I held the rocker and did the same... The shock extended..!!!

What a mind bend...It's the same input??

When I hold the shock at full extension, (as the shock would be in life when effecting a hoop adjustment).
The rocker moves a little and swingarm moves a lot more to accomodate the longer hoop.

Difficult to draw any conclusion from this, but having thought about it, I don't think that the linkages can have anything to do with pre-load, as that is pre-set on the spring itself by the adjusting rings, and the weight of the bike is not changed.

What I think may be happening is that the resting point (static sag) is changed in relation to the "progressive curve", due to the wheel movement effecting a different area of shock travel.
I need to do some more work on this...Hoped it would be easier than this..!!:freak:

[stopintime]

.............

What I think may be happening is that the resting point (static sag) is changed in relation to the "progressive curve", due to the wheel movement effecting a different area of shock travel.
I need to do some more work on this...Hoped it would be easier than this..!!:freak:

Fun to follow your model and play with it :thumbsup:

Indeed, the static sag numbers will be smaller if the ride height is raised. Rider sag won't be as affected - if at all.

The linkage is designed to give a progressive action - less effective spring resistance and less effective damping on top = 'softer' ride on minor bumps, as during moderate street riding.

This also means (unwanted) less spring resistance and less damping when closer to full compression, which Ducati typically 'fix' with a progressive spring.