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 Rear shock bump stop

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ghezzi
Fra Cristoforo
Fra Cristoforo


Posts : 1692
Join date : 2014-05-22
Age : 59

PostSubject: Rear shock bump stop   Tue Oct 14, 2014 6:55 pm

My spare GRiSO shock has no external bump stop rubber. Can someone confirm if that's normal?

Advertising bull shit amazes me.
Bellagio advertised rear travel is 120mm. Fitted stock rear shock with no spring and plotted travel with dial gauge.
With a 24mm rubber bump stop attached shock appeared to have 32mm of free stroke, but I managed 40mm of plotting.
For this the actual rear wheel travel is 92mm. That's more than a full inch I don't get. Fuck, we need it here on our goat tracks that gummint call major roads.


GRiSO is advertised at 110mm travel. My GRiSO shock has 50mm free stroke with no rubber bump stop. So that equals 115mm wheel travel. ?????
If I was to add a 24mm rubber bump stop to the GRiSO shock, the travel would be dramatically less than 115mm.

Overall rocker ratio plots out at 2.3:1 (every 1mm shock movement = 2.3mm wheel travel). It starts at 2.6:1 reducing to 2.1:1 by full compression.

Matris R is not an improvement on either of these in relation to total travel available.
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ghezzi
Fra Cristoforo
Fra Cristoforo


Posts : 1692
Join date : 2014-05-22
Age : 59

PostSubject: Re: Rear shock bump stop   Thu Oct 16, 2014 6:02 pm

Bump (pun intended).

Can somebody tell me if stock GRiSO shock has an external rubber bump stop at the bottom of the shock shaft?

If so, how thick is it?
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mark111
Grignapoco
Grignapoco


Posts : 187
Join date : 2014-04-23

PostSubject: Re: Rear shock bump stop   Thu Oct 16, 2014 6:59 pm

yes it does on the shaft
size? probabley about 25mm but not sure as I have never seen one in one piece, they have usually been hammered and are falling apart
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guzziownr
Biondino
Biondino


Posts : 216
Join date : 2013-12-23

PostSubject: Re: Rear shock bump stop   Thu Oct 16, 2014 7:00 pm

External?  I can fish this stocker out of a box if you need a measurement.
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ghezzi
Fra Cristoforo
Fra Cristoforo


Posts : 1692
Join date : 2014-05-22
Age : 59

PostSubject: Re: Rear shock bump stop   Fri Oct 17, 2014 1:32 am

Thanks for that.
Stelvio shock is identical to Bellagio shock, only longer.

My next plan for a better quality ride is;

Make a new 'L' shaped linkage for Bellagio that both increases initial ride height in the interest of steeper rake and quicker steering.

Bur more importantly, increase the overall ratio to give more rear wheel travel to cope with our goat tracks.

Currently I have around 90mm rear wheel travel, I'd be happier with a real 120+mm.
This may require a heavier spring, I already have the original Matris unit which would support the Sydney Harbour Bridge.

Don't panic about unknown black art. I got Tony Foale's suspension kinematics and a  susp guru with a red crayon.


Uzi, feel free to chip in anytime with questions / guidance etc.
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ghezzi
Fra Cristoforo
Fra Cristoforo


Posts : 1692
Join date : 2014-05-22
Age : 59

PostSubject: Re: Rear shock bump stop   Thu Oct 23, 2014 4:52 am

Slight change of plan;
Turns out the Matris has a top out spring about 25mm long. Removing it and inserting a hard rubber top out bush will net me an increase of 10-12mm shock shaft travel. With an overall rocker ratio of 2.3:1 means a theoretical increase in rear wheel travel from 92mm to 115-120mm.

Also would mean rear ride height increase of similar amount, 23-28mm. That will reduce rake by approx 1°, the 17" front C/F wheel has also dropped the front 13mm, or about 0.5°.

These same rake & trail changes I made to my Cali Stone, except my handbook lists the stock trail for a Bellagio at only 92mm. I believe that as much as the advertised stock rear wheel travel at 120mm.

Anyhow, if it gets too tank slippery we have three choices.
1. Reduce travel/ride height.
2. Increase trail with new triple clamps.
3. Crash.
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Pete Roper
GRiSO
GRiSO


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PostSubject: Re: Rear shock bump stop   Thu Oct 23, 2014 5:43 am

Eccentric bearings?
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ghezzi
Fra Cristoforo
Fra Cristoforo


Posts : 1692
Join date : 2014-05-22
Age : 59

PostSubject: Re: Rear shock bump stop   Thu Oct 23, 2014 5:58 am

I've mistakenly been called "Eccentric" before. Then it was explained to me that term was reserved for stark raving lunatics who actually made a squillion $ from their lunacy.
The rest (self included) who are still stone motherless broke, are just freakin' idiots.

Thanks for reminding me, I think it was Ghezzi & Brian had eccentric bearing kits for V11's.
Hope they're same size as Bella, at around $300 it is the cheap easy option.

Any downside to these Pete?
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Pete Roper
GRiSO
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PostSubject: Re: Rear shock bump stop   Thu Oct 23, 2014 11:48 am

I've never used them Wayne so I'm afraid I have no idea. Bearings though are the same for Bella and V11 I believe.

Pete
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ghezzi
Fra Cristoforo
Fra Cristoforo


Posts : 1692
Join date : 2014-05-22
Age : 59

PostSubject: Re: Rear shock bump stop   Fri Oct 31, 2014 12:33 am

Got message back from Bruno Saturno, they no longer make the eccentric bearing kits.

Anyhoo, Stock shock is 310mm long, GRiSO is 320 and my Matris is now 330mm eye to eye.
At full ride height my rocker ratio is 2.6:1 (overall it's 2.3:1) so I have theoretically raised the rear ride height by 52mm. That's about a full 2° reduction in rake, plus the front has dropped 13mm with the 17" wheel, = approx. another .5°.
So I now have a 25.8° rake, and 77mm of trail. Measured at static height.

Apart from my arms getting shorter (need a knew glass eye) my bloody legs seem to be getting shorter too. And the side stand.

Might go for a ride tonight Smile
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PostSubject: Re: Rear shock bump stop   Today at 8:24 pm

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