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Discussion Starter · #1 ·
Hi all,

I want to fit a swinger 4-way air or a DHX air to my prophet to be able to turn pro pedal off and also control bottom out on bigger hits. My present Float R just bottoms out all the time and does not feel plush downhill.

I'm interested to see if you guys have tried/measured or experimented with fitting a shorter shock for slacker angles, or a shock with longer stroke to get more travel. :thumbsup:

In this thread : http://forums.mtbr.com/showthread.php?t=220972&highlight=fitting+shock+size+prophet
It is told that a shock with 57mm stroke won't work in FR mode but a shock with 55mm stroke would.

The shock I'm contemplating comes in either 190 x 50 , 200 x 50 (stock size) or 200 x 56 mm.
http://www.chainreactioncycles.com/Models.aspx?ModelID=21361

If I fit the first one (190mm, i.e. 10mm shorter eye to eye than stock), will it work in FR mode to give me an even slacker angle(around 67 instead of 67.5) or will my back tire hit the seat tube on bottom out?

Will the longer stroke one (200 x 56) work or is it the same there? (Would give the bike 156mm rear travel instead of 140)

Just want opinions before I get the stock one.

Thanx
 

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Hi there,

Interesting this, as I've been hatching a plan to buy a Prophet frame and mess about a bit with rear travel and angles. I fancy replicating what Cannondale did here in the UK with the Prophet SL (120mm rear travel, 190mm eye-to-eye, 45mm stroke), but for heavy-duty UK 'all-mountain' use. I plan to use a 190mm eye-to-eye Swinger 4-Way which I already have, re-valved to suit the regressive rate on a Prophet, but also with its stroke reduced to 45mm (TF Tuned can do this for me). This should give me 120mm of rear travel, which paired with my Fox 36 Floats spaced down to 130mm travel and a reasonably light but tough build should make a great UK trail bomber. (we don't really need 6-inch travel trail bikes here...)

I guess the thing to be wary of with changing to different shock lengths and strokes is the 3:1 ratio of rear travel vs. stroke; if you go for a longer stroke, you may need to go for a longer shock or risk frame contact with the rear wheel. Equally if you go for a shorter shock, you need to have a shorter stroke. I assume the Prophet SL came with a shorter stroke shock for that very reason.

If you're just looking to sort out your bottoming out issues and get a plusher feel why not get your Float R 'Pushed'. They'll be able to give you exacly what you want. I'm running a Pushed Van R on my Gemini and it is awesome.

Finally, I believe that the Prophet has a regressive rate rear suspension design, and consequently any rear shock change needs to take this into account (or risk bottoming out easily - right?).

Cheers.
 

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Discussion Starter · #3 ·
Dusty Lilac said:
Hi there,

Interesting this, as I've been hatching a plan to buy a Prophet frame and mess about a bit with rear travel and angles. I fancy replicating what Cannondale did here in the UK with the Prophet SL (120mm rear travel, 190mm eye-to-eye, 45mm stroke), but for heavy-duty UK 'all-mountain' use. I plan to use a 190mm eye-to-eye Swinger 4-Way which I already have, re-valved to suit the regressive rate on a Prophet, but also with its stroke reduced to 45mm (TF Tuned can do this for me). This should give me 120mm of rear travel, which paired with my Fox 36 Floats spaced down to 130mm travel and a reasonably light but tough build should make a great UK trail bomber. (we don't really need 6-inch travel trail bikes here...)

I guess the thing to be wary of with changing to different shock lengths and strokes is the 3:1 ratio of rear travel vs. stroke; if you go for a longer stroke, you may need to go for a longer shock or risk frame contact with the rear wheel. Equally if you go for a shorter shock, you need to have a shorter stroke. I assume the Prophet SL came with a shorter stroke shock for that very reason.

If you're just looking to sort out your bottoming out issues and get a plusher feel why not get your Float R 'Pushed'. They'll be able to give you exacly what you want. I'm running a Pushed Van R on my Gemini and it is awesome.

Finally, I believe that the Prophet has a regressive rate rear suspension design, and consequently any rear shock change needs to take this into account (or risk bottoming out easily - right?).

Cheers.
First, thanks for a very good reply!

You are right about shorter shocks needing shorter stroke and vice versa, I'm just enquiring what the exact limit is. If I have 2mm clearance to my seat tube at full bottom out with decent tires, that's enough. But difficult to know. I guess I will have to remove the shock and measure where the rear wheel is with a simulated 190mm shock with 50mm stroke bottomes out (i. e. 140 mm eye to eye between swing arm holes and top tube hole)

The spring rate is regressive, that's why I was going for the 4-way. Since you can control the SPV volume, i.e. progression my thought is to use this to counter that regressivity.

So you say pushing the Float could valve it to counter bottom out? The main thing then is the unability to switch pro pedal on and off... for trail riding vs downhilling. That could easily be done on a 4way / DHX air.

What I'm after is the same as you, a single track trail bomber. Do not need more travel than 140mm really, but could like a bit slacker head tube angle for alpine descending..(the rest of my build is FR light/hardcore AM at the moment)

Otherwise it's just going to be between pushing my Float R and buying a 200 x 50 4-way. The new shock won't be much more expensive if I sell the float and take that into account.

Will have to get some second opinions on that PUSH tuning, which sounds good.

Thanks again for all input!
 

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I see where you are coming from with your thoughts regarding the 4-Way/regressive rate, good thinking!

A couple of links that may be useful:

More info on Pushing a Float

http://www.tftunedshox.com/push-rear-shock-upgrades/fox-push-upgrades.html

Also, I got this part for my Gemini which whilst doing its job of preventing the fork crown from hitting the downtube also slackened the head angle a fair bit. Don't know what headset you are using, but this may help?

http://www.cannondale.com/asset/iu_files/techcenter/2006_prophet_mx1_mx2_gemini_900_2006_headset_technote_en.pdf
 

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I went to a Vanilla R coil, 7.875 (200) x 2.25 (57) to get a plusher ride, more travel. I couldn't put it in the FR setting, but since my current fork is over spec at 150mm I figure it's a wash, it's perfect for New England trail/DH stuff. That said, I'm a bit of a travel whore and I'm thinking now of going up to a 160mm fork. That would be a way for you to get that slacker angle without having to mess too much with the shock length. I just know sooner or later this Prophet will be sporting a Monster T...
 

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Discussion Starter · #9 ·
Yeah sorry for posting in metric. The prophet I linked to aboce has a 7.875x2.25 Sized roco fitted in FR-mode, which should not work. Maybe it does with the right tires?
 

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my 2 cents

Hi, i was looking into the rear end on my Cannondale prophet, and it doesn't look like it's a 1:3 ratio, the actual physical ratio of pivot to rear axle (464mm) and pivot to shock bolt (191mm) is 2.43:1, which with the stock shock stroke (50mm) only gives about 121mm of travel, so the regressive design allows an amount of extension or slip to travel. Even if you just divide the travel by the stroke you don't get a ratio of 3:1, you get 2.8:1. So using Cannondale's frame travel "140mm" i worked out possible travels on the frame using a 200/50, 200/57, and 216/63.5 shock. (i was also thinking that the lower ratio 2.42:1 means less air pressure is needed to set an amount of sag, and therefore there is also less air, ramping spring rate slower also compounded by the regressive action)

here are the numbers;

2.43-RR (464/191)-(axle to pivot, shock bolt to pivot, Real Ratio)

50 x 2.43 = 121.5mm

121.5 / 140 = 0.868 (regressive slip ratio, using Cannondale's frame travel)

121.5 / 0.868 = 140mm (end travel affirmed using slip ratio)

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57 x 2.43 = 138.5mm
138.5 / 0.868 = 159.5mm (travel calculated using slip ratio using 57mm stroke shock)

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63.5 x 2.43 = 154.3mm

154.3 / 0.868 = 177.76mm (travel calculated using slip ratio using 63.5mm stroke shock)

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2.8-ER (140/50)-(Cannondale's frame travel divided by stroke ratio, End Ratio)

50 x 2.8 = 140mm (travel calculated using frame ratio using 50mm stroke shock)

57 x 2.8 = 159mm (travel calculated using frame ratio using 57mm stroke shock)

63.5 x 2.8 = 177.8mm (travel calculated using frame ratio using 63.5mm stroke shock)

Any feedback welcome.
 

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I have a 200 x 57 on my Prophet. I ride in XC setting so the tire does not make contact on full compression. I haven't tried it in FR setting, so I can't say it doesn't work.
 

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I have a PUSHED float R at my house right now. I replaced her with a RP23. once i blow this sucker up on my prophet i Will send it off to PUSHED and get it set up for the way i ride. My Pushed float R changed the way my prophet handled and the rear end felt way stronger and i used less travel on my shock.
 

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Discussion Starter · #13 ·
Prophet Julio said:
I have a 200 x 57 on my Prophet. I ride in XC setting so the tire does not make contact on full compression. I haven't tried it in FR setting, so I can't say it doesn't work.
Could you please try it in FR-setting for a ride and maybe also try a drop and see if it works without rubbing the seat tube?
 

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hi, i think the max theoretical shock stroke is something like 71~74mm, worked out by taking the shock out, fully extend the suspension, take a i2i measurement, fully compress the suspension, take another i2i measurement and subtract one from the other, but the max i2i seems to be about 213mm or so, i'm running a 216mm 64mm DHX5.0 in the FR setting, with slightly modded mount eye, before that i was running a 200x57 in the FR setting with out any problems.
 

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Discussion Starter · #15 ·
Capt_Monkeyboy said:
before that i was running a 200x57 in the FR setting with out any problems.
Great news, thank you!:)
 

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as ever though, check it out your self, differences in tyres, shocks or pressures might create an issue for you, just move to the FR setting, put a low pressure in the shock, bottom the shock out and have a look at the clearance.

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