2 Up shock data

[whodat]

Ok, I've searched and found lots of conjecture and lots of discussion but very little hard data on the 'occasional two up rear shock'. The basics seem to be that the shock is the same as the stock f3 shock, but it has a different spring. You can't order the spring separately, so you're stuck shelling out $200 for the set. Which I did. I then immediately took it apart and took measurements.

Stock spring:

Free Length 10.75" installed length 10"
Coil diameter 3.5"
Wire diameter .440"
Active coils 5

387 lb/in

2-up spring:

Free Length 10.75" installed length 10"
Coil diameter 3.5"
Wire diameter .520
Active coils 8

496 lb/in

The calculations came from racingsuspensionproducts.com

I haven't started searching yet, but with this info it should be fairly simple to buy a spring and swap it yourself for less than the $200. Another data point is that the springs are slightly tapered at the top and bottom, with the 2-up measuring around 2.825 at the ends. Should mean that a standard 2.75" spring should fit, but that's another math thing where you have to figure out the coil's inside diameter and make sure it's larger than the shock body, which is 1.85"

Discuss.

Oh yeah, I should point out that the 10.75" free length is a red herring. The shock only has a couple inches of travel so you could easily get a shorter spring and install a spacer.

 

[troop]

Nice info ... I bought the two up shock as an accessory when I purchased my F3S. I knew after test riding it, I wanted something more adequate for my 230#. I installed the two up shock a couple days after I had it home and like it. I ride 100% solo, but do take trips with Shad luggage/luggage rack-top case installed. It works good for my purpose..

 

[Rattlebars]

Provide a link if you find the spring. THX. You are fun to watch.

 

[Bottomline2000]

well..that was interesting..It appears hypercoil has what you need..
https://www.summitracing.com/parts/...WTUT4J0wt3HrGbM2uMiinlttGbduooCcaArz_EALw_wcB

 

[PMK]

FWIW, consider if you up the spring rate by 25%, that is a pretty large change and should have the shocks internals revalved also. Not exactly sure which shock you went with, but believe you have in hand the sealed and non serviceable Sachs unit. If so, you might want to modify the shock by drilling, draining, installing a Shrader valve, then tune the fluid viscosity since mechanically the shock can not be easily opened and revalved.

 

[Mikey]

:agree: Or other wise you are going to have a nice pogo stick!!!:2thumbs:

 

[troop]

Does anyone actually know if BRP kept valving the same in the two up shock? After 7K miles, mine is riding nicely. Zero rear wheel hopping and the ride is improved nicely over the softer stock shock..

 

[Bottomline2000]

:agree: Or other wise you are going to have a nice pogo stick!!!:2thumbs:

I'd take a pogo stick over riding around on the bump stops. You could probably get away with just adding the spring, but its a band aide over the real problem. Spring only cost $70 and should be easy to replace.
I have M2 shocks on order so this was just something fun to play with.

 

[Mikey]

Let me guess, your air bag, or compressor went tit's up??

 

[PMK]

I'd take a pogo stick over riding around on the bump stops. You could probably get away with just adding the spring, but its a band aide over the real problem. Spring only cost $70 and should be easy to replace.
I have M2 shocks on order so this was just something fun to play with.

Great you are upgrading.

With a known history where some rear shocks have failed and separated. When it happens the spring goes sideways and the shock becomes two parts.

A lack of rebound damping is a common cause for these type failures regardless of the vehicle and it is never good when it happens.

 

[whodat]

Do you have any links showing this happening on an F3? I’d be interested to read about it. The shock is the same. I agree that different damping would be ideal, but the fact is that BRP is willing to warranty the vehicle with either spring so I assume smarter people than I and their lawyers have determined it’s safe. My point wasn’t to replace a Wilburs or other $750 shock, it was to provide data for those with the skills and desire to pay $75 instead of $200 for the mild upgrade. It was also to provide data points for those With the wherewithal to drop close to a thousand bucks for a shock to know what the stock and optional spring rates are.

 

[PMK]

Do you have any links showing this happening on an F3? I’d be interested to read about it. The shock is the same. I agree that different damping would be ideal, but the fact is that BRP is willing to warranty the vehicle with either spring so I assume smarter people than I and their lawyers have determined it’s safe. My point wasn’t to replace a Wilburs or other $750 shock, it was to provide data for those with the skills and desire to pay $75 instead of $200 for the mild upgrade. It was also to provide data points for those With the wherewithal to drop close to a thousand bucks for a shock to know what the stock and optional spring rates are.

Searching here can be a challenge and likely easier to win Jeopardy 5 days in a row. Somewhere in here folks have talked about their rear shocks coming apart where the shock shaft pulled out of the shock body.

I had never heard the actual damper portion of the shock was the same until your post. If so, then certainly upgrade to a Hypercoil.

 

[whodat]

https://www.spyderlovers.com/forums/showthread.php?107852-The-skinny-on-BRP-S-2-up-F3-shock

 

[Mikey]

Do you have any links showing this happening on an F3? I’d be interested to read about it. The shock is the same. I agree that different damping would be ideal, but the fact is that BRP is willing to warranty the vehicle with either spring so I assume smarter people than I and their lawyers have determined it’s safe. My point wasn’t to replace a Wilburs or other $750 shock, it was to provide data for those with the skills and desire to pay $75 instead of $200 for the mild upgrade. It was also to provide data points for those With the wherewithal to drop close to a thousand bucks for a shock to know what the stock and optional spring rates are.

Do you have the info on how far you can push that shock before you have a two part assembly?? Not every one has the tools to make this call, and if you don't do it right, how many springs can you send back till you get the right one to do what you want it to do? No ones saying it will not work, I would suggest that if you go down this alley go slow and hope you don't take it to far!!

 

[PMK]

With the confidence you have that the shocks are the same, then go for it to get the better spring on there.

I recently purchased and installed a Hypercoil on one of my other motorcycles. Very nice part and was about super inexpensive.

 

[whodat]

Again, to clarify: I bought the BRP occasional 2 up shock. It’s on my bike now. It’s a huge improvement for my application. I’m not putting a different spring on it. I just put the data out there in case someone else wants to either swap the spring themselves, or know what BRP specs for spring rates when choosing the spring for their aftermarket shocks.

 

[Bottomline2000]

Again, to clarify: I bought the BRP occasional 2 up shock. It’s on my bike now. It’s a huge improvement for my application. I’m not putting a different spring on it. I just put the data out there in case someone else wants to either swap the spring themselves, or know what BRP specs for spring rates when choosing the spring for their aftermarket shocks.

this is good info. This is a nice mod for less than$100. I doubt the shock would pogo with a 200lb+ rider and 500lb spring. My M2 ahocks are being built around a 600lb spring, but the shock is being valued accordingly. Im tempted to do this mod just to see how well it works and maybe keep it as a backup.

 

[whodat]

Remember: the spring holds you up. The shock keeps the spring on the bike. The compression damping controls the upwards travel rate against the bike’s inertia, the rebound damping controls the downward travel rate against the spring pressure. For general purposes, you want to consume roughly 1/4-1/3 of your suspension travel at normal load. The purpose of all this stuff is to keep your tire touching the ground. Comfort is a far second. An ideal suspension would exactly follow the profile of the road surface while transmitting nothing to the vehicle. That suspension doesn’t exist, so we make compromises.
And a couple of phrases that are kind of platitudes but still ring true:

The best you’ve ridden is the best you know.
Sometimes having adjustable suspension just means you can make it worse.

 

[Bottomline2000]

Remember: the spring holds you up. The shock keeps the spring on the bike. The compression damping controls the upwards travel rate against the bike’s inertia, the rebound damping controls the downward travel rate against the spring pressure. For general purposes, you want to consume roughly 1/4-1/3 of your suspension travel at normal load. The purpose of all this stuff is to keep your tire touching the ground. Comfort is a far second. An ideal suspension would exactly follow the profile of the road surface while transmitting nothing to the vehicle. That suspension doesn’t exist, so we make compromises.
And a couple of phrases that are kind of platitudes but still ring true:

The best you’ve ridden is the best you know.
Sometimes having adjustable suspension just means you can make it worse.

Completely agree with that and my compromise wil be a stiffer suspension to get the handling i want. I learned a lot about suspension setups from racing nitro rc cars of all things. If a trophy truck can keep its wheels on the ground im sure the same can be done on the street. Just a matter if you are willing to pay for it. Today's magnetic ride suspensions seems to be a step in that direction, but all out racing seems to still be static suspension setups.