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Skinniest coil shock?

5K views 23 replies 12 participants last post by  HollyBoni 
#1 · (Edited)
I really want to try a coil shock in the back, but the space in my frame is very limited. The problem is clearance to the seat tube. The frame takes a 185x55 trunnion shock.

Which shock uses the smallest diameter coils? So far all I know is that DVO springs are supposed to be 53.30mm OD according to their support. Anything smaller than that? Also, the more distance between the lower bushing and the spring collar, the better. I printed out a DVO Jade to scale on paper and "installed it" in the frame, I think it MIGHT just fit. 😁
What if I used an offset bushing turned sideways to gain a tiny bit of clearance? Would that impact the kinematics a lot, or would it even work at all, or would the bushing rotate on it's own?
I know all of this might seem really stupid, i'm just super curious about coil shocks (and want to try just a new shock in general), but I don't want to buy a new frame yet. :)

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#5 ·
I really want to try a coil shock in the back, but the space in my frame is very limited. The problem is clearance to the seat tube. The frame takes a 185x55 trunnion shock.

Which shock uses the smallest diameter coils? So far all I know is that DVO springs are supposed to be 53.30mm OD according to their support. Anything smaller than that? Also, the more distance between the lower bushing and the spring collar, the better. I printed out a DVO Jade to scale on paper and "installed it" in the frame, I think it MIGHT just fit. [emoji16]
What if I used an offset bushing turned sideways to gain a tiny bit of clearance? Would that impact the kinematics a lot, or would it even work at all, or would the bushing rotate on it's own?
I know all of this might seem really stupid, i'm just super curious about coil shocks (and want to try just a new shock in general), but I don't want to buy a new frame yet. :)

View attachment 1963087
As a reference point a Fox steel spring (500x3.25) measures 53.4mm, the 550x3.25 I have on my bike measures 54.8mm...

These were/are fitted to a Fox DHX RC4 9.5x3.0
 
#8 ·
Is that right? I thought the Fox X2 stuff, SLS included, was a significantly larger diameter than the Bomber CR stuff. I have a Bomber CR and several springs for it. The springs are pretty tiny compared to the spring for my Jade and EXT, both of those are larger diameter.
 
#10 ·
What if I used an offset bushing turned sideways to gain a tiny bit of clearance? Would that impact the kinematics a lot, or would it even work at all, or would the bushing rotate on it's own?
I once asked the guys at offsetbushings.com if it was possible to install the offset bushings the wrong way to increase bb height. They said it won't work as the bushings tend to rotate to the slackest position
 
#15 ·
I disagree with that. my bike has an 18% progression (2.6 to 2.15) and the 2022 model COMES WITH A COIL. The team riders on the EWS circuit have been coiling my frame since 2018.
20% is fine for a coil, OP.

My advice is to get a 'cheap' one used from PinkBike (sell it if it doesn't work) or beg a favor from a local shop to test fit if possible.
 
#18 ·
My bad, you're right-- but it does matter what size shock we're talking about too.

Example: my Tallboy 4 has a stock progression of 26% but is not recommended for a coil because of the size of the shock (190*45). I thought that was because of the progression rate but apparently it's just because of the shock size. I guess I don't know how that works.
 
#20 ·
Hmm, 52.5mm is pretty skinny! So it sounds like lighter springs might have a smaller OD, which is nice because i'm around 65kg so i'd need something light. I'm fairly sure something in the 52-53mm range would clear most of the seat tube, the problematic area is the lower part.

Automotive tire Bicycle tire Automotive lighting Bicycle frame Bicycle part


The part where the red line is is at an angle, which limits space there a ton... 😠

BTW I can't find Marzocchi springs, do they come stock with the cheaper, black FOX springs like this?

 
#21 ·
Yeah, that doesn't look too good. The spring collar/perch is quite wide and relatively close to the eyelet. Maybe upside down would work better, the top of the shock is usually not as wide. But it all depends on the specific shock.
Things like this are really hard to say just from pictures, you must also test during compression all the way to bottom out, your best bet is to discuss with local shop if they have some coil shock to try. Or depending on the return policy you can always order, check for fitment and return if it doesn't work.

And yes, the black foxshox spring are the cheap option for Bomber CR. Stock the shock comes with no spring so you get to choose.

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#22 ·
Yeah, that doesn't look too good. The spring collar/perch is quite wide and relatively close to the eyelet. Maybe upside down would work better, the top of the shock is usually not as wide. But it all depends on the specific shock.
Things like this are really hard to say just from pictures, you must also test during compression all the way to bottom out, your best bet is to discuss with local shop if they have some coil shock to try. Or depending on the return policy you can always order, check for fitment and return if it doesn't work.
It's a trunnion mount so I can only mount the shock in one direction. Luckily as the suspension moves through it's travel the shock rotates forward, away from the seat tube. So if the shock clears fully extended, i'm golden (unless there are clearance issues with the reservoir).
The shops around me are absolute garbage (or most shops in general here in Hungary). If you need a 6spd freewheel you're set, but testing a coil shock on your bike? Yeah, nah... 😁

Since no one in my group rides a coil my only option would be to buy new and return it. I guess I could slightly sand down the OD of a center sleeve/reducer that would easily slide in the bushing on the shock and leave no marks, and check the fitment that way. But it's risky for sure.
 
#23 ·
Sounds like lot of issues just for coil shock. Maybe well tuned air shock is better solution.
I don't see a great difference in performance between good coil and good air shock. Yeah they feel a bit different back to back, but both usually work pretty well while riding.

I love coil for lower maintenance and no need to check pressures. That's why I have it front and back, every time I take the bike out its exactly the same as last time i rode it. Even if it feels different (many possible reasons) I don't have to chase the "maybe the pressure changed?" rabbit. But you loose a bit of adaptability to terain/style of riding.

In the end, when setup right, air and coil are both great, and seems like for your bike coil just isn't meant to be, unless there is a specific shock with workable dimensions for you.
 
#24 ·
Found this DHX2 drawing, printed it out to scale, "mounted" it in the frame.

Rectangle Font Parallel Diagram Engineering


In the spring collar area at the bottom the clearance is pretty decent, but at full extension the spring JUST contacts the seat tube. This spring is 54.6mm according to the drawing tho, so with something in the 52-53mm range I might have like 1mm of clearance...
So i'm most likely staying air. Bummer!
 
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