Frame Design

Bit of a shop rat question. I know santa cruz have lifetine warrantee on pivots but im wondering how much a shop would charge for labour to replace all the pivots? Is there a bike company that has the easiest most inexpensive pivot replacement set up? Im kind of looking at devinci as well

I'm super frustrated, as this has happened to my previous design as well. 

My single pivots keep cracking right here, around the main pivot shell. I knew this would be a high stress area so I even added a gusset here. My guess is that the angle between this gusset and the downtube is too acute and putting stress on the weld, causing the crack. 

What are people's recommendation? Add yet another gusset on top at a shallower angle? or just change the angle of the existing one? 

This is a short travel titanium single pivot that hasn't been hucked off anything more than probably 5 feet. 

if theres a way to do one smooth gusset, thats the move cause a lot of sharp corners are going to cause a lot of stress in a small area.

Could also help if i could see the frame woithout the rear triangle on it and where specifically the cracks are helping. 

Does this give you a better view? 


So you're saying just modify the existing gusset to meet the downtube at a less sharp angle, like this below?

On my current build I have used a set of plates to tie the bb/main pivot/shock mount all together with the downtube. So far it has worked well. The plates are probably a touch on the thin side, I had Send Cut Send do them and they have limited options in 4130. 

Mainly talking about where the gusset sections meet each other and the frame to make a sharp angle. That 4030 plate looks really cool!

Titanium for now. 

I'm exploring steel for an ebike. 

Maybe you could increase the wall thickness of the down tube in addition to the gusset with a shallower angle?

Hi guys, i'm about to build a frame with the help of a local builder. It's going to be a single pivot and i was wondering about the pivot placement: above the BB or concentric to the BB ? 140mm of travel with 230x65 shock. What would you suggest and why ? 

Definitely not concentric. 

i totally get where you are coming from about concentric, for a dirt jumper that could be the way to go. For a trail bike you definitely wont want to go concentric. the construction is a little more challenging but the kinematics wont come out the way youd likely want it for a trail bike. single pivot layouts tend to have a linear leverage rate. as for the length and stroke for the shock, most bike companies run 50-55mm of stroke for a bike around 140 mm of travel. cascade components had a good explanation about it in this forum. they know what they are talking about. 

Above the BB - a concentric pivot has extremely low anti squat and anti rise characteristics so is pretty awful and hyperactive under pedaling and braking. Have you played with linkage software at all? Most single pivot bikes are around the top of the chainring because it has an OK balance of pedaling efficiency without too many drawbacks

Agreed on the 55 mm shock. The 65 mm shock will actually have low pressures. I ran about 150 psi in the SDLX on my Bird Aeris AM9 at 150 mm travel at 75ish kg. 

The main problem with a leverage ratio that low is that you will have problems finding a shock with a tune opened enough for it to work properly... 

Thank you all for the answers ! I was also perplexes when the builder proposed the concentric option...so i asked here.

Regarding the shock longer than usual: i'm kind of heavy 96kg and i do drops that many will describe as dumb and useless, currently on a raaw jibb with a progressive 550-670 or 700lbs coil, i was hoping that with this layout i could use a lighter spring and have both better tracking and better bottom out resistance, the shock will be a canecreek kitzuma to have a wide compression range.

What about an air shock and/or a progressive linkage frame design? 

I don't really like how they perform and reliability is not up to the task in my experience.

Regarding a progressive linkage, i would like to try it but in a second iteration similar to stanton (they use both a linkage and a long shock 230x65 for 140mm of travel) with this frame i would like to learn the basics.