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So your saying my options are, put skateboard wheels in my pivots, or stay drilling holes in my stays until it's flexy enough. I like these ideas

Be very careful with poly mounted bearings. Don't just throw them in a poly sleeve and straight into the frame. That will eat the pivot bearing. You'd need either a poly mounted tube to press the bearings in where the tube is strong enough to connect the two bearings so they move in unison, or a poly tube going through the bearings into which the pivot axle is inserted. It would probably be easier to make a carbon chainstay that is the right amount and right direction of flexy vs. a poly mounted main pivot...

I don’t think you need to go that far to have flex bushings, my steel frame and modified aluminum rear end from Trek session can give you that feeling. That’s just from using tubing that isn’t as rigid and me removing some of the seatstay and chainstay bridges. My personal opinion is that brands just don’t need to make the bikes so rigid.

Do you think it's possible to make a test frame where you mount the rear triangle to the front with bushings that can allow the rear to turn 2-3 degrees? I'm imagining a dual link frame design so you have a solid triangle and before it joints with the 2 short links you make a link that has a bushing (and stopper) that allows side to side movement only? I think test riding something like that would be really essential to understanding flex parameters and what feels good.

Idea for compliance. Pivot bearings set in a polyurethane bushing. Different durometer bushings to tune the amount of flex.

I wouldn't say it's doing weird things here, but it does look weird. It's "just" flexing. But it does look a bit hectic. It's a perfect illustration as to why frame compliance and wheel flex is important. The way I think about it is this (could be totally wrong), he's pushed aggressively hard into the corner, the front is tracking perfectly as it has an axle to pivot on (the fork) and thus flex isn't really an issue up front. The rear wheel of a bike/motorbike will always understeer in a corner, which is an issue in berms, as it...

World Cup DH frame modifications

I have nothing of value to contribute but keep it coming nerds, this is so interesting to read

The bike is not fun to ride in this setting. (setup for countershox but removed). Much more feedback to my hands and less planted bike. It felt like it was deflecting all the way down the trail. I did a test recording axle and bar movements with and without countershox. There is an article on PB that has all the graphs and results. https://www.pinkbike.com/news/first-look-countersycles-tuned-mass-dampe… I have no horse in the race, I’m just a rider who’s trying to make his bike feel awesome and enjoys testing. I’ve tried a lot of stuff on my bike that didn’t make a difference...

Im sorry I am late to this discussion, I missed where anyone brought up the topic of spoke tension and how that plays into the frame Roll and Wag. OOOOO and rim material.

Yeah I agree with this and with @Erwan_Ghesquiere views, the companies can definitely test, but I do understand if they don't publish the data. I think an interesting point is there isn't really an engineering or rider based objective standard of what is good or bad flex yet, we are still at the stage of figuring out whats good, let alone specifically designing for it. In the broadest sense, everyone can agree that "wind-up" flex from a frame is undesirable, i.e the frame can wind up in a corner and spring back aggressively losing traction and control exiting corners. Also...

There was a bike with sliders that came up recently, but also the 1st gen Intense M1, which had a strut rather than linkage activated single pivot design, used sliders. Having said that, the M1 suddenly became a lot more successful in racing when they switched to the 2nd gen without sliders, although there are other variables involved.

I don't think the slider is the best approach. If anything it will just kill your shock quicker as it prys off your seattube. Just add a brace between the pivot and shock mount to make that stiff. My frame has a pretty tight gap from rear end to seattube (1/4") and it has never touched, even with spherical bearings on the shock. Most movement or flex is rotation behind the pivot point. A bridge behind the seattube will help and a stiffer axle interface. I run a BMX style bolt on 135 hub with right washers to remove axle...

Someone built a steel frame incorporating the slider idea I to it. I can't recall off the top of my head who the builder is to find the IG link. Igus sells a filament that would work well for this, now sure difficult it is to print on a consumer FDM printer.

Ryan, those sliders are a cool idea! Erwan, if you interested or need, I could help you print some and send them over