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The bearing in a poly bush exists and has I think patented for bikes. https://www.instagram.com/p/Ccu0xQCM9dG/?igsh=Y3V4b3AxMjk3NWUw Same guys that developed the stem with isolation bushings. https://www.instagram.com/p/CiffPjpsIbR/?igsh=cDR1ZDZkcnB5aXhp I like the idea of having one end of the shock mount isolated on a polyurethane bushing to take up small vibration. I don't think the poly bushing would work for a main pivot but maybe for the seatstay to a rocker link pivot it might add a tuneable flex that also isolated vibration.

I found these photos of the Honda RN01 that I never noticed. Greg Minar mentioned on the, Making Up The Numbers podcast that when he went testing for Honda, the first frame they had was max stiffness. As the day went on they start drilling holes in the frame until it looked like Swiss cheese and he liked the ride feel. They went back and made the next frame to match that rigidity. So I started looking up photos and noticed there was 2 versions, one with single backbone and one had double. Not sure which was first, but cool...

I mean, look at that rear triangle, its looks ridiculously stiff. I'd want to drive over it with a truck just to develop some bearing play for comfort haha. @Ryan_Burney I'm just about to upgrade from a pretty clapped out frame, i'll see if a friend is willing to help make some bushing inserts and do some test runs. Not sure if ill get around to it, but i'd like to try it. It's a collet main pivot and rocker pivot, so if I get some PU mid durometer inserts machined I can't see why I cant just press in...

On a podcast with Dave Wiegal, he said the 3 holes in the Ironhorse Sunday link were hand drilled during test sessions to create more rider comfort.

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.