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Very good point made, from my experience i have found that the data from the MI system is fairly repeatable. However, i normally go for a balance that makes sense from the data and that the rider is happy with.
Hi Slonschtor, I am hesitant to recommend Shockwiz as it does not take into consideration leverage ratios j no or the velocities at the wheel. It only looks at what happens at the shock. Also, I am not sure about the scoring and recommendations, I rather use the data.
however, some data is better than none. So ShockWiz maybe helpful to provide some data that you can use to make changes based on how you interpret the data.
Did you ever find any weird handling characteristics when you first tried the supreme v4? I managed to try one for a run or two and I felt like I was going to high side it when going around every berm, I could feel my weight being jolted forward faster than I was able to react. If so, does a mid-pivot have that same weight transfer or is it more akin to a normal pivot setup?
Disclaimer - I'm no where near the setup Guru that the OP is -
I have had a V4 Supreme (29/27) for 4 seasons. I has to be setup up differently than anything else to be able to maximize it's strengths and minimize its weaknesses. It's about as extreme of the high/growing rear center pivot as any mass produced bike in recent history. it's not something you can just jump on and feel at home with unless you're coming from a Forbidden or similar.
For me, that involved progressively running less and less rear sag and overall setting the bike up 'stiff.' It has sooo much rear travel, I think the behind the numbers series on the other site measured 220mm or more in actual travel. You simply do not want to run too deep in it. This seemed to control the rear growth in the corners and G out's while still letting the bike eat in chunk.
I tried the other way around initially (running deeper in the travel with more rear sag) rationalizing that all the rear growth would have already happened but I couldn't get along with it like that. Plus the bike jumps awful with too much rear sag. Really unpredictable on the different lips.
Definitely interested in Luis opinion on the matter!
But consider the V4 might have had a bad suspension set up that could be causing the issues. But I have owned a V4, V5 and Session. The mid pivots don't pitch as much for sure. The V4 has a very high anti-rise that squats the rear then as you let off the brake it lifts. So this could be what you are feeling. But setting up the suspension to combat these issues is what Luis is the master at.
Hi AvgMTBEnjoyer ,
i have not done much testing on the Commencal V4, but it is mainly an observation based on its kinematic profile and applying some vehicle dynamics principles. No the Mid Pivot bikes are less affected by the changes in dynamic weight distribution as it goes thru the travel.
Hey Joe,
I will be covering this topic in more detail on a later case study. I don't to give anything more at this time, haha!
Talk to you soon buddy.
Luis
I'm curious why you didn't try using a 27.5" wheel on the back with the mullet link and decided to put the 29" wheel on instead? Wouldn't that in theory mess up the geo of the bike with the mullet link on there or does the 190mm fork balance that out?
Hi Astrizzle,
First, the bike was configured like that by the owner and rider. The mx link with a 27.5 rear wheel preserves the original geometry. However, the increased in fork length due to the 190 boxxer changed the geometry significantly in head angle, reach and front center. These changes completely changed the ability to load up the front wheel efficiently, and the behavior of the bike. By using the 29er rear wheel, it raised the back end enough to correct most of the changes in reach and head angle and it improved the ability to load the front end back again. It actually workes fairly similar to the standard Jekyll or mx Jekyll with longer travel front and rear.
I hope this makes sense.
Thanks for the breakdown on that, I assumed that was the case on the geo issues with using a big fork. I think I am going to stick with a 180mm zeb fork and the mullet setup for mine. That will be as close to a full on DH bike as I can get right now with the parts I have.
But its really great to know that long-term if I wanted to go full out and make a Dual crown DH shred sled I can do it!! Did you have to use a pretty low rise bar with the 190mm fork in order to keep the front end from getting to high up as well?
Thinking about it it makes sense. A very high (single) pivot bike will have a very rearward axle path in the beginning of the travel. Running it stiff it will be proportionally more stiff (because of the axle path) in vertical squish (so pushing down on the bike, essentially throwing it into a berm), but it won't be as stiff when hitting obstacles as the force input is working more in line with the axle path. The situation is opposite with normal pivot height bikes around sag and deep in the travel for high pivot bike and effectively reversed for obstacle scenario for a low pivot bike deep in the travel (it will essentially get stiffer for vertical input events and even stifferer for obstacle events).
You could call the vertical events (berms, loading the bike, landings, etc.) handling events and the obstacle events bump absorption (that's roughly what it's called with cars as handling events cover weight transfers during accelerations and any compression/cresting events, so low speed events, while bump absorption handles any potholes, cracks, kerbs on racetracks, etc., so high speed events).
A dual crown fork at 190 mm travel will likely be about the same ATC as the 180 mm ZEB, possibly even lower. DC forks have relatively low ATCs compared to SC froks (for the travel).
Yup this is pretty much exactly what I found with high pivot bikes - although I would add it gets a little more complicated when you compare vertical leverage ratio vs the leverage perpendicular to wheel travel, as they can track in different ways through the travel so certain bikes have a narrow window between too soft and too stiff. If you have too little sag that rearward wheel path reduces sensitivity to small bumps (which are acting closer to vertical) and also the handling inputs can feel "wallowy", because the initial travel feels stiff vertically then as you gain leverage in the middle of the stroke is perceived to feel softer. The leverage ratio can be optimised to make it easier to find this balance but it is slightly less forgiving of leverage curves that aren't totally dialled.
I found the Commencal's do need to be quite stiff (they actually recommend very low sag numbers for the V4, like 15% at the shock) but bikes like the Zerode G3 need a bit more sag to hit the sweet spot due to its leverage ratio.
So it's basically all back down to what Neko is trying to do - the easiest bike to ride is the calmest, most predictable one that has the least weird stuff going on with the kinematics.
Great article Luis. I’m also a long time user of Motion Instruments for my RSR Bikeworks business and a BYB user for my Scott DH team work. Both systems are great, but MI edges it for customer setup days I think.
As said by others, the data between the two systems is quite different, so not relatable. Probably to do with the sample rates.
I do actually use max compression and rebound speeds to ‘tune’ the HSC and HSR. Then also use the average speed function to ‘tune’ LSC and LSR. Then use the 95% to balance front to rear along with the balance graphs. But otherwise, our methodology is very similar.
I do think a bike with 20% dynamic sag on the fork is a bit sporty. My take on it is that static sag should be 20% front, 30% rear as this is measured on the flat. However, dynamic sag is an average position over the entire run, so not on the flat and is taking the trail gradient in to consideration. All the testing I’ve done on my bikes (DH and enduro/trail bikes), with 100s of customers and with DH World Cup athletes, has shown better results in terms of grip, speed and comfort with front dynamic sag between 25 and 30% and rear between 27 and 33%…….with the rear always a few percent more on the rear.
That said, everyone is different and customer feedback and data results must be considered hand in hand, so sometimes you get different results.
Hi, Luis! Super interesting case study! Most of this stuff is way over my head.
I've been setting up a Jekyll myself and tinkering a bit.
I have a medium frame. I believe the frame sizes have different leverage rates.
I'm curious I'd you would recommend air or coil for this bike?
-Gary
Luis,
We're all patiently waiting for the next case study on this. I am curious your thoughts on average sag.
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