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Added a comment about news blog FINAL RESULTS - Maribor World Cup Downhill 8/15/2021 5:23 AM
jeff.brines

Can we get Cedric on the English feed at some point wink - That'd be a blast.

This news blog has 27 comments.

Added a comment about product review Vital Test Sessions - Pivot Firebird 8/13/2021 5:49 AM
jeff.brines

The whole idea behind scales is so you don't have to guess, you can actually measure where the mass is being carried. While I've obviously tested this extensively on myself, I've also put other riders through my "system" with similar results. If a taller rider is having problems weighting the front of the bike, the scales tell the story every single time.

As far as your fit goes, that may just be something that works for you, and your body's "geometry". However, one thing I failed to mention, is I put a clock on everything too. I'm not just having less arm fatigue but I'm faster with a much smaller standard deviation of times. I can knock out my fastest time over and over and over when the balance is there. On the longer reaches with the shorter stays, I may be close to my fastest time (but not quiet 'on it') all the while the SD is very high.

I could certainly ride a bike with a super long reach and feel comfortable, but when I'm actually pushing the limits of what I can do from a speed perspective, that's where I'd really start to notice upper body fatigue. I personally want my legs to be what is fatiguing fastest, being they are the strongest group of muscles on my body. It is a lot easier to stay standing than it is to stay in pushup position. Again, if I'm really not pushing the limits of what I'm capable of, or noodling around, all bets are off here.

What I'm calling for may not be for everyone, and may also not be something everyone takes advantage of. HOWEVER, if you are a racer, which a lot of people are, its a MASSIVE advantage to get to be able to set your bike up in a way that helps you naturally weight the bike as you want it to be weighted. I cannot emphasize this enough.

Every moto has a massive amount of swingarm adjustment. Nobody is revalving shit if they use the adjustment. I'd wager mtb would be the same, especially in the world of Float X2s and similar.

There are a lot of ways you can build an adjustable rear end into a bike, and every way I'd do it would target the dropouts itself. Not a whole chainstay/seatstay/etc. Look at how SC made a longer rear end for Greg. This is one example. Hell, there are also ways you can use a horizontal dropout with a piece that is machined that slides in the dropout for your brake/derailleur hanger.

Until you try this, and actually throw down to have a few different reaches of the same bike (that you like), its hard to really understand how important this stuff can be.

I've been fortunate enough to do so, and like I said, the results have been amazing.

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This product_review has 79 comments.

Added reply in a thread Gwin not representing US at World Championships? (WTF?) 8/12/2021 12:52 PM

As always, the peanut gallery again looks like we have zero idea what we are talking about (because, we don't). Nuance, turns out, is everything. Thanks for taking the time to update us superfans, best of luck recovering. Keep your head up.

Added reply in a thread Gwin not representing US at World Championships? (WTF?) 8/12/2021 9:22 AM

I'll probably regret asking this, but what do you mean "He and most others are going to starve next season and probably a few to come because of all this Covid crap"? The industry is absolutely crushing it...

Added a comment about product review Vital Test Sessions - Pivot Firebird 8/12/2021 6:00 AM
jeff.brines

Robot beat me to it.

I could write an entire dissertation on the subject. Ultimately yes, rider size does matter and will change the outcome. However, your big flaw is thinking size alone will somehow fix the weight distribution so long as the rider is on the "recommended size". Few reasons why...

1) As TR illustrated, your assumptions are a bit off from the get go. I could illustrate this using MS Paint but I'll spare you wink - Though your own specific height, arms, legs, torso etc all matter (a lot), rider size does not compensate enough to put your weight in the right spot by some magic variable just because you picked the right reach. To add, The larger the bike, the bigger the sweet spot will be (balance wise) but if its way out in front of you, its going to be harder to get there (again based on WHERE we carry our weight as humans). This is important. Another way to look at this - skiing. Mount points change even though skier size also changes. Why? Because of how we carry weight (I know, different sport, but there is a common thread)

2) Most companies do not objectively test with a big enough sample to verify handling traits across the entire lineup of sizes. It'd take way too long, is riddled with lurking variables and its far more an art than a science. Otherwise you can't explain reaches arbitrarily growing 20-40mm for no reason other than "I like it" over the last decade. My point here is height suggestions have little to do with weight distribution. In fact, I'd argue this is a relatively new idea for most bike companies (having been behind the scenes with a few - I've never even heard of it).

3) What I *really* want is adjustable chainstays. And I want them adjustable by a rather large margin - there are clever ways to do this. This actually allows me to vary the fit of the bike and allows the rider to pick the reach they feel most comfortable with, being reach is what the rider feels. From there, a person's own biometrics will dictate the rest, and if I can adjust the rear center, I can adjust front wheel weighting very easily. I know there are problems with this, as in the damper would require a different tune as you change the leverage ratio substantially, but in the land of $13,000 bikes, I think we can handle this.

The proof, for me, has been in my own experience. At 6'2" I'm often in between sizes. I've tried reaches all the way to 510mm, and as small as 460mm (this is in the last 5 years). I'd much prefer being on the shorter reach than the uber long reach, even if I am cramped. This isn't because of cockpit feel or "limosining through corners", its because until more recently, CSs were on the short side. I couldn't go too long without a ton of arm fatigue.

The sweet spot for me is reach of 470-480mm, 63-64 HTA, 37-44mm offset, 35-50mm stem, 445+ stays (current bike is 442 and its fine). On a bike like this, my legs, not arms, get fatigued going downhill. Legs are much stronger than my weeny arms. So I have more fun and rider more betterer. I could see extending my rear end further, too.

Again, this is for those racing. Looking to go fast down a hill for extended periods of time while staying in control and not "fighting" the bike or becoming overly fatigued. For those looking for playfulness, ride park endlessly with no care of lap time or even if I was looking to build a slalom bike - I'd throw this out the window because, for instance, slalom involves 30 seconds of riding - I can alter my body position IMMENSLY for this window of time.

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This product_review has 79 comments.

Added reply in a thread Gwin not representing US at World Championships? (WTF?) 8/11/2021 9:05 PM

I'll just flat ask the question... With how close WCs are to Maribor, at what point does Gwin give his spot up? If he can't race this weekend, but somehow can be at full strength at WCs, more power to him. Love to see him crush it. However, that seems ... more »

Liked a comment on the item Vital Test Sessions - Pivot Firebird 8/11/2021 4:48 PM

Grizzatom, respectfully, I disagree that a rider's center of mass is typically in front of the bb spindle when they're standing in a DH body position. Butts are typically behind the seat and above the rear tire. If your body position was truly centered...more

Added a comment about product review Vital Test Sessions - Pivot Firebird 8/11/2021 5:15 AM
jeff.brines

One more thing to add here...

If you ever find a bike that you feel is effortless to weight properly, EG: you feel like you aren't moving fore/aft a lot to keep weight where you want, throw it on the scales. Write down the weight on the front, weight on the back.

Now look at the bike's front center and compare it to the rear center.

Front center is a much better gauge of how you will actually weight the bike being HA & offset is included in that number. Reach alone doesn't include these two massively important variables. When buying future bikes try and keep all this close (proportions).

To be honest, I'd like to see "mountain bike fitting" with weighting being the big data point. Lots of testing would need to be undertaken to figure out what *actually* works, for who and how it varies discipline to discipline. From there you could take certain inputs - like the kind of terrain a rider finds themselves in, if they race, skill level, arm length, torso length, inseam length etc. etc. and better fit someone on a bike or better steer them to a bike that will handle for their desires. Especially important now that bikes are all "pretty damn good" with the big difference between them little things with respect to fit.

Until we get fully adjustable chainstays, (or if we ever do) it'll be hard to play with balance too much. Really all we've got is cleat position, stem, offset (to some extent), stack/rise and some wiggle room on suspension. Obviously, a lot of these impact other riding & fit characteristics too.

This product_review has 79 comments.

Added reply in a thread Fox 38 Grip2 very harsh/poor small bump sensitivity 8/11/2021 4:07 AM

Likely bushings have migrated or something isn't totally straight. Second most likely scenario is you are using fluid that is causing seal swell. Either way, this one is going to need to go to a service center to really figure out.

Liked a comment on the item Vital Test Sessions - Pivot Firebird 8/10/2021 6:26 PM

Roger that. I recall seeing your input with the scales, something that would be cool for us to do at the Vital offices for sure. Fully on board with your take on biometrics too. I'm a medium-sized human with relatively short legs/long torso and feel that...more

Liked a comment on the item Vital Test Sessions - Pivot Firebird 8/10/2021 6:25 PM

Jeff, you're 100% right about headsets, hubs, and frame pivots. All press-fit, not a big issue. I don't know whether bb shells can really wallow out or expand from having too many cups pressed into them, so I don't know if it's a legitimate fear. But, I...more

Added a comment about product review Vital Test Sessions - Pivot Firebird 8/10/2021 2:27 PM
jeff.brines

I'm with you and TR and agree press fit sucks relative to threads, but I'd still ride one. Its not THAT big of a deal. Don't forget, MOST bearings are press fit on your bike, car, motorcycle etc. Example: I've swapped bearings on an old rear hub probably 6 times, still fine. No suggestion of "tolerance loss" or "worse fit".

This product_review has 79 comments.

Liked a comment on the item Vital Test Sessions - Pivot Firebird 8/10/2021 2:08 PM

Primoz, I feel like you gave a really long explanation for why 30mm spindles are dumb, not a convincing argument for why press fits are good. You said press fits make "carbon bikes MUCH cheaper (with no effect for us consumer)," but the whole reason people...more

Liked a comment on the item Vital Test Sessions - Pivot Firebird 8/10/2021 1:24 PM

Yeah, I love that I need a multi-hundred dollar at-home bearing press to replace a regular wear item. Way better than threads. Even better, if I don't have that multi-hundred dollar bearing press on hand, I get to wait for three weeks to make it onto my...more

Liked a comment on the item Vital Test Sessions - Pivot Firebird 8/10/2021 1:23 PM

Yeah, I love that I need a multi-hundred dollar at-home bearing press to replace a regular wear item. Way better than threads. Even better, if I don't have that multi-hundred dollar bearing press on hand, I get to wait for three weeks to make it onto my...more

Added a comment about product review Vital Test Sessions - Pivot Firebird 8/10/2021 1:05 PM
jeff.brines

Quick math = the following...

Front Center/CS Length
Reach/CS Length

Note how different the proportions get as the reach grows longer by 10s of mms whereas the chainstays only grow a handful of mms.

The best way to "test" this is to put a medium and large bike of the same brand and model on two scales (front wheel, back wheel). Then put the rider on the bike in "riding" position. Keep all variables static (sag, stem, offset etc).

Note the differential in what the scales say. What this means is a larger bike with shorter (proportionally) css will require more active weighting of the front wheel.

I don't have a magic number I look for, but I do know if the bike has less than 450mm cs length, and I'm on something more than 475mm reach, I'm probably going to get a lot more upper body fatigue if I'm really trying to race the thing. Its a bit ancedotal, but watching how quiet Sam Hill was on his old Nukeproof with a 450 reach and 450 stays was pretty wild. He's Sam Hill obviously, not some hack from Idaho, but its still an interesting data point.

A rider's own "biometrics" will weigh into this heavily, too. Which is why, again, I say put the bike on the scales then learn what you can learn in the field.

If you aren't racing or looking for outright speed, throw what I said out the window. The same way guys can ski on skis that are center mount, we can all ride bikes with wonky geo for various applications.

My $0.02.

This product_review has 79 comments.

Liked a comment on the item Vital Test Sessions - Pivot Firebird 8/10/2021 12:53 PM

Jeff, I think it's a case of "less worse" for the bigger sizes.

Added a comment about product review Vital Test Sessions - Pivot Firebird 8/10/2021 11:16 AM
jeff.brines

Just doing some quick math, they are relatively much shorter in a large, XL than a medium. I know they do proportional chainstays, but they are not even close to keeping weight distribution "static" across all sizes.

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This product_review has 79 comments.

Added reply in a thread Gwin not representing US at World Championships? (WTF?) 8/9/2021 12:27 PM

Apologies for the political banter. Not psyched to see Gwin perpetually lit up just because he believes something that might go against the "norm" in bike culture. Back to the topic at hand, I think this outcome is the right outcome, despite how much ... more »

Added reply in a thread Gwin not representing US at World Championships? (WTF?) 8/8/2021 8:46 AM

...that's what I wrote. He's top ten of all time, for sure. Top 5 is probably more accurate. Only reason I didn't write "top 5" is I don't think you can compare the old school guys to the modern era and didn't want to be disrespectful to the old guard. ... more »