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Trail Ninja
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6,040 Posts
Discussion Starter #1
I was inspired by Karver's style in his Sun Peaks video, with 2 wheeled drifts all day:

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I compared it to his video promo for an Intense Carbine, and notice he's only drifting the rear really:

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It seems the opposite of this video of Guy Kesteven on a Specialized Status, where his front end lacks traction and he's having trouble steering:

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Why consider geo when people can adapt to the bike?

Karver, whose signature style is to break traction, seems to not adapt to nail those 2-wheeled drifts on a 29er (with 445mm CS).

Guy Kesteven, called a "super tester" among media types, failed not only to adapt to this one bike with short CS (426mm) and a front tire that's kicked way out (1256mm WB), but also fail to adapt to a Process 153 and Intense Recluse, each time confused and looking to blame something like folding a tire (despite lack of side-load forces), bad Fox 36 fork, or whatever. He's confused when a known front tire and fork combo just doesn't perform as expected on these short CS bikes.

Commenters on pinkbike and here seem to claim that adapting to bikes is what makes a pro, into a pro. From interviews, pros seem to claim that they spend the offseason dialing in their bike and getting used to it, and seem very reluctant to change things up drastically close to race season. Maybe adapting to bikes is far harder than people want to admit?

There's a sweet spot between a bike that has a front wheel that's too prone to breaking traction, and one with a rear tire that's prone to breaking loose. You can shift weight to the front to adapt to a drifty front; can also compensate with a grippier front tire (and offset the drag with a faster rolling rear tire). On a bike with a drifty rear, you can shift weight to the rear to compensate for that, and also avoid things like nose-planting (and nose-diving when mid-air), which I associate with too much weight on the front.

One might reason that it's better for the rear to break traction before the front, and might find it useful for corners, arguing that the front drifting makes for a bad time. I argue that this is a personal preference. I want to get closer to 2-wheeled drifts all day. People seem to consider short CS and "love-back-wheel" makes for a good time, which I associate with much more weight distro on the rear than on the front.

For someone who believes in heavy-feet & light-hands, how the body's CoG and the BB is centered between the wheels/axles matters. Basically, I'm implying that one should pick a bike based on out-of-the-saddle handling and balance. Oddly, people seem to be uncompromising with seated fit and comfort, always ensuring that the ETT, STA, seat tube length, reach, stack, etc. is in a familiar range...

Back in the day when people claimed that 29ers can't jump, bikes looked like this:



The chainstay length was 450mm and the front end looked like it had smashed into a wall, it was so tucked in. The wheelbase was 1131mm for a size medium. With a rider standing on the pedals with legs/hips aligned vertically, I estimate that the weight distro was probably around 55% on the rear and 45% on the front (based on how my Superfly 100's weight distro measured out).

Here's what the equivalent 29er looks like today:



There's hardly any space between the 32t chainring and tire, hinting that the CS lengths have shortened, and there's a lot more space between the crankarm and front tire, hinting that the front center has lengthened greatly. There's much praise about how this bike feels dialed, nicknaming it as a DH/enduro rider's XC bike, or a "downcountry" bike.

People seem to credit the a goldilocks amount of reach, CS length, HTA, and/or whatever else for the dialed handling that even an uncompromising gravity rider is happy with. I firmly believe it's more about balancing the weight distro, with chassis rigidity, susp, and spec also mattering. I will focus on weight distro here because geo is easier to discuss on paper.

CS length has been the subject of many heated debates, without much consensus other than that handling suffered as they got too long, like on early 29ers. People seem open to the belief that they can be too short now too, like on modern long wheelbase bikes that lack traction up front. There's been brands that proclaimed that 16.9" CS was the magic number for trail/AM bikes (e.g. Yeti), like how 71/73 were the magic numbers for competitive NORBA XC hardtails. The industry has slowed changed their tune. Norco introduced size-specific CS lengths, with some of their bikes nailing it, like their Sight, with +/- 5mm CS length change per size. Not every bike of theirs got it right, but not every bike of other brands seem to get it right. It's like it's all trial and error... YT is on a roll though, with all of their bikes being very dialed. Santa Cruz's entire line-up seems relatively dialed too, with the adjustable CS length feature finding some favor.

Steve from Vorsprung once made a bold video, suggesting that the rear center measurement (horizontal CS length) should be proportional to the front center (horizontal distance from BB to front axle). He may have been a bit too opinionated when he praised his personal bike and Sam Hill's to have a similar ratio, dividing the FC by RC. It spawned a debate, especially since he criticized a Pole, which was considered to be a peek at the future of modern geo pioneering. The issue here seemed to be that simply calculating a ratio didn't work--people tried to find other bikes that matched the goldilocks ratio, but refused to believe bikes that didn't have that ratio were any worse.

There was an effort by a few folks who measured the weight distro of their bikes with actual scales under each wheel, to determine how much % of weight was on the rear and front. People seemed to gravitate towards bikes with 60% weight on the rear and 40% up right, where bikes with more weight up front were generally more old school XC, and those with more weight on the rear were not ideal for racing and were more for hooliganism.

Long story short, all this talk reminded me of what people in motorsports racing already know. They go through great pains to distribute weight between the wheels for predictable traction on performance vehicles, especially race worthy. Bikers seem to discount this, saying it doesn't matter since a rider can shift their weight forward and back, and knowing how to do this well is a skill. They same people also seem to argue that the bike doesn't matter, and that it's all about the rider. I dunno about that, as a bike can transform a rider from crap to average, and seeing more brands offering size-specific CS lengths (or adjustable) and designing extra opportunity to upsize/downsize across their range of sizes. That, and I've noticed that bikes just simply seem to corner better in certain sizes, which for me tended to be in larger sizes (I'm 5' 7" with short inseam).

Anyone else subscribing to this belief that CS length should be proportional to the length of the bike, for something like weight distro and feel that this is way more important than trying to find some goldilocks number, or believing "shorter is better"? Santa Cruz seems to have paid extra attention to this on their V10, and the numbers look good to me (since FC isn't a common geo figure, can just compare CS to WB). I've experienced some bikes that seemed to effortlessly do 2-wheeled drifts whenever I tried to take corners a bit hot, but want a modern version of it in freeride/park style.

 

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