BRAKE JACK DOESN'T EXIST!! Advice!! with Team Robot, March 2021 42

If you like new, shiny things or a good conspiracy that blames your bike for personal riding failures, then you may want to hit up our Bike Check section or Forum. MTB ADVICE!! with Team Robot #3 is here, and it's a sobering dose of non-judgemental integrity...or at least an entertaining opinion. Vital MTB sold the corporate Yaris and used the funds to wine-and-dine Team Robot, one of internet mountain biking's most respected commenters, so he would present his bedrock of two-wheeled wisdom. This is the best mountain biking advice column on the internet.

Despite Amazon's attempts to get the patented Team Robot ADVICE!! technology for union-busting efforts, Team Robot's algorithm fended off multiple DNS attacks and processed the digital landslide of quarrelsome queries to inhale, digest and excrete answers to three barely-comprehensible conjectures worth a robot's time and CPU resources.

Answers stated by Team Robot do not necessarily (but most likely) reflect Vital MTB's stance.

Will I really feel a difference if I upgrade from my 2017 bike geo to one with a slightly slacker head tube angle and a slightly steeper seat tube angle? More importantly, will I be more likely to ride like Remy Metailler or Yoann Barelli?

-Butch

I’m of two minds to your question. Part of me says your old bike is fine, and the other side says do it, buy a new bike as soon as possible!! I’ll address these conflicting ideas in turn.

Don’t stress it, your old bike is fine. Will you notice a difference in a new bike? Probably a little. Will a new bike make you faster, or better? Probably not. There have been a lot of horrible full suspension bikes in the history of mountain biking, but by 2017 bikes were pretty darn good. By 2017, pedaling dynamics had been mostly sorted out, the design and materials were great, enduro bikes didn’t break all the time, bump absorption was great, forks and shocks were great, and brakes were great, too. The marginal changes in frame geometry since 2017 are just that- marginal. Heck, I don’t think Intense has changed the Carbine or Tracer since 2017. Unless your current bike is one that was infamously short in 2017, had a crazy-slack seat angle, a super weird suspension kinematic, or had a shock you had to pump up to a billion PSI, then you’re probably fine.

If you’d really like to try a steeper seat angle, you can do it for free right now on your current bike. Just slide your saddle forward on your seatpost and raise your post 5 mm. Similarly, if you’re bummed out on your bike’s slightly-too-steep head angle, make your fork taller. You can probably buy whatever air shaft you need to give your fork 20mm more travel, then add two volume reducers so it ramps up and you can’t use the last 20mm of travel. Voila, your fork will ride 20mm taller at all times, making your dynamic geometry slacker at all times. You’re welcome. Obviously you can’t do both of those things to the same bike, because making the fork taller will make the seat angle slacker, but you can still try either one and see how you like it. My sneaking suspicion? It’s a little nicer, but not mind blowing. You’ll still be faster than the people you’re already beating, and you’re still gonna get beat by the people who are faster than you. Similarly, if you thought a slacker head angle was gonna help you hit that monster step down at your local trails or a steeper seat angle was gonna help you unlock those 5 hour backcountry epics, I’ve got some bad news for you: it won’t.

Lastly, there’s a real joy that’s found in squeezing new life out of an old item. Restoring cars, renovating houses, and keeping an older bike in great riding shape can be a point of great pride if viewed from the right perspective. New bike sales aren’t driven by actual performance, they’re driven by consumerism. Bike customers have been carefully trained to crave newer, shinier, better, faster, stronger, more compliant, or whatever the buzzword-du-jour is. You have the opportunity to be part of the solution, instead of feeding the problem. You can be the type of person who appreciates what they have instead of obsessing over what you don’t.

Counter point: Who cares if it rides better? If you can get a new bike, you should dump that old bike and run, don’t walk, to buy a new one.

Hear me out. Buying a new bike in a year or two is gonna be like buying a house in 2021- if you don’t already have one, you already missed the party and they’re all gone. Supply is down, demand is way up, and every bike company is raising their prices over the next 4 months to reflect the new reality. You’re gonna have to buy a new bike eventually, and you’re gonna have a hell of a time buying a new bike in a year or two. Plus, the used market is never going to be stronger. Thanks to the crushing wave of new riders to the sport, your 2017 bike just went from “old” to “gold.”

Think of it from an economic perspective. The clock is ticking on your bike’s warranty, it’s not getting any younger, and you’re never going to get a better price selling it used. This is no time to harbor nostalgia or wax eloquent about the carbon footprint of mountain biking. It’s last call at the party and you gotta take care of #1 while you still can.

New bike or old, you’ll never be able to ride like Remy or Yoann. Unless by “ride like” you mean riding forward on two inline wheels.

I’d like to hear your thoughts on brake jack. Is it just a perceived myth brought on by poor setup / skill?

Why does it predominantly seem to affect single pivot frame designs (Orange, Kona)? And if it's not an actual thing, why do so many racers use elaborate custom linkages to isolate the brake from the swingarm (Danny Hart, Peaty on Orange, etc.)?

My experience is admittedly based on my old Scott Ransom that I had over 10 years ago. In 2010 I took it to race the Megavalanche (my first Alps Trip… in at the deep end) and suffered with what felt like a locked-out rear end under heavy braking. My bike setup and skill has increased a tiny bit since then so I’ve not really had any issues for a while. But I have deliberately never even considered riding or buying a single pivot bike since then, so it could be time to re-open my mind.

Cheers,

Tim Jones (aka TimBud)

Brake jack doesn’t exist. The phenomenon described by the term “brake jack” is a real thing, but it’s caused by a host of other factors- mostly bad bike setup.

The classic definition of brake jack is an extension of the rear suspension during braking events that is caused by pivot layout, brake placement, and axle path. It’s true that your bike’s rear suspension extends during braking, but it’s almost entirely a result of fork dive, not your rear suspension. When you pull the brakes, your weight shifts forward, giving you that going-over-the-handlebars sensation we all know and love. The softer your fork, the more forward weight shift you’ll feel when you pull the brakes. Even worse, as your weight shifts forward it unweights your rear shock, extending your rear suspension. And with less weight helping to compress your shock, your rear shock effectively has a higher spring rate. This makes every bump your rear wheel hits feels bigger and harsher. It’s a nasty spiral.

People were obsessed with brake jack in the late 90’s and early 2000’s, with all sorts of floating brakes contraptions from bike manufacturers and aftermarket peddlers. If you’re tracking so far, you might have realized that brake jack was a hot topic during a time when forks and bikes were terrible. From Rockshox to Marzocchi to White Brothers, everyone was running coil springs with no ramp-up built in at the end of the stroke, and damping was basically non-existent to get that “plush” small bump feeling from the factory. To compound the problem, downhill bikes had steep head angles, high bottom brackets, and short wheelbases, meaning the bikes rode less like a longboard and more like a set of roller blades on a gravel road. Forks dived like crazy, bikes were tiny little see-saws, and riders were convinced the harsh feeling at the rear wheel was coming from the brake. Luckily, forks got better and bikes got longer, lower, and slacker, so you don’t see many people complaining about brake jack much anymore.

To be fair, there is another possible benefit to floating brake arms. Rear suspension is affected by braking through a force known as “anti-rise.” Anti-rise, also known as “brake squat,” is the opposite of brake jack. Here’s a quick summary: as you pull the brakes, your rear wheel wants to stop and the rest of the bike wants to keep going forward. For bikes with a rearward axle path, the suspension compresses under braking to allow the chainstay to grow and the rear wheel to travel “back” relative to the rest of the bike. The suspension compresses under braking, thus “brake squat.” Going deeper into shock travel puts you into stiffer spring rates, making bumps feel harsher. Single pivots tend to have a more rearward axle path, so maybe that’s why they have a reputation as being harsh under braking? Bikes with high anti-rise supposedly are more stable under braking, because the rear suspension compressing should resist weight shift as your body naturally lurches up and forward during braking.

In theory, a bike with an extreme forward axle path would have the forces reversed, creating brake jack. As you brake, the bike would want to rise in its travel from the sag point. Those bikes don’t exist in reality because they’d also pedal terribly, with chain forces compressing the suspension with every pedal stroke, creating insane pedal bob.

Instead, what you will see in the field are bikes with relatively low anti-rise values. There’s no such thing as a bike with a truly vertical axle path, but rear suspension designs with a vertical-ish axle path won’t extend or compress significantly as a result of braking. Because these bikes largely isolate suspension movement from braking - they’re viewed as active under braking. That sounds cool, but the downside of isolating braking forces from suspension is that these bikes don’t actively resist forward weight shift, so they’re inherently more unstable under heavy braking. As a result of these competing design constraints, the conventional wisdom is that you can tune the anti-rise number to create a stable bike that’s harsh or a supple bike that’s unstable, but you can’t have both. Anti-rise can’t be tuned to produce a bike that’s supple and stable.

So, what’s more important, supple or stable? Asked another way, how much anti-rise is the right amount? I’d say it’s an equal dose of “no one knows” and “it doesn’t matter.” In 2018, Amaury Pierron won 3 races and the World Cup overall on a bike with insane levels of anti-rise. Apparently, no one told Amaury his suspension was harsh under braking. The next year, Loic Bruni won three races and the 2019 World Cup overall on a bike with super low levels of anti-rise. It’s true Danny Hart experimented with a floating brake arm in 2019, but Matt Walker rode the same bike and didn’t. I think either Danny or Saracen wanted to test the effects of anti-rise, but obviously it wasn’t a big issue because Matt Walker went on to win the World Cup overall in 2020 on a stock Saracen Myst, no floating brake arm in sight. I’m no World Cup Champ, but I’ve ridden lots of bikes, many of them single pivots, and I’ve never felt anything I’d call “brake jack.”

Now, let’s talk about your brake jack experience on the Scott Ransom. I think what you experienced in 2010 was a combination of factors. I looked up the geometry on a 2008 Scott Ransom and, I’m sorry to say, it’s a complete junk show. 165mm travel, 68 degree head angle, and a 420mm reach on a large. If you add in a couple other factors, like a too-soft fork, a too-stiff spring rate on your shock, or a too-slow rebound speed that was setup for your home tracks, it’s easy to imagine why your bike might have felt like garbage on your first trip to the Alps.

So repeat after me: Brake jack is not a thing.

Also, Steve Peat never had a floating brake arm on an Orange. I promise. And he was on a Littermag online issue cover.

How are the robot overlords dealing with the shortage and delay in spare parts due to the Covid 19 supply chain breakdown?

-Fionn

The ROBOTS are doing better than ever. In the last year we’ve seen self-driving cars, drones delivering packages, and widespread facial recognition software, so we’re only a few years away from Skynet.

A dare I made with myself during COVID has been to buy all my bike parts either from a local bike shop or to buy used. I have good friends working at online bike stores, so I’m not claiming that all online retailers are Amazon, or that online = pure concentrated evil. That would be overly simplistic. But I will say that, in my experience, buying from a real brick and mortar or buying used does feel a little less evil. Sometimes I have to wait a couple weeks for a special order to come into my LBS, but in 12 months of COVID, I haven’t had to buy anything online yet. Between bike shops and the used market, I’ve always been able to find what I needed and keep my old bikes running smooth.

Seriously, if you’re pulling your hair out trying to find bike parts during COVID, don’t sleep on the used market. There are so many avenues, too. Craigslist, Facebook, Ebay, and of course the Pinkbike buy/sell. If you can find someone who’s selling something they took off a new bike or rode once and didn’t want, it’s as good as new. This year I bought a like-new takeoff fork, tires, a set of pedals, a cassette, a take-off chain, and probably some other stuff used, and so far it’s all working great. Of course there are things I wouldn’t want to buy used, like brake pads or grips, or anything that you need to have a warranty on, so pick your battles.

An unexpected upside from avoiding online retailers has been a dramatically lowered rate of unplanned impulse buying. When I can’t buy exactly what I want right now, or when I have to do a little extra research to find what I’m looking for, or when I have to wait a couple days to swing by the bike shop to buy it, my “needs” change a little bit, and they start to more closely resemble my actual needs. Do I need another spare set of pedals, even if they’re on sale? Probably not. Do I need a new handlebar, even though my current one is working fine? No. Do I need a third rain jacket? Nope.

Give it a try. It’s a little more work, but I think it produces a more harmonious result.

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