Spoonrobot 

I extremely skeptical of the full inch of movement, barring any evidence from you I think your figure is not grounded in reality. It's much higher than Rinard tested any of his forks and higher than the Heine video above indicates. I did see a blurb in the latest BQ about forks flexing up to 20mm (3/4") but I do not recall what his actual testing showed. Would be happy to see something confirming your number.

63rickert

Yeah, carbon rims have been past the 30mm mark for a while. My brain is on aluminium. The new Cannondale comes with 23c Rubino tires that inflate to 26mm on that rim. Funny an $11,000 bike comes with second line tires. The ad copy also says the bike is designed for 26-28mm tires, though some 30mm tires might work. Staggering versatility there. Modern design at it's best.

In other news Rotor announces new 13 speed cassette. Gotta have it.

So does your fork crown have 9mm clearance to spare? Something in reserve for the really big bumps? I try not to pay that much attention to modern bikes, my impression is most of them lack much clearance anywhere for anything. And thus they need to be stiff. And thus the designers head for wider and more forgiving tires. There are good reasons for wide tires and unfortunate reasons for wide tires.

"Send in the clowns. Oh wait, they're already here."

Kontact

I would hope that anyone reading this would understand that "poor riding" is a personal opinion based on whether I like stiff forks or not. But the fact that disc forks MUST be stiffer than required to support and steer the bicycle is a fact. Read any article talking about the requirements for discs and there will be a quote from manufacturers acknowledging this necessity.

At the same time, we are in another "make everything stiff" period, and everyone likes to pretend that cyclists need tapered steerer tubes or their front ends will be noodles, and that is pure malarky. Bike designers loved the all carbon forks that were available at the tail end of the 1" steerer era and no one in the pro peloton has complained about scary descents since the TVT type framesets went away in the early '90s. A 1" Alpha Q fork or even an EMS or HSc have excellent road manners.

What is actually happening is that massive downtubes are wasteful when combined with skinny steerers, so designers oversized the fork to match the frames. And with the rise of disc road bikes, there is absolutely no incentive for Trek or Specialized to offer rim brake bikes with softer rides because that would be tantamount to admitting that a disc bike has a limitation. Make everything appear even and you don't taint your sales.

With brands telling us that ultra stiffness is normal, is it any wonder that no one notices it isn't necessary? And is it any surprise that suddenly the tires people used to ride centuries on are too hard? The bikes. wheels and especially forks have removed all the suspension they had to the point that we are in denial about how well an old Litespeed with an EMS fork or a 5500 OCLV frameset rode.

Kontact

I'm not sure why you're not understanding. The fork doesn't get shorter, it changes angle. It is a swing arm. Why would the crown get closer?

dddd

I'm not in denial about the superiority of braking power and modulation that is reported for modern disc brakes, and Road Bike Action has been quite pro-disc in their reviews, but their latest test of the Scott Foil caught my eye.

The reviewer noted that the latest disc-braked version was heavier. Quoting the July 2018 issue of RBA, the reviewer (a previous Scott Foil owner as it happens), "Along those lines, I was surprised to find that the new Foil weighed 1.7 pounds more than my old bike".

That's especially remarkable in that his older bike was a 2013 model, so the older bike's similarly-Ultegra parts should have been heavier to start with. So this suggests that, after increasing tire and rim width to perhaps match the ride quality of the older model, that the total weight penalty of adding discs was about two full pounds. I am not surprised by this, as the lengthened and greatly intensified load paths of braking forces being fed through frame, fork, discs and wheels requires a lot of extra material to maintain an equal level of durability, even in a five-years-newer design.
The payback for all this is that braking performance is improved, while tread life and traction also benefit from the wider and softer tires. The buyer gets to be the judge of whether this is all worth it.

I just bought this lightly-used 15-pound bike for under 1.5k, and had to wonder how much that a disc-braked road bike of similar weight would have to cost?

Kontact

It was a guesstimate looking down while riding. Would you prefer 20mm on my flexible Icon fork? Okay, it was 20mm.

Joe Bikerider

Spoonrobot 

This is an excellent point that has really been swept under the rug both by the manufacturers and the end users who lose objectivity due to emotional attachment to new purchases. It's especially egregious in the allroad categories where steel bikes with 47mm tires ride like the Cannondale crit bikes of old but the riders have no idea as they see the large tires and think the bike must be comfortable.

Ah I understand now, thank you for clarifying.

TenGrainBread 

I definitely agree that the marketing speak around stiffness is total nonsense. But I find your claim that the move to wider tires is simply a ploy to cover up the discomfort caused by ultrastiff modern frames to be in the realm of conspiracy theory.

I don't think modern frames are "ultra-stiff" compared to C&V bikes. All of these manufacturers sell bikes that use hydroformed tubing or carbon layup that is meant to promote frame flex ("vertical compliance" in marketing speak). Yes, they talk a lot of nonsense about the importance of stiffness, but the bikes are pretty much just as comfortable as days past. Perhaps in the early days of OS frame tubing there were many ultra-stuff bikes, but not really any more. The race bikes are stiff but not really unforgiving, like an old Cdale Crit would be.

gugie 

It's not a swing arm. The fork bends mostly down near the dropout, where the diameter is smaller. That's a fact. I've reraked forks quite a bit, and measure clearance before and after. Add rake, tire to fork crown distance decreases. My fork reraker bends the forks only at the curvature, which is where a fork mostly bends when in use. I just bend it past the elastic deformation point so it's permanent.

If you're interested in the math behind it, Tom Matchak wrote the definitive paper.

Anecdotally, my commuter bike doesn't have much clearance in the fender at the fork crown. When I hit a pothole, the tire rubs on the fender.

Kontact

That isn't what I claimed. I said that interest in wide tires are coming after forks got stiffer than they were 10 years ago. I don't know what you consider the age of C&V bikes, but the bikes that I would rate as having the nicest overall ride characteristics for both comfort and efficiency were in the mid-90s to maybe 8 years ago when forks started getting big.

It isn't a swing arm, but that's the allusion I used to someone who's post suggested they think a rigid fork moves linearly like a shock fork. The reality is as you describe, and there's no reason to think that the crown is going to get crowded by a bending moment along the blades.

What part of your fender gets rubbed?

dddd

It is typically the case that (in the interest of reduced weight) as a tubular structure achieves higher strength-to-weight, that the ability to tune the flexibility of such a structure becomes much more difficult.

Thus, large-section frame members are usually more stiff.

And with these tapered steer tubes, the required larger-diameter lower bearing sees more-localized contact force for any given amount of angular flex at the crown, so the steer tube must be kept as rigid as practical in the absence of some kind of spherical seating for the bearing.
Add in the disc-brake requirement that the left leg must now handle concentrated braking torque input that now resolves over a four-times shorter distance (and now along just the one leg), and the formerly flexible fork structure must now be kept virtually rigid, despite any claims to the contrary.

The claims of today's carbon frame's improved compliance thus must be focused on the rear of the frame, and along the seatpost. Any gains at the front now have to come from the tires.

Fortunately, most of today's framesets get along with most road conditions (of the sort I am most familiar with) using as small as a 25mm tire, which happens to be a very practical size in terms of weight and air resistance. But when road conditions are less than good, giving away a frameset's fork compliance isn't a good thing.

Stormy Archer

I like skinny tires because my local bike co op has a bunch of nice ones for like 5$

noglider 

That can be a good reason to like tires. Remember us when you have more cash to spare.

Stormy Archer

Oh, I'm pretty aware. I remembered you when I recommended tires to my girlfriend, now running 25c gp4000s. She had the 65$ to spare on Amazon B stock.

What's the research on wider tires for lighter people anyway? I thought I read the situation was a bit different for those of us small people under 130 pounds...

noglider 

I don't know of research findings, but my finding, with a sample size of only one person, is that it's less of an issue. My wife is 110 pounds or so. I've made several tire changes on her bikes, and she only noticed one, when she went from heavy knobby MTB tires to smooth MTB tires. She doesn't ride the MTB any more, only road bikes, and heavy, light, narrow, wide, high pressure, low pressure, she doesn't notice.

RiddleOfSteel

That's how I ended up with a bevy of Vittoria Open Corsas (ok, $10 a pop, but still...)! 23 and 25mm only for those things. They are great tires!

gugie 

[QUOTE=Kontact;20437772**
It isn't a swing arm, but that's the allusion I used to someone who's post suggested they think a rigid fork moves linearly like a shock fork. The reality is as you describe, and there's no reason to think that the crown is going to get crowded by a bending moment along the blades.

What part of your fender gets rubbed?[/QUOTE]

You wrote:
" The fork doesn't get shorter, it changes angle. It is a swing arm. Why would the crown get closer?"

On a standard, classic fork that draws down to a smaller diameter and curves somewhere below halfway down the fork, almost all of the flex is down where it curves - the raked curve "curls up" and reduces the radius when force is applied - such as when you hit a pothole.

My commuter fender rubs (drum roll please) right under the fork crown when I hit a pothole. The fork crown definitely got closer to the dropout.

The fork doesn't pivot at the fork crown like a swing arm. Well, maybe it may seem like it to some, but that's just an allusion.

The head tube angle does steepen temporarily when I hit that pothole (see Matchak article I linked to above).

Kontact

So when 63rickert said that the 9mm of suspension would mean the tire would move 9mm closer to the crown, you agree with that? Because that's what I was trying to dispel.

gugie 

You're just in an arguementative mood now, aren't you? I didn't read nor comment on that post.

I have actually measured the amount of fork crown clearance lost when you add offset to a fork, but it's specific to my Babe Ruth of Fork Rerakers. I think it's probably in the ballpark of what most forks do elastically. I've done enough of them, and taken enough data to be pretty confident of this.

For every mm of rake change, there's a corresponding 0.17mm of fork clearance change. That's nowhere near 1:1, very close to 1:6. When one is considering going low trail, fat tires, and fenders, and wants to modify a vintage bike to do so, you have to keep all of this in consideration. I typically want to have around 20mm of vertical fender clearance when I'm done. Add ~3mm for fender thickness (including hem), I really need at least 23. Knowing the current rake of a fork, and what I want it to end up with, I can easily calculate how much more clearance I need before I rerake to end up with the clearance I want.

So, to conclude, yeah, wider tires are better, mostly.

Cyclist0108

There are posts where he isn't?

Kontact

Excuse me? Didn't I already agree with you when I said "the reality is as you describe"? Yet it sounds like that didn't satisfy you and you need to make sure you're right by arguing about it.

So: you are right. I just never disagreed with you when I made the basic point that forks absorb shock by changing angle rather than getting shorter. They do both, but as you illustrated so nicely, they mainly change angle.

Summary: If your fork absorbs a 9mm bump, the tire might get 1.53mm closer to the crown, but the top of the wheel actually moves up 9mm relative to the frame.

Kontact

Awwww, does someone have some hurt feelings they want to talk about? Consider this a hug.

gugie 

User Control Panel > Edit Ignore List > Add a Member to Your List...

Kontact

Great idea. Done for two people that can't talk about bike junk without getting upset.