Words: Seb StottSometimes the best solutions are the simplest.I've already complained that some of the
latest innovations cooked up by the bike industry could add more complexity than they’re worth. But it’s not all bad news. There are also some good ideas out there that make bikes both simpler and better.
In contrast to overly complicated suspension designs or added electronics, sometimes good design is about asking what you
don’t need. At its best, simplicity means making a bike lighter, quieter, cheaper, easier to maintain and more reliable. And it’s more than that. There’s something elegant and ingenious about a simpler solution that performs just as well.
Here are a few examples of where less is more.
1. Flex pivotsThere’s a reason virtually every XC bike now has a “flex pivot” instead of a conventional pivot with bearings or bushings. Flex pivots are lighter, they eliminate a number of small parts (bearings, bolts, washers…) and maintenance.
While bearings have to be replaced about once every season, a well-designed flex pivot will last the lifetime of the frame. The pivot at the rear of the frame, whether on the seatstay or chainstay, usually only sees a few degrees of rotation through the suspension’s travel. That means bearings can become pitted and wear out faster because the force is always acting on the same point, whereas a flexible frame member made from carbon,
steel, or even
aluminum can accommodate that range of motion without fatiguing. They’re most often seen on bikes with 120mm travel or less right now, but
Merida just launched a 170 mm flex pivot bike and I suspect we’ll see more long-travel versions pop up as manufacturing techniques improve.
2. Single-ring drivetrains for allTo keen mountain bikers, the benefits of one-by may be so obvious that it almost goes without saying. They have allowed us to do away with a front shifter, front derailleur, cable, and (usually) a chain guide too, while still providing a wide range of gears. But to a novice rider, the simplicity of the single shifter is even more beneficial. They’re not just simpler to install and maintain, they’re simpler to ride because you only have one shifter and a continuous spread of sequential gears to think about.
And although they’re not exactly new, you can now buy an entry-level bike with a decent single-ring drivetrain. For those who are just getting started in the sport, that’s a very good thing.
3. Single pivot suspension (done well)I’m sure that defending single pivots is going to draw a lot of flak, but here we go. Two criticisms are levelled at single pivot bikes. The first has to do with braking and applies to linkage-driven single-pivot bikes (like you'd find on a Kona or Commencal) as well as true single pivots (as used by Orange and Starling).
The main reason to use a Horst-link layout (which is the most common design these days) over a linkage-driven single pivot is to reduce and tweak the anti-rise characteristic, which is how the brake force acts on the suspension. This is claimed to allow the suspension to move more freely over bumps while braking. But in reality, this just isn’t much of an issue. In fact, high anti-rise values typical of single pivots help them to resist brake dive, making them more stable under braking, and I think this effect is far more noticeable. For what it’s worth, a lot of World Cup and EWS races have been won on linkage-driven single-pivot bikes over the years, from the likes of Commencal, Kona, Nukeproof, Cannondale, Honda and Saracen.
The second criticism only applies to true single-pivot bikes, where the shock is mounted directly to the swingarm. They generally lack progression from the frame, which means any progression or ‘ramp up’ in the suspension forces has to come from the shock. And with a progressive linkage, the damping forces also increase toward the end of the travel, further helping to prevent bottom-out.
First off it’s worth pointing out that some multi-pivot designs, such as Specialized’s
Stumpjumper Evo, don't offer more progression (drop in leverage ratio) than could be achieved with a single pivot.
Besides, air shocks make tuning the progression of the spring with volume spacers easy, while the latest air springs with added negative volume or progressive coil springs mean modern shocks suit a linear leverage curve much better than they used to, diminishing the benefit of a progressive linkage.
Sure, with a progressive linkage the damping forces increase throughout the travel as well as the spring rate, and this is harder to replicate with the shock. But not everyone agrees the travel-dependant damping rates which come with progressive linkages are a good thing. That’s why
Cannondale built a downhill bike with a progressive link to drive the (coil) spring and a linear one to drive the damper.
Despite all this, I do think that progressive linkages have advantages from a performance standpoint, at least with many of the shocks that are available today. But with the right shock, single pivots can work very well indeed. Where I live, I know people who swap frame bearings multiple times a year; for them, the benefits of a single pivot could greatly outstrip the downsides.
4. More travelThere are a lot of complicated ways of trying to optimize suspension performance: fancy linkages, expensive shocks, idlers. But there’s only one surefire way to help a bike smooth out the bumps: give it more suspension travel.
Increasing travel doesn’t necessarily increase weight, cost or complexity, but it fundamentally changes how effectively the bike can absorb impacts. And while not everybody wants a well-cushioned ride, you can run a long-travel bike as firm as you like by running less sag, using a lockout or adding volume spacers, but you can’t run a short-travel bike as soft as you like, or it will bottom out.
I’m not saying that everybody should ride a downhill bike, but giving a trail bike 10mm more travel might be a simpler and more effective way of improving tracking, grip and comfort than a more complicated suspension design.
5. Big rotorsSimilarly, there are a lot of complicated ways of improving braking performance like two-piece rotors, finned brake pads and lever cams. Most of these add cost, and sometimes issues too. Finned pads often rattle, and lever cams amplify inconsistency or sponginess in the hydraulic system.
In contrast, bigger rotors improve power, cooling and consistency without adding complexity. A 220mm rotor will boost power by about 10 percent when compared to a 200mm rotor, while also providing more surface area to dissipate heat. Sure, they weigh more, but the disc is only about 25 grams heavier in the case of SRAM’s HS2 rotors, and the extra weight is a positive for absorbing heat during heavy braking. To make things even simpler, you could try 220mm rotors with two-pot brakes instead of 200 mm rotors with four-pots; two-piston brakes are easier to maintain, and the weight and power should be comparable.
What’s the bottom line?I don’t want to come across as a Luddite. I like technology that makes bikes perform better, even by only a small amount. I’m a big fan of innovations like long-travel dropper posts, 12-speed cassettes and adjustable geometry because they offer a tangible benefit, at least sometimes. But in the cases where a design with fewer parts performs just as well in the real world, I’d rather take the simpler approach every time. Remember that bike brands want to stand out from the crowd and convince you their bike has an edge over its rivals. It's much easier to do that by asking what they can add than what they could take away.
On a road bikes they say its more aero and so on. but on a mtb to my understanding aero isnt such a big deal anyways. Full external cable routing is in fact very easy to work with.
Only looks… which is subjective anyway. External cables look cool imo
Steel single speed, no brakes
Then we go back to classic outer routing because holes in a frame look bad.
How often do you swap shifter hose, 1-2 times per year?
I do not understand internal routing hate, since in modern frames tube in tube solutions allow you to do these things easily for home mechanics;
Also why nobody complains about dropper routing in that case?
Most internal routing for decent nowadays for normal frame mounting. However, if you have to cut the rear brake line it's a pain. Headset routing, not a single MTB rider can justify this..... Just a headset spacer adjustment or stem change requires cutting/removing the brake lines, rear derr, and dropper if not AXS. It's senseless sh*t on anything but TT bikes (maybe Road bikes).
1. It looks better, I care about how mechanical objects look and am prepared to sacrifice a little convenience for a clean aesthetic.
2. External cables/hoses attract mud and the mud trapped between the frame and the cable rubs through the paint and make the bike harder to clean.
3. External cables promote the use of single use zip ties which equal more plastic waste. I've also had these zip ties break on trail more than once.
4. When you install a brake you have to shorten the hose anyway, just stick a threaded plug in the line when routing and you can usually get away with a lever bleed or no bleed at all.
5. Internal hoses and lines are protected from trail debris, bike racks and shuttle pads.
Our shop carries Trek, Santa Cruz, Ibis, Cannondale, and Evil. I can route a shifter or derailleur cable on any bike from any of those brands quicker than any external guide.
also it looks much nicer
The holes in the frame/steerer tube are so big that people blast the crud inside the frame/headset which obviously leads to a sequel of the Titanic...
If you have to ever change any cable on a Scott Parton you will probably retract your last paragraph as well. Absolute toilet...
When you ride in a lot of filth you don't just replace the cable, the outer goes too.
Rather than deal with that for the third time I just went AXS instead. No worries any more
1. External cable routing only
2. Threaded BB shells only
3. From for large water bottle only
4. Think carbon fiber is the best thing to ever happen to mountain bike frames
5. Think stupid puns are funny and worth repeating over and over ad infinitum
Avoid Scott bikes, problem solved!
My only exception at this point is my BMC roadbike. When the time comes it will be an immense pain in the ass but that bike doesn't see the conditions the mountain bike does and it looks really nice. I view the mountain bikes as fun, utilitarian rough-housers that need therapy regularly, whereas the road bike has more vanity tied up in it. But that's just me.
When you get to the right time in life you only go for a prostrate exam once a year. But no one likes going. Likewise, 99% of brake swaps are much more enjoyable if it's bolt off/bolt on. The design of some frames internal routing makes me want to go for a prostate exam.
The reason nobody bitches about internally routed droppers is that once your properly install the dropper cable housing your good, and you can swap posts without replacing the housing.
Every time you need to faff with brakes it’s a re-bleed. I just put Hayes dominions on a stumpjumper and the Hayes lines are thicker than most, it ended up dislodging the vinyl tube inside the frame which led to complete frame disassemble to put a new internal routing vinyl tube in.
So dumb!
I will accept arguments for external brake lines however, if you swap brakes often it is faster. But on my personal bike I’m happy to take an extra 5 min to bleed it for it to be hidden.
Also, zip ties are ugly, I’m thoroughly convinced of that.
The reverb hate on pb is silly. Theyre actually one of the best posts out there. You just have to service them... People never do, and then they cry about it when the post fails after 7 years of abuse. Classic modern culture...
This happens every time mtb "gets popular". Loads of stupid ideas start circulating the market and everything goes to shit.
On hydros now, but loved my BB7’s!! Strong as heck.
Just look at the comments for EVERY bike review on PinkBike. And own the MTB culture's ridiculous obsession with design over engineering. If headsest routed cables hadn't been developed for road aero, the MTB community still would've made them happen.
Shimano have made that great Deore 10sp and 11sp stuff, but I guess bike companies feel consumers see "12 speed" as a must-have bullet point.
11-50t for HG driver
10-50t for XD driver
I built up a SJ Evo with this 11sp XD so that if I needed to, I could swap in my old 27.5 wheel still running the 11sp HG cassette.
They have good range, pretty light, and can be found a little cheaper on other sites
www.bike24.com/brands/garbaruk
If you have special needs chances are you need a special setup.
Less is more!!
I'm taking that approach with my next MTB build myself.
For shifter/dropper... less cables is better.
That being said, Starling's bikes have a very flat progression curve, and on some sizes/models a falling curve, or rising leverage rate. This is bad haha. If Starling moved the main pivot forward a bit, it would be easier to get some rise. On their frames, without really changing much else, they could reach about 4% progression, which is much better than falling, or negative progression. Too bad the industry has everyone so scared of chain growth and rising antisquat that Joe will never do this.
THAT BEING SAID again, the worst thing you could do to your frames suspension performance is give it negative progression, and even with that the Starling bikes ride amazing, and like you said, good for 95% of riding. It just goes to show you, I don't think complex, multi-link suspension designs are worth the trouble.
On a side note, all my singlepivots killed shocks. Not exactly science but i feel a perfect singlepivot also needs a ball joint shock.
www.pinkbike.com/news/gt-downhill-bike-prototype-fury-nz-national.html
But I prefaced my comment with "or weirdo frame", and I'd consider a split seat tube on a bike with 160mm of travel or less "weird" because it would be hard to run a dropper.
There was a time when i was convinced i could do a very good singlepivot -i even bullied Joe to do a starling with a different shock placement to make it slightly progressive ( @Vinnijussi is my son). The thing was still fairly easy to bottomout.
For me linkages are still the way.
Can you be more specific/detailed in "fairly easy to bottom out"? What shock was it? I know its tough for me to criticize Starling bikes because they ride so well, but something else I'd like to change is the Murmur's 2.54 leverage ratio. Its not high, but I'd like it to be even lower, at least 2.4 to get better damping performance from whatever shock is being run.
The shock it worked best with was the RS vivid coil tune MM with a fair amount of compression. After the shock died I got an inline (which also died) and the simple Fox coil which kept bottoming even at 15 % sag. As long as you dont do bigger hits the starling is great, It tracks way better than anything else. At 25% sag it bottomed on 2.5 -3 foot flat drops or a similar force, which basically occurs 2-3 times a ride around here. What i did not like was how it kept me from doing bigger stuff, I knew I need some backup for. (And cranks hit the frame while sprinting, i tried to dono it to my son but even at his lower weight he kept hitting the frame, more modern starlings do not have this problem anymore I believe).
It would be interesting if you could do a more modern version of the GG DH for enduro:
-Mount the shock lower for less leverage ratio and a sufficient dropperclearance
-Keep the very long shock to improve progression ( I found out that this is way easier to do with a long shock)
Or get a full moxie ( low leverage ratio, droppercompatible, good progression, probably great quality as the moxie is the best made frame i have ever owned.
www.pinkbike.com/photo/23584548
It has a 2.4 leverage ratio, and about 5% completely linear progression. With air shocks you just stuff the can with volume spacers and its fine. I never bottomed. I've also run an Inline Coil, with a progressive coil, and that keeps the bottomout soft too, but to make it poppy and feel good on machined trails & jump lines I have to run more compression than I'd like for the rough, natural trails. Rather than having to adjust my compression for every type of trail, I put an EXT on there (not pictured) and its the best of both worlds. It doesn't bottom harshly, it has "pop" for machined runs, and still has that ultimate traction for natural, rugged trails.
I only ran a cane creek inline air for half a season, and had no issues, but I've run the inline coil for an entire season and also had 0 issues (only a half season on the EXT so far). My design is slightly less flexy than a steel Starling, and uses a lower leverage ratio, so I doubt my frame will blow up shocks faster than anyone else. With a good shock, 5% progression is fine. I rarely bottom, and never harshly, at about 30% sag.
Its not the best angle to see in that photo, but the main pivot is very far forward- its further forward than the front of a 32t chainring. This allows a single pivot to get more progression, but it increases the pedal kickback as you go deeper into your travel. Most designs try and reduce pedal kickback as you go deeper, but I think this is misguided (so does specialized- look at their Enduro and Demo). I could rant on and on about this subject but this comment is already too long haha.
Although Seb is correct in saying they will last the life of the frame! Haha
Fatigue is actually one of those funny spaces in engineering where we have a poor analytical model for it, but plenty of empirical evidence so we can design for it reasonably well.
I have nothing against flex pivots for carbon or even steel bikes, but it doesn’t make any sense for aluminum frames. I’ve seen a few Kona Hei Hei break at this “flex” point.
I'm just interested to see what sort of lifespan carbon flexures have on bike frames, that's all. It's sort of a new thing.
The point of my comments here are just to point out flex stays follow the same S-N fatigue curves (and Stress-Strain curves) that the rest of the frame follows. The internal stresses that you see clearly with a flex-stay also happen at the head tube, near the bottom bracket, all over the frame but are less obvious. Sure, a flex stay is probably a more difficult feat of engineering than a normal bike frame, but they're not particularly new nor novel from a structural engineering standpoint.
Don't worry.....
From a performance perspective though, yeah it can definitely shine there
It's obviously a bit different of an application compared to an enduro bike or even a modern trail bike, but flex stays aren't new.
Every day Alicia is able to remember a little bit more and do a bit more therapy. Progress is slow but it is happening!
The lack of frame progression is an absolute non-issue IMO, even with coil shocks. But the loss of grip under braking is a real thing. You can adapt to it, even make it work for you and have fun with it, but get back on a Horst link bike and it does get easier.
They're also bloody great bikes and nothing is more fun than an Orange
you forgot wheel size..........
A 220mm rotor will boost power by about 10 percent when compared to a 200mm rotor
As I understand it, braking force diminishes at the speed differential increases (ie the rotor moves faster over the past). This is compensated by the increase in leverage, but the relationship is complex.
A larger rotor can store and dissapate more heat than a smaller one, but not by as much as you'd expect, as the area increases in line with the circle circumference, not the circle area
I would still be riding it as a bike for mellower terrain if the cranks would not hit the frame while sprinting ( it was a very early version)
With the front derailleur you get a far greater gear range, lower lows and higher highs. Instantly move into climbing gear range with the front derailleur. You get a better chainline, less tension on the chain and noticeable less friction in the climbing gears.
The last two generations of Shimano’s XTR front derailleurs are the best front derailleurs of all time. Super snappy performance.
Don’t be fooled by sram’s marketing team because they couldn’t make a competing front derailleur. Front derailleurs rule!
Besides as a bigger guy, I’ll generally take the stiffness of a bigger travel fork even if it means an extra 100-200 grams.
Big rotors also just make total sense, too - in the auto racing world, rotor size is restricted by inner wheel diameter - until we get to a 660mm brake rotor - the mtb world doesn’t have that issue !!
Refreshing ot hear someone not pushing the narative of low Anti-Rise being a positive suspension caracteristic. Having spent 2 seasons on a bike with very low AR, I can't wait to ditch that frame and go back to a frame with high AR as it makes your life much more relaxed when riding steep stuff, at least when you're not a WC level athlete.
We are used to see the pivots rotating in the seat/chainstays but with a flexpivot that angular movement is spread across a good part of the length of the beam.
Some designs will have more elastic deformation from cornering than actually from cycling the suspension
That being said, two big caveats here are to remember the sheer scale of fatigue life (order of magnitude of 500 million high-stress cycles, for example) and also that carbon, even if it has no fatigue limit, still fatigues slower than aluminum. Engineering as a whole has a decent grip on how to design for fatigue life, using lots of empirical data (S-N plots) and the such.
So TL;DR yea, a properly engineered flex-stay frame is absolutely nothing to worry about, but not because carbon doesn't have a fatigue limit, its because of years of empirical research and good engineering practice.
Getting the correct carbon layup, mold design, and resin to allow a frame to flex and then hold up to every Jerry with a JRA warranty claim ain’t simple.
Single ring drivetrains only worked when we figured out wide range, cnc machines advanced to pump these out cheaper, and we got more frame makers on wider hub standards so these wide range/12sp drivetrains fit on frames.
Single pivot- see needs to pedal like an XC bike but descend like a downhill bike, but we want simple shocks without levers and electronics. I too, like also like to have my cake as well as eat it.
More travel- agreed here but then we need to negate single pivot argument
Bigger rotors- agreed here. But these are needed because we have more travel, better suspension, bigger wheels, more powerful brakes, more trials being built and greater access to them with vehicles to get us places, and the internet to tell us where they are.
We have it good when we don’t realize how complex the simple really is.
Let the idea that brake squat is a good thing die. It was wrong when PB first started pushing the idea, and its still wrong now.
I only disagree w/ #4 - I prefer less or moderate travel as in my experience it keeps handling overall more consistent and is compatible with my skill level (meaning that if I rode a 180mm bike, I might try a big feature and get seriously hurt).
but is there any evidence at all that floating rotors or 4-piston calipers are more problematic?
does anyone often hear people complaining about these items?
why floating?
"A floating rotor has the ability to conform to the brake pads giving maximum rotor to pad contact. This happens even when a relatively small amount of force is applied. Floating motorcycle brake rotors often lead to more consistent and predictable braking."
why 4-piston?
"With 4-piston calipers, you have one brake pad and two pistons on each side of the disc. The greater number of pistons results in a more powerful braking setup, since more force can be applied by the pistons on the pads"
Though, if a Toyota costs the same as an alternative offering better luxury, looks, and prestige, I can see why many may be compelled to go with the latter, especially for sporty recreational stuff.
I'm guessing the author is more interested in utilitarian aspects of bike ownership?
there are many advantages to having a higher number of smaller pistons in a caliper, rather than a a single big piston. The performance of a brake comes down to many factors, and raw mechanical force at the piston is the least important.
smaller pistons are more stable in their bore, and suffer less binding due to manufacture tolerances. they do have a tendency to get sticky faster than a bigger piston due to build up as the bore surface is larger in relative to the piston size.
smaller pistons can travel further with a given amount of fluid movement, giving you better retraction and reducing rubbing.
smaller pistons do allow a bigger pad(as you mentioned), but the real benefit is that the pressure is applied much more evenly across the pad, thus giving you a more consistent force and ability to control lock up.
A higher number of smaller pistons is the main factor in alleviating the main cause of degridation of braking perfromance.....heat transfer to the brake fluid. Finned pads, ceramic pistons, floating rotors, finned rotors, etc etc etc.....all a secondary way to keep the fluid cool. More smaller pistons is the primary method. Just go look at car racing. You won't see any giant 2 piston calipers on a modern race car. 6 piston or even 8 is what you will find.
Therefore: 10% more radius means 10% more power. Yay physics 101.
Put it this way, you've probably never been in a car with brakes that were too powerful, but you may have noticed when you were in one where the brakes weren't powerful enough. Sure you can stomp on them and skid the tires, but you probably got tired of wearing out your foot pushing super hard all the time just to come to a stop.
Small pistons are more stable in their bore, whether this has any measurable effect on performance is debateable
Small pistons dont travel any further unless their overall surface area is smaller. 2 small pistons vs 1 big piston, they will move exactly the same distance if the surface area of the 2 small ones = 1 big one.
Hot fluid is not the main performance degrader on pushbikes, it's hot pads. Although more often than not, its actually bent rotors,
That makes your "extra travel is no big deal" item much more palatable while improving suspension performance since they don't have to tune kinematics with much climbing in mind.
To link those functions makes perfect sense. And this isn’t the first time I’ve heard the suggestion- but the way you put it made me think - you could pull it off with a crazy cable arrangement bolted to your saddle rails and lockout lever. Would be fun to try out.
IMO, a 3 pos. remote lockout sounds pretty good solution, not too complicated.
aside; I'm surprised enduro folks don't use remote lock out with all the sprinting they do.
- Amount of time and money spent on sealant: zero and zero
- Amount of time and money spent on inserts: zero and zero
- Amount of sealant leaks: zero
- Number of times I have re-applied rim tape: zero
- Amount of Youtube videos watched on how to seat a tubeless tire: zero
- Favorite tubeless valve nipple: the one attached to the $5 tube I bought a couple years ago
- Number of trailside tube replacements in the last 4 years: 2
I understand the theoretical benefits of going tubeless, and I know some terrain & riding styles will destroy inner tubes, but for me the simple inner tube has been working out pretty well!
-Amount of money spent on tubes and patches: Zero and Zero (well, OK, I do carry a tube I bought back in 2018 or something)
-Amount of time and money spent trueing bent rims from running no insert: Zero and Zero
-Number of times I have reapplied rim tape: Zero in 5 years over 3 bikes
-Number of trail side tubeless repairs where I inserted a tube:1
-Weight saved in front wheel running no insert and tubeless: half a pound
-Amount of evaporation of sealant if you use QuadBoss ATV sealant: none
-Traction gained from running 2-3psi less than with tubes: a metric $hit ton
To each their own, and I run tubes on my road and commuter, as it makes sense weightwise, but tubeless is going to be the way going forward in most situations offroad.
Zero percent of people agree with this, it’s really remarkable.
Even if tubeless didn’t have any performance benefits (it has tremendous performance benefits) the lack of flats would be worth the effort. I get a flat a year now…used to be one a month, and more during the summer.
Wow.
Dude! You’re pro tube! I love it!
I remember when was a couple years into tubeless, riding that enchilada with a couple of old friends…they were still on tubes, probably when 90% of riders were still to convert…those dingdongs changed like six flats between them that day, and it was glorious to watch. I knew then that whatever struggles I had installing my tubeless stuff at home was nothing compared to one, two, infinite tube changes in the Utah sun. Especially with an audience.
Truly takes all kinds…
Post your venmo so I can send you five bucks, I must show my support with more than words. What’s a tube cost in 2022?
-No rear suspension
-Universal hanger
-External cable routing
-Whatever headset type that you can pop in/out by hand. (I can't remember)
-Plenty of clearance around tyre/crank to clean away mud.
The linkage driven singlepivot never felt like an issue to me and I've been riding specialized and Santa Cruz for years because I was "scared" of the soooooo "bad" singlepivot designs
Bike is dead silent.
Next up for me is probably the a bike featured in this article... starling.
There's something to be said for setting suspension to work for an individual and their own level of riding.
FWIW I do tend to use the same spring rate across different travel bikes though.
I don't think that's true. I'm not a materials engineer but my engineer friends tell me that all materials - aluminum with its "micro fractures" or whatever and carbon as well - absolutely do wear out over time. If this were not true, you would never need to perform maintenance or replacement on aircraft wings and bodies.
Furthermore, I've broken 2 frames and know many people in the local community that have as well. It's not uncommon. I find it really hard to believe that a flex stay doesn't break faster than a non-flex part. It's intentionally thinner and enduring more elastic deformation than it otherwise would, and that simply has to wear it down faster than a comparable, conventional design.
Ummm. So flex pivot lasts until it cracks and frame is dead?
Everything is a compromise, some people are happy to live with the compromises a steel bike makes for the way it rides.
I'm with you on ti frames though.
If you want a more scientific approach look here: en.wikipedia.org/wiki/Fatigue_limit
Aluminum will start to fatigue the moment it gets used no matter how low the stress, steel and Ti have thresholds where a certain level of stress has no effect on the alloy. Meaning, on the road at least, most riding has no impact on the life of the frame.