|Metal Fatigue and Big Riders|
|Fatigue failure is failure that occurs after repeated cycles of stress, but at a stress that is less than that which would be required for the failure to occur with a single application. Cyclic loading is the key idea here; and we get plenty of that as we ride. The number of cycles to failure by fatigue decreases as the load is increased. This is where the big rider comes in – the rider we at Zinn Cycles specialize in building bikes for. However, metals can also fail at rather low stresses given many repeated cycles of stress. All metals other than aluminum have a “fatigue limit,” which is the stress below which failure will never occur. With aluminum, failure can occur even at very low stresses, given enough stress applications.|
|Big riders are often very familiar with wearing out and breaking bike equipment. You go through tires much faster than lighter riders, your rear rim develops cracks at the spoke holes, and maybe you’ve broken spokes, chains, hub flanges, seatposts, saddle rails, saddle shells, crank arms, and even frames. To avoid breakage in use, big riders need to replace their weight-bearing bike parts more frequently than would a smaller rider.|
|Many big riders who go to bike fitters come away set up with longer pedal spindles to properly align the knees over the feet to account for wider pelvic structure, and the recommended saddle will often be wide as well. The stem will tend to be long and the handlebars wide, too. These adaptations “to make the bike look like the rider,” as fit guru Andy Pruitt, director of the Boulder Center for Sports Medicine, often says, can significantly improve the rider’s comfort and efficiency. However, there is a fatigue cost.|
|The use of longer and wider parts results in higher loads for a bigger rider because they are cantilevered out further from their mounting points; this causes a higher rate of fatigue failure on those parts. A seatpost for a big and tall rider may be extended twice as far out of the frame and get twice as much weight put on it as a small rider’s seatpost, and it will consequently be subject to a higher rate of fatigue failure. One rarely hears of a small rider breaking a seatpost, but many big riders have had it happen to them. The breakage may be attributed to hitting a bump, but that may simply be the straw that broke the camel’s back; the cumulative stresses on the seatpost made it vulnerable so that the single, sharp impact snapped it off. Perhaps the seatpost would have passed a standardized lab fatigue test, but the loads applied and the amount of seatpost extension used in the lab test may be far less than the big rider might apply in use.|
|Similarly, a big, strong rider pushing on pedals with extra-long spindles screwed into long crankarms will be subjecting those cranks, as well as the spindles, to an extra high rate of fatigue failure. Consequently, the big rider should replace his cranks (and spindles) more frequently than a small rider would. This is the reason we allow our customers to upgrade their cranks at half price. Similarly, we offer a 10% discount to our bike customers on any weight-bearing part they replace on their bikes.|
|Bike riding is too much fun to have your ride ruined by suddenly breaking a part that has your full weight on it. Big riders particularly would do well to recognize that metal bike parts do not last forever. They have a lifespan, and there is wisdom in replacing them before they break. I have seen a number of owner’s manuals for aluminum stems and handlebars that recommend replacement after three years of use. I think that’s a good guideline for aluminum weight-bearing parts under big riders. For instance, I personally replace my aluminum handlebars after two years of use. Even with ideal maintenance, all components will eventually reach the end of their serviceable life, the length of which depends on conditions and intensity of use.|
“As soon as the sun came out and the snow started turning to mud I knew I could do well in Frisco. The slicker the better for me, because it’s all about trusting your equipment and letting your bike take you for a ride. The brilliant golden of turning aspens with the fresh snow could not have been a more idyllic setting to suffer and feel the cold air freeze your lungs and fingers.” Emily Zinn
Have done a couple of long rides recently on my old BZ (Before Zinn) bike. Was an interesting excercise.
In short – I hated it – and it re-affirmed my love affair with my Zinn Dolomite Ti with it’s 210mm proportional length cranks. I used to absolutely love my old road bike – but my Zinn has spoiled me.
So – I’ve done a couple of 100km+ rides. The old road bike has 175mm cranks – and I figured I’d be fine with that as I’ve been doing a bit of riding on my Hase Pino Tandem that also has 175mm cranks. But I wasn’t fine. On the road bike I was on a reasonably quick group ride with some fit riders, and on the tandem (which is a heavy big beast of a thing) I’m tootling around with my kids. Nothing remotely like the same thing.
The thing I found was that I was back to struggling…
Both rides were reasonably flat – and I could hang with the group on the flat without much problem – but what hills there were – I was out the back immediately. On the Zinn – I can keep up on with the weight weenies on rolling hills (longer hills is a different story). But the rolling hills, and even small rises that the Zinn’s proportiional length cranks flattened for me – I could feel again. And the surges and accellerations that you get in a group of road riders – I was struggling with again. I remember when I first got my Zinn – that one of the biggest revelations was when I was racing – and how the accellerations that used to spit me out, became manageable. And that was immediate. The week after my first race on the Zinn – I jumped up a race group – and the following week – up another group. So here I was back on shorter cranks and immediately stuggling again with accellerations. And these things add up over a 100km ride.
So absolutely – without any doubt whatsoever – there is no going back for me! I will be back on my Zinn with relief and reaffirmed respect for what it enables me to do.
I’ve got a bike in my garage that illustrates the proportional length crank philosophy that is one of the cornerstones of the design philosophy of Zinn Cycles. It’s not a Zinn bike – but even so – it’s still pretty cool…
It’s fairly new and very specialised in that it’s a tandem that my wife and I ride with our special needs son Ted…
The bike is a Hase Pino tandem where the pilot is at the rear and the stoker is on the front in a recumbent position. And Ted isn’t tall enough yet to reach the pedals on the adjustable boom at the front – so he uses “Kiddie cranks” that are temporary.
As you can see from the photo the kiddie cranks interrupt the regular chain line and are clamped in place. So there are 2 sets of cranks of the front – eventually he’ll use the longer cranks on the front (which are on a sliding boom) but for now he uses the much shorter kiddie cranks. Proportional length cranks on display! Short cranks while you’re short – and longer cranks when you are taller. Makes perfect sense. Only problem being – that for the vast majority of bikes – it’s only proportional up to adulthood – when the range of crank lengths becomes very small – yet the difference in size of adults is vast…
Here’s Ted and I and the whole bike (so you can make sense of the above photo)…
So what else have I been up to?
Well – Ted and I rode the tandem in a 6 hr relay – so I’ve been doing a bit of riding on the tandem – but still on my Zinn at every opportunity. It’s interesting going between the tandem and the Zinn – going from 175mm cranks to 210mm cranks. You immediately notice the difference when gettting on the Zinn – but within a few hundred meters it the noticeablity goes away and it you are back into the world of comfort and increased ability. When riding the tandem – the noticeabilty doesn’t go away – and as it’s a big heavy bike (and because Ted isn’t able to contribute much) I’m constantly wishing it had longer cranks – especially when we get to a hill..
I did get a lesson in “being prepared” the other morning. I set off on a ride to work – with 2 mates. Early start – riding in the dark – and as it was so early – I decided to skip breakfast. Mistake! The guys I was with were faster than me – so that put me under a bit of pressure (which is normally fine – and benificial). But when we got to a good sized hill about 10km into the ride – I started feeling dizzy and struggled big time. Halfway up I decided that I’d had enough and said my farewells to my companions and rode home again. Combination of late night and no food I think was the problem. Completely underprepared!
Other than that – I’m still riding – not as often as I’d like in the last couple of weeks – but still riding.
If you’ve ever done squats in the weights room – you’ll know that you can cheat by not squatting all the way. You can seemingly lift more weight – but it’s a false economy as you don’t get the full strength gains that a deep squat can give.
So what’s this got to do with cycling? Well for me it’s the difference between 175mm cranks and the 210mm cranks that are proportional to my size on my Zinn. I’ve been adding a few interval sessions to my training lately – and one in particular is seated big gear climbs… Where I find a gentle (ish) climb and put it in the big chain ring and climb with a low cadence. It’s very much like doing weights on the bike. Certainly makes you strong. But also – it’s something where I feel I can make even better gains because of the long cranks on my bike. Full range of motion can only help strength development. The long levers of the Zinn custom cranks enable me to really develop the advantage I already have with the long levers of my body. Means I can really get into the nooks and crannies of strength development – so to speak…
So what else have I been doing?
Well – we’ve had an awesome summer down here in New Zealand. So, just as things are starting to cool down, I pick that as the time to ramp up my training. Seems like I’m doing things backwards…
But – though it’s nice to go for a ride on a beautiful day – there is some perverse satisfaction to be had from gutsing it out into a stiff breeze in the dark on a long commute home.
I’m slowly but surely picking up my training volume. I’m very mindful of the fact that when I last did a long lead in to an event I was training for – that I had a hiccup – in that I trained like a demon to start with and was making fantastic progress – only to be stopped in my tracks with a mystery illness that put a major dent in my training. Whether or not that was caused by the training I was doing is hard to know – but I’m taking a bit more of a measured approach this time.
I’m adding volume by adding midweek rides. I work 50km from home so I’m adding 1 or 2 one way trips (in the dark) to my schedule as work allows. And I’m increasing the distance of my Sunday rides (that are normally done with a group) – pushing that out to 80 to 100km. And I’ve started adding a few of those interval sessions.
Intervals are something I really enjoy – in a twisted sort of way. Sure they hurt and you want to puke sometimes – but I love them. I guess it’s some sort of learned hardship that I picked up from my rugby playing days – where we did a lot of interval training. I know that my body seems to respond well to intervals –so they are something that will always be a part of my regime…
But they hurt bad when you haven’t done them for a while – and when your aerobic base isn’t what it was :)
So anyway – I’m increasing volume – and slowly introducing some interval work. There is a Winter Series of races coming up in 6 weeks or so – so I’ll be targeting that as my first hit out with some intensity. And will be racing as often as I can from then on in…
205 days till my first major goal which is the Taupo Cycle Challenge – so – steady as she goes….
This year – as a Team Zinn member – I’m going to regularly post short blogs about me and my Dolomite Ti’s advances towards my goals for this year.
I’ve been in a bit of a holding pattern – still riding regurlarly – but only enough really to keep a level of fitness up. Work and Family have been a priority for the last year – so as needs must – cycling has taken a back seat.
But with things settling down to manageble levels at work – I’ve decided to set some goals and really get into it again… (Family is still the biggest priority – but they will benifit from a fit Husband and Dad – so all good there).
So – I’ve set a couple of goals this year…
- A 4 hours 30 something ride at the 160km Taupo Cycle Challenge – in November.
- A 40km TT in under an hour – before the year is out.
These are lofty goals. Both of them will be new personal bests.
I’m starting from a position of reasonable – but not spectacular – fitness. And a bodywieght that’s about 10-15kg too much too much to achieve my goal at Taupo – which has a lot of hills in the first 80km and a biggish one at the 120km mark. So I have a lot of work to do. We are heading into Autumn down here in New Zealand – so I’ll be riding and training through our winter – so I can acheive these goals in our spring.
Along the way – I will race in road races and TT’s as much as I can fit in – and generally get involved as much as time allows in the local cycling scene here in Kapiti, New Zealand.
And it’ll all be on my beautiful custom Zinn Dolomite Ti bike – that I’m as excited about riding as the day I got it a few years back.
This is a photo of me racing a few weeks back (one of the only races I entered this summer) – I doctored the photo via snapseed as it helps to hide the weight :) I’d been dropped when this photo was taken and in a world of hurt. Good reminder that I need to work harder.
I’ll try to post a blog a couple of times a month about how I’m doing – or just cycling in general on my Zinn…
Boulder, CO, USA – February 21, 2013 – Lennard Zinn has updated his best-selling book Zinn & the Art of Road Bike Maintenance, the world’s most helpful and comprehensive guide to bicycle repair and maintenance. From basic repairs like how to fix a flat tire to advanced overhauls of drivetrains and brakes, Zinn’s clearly illustrated guide makes every bicycle repair and maintenance job easy for everyone. Zinn & the Art of Road Bike Maintenance, 4th Ed. is now available in bookstores, bike shops, and online. To preview the book and see what’s new, visit http://www.velopress.com.
* Basics: How to fix a flat tire, lube a bicycle chain, adjust the brakes
* Emergency repairs: How to fix a broken chain, tighten loose spokes, repair a bent derailleur
* Easy shifting: How to clean, lube, and adjust shifters and cables for smooth shifting
* Wheels: How to install a new tire, change a cassette, true a wheel, replace broken spokes, build your own wheels
* Overhaul: How to repair pedals, chains and chainrings, saddles, handlebars, stems, headsets, forks
* New tech: How to maintain 11-speed systems, electronic shifters, disc brakes, new bottom bracket formats
* Cyclocross: How to set up a ‘cross bike for racing, select the right components, and make quick repairs
* Troubleshooting: How to figure out what’s wrong with any bike and fix it