Thursday, January 15, 2015

Multiple Wheelsets

We started tinkering with the idea of alternate wheelsets for bikes back during the 2006-08 period when everybody, I mean everybody, was converting skinny-tire 700C bikes to chubbier-tire 650B bikes with long-reach brakes. Of course, disc brakes don't require a brake swap, which makes it much easier to try different wheels on any given bike, as long as the hub and brake rotor dimensions match.

A few years ago, Mark here put some 700C disc wheels on his Surly Troll, which is a bike designed around 26" mountain bike wheels. Mention this on any bike forum, and you'll be met with "experts" who insist that changing wheel sizes will make handling too weird. But in reality, a 700x32 and a 26x2.4 have similar overall diameter, so handling is affected minimally. Since then, we've converted at least two 26" Disc Truckers to 650B and even 700C. Yes, things change about a bike when you change wheel sizes, but that's why we do it. Like all bike choices, there are trade-offs to swapping wheels. There are circumstances where one wheel size is just what you need, and the other would be less optimal. Then there are other circumstances where the reverse is true. Luckily, these decisions aren't permanent.

I have two wheel sets for my Ice Cream Truck. Here it is with a typical fat wheelset, Clown Shoe rims and Bud tires:
These fat tires are just the ticket for riding into an uncertain future.

And here is the same bike with 29+ wheels, Stan's NoTubes Hugo rims and 29x3" Knard tires:
It doesn't even look weird.
The 29" wheels and tires save about 5-6 pounds of rolling weight off the bike. They're fat enough to handle lots of varied terrain, but feel zippy compared to 26x4.8" wheels and tires. The overall wheel diameter is nearly identical with either wheel size. So I keep the fatties on in most winter conditions or when brush-busting, and I roll the "skinny" 29x3 rubber when I'd rather feel fast than have ultimate traction and flotation. It's like two bikes in one!

Here's another example - two Surly ECRs, one with the usual 29x3 tires on Rabbit Hole rims:

And the other with normal width 29"/700C rims and the amazing Compass 700x38 tires.

Again, the internet experts will insist that this is a bad idea. But listen to this: The wheelbase and bottom bracket drop on the ECR is nearly identical to that of a similar sized 700C Disc Trucker. Nobody would suggest that 700x38 isn't appropriate for a Disc Trucker. Not surprisingly, the handling of the skinny-tire ECR is reminiscent to that of a Disc Trucker, and it has all the braze-ons for rack touring... So here again, we have one bike with two wheelsets serving a wide variety of needs.

Wednesday, January 14, 2015

Surly $150 coupon: Best Deal of 2015

Have you been thinking about a fat bike, but waiting for a deal? Or have you been planning to set up a new commuting or touring bike this Spring? Well, this is the best deal you're likely to get. Here's how it works. You print off this coupon:
Then you bring it to your favorite Surly dealer, and you get whatever complete Surly bike you want for $150 less than retail. We will also sweeten the deal and give you 10% of the purchase price in store credit.

Here's an example. Let's say you want a Pugsley. MSRP on a Pugsley is $1750. Subtract $150 for the coupon, and you'll pay $1600 plus tax. But then you'll have 10% of that $1600 to spend at Hiawatha Cyclery. That means $160 in free bike stuff on this purchase or future purchases.

This coupon is good until April 1 or until the bike you want isn't in stock anymore.

Tuesday, January 6, 2015

Tuscobia ride, some thoughts about my training and diet

I attempted the Tuscobia 75 bike race last week. Short version: I had a great time, but my body was really only good for 45 miles on that trail, not 75. My Surly Ice Cream Truck performed flawlessly, but in the end, my lack of training and extra pounds on my body made it difficult for me to finish the entire distance. Here are a few images:
It started out pretty cold first thing in the morning before the race, but by the time I started rolling, it was into single digits above zero.

This was my first snack and water break, at around mile 10. The trail was plenty scenic.

The Tuscobia Trail looks a lot like this most of the time. When I could find bike tracks to follow, it was pretty easy and fast. Where snowmobiles had obliterated bike tracks, it was squishy and slower.

A few commenters asked about the results of my diet and training. I more or less followed the diet advice in Grant Petersen's book Eat Bacon Don't Jog, and I was successful at dropping about 15 pounds in a month. If you haven't read the book, you should, but the jist of it is that a person should eat mostly "good" fat calories, limited protein, and almost no carbohydrates of any kind. This method works wonders for me. Anyway, when the holidays hit, I quickly realized the true limitation of this approach - it's profoundly antisocial. When you eat this way exclusively, only a few fat-filled bites will keep you full and not thinking about food for several hours. You don't need many big meals, and you certainly don't feel like eating three squares a day. Unfortunately, our culture holds that eating large meals is an important family/social thing, especially around the holidays, and, for the most part, these meals offer few options for a person who lives on 80% fat calories, and they also tend to offer lots of desserts. So I fell off the wagon, mostly for social reasons, during the month of December. By the time of Tuscobia, I was down about 10 pounds from my peak weight. I had done little riding aside from my daily commute. So my weight loss and training was lackluster, and during the race, I just didn't have the muscle stamina to keep pushing through the snow after 6+ hours. One effect of being on the low-carbohydrate diet is that I didn't experience anything resembling bonking. Because I ate only low-glycemic food leading up to and during the race, my energy level seemed constant. I had to drop out because my muscles and joints were in pain, not because I was out of energy to keep moving.

Thursday, January 1, 2015

Closed Friday, Jan 2

Gonna go try something:

Back on Saturday!

Tuesday, December 23, 2014

Holiday hours

HC will be closed to the public Dec 24-25. We will be open Friday, Dec 26 at 3-6 pm, and Saturday, Dec 27 at Noon-2pm.

I'll get back to you about our schedule for the following week.

Happy holidays, etc. Hope you all get out for some bike adventures.

Wednesday, November 26, 2014

Thanksgiving hours and holiday special

HC will be closed for the Thanksgiving holiday weekend, Thursday, November 27 thru Monday, December 1. We will get back to normal hours on Tuesday, December 2. I am more than happy to take orders and answer questions during this time via email during this time. hiawathacyclery at gmail

Don't wait in line for hours like on Thanksgiving and Black Friday for deals. You can get all your deals here at HC. Buy any gift certificate between now and December 31, and I'll add 15% to it. For example, you spend $100 and get a gift certificate for $115, or spend $1000 and get a gift certificate for $1150. You can order this by email or phone, and I can mail it to the intended recipient.

Thursday, November 20, 2014

Are fat wheels heavy?

I think most smart bike people will acknowledge that fat tires have superior traction and flotation on sketchy surfaces, in winter conditions, etc. But the tradeoff is that they're so heavy and slow!

Thirteen years ago, the University of Minnesota decided to grant me a master's degree in geophysics, and I figure it's finally time to apply that credential to some useful purpose. So why not start by measuring something. Here's a 120tpi Dillinger 26x4" on the scale:
The scale reads 1352 g with packaging included. Add in a Q-tubes 26x2.4-2.7 superlight tube and a standard Marge Lite rim, and we have a tire/rim mass of approximately 2.28 kg.

For comparison, consider a more "typical" winter bike wheel. A Schwalbe Marathon Winter 29x2.0 studded tire is listed at 1265g. On a typical 520g rim with a typical 220g tube, this typical winter wheel weighs in at just over 2.00 kg.

But the acceleration of a wheel with an applied torque is not quite as simple as a basic mass comparison. We also have to consider the size of the wheel, since mass farther from the center of rotation is harder to accelerate. The important physical quantity here is moment of inertia. The lower this number, the faster the wheel accelerates under a given torque. Most cyclists prefer a lower value for moment of inertia, though having a higher value increases rolling momentum, which is desirable sometimes. If I assume that the effective radial center of momentum of each wheel is in the center of the tire (halfway between the rim bead seat and the outer tread of the tire), the 29" wheel has an effective radius of approximately 0.340 m. The fat tire 26" wheel has an effective radius of approximately 0.330 m.  The formula for moment of inertia is I = m x r x r. So square the radius and multiply by the mass. For the fat tire 26" wheel, the value of I is 0.24 kgm^2. For the 29" wheel the value is 0.23 kgm^2. These are about double that of a typical high-performance road racing wheel.

I consider these two inertia values to be effectively the same, given the simplifying approximations I made. But the fat tire is widely regarded (by armchair experts) as heavy and slow, while almost nobody thinks to comment on how heavy and slow a typical 700C/29" winter wheel is.

Note that I'm assuming that the mass of a hub and spokes don't contribute to the inertia calculation. Assuming the same hub mass, the 26" wheel has a slight advantage because the spokes are shorter and lighter. But the more important mass is further out on the wheel. That's why I just consider the mass of the rim, tire, and tube. Also, I'm not considering the effect of tire rolling resistance or aerodynamics. My general sense is that a high-quality fat tire inflated to an appropriate pressure has lower rolling resistance than a Schwalbe Marathon Winter, but the skinnier tire has lower aerodynamic drag.