Category Archives: Cycling

SRAM Apex Brakeset 2012

. Cycling, Product Weight

I’d been interested in improved braking and modest weight savings for my newly rebuilt bike. The SRAM Apex brakes fit that bill. The new brakes saved 49 grams over the old stock brakes, originally from a ~2001 Trek 1000. At less than 1 gram saved per dollar, that’s not a lot.

Braking performance was noticeably improved. Whether it’s from the shoe-based pad design, or from different pad material, I’m not certain. The flex of the calipers is comparable to the previous brakes, so I don’t think it’s due to different caliper design.  I have a couple hundred miles on them now, in mostly dry and some wet conditions. Dry and wet braking meets or exceeds expectations.

Masses checked out nicely. SRAM claimed 308 g for the set (and still does for 2013 — unchanged?). At 152.8 g for the rear brake and 155.9 g for the front, I find 308.7 grams for the brakeset – easily within the 1-gram uncertainty implied from the quoted number’s significant digits.

sramApexFrontBrake sramApexRearBrake

Michelin Kromion

. Cycling, Product Weight . ,

New tires came with the saddle. Manufacturer spec is 230g.

231.7 g and 235.5 g. At worst, 2.4% off spec. Drawing the same inference as in the previous entry (with no extra conservatism), this yields (with some uncertainty about the 3.4): 233.6 +/- 3.4 g, easily consistent with a 230g spec.

I saved less weight than I’d expected simply because my worn tires were lighter than specified by the manufacturer. I’m looking forward to lightening these Kromions further by riding!

Folding tires are a really inexpensive way to pull a little mass (and moment of inertia) out of your bike. Wire beads are heavy.

Nashbar R2 Saddle

. Cycling, Product Weight . , ,

New saddle arrived. Feels nice, feels light, looks cool, magnet doesn’t stick to seat rails.

Nashbar claims 191 grams. I get 205.8. That’s 7.8% high. Weighing, as before, used the AWS Blade scale calibrated using the 200 g weight.

I wanted to put this in perspective, so I looked up the prices of the other saddles that Nashbar sells.

My first takeaway is that old-style riveted leather saddles are heavy. The second is that, while the R2 remains a value, I’d be very unhappy with Nashbar’s claimed 191 g weight if I manufactured the 190g saddles priced at $50-55.

I see 8% less weight savings than expected using the R2, but how much less attractive does that make the saddle?

As shown in green, the claimed weight netted me weight savings at $87.57 per pound. In reality, it cost me $95.35 per pound, and my bike’s mass is 15 grams more than expected.

Reviews at Nashbar.com state that the saddle weighs 214, 208, 209, and 220 g.  Averaging them together with the measured 205.8g yields 211 +/- 5.7 g. With only 5 samples and normally-distributed data, the uncertainty in the variance is considerable, and is slightly underestimated (by 7 %). Call it 211 +/- 6 g. Since Nashbar has lawyers, we don’t have very many samples, not all scale users know what they’re doing, and process variations aren’t always Gaussian, let’s double the variation, to 211 +/- 12 g (that’s almost an ounce variation, peak to peak).   Using these data, if the saddle masses are “normally distributed”, less than one in ten saddles will have mass at or below 191g. 

Weight-wise, the R2 remains a compelling value for budget-minded buyers, just not the exceptional value 191g presents. If the R2’s mass is consistently higher as than 191g, as reviews indicate, then the saddle is improperly labelled and advertised. If the manufacturing process yields saddles that are 176g as often as it does 206g saddles, quantified variation (expressed as 191 +/- 15 g) would be a straightforward consumer resource.

Crank Brothers Eggbeater 1

. Cycling, Product Weight . , , , , ,

Over the weekend, we went on a long bike ride. It was fun, but I was slower than I wanted. So, in addition to resolving to get more exercise, I took a look at the weight of my bicycle.

Lots of disassembling, weighing parts, and playing with spreadsheets ensued. Ultimately, I decided to replace my worn tires (wire beads add 100g per tire!), rattly clipless pedals, and saddle. If manufacturers meet spec, I’ll have dropped about a pound from my 24 pound bike for ~$100. This isn’t the optimal weight/dollar way to get to a 18 lb bike, but it’s a way to spiff up a favorite bike.

The first package arrived in the mail yesterday – Crank Brothers pedals from REI. Listed as 256 grams per pair,  these should save 110g over the old pedals. Opening up the package, they look and feel great.

Image

Here’s what arrived. 280.2 grams.

Nearly 10% high. For a weight quoted to three significant figures in an industry obsessed with weight, that’s a letdown. In real terms, it’s the weight of an extra granola bar per pair. Or, if you’re a triathlete, three quarters of a pack of GU. As a customer, I saved 22% less weight than I expected with this purchase.

It’s not a gross manufacturing inconsistency; the two pedals mass 140.0 and 140.3 g (+/- 0.1 g statistical uncertainty).

Balance is an American Weigh Blade 400, calibrated with an American Weigh 200g calibration mass. At present, I trust the calibration mass to about a gram. The manufacturer specifies at least 0.1 g. I haven’t yet checked it on a superior balance.