Here's the unique bit - I only want to use the first 7 cogs, 11-19t. 11-12-13-14-15-17-19. So I'll be ditching the carrier with the 3 biggest cogs on.

Is there any significant difference in weight on those 7 smaller cogs? Or are they pretty much identical?

If anyone here has a cassette handy (i.e. not on a bike) that they can quickly weigh the bottom 7 cogs & spacers for me, that'd be great

Thanks!

No-one?

I have both at home off the bike. I'll weight them tonight if I remember and post up the results.

I just threw my old 105 cassette away . But, if I remember correct, they weighed almost the exact same. Both had the largest three on a carrier and the rest were single cogs. The Ultegra came with an aluminum lockring, which is where any weight savings came from.

OK thanks. I can obviously source a light lockring from elsewhere. Certainly in the shimano PDFs and photos the smaller cogs look very similar, but they have different codes and I wasn't sure if the Ultegra ones used some fancy lighter steel alloy, or were drilled out a bit more, or similar.

Woody - that'd be excellent if you can

IIRC there's a 3gm difference between the two cassettes and that's actually the lockring.

Main difference is in the finish. 105 is smooth, chrome-y, with a tint. Ultegra is blasted or shot peened or something. Either for wear resistance, hardness, lubrication retention, whatever.

OK thanks, 105 ordered.

Surprised that the weight difference is only a few grams..... Who knew?

@Downhiller - good choice ordering the 105 cassette. Sorry I didn't get back to you yesterday, got busy with life.

I had a chance to take some weights between a 12-25 6700 cassette and a 11-25 5700 cassette. They are not exactly the same but I was able to take a bunch of weights and this is what I discovered. Sorry, I forgot to take scale pictures, so un-WW of me...

As others pointed out the main difference is in appearance, the 105 is shiny and the ultegra has a shot-peened look. The weights between the actual gears themselves are with-in my scales tolerance of 0.1g. I would say, despite the appearance, the 105 gears and Ultegra gears weigh exactly the same.

The biggest difference is in the lock-ring as someone previously mentioned 105=12.9g and Ultegra=5.5g. The other interesting point is that the spacers between the gears on the 105 are plastic at 2.2g each, whereas the spacers on the Ultegra (I assume are aluminum) and weigh 1.6g each. Even the 3 largest gear clusters are almost the same weight, both 21-23-25, with the 105=106g and the Ultegra=105.2g.

Looks like the 105 cassette is quite a bargain for all the bargain-weenies out there.

Good info Woody55,thanks foe weighing and posting up your findings.

Good info woody, thanks! Odd that the plastic spacers weigh more than the aluminium ones - I assume they're a fair bit bulkier? Not an issue anyway, we're talking fractions of grams now!