Hey guys. So i can't figure this one out. I recently switched from a Tarmac ELite (mixed 105) to a Tarmac Expert (Ultegra 6700). I had my ksyrium elites on both. The issues is this: the elite had 12-27 cassette, whereas the expert has 11-28. Theoretically, these have very similar gear ratios, and I have a noticeable speed increase on flats, climb faster, etc. My problem is that for the last 2 weeks, my legs have been incredibly sore. I got a fitting with the bike, have same shoes/pedals, etc. The bike fits well, and I am thinking this may be due to the cassette. My only other explanation is that I am subconsciously pushing myself harder and making myself sore. Any input? Thanks.

I can see no way a cassette could make your legs sore.
There's another reason, probably a fit issue, maybe you're going all out on the new bike.

if the gear ratios are a little off from what you're used to, i suppose you might be either spinning more or mashing a little more, but i wouldn't expect the difference to be noticeable.

what exactly is sore? quads? hamstrings? you said you got a fit, but that doesn't mean your fit is exactly the same as it was before (unless you measured and made sure). i think a new body position is a more likely suspect than a new cassette.

also, you mentioned that you "have a noticeable speed increase." the bike and/or cassette shouldn't have too much of an effect on that (at least not the upgrade you're talking about), so maybe you are just pushing yourself harder.

You just spent a bunch of money and need to prove that it was a worthwhile investment. After all, you wouldn't want to go slower on the new, more expensive bike. So you check your speed constantly to verify that it is higher, and it will climb on its own if you notice it looks on the low side...

Either this or new bike fit issues. Leave the poor cassette out of this unless your counting gears i.e. if I was in gear 'ten' on the old one I should be in gear 'ten' in the new one too...now you're pushing that 11 with the same cadence...

It's definitely the cassette. If you don't go back to a 12-27, you're destined for a lifetime of soreness.

Gosh no, it couldn't be that. It's perfectly logical that your increased speed is solely due to the new bike. Just going from 105 to Ultegra alone is worth at least 1 mph average speed. If you're not getting that, you should go back to the LBS and complain.

Unless you were uncomfortable, set your new bike up EXACTLY the same as your last. Spend a good few hours making sure you have it right and ride both to check they are the same. Fits are over rated.

Your new fit may be "correct", but if it's different from your old bike, it takes time for your body to adapt, and you can be sore for a bit.
Or maybe your old fit was better ...... what's the difference in seat height between the 2 bikes ?

How you can bring a cassette into the discussion when switching bikes & fit doesn't make any sense.

Big hill. Smaller cog. No rest.

cassettes can cause you pain, when they're thrown at you and hit you in the head.

Ninjas I believe centuries ago used to take apart Dura Ace cassettes and fling those shiny cogs at the enemy. Even then there was considerable debate over whether a 12 or 13 would better suit a particular 'application'.

Hey guys. Thanks to those who added valuable input and a bit of comic relief. Admittedly, it sounded dumb when I was writing, but it was the only thing I could think of that changed. As far as fit goes, I switched from a 110mm stem to a 100, but don't think that would have any affect on my legs. The only other fit different may be in seat height, but I don't have my old bike to compare. I will play with that a bit and see if it helps.

crank arms the same size? that probably wouldn't matter much, probably more of a saddle position issue. I'd check fore/aft placement in relation to crank, compare the two. height too of course if you haven't.

So where exactly are you sore again? Quads, hamstring, lower back, hands? More info would help...

Sorry. Quads are the only thing that are oddly sore. I messed with my saddle height and made sure it loomed fine. Also, the crank arm lengths are the same. I'll ride tomorrow and see if the saddle adjustment knocked it out.

I'm guessing your bike fit is not the same as your previous bike. The only issue I see w the two cassettes is that the 11-28 has gaps starting on the 15 then jumps to 17 and gets wider from there throwing your cadence off.

I would guess that you're trying to ride the "same cogs" with the 11-28 as you were with the 12-27. This would explain being faster. With the new gearing you're having to do more mashing with the 11-28 than you would with the 12-27.

Don't be afraid to drop to larger cogs with the new cassette gearing. I went from a Shimano 105 12-27 (12-13-14-15-16-17-19-21-24-27) to a SRAM Red OG 1090 11-25 (11, 12, 13, 14, 15, 17, 19, 21, 23, 25 ) with a 53/39 crankset. I can go faster on the flats but I don't find myself using the 11t cog as often as you would think. I've quit mashing like I used to (building muscle) and have focused on being in a comfortable but fast cadence. I'm keeping the same speed but not using the quads as much as I previously was.

So, my guess is that you're mashing - even though you don't know it.

Bike fit's can be fickle. I know I am not making the power on this bike that I made on my previous bike. Just keep at it making one adjustment at a time till you get it right.