Post your road bicycle

Was the "B" screw adjusted to accommodate the larger pulley gap needed for the 40T sprocket? This screw, while some think it's only for chain tension, is used to adjust the angle at which the derailleur moves across the cassette. The shallower the angle, the quicker and more precise the shifts. Depending on the amount of adjustment made at the "B" screw, re-indexing may be needed, but likely only with the barrel cable adjuster.

Info here: https://www.parktool.com/blog/repair-help/rear-derailleur-adjustment


EDIT: Another thing to check is to be sure the QR axle is sufficiently tight when on the trainer. If it is even a little looser then on the bike, the indexing will be off. A mm off in either way will affect the index.

 

New gravel/road steed. Trek Checkpoint. Really like it so far. 18# gravel bike and the AXS shifting is pretty nice. Still sorting out minor ergonomics, but it's able to handle more watts than I'm currently putting out. lol.

 

That is an odd one. All the gears are off or just trouble on the bigger cogs? With the DI2 indexing is a breeze . You can actually do it on the fly while riding, Both cassettes are same brand and same model (which all 3 groups should be the same) ? Is there by chance a spacer on the trainer hub/cassette setup ? Just thinking out loud.

 

You can buy longer b-screws too if you run out of adjustment when trying to stretch an old derailleur into an un-approved use case.

 

I think I found out the issue. All my 11-36T cassettes are SRAM including the one on the trainer. The new 11-40T cassette is an XT Shimano and I'm told it needs a spacer behind it. I haven't tried that yet but it makes sense. I used the trimming on the Di2 to get the shifting on the trainer just right so I can do my plan today. Later on I'll add the spacer to the wheel and pull the bike off the trainer and try it.

 

Is your saddle tilted a lot forward? Maybe it's just the angle. Good looking bike, for sure!

 

Keep us posted. While it sounds plausible, not all Shimano cassettes need a spacer against the free-hub (I know you referenced a specific cassette). Personally, learning from your situation would be good knowledge to store in the bank as it relates to XT cassettes for the future.

 

Just found this thread on the same subject: https://www.bikeforums.net/bicycle-mechanics/832959-cassette-install-question.html

Simple rule that applies to ALL cassettes and ALL freehubs. Once you learn it you'll never need to ask again.

The cassette must overhang the front of the freehub body by a millimeter or so, so the lockring can compress the cassette without bottoming out against the freehub body. Use enough spaces behind the cassette to achieve this if/when needed.

It's analogous to how threadless headsets need the spacer stack to be taller than the steerer for the same reason.

BTW- if you have multiple wheels that you swap out on the same bike, there's another consideration. If you use spacers to bring the outer sprocket to the same distance behind the axle face on all the wheels, you won't need to adjust limits or trim when changing wheels back and forth.

 

The only spacer I had lying around is too small. I'll get a spacer on Friday but I've confirmed with 3 others in the know that the XT mountain bike cassette will need a spacer behind it. A Shimano road cassette does not need a spacer.

 

Yes Shimano road and mtb freehubs (& cassettes) are different widths, 1.85mm difference. Same difference between Shimano 11sp and 10sp road coincidentally. Maybe check your box of trainer spare parts as some brands include them with the trainer, at least mine did (elite).

 

Should be the same spacer that's used for putting a 10 speed cassette on a 11 speed hub. Glad you got it figured out.

 

Just picked up my first bike since I was a young lad. Its a Trek FX2, from the minimal research I did seems to be a good mix of features to price. As soon as I saw the hydraulic disc brakes I was sold

Figured since the gyms are closed this will help keep the Covid 19lbs off my ass. I know next to nothing about bikes but figure I'll just start peddling and slowly upgrade as needed. Definitely need to get a mount for the truck. Never knew it would be so painful putting a bike in the bed and not wanting it to get scratched.

 

You were right. My Wahoo Kickr trainer had a 1.85mm spacer in the bag of stuff that came with the trainer. So, I should be good to go. I'm doing a ride on the trainer in a few hours and once done I'll pull the bike off the trainer and see how it shifts with the wheel on it.

 

Good catch. It shifted down an a rough gravel road w/potholes. Part of why I stopped was to fix it.

I've ordered a shorter stem, as the saddle is too far forward to make things comfortable. Hoping a shorter stem will allow me to slide the saddle back a bit (and not be so forward-mounted), which will help it not move around on bumpy roads where all the weight is on the front edge of it.

 

I have one of the ISM saddles on my bike. They're short, but still offer support where you need it. Have you considered them? I have the Typhoon. https://ismseat.com/help/product-archives/typhoon/

 

Those looks nice, thanks. Ever hear of Infinity saddles? Some of my mtb buddies swear by them.

 

Nice! I have a friend with one of those. As a former road racer I was really pleased with how quick that bike rolls. Great choice.

 

Before you go changing saddles, stems, etc., be sure you adjust the fore/aft position of the saddle so the back of your kneecap aligns with the axle of the peddle (as seen in the pic below). Once you get settled in the proper saddle position (peddle backwards a few rotations with someone holding the bike upright so your hands are on the hoods/bars in a normal riding position), use a laser level to align the laser with the axle of the peddle with your right foot at the three o'clock position. The laser should align with the back of your kneecap AND the axle of the peddle. If it doesn't align with the back of your kneecap while aligning with he axel of the peddle, adjust the fore/aft of the saddle until it does. this IS your starting point. From here, determine if the stem needs to be shortened or lengthened for comfort, but not for alignment. The stem has very little to do with alignment. Saddle height, saddle fore/aft, and cleat placement (directly below the ball of your foot) are critical for proper body mechanics. Stem length/height is comfort related.

With that said, an incorrect frame size will only allow you to adjust things so far before you're at an impasse of proper body mechanics and comfort. That is why getting the correct frame to begin with is so critical.

 

Took the bike off the trainer and put the wheel back on with the spacer installed. Shifted like butter with no trimming needed. Thanks again.

 

Which one of you kids knows someone who knows someone and can give me a hint on when the SL7 Tarmac will be out? Or even when they'll bring the existing bike back into stock?

Tried to buy the Tarmac Pro a couple of months ago, and they were out of stock in my size. Trying to decide whether I keep waiting or get something else.