Mixing Shimano A type & B type chainrings

[rando]

I'm finding after over a decade with the same bike running the same parts a few group/era specific points have faded from memory.

Bike is running a full Ultegra 6700 group with severely worn out 39/53 rings. Today I came across a deal too good to miss on a DA 7900 54t. FD works just fine with matched B type 34/50 compact crank(16t spread).

The question is will finesse and possibly some mechanical jiggery pokery allow one to continue spirited riding with the mismatch. Or should I forget I ever considered it and hunt down a 42t. After 4 notices parts were backordered and a few outright refunds due to non-existent stock in the last week. I'm solid on the fact there is a new 6700 39t inner ring in my parts bin. Procuring the matching A type 42t is actively being considered a crapshoot since I can't trust online stock trackers.

[oldpotatoe]

Originally Posted by rando

I'm finding after over a decade with the same bike running the same parts a few group/era specific points have faded from memory.

Bike is running a full Ultegra 6700 group with severely worn out 39/53 rings. Today I came across a deal too good to miss on a DA 7900 54t. FD works just fine with matched B type 34/50 compact crank(16t spread).

The question is will finesse and possibly some mechanical jiggery pokery allow one to continue spirited riding with the mismatch. Or should I forget I ever considered it and hunt down a 42t. After 4 notices parts were backordered and a few outright refunds due to non-existent stock in the last week. I'm solid on the fact there is a new 6700 39t inner ring in my parts bin. Procuring the matching A type 42t is actively being considered a crapshoot since I can't trust online stock trackers.

Plug and play. The ramps/pins gig are some computer generated thing about when and how people ‘may’ shift but in actual practice, it means a whole lot of nuthin..

[Mikej]

I'm running R9100 50/36 Which should be 50/34 and the 36 is fine. FWIW

[rando]

Originally Posted by oldpotatoe

Plug and play. The ramps/pins gig are some computer generated thing about when and how people ‘may’ shift but in actual practice, it means a whole lot of nuthin..

I accept that opinions merit given the direction of development in last decade. Electronic shifting = reinforce the mounting points and shift through application of sheer force. As usual refinement lies in arm of person/impulse applying mechanical adjustment.

[jamesdak]

Well, like Pete said, ultimately they are all gonna shift. But, if you want the quickest best shifting rings out there I'd look at Wickwerks. I've ran 3 different setups of his stuff and they work so well.

https://wickwerks.com/product-category/chainrings/

First was an odd 53/34 setup he wanted me to test. On the upshifts I swear you just start to push the shift lever over and the jump is already made.

Than I've got a more standard setup and it's the same way.

Finally he cobbled together a triple setup for me that he said wasn't optimum but it works perfectly out on the road.

His rings are on a ton of CX bikes in Europe.

Now that said....you do have to get past the looks sometimes....



If I remember correctly the two inner rings are mountain ones while the outer is for road.

[rando]

Originally Posted by Mikej

I'm running R9100 50/36 Which should be 50/34 and the 36 is fine. FWIW

You went in the opposite direction on the opposite end of physical equation being pondered here though. Mathematically and mechanically, maintaining ideal behaviors is more complex on the upper end of chainring sizes. Until you physically impede functionality by fitting inner ring too close in size to outer much greater latitude exists.

[jamesdak]

Originally Posted by rando

You went in the opposite direction on the opposite end of physical equation being pondered here though. Mathematically and mechanically, maintaining ideal behaviors is more complex on the upper end of chainring sizes. Until you physically impede functionality by fitting inner ring too close in size to outer much greater latitude exists.

I thought this was an english speaking forum.

[rando]

Originally Posted by jamesdak

I thought this was an english speaking forum.

For my own part I wondered if this was still a... it doesn't matter.

Thanks for doing your part buying and advertising new stuff to keep all of these companies afloat.

[oldpotatoe]

Originally Posted by rando

For my own part I wondered if this was still a... it doesn't matter.

Thanks for doing your part buying and advertising new stuff to keep all of these companies afloat.

I think he's just giving an opinion about some chainrigs that work really well for his rig. Doesn't sound like he's being a shill for wickwerks.

BUT, back to the original question..you can worry about computer generated studies about shifting techniques..or just buy the 'miss matched' CRs and go ride.