HalfHearted

I'm looking at a hybrid bike that comes with a Deore crankset with 48/36/26 chainrings and a Deore front derailleur. Would there be any problem if I replaced the middle and inner chainrings with 34 and 22 (I believe these are the "standard" chainrings for the Deore crankset anyway) but left the 48 tooth outer ring? (BTW, the rear is an 8-speed 11-32 with a SRAM ESP 7.0.)

Will the derailleurs be able to take up the slack over this wide a range (from 48-32 to 22-11)? Will there be any problems with the chain trying to shift up over such a wide step (i.e. 22 to 34 and 34 to 48) up front?

If need be I'll change the outside chainring too, but I kind of like the idea of keeping the taller gears for those days when the road is flat and the wind is on my back.

Thanks for your thoughts,
John

pokey

Shouldn't be a problem,assuming you BCD is such that you can actually use a 22.Your derailer will wrap 45 teeth and you are doing 48,so if there is a problem just stay out of the few mallest cogs when in the granny ring.Shimano front derailers have 22 tooth capacityand you are trying for 26,but specs are usuallly concervative and can be exceeded.

Greg

Try to get the shop to fit the ring prior to purchase.

Some special order rings run at a premium cost although I'm not sure in this case. Inquire at the shop.

MichaelW

There may be a problem downshifting from middle to granny if the gap is more than 10 teeth. The front mech moves diagonally. so as it moves down, it moves inboard. When I put a 26t on my Campy triple, the 38-26 move was too much and the chain would often get dumped off the granny onto the bottom bracket. The Shimano mech may be able to cope with a 12t shift, but it cant be guarenteed. Generally, the limits given in the specifications can be exceeded a little.

If you look at the gear combinations in terms of "gear inches" you will find that 22/11 and 48/32 can be duplicated with other combinations with better chainlines. Extreme crossover gears should never be used.

pokey

It may vary acording to specific case,and shifters may have alot to do with it.I have heard of people successuflly using a 26/42/52 with a Shimano road derailer and STI. Your case of dupming onto the BB may have been setup of other factors...maybe not. I have certainly used more extreme setups.

pokey

How do you get a 38 on a campy crank?I thought the smallest with a 135bcd was 39?

HalfHearted

Thanks for all the help guys. I think I'll just try it and if it doesn't work out I'll go ahead and drop to a smaller outer as well. I've checked on the availability of the rings for the 104/64 Deore and getting reasonably priced 34 or 32 middle and 22 inner rings is no problem.

John

MichaelW

Yes Pokey your right. It was a TA 39 tooth ring, so the difference was 13 teeth, which is definately too much for the Campy mech to cope with.
Surprisingly, the mech and shifters works very well with a replacement Shimano LX chainset.