What cassette/chainring combination

ianaveitchvVMbxPt4

I got a bit of a bargain of a bike for my wife who used to ride a bit but does a bit of mountain biking now. However, she is doing a 40 mile road race with a couple of 3 mile climbs in May (5% up to 10% for very short periods) and isn't very fit at the moment. The chainring set up was for triathlobs or time trials i think and is is a 53/39T and a 11-23 cassette. It has a Ultegra 10 speed short cage derailer. I will probably have to change the 53 chain ring as its worn, so i was thinking of a 50T (but I've not seen one at 130mm 5 hole), but wanted to know just how far i could go with a cassette. I want to make sure she gets the best possibility climbing on it (IE not having to walk). so can i go as far as a 11/32 or even 11/34 cassette, or should i do a 11/28 or 12/30? I believe the maximum capacity of the derailleur is 33 but I'm not sure the maximum cassette size.
I cant help feeling it would be easier to get a new bike (or new wife, but can't tell her that)

MattFalle

Short cage mech is 28, some say a 30 with some faffing (reversal of B screw and fiddling but its a hassle.)

Easiest thing to is get a compact chainset in the sales - any with a 24mm diameter spindle will fit. Easier and cheaper than new chainrings - its very unlikely you'll find 130 bcd compact chainrings.

New KMC chain and boooooooooom sorted innit, gezzer, blood, bruv.

shop around, you'll get it all for £70/80.

#speedyyetthrifty

N0bodyOfTheGoat

My Cube Attain came with 34/50 chainset and 11-32 cassette, sprocket sequence was...
11-12-13-14-16-18-20-22-25-28-32
For me, that effectively gave me 18-32 sprockets to use on climbs.

I swapped to an 11-34 cassette in the summer, sprocket sequence is...
11-13-15-17-19-21-23-25-27-30-34
This effectively gives me 17-34 for climbing, a larger range and more gear combinations. I don't race, so the two tooth jumps 11-17 don't bother me that much, but sometimes it seems weird if I'm pushing on over flat/rolling terrain and see the chain so far over to the right of the sprocket cluster.

I'm going to need a new chainset (or at least rings, but they are usually pricey compared to a chainset) sometime this year, problem is the big Shimano price increases this past year and simply stock availability. I'll probably go 34/50 again, but if the price is more right, I might go 36/52.

Gearing is such a personal thing, depends upon factors including your ability, plus whether you want to smash up a climb or simply spin comfortably up a metaphoric wall.

https://www.sheldonbrown.com/gear-calc.html is a well known calculator for seeing gear ranges.

hdow

The 10 speed Ultegra SS rear derailleur (if model RD-6700) should take a 34 tooth cassette according to some specs I've come across. Worth checking out what you have fitted. However, not many new ones about so a 105 (30 tooth for SS & 32 tooth for GS) may be required.
I fitted a 10 speed 105 GS plus 11-32 cassette to my 53/39 chainset TT bike and got over Kirkstone's Struggle pretty well. Also gets me up Pateley Bridge's hills with a bit of effort. Agree with MF's post that just a compact chainset would work as I've done this with previous bikes. Also agree about KMC chains.

dj58

If your RD is a 6700-A-SS, it is rated up to 30T max low sprocket with a double/compact crankset, the outer upper jockey wheel cage is stamped 30T. You could probably get it to work with a 11-32T by adjusting the B-tension screw and/or using a longer B-tension screw, care needs to be taken with chain length and no cross chaining the big-big combination. Spa Cycles sell 130 BCD 5 hole chainrings.
https://www.spacycles.co.uk/m8b0s113p0/Drivetrain/Chainrings-TA