https://www.dropbox.com/s/d19b11jzreapxkd/20180423_150345.jpg?dl=0

My wife has just got a road bike and is happy with it apart from the gearing. Transferring from a 9 speed, 3 ring mountain bike to a 2 ring road bike with a high geared cassette means hills are a struggle so far.

Looking to a different rear cassette – what would I get away with using the existing rear mech, or do I have to change that too? Anything else need changing. Existing Cassette has 28 as lowest gear, maybe looking at 32 or 34.

Thanks

Honestly, assuming she has a 50/34 chainset currently, I’d look to a smaller chainset, something like this:

https://www.spacycles.co.uk/m2b0s109p3383/SPA-CYCLES-Super-Compact-Chainset-with-Zicral-Rings

That way you keep nice close gaps between the gears on the cassette, which is better on a road bike, but you have the gearing to get up stuff when needs be. Sure, she’ll spin out at a lower top speed, but does that really matter?

Thanks that is helpful!

If your budget is significantly higher, or you want to avoid a square taper BB then FSA have launched an Adventure range of low ratio cranksets:

https://www.fullspeedahead.com/en/fsa-world/future-super-compact-cranks

https://www.bike-components.de/en/FSA/SL-K-Modular-Adventure-Supercompact-BB386EVO-Carbon-Crankset-p61059/

I use the Sugino OX901D cranks on my 650b drop bar bike with 44/30 chainrings and its versatile enough for riding club runs, for touring and for off-road using a 11/28 11 spd cassette. They do a cheaper version as well called the OX601 which is a fair bit cheaper.

To answer the original question: I think it’s unlikely that that RD is designed to work with anything more than 28T.

Would be useful to know what chainset you’ve got at the moment. Assuming it’s already a compact, I’d suggest changing the cassette and rear mech as it’s much cheaper, and you can try out different options easily.  It looks like 8 speed, so new cassette is about £10, MTB rear mech £20.

Personally, I wouldn’t worry too much about gaps in the range.

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means hills are a struggle so far

That’s the key bit for me. They do get easier, or she’ll get fitter, whichever way you want to look at it. 😉

Other more realistic advice in previous replies though.

We really need to know what is currently on the bike in order to give you some ideas. Cheapest way is to find the limit of your current RD and see if that is enough for you just to change your cassette. If not then its new RD and cassette time which means you may have to be mindful that you buy something with the same pull ratio as your gear lever.

What model is the rear mech? Medium or short cage? Current chainset/rings?

48/32 – 11-32/34 is probably as low as you can go in road before you need to start looking at mtb gearing. Need to check bits and pieces are compatible mind.

Just checked. Cranks are 50/34. Nine speed

http://www.wiggle.co.uk/shimano-hg50-9-speed-cassette/?lang=en&curr=GBP&dest=1&sku=5360560448&kpid=5360560448&utm_source=google&utm_term&utm_campaign=UK_PLA_Components&utm_medium=base&utm_content=mckv%7CsX3LGg1UE_dm%7Cmcrid%7C67090789502%7Cmkw%7C%7Cmmt%7C%7Cmrd%7C5360560448uk%7Cmslid%7C%7C&mkwid=sX3LGg1UE_dm&pcrid=67090789502&prd=5360560448uk&pgrid=17507338502&ptaid=aud-131236049102:pla-304066957368

Sora 11-30 it’ll work with most derailiers, if it doesnt youve lost £19.

I wouldnt bother bodging chainsets,  34/30 should be ok for most situations in the UK, if not ride a few flatter routes until fitness and weight improve.

Just checked. Cranks are 50/34. Nine speed

Work out gearing way, tyre size isn’t changing so you don’t need to worry about tyre size.

50/34 – 11/28

= 50/11 = hardest gear = 4.54

=34/28 = easiest gear = 1.21

divide the big ring by what you are using at the back = gear ratio

32/32 = 1, which should be much easier.

32/34 = 0.94, even better.

Must admit, I’ve never actually rode road gearing before. Only reason I’m looking at is is I’m thinking about buying a gravel bike. Road gearing is mental. I think there’s a middle way required inbetween mtb and road. can call it gravel or bimbling about gearing! 😆

1x sounds good to me actually

38/42 is 0.9

36/42 is 0.85

(who cares about top end speed!)

12-36 for £19: https://www.merlincycles.com/shimano-hg400-9-speed-mtb-cassette-48272.html

9 speed MTB rear mech for £21: https://www.tredz.co.uk/.Shimano-RD-M370-Altus-9-speed-Rear-Derailleur-SGS_65139.htm

36 might be overkill.  It’s 28% lower than the 28T so very roughly equivalent to 2 additional, well spaced gears.  It depends how much she’s struggling at the moment, but I’d err on the side of too much range rather than not enough.  Being able to ride up hills “comfortably” = enjoy riding = ride more = get fitter faster.

pdw has it for me, tho you’ll need some chain links unless she is careful with gear selection

Chris Froome ran a 34 cassette on the steepest mountain sections on last years TDf so if it’s good enough for him then it’s good enough for anyone. Not sure why there is so much macho ‘advice’ about just sticking with 28 and just get fitter and stop whinging. Wasn’t so long ago a 28 was considered only for the softies back when the biggest cassette was a 25t and 28’s were just coming in. There is no shame in getting a wider range cassette and it is much more efficient to increase cadence anyway, especially on climbs. Also having that extra low bale out granny gear can be the difference between completing a ride or quitting and calling the taxi of shame on a particularly long ride when you’ve got a big alp to climb in the last 20km or something like that. One of the advantages of cassettes with more and more sprockets is that you can have that additional bale out gear for the odd occasion you need it. It’s about fun and enjoyment at the end of the day and not the ultimate human challenge – well for most of us it is at least.

I have a 46/32 on my Arkose. The big ring gives a really nice spread of gears for road cruising speed and the small ring is noticeably lower than the compact on my road bike.

You can get a 33 for the front as well to get a bit more range. TA do a zephyr in this size and it will work fine with the 50 big ring on my bike

Froome didnt have a compact chainset with that cassette though.

34/30 is fine as a low for 90% of riders 99% of the time.