Will my derrailleur work with a bigger cassette?

[arupaka]

Hi everyone,

My girlfriend is having some troubles with her road bike: she complains the gearing is too heavy. At first I thought "maybe you need some more training ", but after researching a bit I found the gear ratio to be of 42:25 (small chainring vs big cassette cog). Seems quite a bit!
We live in a place that's not flat at all, so now I understand her struggle.

BTW, cassette is 8gears 11-25, crankset is 52-42.

After doing some more research I learned the cheapest way to improve this situation is to simply replace the cassette, a task I know I can do! (In truth, it would be great to install a triple cog crankset, but seems like too much hassle.)

So the problem is that the derrailleur's brand is unrecognizable, so I have no idea if it will be ok to go for a 32T cassette (30T could also work for her). I've read that you need GS derrailleurs for 32T cogs, but in my ignorance it seems like that's the case for 10+ gears (??). Because the shimano Claris or SORA 8g SS seem to accept up to 32T.

Is there some way to understand how big can I go, before actually buying the part?

A second question is: If it works, will I need a longer chain? I've read that as long as the new cassette is 8gears it should be fine. Tried to take a picture of max slack in biggest cog (rear and front) configuration.

I don't mind replacing cassette, derailleur and chain, but I'll probably need some new tools for the chain :\ Preferably would just replace the cassette and hope things get sufficiently light.

Some pictures:







front derrailleur says microshift, but I suspect it's unrelated to the rear one.



Hope I made myself clear!

Thanks

[richardfm]

I don't know for sure, but I would expect the current derailleur would work with 32T cassette.
You may have to adjust the b screw https://www.youtube.com/watch?v=y3x13dD0UiQ
If it was me I would replace the chain whether the length was OK or not.

[alexnharvey]

A switch to a front crankset of 50/34, or a triple chainring, with a wider range rear cassette will transform the gearing. It will likely also require a longer rear derailleur. You should switch the chain too if you're replacing the cassette.

If you don't want to change the cranks then you could fit a 38 or 39T inner chainring instead of the 42.

[arupaka]

A switch to a front crankset of 50/34, or a triple chainring, with a wider range rear cassette will transform the gearing. It will likely also require a longer rear derailleur. You should switch the chain too if you're replacing the cassette.

If you don't want to change the cranks then you could fit a 38 or 39T inner chainring instead of the 42.

You reckon a 38T inner chainring would be better than a 32T in the rear?

Thanks!

[alexnharvey]

I'd do both if you like in a hilly area, 38t and 32 cassette.

[arupaka]

I'd do both if you like in a hilly area, 38t and 32 cassette.

of course!

checking what's available right now; for a given chainring there are 3 options: single, double, triple. If I don't follow this I'll be in trouble when mounting? (Mine is double).

TIA

[alexnharvey]

You would choose the double unless you intend to also fit an inner ring. A double inner will not have any pins and ramps on the inside to ease the shift as you would have on a triple to help with inner to middle "pickup" and derailment when doing back down. A single speed ring will have no shift aiding features at all. It probably wouldn't cause any issue with mounting if you chose the wrong type, assuming the bcd is correct, just shifting performance.

Also, it looks like the bike has a medium cage derailleur so you might get away without changing it.

[slowster]

How much time does your girlfriend spend riding on the 52t chainring? How much of that is in the 4 smallest sprockets rather than the bigger sprockets?

Fitting smaller chainrings is likely to give a much more useful range of gears than just changing the cassette for one with a wider ratio. Wide ratio cassettes with large gaps between gears are not likely to be a good choice for a road bike when riding at tempo/speed: many riders will find the gaps between gears too big.

If the chainset has a 110mm Bolt Circle Diameter (BCD), it should be possible to fit an inner chainring of 34 teeth. The front derailleur looks like it could cope with a larger difference than 10 teeth, so 46/34 or even 48/34 might be an option (or 46/36, 48/38 etc. etc.).

If you increase the tooth difference between chainrings from 10 teeth, the extra teeth will reduce the rear derailleur's capacity, but I doubt a 12 teeth difference would be a problem, and I suspect 14t would also be OK with the current cassette.

Your girlfriend should check what gear she spends most time using when cruising on the flat mid-ride. If she spends most time in 52 x 19 or 42 x 15, then 46/34 or 48/34 chainrings might be ideal, since 46 x 17 and 48 x 17 will give similar mid-70 inch gears while keeping the chain in the middle sprockets and optimising chainline. The link below gives a visual comparison of 52/42 with 46/34.

http://www.ritzelrechner.de/?GR=DERS&KB ... 0&UF2=2170

That is probaby a much more useful range of gears than would be provided with just a wider cassette. The link below compares 11-25 and 11-30 cassettes with the existing 52/42 chainrings. As the two links show, both options give roughly the same bottom gear.

http://www.ritzelrechner.de/?GR=DERS&KB ... 0&UF2=2170

[531colin]

From the photo it looks to me like the inner chainring teeth are a funny shape....like shark's teeth. If they are that shape then that chainring is worn out, and its quite likely the rest of the transmission is worn out as well.
Is it really a 42/52 chainset? World class professional cyclists use a 52/11 gear for racing......there is no way on earth that a recreational cyclist needs a gear like that....how often do you use yours?

An introduction to "Bolt Circle Diameter" BCD for short............ https://sheldonbrown.com/cribsheet-bcd.html
This is a 5 bolt chainset, measure how far apart adjacent bolts are to find the smallest (inner) chainring you can use. (My guess is its 110 BCD so you can use a 34 or sometimes 33 inner ring)

I would go lower on the big chainring as well, as you can't get a cassette without the (useless, in my opinion) 11 T sprocket. Say 46 T? or even 43T, if the F. mech. is happy working with 10T difference.

A triple will require new cranks, bottom bracket unit, and possibly F. mech. as well.

...............Beaten to it by "slowster"....as usual!

Here you go....33T 110 BCD inner...https://spacycles.co.uk/m8b0s210p3055/S ... -Chainring

The discussion on size of the big chainring (in my view) should centre on the question "does the rider NEED 52/11? If she NEEDS a gear that big, (and also a low gear) she will have to have a big gap between big and small chainrings, which means for a comfortable change in cadence you have to change both front and back at the same time, but in opposite directions, so go UP a chainring and DOWN a sprocket or two. If she doesn't need a huge 52/11 gear, she can have a smaller gap between chainrings, which is easier....assuming the F. mech. will handle it....this one already handles 42/52.

[rareposter]

From the photo it looks to me like the inner chainring teeth are a funny shape....like shark's teeth. If they are that shape then that chainring is worn out, and its quite likely the rest of the transmission is worn out as well.

That entire transmission is shot to pieces.
Going from the groupset, it's an ancient bike anyway - if you try and fit a new cassette, you'll need a new chain which will then refuse to work with that chainset cos it's so worn.

As often happens when you get to a situation like this on a bike of that vintage, it'll either need a complete new transmission which will probably require numerous other parts like a new front mech and BB to cope with the new chainset and a new rear mech to cope with a bigger cassette and maybe new shifters and the list goes on.

Or you need a new bike (secondhand?) which ultimately is probably the quicker and cheaper option.

[arupaka]

Thanks for your invaluable input!

How much time does your girlfriend spend riding on the 52t chainring? How much of that is in the 4 smallest sprockets rather than the bigger sprockets?

Your girlfriend should check what gear she spends most time using when cruising on the flat mid-ride. If she spends most time in 52 x 19 or 42 x 15, then 46/34 or 48/34 chainrings might be ideal, since 46 x 17 and 48 x 17 will give similar mid-70 inch gears while keeping the chain in the middle sprockets and optimising chainline. The link below gives a visual comparison of 52/42 with 46/34.

She bought the bicycle from a friend a few years ago, and at the time paid no attention to any detail at all(besides that the bike rides). We only use them for commuting, so we're really not technical about anything. I've told her many times it's better to get a new bike, but oh well.
From what I was told, 80% of riding time is around 42x11 (maybe one or two up in the cassette). 52 sprocket only for big downhills.

I'm thinking of going with alexnharvey's idea and do a 39T front (BCD is 130mm since adjacent bolts are around 76mm) and 11x32 rear.

Was thinking of something like this
https://www.tradeinn.com/bikeinn/en/shi ... 37705252/p
https://www.tradeinn.com/bikeinn/en/shi ... 38733598/p

You think this is ok?

From the photo it looks to me like the inner chainring teeth are a funny shape....like shark's teeth. If they are that shape then that chainring is worn out, and its quite likely the rest of the transmission is worn out as well.

You're quite right.. some of the teeth are sharky already, but most still seem "intact".

Edit: She's telling me her friend bought the bike circa 2015 (and gave her the receipt). So it's not that ancient! Though I admit it's a very strange and distasteful bicycle

[TheBomber]

These comments may not be greatly received:

From what we can see of that bike you are at the point of deciding whether pouring a not inconsiderable amount of money into it is the right thing to do. Apart from the gearing issue, how well does the bike suit her cycling needs generally? For example, is she happy cycling without mudguards (clearance looks limited)? Any desire to fit some wider tyres for non tarmaced surfaces (any bike that age with a 52/42 chainset is likely to be limited to around 28mm tyres). What about a luggage rack for trips away?

And the reason for saying this is I believe you are about to open a can of worms here. Are you sure the hubs are running well? What about the headset? Do the gears ‘index’ correctly (even with that loop of brake cable outer we can see). Once you start making any modifications all these things become more obvious.

I’ve said my bit now. I’m going to hide under the table from any incoming volleys.

[rareposter]

These comments may not be greatly received:

And the reason for saying this is I believe you are about to open a can of worms here. Are you sure the hubs are running well? What about the headset? Do the gears ‘index’ correctly (even with that loop of brake cable outer we can see). Once you start making any modifications all these things become more obvious.

I’ve said my bit now. I’m going to hide under the table from any incoming volleys.

I agree entirely.
Once you start "just changing this simple thing" on a worn out bike of that age, you'll very quickly find that everything else is wrecked as well.

It all (sort of) works because it's all worn together and because you don't know any better (which is fine, nothing wrong with that!).

But trying what on the face of it is a relatively simple "just fix this" will become a pit of "well now that needs changing as well" and "this new bit won't work with that old bit"...

[KM2]

Try a Spa cycles XD2 48/38/28 set £41, might even fit on the existing bracket. Lower the front mechanism and see if it copes. Might not be good for the 28 ring to small rear sprockets though.

[alexnharvey]

To echo what others have said, I think the optimum solution is to change to a smaller crankset overall, allowing you smaller chainrings than 38 and a large ring that gets more use than the 52 does.

Using a 38/39t is just the best you can do without getting new cranks.

And i also agree that you need to weigh up the cost of the whole upgrade and check the rest of the bike is working well enough, so no volleys fired here