Cassette size question

[Fats25]

Apologies in advance for this question as I should be able to find it from other info on this forum (and others!) but I'm going round in circles to get a definitive answer.

My bike has Shimano 105 11-28T cassette. I'm picking up a Flux 2 trainer tomorrow that has a 105 11-32T cassette fitted.

Will my bike just fit on? Is any adjustment to chain or derailleur needed? I read somewhere about a "long" derailleur needed but think that's for a 34T.

Is there an idiots guide to basic maintenance and understanding of cycles so I don't have to ask such stupid questions ?

Crazy but I can maintain a motorbike but with cycles I struggle!

[Wilmslowboy]

The short answer is yes you will need a medium size derailleur (if you don't already have one), and a longer chain.


However, as it is only a trainer, what is to stop you just not using the top (32 ring on the cassette)

The real danger comes if you push up into the top cassette ring (32), when you are still in the big front chainring, this could cause the whole thing to jam up (if there is not enough slack in your chain).

[Fats25]

Thanks for response!

2 more stupid questions:-

1) When you say "avoid top - or 32" - this is the biggest cog (gear 1 and 12) or the smallest cog (gear 11 and 22) that I shouldn't use ?

2) how do I tell the size of the derailleur and if it is mid size or not?

I've also read about smallest to smallest or largest to largest chain length - but I need to read again to understand what that means and what chain length is on there already.

[Fats25]

I think I understand what you mean - gear 12 being most problematic as chain will be the most stretched on the 2 x biggest cogs (front and back).

[Wilmslowboy]

Fats25 said:

I think I understand what you mean - gear 12 being most problematic as chain will be the most stretched on the 2 x biggest cogs (front and back).

Yes happened to me, bought a new bike, fitted my 'old existing wheels' which had a 32 cassette, (new bike came with a 28, but mid-size derailleur, so thought all would be ok).

A lazy act on a short but very steep ramp, saw me go into the 'lowest' biggest ring at the back, while still in the big front chainring, immediately jammed everything up and ended up snapping the chain hanger.

[gazza285]

You could always swap the cassette for the same as your bike, cheaper than repairing the potential damage.

[Gareth79]

If you will be using the trainer in ERG mode all the time (ie. training programmes) then you may not ever need to change gear, just leave it in the middle of the cassette.

[alolympic]

gazza285 said:

You could always swap the cassette for the same as your bike, cheaper than repairing the potential damage.

I agree, best option.
On the trainer, you can go for a cheaper cassette 11-28. Your real world bike weight doesn’t matter In the virtual world.

[Fats25]

gazza285 said:

You could always swap the cassette for the same as your bike, cheaper than repairing the potential damage.

If I can find one - then that is what I will do. The market where I live is not the easiest to find what you want when you want!

Thanks

[stepaway]

Fats25 said:

gazza285 said:

You could always swap the cassette for the same as your bike, cheaper than repairing the potential damage.

If I can find one - then that is what I will do. The market where I live is not the easiest to find what you want when you want!

Thanks

Don’t forget to factor in a cassette removal socket tool and a chain whip (or similar) if swapping cassettes over if you haven’t already got these

[Fats25]

stepaway said:

Don’t forget to factor in a cassette removal socket tool and a chain whip (or similar) if swapping cassettes over if you haven’t already got these

I was watching some videos this morning for bike maintenance (found some guy on Global Cycling Network) with some very clear and concise instructions for basic bike setup. He had a chain whip. I realized at that point that I finally found out after 20+ years what one of the tools my Grandad left me when he passed away was to be used for.

I have just looked for it and cannot find it anywhere! Must have seen it 100 times in 20 years, and wondered what it was for, and now no idea where it is!

[LM240]

As mentioned, just change the cassette on the trainer. It’s a really easy job compared to the changes needed switching chain/hanger.

It just makes life simpler, especially if you change between road and turbo training.

You could always sell the bigger cassette to recoup the tool costs.

Once you’ve got the tools, they will be handy for future maintenance.

[Fats25]

I picked the trainer up tonight and have put the bike on the 11:32 cassette because I wanted to test (and am impatient!)

I didn't run it up to 12th gear - but did have it in 14th and checked the chain. I then clicked it by hand into 13th and was still ok. I reckon there is enough play in the chain to get to 12th though - but I didn't push it !

I will go out tomorrow to look for proper cassette but if not I think I may be ok anyway.

[Fats25]

Thought I would come back and update this thread in case anyone does a search in future. I have found out lots over the past couple of weeks that I never knew about bikes, and now have a setup I am happy with.

My original plan was to use my roadbike on the trainer, and just put it on and off as I needed to. Then I remembered that I am 1. Lazy and will never actually do that, and will effectively lose my bike for outside riding, 2. I have a spare bike that I bought cheap for visitors - is a little small - but with seat raised, and stem flipped it is ok for me.

Unfortunately the spare bike did not have a 11-32T either, it had a 11-28T too. To start with I had the spare bike on the trainer, and continued with the 11-32T, but it wasn't ideal. I couldn't use all the gears (as advised earlier in thread) and no matter what adjustments I made I could not get the indexing right across the range. I did however like the 32T more for Zwift challenges than the 28T. So (my man math) solution was to buy a new Mid size Derailleur for spare bike, another 11-32T cassette, and chain. Now I have the spare bike all set up and working much better.

Whilst I sourced the other bits I put the 28T from spare bike on the trainer, and used my road bike on the trainer. I found (maybe user error) that when switching it onto trainer, and off again, I had to re-index gears every time. So going back to my lazy comment earlier I am glad I have the setup I have now. The spare bike is still useable on road without having to remove cassette from trainer, and it is only used occassionally, so to reindex that infrequently is ok.

Some other things I have found that may be useful for others:-

1) There is a Global Cycling Network YouTube channel, which for a newbie like me has been invaluable. Highly recommended for advice on basic maintenance.

2) If buying second hand trainer (and useless/impatient like I am), be careful to get the setup right. I bought a second hand Flux 2, and on fitting my bikes it was obvious that the adapters for the bike to sit on was incorrect. The previous guy was using the 142 adapter, and my bike is a 130 (spare is 135). This is where I screwed up and it could have been catastrophic. Having never used a trainer before, and with very limited setup instructions available on-line, I switched the adapter on the non-drive side, and the bike fitted. I did about 45Km riding like that. When I came to switch the cassette from 32T to 28T I noticed that I should have also switched the drive side adapter too. It is not swappable without removing the cassette and not really visible either. Effectively I had all my weight on the quick release spindle, and not the adapter that should be fitted. A schoolboy error.

Other thing I have noticed (and now understand why so many of these come up for sale on 2nd hand market) these trainers are bloody hard work! Much harder than cycling on the road. I am using it though, and is much harder to come up with an excuse to not go cycling when it is all setup and ready to use.

Hope this is helpful!