Frog 78 - gears - would like to make them easier - how?

mikes-brother

Hello, my son has a Frog 78 (its the hybrid) and we would like to make the gears easier. Either get a smaller front chain ring or a larger maximum ring on the cassette.

This is for a cycling trip to mountainous areas of france this summer. Some long road climbs….

Has anyone done this with a Frog bike please?

& if so what’s the most straightforward way of doing this? & where can I buy the components please?

My local bike shop seems to think this will be “very complicated” … (really?)

Having looked at the other frog bikes my children have (the two sizes down in the same model) it seems like the components are identical.

Thanks ever so much

shirley_basso

Looks like it has 8 speed rear mech. Just work out how many teeth the largest sprocket at the back has, then buy another 8 speed cassette with more teeth in the biggest sprocket.

Google (Rutland Cycling) says it comes with a 32T at the rear and you can get one with 34 teeth here:

https://www.tredz.co.uk/.Shimano-CS-HG31-8-Speed-Cassette_92581.htm?sku=323322

From checking the spec of the rear mech online, I think it can handle up to 36T, but you may be able to go higher if you change the rear mech.

https://www.microshift.com/models/rd-m36s/

https://www.chainreactioncycles.com/microshift-mezzo-rd-m36-8-9-speed-rear-derailleur/rp-prod204944

Should all be very straight forward. Changing the rear mech a bit more involved, especially getting one which is compatible with the shifters, but not that tricky with some patience and youtube videos.

daniel_b

That's interesting - my newly gifted, but 2nd hand 73 has a Claris RD, and comes with an 11-32, but I would think that was the max for that specific derailleur, without an extender of some kind.

Depending on the age of your 78, it might not have the newer Microshift RD - the one I bought has the latest font, but still has the Claris RD on there.

The other option if it has a Claris RD on, and you think it can't take more than a 32, is to fit a derailleur extender like the below.
It simply bolts onto the rear hanger where the derailleur was fitted, and then the rear derailleur bolts onto the extender - thus moving it further away, and increasing capacity.
I have one I need to fit to my girlfriends bike, and will be keen to see how it works.
https://airbike.uk/products/derailleur-hanger-extender-goat-link-for-larger-cassettes-expander



Out of interest @mikes-brother , how old is your son?

My daughter is a tall 8, soon to be 9 year old, and the 73 fits her really well - the extra speed those bigger 26" wheels give her makes a massive difference.

mikes-brother

Thanks that's really helpful

My son is about to turn 11 and has had frog bikes of various sizes as he has grown. He is tall for his age and the bike fits him nicely

The bike is brand new and has the microshifter derailleur.

So the simplest seems to be to order the cassette with 36 teeth --- which one should I get? i.e. how do I know which ones may be compatible ?

daniel_b

It will be the same splines on the freehub as Shimano, so anything Shimano compatible will do the job.

Either get a Microshift version, or something like this Airbike one below will also do the job:
https://airbike.uk/products/8-speed-mtb-cassette-fits-shimano-sram-11-36t

Happy to be proved wrong, but I'm not convinced Shimano make an 8spd 11-36, so something like the one above, or SRAM will be compatible, or Miche likely as well - as long as it states compatible with Shimano freehubs.

EDIT: Doesn't appear Microshift or Miche make an 11-36 either in 8spd!

I think an 8 spd with that breadth of range is pretty niche, so the Airbike might be the only off the shelf option - it's definitely good value, and I've heard good things about the brand on here.

Munsford0

Bear in mind you will likely need a longer chain if going from a max 32 to a max 36t sprocket

theriddlr

Contact Spa Cycles for help. I have this double which is compatible from 7 speeds and up https://www.spacycles.co.uk/m8b0s109p3383/SPA-CYCLES-TD2-RD2-Super-Compact-Chainset-with-Zicral-Rings

Their single doesn't seem to go down lower than 38T but they might be able to source a chainring smaller than 32T for you. https://www.spacycles.co.uk/m8b0s109p4544/SPA-CYCLES-TD2-TA-Single-Chainset

mikes-brother

Would going from 32 to 34 make a noticeable difference? Seems like that would be the simplest approach- plus adding road tyres and removing the pannier rack and metal basket!

mikes-brother

I.e instead of trying to source a 36

vincesummerskRoxcBTr

Yep, the extra 2 teeth do make a difference.

daniel_b

mikes-brother said:

Would going from 32 to 34 make a noticeable difference? Seems like that would be the simplest approach- plus adding road tyres and removing the pannier rack and metal basket!

I'd either do that, or get the super cheap airbike cassette I posted above, and then even if you did need a new chain, they are comparatively pennies, and there is an argument on occasion that says when you change the chain you change the cassette anyway.
A risk with sticking with the original chain and a new cassette, is that they might not marry up as well, and you might get jumping gears.

I personally would not go to the expense of changing the front crankset, I also think that may put people off when you come to sell it on, being non original and all - although I suppose you could revert to the factory setup for sale, but then you are left with a spare crankset.

Assuming you already have the tools (?) I'd say for less than £25 that would make a big difference - well plus the tyres as well.
Out of interest, as the same tyre thought has occurred to me, do you already know what tyres you would be buying?
I think the 78 has the same 26" wheels as the 73.

mikes-brother

I ordered these tyres:

https://www.panaracer.co.uk/shop-c1/tyres-c34/urban-road-tyres-c10/panaracer-ribmo-wired-tyre-p24

mikes-brother

By the way, we took the new bike out for a ride last night and he was so much faster than on his previous frog 69 bike, especially on the hills. Burned me up big time.

So I will just upgrade the back cassette to 34

mikes-brother

Yes the Frog 78 has same wheels as the 72 and 69

mikes-brother

Hello @shirley_basso -- I installed the 11-34 cassette and it's great. Makes a big difference (I didn't realise that the 34 ring was 'mega' size. Thanks all for your help!

shirley_basso

No worries! Glad to be of use. 5 and a half thousand posts of drivel and glad one is finally helpful.

StillGoing

Late on this, but I just upgraded my daughter's Frog 70 by fitting Shimano Tiagra 4700 10 speed with a 11-34 cassette and upgraded the brakes to Tektra long drop side pull calipers. Kept the standard crankset and all works fine. She's now got a better bike with better brakes and easier shifting. Also means the Frog 70 will also take 700cc wheels with the side pull calipers, so with a longer stem will eventually last her another year or so.

StillGoing

Danyradar

Your daughter’s Frog 70 looks like a whole new bike now with better brakes and smoother shifting. The Shimano Tiagra 4700 10-speed setup and Tektra long-drop side-pull calipers are fantastic additions.