A question about front derailleurs, and chainrings.

[cybertect]

AND to re-iterate / re-ask... Something like a 58 / 50 front chainring set up would be mechanically / theoretically viable?

And would need... 4ish extra links?

OK. 58T is a lot bigger than you were talking about earlier.

I'm assuming you actually bought the Focus Cayo, which happens to have a 50/34 front chainset.

The front derailleur on that is a Shimano 105, which has a maximum capacity of 16T with a 50-56T outer. You're likely going to have to replace that if you want to fit a 58T outer, otherwise you're stuck at 56T.

I don't know who makes an FD that will handle 58T.

Suppose you get a 56T front outer ring...

If you keep the 34T inner, then your range on the front is 56t - 34T => 22T

The rear cassette, as standard on the Cayo is 12-27T; a range of 15T.

That makes the total range on your system 22T + 15T: 37T.

The 5600-GS 105 rear mech (it looks like the long cage version in the photo on Wiggle) can handle up to 29T range. So that's out.

Keep the 50T as an inner, fit a 56T outer and your front range goes down to 6T, with a total range on the system of 21T, which the rear mech can deal with.

Using Sheldon Brown's Gear Calculator, with a standard 12-27 cassette on a 700 X 25 / 25-622 tyre and 170mm cranks, you go from

(50/34)

Bottom: 33.2 gear inches
Top: 109.9 gear inches

to

(56/50)

Bottom: 48.9 gear inches
Top: 123.1 gear inches

or possibly (if you can find a big enough front derailleur)

(58/50)

Bottom: 48.9
Top: 127.5

In top with the 58T/12T combination at 90 rpm cadence, you're doing 34.2mph.



Here's a thought...

Change the rear cassette to an 11-23T.

Change the front outer ring to 54T, the inner to 39T.

Total teeth range on the system: 15T + 12T = 27T

This can be handled by both your existing front and rear mech.

Plugging the numbers into Sheldon's calculator you get

Bottom: 49.0 gear inches
Top: 129.5 gear inches

Which is actually a higher top end, since that seems to be what you're after.

34.7 mph at 90 rpm

The bottom is near as damn-it what you get with your 58/50 setup.

 

[Herbsman.]

Are you riding a fixie with horizontal dropouts, Herbie?

Almost. Singlespeed.

 

[mattie]

OK. 58T is a lot bigger than you were talking about earlier.

I'm assuming you actually bought the Focus Cayo, which happens to have a 50/34 front chainset.

The front derailleur on that is a Shimano 105, which has a maximum capacity of 16T with a 50-56T outer. You're likely going to have to replace that if you want to fit a 58T outer, otherwise you're stuck at 56T.

I don't know who makes an FD that will handle 58T.

Suppose you get a 56T front outer ring...

If you keep the 34T inner, then your range on the front is 56t - 34T => 22T

The rear cassette, as standard on the Cayo is 12-27T; a range of 15T.

That makes the total range on your system 22T + 15T: 37T.

The 5600-GS 105 rear mech (it looks like the long cage version in the photo on Wiggle) can handle up to 29T range. So that's out.

Keep the 50T as an inner, fit a 56T outer and your front range goes down to 6T, with a total range on the system of 21T, which the rear mech can deal with.

Using Sheldon Brown's Gear Calculator, with a standard 12-27 cassette on a 700 X 25 / 25-622 tyre and 170mm cranks, you go from

(50/34)

Bottom: 33.2 gear inches
Top: 109.9 gear inches

to

(56/50)

Bottom: 48.9 gear inches
Top: 123.1 gear inches

or possibly (if you can find a big enough front derailleur)

(58/50)

Bottom: 48.9
Top: 127.5

In top with the 58T/12T combination at 90 rpm cadence, you're doing 34.2mph.



Here's a thought...

Change the rear cassette to an 11-23T.

Change the front outer ring to 54T, the inner to 39T.

Total teeth range on the system: 15T + 12T = 27T

This can be handled by both your existing front and rear mech.

Plugging the numbers into Sheldon's calculator you get

Bottom: 49.0 gear inches
Top: 129.5 gear inches

Which is actually a higher top end, since that seems to be what you're after.

34.7 mph at 90 rpm

The bottom is near as damn-it what you get with your 58/50 setup.

I've got a deore long cage rear mech going spare if that'd help....

I worry about quoadie though. I can only assume he's got silly low cadence.

 

[mrs quoad]

TY, cybertect

THIS:

(56/50)

Bottom: 48.9 gear inches
Top: 123.1 gear inches

looks perfect

Any guesstimate of how many links I'd have to add to the chain...?

 

[mrs quoad]

I worry about quoadie though. I can only assume he's got silly low cadence.

No comment

e2a: what's 'silly low'? And what's reasonable?

e2a2: just looked at my HR monitor for cadence data, and it hasn't recorded it since the 16th (earliest individual recorded exercise) I'm guessing the sensor got wonked :rerleyes:

e2a3: oh, ok, somewhere or other suggests 80-100 is beginning to get efficient. I've never gone above 119 on a bike that's recorded it, but IIRC I'm somewhere around the low- to mid-eighties. Erm. Mostly. Possibly. Will check!!!

e2a4: ahhhh, reverse-calculating my cadence from my avg fixie speed and gear inches suggests an avg cadence in the mid- to high-seventies

 

[cybertect]

Any guesstimate of how many links I'd have to add to the chain...?

http://www.parktool.com/repair/readhowto.asp?id=26

The maths bit at the bottom suggests 2 links.

e2a: another bit in the middle suggests

NOTE: Do not attempt to lengthen an old chain by adding new links.

i.e. buy a new chain and shorten it to length.

 

[weepiper]

TY

So do dotbike but I wasn't going to spoil the local bike shop vibe

I know my local friendly bike shop wouldn't have an account with any importers; the last time they sold new bikes was when I bought one. And the guarantee then cost them so much time and work that I think they decided to only sell second-hand from then on. They are not a glorious shop, but they are a lovely shop
And the other local somewhat-less-friendly bike shop adds at least 1/3 onto net prices

pffft, move to Edinburgh and I would be your local friendly shop am tiddly just now and will contribute more snese tomorrow when sober

 

[mrs quoad]

And that I'm unlikely to ever want anything lower than 50:27 (if I do, I'll shoot myself first).

I discovered Fish Hill

http://www.marts100.com/Photo_Pages/fish.htm

Fish Hill is the highest point of the northern Cotswolds

Whilst cycling to my aunt and uncle's.

I not only ended up changing down to the smaller of my two rings; I was on the biggest rear ring with the littlest front ring Spaddling away at about 30rpm going at, like, 4.3mph, for about half a fucking hour, with a hr of something twatty like 175 because I'd already nobbled myself earlier, when I thought I could take the bastard at full pelt

Fucking cotswold fucking wanky fucking wankery cotswolds.

*sulks*

 

[turing test]

I worry about quoadie though. I can only assume he's got silly low cadence.

I am thinking he averages about 45 RPM.

Reading this thread has given me Tendonitis.

 

[cybertect]

I discovered Fish Hill

Ouch!

This is why standard setups are standard

 

[mrs quoad]

Ouch!

This is why standard setups are standard

I think I've been thinking a *Cambridgeshire fens* setup was universalisable

 

[gentlegreen]

You should have come out with us cycling from Bristol to Chew Magna and back yesterday.
I came close to wishing I still had my 22 tooth granny gear.

My 48 tooth cog could do with a few extra teeth though ...

 

[mrs quoad]

Suppose you get a 56T front outer ring...

If you keep the 34T inner, then your range on the front is 56t - 34T => 22T

The rear cassette, as standard on the Cayo is 12-27T; a range of 15T.

That makes the total range on your system 22T + 15T: 37T.

The 5600-GS 105 rear mech (it looks like the long cage version in the photo on Wiggle) can handle up to 29T range. So that's out.

One query: if I understand what you're saying, then... wouldn't the set up as it comes be 50-34 = 16t, plus 15t (rear cassette) = 31t...?

Which, um, surely wouldn't be beyond the rear mech's mechanism? Not that I have any intention of going for 56:34, but it seemed worth asking / clarifying

 

[Herbsman.]

I am thinking he averages about 45 RPM.

That's a record!

I'l get my coat

 

[turing test]

I was waiting for that.

 

[mrs quoad]

That's a record!

I'l get my coat

I was waiting for that.

Pardon?

Is this some cultural reference that only people even older than me will get?

Are you two older than me?

I think you're older than me.

 

[gentlegreen]

Pardon?

Is this some cultural reference that only people even older than me will get?

Are you two older than me?

I think you're older than me.

I'm thinking Roy Castle RIP and the Mac Whirter twins - one of whom RIP also ...

 

[turing test]

Pardon?

Is this some cultural reference that only people even older than me will get?

Are you two older than me?

I am waiting for some old coddger to say anything less than 78 RPM's is just to slow.

 

[mrs quoad]

If I can't break 40mph with this, I will be pissed off.

 

[Herbsman.]

That's daft.

 

[Herbsman.]

You need a recumbent if you want to go really fast. Lower position = less aerodynamic resistance. Which is the main thing you're fighting against when you're trying to go really fast...

 

[Herbsman.]

Pardon?

Is this some cultural reference that only people even older than me will get?

Are you two older than me?

I think you're older than me.

You know what records are! And that some spin at 45 RPM

 

[mrs quoad]

You know what records are! And that some spin at 45 RPM

Ah!

You need a recumbent if you want to go really fast. Lower position = less aerodynamic resistance. Which is the main thing you're fighting against when you're trying to go really fast...

Yeah... I put the aero bars on it. Still failed, today. Blew up at about 38mph on hill 1, and forgot to shift to the 56t ring on the second decent hill! Also a filthy headwind today, which gives me hope

On the brighter side, avg cadence = 84. Which I BELIEVE isn't pure filth. And it's 10 higher than I thought it was

 

[mrs quoad]

Oh!

Also!

I used ALL MY GEARS for the first time today!!!!

For the first time!!! EVER

*with the possible exception of Fish Hill

 

[mrs quoad]

Bosh!

 

[gentlegreen]

 

[Herbsman.]

http://i127.photobucket.com/albums/p150/Quoad/Photo0395.jpg

Bosh!

Yeah thats easy to fake. You could have just taken the magnet off the wheel and attached it to a special large diameter drill bit (a sander type thing for example), and put this next to the sensor while the drill was rotating at high speed.

Prove you did 40 by doing it in a 30 zone where theres a speed camera, setting off said camera and and obtaining the photo from the police. Then posting the original photo to me 1st class recorded delivery, so I can scrutinise and inspect it.

 

[Boycey]

if it's wireless take it through one of those shoplifting sensor alarms whatsits

 

[Herbsman.]

wtf?

 

[Boycey]

when someone brings a bike through our doors with a wireless speedo it immediately reads 78mph