29er maths question

[gairym]

i've been thinking about whether or not to convert my new 29er to a 1x9 set-up and i stumbled upon some maths-based potential issues which i'm bringing up here to either be confirmed or poo-poo'd.

the idea is this.....

if i'm running a 1x9 set-up with, for example, a 32T chainring up front and a 9spd 12-36T cassette at the rear then i get a certain set of gear ratios.

but.....i'm forgetting to calculate the circumference of the wheel itself.

surely there'd be a noticeable difference in running this same gearing ratio on both a 26er and a 29er - no???

the logic seems to me to work: moving the same amount of weight (bike and rider) over different distances (the circumference of the wheel) using the same (for example 32T front and 16T rear = 2:1 ratio) would require increased energy input for a 29er.

sooo.....is this:

a) something that is common knowledge and i'm just catching up
b) nonsense and i'm overlooking something obvious
c) true and i'm some kind of geometrical genius

what do we think....?

[Bearbonesnorm]

Afternoon ... you are correct that there is a difference in gearing when using 26" and 29" wheels. If we were talking singlespeed (rather than 1x9) then the general thought is ... a difference of 2T. 32x16 with 26" would be roughly the same as 32x18 on a 29er.

I do notice the difference on a singlspeed but don't really notice it with gears. Your 36t rear should pretty much cover you, although it may now feel like a 34t rear

Leg better?

[gairym]

good good.

glad my logic hasn't failed me.

i think i'll try the set-up as it is on my 26" bike and then change things if i notice that it's too hard (when heavily laden on steep climbs).

and.....no, the knee's still giving me hassle.

i popped out on the 29er yesterday and i still can't put any power down without it twinging - it's crap!

i'm off back to France at the weekend and have a mini bike/bivi/bike trip planned and so we'll see how it holds up (as i'll be damned if i'm cancelling).

[Anthony]

Google 'gear inches'. There are more wheel sizes to get your head around than 29 & 26"

I was hoping there would be a decent Android app. but there isn't one yet.

[gairym]

holy crap!

some people (this sheldon brown fella for example) seem to have a lot of time on their hands.

will wade through all of it when i get a minute - good stuff.

thanks, gairy.

[Ian]

You've never heard of Sheldon Brown?

[Bearbonesnorm]

Ahh ... Sheldon Brown (RIP), a true eccentric of cycling. He must have been responsable for setting thousands of folk on the road the oddness

[gairym]

You've never heard of Sheldon Brown?

nope - but.....now that i think about it i'm sure i've come across his site before (when looking up obscure bike figures) but don't know anything about him.

seems to know his stuff!

[thomthumb]

i blame/ thank sheldon for setting me on to the one-speed path of the righteous. :D

i built up a SS mtb in my final year of school with only sheldons site as a reference. 6 years later i spent a good proportion of my final year at uni converting a 1989 raleigh into a fixed wheel with only sheldons site as a reference.

The cycling world is poorer without him.

[royAB]

Amen to that..