Even Orange are at it now...

bluechair84

Gazlar wrote:

Having tried out both 650s and 29ers I find that being a tall, twitchy kind of rider that is quite high up in posture when he rides, they feel a lot less stable than a 26 inch bike.

Really? I'd have thought it would be the other way around! Any ideas why this might be the case?

pesky_jones

bluechair84 wrote:

Gazlar wrote:

Having tried out both 650s and 29ers I find that being a tall, twitchy kind of rider that is quite high up in posture when he rides, they feel a lot less stable than a 26 inch bike.

Really? I'd have thought it would be the other way around! Any ideas why this might be the case?

Lower centre of gravity on a 26"

The Rookie

True, but by all of half an inch at most, for 13kg (est) of bike under a 70-80kg rider at the same height.....sounds psychological to me!

pesky_jones

excuse the poor quick drawing on paint, I dont even know if it's understandable.



The two lines either side of each rider (the range) shows the amount your centre of gravity (COG) can travel before you fall.

It is easier for the higher COG to fall out of its range as you are pivoting around the point of contact with your front wheel and the ground.

29" is exagerated, COGs are in wrong place, but its schematic

bluechair84

Pesky Jones wrote:

bluechair84 wrote:

Gazlar wrote:

Having tried out both 650s and 29ers I find that being a tall, twitchy kind of rider that is quite high up in posture when he rides, they feel a lot less stable than a 26 inch bike.

Really? I'd have thought it would be the other way around! Any ideas why this might be the case?

Lower centre of gravity on a 26"

Marginally... 29ers do not have to have a higher BB so it's only the little bit of extra weight at the top of the wheel

bluechair84

ooh, can't see the drawing - work's servers. I'll have a look tonight.

Thewaylander

BB has little to do with centre of gravity of a bike is though it helps..

More mass is higher up on the 29" generally.

I notice it on many 26" which is why the bikes i tend to like have the rear shock with a low mounting keeping the wieght lower.

Gazlar

I think I pronounce it to by being quite long in the body and when I ride I look like a vicar riding into town. It may well be psychological or it may be just that familiarity and feel and with more riding and a better setup a larger wheel bike would feel great, I just like having the choice rather than being told this or that is better, I'd rather feel for what I prefer

Chunkers1980

The BB doesn't have to be higher. The only things that are certainly higher are the axels, everything else is design.

bluechair84

Chunkers1980 wrote:

The BB doesn't have to be higher. The only things that are certainly higher are the axels, everything else is design.

This. You will have to have very slightly raised stays too, but I can't see see the CoG raising that much. But, I might be wrong here, my first argument was that people are very susceptible to slight changes in their bikes. Maybe this slight change is very noticeable. As Gazlar says, it's all about feel.

Thewaylander

I think in real terms rear shock positioning would have a greater effect on cog. But like for like on frame design a 29er will be higher I reckon.

thekickingmule

I've just been curious about the measurements of the wheels as to what we're all talking about.
If this is wrong, feel free to correct it, if it's irrelevant, feel free to ignore it.

Sizes are approx.

26" wheel = 66cm Circumference, 21cm Diameter
600B wheel = 68.5cm Circumference, 21.8cm Diameter
29" wheel = 73cm Circumference, 23cm Diameter

The Diameter will give you a rough idea of axel height, if I think I'm right. That said, I am absolutely useless at maths (honestly!) so mathematicians feel free to correct them.

angry_bird

thekickingmule wrote:

I've just been curious about the measurements of the wheels as to what we're all talking about.
If this is wrong, feel free to correct it, if it's irrelevant, feel free to ignore it.

Sizes are approx.

26" wheel = 66cm Circumference, 21cm Diameter
600B wheel = 68.5cm Circumference, 21.8cm Diameter
29" wheel = 73cm Circumference, 23cm Diameter

The Diameter will give you a rough idea of axel height, if I think I'm right. That said, I am absolutely useless at maths (honestly!) so mathematicians feel free to correct them.

Those numbers don't seem right to me at all I'm afraid. Think you're getting confused somewhere. Or I'm confused. Or… we're both confused.

thekickingmule

Haha possibly. I just used an online calculator thing and put in the circumference, as my maths is that bad, I rely on interweb people to do it for me.

I think it would be interesting to see what we're talking about in terms of actual sizes

EDIT: It may be the middle, 650B one that's wrong. I don't know what its circumference is :?

supersonic

The diameter is the first figure! Circumferance is that times pi

But is a much simpler way of comparing relative hub height. Take tyres out of the equation - assume they are all the same height. Then the relative hub heights is simply the difference in rim radius.

26er = 559mm diameter, radius = 279.5mm
650B = 584mm diameter, radius = 292mm
700c (29er) = 622mm diameter, radius = 311mm

So compared to a 26er, the 650B hub height is 12.5mm higher, the 29er is 31.5mm higher.

thekickingmule

:oops: Told you I was rubbish at maths!

Cheers for that though, to see we're only talking 3cm bewteen the outer extremes is interesting!