[xy9ine]

Fuuuuuuuu...that sucks more than a Dave Mathews concert. While highly unlikely, I hope you find the mutha fucka

sorry about the loss - just had my bike jacked a week ago (from inside my house, along with a bunch of other shit). fuckers must die.

random: i saw danny trejo (the above pictured badass) at the vancouver airport this weekend! was going to say hi, but momentarily blanked on his name. he had really nice shoes.

carry on.

 

[Sandwich]

o no, not the lahard?

 

[Metamorphic]

I rode my 650b/26 setup yesterday on my Spitfire. About 100yds from the end of a good long downhill run, I detonated and now my ass is swollen and turbo sore.

Was it because of the wheel size thing? Yes. Yes it was. Avoid at all costs all ye.

 

[xy9ine]

o no, not the lahard?

no, my bronson. wife's spitfire and the lahar were beside it, but were untouched.

bastard did find my greztky rookie card, and yoinked my macbook though.

 

[dump]

:/ house break-ins normal in vancouver?

 

[Udi]

Liteville (the Ibis of Germany = dentist bikes) offers this from factory:
http://www.liteville.de/t/25_579.html
They found a marketing name and most likely have trademarked it. If Udi is unlucky Specialized has all rights to this patented already and will soon sue him and Liteville.

Congratulations to Liteville / Syntace for failing at basic highschool level physics. I'm actually amazed that anyone could mess up this badly. I suppose this isn't new for the bike industry, but I expected better from Syntace.

For anyone interested in what's wrong here, two wheels hitting an identical bump doesn't magically reverse the direction of the vertical force vector. That's flat out incorrect.

 

[dump]

For anyone interested in what's wrong here, two wheels hitting an identical bump doesn't magically reverse the direction of the vertical force vector. That's flat out incorrect.

Not everyone building frames went to school where statics/dynamics was required... and some that did still can't get the forces diagram correct.

 

[xy9ine]

:/ house break-ins normal in vancouver?

depends where you are. property theft goes up the closer you get to the downtown east side (where the most of the crackheads congregate), but our neighborhood isn't bad. this is our first break in, and we've been here for 10 yrs.

 

[Udi]

Force is the vertical load (your butt + bike). Area is size of contact patch.
Nowhere in that equation is there anything about wheel diameter.

I understand F=PA, didn't really need to explain that.
My question was specifically with regards to traction and I did try to make that clear. I know you never implied that contact patch and traction are related 1:1 (maybe I could have worded that differently), I wasn't calling you out at all - you obviously know your stuff.

I do think it's potentially misleading (to those who aren't intimate with the terminology) to say the contact patch area doesn't vary and then to not discuss the traction differences in the same breath however - which is why I brought it up.

I'm fairly sure bigger wheels won't reduce traction, and as I suggested, I think in an offroad scenario with tread blocks, traction will likely increase - because tread blocks (embedded in some medium) can provide an axial reaction that isn't directly proportional to vertical load. If a larger diameter wheel is providing a *longer* contact patch, it's very likely making superior use of this axial support component compared to a shorter/wider one. Think about a railway track for a crude example - as the train goes around a bend, the rail provides a reaction that isn't dependent on the vertical load.

Classical friction says F = u*N, i.e. friction force = coefficient * normal force. Obviously tire load sensitivity complicates this, but essentially, on something like a road car - the traction is dependent on the normal force (i.e. vertical load on the tire). You understand this obviously, just re-stating.

My point is that offroad this isn't the case, especially where you have a tread block that is penetrating into the ground - something like a motocross bike or mountain bike is a good example. In this case I think you quickly hit a peak (axial/cornering) friction value with a wide+short contact patch, since there's a limited number of blocks across the tread (that can be 'underground'), whereas I think you can make better use of the same load with a longer contact patch - even if it is narrower - since there are more blocks lengthways.

Of course it'll vary with the surface, block size, etc, but I think on average the net result will be an improvement - even if small. Open to correction though, I thought it'd be cool to think about since it's hard to measure. Also, I'm still on 26" all round so I was quietly hoping to be shut down on the traction thing.

 

[no skid marks]

Back in the day when I tried 26 front 24 rear, it seemed the back got unweighted easy as if the axle was trying to get to the same height as the fronts. I'm sure there's no or little truth to this but it's what it felt like. I think it was on a ATX DH. I didn't give it much thought or try to figure out other causes, I just switched to same wheel sizes. Maybe the smaller wheel made it bounce more off stuff.........

On the contact patch thing, all things being equal in tyre specs(casing, width etc) and same pressure. Contact patch would be the same just a different shape. Fairly moot point though, as rim width, tyre structure, width and design and pressures would have similar effect anyway.

 

[kidwoo]

Back in the day when I tried 26 front 24 rear, it seemed the back got unweighted easy as if the axle was trying to get to the same height as the fronts.

Even 24s long with all their heart to be 26s.

 

[WestCoastHucker]

...and got a 0.9" increase in OD from 26" to 27.5" with the same tire...

are you sure it was the same tire? i can't get a 26 tire to fit on a 27.5, but i probably just need bigger levers...