[ÆX]

I found i really like the rolling of the 29's like most.
So I am going to to a DH 26 vs 29 test to show people.

I will take 50 3' length 2x4 pieces of wood and run over
them down a hill at 20 mpg 10 times to get an average.
then do it on 26's.

same 30 PSI in the same 2.1 motoraptor tires.
same rider
no wind

so say a 29's time would be 45 secs.
and a 26's 60 secs.

that would mean they roll over crap 25% faster.

I would guess it is going to be more like 8% but
that would be fine.

I will put my MPH computer on so I can record top speed.

I got my 26 motoraptors in.
I have time this weekend so I will have some results soon.

alex

 

[N8 v2.0]

Great idea for a test Alex!

 

[bikenweed]

so say a 29's time would be 60 secs.
and a 26's 45 secs.

You mean a 29's time would be 45 secs?

Makes sense to me. But they aren't faster if they've got flat tires and taco'ed rims...

I'd love a 6" travel, 29" wheel bike with pure DH geometry- low, low BB, super slack head tube and seat tube, and a loooooong wheelbase. I think it could be quite competitive against all the 26" bikes these days, especially on a faster course.

 

[BikeGeek]

I seem to remember a lot of DH guys riding a 24" in the back with a 26" up front. Have your tried the 26/29 combo yet?

 

[ÆX]

You mean a 29's time would be 45 secs?

Makes sense to me. But they aren't faster if they've got flat tires and taco'ed rims...

I'd love a 6" travel, 29" wheel bike with pure DH geometry- low, low BB, super slack head tube and seat tube, and a loooooong wheelbase. I think it could be quite competitive against all the 26" bikes these days, especially on a faster course.

oops, EDIT:

yeah, i don't like small tire choices, flats, week wheels.

but it has to start somtime. that is what i am trying to

do is movethis along so next year we will have tires, forks,
and rims/120 front hubs to use if we want.

 

[MMcG]

Alex - what about front end height on a 29" wheeled DH bike - would it be a little too high - or would that be balanced out because the 29" wheel would allow a user to run less travel up fron than current 7 and 8" travel Dual Crown DH forks?

 

[Beast]

heh, alex - i think your front rotor is on backwards

 

[dcamp29]

this sounds like a great experiment, but I think you need to take into account that a 29er will have a longer contact patch with the ground, giving them-in theory- more rolling resistance for a similar 2.1" tire. This is why everyone at our shop in littleton runs 1.9s on their 29ers-they hook up the same as a normal 26" 2.1.

maybe do the experiment with and without the bumps. then compare results.

 

[Pau11y]

I'd bet a 29er would be a good candidate for 4x wheel lacing in DH applications. A 36h 4x ought to make it pretty strong...

 

[Cloxxki]

this sounds like a great experiment, but I think you need to take into account that a 29er will have a longer contact patch with the ground, giving them-in theory- more rolling resistance for a similar 2.1" tire. This is why everyone at our shop in littleton runs 1.9s on their 29ers-they hook up the same as a normal 26" 2.1.

maybe do the experiment with and without the bumps. then compare results.

In theory, but only a wrong theory, no offence
What're confused with is the extra grip and traction a longer contact patch will give you. We're not pedaling our bikes spinning out all the time (wouldn't that be fun, and horror for the trails).
The way the contact patch changes shape between 12" scooter wheels and 29" wheels of the same width, per meter travelled, less rubber in the tire is deformed, and at much shallower angles.
The part of the tire that touches the ground is actually hardly generating resistance, it's the parts just hitting the ground, and just leaving the ground, where the rubber deforms.
I once rode a 36" wheeled beach cruiser over an exhibition floor, and although it obviously was a big fat pig, it rolled like nothing else. Imagine perfect rail track of endlessly hard steel and a perfectly round wheel of the same steel, and frictionless bearings (magnetic power or something). It was like that, total silence and no forward energy taken from the bike by the tires. Larger wheels just roll faster, it's why BMX is for tricks, smooth tracks and curved ramps, and 26" and 29" for more XC and DH type stuff.

 

[Cash-Money]

are you using your inedible for this test? i think it would work better on a rigid bike, so the suspention doesn't affect the test.

 

[Dirtbike]

A couple points:

You need a control; do runs without bumps.

Do more trials for a more accurate conclusion.

30 psi in a 29" tire will produce different rolling resistance than 30 psi in a 26 inch tire because the 29er has a greater volume.

Sounds like a cool experiment..

 

[ÆX]

this sounds like a great experiment, but I think you need to take into account that a 29er will have a longer contact patch with the ground, giving them-in theory- more rolling resistance for a similar 2.1" tire. This is why everyone at our shop in littleton runs 1.9s on their 29ers-they hook up the same as a normal 26" 2.1.

maybe do the experiment with and without the bumps. then compare results.

this is not a rolling ress test. that has been done. see MBA last month.
I know i hate reading it too.


this test is for roll over. the plow over where 29's shine. What i am looking for is a pecentage to give people.

the test will be at diff speeds, might do some with 4x6's too.

 

[ÆX]

are you using your inedible for this test? i think it would work better on a rigid bike, so the suspention doesn't affect the test.

yes i am using my inedible.
i think if the sus travel and setting don't change it should be fine for
a side by side.

certainlly you might be able ot TUNE you setting to work beter for a
26, but not much.

rigid might be better but that is not real world use.
I am trying to replicate a ruff part of a dh track where time
would be made on a 29 and test how well they actually do.

 

[Cloxxki]

I think it's fairest to do all runs with the weight on the seat, just rolling along passively. The 26" wheels might like faster compression/rebound for the same obstacle. A 29" wheels takes longer (inches along the trail) from start to ending of an obstacle. Lower peak impact. Not sure what type of setting might favor each wheel. Ideally you'd find the ideal setting for each, and compare best performances.
At least you'll get super fit from riding a DH bike up a hill 100x times a day.

 

[Zark]

Interesting idea.
Alex I know you are very into this 29'er DH thing.
I got some questions for ya.
I rolling over crap really an issue considering the suspension around these days? I
I'm thinking cornering and acceleration out of corners are more essential to improving times in the DH world. How about some sort of test for 29 vs 26 in these areas? I know there are a ton more variables which makes it harder to quantify, but it seems like another important aspect of your endeavors.

 

[bjanga]

If a 29" needs less suspension because it eats bumps, does that mean it can power out of corners better?

 

[Cloxxki]

From analysing the action at last year's Willing world Cup Dh, I think acceleration is not worth worrying about, especially not on bikes so bulky already. What I saw was a course with sketchy landings, braking into low-grip corners, picking lines through rock gardens, and trying not to jsut lose the bike on a slippery section. Then near the end the course crossed the 4X track, and there were high-speed gravel corners and long jumps. All IMO would favor larger wheels, the steepness of the course seemed to take take of most of the acceleration involved. Then, I'm not a DH racer by far.

If long travel makes for heavier bikes that accelerate slower or less efficiently, then 29" might indeed have things to offer. Less travel required to clean the same course safely, a lighter more manouevrable bike, that is faster everywhere the brakes are not applied. Plus it should allow to brake later and less. I suppose the above goes for 26" vs 24" as well?

I have the impression that if wheels hold up and suspension design is sound, anything is possible for DH 29", even World Cup wins.

In a field of just 24" DH bikes, how would a single podium contender be to do on a 26" bike?

 

[ÆX]

Interesting idea.
Alex I know you are very into this 29'er DH thing.
I got some questions for ya.
I rolling over crap really an issue considering the suspension around these days? I
I'm thinking cornering and acceleration out of corners are more essential to improving times in the DH world. How about some sort of test for 29 vs 26 in these areas? I know there are a ton more variables which makes it harder to quantify, but it seems like another important aspect of your endeavors.

maybe for the very top pros it is. b/c they are allredy at the max
over the ruff stuff, well, with 26'' wheels they are.

as for the average JOE they are hesitant in the ruff and they could
have more confidence and make faster times if they went faster over
the ruff.

they will also provide more cornering traction, well as soon as there is
a tire made spec for dh.

after a do the rollover test i might work on some sort of cornering G
test. have to think about it.

 

[Sorgie]

Did you see the 26er vs. 29er comparison in this months MBA with the identically equipped Gary Fisher Paragons? The 29er won the rollover test, but pretty much lost everything else. I'm interested to see if your results reflect what they came up with. I've toyed with the idea of a Monocog 29er, but I'm not convinced it would be that much fun on the trails I ride.

 

[ÆX]

Did you see the 26er vs. 29er comparison in this months MBA with the identically equipped Gary Fisher Paragons? The 29er won the rollover test, but pretty much lost everything else. I'm interested to see if your results reflect what they came up with. I've toyed with the idea of a Monocog 29er, but I'm not convinced it would be that much fun on the trails I ride.

there rollover test was down a dirt path.
not slamming it to thing you would on a DH run.
they didn't do it right IMO.

 

[Cloxxki]

To test cornering G's, you can simply go to a smooth field (perhaps even an especially rough one too). Draw a perfect circle, perhaps 6-10yard radius. Mark it with rocks or wood. Ride around, and either have laptimes registered, or set the computer really precisely and try to get a max speed, without letting go of the inside of that circle.
Riding in both direction should be good to improive cornering over your "bad" side.
I did this sort of test over grass with 3" of snow. Racing my buddy around a labyrinth in a park. Purely a grip game, not fitness. You get to try things with weight distribution too, speedometer tells you.

In a rough field, this test could be a combination of rollingspeed and cornering traction. It will be fun to compete with other riders, swapping bikes. If the seat height suis, we can all ride every bike through an eternal corner at out maximum, right? Having a single electronic eye to register each completed lap would be good. Note with each best lap of an attempt which rider on which bike, possibly even with which tire pressure. Should all be very interesting, with a fun competition factor. With a DH bike, obviously fork/damper setting are going to matter too.

 

[ÆX]

got the wood cut. i have 40 2x4/4x4's
I did various lengths of scrap i had. around 16''.
put big nail thru them to afix to the dirt road.

found a downhill paved to dirt for the test.

I don't know if i will get to it b/f the weekdend
but maybe.

 

[Cloxxki]

Exciting! Wish I were local so I could help out setting up for the test. I hope others will take my place

 

[Tame Ape]

I think a good test would be to see if the 29er wheel is safer for localized wildlife.

Is a squirrel safer running into a 29er wheel or a 26" wheel? I actually think that he would be better off colliding with a 26" and that a 29er might just break the laws of physics and send the little bastard back in time. It is just a theory...

 

[Cloxxki]

2 weekend later
Any news yet? Need some hands to plant those 2x4's?

 

[ÆX]

lol,

till wed i am working on our amazing race submission video.

learning adobe elements and all the pc upgrade crap to get it

to run/render fast.

end of the week maybe I'll have time.

http://bcdracing.com/pics/can.mpg

 

[Rye_Bread]

results?

 

[ÆX]

gheeesh, com on guys.
we all know they roll great!
we don't need a test. lol









































.
well i am just slacking