Wheel theory

[Insaneclimber]

Over the last year i have been trying to build the lightest wheels i can in the belief that light is more effeciant. But reciently i saw on this forum that one member believed his deep v carbon fiber rims were faster. After looking at several brands of carbon rim i know that a 330 gram scandinium rim is about as light as you can get. Now im wondering if my weight fascination is wrong.
So which is more efficient. a 600 g wheel with alloy rim or a deep v carbon 700g wheel.

PS im talking mtb wheels here

 

[artemidorus]

Over the last year i have been trying to build the lightest wheels i can in the belief that light is more effeciant. But reciently i saw on this forum that one member believed his deep v carbon fiber rims were faster. After looking at several brands of carbon rim i know that a 330 gram scandinium rim is about as light as you can get. Now im wondering if my weight fascination is wrong.
So which is more efficient. a 600 g wheel with alloy rim or a deep v carbon 700g wheel.

PS im talking mtb wheels here

With your great fat tyre on it, I'll bet that a deep profile rim makes no difference at all. I'd go for light weight.

 

[bobbyOCR]

mtb? I value stiffness in a mtb wheel. Makes the handling more predictable and hopping obstacles + technical descents easier too.

 

[artemidorus]

mtb? I value stiffness in a mtb wheel. Makes the handling more predictable and hopping obstacles + technical descents easier too.

MTB wheels are intrinsically much stiffer than a road wheel. Can't say i've ever come across a noticeably floppy one. And the fat tyres probably make them all a lot less stiff, effectively, as the contact patch can drift about with the tyre.

 

[bobbyOCR]

MTB wheels are intrinsically much stiffer than a road wheel. Can't say i've ever come across a noticeably floppy one. And the fat tyres probably make them all a lot less stiff, effectively, as the contact patch can drift about with the tyre.

The difference between a titanium spoked pair of cane-creek mtb wheels and 32 spoke mavic to high-flange disc wheels is pretty big. Caneçreeks are fast but the titanium spokes don't suit my riding style. Butter smooth XC racers (of which I know one.....the owner of these wheels) could handle the well though.

 

[Insaneclimber]

All very interesting but i still don't get why a heavier deep v carbon rim is considered faster, maby its just more aero? or is it actually benifical to have more weight on the outside of the wheel?

And my big fat mtb tyres only weigh 320g and i run 60psi, so that dont make as much differance as you think?

 

[JohnO]

Faster for what?

For climbing... aero doesn't really matter, unless you are superman. You aren't going that fast.

Downhill or even on the flats is another matter. I definitely noticed a difference in descending speed when going from a box rim to a 58mm Zipp rim.

If you watch the Alpe d'Huez TT of a couple of years ago, you can see that no one was riding deep rim wheels, as that stage was all climbing.

 

[artemidorus]

All very interesting but i still don't get why a heavier deep v carbon rim is considered faster, maby its just more aero? or is it actually benifical to have more weight on the outside of the wheel?

And my big fat mtb tyres only weigh 320g and i run 60psi, so that dont make as much differance as you think?

A deep V rim has only been shown to be aerodynamic with a 23mm tyre, or smaller, on it. You're talking >40mm, I imagine, with knobs on. No evidence that deep v helps with those, and intuitively it seems unlikely. In addition, you need to be going >35km/h to notice real benefits with slim tyres and deep v, so much of an XC racer's time would be spent at too low a speed, even if it worked with fat tyres.
The weight distribution of a wheel has been shown to be pretty irrelevant. Wheel weight is mostly equivalent to weight anywhere else on the bike.

 

[Insaneclimber]

A deep V rim has only been shown to be aerodynamic with a 23mm tyre, or smaller, on it. You're talking >40mm, I imagine, with knobs on. No evidence that deep v helps with those, and intuitively it seems unlikely. In addition, you need to be going >35km/h to notice real benefits with slim tyres and deep v, so much of an XC racer's time would be spent at too low a speed, even if it worked with fat tyres.
The weight distribution of a wheel has been shown to be pretty irrelevant. Wheel weight is mostly equivalent to weight anywhere else on the bike.

That makes sense, good to see someone knows what there talking about
So ill stick with my current theory and get back to finding some sub 100g hubs, someone mentioned Ti spokes? is that a good idea or is it just dumb like the Ti chain?

 

[alienator]

That makes sense, good to see someone knows what there talking about
So ill stick with my current theory and get back to finding some sub 100g hubs, someone mentioned Ti spokes? is that a good idea or is it just dumb like the Ti chain?

Well, a lot of people will trot out some myth and say Ti spokes are a bad idea; however, there are more than a few builders that have been using Pillar Ti spokes with great success. The problem, however, is the cost: Ti spokes be expensive.

 

[bobbyOCR]

Ti spokes a light, very expensive and tend to build a flexier wheel. Stick with good stainless steel, especially for a handbuilt mtb wheel. The Cane Creek Aros Ti use a massive hub flangeto compensate for the radial load placed by the disc and drive IIRC. I'll assume this has something to do with helping the Ti spokes properly function and survive under massive loading present with disc brakes and accelerations. If you want ti spokes, go for those wheels, but I say stick with stainless steel. The amount of material in those CC hubs makes the wheels weigh more than a good pair of handbuilts anyway.

 

[alienator]

Ti spokes a light, very expensive and tend to build a flexier wheel. Stick with good stainless steel, especially for a handbuilt mtb wheel. The Cane Creek Aros Ti use a massive hub flangeto compensate for the radial load placed by the disc and drive IIRC. I'll assume this has something to do with helping the Ti spokes properly function and survive under massive loading present with disc brakes and accelerations. If you want ti spokes, go for those wheels, but I say stick with stainless steel. The amount of material in those CC hubs makes the wheels weigh more than a good pair of handbuilts anyway.

FWIW, I have lateral stiffness test results, here on my computer for a wheelset built with Reynolds Stratus DV-UL rims, Pillar Ti spokes, a Tune Mag190 hub in back and an M5 SP hub in front (16f, 20r) compared to a DT Swiss 1450 wheelset. The comparison was done on the same test apparatus, and the results are as follows:

DT Swiss rear:
Pattern = 28 2X
Weight = 832g
Average deflection* = 3.6mm @ 25#

Custom Reynolds rear with Tune Mag190 hub:
Pattern = 20 1X EO drive/2X non-drive
Weight = 608g
Average deflection = 3.45mm @ 25#

DT Swiss front:
Pattern = 28 radial
Weight = 665g
Average deflection = 2.55mm @ 25#

Custom Reynolds front with M5 SP hub
Pattern = 16 radial SP
Weight = 446g
Average deflection = 3.07mm @ 25#

*measured at 4 points on the rim, at the center of the brake, on both sides of the wheel, twice, then averaged.

Note that the DT front wins in lateral stiffness as a result of having 28 spokes vs. the 16 on the Reynolds.

Soooooooooo......these Pillar Ti spokes ain't the same one your Grandma built wheels with. While the above test isn't an apples to apples comparison, necessarily, it does show that stiff wheels can certainly be built with the Ti spokes.

 

[bobbyOCR]

Thanks. That is pretty interesting. For mtb though, I would stick with stainless steel.

 

[alienator]

Thanks. That is pretty interesting. For mtb though, I would stick with stainless steel.

Mtb? What the hell is that? You mean those bikes that I see folks riding between classes and to grocery stores?

 

[bobbyOCR]

Mtb? What the hell is that? You mean those bikes that I see folks riding between classes and to grocery stores?

exactly.

 

[Insaneclimber]

Mtb? What the hell is that? You mean those bikes that I see folks riding between classes and to grocery stores?

Thats just low, you dont see me baggin out you leg shaving lycra wearing soft cocks do you now.
Any how i thought id mention that although rear wheel regidity is critical for effeciancy, a soft front wheel handles the hits better, so maby a Ti wheel would be suitable for the front, oh and my 10.1 kg xc bike don't have disc brakes, there too heavy!

 

[bobbyOCR]

suspension handles hits.

I will play advocate for roadies here. I recently came off at 40km/h on the road. You slide on dirt, smooth asphalt perfectly shears off skin (and whats under it). If you know how to come off a bike (very handy skill, though not easyy to practice) it hurts much less (usually) on the dirt.

http://weightweenies.starbike.com/phpBB2/viewtopic.php?t=27336&postdays=0&postorder=asc&start=15

This thread also explains some of the mysteries of Ti spokes (Pillar Ti, possibly a NiTi alloy)

 

[Insaneclimber]

suspension handles hits.

I will play advocate for roadies here. I recently came off at 40km/h on the road. You slide on dirt, smooth asphalt perfectly shears off skin (and whats under it). If you know how to come off a bike (very handy skill, though not easyy to practice) it hurts much less (usually) on the dirt.

http://weightweenies.starbike.com/phpBB2/viewtopic.php?t=27336&postdays=0&postorder=asc&start=15

This thread also explains some of the mysteries of Ti spokes (Pillar Ti, possibly a NiTi alloy)

Your forgetting about trees and rocks, and im forgetting i was a roadie for 10 years and i still wear lycra.

 

[alienator]

Your forgetting about trees and rocks, and im forgetting i was a roadie for 10 years and i still wear lycra.

See, here in Arizona, we don't just come off and slide or tumble down the road. No, we got more than enough places where coming off the bike means coming to a rest in the cactus backstop, while the ****** off stinging and biting reptile, arachnid, and insect populations look on.

Besides, it's the mtbers forgetting about the trees and rocks........"Ted.....DUCK!!!"

 

[Insaneclimber]

See, here in Arizona, we don't just come off and slide or tumble down the road. No, we got more than enough places where coming off the bike means coming to a rest in the cactus backstop, while the ****** off stinging and biting reptile, arachnid, and insect populations look on.

Besides, it's the mtbers forgetting about the trees and rocks........"Ted.....DUCK!!!"

Heres a news story from my home town, theres nothing safe about mtb.

Nelson mountainbiker Jared Brown is facing an uncertain future after breaking his neck in a high-speed crash near Blenheim.

Jared was on Wednesday waiting for surgery in Burwood Hospital in Christchurch after crashing in a Marlborough Mountainbike Club downhill race at Strachan Peak north of Blenheim on Sunday. The 16-year-old Waimea College student was riding at 60kmh when he hit a rut and flew 20m over the handlebars, landing heavily on his head.