Bora WTO

[HiFi]

Both links discuss why 28mm tyres are faster in spite of their larger frontal area. (The 1st link teases out that besides the tyre carcass rolling resistance reported on in drum roller tests, lower pressure 28s deform better over the irregular surface of tarmac, and this turns out to be a bigger reduction of overall resistance than people realised). So the tyres are good. But the question here is what width of rim do we need. Wheel design isn't my day job either, but let's just think about it. 105% of a 20mm tyre means 0.5mm extra rim sticking out each side, 105% of a 28mm tyre would give 0.7mm extra each side. With the more pronounced curvature of 20mm tyre sidewalls the airflow detaches sooner, but a rim that introduces a 0.5mm step recaptures it, so it flows smoothly down the rim wall. With the more relaxed curvature of the 28mm sidewall the airflow stays attached longer, doesn't get deflected as far, and the rim step needed to recapture the airflow probably needs to be smaller. CFD would tell us, but let's just guess it needs a 0.2mm step. But the 105 rule-of-thumb says we want 0.7mm there, ie an even bigger rather than a smaller step. If we simply stick to the rule-of-thumb created five-tyre-generations-ago doesn't this bigger step now stick out too far? Is it now a cause of turbulence rather than something that reduces it? My presumption would be that each generation of tyre needs a different rule-of-thumb rather than one rule-of-thumb for every tyre generation.

[ichobi]

The new black inc 48/58 comes with 23mm inside with and 29mm outside. They seem to have done rather extensive cfd and windtunnel testing in conjunction with the new Factor Ostro. I don’t think that they won’t be aero with a 28mm tires no?

[HiFi]

Well you'd hope so. Everyone does extensive CFD testing. Maybe Black reveal just how far down the list of priorities the rim/tyre width ratio has fallen for wheel designers for this tyre generation, as they don't even mention it or the rim width anywhere in their launch book, instead: "We increased the leading-edge radius, creating a true airfoil shape that is optimized for 28mm tires. The increased radius creates a more gradual rate of curvature change, promoting flow attachment at larger yaw angles. In addition, the rounder profile and more-gradual change in curvature means that the aerodynamic stall onset is gentler". We can see this shift in focus in all manufacturers new wheel designs.

[ichobi]

Part of the reason Roval only claims their wheels are fastest with 26mm tires is probably because they don’t make fast tires bigger than the 26mm. The one size up - the sworks turbo cotton 28mm is designated hell of the north version with extra puncture protection compared to
The standard TC, which their sponsored team never use on normal road race except the classics. Would be weird for them to champion something bigger if they don’t make and sell the thing.

Aside from Roval and a few few brands i don’t really see many brands put emphasis on 105 rule at all (not that the rule is wrong or outdated) but it seems interesting. Perhaps it’s too limited to prescribed exact tire sizes for customers? Even with Roval their reasoning for massive outer rim width is not particularly for the 105 rules but rather their philosophy on crosswind stability.

[Junior Varsity]

Part of the reason Roval only claims their wheels are fastest with 26mm tires is probably because they don’t make fast tires bigger than the 26mm. The one size up - the sworks turbo cotton 28mm is designated hell of the north version with extra puncture protection compared to
The standard TC, which their sponsored team never use on normal road race except the classics. Would be weird for them to champion something bigger if they don’t make and sell the thing.

Aside from Roval and a few few brands i don’t really see many brands put emphasis on 105 rule at all (not that the rule is wrong or outdated) but it seems interesting. Perhaps it’s too limited to prescribed exact tire sizes for customers? Even with Roval their reasoning for massive outer rim width is not particularly for the 105 rules but rather their philosophy on crosswind stability.

This is because there really isn't a 105 rule. It's too simplistic and doesn't take into account so many things that impact total system (Tire + Wheel) performance.

[iamraymond]

I'm trying to help a friend setup his new bike and he's running the Bora WTO 45 rim brake wheels with Ultegra R8000 calipers with the Campy red pads. I find that the pads are very thick and don't have much clearance even with the brakes completely opened up. Has any one else experienced this before? This is my first experience with carbon rim brakes so I'm wondering if it just might be that the pads are too thick and need to wear in?

The brakes function super well, but there's not alot of modulation at the levers because the pads are so close to the rim.

[MDecius]

Just a data point, I am running those exact wheels and pads with R8100 calipers (dual pivot not direct-mount), and I had tons of room even on first setup. Glancing over Shimano's webpage, the reach and wheel width numbers have not changed between the two generations, so I'm not sure what the difference could be.

[iamraymond]

Thanks for the input. That's good to know that there should be more clearance. I think I know what I did wrong. I swapped his brake pads (shoes and holder) from one bike to the other thinking that they were the same. But I believe there's a difference in the holders of the Direct Mount (on the new bike) and the Dual Pivot (on the old bike). Looking at bike24.com, I can see they sell two different types of Ultegra pads: one for DM Y2J498010 and a different one Y2J398010 for the dual pivot/standard mount.

I'll try swapping the holders to see if that does it.

[iamraymond]

Update: it was definitely the brake pad holders. I swapped those out and gained a lot of clearance in the front.

Interestingly, the pad holders/cartridges for the Dual Pivot are the same as the Direct Mount Rear. Only the front Direct Mount holder is unique as it has the pad lock screw in the front and positioned slightly closer to the center of the pad. The Dual Pivot front/rear and DM rear, have the pad lock screw towards the rear of the bike.

[ThunderJack07]

Just received the new Bora WTO 60, 1504g with Shimano freehub and tubeless valves.

[commendatore]

The latest disc C23, claimed weight 1460 g?

[ThunderJack07]

The latest disc C23, claimed weight 1460 g?

Yes, C23 disc

[jdecraene85]

Just received the new Bora WTO 60, 1504g with Shimano freehub and tubeless valves.

That's a bit disappointing, but the launch weight claims were a bit suspicious tbh... Less tempted now

[jlok]

Just received the new Bora WTO 60, 1504g with Shimano freehub and tubeless valves.

Still lighter than the Ultra WTO 60 C19 XDr at 1520g (excluding AFS lock rings). Not bad.

[ichobi]

Just received the new Bora WTO 60, 1504g with Shimano freehub and tubeless valves.

That's a bit disappointing, but the launch weight claims were a bit suspicious tbh... Less tempted now

Oow, that's 100g over the mark. (Claimed 1395).