road disc and sidewind??

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Delorre
Posts: 913
Joined: Sat May 24, 2014 12:09 pm

by Delorre

As I was quite disappointed by the stability of my Endurace disc, especially in side wind, I decided to sell it and to replace it with an Addict disc. Owning a rim brake version, and really liking the behaviour, even in hard side winds, I thought I couldn't go wrong with the disc brake version of it. Well, while better than the Endurace, I'm really surprised the Addict disc is far less planted than the rim version. Riding position is almost identical (few mm here and there, nothing more), geometry also. So, it has to be a result of disc brakes, but what exactly?

*It could be the wheels, that I took over from the Endurace. The Roval clx 32 made the side wind stability of the Endurace worse compared to the alloy DT wheels it came with out of the box. Those Rovals are only 32 mm tall and have a very round profile. So, I guess it's not really the rim profile. But the rims have to be fairly light to achive 1350 gr on a disc wheel. So, less gyroscope effect of really light rims vs more heavy alloy rims? The stock Carbon DT wheels that came with the Addict are now on the Endurace, but still unridden and not set up for sale yet. Will make a short ride on it to check everything is OK before the bike will be sold. I will see how it behaves with more heavy wheels (also 35mm tall)

*It could be the disc rotors. Although small in diameter, it's an almost plain surface that could catch a lot of side wind. Complete wrong guess, or could it influence the general behaviour of a bike?

The Addict is 'only' my secound disc bike, so, I not enough to genaralise. With's your experience? Any comparison with an almost identical rim brake bike?

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TonyM
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by TonyM

I have a BMC Roadmachine (disc) with the DT Swiss ERC 1100 Dicut in 47mm and I have no problems at all with crosswinds. DT Swiss advertised on this for their ERC and ARC wheels.

Delorre
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by Delorre

TonyM wrote:
Fri Dec 29, 2017 4:08 pm
I have a BMC Roadmachine (disc) with the DT Swiss ERC 1100 Dicut in 47mm and I have no problems at all with crosswinds. DT Swiss advertised on this for their ERC and ARC wheels.
OK, thx! But to be fair, a roadmachine has a very relax front end : slack head angle, a lot a center-front, a long wheelbase and low BB. This all contributes to a very stable ride by nature. An Addict is a pure race machine with direct but stable steering. I guess is't far more sensible to other factors. In 800km, I didn't have the chance to ride the disc version in calm weather. It's been very, very windy for the last couple of weeks, with daily 4 to 5 bf wind. If weather permits, I will do a side to side comparison of both addicts, on the same routes and same weather conditions. But I don't remember in the almost 20.000 miles on the rim version, that wind caused any problem.

But please, if you have a theory / ideas, shoot. This can only be instructive for everyone, as disc become more and more popular.

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TonyM
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by TonyM

My other bike is a C60 rim. Also very relaxed if I take your words. Also there no problems with crosswinds with my Bora 50 (but with my Lightweight Meilenstein!). What I mean is that the wheels are a key for having crosswinds problems or not. The head angle etc...will only amplify it.

If your both bikes are identical except the rim vs. disc brake then it is due to the rotor I suppose.

If the behavior in the crosswinds bother you you should maybe look at a different wheelset with even less profile.

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Calnago
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by Calnago

I think it's a safe assumption that anything with a larger flat surface area exposed directly to a wind source is going to be affected more than anything with a smaller flat surface area. Whether it's a problem or not is subjective and depends on, among other things, how much wind and how sensitive you are to it.
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TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

If you're really worried about this, I would switch away from the DA RT-900 rotors and start using SRAM Centerline X rotors. They obviously don't have the fins, but they have a better vent design for quiet operation and they warp less. I never could get my RT-99 or RT-900 rotors to stop making the gobble-gobble noises that showed up permanently after hard descents.

NiFTY
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by NiFTY

Where are you guys riding where sidewinds are such an issue. Are you storm chasers? Handling even a deep v shaped rim on a tt bike in the extensions is not as hard as you guys make a box rim on a windless day sound.
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TonyM
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by TonyM

@ Delorre: Where are you based?

TobinHatesYou
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by TobinHatesYou

NiFTY wrote:
Sun Dec 31, 2017 6:40 am
Where are you guys riding where sidewinds are such an issue. Are you storm chasers? Handling even a deep v shaped rim on a tt bike in the extensions is not as hard as you guys make a box rim on a windless day sound.
I don’t worry about my rotors personally, but I do ride in sustained winds often and have felt two different sensations.

1) While riding in a straight line, variable gusts forcing a steering correction...or strong steady winds making me steer into the wind just to ride straight.

2) The rear wheel feeling like it’s being pushed out in fast corners and forcing me wide. It feels like the whole rear end goes light and you’re about to lose traction.

Phil’s Fondo this year took place during a swell of Santa Ana Winds. The peak of Mt. Hamilton often has steady winds of 30mph. My main method of getting down from San Mateo to Woodside here in the Bay Area is via some windy corridors as well. There are days where I swap out my 5.6s for the 40mm Altos, and there are days where I wish I had 25-30mm wheels.
Last edited by TobinHatesYou on Sun Dec 31, 2017 9:10 am, edited 1 time in total.

Delorre
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Joined: Sat May 24, 2014 12:09 pm

by Delorre

TonyM wrote:
Sun Dec 31, 2017 6:49 am
@ Delorre: Where are you based?
Belgium. Just like in the Netherlands, we have wind 2 - 3 bf all year long, I'm used to it and like it after all, but the past 2 weeks, we had 4 - 5 bf wind every day, with wind peaks of 50 mph. Not the best conditions to judge a bike , but I have to say, I din't really enjoy the rides due to being throwed around a little too much.

As Tobin said, it's more the sudden wind bursts that are a problem. Steady side wind is easy to cope with, even with the disc bike : you put in a certain amount of countersteer, and no problemo. But as soon as a car pass you, or you have some houses that shield you from wind , the difference in wind pushes you around quite a bit.

I will have a look at the Sram rotors, thx for the tip :wink:

Hexsense
Posts: 371
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

TobinHatesYou wrote:
Sun Dec 31, 2017 8:02 am

2) The rear wheel feeling like it’s being pushed out in fast corners and forcing me wide. It feels like the whole rear end goes light and you’re about to lose traction.
That sound familiar to when i moved my seat (and handlebar, of course) too far forward that my center of gravity is way off to the front than what i'm used to. i saw myself sit further back on saddle on hard corner to maintain control and rear end traction then i eventually just move my setup more rearward of the bike to get weight balance i desired. hopefully this is not the case.

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