Re: [RBW] Velocity Dyads and 50mm Tires

[Nick Payne]

On Tuesday, 23 June 2020 at 9:01:11 am UTC+10 peter...@gmail.com wrote:
 

> At the same pressure (psi) the larger the tire, the more force is applied 
> to the rim's sidewalls.
>

Yes, for a given pressure, stress in the walls of a cylindrical pressure 
vessel (of which a tyre is a good approximation) is proportional to the 
diameter of the vessel. So a 50mm tyre at any pressure will put about twice 
as much stress on the walls of the rim as a 25mm tyre at the same pressure. 
Conversely, a 50mm tyre at, say, 35psi, and a 25mm tyre at 70psi will put 
approximately equal stresses on the rim wall.

On the bike I have that takes that sort of tyhre size, with 55mm tyres I 
run the front at 25pis and the rear at 35psi (H Plus Son Todestrieb rims).

Nick

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Re: [RBW] Velocity Dyads and 50mm Tires

[Chris L]

Wow.   I weigh 385 and I pump any 50+ mm tire to 45 psi and consider that 
higher than I really need.   

I've been riding Dyads and have had 50+ mm tires on them probably 95% of 
the time.  I don't do huge miles but the wheels are about 7-8 years old.  
Zero problems with the rims or wheels.  


On Monday, June 22, 2020 at 6:01:11 PM UTC-5, Peter White wrote:
>
>  For example, Schwalbe says that if the rider weighs 240 lbs, a 50mm wide 
> tire should be inflated to 70psi. This is absurd. 
>
> Peter White
>
>
>

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Re: [RBW] Velocity Dyads and 50mm Tires

[John Rinker]

Peter,

Thank you for your insight on this. I weigh about 180lbs and run my 
Marathons at around 25 psi and 32 psi front a rear respectively (a little 
more depending what I'm carrying). I don't know if these lower pressures 
are a culprit, but it doesn't seem so according to what you've said. 
Velocity has been great about offering to replace the rim with a more 
suitable one (Cliffhanger). 

On my mountain bikes, I've run Mavic 719s forever with 2.25 tires. These 
rims seem to have a similar width as the Dyads, and I've never split a rim 
with fat tires. I got a set of wheels that are almost 20 years old and they 
still ride true after being beat to hell and back on my hardtail. 

Cheers,
John

On Monday, June 22, 2020 at 4:01:11 PM UTC-7, Peter White wrote:
>
> I'm a Velocity distributor. But their recommended tire sizes make no sense 
> to me.
>
> The problem with fat tires isn't that they're fat. It's that the tire 
> manufacturers give pressure ratings that only take into account the tire's 
> ability to stay on the rim, rather than a tire pressure that actually 
> delivers a good ride, and doesn't put excessive force on the sidewall of 
> the rim. For example, Schwalbe says that if the rider weighs 240 lbs, a 
> 50mm wide tire should be inflated to 70psi. This is absurd. At the same 
> pressure (psi) the larger the tire, the more force is applied to the rim's 
> sidewalls. It's POUNDS PER SQUARE INCH, and when you increase the square 
> inches of the tire's surface area, you increase the load on the sidewalls 
> of the rim. So it's no wonder that we see rims failing due to cracks in the 
> sidewalls, and cracks under the rim strips.
>
> Peter White
>
> On Mon, Jun 22, 2020 at 1:50 PM John Rinker  > wrote:
>
>> Good morning,
>>
>> Just wondering if anyone else has had an issue with Velocity Dyad rims 
>> splitting on the sidewalls while running fatter tires. I have been running 
>> some Schwalbe Marathon Mondials (28x2.0) and muy rear rim recently split. I 
>> am told by Velocity (who has been very helpful, indeed) that the tires are 
>> too big for these rims. 
>>
>> I love the tires and the rims, but perhaps I need an alternative to the 
>> Dyad to run these tires. Any recommendations?
>>
>> Cheers,
>> John
>>
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>>  
>> 
>> .
>>
>
>
> -- 
> Peter White
>

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Re: [RBW] Velocity Dyads and 50mm Tires

[Bill Schairer]

I did a week loaded on the GDMBR last summer with the DT TK540 on the rear and 
50mm Mondials.  I had no issues and wheel didn’t need any truing afterwards.  
As I recall it was an easy build and the rim has a very nice breaking surface.

Bill S

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Re: [RBW] Velocity Dyads and 50mm Tires

[Peter White]

I'm a Velocity distributor. But their recommended tire sizes make no sense
to me.

The problem with fat tires isn't that they're fat. It's that the tire
manufacturers give pressure ratings that only take into account the tire's
ability to stay on the rim, rather than a tire pressure that actually
delivers a good ride, and doesn't put excessive force on the sidewall of
the rim. For example, Schwalbe says that if the rider weighs 240 lbs, a
50mm wide tire should be inflated to 70psi. This is absurd. At the same
pressure (psi) the larger the tire, the more force is applied to the rim's
sidewalls. It's POUNDS PER SQUARE INCH, and when you increase the square
inches of the tire's surface area, you increase the load on the sidewalls
of the rim. So it's no wonder that we see rims failing due to cracks in the
sidewalls, and cracks under the rim strips.

Peter White

On Mon, Jun 22, 2020 at 1:50 PM John Rinker  wrote:

> Good morning,
>
> Just wondering if anyone else has had an issue with Velocity Dyad rims
> splitting on the sidewalls while running fatter tires. I have been running
> some Schwalbe Marathon Mondials (28x2.0) and muy rear rim recently split. I
> am told by Velocity (who has been very helpful, indeed) that the tires are
> too big for these rims.
>
> I love the tires and the rims, but perhaps I need an alternative to the
> Dyad to run these tires. Any recommendations?
>
> Cheers,
> John
>
> --
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> "RBW Owners Bunch" group.
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> 
> .
>


-- 
Peter White

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[RBW] Velocity Dyads and 50mm Tires

[John Rinker]

Good morning,

Just wondering if anyone else has had an issue with Velocity Dyad rims 
splitting on the sidewalls while running fatter tires. I have been running 
some Schwalbe Marathon Mondials (28x2.0) and muy rear rim recently split. I 
am told by Velocity (who has been very helpful, indeed) that the tires are 
too big for these rims. 

I love the tires and the rims, but perhaps I need an alternative to the 
Dyad to run these tires. Any recommendations?

Cheers,
John

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