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PostPosted: Mon Jul 09, 2012 9:01 am 
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Formerly known as wassertreter

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dudu wrote:
It looks like i might have to ride Al clinchers on my climbing rides [...]

As others have said already, it's a long shot calling Al clinchers safer than carbon tubs across the board. A small imperfection in the rim tape can lead to blowouts quickly when the rim is heating up.
Apparently quite a few alu tub front wheels were brought out on Giro mountain stages this year, if Eurosport comments are credible.

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Posted: Mon Jul 09, 2012 9:01 am 


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PostPosted: Mon Jul 09, 2012 10:49 am 
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Location: France
you can make a compromise since most of the braking is from the front : Al rim 27mm in front and Bora rear


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PostPosted: Mon Jul 09, 2012 11:44 am 
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Location: Belgium
Hi,

Quote:
Apparently quite a few alu tub front wheels were brought out on Giro mountain stages this year, if Eurosport comments are credible.


Yes, but nothing to do with heating up rim cement though. More likely for better braking performance and less susceptibility to crosswinds.

I fully agree with other people's opinion regarding this Conti's carbon specific rim cement, it's a royal PITA and not worth the bother.

IMHO it takes an awful lot of abuse to make a properly glued tubular roll due to heat, you'd almost had to do it on purpose....

Ciao, ;)

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PostPosted: Mon Jul 09, 2012 4:08 pm 
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After applying glue (conti carbon) and letting it dry I mist both tire and rim with cold water. This allows you to reposition the tire but you will need additional drying time. I personally clamp the tire while drying. After 24 hours you will have a VERY tight bond. Never had any issues doing it this way.

Guess I'll put on my Boras, have not used them this season. Today's TDF TT has me inspired

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PostPosted: Tue Jul 10, 2012 12:19 am 
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Location: Belgium
Hi,

While watching Flemish television tonight I saw a program about the TDF where they had Julien Devriese (ex Lance A and Eddy M technician among many others) talking about how Radioshack (not sure about the team) filled the tyres with nitrogen.
According to Julien D this keeps the pressure in the tyre constant so even under heavy braking chances of rim cement heating up to melting point are reduced considerably.

They also talked tubulars and the Youtube video showing Julien's cellar filled with aging tubbies was dsiplayed on tele.

http://inbussleutel.blogspot.be/2011/01/julien-de-vriese.html

Just an idea... 8)

Ciao, ;)

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PostPosted: Tue Jul 10, 2012 12:09 pm 
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A bit off topic, but I had fair success so far with Conti carbon cement. It dries quickly, i.e. when around the rim with the brush, the start is already tacky. What I did was to mount the tyre pretty immediately after the last layer, I could true it (almost) ok :-)

Anyway a tin of Mastik is on order.

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PostPosted: Tue Jul 10, 2012 3:22 pm 
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fdegrove wrote:
Hi,

While watching Flemish television tonight I saw a program about the TDF where they had Julien Devriese (ex Lance A and Eddy M technician among many others) talking about how Radioshack (not sure about the team) filled the tyres with nitrogen.
According to Julien D this keeps the pressure in the tyre constant so even under heavy braking chances of rim cement heating up to melting point are reduced considerably.

They also talked tubulars and the Youtube video showing Julien's cellar filled with aging tubbies was dsiplayed on tele.

http://inbussleutel.blogspot.be/2011/01/julien-de-vriese.html

Just an idea... 8)

Ciao, ;)


Pure Nitrogen keeps the tire pressure more constant over a range of temperature. It also migrates less fast through rubber than O2 and CO2 (CO2 being worst). It's used in Formula-1 and airplane tires as these tires heat up considerably. The key is that it has to be pure nitrogen and not contaminated with e.g. water/humidity. It doesn't help with the rim/glue bond however, the heat comes from the rims and as such the tire (whatever gas it is filled with) will have very little impact on the heat accumulating in a rim.

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PostPosted: Tue Jul 10, 2012 4:51 pm 
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Location: Belgium
Hi,

Yep, they showed the kit with the appropriate filters.
The part about reducing heating up of the rim cement was actually my assumption, not Julien's. Will scrap the idea mentally.... :lol:

You saw Vive le Velo as well last night?

Sorry for the OT guys. :oops:

Ciao, ;)

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PostPosted: Wed Jul 11, 2012 10:53 am 
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I have just spent a week in the Pyrenees with my boras. It is the first time I have ridden on tubulars or carbon wheels and I was a bit apprehensive after seeing some ruined blistered boras in my lbs from someone doing the marmotte last year. And from club mates saying that apparently the tyre can come away from the rim if you brake too much.

Well after about 6 very big descents with a temperate of over 100f when descending the aubisque and soulor, my conclusion is that anyone who has ruined carbon wheels from braking must have been on them the whole way down. This ties in with the lbs story of the marmotte guy.

To put in context, I have never been on a longer descent than about 1km before so my technique was being learnt day on day. Despite this, my wheels never heated up greatly and I am sure my technique wasn't te best.

Bottom line from myself who is a very inexperienced descender, unless you are obscenely nervous and nothing short of appalling with your hands glued to the shifters on a descent, you will be fine. That is all I have to say really. Ie it is a bit of a non issue perhaps? I add that my weight is 62kg.


Last edited by derosaprotos on Wed Jul 11, 2012 11:22 am, edited 1 time in total.

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PostPosted: Wed Jul 11, 2012 11:05 am 
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fdegrove wrote:
You saw Vive le Velo as well last night?

Yeap ;)

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PostPosted: Fri Jul 13, 2012 10:47 pm 
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A bit off topic: I experienced a catastrophic front wheel blow out on front new carbon clincher rim on steep windy descent of a quarter mile. Rim didn't deform but braking became spongy, heard pop and next thing I was on the ground in the middle of the road, briefly unconscious, shoulder separation, hip contusion but ultimately recovered okay. Appears that bead of tire came off and tube blew out. Had ridden same brand carbon clinchers for previous year with instance of warping and replacement of front rim by manufacturer but never a failure until this ride on newest version of rim. Now will only ride on AL clincher rims. Miss the ride of carbon rims and considering getting some tubular ones built. Having a light front AL rim and rear carbon wheel seems like a good compromise for those of us who love to climb and live in hilly terrain.


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PostPosted: Sat Jul 14, 2012 3:11 am 
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Location: Wherever there's a mountain beckoning to be climbed
bluhorizon,

Are you just relating this incident viewtopic.php?f=3&t=75801&p=713529#p713529 , or is this a new incident?


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PostPosted: Sat Jul 14, 2012 9:10 pm 
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Basically it´s about braking technique. If you don´t know how to ride a fast descent while only braking hard just before turns then you should not ride tubbies (or overinflated clinchers for that matter). Braking too much overheats your rims and is potentially very dangerous. My safest bet for a non pro (at descending that is) is tubeless tires on aluminium rims at about 80 psi.

Descending is an absolute art form so there is nothing embarrassing about not being able to ride your light carbon rimmed wheelset on a tough descent. It´s more embarrassing not realising your limits as a rider...

Take this advice from someone who has the scars to prove his point...

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PostPosted: Sat Jul 14, 2012 10:22 pm 
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Manufacturers say that their products are tested beyond the limits of all of us who are weekend riders to the point of failure. Intermittent heavy braking on steep descents should not result in catastrophic failure. Unless you are thinking of Alpe d'Huez time trial where wheels are designed only for the uphill climb and not for descending.


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