BB7 disc: disappointing, why?

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Re: BB7 disc: disappointing, why?

Postby trailgumby » Mon Jun 28, 2010 2:01 pm

Uncle Grumpy wrote:I'd be too scared to use discs on skinny tyres on wet bitumen. I reckon I'd hit them in a panic stop and just lock up and keep sliding without decellerating.

I run 23mm slicks on 700c rims on my mtb commuter with Shimano XT 2-pot hydros.

I haven't had an issue, but then I haven't had to panic stop in the wet as I'm hypervigilant in the wet. The rubber I run is the pretty sticky Conti GP4000s Black Chilli. Plus, I shift me bum back behind and below the saddle under brakes (mtb habit) and have panniers on the rear as well, so I get more stopping power from BOTH tyres than most would if just loading up the front. I'm sure the day will come, though.


I like the instant-on feel of the discs - you don't have to wait for the water to be squeeezed out before they bite like seems to happen with rim brakes in wet weather.
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by BNA » Mon Jun 28, 2010 2:05 pm

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Re: BB7 disc: disappointing, why?

Postby baabaa » Mon Jun 28, 2010 2:05 pm

When did that come into being? The impression I had was they were still officially off-limits and with no prospect of it changing in the near future?

An excellent development - if anybody needs them, it's CXers.




http://www.cyclingweekly.co.uk/news/lat ... hoice.html
UCI clears disc brakes for 'cross bikes but narrows tyre choice

Of more interest to top-level cyclocross riders who aren't thinking of adding electric motors to their racing machines is that disc brakes will now be allowed from the 2010/2011 season but that only tyres at or narrower than 33mm will be permitted instead of the previous 35mm maximum width limit.

And also in the same:

Earlier today, Lance Armstrong posted on his Twitter feed, "UCI approves disk brakes for cyclo-cross. Great news. I look fwd to the day they're approved for road racing."

So watch this space for a whole swag of new options for road bikes.
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Re: BB7 disc: disappointing, why?

Postby MichaelB » Mon Jun 28, 2010 2:17 pm

trailgumby wrote:
I like the instant-on feel of the discs - you don't have to wait for the water to be squeeezed out before they bite like seems to happen with rim brakes in wet weather.


Uh huh. I like the idea of being ready to stop on a wet day rather than having to constantly feather the brakes to get rid of the water so that you can actually brake, even with the Kool Stop salmon pads.

Watching this space with interest.
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Re: BB7 disc: disappointing, why?

Postby cooperplace » Mon Jun 28, 2010 2:32 pm

cooperplace wrote:
Lark2004 wrote:I hope your forks are well made.....

Image


that is fascinating, and obviously scary. We would all be very grateful if you could tell us more about that picture: eg. what brand fork is it? and how did it happen? is it your fork? what sort of surface was the bike on at the time? anyhting you might know about it.

thanks


I've just read the stuff on the website that photo came from. It's not relevant to my bike, so everyone can stop losing sleep about me.
Please be nice to me, I'm not very bright.
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Re: BB7 disc: disappointing, why?

Postby cooperplace » Thu Jul 01, 2010 1:49 pm

after some bedding in, the BB7 is great. Powerful: can lift the back wheel with 2 fingers, and easy to modulate.
Please be nice to me, I'm not very bright.
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Re: BB7 disc: disappointing, why?

Postby baabaa » Thu Jul 01, 2010 3:04 pm

Good to hear.
You may have some cable stretch in a few weeks. Do you have inline adjusters? A few twists of these will help take up the slack.
When it comes time to adjust beyond a twist or two on your adjusters you will need to move to your "red knobs". Give another hoi if needed.
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Re: BB7 disc: disappointing, why?

Postby MountGower » Thu Jul 01, 2010 4:13 pm

Too good. Without meaning to drag things out, I reckon a titanium BB7 would murder the hydraulic brake industry. Glad it all worked out without having to whip out the wallet.
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Re: BB7 disc: disappointing, why?

Postby }SkOrPn--7 » Thu Jul 01, 2010 4:27 pm

Glad it's sorted and that you appear to be on the way to being happy with the new BB7

MountGower wrote:Too good. Without meaning to drag things out, I reckon a titanium BB7 would murder the hydraulic brake industry. Glad it all worked out without having to whip out the wallet.


MountGower two of my rides have Juicy 7's Hydro's and while I luv the modulation/feel and power I have since stepped away from hydro's now buying BB7's because you just can't beat the price/adjust-ability and then if you get the Avid Speed Dial 7 levers then you have even further adjustment to feel. So for me at this stage the standard BB7 has swung me away from hydro's let alone a titanium set. :D
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Re: BB7 disc: disappointing, why?

Postby Nobody » Thu Jul 01, 2010 4:32 pm

MountGower wrote:Too good. Without meaning to drag things out, I reckon a titanium BB7 would murder the hydraulic brake industry. Glad it all worked out without having to whip out the wallet.
I'd say Avid/SRAM have probably looked at it and may have come to the conclusion that regardless of performance to weight, hydros either had more potential or there was too much stigma attached to cable brakes. Kind of like CF is always perceived to be better than aluminium alloy.
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Re: BB7 disc: disappointing, why?

Postby rowdyflat » Thu Jul 01, 2010 9:48 pm

I have seen discs on road bikes but it does add weight +, the fork needs to be braced or replaced to get braking power .
Having tried different setups I have found that if you have mtb brake levers even on drop bars + curved large mtb brake pads even conventional road bike calipers become quite powerful enough for descending steep roads eg Dolomites.
The other thing to consider is that with conventional road brake levers or brifters on drop bars it is difficult to shift your weight back behind the seat to get really good tyre traction.
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Re: BB7 disc: disappointing, why?

Postby Uncle Grumpy » Fri Jul 02, 2010 9:45 am

MountGower wrote:Too good. Without meaning to drag things out, I reckon a titanium BB7 would murder the hydraulic brake industry.


Who knows what the future might hold.

Right now the big market for discs is the MTB market where hydros are widely accepted. I don't see a cable disc taking over the hydraulic market for MTB use.

Unless someone makes a hydro-brifter for road use (combining a cable shifter with a hydraulic master cylinder) then cable discs are here to stay for the road and cyclocross world. Not that there's anything wrong with cables, and I'm not suggesting that the road world should look at hydros.

As discs gain more acceptance and the market gets larger I'm sure Avid and others will look at light options, though I don't know about titanium, I reckon a lightweight magnesium caliper with heavily milled out 140mm rotors.

I don't think a ti cable disc would murder the hydraulic industry. I run Avid BB7s (MTB version), Avid Juicy 7s, Juicy 7 Ultimates and Hope 4 pots (with 203mm rotors and braided lines). I prefer the feel of the hydros but yeah the cables aren't far behind and the BB7s offer a lot of adjustability that you don't get in lower end hydros.

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Re: BB7 disc: disappointing, why?

Postby Nobody » Fri Jul 02, 2010 10:54 am

I think Shimano will bring out hydro STI eventually (but I hope they don't) as it will be an opportunity for them to corner the CX and road disc market. If this happens, SRAM might have to match Shimano's master cylinder piston volume rate if they want to sell more aftermarket road/CX disc brakes.

As for road brake size, I have a 185mm BB7 on the front as braking from the hoods needs all the leverage you can get. I thought about a 203, but fortunately didn't get it, as I found this out later:
Avid wrote:Note: Fork manufacturers often discourage the use of anything larger than a 185mm rotor on a standard quick-release.
http://www.sram.com/_media/techdocs/dis ... compat.pdf
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Re: BB7 disc: disappointing, why?

Postby MichaelB » Fri Jul 02, 2010 12:05 pm

Nobody wrote: ....As for road brake size, I have a 185mm BB7 on the front as braking from the hoods needs all the leverage you can get. .....


Can you share a bit more detail re your frame/fork setup ?

It seems that the forks available readily (Kenisis, Trigon et al) seem to be either MTB or CX oriented, and therefore have a higher axle crown dimension, and or rake that is closer to 43mm rather than the seemingly standard 45mm for road bikes.

Cheers

Michael B
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Re: BB7 disc: disappointing, why?

Postby baabaa » Fri Jul 02, 2010 1:30 pm

Sorry to jump in but...
BB7 road come with, and only offer 160 mm rotors.
BB7 mtb come with 160, 185 or 203 mm rotors.
I would guess that the road is kept small to keep it close to the fork and to lower the torque given road and cx bikes have finer fork tubing than mtn bikes.
I run road on a cx and mtb on a 29er both 160 and apart from the colour they both “look” the same.
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Re: BB7 disc: disappointing, why?

Postby human909 » Fri Jul 02, 2010 2:40 pm

baabaa wrote:Sorry to jump in but...
BB7 road come with, and only offer 160 mm rotors.
BB7 mtb come with 160, 185 or 203 mm rotors.
I would guess that the road is kept small to keep it close to the fork and to lower the torque given road and cx bikes have finer fork tubing than mtn bikes.


For a given braking force smaller rotors produce more torque.
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Re: BB7 disc: disappointing, why?

Postby MichaelB » Fri Jul 02, 2010 3:07 pm

human909 wrote:
For a given braking force smaller rotors produce more torque.


I think that you mean to write ;

"For a given braking retardation (i.e. decelaration), a smaller rotor needs to produce more torque, which is in tuirn produced by a greater clamping force on the disc"

I think... :roll: it's too close to home time from work .....
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Re: BB7 disc: disappointing, why?

Postby baabaa » Fri Jul 02, 2010 4:21 pm

Start talking about torque and.....
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Re: BB7 disc: disappointing, why?

Postby cobba » Fri Jul 02, 2010 4:40 pm

Avid wrote:Note: Fork manufacturers often discourage the use of anything larger than a 185mm rotor on a standard quick-release.

The rotor size recommendation/discouragement from Avid only refers to MTB forks, it doesn't mention road bike forks which have different fork ends.

MTB suspension forks made for standard QR skewers usually have a retention tab (lawyer lip) on the fork ends where the skewer is recessed into the fork end as a secondary safety measure to prevent the skewer/wheel coming out under braking, of the few disc compatible road bike forks I've seen none of them have this retention lip.
Image

http://www.bikemagic.com/gear-news/are-quick-releases-safe/3322.html

Busted carbon disc fork with bonded aluminium dropout: http://www.bustedcarbon.com/2009/11/carbon-fork-disc-brakes.html

The following quote was found at: http://www.ne.jp/asahi/julesandjames/home/disk_and_quick_release/index.html
From: [email protected]

Dear Customer
in reply to your technical question:

Is the 8" rotor compatable with the standard QR version of the Z1FR?

--------------------------------------------------------------------------
the reply is:
--------------------------------------------------------------------------
It will definitely fit onto the fork. It is recommended that an 8" rotor is not used on a standard axle fork because the forces exerted on the wheel can potentially pull the axle out of the dropouts. So, it will physically fit, but it is not recommended for aggressive riding.

Best Regards,
Marzocchi Staff
661-257-6630
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Re: BB7 disc: disappointing, why?

Postby Nobody » Fri Jul 02, 2010 5:18 pm

MichaelB wrote:It seems that the forks available readily (Kenisis, Trigon et al) seem to be either MTB or CX oriented, and therefore have a higher axle crown dimension, and or rake that is closer to 43mm rather than the seemingly standard 45mm for road bikes.
The fork is a Dimension Cross fork. It has a 399mm axle to crown and 45mm rake which is almost identical to the original Surly Cross Check fork. Another one worth considering is the Civia Hyland fork which has a lower 395mm axle to crown. What height of axle to crown length are you looking for?

My bike with the 185mm BB7 and Dimension Cross fork:
Image
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Re: BB7 disc: disappointing, why?

Postby Nobody » Fri Jul 02, 2010 5:40 pm

cobba wrote:
Avid wrote:Note: Fork manufacturers often discourage the use of anything larger than a 185mm rotor on a standard quick-release.

The rotor size recommendation/discouragement from Avid only refers to MTB forks, it doesn't mention road bike forks which have different fork ends.

MTB suspension forks made for standard QR skewers usually have a retention tab (lawyer lip) on the fork ends where the skewer is recessed into the fork end as a secondary safety measure to prevent the skewer/wheel coming out under braking, of the few disc compatible road bike forks I've seen none of them have this retention lip.

http://www.bikemagic.com/gear-news/are-quick-releases-safe/3322.html
All my forks are steel and have the retention tabs. Somehow I don't think I'll have a problem with them. I'll just take the advice to remember to keep them tight. Thanks. :)

cobba wrote:Busted carbon disc fork with bonded aluminium dropout: http://www.bustedcarbon.com/2009/11/carbon-fork-disc-brakes.html
One of my favourite sites. I'd say with CF bonded to Al, this is bound to happen eventually.
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Re: BB7 disc: disappointing, why?

Postby MichaelB » Mon Jul 05, 2010 9:19 am

Nobody wrote:
MichaelB wrote:It seems that the forks available readily (Kenisis, Trigon et al) seem to be either MTB or CX oriented, and therefore have a higher axle crown dimension, and or rake that is closer to 43mm rather than the seemingly standard 45mm for road bikes.
The fork is a Dimension Cross fork. It has a 399mm axle to crown and 45mm rake which is almost identical to the original Surly Cross Check fork. Another one worth considering is the Civia Hyland fork which has a lower 395mm axle to crown. What height of axle to crown length are you looking for?


Hi Nobody,

Thanks for the links - (i'm not a weight weenie, but bugger me if those forks ain heavy - 960g to 1150g :shock: )
I measured the fork on the Argon18, and it appears that the axle to crown height is 370mm (28C tyre fits in easily).

I'm waiting on a reply from Woundup at the moment as well, but will add you links to the list of possibilities :D
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Re: BB7 disc: disappointing, why?

Postby MichaelB » Thu Jul 15, 2010 10:57 am

MichaelB wrote:
I'm waiting on a reply from Woundup at the moment as well, but will add you links to the list of possibilities :D


After numerous emails that never really answered the Q, they pointed me to Aspire Velotech who are one of their distributors, so I sent them an email, and this is the response ;

Thanks for your email. We do not have a Wound Up Team X Disc fork, 1-1/8 inch steerer, 45mm rake with an axle to crown height of 374mm in stock and will need to order it from Wound Up for you. The base price for this fork is $495.00 with free shipping, but we will need to find out from Jake at Wound Up if there is an upcharge for the axle to crown height adjustment. The standard Team X Disc fork has a 395mm axle to crown height. We will contact Jake at Wound Up and get back to you with further information about your fork order and arrange payment at that time.

Crkey, $495 US peso's. :shock: Might have to give the Trigon or Cooperplaces's Kinesis one a trial first
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Re: BB7 disc: disappointing, why?

Postby Nobody » Thu Jul 15, 2010 11:06 am

So basically, production road disc forks don't really exist at this time. They are basically all 'cross/hybrid forks. I think it will change in time.
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Re: BB7 disc: disappointing, why?

Postby cobba » Thu Jul 15, 2010 10:43 pm

Kona have a nice looking carbon disc road fork, but you have to buy a bike to get it:

http://www.konaworld.com/bike.cfm?content=honkyinc
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Re: BB7 disc: disappointing, why?

Postby MichaelB » Fri Jul 16, 2010 9:09 am

cobba wrote:Kona have a nice looking carbon disc road fork, but you have to buy a bike to get it:

http://www.konaworld.com/bike.cfm?content=honkyinc


Might see what a "spare part" costs ....
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