Workshop tales, trials and disasters.
Maintenance tips, techniques and myths.
Technical discussion, description and outright lies
They did that Michael, I lusted over me mate Allans until he let me ride it and was happy to go back to the good ol' Repco with the banana seat swapped out, knobbies and a bush mechanick'd low rise MX bar. That old girl took me everywhere...
London Boy 29/12/2011
Regarding previous comments on disc size and suitability of discs for road bikes: in December my wife and I rode the east and north coasts of Tassie on bikes with 160mm mechanical discs. As anyone who's been there knows, there are some amazing hills in Tas and descents to match. The bikes each weighed around 40 kg laden, so my total rolling weight would have been 130 kg.
I'm a convert. No problems at all for the whole trip. No sign of overheating on long, twisting descents at high speed. We got bucketed on near Piper's River and the brakes worked perfectly. We were heading into the entrance of a narrow track when my wife decided she couldn't make it and stopped suddenly in front of me. I had to panic stop as I couldn't pass; on my road bike I'd couldn't have stopped in time - on these I had no trouble at all.
Take home lesson: If a 160mm disc will stop the juggernaut that is my fat arse on a laden touring bike, you should all be fine.
I borrowed my son's bike for the trip as my new bike wasn't ready in time. The new bike is now complete and sports BB7s, I'm thinking about converting a pair of Magura MT2s to fit the Campy ergos.
Hmmm, trend seems to be that those with discs up front only, want bigger, yet those with frames built to suit discs front and rear have no issues with size of 160s (and less?).
Been running my road bike with calipers on road, and the sscx with canti brakes off road quite a lot during this dry summer and been happy with the braking. Still think discs are great for day in day out commuting and a one bike that can do it all, but now not sure I would go discs for a fast light road bike if I would ever needed to update my current ride (doubtful as current bike works across so many levels of the type of riding I do)
Worst still, if I was in the market for a new cross bike I wouldn't even think about discs and just go for a thing that would/ could do it all and yet make one smile by just looking at it..... http://www.ritcheylogic.com/dyn_prodfamily.php?k=472408
Can you elaborate why yopu think they wouldn't work on a fast light road bike vs any other roadie ?
I'm aming for 7kg all up for my double disc Voalgi Liscio (when the frame finally arrives), and can't wait to ride it.
180mm disc on the front and 160 rear
You better post loooooottts of pics...
London Boy 29/12/2011
Micheal, not "they wouldn't work" just thinking that I now wouldn't bother as a rim/caliper set up delivers for my riding fast light road bike needs (which is not really that fast or light, more long medium paced rides and medium/ light weight).
I guess I have now found it is good having the choice of which bike to ride and lucky enough to have both. Still like the thought that has gone into the Voalgis.....
The main reason I chose 185 over 160 BB7 on the front was to make emergency braking from the hoods easier as this was the main problem I had with caliper brakes. At the time of build the bike was going to be a all-weather bike so the disc presented a clear advantage.
Since I have a wet bike now, I changed to a V brake recently. Although I did get brake feel similar to a disc in the dry, I couldn't get rid of the squeal problem so went back to disc.
IMO the main disadvantage of disc for road bikes is more aero than weight. I read somewhere that Zipp did some testing to find (not surprisingly) that discs are poor for aero. Obviously this drag would have more effect on smaller riders as a percentage of their total drag than bigger riders.
Even if discs become legal for road racing, I doubt they would be used as anything more than specific wet day bikes.
That's the plan. Will even be a full writeup on BNA as well
In my mind, where the discs come into their own is in two cases - long descents and in the wet. I strike both of these in Adelaide (mind you, it's been pretty dry for a while). I find that the rim brakes can get grabbier at the end of a descent.
If I had multiple bikes, they'd all be disc equipped.
Yes, discs are aero poor compared to rim brakes, but by how much in the overall scheme of things when compared to the body sitting on top of the bike and thrashing away ?
Will discs be used at the WT level ? No idea, but it would be a brave team that would take the first step.
I've heard the term two thirds rider, one third bike from an expert like Obree on some video (this is regard to track TT with skin suits etc, so I suspect road bike would be more like 80/20 average). If discs produce 10% more drag for the bike at top speed on the flat than a normal road bike and we make the assumption of 80/20, then we're looking at a possible 2% on the flat at top speed (< 1Km/h). When combined with hills, corners and other normal stuff it would probably make < 1% difference to the average faster rider (< 0.4 Km/h). A pro would obviously notice the difference, the average rider won't go fast enough to really notice. In a bunch it won't matter. As said above a bigger rider like yourself is going to measure the difference even less.
My riding is mainly flat. To me it felt slightly faster on 16/20 spoke racing wheels with V brakes than 32/36 spoke touring wheels with disc on front. All other things were equal.
Hopefully in time you or someone will do some back to back tests to see how much difference it really makes to the average rider. I suspect barely noticeable, like 3Kg in bike weight.
In the end we run discs because they do the job better in wet conditions, which prevents injury.
Actually less than 1%. Power required to overcome drag increases as the cube of speed, so if the drag is increased by 2%, at constant power output speed will decrease by about 0.7%. This ignores other drains on power (tyres, friction etc) but they will work to reduce the speed deficit so it's good enough for Government work.
Good point. Thanks.
Not really comparing apples with apples there are we .....
I'm even looking at the M820/Zee caliper and wondering what the relative piston sizes are so that I can see if it will work with the Parabox m/cyl size. I like the idea of 4 pistons and a big pad
Oh, I think it's a little bit more than that
Adding a little variable to the whole mix: If running discs lets you brake later and harder for bends etc, would there be any net benefit even with the whole poor aero thing working?
London Boy 29/12/2011
Road racing no, criteriums maybe.
So we get the leaders we deserve and we elect, we get the companies and the products that we ask for, right? And we have to ask for different things. – Paul Gilding
but really, that's rubbish. We get none of it because the choices are illusory.
do tell...hydro box or something else in mind?
Was/is there a 130/135mm campy compatible rear hub?
No I don't like the idea of a conversion box. My intention is to remould the cylinder housing in carbon to make it the shape of a Campy ergo and then attach the gear shift mechanism. I'll also need new levers but they're easy to make. Still trying to figure how to get the cable run right and allow good access to the bleed port - it may yet defeat me. I won't ride Shimano ever again and I could die before Campy sees the light and makes direct hydraulic ergos.
To get a Campy compatible 135 rear I used a DT swiss hub and swapped out the freehub section. IIRC I had to put a 0.5mm spacer in to get things right. I also under-dished the wheel by 3mm to get the DS / NDS ratio to 0.7 which is roughly equal to 1.5^2 / 1.8^2 (revos / competitions if you use DT swiss spokes). I built the rear end of the frame to match so they only go together but that's not a problem for me - I don't have mechanics chasing me with spare wheels.
Stuck any boron through yourself yet?
Last edited by Mark Kelly on Sat Jan 12, 2013 12:45 pm, edited 1 time in total.
You might die before Shimano and SRAM do it too.
I came close to getting cleaned up this morning on the Victoria Road crossing of the bay to bay ride. The light was red for Victoria Road traffic and I'm crossing at the ped/cycle crossing and heard something behind me to the right. I look back to see this big dual cab 4WD ute go straight through the red and keep going like nothing had happened. Sunlight must have been in his/her eyes. It can happen at any time...
Now you're talking. I too have tried this. only to mock up stage in card and filler.The change of dangle angle in the (alloy) lever stumped me but i have not done any small part layups before...only 35 ft boats!
boron in fridge awaiting vac bag. Maybe combo rack/guard for commuter?
SRAM is close (HydroR) and reportedly Shimano is doing something for 2014 .....
http://reviews.roadbikereview.com/why-y ... oad-bike/2
Interesting article.. I saw the other day that specialized now have a roubaix available with discs too..
Disc Brakes had a bit of a shocker this last week at the US CX nats... was pretty funny watching some of the races. The Cannondale riders had no choice but to run them... but everyone else was back on canti's.
May not be very important in Australian conditions but interesting all the same.
http://velonews.competitor.com/2013/01/ ... mud_271112
So they are basically saying that they need hydro brakes with thicker, longer wearing pads. They aren't issues that a change in design can't solve or at least help. Like most engineering challenges, they just need to have a rethink and another go at it. Still early days for discs in CX.
Still on my first set of sintered pads on the road, which is since March 2010. Obviously where I ride is fairly flat and flowing. Don't need brakes much.
Yes it is interesting, but contains a few errors.
There is also the Hope V-Twin system available (similar in operation to the Parabox) out as well.
Why does he complain about the rear brake cable routing when the front (on the Parabox) is EXACTLY the same ? The 324 Labs system is still in pre-order stage (and the page doesn't seem to have been updated for some time) and looks a bit messier than the Parabox (imho).
I'm curious as to what the weight comparison between all of the three systems is. Also, curious re the pad sizing on the Formula calipers.
As Nobody mentioned, it's still early days re development of CX/Road discs, and I think there is much to come.
SRAM's HydroR is the next step chnage, and probably Shimano's system will be the next big change.
Until then, we wait ......
Seems like the issue was with cable discs only. No mention of any issue with the Hydro equipped ones - or did I miss something ?
Have done 3,000+km on my Parabox discs (plenty of descents with hard braking) and the pads are still fine.
They were using cables, but one of the mechanics made this comment:
"Mechanic Chandler Snyder of Chandler Cycling Service, who has been working on many a distraught rider’s disc-equipped bike on Thursday and Friday, says hydraulic brakes would have helped, but added that “the pads are wearing so fast here that they would not last through the race either.” "
Discs are meant to shine in these conditions. This is proof that they're not all that they're cracked up to be and that there is no perfect, one-size-fits-all solution when it comes to bicycle brakes.
The largest obstacle when it comes to disc brakes on a bicycle is weight. If you want better braking, you need bigger, thicker [and therefore heavier] discs and pads... But then you have to push all that extra weight.
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