Have recently completed an upgrade to the RST disk brake on the rear of our Orbit 26 Twin using a Hope Mono M4 185 mm disk. The new brake has taken a few miles to bed-in but is now performing an excellent job and in most circumstances is our main braking method.
There were a few issues that came up with the work that may be of interest to others thinking of an upgrade.
1. The supposed ISO mount isn't ! To make it work we had Hope fit an ISO front caliper on a rear brake lever. It looks like the mount is a front one to allow clearance to the pannier rack fitting.
2. The 185 mm disk is an unusual size. The RST uses 192 mm, but this is too large for the Hope Mono M4 caliper. The 185 mm disk was available overnight at no extra cost from Hope.
3. Opted for the stainless braided hose. This looks substantial, but time will tell whether it has adequate durability.
Have riden ~50 miles around the Peak District with the new brake so far. Brake now capable of fairly rapid slowing from 40 mph with no ill effects. :)
Will be testing it further over the summer, including a trip over the Col du Tourmalet. :eek:
Hope this helps anyone thinking of a similar upgrade. Comments welcome.
Brian
06-17-05, 04:01 AM
Braided hoses are a must on a tandem. That's the only way Magura will approve their brakes on a tandem, Hope should be the same.
Peak Team
06-17-05, 08:45 AM
Braided hoses are a must on a tandem. That's the only way Magura will approve their brakes on a tandem, Hope should be the same.
Interesting one. My understanding of the braided hose is that it is more robust and has reduced internal expansion. Do you have any comments on why Magura see these as specific advantages on a tandem ?
Brian
06-17-05, 04:06 PM
Apparently the heat generated by a disc on a tandem is enough to cause plastic parts to melt, including plastic brake lines. I did a Google search for tandem rated disc brakes, and came across an actual scientific test where they tried different brakes under an increasing load. At the time, I think only Avid mechanicals held up to the highest load. Alex@mtbtandems.com has worked with manufacturers to get them to approve discs for tandem use, and that's where I got the Magura info from. I'll look for a link to the brake test.
Brian
06-17-05, 04:15 PM
http://www.ihpva.org/pipermail/hpv/Week-of-Mon-20020304/023003.html This isn't exactly what I was referring to, but if you scroll down, it seems to have all the details covered.
stapfam
06-18-05, 02:03 PM
When I converted my Dale to Discs, I, and The LBS I was working through, contacted Hope for all the Necessary details. Fitted Mono M4's with 200mm discs F.& R. Standard brake pipe was used, and in 18 months use with some very severe braking at times, have had no problems at all with the piping, or any other part of these brakes.
I was involved in manufacturing Brake units within Motorsport (Karts) and we used to generate a lot more heat that any Bike brake system will. You imagine a disc glowing red after a 20 minute race, and that is hot. We used to use unshielded nylon piping that is not up to the grade that is used on my tandem.
I am definitely not saying that Standard Piping will be suitable in every case, as I never use disc brakes as a drag brake, but providing the Piping used is to a high enough grade, and manufactured to a specification that is suitable, then in normal use there will not be a problem with it. That is if you can call Offroad, and onroad now, downhills at 50mph+ normal.
Brian
06-18-05, 04:48 PM
At $100 for a set of lines that are also cut-proof and kink proof, I can't see not buying the extra insurance it provides. Since we have a coupled tandem, the kink proof part is a big selling point too.
phinney
06-18-05, 05:03 PM
For the brake lines to get hot enough to fail the fluid would too and I'd think that would be way past the boiling point. More likely the benefit of the braided lines would be increased sidewall stiffness to reduce sponginess at the lever. This could be important for the long hose length to the back brake on a tandem. If the lever's not spongy then no problem.
Great data in the attached links!
Brian
06-18-05, 05:58 PM
Great data in the attached links!
Thanks. My wife rides on the back of our tandem, so I tend to not leave anything to chance. We took the position that "Good enough" isn't. The bike was originally envisioned as more of a touring MTB than a purely off road venture. But between the cost of building it, and the cost of taking the family from Australia to the US for an extended holiday, we don't have much budget left for a cycling holiday any time soon. That leaves us in the position of riding locally, where we have some great bush tracks and lots of high speed hills. Braking is a pretty important issue. I can smell breakfast cooking, and I think I'm losing my train of thought. Happy Father's Day to all you other dads out there.
stapfam
06-21-05, 02:45 PM
For the brake lines to get hot enough to fail the fluid would too and I'd think that would be way past the boiling point. More likely the benefit of the braided lines would be increased sidewall stiffness to reduce sponginess at the lever. This could be important for the long hose length to the back brake on a tandem. If the lever's not spongy then no problem.
Great data in the attached links!
Just realised the only problem I ever had in Karting on the brake front, and that was Moisture getting into the brake fluid. Only had it happen once and that was an atmospheric anomoly at one particulat circuit at 3 am in the morning. (I did Endurance racing- 6,12 and 24 hour races). Contacted ferodo and they came up with a fluid that repelled the moisture. This was a new grade of Brake fluid called DOT 4. The old fluid that did actually boil was dot 3. Still no problem with the brake lines even though the temperature was way above what we would have expected.