Hi,
I'm looking to improve the front braking of my 1974 r90/6, which is currently pretty dismal. I am familiar with the article that came out of the 2018 supertech on this subject: https://www.r90s.info/Articles/upgrade_brakes.html.
However, I am wondering if anyone has firsthand experience employing the recommended solutions and can comment on the cost and effort vs. the effectiveness.
I am going to start with new Lucas pads from boxer2valve and fresh fluid and bleeding, and my mechanic is going to "buff up" the disc. However, I don't expect that to result in miracles, and I am considering having Apple Hydraulics sleeve the master cylinder. The representative I spoke with said they could go from 14mm to 12.7mm for a likely 15% improvement in assist at the lever. The rebuild and new piston would run me about $270 plus labor by my local mechanic.
There is also, of course, the option of adding a second disc, but I don't even know where to start on finding the parts for that and estimating cost, which seems like it would be significant.
Any advice or firsthand experience (or if anyone wants to unload a compatible set of fork legs with a second disc) would be greatly appreciated! Thanks in advance.
Best,
Jason
I most definitely have some ideas. In order of effectiveness...
1. Everything else pales in comparison to replacing the standard brake hoses with what are known as "stainless steel hose". The name refers to the anti-expansion sheath used to keep the hoses from expanding under hard braking. The actual hose the fluid runs in is PTFE (aka Teflon). Modern versions have the stainless steel hidden under an outer sheath of colored vinyl. If you buy the black vinyl, then you can't tell the new hoses from the OEM, so your stock "look" is maintained. But you could also have red, blue or yellow if you so desire.
There is a lot more info HERE.
If you choose not to replace the hoses, then NOTHING else you do will have any real effect.
2. The stock BMW rotors are OK, but if you really want to stop then replace the OEM with an EBC full floating disc. These are not cheap (~$250) but man do they ever STOP! You are wise to replace the OEM pads, but best results are obtained when you match them to the EBC pad set designed for these rotors. HERE
3. There is a major amount of compliance introduced into the system by BMW using a cable operated master cylinder. This compliance is why modern systems have the lever directly connected to the master cylinder. However for you to do that and look stock, you've need to buy the twist grip, electrical switch gear AND master cylinder. That could be a sizable sum, unless there is a motorcycle junk yard near you.
Still there are people who sleeve the OEM under-tank master cycling and this is a way to get respectable results for not much money. Look in your Club newsletter for these guys.
4. While all these systems are apart is a great time to consider your brake fluid. You have 2 choices: DOT4 which is what BMW recommends, and DOT5 Silicone which is what Harley uses. As long as you do not have ABS brakes, then these are equivalent in street use performance.
The big advantage for the DOT5 Silicone is that it will not attack your vintage paint, whereas DOT4 will totally destroy any painted surface it's left on. To me, DOT4 is simply a PIA all the way around. It requires a lot more maintenance... which increases your chances of screwing up your paint. Your choice. I'm simply pointing out that you have a choice at this juncture.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
► Here's a photo of my 1988 "single-sided" with stainless steel hoses and EBC brake rotors...
With the black vinyl coated hose, you need to look fairly hard to tell it's not stock.
► If you did decide to go with a double disc setup, then you'd want to buy a complete front end off of an early 1980's R100 with the dual Brembo calipers. (That will work with your existing front wheel.) The advantage is that your current ATE system employs a single piston caliper, so the caliper has to pivot in order to stop. The Brembo system employs a dual piston design (1 from each side) and so the stopping efficiency is increased. The Brembo system also has the more desirable bar-mounted master cylinder, whereas with the dual ATE system simply uses the same cable-operated, under-tank m/c.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
@wobbly This is fantastic and very valuable advice. Thanks very much! I will start with the new pads and brake hose and consider that EBC disk you mentioned. I then will probably progress to having the existing master cylinder re-sleeved by applehydraulics. I priced a handlebar mounted master cylinder at Max BMW and it was $$$, because, yes, it required a new throttle, etc. I'm wondering if there are stand alone units that would allow me to use the existing throttle, but I don't think that is possible.
► There are BMW "breakers" on Ebay. Price an entire '81/'82 front end and ask them to thrown in the RH sw cluster and master cyl.
► If you make up your own hoses with units from Fragola (and the like), you can eliminate some of the steel lines at the same time. If planned correctly, you can also eliminate a few of the places in which the stock hydraulic system collects air. This will make it easier to eliminate air, which increases your stopping power. For instance, the rear hose replacement is typically just a single long hose, which eliminates 2 steel lines and a hose.
Hope this helps
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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