Hey guys, There are lots of threads on this upgrade from under the tank to handle bar MC's Bike: r90/6 75 model But.... 1) what size MC, 14mm should be ok? 2) can I use any MC or does it have to be off an /7 or the like, i.e. can I use a Honda handle bar 14mm MC? I am replacing all switches/brake lines etc anyway so that's no issue Thanks guys
I prefer 13mm used on my 75 R90/6. This is a twin throttle pull M/C as used on some later airheads, your switches and throttle cables will transfer seamlessly. You can fit a front brake switch to it as well. This is still available new from BMW or from eBay? You can use any 13mm M/C. The only advantage of using the BMW unit is that it is a no hassle modification. I use a splitter under the fuel tank as per the later bikes, so I have a single hose to the splitter, then twin hoses to the lower hard lines. In terms of use 13mm works well to give you both power and control of the brakes, there it's lots more lever travel, but this is a good thing. I did a series of panic stops from about 70mph, fully loaded just to ensure that I would not run out of brakes coming down a mountain pass. Some people use 12mm, and I'm sure that 14 would work as well.
Chasbmw is right. 12, 13, or 14 are all good, but smaller is better; see http://roadstarclinic.com/content/view/89/95/ . I used a 14 mm and it works great, see post #125 here http://www.advrider.com/forums/showthread.php?t=741179&page=9 .
Cray. Iv seen that chart before but can't work out how to use it Eg with dual discs with single slave cylinders of 38mm each...........
My '78 (manufactured in '77) under the tank MC is 14mm. I expect your /6 under tank MC is also 14mm (but am not certain). Smaller is better and would go with 12 mm if it were the same cost and availability as a 13 mm.
Stan, I would guess that yours is a single disc bike? I reckon that having a full hydraulic system is better than BMWs strange mix of mechanical and Hydraulic
Yes, my MC is for a single 40 mm caliper and rotor. I know mine is 14 mm because the bore was measured before sending it out to be sleeved and subsequently installing a kit. The lack of a cable and linkage provides an advantage to the handle bar MC, compared to the under-tank approach. Based on hydraulics, the smaller the piston diameter in the MC the more mechanical advantage. But there must be enough volume to operate the brakes. Considering volume, a pad movement of 0.5 mm for dual 38 mm ATE caliper pistons requires a 12 mm handlebar MC piston to move ~10 mm. Although, I don't think pads would normally move that much.
When I switched mine over, I used a 13mm, and I'm really happy with it. If I were going to do it again though, I might consider a 12mm.
Let's see, dual calipers with single pistons... got it. Across the top of the chart is the MC size in mm, e.g., 13 mm. If you had a 13 mm (put in your MC number) then follow that column down to the piston row; piston size and number of pistons is the on the left side of the chart . Let's look at the left side and follow it down to 38 mm; listed is 38, 38 (2), and 38 (4). The number in parenthesis, e.g. (2), is the number of pistons. i.e., 38 (2) is used for our 38 mm dual caliper ATE's. So, follow the 38 (2) row across to the 13 mm column and there is your ratio; in this example it reads 17.09 From that chart, see: Single piston calipers are much happier in the 14:1 to 12:1 range. Keep that in mind. I have the 14 mm MC, dual 38 mm ARE's, so my ratio is 14.73.
i love all you guys, yew! thanks heaps for the replys guys I am trying to find a 12mm MC but sweet jebus, perhaps my googling skills are lacking but its real hard, and 13mm is no better! I will get my search on...see what i can find thanks again guys!
dude i love everything about your bike! thats a sweet setup what grips are they? they look nice and wide...im looking for some bigger grips as well (big ass gorilla hands)
This is the complete deal Just need to check that's a 13mm http://www.motobins.co.uk/bmw-parts.php?model=R Series 2 valve Twin
wicked - just having a sneaky look now thanks for that 300 pounds is pretty steep, hell yea. there are heaps of 14mm out there, and i love the 14mm ones i can find....just making sure it would work, peeps above all saying that its not ideal....hmm would there be much difference between having a 13mm to a 14mm? I am digging either of these: http://www.ebay.com/itm/NISSIN-Moto...Parts_Accessories&hash=item485084505f&vxp=mtr or this one because it has that orange factor too...(bikes orange) http://www.ebay.com/itm/BWS-ZUMA-JO...her_Vehicle_Parts&hash=item2a224b9fa7&vxp=mtr
Hearse, thanks for the compliment! Are asking about the handgrips on the handlebars? They are a stock BMW item, part #32-72-1-237-811 is the grooved handgrip (the smooth grips are #32-72-1-230-407 , see if this works http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51891&rnd=08102012
I used a 1/2" mc on twin 38mm ate's and found that while they stopped well they never felt firm at the lever. I could always pull the lever to the bars.
so how would you better the feel in the brake lever? Would you up the bore size to say a 13mm? (im trying to understand front brakes well in my head - so forgive the multiple questions )
I used a universal fitment Magura 13mm. It was like $110 I think. It fit very well with the /5 style throttle, after I chopped off the old brake lever perch. I got it from Economy Cycle, but I know lots of places sell it.
links dude? please :) got it - http://www.economycycle.com/servlet/the-295/Front-Master-Cylinder-Kit/Detail $50 delivery form USA to AUS - HAHA...wtf?! man you guys pump us aussies
If you achieve a good leverage ratio as described here http://roadstarclinic.com/content/view/89/95/ , and if the goal is to have the ratio somewhere around 14:1 to 12:1 as proposed in the article, then the "feel" should be good. To address the problems that SamH reports in his post above - it sounds like it could involve several issues. A few come to mind: 1) brake hoses - get new hoses, possibly the Spiegler type - http://www.spieglerusa.com/brake-line-kit-77.htm ; 2) get new bake pads; 3) align the calipers correctly; and 4) bleed the system and bleed it again and elevate the calipers above the MC and bleed 'em again. Also, did I mention... bleed the system?