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Disc Brake "Upgrade" Boxermetal.com

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bradley martin
(@dartnmartn)
Active Member

Hey group.  Someone, from one of my now many BMW airhead sources, mentioned an upgrade to the wonderful caliper/disc arrangement we of 74-80 vintage airheads are blessed with.

R90X BIG BRAKE KIT – Boxer Metal

Boxermetal.com Has this kit.  Replaces stock rotor with a floating 320mm from a Ducati 1098.  Replaces the caliper with a 4 pot off a BMW S1000R.  Includes this insert which attaches to the current caliper pivot point but provides mounting points for the radial caliper.  Looks like some removal of some of the casting might be required.  (site sez "basic tools only required", so hacksaw maybe?)

I've done everything suggested on this site and others to get the most out of the original design.  I've taken it to a BMW guy who has been twisting wrenches on these things for 40 years.  He said "Yup" that's about all you are going to get.

I find the braking on my 78' R80/7 almost silly compared with the other bikes in my garage.

so.... Before I shell out hundreds of $$$ and carve up my fork leg....

Anyone done this upgrade?  Was it a major improvement?  Is it a 3 finger braker now? (As opposed to four finger max pull and boot heels dug into the tarmac just to assist? still only providing a modest deceleration experience....)

Any input would be great.

Quote
Topic starter Posted : 01/20/2022 12:47
Richard Whatley
(@wobbly)
Member Moderator

I've been a big fan of the full floating discs for some time. EBC makes them to fit the stock Airhead wheels/brakes.

To get the full benefit, you'll also want to fit all new modern "stainless steel" brake hoses.

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

ReplyQuote
Posted : 01/21/2022 04:44
bradley martin
(@dartnmartn)
Active Member

@wobbly

So did you stay with the stock caliper and just upgraded the discs?

This kit provides mounting for a four-pot caliper from a modern sportbike.

Wondering if it is worth the $$, effort and "Irreversability"...?

ReplyQuote
Topic starter Posted : 01/21/2022 11:13
Richard Whatley
(@wobbly)
Member Moderator

This "kit" is proabably not complete. They may want you to find your own calipers, and wrecked S-bikes aren't that numerous. So you've got the high price of the kit, plus a lot of extras to hunt up. And you couldn't stop half-way and use the new Ducati rotors with the old calipers while you wait. Don't get me wrong, it's an ingenious kit and it would definitely improve the braking, but it would not improve the resale value by even 1/2 of the investment. And it's overkill because you are fitting 150MPH brakes to a 90MPH bike.

Think about it. You'd get more realistic results, at about $1000 lower cost, by simply buying a complete 1980 to 1985 R100 front end off Ebay. And it would remain 'stock' looking for the next buyer. Those are the pitfalls I see.

Here are the steps I have taken with several Airheads. In order of preference they are:

  1. First and foremost, install some new brake pads. Pads age. Old pads absorb oils. New pad compounds come out all the time. And don't buy BMW brake pads either. Buy them from a company that makes nothing but brake parts, like EBC. I bet most Airhead owners are driving around with 20 year old pads, and don't even think about it. About $25.
  2. A full set of updated steel reinforced brake hoses. OEM brake hoses are prone to failure anyway, so modern hoses will be proactive general maintenance. These alone will be good for a 10-15% improvement in braking efficiency. About $80. Read This Article Here.
  3. You should also take the time to scrub out the calipers and brake master cylinder. Items #2 and 3 will necessitate new brake fluid. BMW recommends this as annual maintenance with DOT4. Regular replacement of DOT4 is hugely important, but often forgotten. [If dealing with DOT4 every 12 to 24 months is too much for an infrequently ridden classic, then consider a swap to 'DOT5 Silicone' while everything is apart and clean. This type fluid is good for 10+ years.] About $5.
  4. Brake master cylinder choices: A. Use the stock, cleaned 17mm brake m/c, or... B. Have your present 17mm m/c sleeved to 13mm, or... C. Convert to the handlebar mounted m/c. (Option C is preferable for maximum braking because it removes the "compliance" of the cable and mechanism, which itself causes a portion of the spongy feel.)
  5. Lastly fit a set of full-floating EBC rotors. These vastly improve the response time of the braking and have a much better rotor material for heavy stopping requirements. These, combined with all the above, will be good for another 15% improvement in braking efficiency. (The great thing here is that these are the same for ATE or Brembo brake systems. So if you sell your /6 or /7, you can move them to your new model Airhead.) About $290 each.

Is the single-acting, single-piston ATE "the best"? No way!! But it can be vastly improved with common updates from modern components. And, these updates can be done in 'stages' to spread out the work and/or dollar investment.

Hope this helps.

This post was modified 6 months ago 2 times by Richard Whatley

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

ReplyQuote
Posted : 01/22/2022 07:42
bradley martin
(@dartnmartn)
Active Member

@wobbly 

Thanks for the reply!

The "Kit" should I decide to go that route is $250.  A rotor off ebay... $125+?  A caliper off of an S1000...  Saw one for $150.  Saw lots of pairs for under $300.  Of course, I only need one and they might need a rebuild and new pads too.  I think I have a steel brake line in the pile-o-stuff that will work.  I saw a single disc front end for a /7 for $130 (all these prices are +/- ??? and then pile on shipping on all of them too).

As for 150mph brakes on a 90mph bike.  OH YEAH!  All day long baby!

As for resale.  Not really important...  I'll be dead or uncaring when this bike leaves my garage.  Plus... if I save all the stock bits (fork leg issue not withstanding) the next owner could put it back to stock.  Or chop it up and "Bob" the crap out of it.

Putting a late model front end on...  Just throwing too much money at the issue.  Dual disc front end off eBay $$$?  another rotor on the front. Then a resleeved or new master cylinder (twin disc set up is a different diameter than the single disc) or find a right-side throttle/switch assembly and, dink around with all the wiring and THEN how far am I from an original unmolested bike?  For whatever an unmolested bike may be worth...whenever umpty years down the road =) ...?

So... If I do it and it sucks or is no better than stock, I'm $500-$600 ish out of pocket.  Could probably get my Rotor and caliper funds back reselling them on eBay.  Of course, my $250 kit cost would be gone cuz all you airhead guys will be laughing your a*** off that I got sucked in on this boondoggle.  And of course, I'm $130-ish away from returning it to its current, pathetic condition. (Reverting to a non-altered eBay fork leg)

If it is MARVELOUS, I now have a bike that stops and is gobs safer than riding around on the vintage bits.  I COULD go ahead and buy the eBay fork leg as a just in case.  So, someone in 60 years doesn't have to say....  "What IDIOT would chop off the brake mounting on this timeless classic!???"

I have contacted The Kit company, twice.  Got a reply saying it will fit my ride (78' R80/7).  Got no reply yet on the "irreversibility" issues.  Or how much better in THEIR opinion is this set up, REALLY!  Or anyone's "Review".

As for the status of the current brakes.  New sleeved master cylinder. and rebuild kit.  New cable from lever to M'cylinder.  New stainless steel brake line.  New pads.  Obviously new juice and tons of bleeding brake exercises to get every freaking last bubble out.  Couple hundred miles of "Bedding in".  So, items #1, #2 and #3 from your note have been addressed.

As for #4, I have a 14mm Mastrer cylinder.  Converting to a "Conventional" handlebar mounted master cylinder starts knocking over lots of dominos in the controls department.  Basically, junking the Rt handlebar stuff.  starter button, turn signal, kill switch and replacing with ???.

still waiting for the kit company's reply.

ReplyQuote
Topic starter Posted : 01/24/2022 11:46
bradley martin
(@dartnmartn)
Active Member

I've have chosen to purchase this kit.

Before I take things apart, and hack up my left fork leg, I'm going to measure several 50-0mph stops.  Front brake only.  After the "Upgrade" I'll do the same.  Results will be posted here!  Stay tuned.....

ReplyQuote
Topic starter Posted : 02/01/2022 13:12
Richard Whatley
(@wobbly)
Member Moderator

That will NOT be an "apples-to-apples" comparison. You won't be telling yourself anything useful.

First you should rebuild your master cylinder, then fit all new steel-reinforced flexible brake hoses, then new brake pads, with all new brake fluid installed and bled correctly. Then adjust the ATE calipers per the WS manual. Then you'll have something to compare.

 

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

ReplyQuote
Posted : 02/02/2022 04:53
Frank Jarrell
(@frankj)
Active Member

The web site for the manufacturer is < https://www.r90xdesigns.com/>. This was discussed on the Airhead email list about a month ago. Most with experience felt it was an worthwhile upgrade. I have no direct experience. He has a kit on his site with a new rotor. (more money) I think some of the increased breaking comes from larger Dia rotor. (bigger rotor means more torque other things being equal.) You will need to procure your own caliper, hoses, and pads.

One suggested that you rebuild the front shocks and carefully examine your fork tubes to handle the increased breaking.

This post was modified 5 months ago by Frank Jarrell
ReplyQuote
Posted : 02/07/2022 12:27
bradley martin
(@dartnmartn)
Active Member

Got the kit in the mail today.

Richard, as for your reply on 2/2.  All those items have been addressed as per my post on 1/24.  New everything, including steel lines and all work checked by an expert.  In my opinion, the brakes are still terrible. So, I bought the kit and received what looks like some nice stuff.  Will know more when I go to mount it!  Can't do my brake test as there is still a fair amount of snow on the ground here in Indiana.

Will post test results and the efforts along the way to the installation of this kit.

ReplyQuote
Topic starter Posted : 02/09/2022 14:44
bradley martin
(@dartnmartn)
Active Member

Previous reply showed all the components received in the kit.

This picture shows the piece that will replace the Stock caliper pivot bracket and provide mounting for the (4) pot brembo caliper.

You can kind of see how the removal of some of the OEM casting will be required.

ReplyQuote
Topic starter Posted : 02/09/2022 14:48
bradley martin
(@dartnmartn)
Active Member

This picture shows the part that will support the Ducati 320mm rotor.  It bolts to the wheel, and the rotor bolts to this.  Of course, the stock rotor is put into "storage" in case all this is a miserable failure!  And I'll have to buy another left front fork leg!  Now I'm off to find a BMW S1000RR left brake caliper.  And a Ducati rotor.  and a steel brake line....

ReplyQuote
Topic starter Posted : 02/09/2022 14:52
bradley martin
(@dartnmartn)
Active Member

@frankj

Frank.  What is the Airhead email list?  I'm diving in on this, but would love to hear any tips if anyone else has tried it.

ReplyQuote
Topic starter Posted : 02/09/2022 15:00
Frank Jarrell
(@frankj)
Active Member

@dartnmartn 

The Airhead email list is primarily a list for technical discussions with a few diversions. It is not in anyway associated with the Airhead Beemer Club although many club members participate in both. You read about it and subscribe to it here:

https://lists.micapeak.com/mailman/listinfo/airheads

 

[Mods edited for clarity]

This post was modified 5 months ago 2 times by Richard Whatley
ReplyQuote
Posted : 02/13/2022 15:33
bradley martin
(@dartnmartn)
Active Member

More news on the Big Brake "Upgrade".

Sourced a pair of Ducati rotors ($150) and a pair of S100RR calipers for $150.  Cut up the fork leg so the bits bolt up, and they did quite nicely!  I still have to source some brake pads and a brake line.  Hopefully SOMEONE on eBay will want the 2 right hand parts!

Stopping distances were measured.... sort of....  It was not as scientific as I would prefer (hard to hold a steady 50mph, slam on the brakes at the same spot, with the same ferocity and a 25mph tailwind.)  But in the end, I got 5 or 6 sorta repeatable stops.

50mph to zero.  Front brake only.

somewhere between 102 and 122 feet.

I will be repeating this test.  Not only with my "New" brake setup but with my 2014 Yamaha FZ1.

Attached is a picture of the dry fit up of all the bits.

ReplyQuote
Topic starter Posted : 03/01/2022 11:09
bradley martin
(@dartnmartn)
Active Member

OK, this is hopefully the "Next to Last Chapter" in this saga.

All the components arrived, everything bolted right up.

Bled the brakes in a FRACTION of the time of the OE caliper.  (this setup does retain the under-tank master cylinder)

Took it out for a spin...  OH BABY!  Just like real live brakes!  A two finger squeeze would probably slide the front wheel if I was silly enough to try.  A GIANT improvement.

Only thing left, is a go at the "Test Track" to re-create the 50mph - zero stopping distances.

Recap.

BoxerMetal.com Big brake kit
Ducati 1098 rotor
Brembo caliper off a pre-17 BMW S1000rr
Speigler Steel brake line
EBC pads

This post was modified 4 months ago by bradley martin
ReplyQuote
Topic starter Posted : 03/11/2022 16:09
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