The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: 67siia on April 07, 2015, 12:07:28 AM
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1979 R65. The problem: the brake lever is super hard to pull, I can only get about 5mm of movement at the lever. I did lots of reading here and decided to have a look. I removed the caliper and split them in half. The piston are rusted in the inside and I was not able to removed them from the caliper well stocked in there. I put new pads repacled the brake fluid, bled the systems and was able to get some good travel on the lever and THEN back to hard I'm not sure where to go from here. What new calipers would fit my bike? Can anyone provide some guidance?
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Hi there.
You have three choices - rebuild your ATE caliper, purchase a 2nd hand Brembo F08 or purchase a brand new Brembo (Grimeca) copy.
Of the three options, the 2nd hand Brembo will probably cost you the least, cunningly they used anodized aluminium for the pistons for a number of years and they tend to never get too stuck.
Brand new Grimeca pistons, which Motobins usually has in stock are around $100.
Our you could buy a rebuild kit for your ATE, have a machinist make new stainless steel pistons and rebuild your ATE.
P.S. I take in unwanted ATE calipers (covering the cost of posting them to me).
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Caliper pistons can be difficult to remove even if not seized. I always get the pistons out the easy way by removing the pads and pumping the brake lever to get them most of the way out before draining off the brake fluid. You inevitably have to hold one piston back to get the other to move. If you can still only get one out make sure it's the inner piston. Then split the halves and replace the O ring with a solid rubber disk, reassemble, fill with fluid and pump out the outer piston. Alternatives are Compressed air - potentially dangerous or pump them out with a grease gun - contamination and clean up issues. Which is why I prefer to use brake fluid.
The ATE pistons do rust badly on the inside and around the dust seal end but as long as the area of the piston in contact with the caliper seal is OK they can be cleaned up and re-used. Applying brake grease to the piston on reassembly, particularly the end under the dust seal helps to keep corrosion at bay. Stainless ones would be nice though.
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Others have said these are good but I have not needed them yet. http://etypeparts.myshopify.com/products/ate15-bmw1
They look like they are brass so that should take care of the corrosion problems.
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Many thanks for you helps guys.
Regarding the Brembo F08, is it a fit to the forks or would it require any modification? I saw this on good old eBay and wondering if it is the correct one to buy: http://pages.ebay.com/link/?nav=item.view&alt=web&id=351342714588
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Be sure to buy the caliper for the left side.
These guys are in your home state of Cali.
https://store.bevelheaven.com/Calipers-Front/
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Thank you all, I ordered the Brembo caliper from Bevel Heaven (thank you mr miller)...$138 for safety? NO PROBLEM.
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67siia... Did you mention the F08 was for a BMW Airhead?
Your bike's caliper mounts behind the fork lower rather than in front as the "Left Side" caliper was described in their catalog. To keep the bleed screw at the top of the caliper -so air can be fully bled out- and the metal brake tube positioned inside the bleed screw, I believe you'll need the Right Side listed caliper for correct positioning on the R65 BMW fork.
Please call these guys before they ship out to you. Confirm. And take a look at your bike's front end and compare how the mounting holes will mate to the fork lower.
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That was the smart way to go
You also have the benefit if now having a standard size caliper with a 38mm dia piston instead of the spacial size that BMW had made special for the R65. So if you ever rebuild the caliper you will need to know that to get the correct kit.
http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_115&products_id=591
You will notice less force needed to stop the front brake.
Also check the dia your master cyl to make sure somebody didn't stick one on there for a dual caliper set up. That can also make the brake feel hard
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Thanks for the follow up. I did communicate with Steve Allen before placing my order. He was very helpful. I hope we get it right. I sent him a picture of the ATE fitted on my bike.
67siia... Did you mention the F08 was for a BMW Airhead?
Your bike's caliper mounts behind the fork lower rather than in front as the "Left Side" caliper was described in their catalog. To keep the bleed screw at the top of the caliper -so air can be fully bled out- and the metal brake tube positioned inside the bleed screw, I believe you'll need the Right Side listed caliper for correct positioning on the R65 BMW fork.
Please call these guys before they ship out to you. Confirm. And take a look at your bike's front end and compare how the mounting holes will mate to the fork lower.
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A bit late but here is the update: new caliper installed, braking substantially improved yet, the pull on the lever remains a bit hard... I can live with that
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Regarding the hard lever pull, are you still using the 1979 vintage brake hose? Also, the piston in the master cylinder could also need a little love.
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A bit late but here is the update: new caliper installed, braking substantially improved yet, the pull on the lever remains a bit hard... I can live with that
Mines the same. The hard lever is simply due to the ratio of master cylinder piston area to caliper piston area. BMW were just too conservative although the 81 on bikes were a little better with a 12mm piston in the master cylinder instead of the 13mm which the earlier models have. If I ever need to replace or refurbish the master cylinder I will go down in size to 12 or 11mm. In the mean time the brakes are not bad for a 79 bike.
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Disk Brakes should have a Firm feel if the you don't have air in the system or a hose that swells under pressure.
What do you mean by "Hard" Does it take a lot of pressure to make it stop.
If so check your MC diameter
I put a 12mm master cyl with the F08 caliper and it still had a soft feel but stopped easily without excessive lever pressure
I didn't like the soft feel so I put a stainless steel brake line on it. Then it firmed up nicely. Some may call it "hard" put it still stopped with same amount of lever pressure
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I do not want to hijack the thread but since we are talking abut changing from Ate to Brembo calipers. I have dual front bakes (Ate) on my 81, can I get the dual calipers from the site above and just switch sides? This would be great.
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I do not want to hijack the thread but since we are talking abut changing from Ate to Brembo calipers. I have dual front bakes (Ate) on my 81, can I get the dual calipers from the site above and just switch sides? This would be great.
Call 'em up and ask as did our 67sila.
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I have only done the swap with the single disc set up.
But if I had a twin set up I would just get the standard F08's that I put on my single set up.
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I was asked to specify left or right side.... this leads me to believe you can buy both sides... contact them, they were very helpful
I do not want to hijack the thread but since we are talking abut changing from Ate to Brembo calipers. I have dual front bakes (Ate) on my 81, can I get the dual calipers from the site above and just switch sides? This would be great.