R65 Front Brake Pads

[Adrian]

Moto bins has 13mm master cylinders - approximately 300 dollars Australian.

Or, buy a 13mm rebuild kit and resleeve your master cylinder.

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Hi Tony - could you explain - just out of interest - why the 13mm will produce better braking instead of the 15mm. My guess is that the smaller the bore the greater the internal pressure to the system.
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Thanks ....

[Barry]

If you are going to spend money don't go for a 13mm with a single disc as it's still not good enough. BMW changed to 12mm in 81 for a reason. As Tony said they were ultra conservative with hydraulic ratios such that 11mm would be better still if such a thing was available.

The twin disc option is the best with stock parts.  Here's the maths:


Single disc

2 x36mm caliper pistons 2036 mm2
 
15mm Master cylinder   176.7 mm2

Ratio 11.52 which is truly terrible

13mm brings it up to 15.3 which is still poor

12mm brings it up to 18 which is ok but 20-25 is better


Twin disc

4 x36mm caliper pistons 4072 mm2

15mm Master cylinder   176.7 mm2

Ratio 23.04

[georgesgiralt]

On my R65 I've dual Brembo caliper. And because of no available parts a long time ago when my master cylinder failed, I put 16 mm bore master cylinder on it.
With SS brake lines, braking is good but you have to have very powerful hands to actuate the lever. My right hand is twice as big than the left one.
So I plan when this MC fail to put a smaller MC.I've been told that 14mmwill be perfect and like the feeling I have on my other bike.

[georgesgiralt]

Hi guys,
If you want to stop your bike efficiently, try this ....
https://www.r90xdesigns.com/shop

[Adrian]

Hi again - I'm going for a second disc. Motorworks have everything I need & I'm just waiting for a quote for all the parts.
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Thanks for all the advice 👍😉

[spiderbob]

I would be very interested in what you end up doing. I also have a 1984 R65. According to the vin number, it's an R65LS, but there is only a single front disc. I don't know the history of the bike, but I wouldn't mind going to two front discs.

[georgesgiralt]

Hello !
Some time ago ;-) BMW "offered" a kit to switch from single to dual discs on the R65. Searching for the kit may help listing and locating all parts needed for the conversion.
Maybe on RealOem

[Bob_Roller]

Here's what BMW had a retrofit kit for second disc .


https://www.realoem.com/bmw/enUS/showparts?id=0364-USA-01-1982-248-BMW-R65&diagId=34_0617

Not sure what you will be able to get as new old stock .

[Adrian]

I would be very interested in what you end up doing. I also have a 1984 R65. According to the vin number, it's an R65LS, but there is only a single front disc. I don't know the history of the bike, but I wouldn't mind going to two front discs.

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Hi there Spider Bob - I have taken the advice of an R65 rider on another forum who has made the conversion to dual disc. He has a 15mm mastercylinder also.
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He has had success with the conversion & is happy with the result. He has used braised lines - as have I on my single disc
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Others also have recommended the change & are happy with the result too.
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So I hope that helps. Everything is available from Motorworks in the UK 👌😉

[Tony Smith]

Hello !
Some time ago ;-) BMW "offered" a kit to switch from single to dual discs on the R65. Searching for the kit may help listing and locating all parts needed for the conversion.
Maybe on RealOem

You would be very lucky to find one and you may not be happy if you do.

The kit was targetted to the 78-80 models, my wife bought one for her 78 model.

The kit came with a new disc, the longer bolts needed the mount two discs to the hub, a hose to connect to the distributor fitted to early models and obviously a RHS ATE caliper and bolts.

She also got a 13mm "round" master cylinder, but I suspect she may have simply ordered that at the same time.

When I first rebuilt my 84 model I looked for a kit but was told one was never made for the 81-85 model. At the time (2013) there was at least one kit in stock for the earlier model, I passed as I didn't want the ATE caliper.

[Barry]

If the parts for a twin disc can't be found, another option is to go with a 12 mm master cylinder and a 38mm Brembo caliper which gives a ratio of 20.   Many people have fitted the 38mm Brembo and they are very reasonably priced.

[stubmw]

If the parts for a twin disc can't be found, another option is to go with a 12 mm master cylinder and a 38mm Brembo caliper which gives a ratio of 20.   Many people have fitted the 38mm Brembo and they are very reasonably priced.

Hi folks, haven't logged in for a while, always checking out the postings though!
Is the 38mm brembo caliper mentioned above a direct/same fit as original ATE , (fork legs, banjo etc.)? If so which models/years were they used on? I'm assuming parts are still available for them, is that correct. Thanks in advance.

[Barry]

The F08 38mm Brembo is a direct bolt on replacement and was used on later type 247 airheads from I think 81 onwards.  81 on R65's also used a Brembo but it was 36mm, the same size as the previous Ate. The F08 38mm was used by other makes so for example you will find them at Guzzi spares outlets. A big plus for Brembo vs Ate is the spares are much more widely available and half the price.

[stubmw]

Thanks for that info. From a quick scout around the net the some/most of the brembo 38mm seem to have threaded mounting holes, whereas  my R45 has the plain holes!

[Tony Smith]

Threaded mounting holes isa sign that the disc in question will NOT fit an  R65 as it will have a differing offset from earlier FO8 calipers.

What made the earlier brembo (and other) calipers used on bmw motorcycles different was that they were internally space door upset to the interchangeable on both cast and spoked wheels.

Once interchangeability between cast and spoked wheels ceased to be a concern (in BMW world this meant the advent of the k100) then the distance between the fork legs was greatly reduced and the calipers had a much larger offset internally.

A couple of years ago I posted photos comparing the offsets on 36mm are 65 calipers and the later 38mm k100 calipers when I was fitting a k100 front end to my r65. Those photos are probably still in the forum archive.

Correctly offset calipers can still be bought, Motobins periodically has them in stock at reasonable prices.

The later callipers can be used however they require you to either machine both the caliper and the fork leg mounts to space the caliper approximately 5 mm further away from the wheel hub or purchasing/manufacturing a suitable mount that negates the additional offset. There has been a seller on eBay for some years the selling such mounting kits for the vertes and Moto guzzis to allow them to mount the later model f08 calipers the adaptors will work equally well for a BMW.

My last comment relate to the 80 year calipers made under licence to brembo by BMW and fitted to early r65 motorcycles AND TO NO OTHERS.

There are only two things wrong with the atu calipers firstly that although made to a brembo licence they were made in so that brembo parts, including pad will not fit, and secondly a t e chose to use mild steel pistons that had been hard chromed. Over 30 years or so the hard Chrome wears and flakes off inevitably leading to a piston stuck in the caliper bore usually having taken out the seal in the process.

I have refurbished a relatively large number of 80 calipers, to do so I turn up stainless steel pistons and highly polished them and I use brembo caliper ceiling rings (which surprisingly do fit).. I also use an oversized round o-ring to replace the impossible to find square section o-ring used by a t e, the first calipers I refurbished are ow significantly more than 10 years old and have never spring a leak and as a consequence I have long since stopped worrying about my o-ring substitution.

The final modification I make to the ATE calipers is to allow than to use brembo disc pads which are very much cheaper then a t e pads. I do however make the point that unless you have a lathe and the skills to use one yourself this is a course of action that is simply not practicable..