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The brakelines on my '82 R100 are original. They still look almost new. There's no cracking, they're still soft and pliable, and I replace the fluid annually. It flushes out nice and clean and I don't see any little bits and pieces of anything in it but I'm still wondering if I should replace the lines. What do y'all think is the useful life of OEM reinforced rubber brakelines?

I would say it is time, if only for the peace of mind.
Rubber does deteriorate.

The old lines flex more with age and thus make your brakes feel more spongy. Replacing them with braided stainless lines will make you think the stainless lines make a huge difference, but actually replacing them with any new line will make them feel a lot better.

Even without obvious cracking, (synthetic) rubber degrades with time and age.

The question to ask yourself will be:
"Do I feel lucky ?"

Or more directly to the point –
How well do you value the capability of your antique MC to be able to STOP ?
That very same old MC that will carry your ass on today's roads, in today's traffic ?
And then, being limited by 29 year old brake system technology ?

Best case scenario will be a 30 year disadvantage ...

Maybe you will consider the prudence
of beginning with a system that will be at least as good as it can possibly be, eh ?

I was in the same position a year or so ago, with original rubber lines that were apparently in good order.
But a recurring thought of the front brake lever touching the handle bars coming into a hairpin bend overrode the nostalgic feeling of original parts.
I put black braided lines on.
Does my bike stop any quicker? No, although the lever is much firmer.
But at least my heart won't stop either, as a result of bursting an oe brake line.

ME 109 wrote: Does my bike stop any quicker? No, although the lever is much firmer.
But at least my heart won't stop either, as a result of bursting an oe brake line. :idea:

The performance differences noted above
may well be the subjective observations of an individual operator
rather than the confirmed and objective results of trial and experimentation ...

As ME 109 –
I would want my brakes to be every bit of all that they can possibly be !
A well functioning MC and calipers,
quality pads, flat rotors, dependable lines,
fresh clean fluid,
and NO air !

The ability to stop ASAP, without trauma or failure –
Can be just too critically important to ignore.

All agreed Vanzen, but can stock airhead brakes ever be anything like real brakes?
I've ridden some bikes with real brakes.
Apart from higher performance pads, my brakes are about as good as they'll get. I think.
New front mc, braided front lines upper and lowers, good discs, No air.
Well, the rear brake could do with some improvement. It is difficult to lock the rear wheel without the assistance of compression.

ME 109 wrote:All agreed Vanzen, but can stock airhead brakes ever be anything like real brakes?
I've ridden some bikes with real brakes.

Quick and easy answer: NO.

ME 109 wrote:Apart from higher performance pads, my brakes are about as good as they'll get. I think.
New front mc, braided front lines upper and lowers, good discs, No air.
Well, the rear brake could do with some improvement. It is difficult to lock the rear wheel without the assistance of compression.

Rear brakes will be virtually moot on pavement –
For example, the R12S has the worst rear brakes of any BMW I have ridden !
It is just too easy to lock that brake when the rear tire is hanging in mid air, eh ?
Conversely, the 12S's front brakes are nothing shy of SUPERB –
and this experience will play a significant part in my judgement of relative braking capability.

"As good as they can be" may be as good as it gets regarding airhead stock components.
Do demand that much from them !
And do always ride with the thought of the temporal limitations of the technology / hardware in mind !

There is one good thing about front brakes that aren't overly good.
I've never lost the front end to locking the wheel.

ME 109 wrote:There is one good thing about front brakes that aren't overly good.
I've never lost the front end to locking the wheel.

I did once. I had the oem 15mm mc, which I found 'grabby". Locked right up on me and down I went.
That was when I changed to a 13mm mc from the mono R80...more lever movement, but more progressive too.