Fork/Brake Upgrade for Early '80 R80 TIC?

[Rob Frankham]

The only parts manuals issued by BMW are the parts fiches and the MaxBMW/RealOEM parts lists are nothing more or less than direct copies of that. Apart from the fact that the lists are not without errors in their own right, it has to be born in mind that they are intended solely for the use of spares departments in determining what parts to order for a given machine. Another frequent 'Gotcha' is that a listing produced in say 1990 might show different parts to that produced in say 1980 for the same machine. The parts will fit after a fashion but may require the substitution of other adjoining parts. BMW never intended for parts to be swapped between different machines outside their development programmes, even though parts supplied might be parts developed for later machines...

That being said, the BMW parts lists can give you an enormous amount of information about parts use and supersession although sometimes you need a masters in logic to actually work out exactly what is being said.

The best you can get is a copy of the parts lists issued within a couple of years of the manufacture of your bike. For a 'Pre '80 R80, that would be in the form of a Fiche (which is pretty useless unless you happen to have a Fiche reader) or the 'Beheflts Katalaog' (Auxiliary Catalogue) which is the paper version of the same information. Computerised lists didn't come in for some years... the earliest I have access to is 2002... and, even then, it's not simple. I have to run Windows XP in a virtual machine just to access it.

In general, the best information is to be gained by trawling the web and forums but bew aware that much of the information that comes up may not be reliable... the joys of loving old motorbikes...

Rob

[barryh]

the internal damping mechanism was changed quite significantly (and not for the better) to a design that was first use in R45/R65's in 1978.

What's the deal with the "knurled nut" .. photos show they are internally threaded, but the front hub is not. Are there just smooth, press fit ones for the 2/3 rib hubs? (I see the 4 rib hubs have threads on them).

Beyond the hipster/"cafe scramblers" types, has anyone tried lacing an 18" front rim to a bike to allow a wider range of tyre choices, e.g. 18 x 3.50, as it looks like I'm going to have to rebuild the wheel anyway.

Any difference between a 2.15 rim versus 1.85?

Thanks.

I'm not familiar with the spoked wheels in any great detail. It might be best to identify the part by posting a parts fiche diagram.

An 18" front rim is going to lower the bike and alter the steering geometry so you really do want to hear from someone that's already done this. If you search all the airhead forums I'm sure someone will have done it. An 18" R65 wheel could be made to fit but the vast majority are snowflakes rather than spoked and the hub width is narrower.

A 3.25 tyre on a 1.85 rim is on the limit of what that rim size will accept so the wider 2.15 rim would allow for a wider front tyre if it will physically fit. A wider front tyre would go some way towards restoring the correct tyre diameter but it will also slow the steering.

[Todd]

The only parts manuals issued by BMW are the parts fiches and the MaxBMW/RealOEM parts lists are nothing more or less than direct copies of that

Yeah, I don't know what's gone wrong in that department but they are 'way' wrong in these departments ... and I suspect others that I haven't discovered yet (electrics). If I can leave a trail of breadcrumbs for anyone else following, it will be to highlight that.

In fact, they're garbage. Worse than incomplete, quite misleading.

Perhaps part of it is because the USA didn't get many/any TICs.

Folks say the CS had the spoked wheels to match ... but it looks like they use the 4 rib hubs, not the 2 ribbed hubs the UK bikes had.

The best you can get is a copy of the parts lists issued within a couple of years of the manufacture of your bike. For a 'Pre '80 R80, that would be in the form of a Fiche (which is pretty useless unless you happen to have a Fiche reader) or the 'Beheflts Katalaog' (Auxiliary Catalogue) which is the paper version of the same information.

Funnily enough, you can pick up fiche readers for free, if you can find the fiches any more. In a way, I actually prefer them to computerised system. Primarily because you don't have to turn a computer on for them to work! One button, one bulb ... quick to navigate, and no oily keyboards to try and clean. I had to passed on a complete collection for vintage HDs once because the club couldn't see the sense in them, but still kept a box full of VHS service tapes.

They'll regret it as one by one all the online websites will be obsoleted too.

And, yes, I'm guessing they must have done auxiliary catalogues just for the TIC models ... I wonder if any of the old cop garages still have them in a box somewhere?

[Todd]

I'm not familiar with the spoked wheels in any great detail. It might be best to identify the part by posting a parts fiche diagram.

What they call the "knurled nuts" (KN) are really just chrome caps that fit on the outside of the dust seal in hub. The drawings show them ... but don't show different hubs. On some hubs the boss (?) that holds the bearing and seal is threaded, as is the KN (part 6), it also have 4 holes to allow it to be tightened/untightened. Part 4 is a top hat spacer and I've no idea if they are supposed to be the same each side as the hub came without one.

The two rib and later 4 rib hubs aren't threaded though.

Note for Rob; you see, this drawing is incomplete again. Not only for the different hubs but also omitting the numbers for the wedding band and spacers require to get the pre-tensioning on the tapper roller bearings correct.

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hub-cap.jpg (43.82 KiB) Viewed 219 times

An 18" front rim is going to lower the bike and alter the steering geometry so you really do want to hear from someone that's already done this. If you search all the airhead forums I'm sure someone will have done it. An 18" R65 wheel could be made to fit but the vast majority are snowflakes rather than spoked and the hub width is narrower.

A 3.25 tyre on a 1.85 rim is on the limit of what that rim size will accept so the wider 2.15 rim would allow for a wider front tyre if it will physically fit. A wider front tyre would go some way towards restoring the correct tyre diameter

Yup, that's what I'm thinking, e.g. the an 18" front wheel would be 0.50" lower, but a 3.50" tyre would be 0.25" higher (in theory), so only 0.25" of a difference. Not a lot in comparison to saggy forks, probably not at all if one has new stiffer fork springs? Probably less then if someone stuck a 90% ratio tyre on.

[Todd]

Seems I can only upload 3 images at a time. Here's the threaded 4 rib hub, an unthreaded two rib hub which came with a 19" rim, and an unthreaded three rib hub which, allegedly, is unique to R80ST. May be the two rib hub is unique to TIC models with Brembo brakes? (I don't know, no fiche, no manual says).

The 2, 3, and 4 rib hubs are all different thicknesses disc face to disc face, so must either have different dished discs which ... again ... isn't shown in the parts fiches!

The 2 rib measures up as 38mm.

From another forum;

The 3 rib measures up as 42mm
The 4 rib measures up as 52mm (possibly same as snowflakes)

Apparently there may be issues relating to spoke hole alignment if swopping from 19" to 18" ... so more joy working that out!

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two-rib.JPG (476.94 KiB) Viewed 217 times

3ribhub.jpg (426.54 KiB) Viewed 217 times

[Todd]

I forget ... did we work out whether the ultimate manner of holding together the two fork styles, i.e. ATE and Brembo, were similar?

Putting aside the minor changes in the stanchions and dampers, is the Allen bolt at the bottom of the Brembos the same diameter as the internal threaded part of the ATE forks?

Here's an ATE takeapart ... Youtube link. A good education in WHY to service one's forks!

Can't find a Brembo takeapart ...