Fork/Brake Upgrade for Early '80 R80 TIC?

[Todd]

Hi,

I'm guessing this has been discussed before but can't find it ... I'm looking for the simplest front fork/brake upgrade for an early 1980 R80TIC with spoke wheels and ATE calipers. Preferably stock BMW parts.

Can anyone point me to where it might have been discussed or documented already?

From the parts fiches, it looks like the slightly later 1980s Rs that came with twin pot Brembos used the same design of leading axle sliders, just cast for the Brembo brakes instead. The axles/spacers etc appear to be the same. I'm guessing that these are one starting point?

Can I just swop the sliders and start from there, either going with said Brembos, or working out an adapter for even later four post Brembos?

The bike already has a handlebar master cylinder and later T-junction under the tank.

The only thing that I have been warned is that, potentially (because I don't know what I am really dealing with, i.e. it may have been changed already) the TIC spoked wheels might interfere with some calipers ... I was told something about having to use a narrower spoked hub or going over to cast wheels?

Ideally, I'd like to do something like swop over to Brembo sliders, then use adapters for the Brembo 4 pot brakes ... may be they do or do not fit with spokes, I don't know. It looks a lot easier and a lot cheaper to make adapters for them than the ATE sliders. (I am aware of the r90x design kits, but I don't need radial brakes, nor could I justify the outlay involved).

Are there other feasible options, like going for R65 forks or sliders?

Just looking for a stock looking end result, not a custom bike.

Thanks.

[Rob Frankham]

I'm afraid this needs a lot more research and a realistic approach to what you want to achieve. A few things you need to take into consideration...

1) The Monoshock for stanchions (including the 'R series) are a different diameter to those on twinshock machines so the sliders from an 'R or any Monoshock bike will not work with the twinshock stanchions.

2) All of the Monoshock road models use an 18" wheel so, even if you could get the sliders to work, you couldn't get the twinshock front wheel to fit.

3) The sliders on the twinshock Brembo models won't work with the forks made for ATE calipers. The stanchions and internal parts are different.

About the only ways forward are:

1) source the complete forks from a later twinshock machine. Your spoked wheel may not fit... certainly BMW supplied a different spoked front wheel for the Post '80 machines. The fork tubes will fit the yokes (Triple Trees if you prefer) and things like mudguards and fork brace will fit. or....

2) Source a complete front end from a monoshock. This time you'll definitley have to replace everything including the fork Yokes (Triple Trees), mudguards and any other bits. I know the forks from a Mono will fit, not sure about an 'R. You will probably have difficulty sourcing a spoked wheel... the vast majority of Monoshock machines use 'Y' spoke wheels. or...

3) Go the whole hog and fit a front end from a completely different machine... but that's something you'd have to research yourself.

In conclusion, If you can't achieve what you want to with the original ATE brakes, it's a big job to make any real improvement.

Rob

[Todd]

I'm afraid this needs a lot more research and a realistic approach to what you want to achieve. A few things you need to take into consideration...

1) The Monoshock for stanchions ...

Thank you for your reply but just to be clear, I wasn't thinking of the monoshocks but, e.g. the later R-series twin shock bikes which use the same yokes but, for some reason, seem to have different part numbers for the tubes, i.e. 31421241655 (81) versus 31422000376 (pre-81). I think they went up from 1981 to 1984, see photo (not my bike). The intermediatory models that had leading axle fork, but Brembo brakes.

In the online parts fiche, they bundle in 1976-1985 together.

I'm guessing, however, that the monoshock bikes used the same head tube/steering stem/bearings though and, hence, a complete front end from one of them would fit on? (question) If they went up to 38.5 mm from 36 mm, then that's only 1.25mm bigger on each side which sounds like it would fit inside the fairing etc just fine.

Are the centre to centre dimensions the same?

r100rs.jpg (100.59 KiB) Viewed 626 times

[JohnT]

Screenshot_17-12-2025_154039_.jpeg (155.58 KiB) Viewed 598 times

This may help you search and identify suitable parts.
My old 1984 Ex Police R80 with twin Brembo brakes.

[Todd]

My old 1984 Ex Police R80 with twin Brembo brakes.

Thanks. Nice full front mudguard ... Yes, that's the set up basically. So far I've been told that they also did an R100TIC with spoked wheels for the Police too, although; a) they're rare ... if there's any original survivors left at all (9 licenced, 7 on SORN), and b) they shared a narrower hub than the ATE caliper version.

I'm wondering if going for a bigger rotor, better caliper, single sided brake might be the way forward, i.e. like an R80ST set up? Does fork twist perhaps become an issue ...

The R80ST uses the same fork sliders as the R65 and some R65s used to have double discs.

[Rob Frankham]

I'm afraid this needs a lot more research and a realistic approach to what you want to achieve. A few things you need to take into consideration...

1) The Monoshock for stanchions ...

Thank you for your reply but just to be clear, I wasn't thinking of the monoshocks but, e.g. the later R-series twin shock bikes which use the same yokes but, for some reason, seem to have different part numbers for the tubes, i.e. 31421241655 (81) versus 31422000376 (pre-81). I think they went up from 1981 to 1984, see photo (not my bike). The intermediatory models that had leading axle fork, but Brembo brakes.

In the online parts fiche, they bundle in 1976-1985 together.

I'm guessing, however, that the monoshock bikes used the same head tube/steering stem/bearings though and, hence, a complete front end from one of them would fit on? (question) If they went up to 38.5 mm from 36 mm, then that's only 1.25mm bigger on each side which sounds like it would fit inside the fairing etc just fine.

Are the centre to centre dimensions the same?


r100rs.jpg

Apologies, I haven't been clear in what I'm saying. I was trying to cover all options with special regard to bolt on mods using BMW parts. For clarity, when it comes to front forks, the marque can be split into four age defined groups (referring to road bikes with disc brakes)...

1) 1974 to 1980 (Model years). ATE swinging calipers, 19" front wheels.

2) 1981 to 1985 (Pre Mono). Brembo two piston calipers. 19" front wheels.

3) 1978 to 1985 (Pre Mono) R45/R65. Brembo or ATE two piston calipers (interchageable). 18" front wheels.

4) 1985 to 1995 Monoshock. Brembo two piston calipers. Completely changed front suspension based on that developed for the 'K series. 18" front wheels with completely different bearing and axle.

5) R100R and R80R to 1983 Marzochie front forks two piston Brembo Calipers. 18" front wheel.

6) R100R 1984/1985 Brembo four piston calipers.

In all cases, the forks legs (icluding sliders) are different both externally and in internal components. You can't intemix parts. Additionally, when you get to the 1985/86 change you need to change the fork yokes (and many other bits like mudguards and fork braces) as well as the wheel. The head bearings are common to all so it is possible to swap yokes without too much bother. A spoke front wheel for the Monoshock forks may be difficult to come by though.

In the context of your original post...

a) no, you can't just fit 'brembo' sliders to 'ATE' stanchions. You can, though, fit post '80 fork legs complete.

b) the four pot calipers used on the last couple of years of 'R model won't bolt up straight to the '80 to '85 twinshock forks. I've seen them fitted but it requires precision made adapters.

Rob

[Todd]

In all cases, the forks legs (icluding sliders) are different both externally and in internal components. You can't intemix parts.

According to the parts fiche, the fork tube or stanchion is 31421241655 (superseding 31429062419) and is found on the following vehicles:

• R 60, R 75 , R 80, /7, RT (76-85)   (04/1977 — 01/1985)
  R 65 GS, R 80 G/S, R 80 ST (80-92)   (05/1980 — 07/1987)
  R 100, /7, /T, CS, RS, RT, S (76-84)   (03/1976 — 11/1984)

The same goes for the internal dampener, spring, yokes etc (with the R45/65 listed on some parts). The shaft seals are the same. We know it's the same diameter.

As far as I can see, there's no reason why a late-1980s to 1984 twin shock slider cannot bolt straight on to an early-1980 fork tube. That would allow the twin pot Brembos to fit and then, as you suggest, an adapter to fit other calipers ... depending on clearance. You can see there's not much space between them.

s-l1600.jpg (293.72 KiB) Viewed 429 times

[Rob Frankham]

In all cases, the forks legs (icluding sliders) are different both externally and in internal components. You can't intemix parts.

According to the parts fiche, the fork tube or stanchion is 31421241655 (superseding 31429062419) and is found on the following vehicles:

• R 60, R 75 , R 80, /7, RT (76-85)   (04/1977 — 01/1985)
  R 65 GS, R 80 G/S, R 80 ST (80-92)   (05/1980 — 07/1987)
  R 100, /7, /T, CS, RS, RT, S (76-84)   (03/1976 — 11/1984)

The same goes for the internal dampener, spring, yokes etc (with the R45/65 listed on some parts). The shaft seals are the same. We know it's the same diameter.

As far as I can see, there's no reason why a late-1980s to 1984 twin shock slider cannot bolt straight on to an early-1980 fork tube. That would allow the twin pot Brembos to fit and then, as you suggest, an adapter to fit other calipers ... depending on clearance. You can see there's not much space between them.


s-l1600.jpg

I'm sorry, I have to disagree. I think you're misreading the Parts Fiche. You need to look at the actual diagram for the vehicle concerned to get the full picture. Below are to images 'snipped' from the BMW ETK system which give the full story.

a) ATE Forks.jpg (135.21 KiB) Viewed 411 times

a)Brembo forks.jpg (132.35 KiB) Viewed 411 times

You will see that the first image shows the number as 31 42 2 000 376 clealy markes 'Bis 09/80' translated 'before 09/80'. The second image shows 31 42 1 241 655 clearly marked 'Von 09/80'. translated 'From 09/80'. You can also see that the internals are very very different and similarly marked as 'before' or 'after 09/80'. In addition, although they aren't shown in these diagrams, the attachment of the damper valve at the bottom of the slider is quite different.

I'm afraid I have to re-iterate that you can't simply put Brembo sliders onto the earlier stanchions.

Rob

[Todd]

I think you're misreading the Parts Fiche.

I read, and copy and pasted accurately, from the Real OEM parts fiche, which I linked to above, i.e. the pages linked to from here.

Where is the link you are using?

Often, when relating to components, there are small changes that require different numbers, e.g. a black finish versus an alloy finish, reflector versus no reflector; that some dampener rods remained the same dimensions but had different sized/number of holes drilled in them, or that the RS received heavier springs to cope with the fairing, but that overall they remained the same.

Then you've got to check backwards to see if the changes in the numbers were just supercessions.

A 36mm slider, will obviously slip onto a 36mm tube, in a 36mm yoke. There were no significant differences in the way they bolted together until they dropped the leading axle forks.

[Rob Frankham]

I think you're misreading the Parts Fiche.

I read, and copy and pasted accurately, from the Real OEM parts fiche, which I linked to above, i.e. the pages linked to from here.

Where is the link you are using?

Often, when relating to components, there are small changes that require different numbers, e.g. a black finish versus an alloy finish, reflector versus no reflector; that some dampener rods remained the same dimensions but had different sized/number of holes drilled in them, or that the RS received heavier springs to cope with the fairing, but that overall they remained the same.

Then you've got to check backwards to see if the changes in the numbers were just supercessions.

A 36mm slider, will obviously slip onto a 36mm tube, in a 36mm yoke. There were no significant differences in the way they bolted together until they dropped the leading axle forks.

I'm working from the BMW electronic parts catalogue (EPC/ETK) (that is the official parts ordering catalogue issued by BMW to dealers). I have access to two old versions of this (2002 and 2006). There are no online links to that resource. I've cross checked the information with a contemporary BMW 'Auxiliary Catalogue' (Paper version of the physical BMW issued Fiches) dated 1981. All of which give the same information.

If I can say so, I think where you are going wrong is, when you look at Real OEM, you are seeing the parts Cross Reference page (e.g. https://www.realoem.com/bmw/enUS/partxr ... eries=2477) which gives the information you supply. This is a bit misleading as that line actually refers to the diagrams which are shared by a number of different models and years. If you follow the link at the end of the line on the page it will take you to the parts diagram and that gives the dating information... which agrees in this case, with the information I gave.

Real OEM and MaxBmw lists are actually copies of the BMW EPC licensed (presumably) for public use. They are, however, updated regularly and thus some of the information and parts details for older models like the airhead are falling off the system.

Rob