Has anyone fitted a four piston caliper fron a R1100 to a K100. I reckon it would be a good upgrade but being a tightwad I don't want to spend till I find out if it fits.

They look like it but I am not sure and I cant even find a R caliper to borrow.

This came up once before and my take is to ask a question can you lock the front wheel under heavy braking with the current set-up?

If not than a change could be helpful, If you can then there is no benefit to increased braking since wheel tyre friction is the constant in any given braking scenario if you see what I mean and the brakes cannot affect that.

If you have ABS on the bike can you provoke the ABS to fire under heavy braking ? If so that is the limit because it has sensed a lock-up and released the brake momentarily.

Happy to discuss if anyone has a different view.
Regards,
K-BIKE

I've done it (from an R1100GS which are the same) but you also need the 20mm master cylinder as the puny, stock 13mm unit leaves a very soft feel even after careful removal of air bubbles with a proper bleed. Don't ask me how they did it with the Mystik and R100R's 13mm M/C, but with a K100 standard with two-pot Brembos and a 13mm M/C the swap isn't direct. You will also need to space the brake discs out about 8mm to align the four-pot cals. I made thin aluminium discs and drilled four holes in them for the mounting bolts. (Update, I actually made those spacers for some Suzuki discs I am using on another Y spoke BMW wheel on another bike...but the four-pot's mounting pads need a slight shave to sit right over the centre of the stock brake discs). In the end it was an exercise in frustration, the brakes felt spongy. I've ordered the 20mm M/C and K1100 throttle assembly, cable and lever and will report back when it's done. My reasons for doing it aren't so much that I can or want to lock the front wheel up but that the feel is so much more progressive from the four-pot cals. I'm going to radial tyres too as a part of a small brakes/suspension/wheels and tyres 'upgrade' over the next few months, so I reckon these mods accompany one another. Oh, that and the throttle bodies from a K1100 too! Rolling!

K Freak wrote:Has anyone fitted a four piston caliper fron a R1100 to a K100. I reckon it would be a good upgrade but being a tightwad I don't want to spend till I find out if it fits.

They look like it but I am not sure and I cant even find a R caliper to borrow.

I did mean to say Rear caliper can I claim a senior moment on that. But I am still a tightwad. I want to upgrade to the four piston due to towing a camper trailer which is the one in the avatar and it puts a lot more weight on the rear so I feel that I need something a bit better.



They are a fully floating caliper with four pots but I am not sure about the mounting bolt spacing and if the ABS sensor is in the same position.

Of course you meant the REAR caliper! LOL. Let's see if we can get someone who owns one of the above-mentioned 'bikes to drag out a ruler and give us some specs. Takers? The master cylinder on an R1100 is 12mm in diametre pushing pistons of 26/28mm x 2 and a K100 uses a 13mm version pushing a nicely sized pair of 38s....close enuf!?

Two Wheels Better wrote:I've ordered the 20mm M/C and K1100 throttle assembly, cable and lever and will report back when it's done.

Installing K1100 front Brakes on a non-ABS K100RT in the Tutorial section is my experience with fitting a K1100 throttle, MC and front caliper set.

I haven't upgraded the rear caliper yet, KFreak, so can't advise you there.

That's what I'm looking forward to and will have some K1100 TBs so the cable mod might not be necessary. Thanks for that excellent tutorial, Robmack.

@ K Freak if you only want extra brake force due to towing the trailer have you thought about electric brakes fitted to trailer?
cheers just a thought
Tony

Toto_jp wrote:@ K Freak if you only want extra brake force due to towing the trailer have you thought about electric brakes fitted to trailer?
cheers just a thought
Tony

The manufacturers of the electric brakes that are what you are thinking of (7 inch) tell you specifically not to use them on a motorcycle trailer.

I have been in the trailer industry for 28 years now (the last 3 only part time due to retirement) and what Dexter told me was absolutely terrifing at what has happened to towing bikes if the brakes do not apply exactly evenly. They will pull you down at low speed and have pulled bikes sideways so badly that the whole lot went down at speed. It is very difficult to adjust them exactly evenly because they dont work on a current that is necessarily even to both wheels. To put it mildly they are bad news and anybody that has a prang will more than likely get wiped by their insurance co. Dexter has made it abuntantly clear to anybody that buys from them that they are not to be used on a motorcycle trailer. I found about two years ago that they made them and investigated importing them as agent and they pulled the plug about two months into the negotiation saying that if I was going to use them on a bike trailer the deal was not on. Knowing electric brakes like I do when they explained what happens I am in agreement with Dexter 100%.

The best to use are override type with small dirt bike discs and the go kart calipers. I am currently working on Aluminium hubs with discs from a pit bike so I can market them.

I don't know if you are aware but I have just started selling a load sharing anti sway hitch for bike trailers and I am working on one that will work with override brakes. If you keep a look out you will see some adds appearing in the mags soon.

A K100RS trailer tower once told me with a straight face that all you really need is a long tongue.

"A K100RS trailer tower once told me with a straight face that all you really need is a long tongue"...to lick your wounds when you bite the black stuff?

What prompted me to make the coupling was that at the Ulysses Club AGM in 2010 at Albany there were 80 trailer/bike accidents while attending the AGM.

Some were just dumb. I won't tell names but two riders towing were both looking at a wedgetail eagle when they colided so not all by any means were the fault of the trailer but many could have been avoided if good towing gear had been available and used.

My coupling works so well that I have towed my camper at 140kph with a flat right tyre and did not even know.

I built some and had friends test them and one got a blowout on the rear of his FJR 1300 without even a problem and bought it to a stop. Common thing when that happens is to go bush and have a writeoff of the bike at least and many have had some serious injuries.

But of course the biggest safety factor when towing any trailer with any vehicle is a functioning brain.



Any how I will get of my soap box now.