Been slowly improving bits on this sidecar combination but need better brakes. The linked foot brake working the near side front and rear discs is good, but the offside front brake is wooden and inefficient. I like the look of the Nissin front master cylinder that was fitted by the previous owner but have been told that it’s 14mm barrel is unsuitable for operating one brake calliper, and that I’d be better with an 11mm brake master cylinder. my question is whether I’d be better delinking the brakes to have the current Nissin operate both front brake discs (if that’s viable) or, source a smaller 11mm brake master cylinder; which I’m struggling to find. Anyone got experience of an upgrade or solution?
Hi Godfrey
I had a SP1000 / Watsonian Monza Combo a few years back and whilst i agree with you about the Front R/H brake being a little wooden, the Linked Brake i found to be really handy allowing you to stomp on the brakes and keep full control of your hands so i would seriously suggest NOT delinking the brakes.
A 13mm Master Cylinder is about the correct ration for one P8 Caliper and even with the Brembo PS12 std M/Cylinder they are rather wooden. Do not go to a 11mm Master as that is not big enough!!!
A couple of suggestions would be to try a Brembo P9 Caliper (larger Pistons), if you can find one! or a BMW caliper from the R1150 Series of machine. These are almost a direct replacement and are 4 pot so with the 13mm master would give you a better ratio or you could try the Brembo P4 30/34 Caliper. Again 4 pot but not so easy to fit!
Persevere with it as when you get used to a combo they are great fun. I stupidly sold mine and have regretted it ever since.
Regards, Nik
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Hey Nik, thanks for the detailed reply!
I agree that the linked front/rear brake and sizeable footpedal is a boon and would be very reluctant to change the set up. I’ve just edited the original post as the Nissin has a 14mm barrel and not a 13mm as I suggested.
Are you suggesting that the front caliper off a R1150 BMW has the same mount spacing?
Ah yes, a 14mm Master would be very wooden. If you revert back to a PS12, the diameter of which is 12.7mm (i think!) its 12. something anyway! and the std fitment, you may find it acceptable???
Yes, the BMW R1150 Caliper has the same mount spacing as a P8 Caliper, but the holes are threaded so you would need to drill them out. Other than that, its a straight fit!
Good luck and enjoy, Nik
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Cheers Nik. I’ve actually just bought a right and a left from a R1150r secondhand from a chap to try this following your kind advice. I actually have a R1150r in the shed but didn’t want to dismantle it. I did note that the threaded section needs a drill put through it, and will update this post as I progress on fitting them once they arrive.
Now I’m wondering what rear master cylinder upgrade might be necessary to keep the linked brakes but utilise the spare BMW brake caliper on the other near side front disc?
I’ll have to shave off the BMW logo from the outer face too😀
You could also consider using linked one for front/sidecar or rear/sidecar. Friend of mine uses such a setup and he’s happy with it. I am into small block only so I am talking about P-05 pots I believe, but 11mm was a right move after wooden feel by Honda CX500 master. If you don’t want to go into sidecar wheel braking, I can share some advice from airheads: as long as I remember, a master 15mm which is supposed to work with twin disc front, works perfectly with 4-pot 1100 caliper - that caliper has slightly bigger piston area than older P-08. So, possibly staying with your 14mm Nissin and switching to 4-pot beemer one will sort things out. Or - stay with your classic look pot, but go down to 13mm master, as single disc BMs did.
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Unfortunately the Steib sidecar chassis won’t take a caliper carrier without a fair bit of work. This by completely re-doing the suspension - so I’m concentrating mainly on the handlebar levered offside front brake at the moment so that it at least stops more quickly and without the effort presently needed.
The second hand calipers from an R1150 came today.
Unfortunately the mounting bolts widths are way out from the ones on my Guzzi. 66 mm apart for the BMW as against 110 mm for the ones on my T3 derived Moto Guzzi. The other issue is that to bore out the BMW threaded mounting holes to accommodate the Guzzi mounting bolts, I would be dubious over it having adequate remaining material to take the braking forces.
Either I have different brake calipers to the standard T3 (P8?) Guzzi ones or it’s a different BMW brake caliper that I require.
Any ideas?
Don’t loose hope. You’re already away from original with that sort of forks; here is the picture of my R100GS, where I decided to use factory wheel, but with much bigger disc - and all is hanging on entirely different fork from DR-Z 400. Yet the outcome is to say least - satisfactory! Also other pic of my mate’s GS with factory fork, hence o/s disc layout. As you can see, a bit of cardboard design job and all can be sorted.
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Thats the wrong Caliper! I guess i should have been more specific. The Caliper shown in ‘adamigo’ picture is the correct one!
Thank you for your input.
Are those brake calipers in your pictures off an 1100 BMW rather than the later R1150r BMW?
Are they front brake calipers from a K 1100 BMW or an R or GS?
Do you reckon that the original brake discs could be used rather than upgrading to thinner stainless discs?
Are these the ones in your pictures that share the same mounting spacing as the Tonti front calipers?
just asked a friend with an R850 (that appears to share the same calipers as the R1100) if these are what I’m after regarding the mount spacing to which he’s replied in the affirmative, so will chase one down.
I do my questioning too, so hopefully will come back here tomorrow as well. Calipers are defo R1100GS, possibly others too.
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The one i used were from a BMW R1150 GS
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Cheers both.
Now ordered two seemingly good front R1100 ones. The left near side extra one on the chance that it might work with the existing rear master cylinder. Or, that I might have to source a larger alternative master cylinder for it to work acceptably.
Seems that the 1150 GS and earlier 1100 series are similar. My mistake was thinking that R1150 BMW calipers were the same as would have been used on the 1150 GS.
Good news and bad news. 1100GS caliper shares same holes spacing, but watch out: my biking friend who is an engineer with degree in hydraulics says, those 4-pot ones are 5 percent weaker due to total piston area, than P-08, standard ones. He says there’s no point what-so-ever to do such conversion! It all only looks better… You may turn your eye to Ducati/Cagiva/anything modern-ish Italian calipers, which I find extremely efficient, and with some abovementioned carboard design work you can get where you want. There are two types on,say, older Ducatis: one of them with 65 mm space between the holes, other one with 40, I can’t remember more but you’ll find them cheap on eBay, all golden ones. Not sure if Breva 750 uses something similar?
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I’ll try the handlebar levered off side front one operated by the Nissin 14 mm master cylinder as the present set up couldn’t be much worse. I understand it should be able to be changed back if unsatisfactory.
I’ll report back after the calipers arrive.
Calipers arrived so did some measurements this morning. Mounting spacing is good, but with the leading link forks the carrier plate needed a bit filed off. I will also need to centralise the caliper by removing or reducing a spacer on the carrier plate.
I now understand the maths and ratios relating to the master cylinder and the brake caliper to acquire decent feel and better brakes. I’m told the necessary ratios are between 20/1 (hard lever) and 30/1 (softer/more progressive) but still usable and workable. Anything below 20/1 being too wooden and unusable, and anything higher resulting in the lever being too soft, having too much travel or having no brakes.
My present 2 pot caliper has X 2 33mm diameter pistons with a combined swept area of 1710 mm. The master cylinder’s 14 mm bore gives a swept area of 154 mm.
Dividing 1710 by 154 gives a ratio of 11.10/1, so is practically unusable and explains my desire for improvement. I struggled to lock up the wheel on gravel using the hand lever.
The master cylinder is newish and the cost of upgrading the calipers with the larger pistoned traditional looking ones is high, so the £80 for two uncorroded and good looking 4 pot Brembos seemed a better option.
Using the new to me 4 pot Brembo with it’s total swept area of 3424 divided by the same 14mm Nissin master cylinder’s swept area of 154 will give me a vastly improved ratio of 22.23/1
Maybe on the firm side but perhaps a bonus with the added weight of the sidecar.
I’ll update my progress as time allows.
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Hold on, you use P-05 caliper, 32mm dia? The one used on all the small block Guzzis??? I was sure Big block employed P-08s, with 48mm dia. And then both total areas, big 2-pot and 4-pot, are comparable.
Nope. The swept area of one of the 2 pot Brembos on my bike are mentioned in my earlier post. The 4 pot replacements have around double the swept area. These were the front brakes fitted to the bike and sidecar when I bought it in the spring earlier this year.
They are rubbish compared to my G5 V1000 brakes, and the reason why I’m looking for more stopping power.
I’m also going to try to fit the other good 4 pot Brembo to the N/S - but that might require a larger rear master cylinder as it’s presently linked to the rear brake.