E.Marquez

The VTR1000F caliper is mounted above the rear axle and slightly forward


With the impending swing arm MOD I have coming up (900r brace) and the need to address the caliber bracket swing arm mount as part of that MOD.. I'm thinking about changing up the entire rear brake setup..
Performance? no not really I ask very little but feel and feedback from my rear brake. Just that if I have to source a caliper bracket (900r) and cut / re weld the bracket guide on the swing arm.. the opportunity to do something a little different is here.


The current crop of go fast bikes from all 3 big names use a top and forward mounted rear caliper..

WHY?

What advantage is that vs a lower and forward mount location?
ZX636

Triumph

ZRX1200

Others

Or put another way.. what are the disadvantages of the lower mounted rear brake?

I can see it taking more abuse from road debris.. or road conditioning chemicals if used in your area. Perhaps that in itself is the reason, damaged finishes, corroded sliders, seals damaged,,ect.

HRC has used the under / forward mounted rear caliper


Thoughts?

98VTRrider

I'm considering a low slung rear caliper for my race bike next year. I want to find something really tiny and light, and make a bracket to move it to the bottom. (I NEVER use the rear brake on my race bike)

I think one thing to keep in mind, the bleed valve needs to be in the correct position to be able to bleed it correctly. If you take a normally top mounted caliper, and spin it around to under the swingarm, the valve may not be in a position to work.. You could always remove the caliper and bleed it unmounted while holding it in the correct orientation maybe.

E.Marquez

Thanks..

I normally remove calipers and or MC to get the best angle for bleeding air.. so I did consider that..

As well as a Brembo rear caliper designed for under mounting are only $93.. so likely would just use that and a modified or custom bracket.

Then... assuming I do this..
I can make a bracket that uses the stock swing arm guide like what is done in the CRB1000 or RC51 kits out there

Jack Flash

The advantage may not necessarily be performance as much as workability. I know, after having changed tires/brake pads/etc. on the rear of many different types/brands of motorcycle, it ha been a charm to do so on lower mounted brake calipers.
If it's only tire you just roll it out with caliper still on may times. If you have a top mounted caliper, then it's a must to remove it.
That's my take on the WHY, IMHO.

bmidd

I have never removed a rear caliper to change a rear tire.

bbancsov

It should just "fall" if you pull the axle and the tire out, i am also contemplating moving the rear caliper. I just welded on a 900rr brace but not yet welded the caliper re-mount bracket so we'll see what happens.

E.Marquez

Really, then how do you get the tire past the caliper, as it will not fit.

either the caliper has to come off the mount, or the mount has to come off the swing arm....

Or you run some ridiculously skinny tires

Jack Flash

Erik, very interested in seeing what final direction you will be taking. Be sure to post some pics
please.

bmidd

Have never changed a tire on this bike yet.

E.Marquez

Ahh, ok then, thanks for your technical input on this thread.. most helpful

The good news for you then is you learned something you did not know and can be prepared for it when you do change a tire on the bike we are discussing here.

7moore7

Wait, are you talking about removing the caliper from the mount that slides onto the swingarm (#5)? When I remove/replace my rear tire, I don't take anything off. The whole rear brake assembly slides out (#8), but I don't undo any bolts other than the axle...

REAR BRAKE CALIPER

kenmoore

After having looked at the pics of other bikes I feel that the underslung calipers are monted there so as to clear the swingarm without having a huge bracket to hang the caliper on.

In most cases the underslung bracket probably fits other models in the manufacturers range and it has been utilised to save money.

i have seen a picture of an underslung rear caliper on a Hawk somewhere and it also had an adjustable torque rod along with a modified swing arm that used the brace from an early R1

E.Marquez

Thats the point... how ever you do it, the caliper is coming off from its normally mounted position when you wish to remove the rear wheel

7moore7

Ah I jumped the gun. I somehow missed this post

Jack Flash

Often wonder why we bother....

bmidd

Because people come from a wide and varied background of motorcycling I imagine. And my last 5 Yamaha's didn't require removing a caliper to remove a rear wheel every 2000 miles to install a tire. This will be the first bike I have owned in the past decade that I will have to remove a caliper to change a tire.

7moore7

I was confused at first too because I didn't really consider the standard VTR wheel removal method to include "removing" the caliper. It sort of slides off with the rear tire still attached to the mount assembly. So it does come off, but you don't loosen bolts or anything like that.

But if an underslung caliper setup makes even this unnecessary, I could see it as a nice bonus (or even the main reason) for going that route by manufacturers. As often as motorcycles wheels are changed, especially race bikes, it seems a viable expenditure of energy on the OEM to move it to make less hassle.

My first guess was that there was possibly a physical advantage to the brake forces "pulling" on the swingarm from the bottom rather than "pushing" on it from the top. Maybe less chatter or something. Or even physical restrictions with many swing arm shapes and braces? Lower COG maybe...

Or maybe it's just a decoy to throw other manufacturers and backyard mechanics off their trail so they don't know which are the important R&D modifications and which ones have no advantage whatsoever.

mdouglas71

I wouldn't do it because it's a little sketchy. I think a rock or some debris can really damge it and keep it from stopping correctly..

E.Marquez

Thanks for you input..

In response.

What is sketchy? Im not looking at doing this with bailing wire and duct tape. The methods and design is common and well engineered for mounting a rear brake caliper under the swing arm. Of course anytime you modify any component on a motor vehicle you have to do it well to avoid issues, from part failure to that MOD causing some other cosmic event...

A rock? Well sure anything is possible.. But as I have off road bikes for riding in dirt and rocks,, the VTR will not see a lot of "rocks".. Anything big enough to hit the caliper and damage it I might encounter on the street is big enough to damage the rotor, my leg, a wheel... so i think I'll just avoid them if possible.. In addition many bikes use the under swing arm caliper location from the factory,, if it was a big a liability or concern as you imply... the factories would not do it.. Not to mention, a google search comes up with no such issues for the models I know using an under swing arm mount.. So while it's possible for a rock to get kicked up and damage the caliper... it seem not to be likely or common.

Lastly.. even if the rear brake was damaged in some freak occurrence encounter with a rock,, it would have almost no effect on my ability to safely and completely slow the bike down and stop. The rear brake provides very little percentage of overall stopping capability.

98VTRrider

along those lines, there is a method of mounting the rear caliper under the swingarm that uses additional linkages to counter the "squatting" of the rear suspension under braking. It harnesses the force of braking and transfers it through linkages and a forward pivot point to put leverage on the swingarm to resist squatting. I believe it adds some stiction to the rear suspension but I've seen it on some race bikes.

E.Marquez

While interesting, the amount of R&D, trial and error needed to make such a system for the VTR1000 work correctly is beyond my reach, or goals.

I have a hunk of 6x12x2 7075 just waiting to be used to make a part of some sort.

Need to fire up the CAD software, build the part layout and see where it takes me.

7moore7

You don't want to build anti-squat resistance? Why stop there? You could build a horst link suspension and get rid of that pesky fixed wheel travel path.