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xvs650 6 pot caliper?

Discussion in 'Cruisers' started by Darrin Hodges, May 31, 2015.

  1. Can you get a 6 pot caliper mod for xvs650? Have seen it mention but have not found anything specific on the internets

  2. Very possibly.

    Can I ask what you might be hoping to achieve with a 6 pot caliper?

    I'm sorry that I can't point you to an internet site, but, in Kevin Cameron's book, Sportsbike Performance handbook, there is a chapter devoted to brakes, including the sordid details of calculating mechanical advantage for the hydraulic system.

    The warning I would give, tho, is that modifying brakes can have unexpected consequences.

    I've changed front brakes on three bikes, one, the Street Triple, worked a charm, the other two, an RZ250 and a Z50, turned the bikes into monsters who'd lock up the front wheel if you so much as LOOKED at the brake lever in the wrong tone of voice. :-(

    If you can't find anything better on line and you can make it to Beecroft, I could lend you the actual book.
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  3. I'm looking to improve the braking power, I've read you can gain modest improvements by using a braided line and different brake pads, which I will look at trying first. With 300KGs (me + bike) I generally have to almost 'book ahead' for braking which is fine mostly, haven't had to deal with an emergency stop really yet.
  4. The brake line business, yes, you can get a wee bit of improvement, but your bike is only 4 years old, so the brake lines should still be in reasonably good nick.

    It's when you get into much older brake lines that the braided option is better.

    Do you know if your bike has the "standard" pads?

    Quite often, folk will replace standard pads with harder, more "sporty" pads which will give the opposite effect from what they are trying for.

    If you can find softer than standard pads, they might be worth a try, even tho they will wear out quicker.

    Do some practice quick stops........ you really truly need to know just how good or bad the beast is.
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  5. #5 oldcorollas, Jun 1, 2015
    Last edited by a moderator: Jun 19, 2015
    More pistons is generally to allow use of a longer pad with even force distribution.

    To get more braking force:
    1. Higher friction coefficient pads, in the right temp range.
    Higher temp range often trades off low temp performance, but not always.

    2. Higher mechanical advantage, basically larger diameter brake disc (or adding second disc if only single). Easy, 20% larger diameter, 20% more braking force.

    3. Hydraulic leverage. This gets more complicated, but still relatively easy to work out. Need.to consider force and movement, as your hand can comfortably provide only a certain amount of force over a certain lever movement.
    Basically comes.down to lever length, lever pivot ratio, master cylinder piston area, and caliper piston area.
    Since force and movement input are hand limited, you are basically trading off pad force vs movement, and since you need a certain pad movement to overcome pad knockback, force increase by using bigger caliper will always be limited.

    Braided lines reduce lever movement as line pressure increases, so they can allow you to run a slightly longer lever (or change lever pivot point) and get slightly greater pad force

    Pads are easiest change.. doubling friction coefficient can double braking force...
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  6. It had 2K on the clock, so I'm assuming it has the factory fitted pads. Thanks for your input, I will look at just changing the pads to a different type, that may provide the extra bit I'm looking for.
  7. Spent ages typing a response, went and got a coffee and everyone had said what I was going to say already! Hah!
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  8. this might help explain the pad friction ratings a bit. (random SAE thing, not necessarily same as bike brakes, since HH is common as sintered compound on steel discs, not carbon)
    but friction rating alone doesn't tell you things like wear rate or usable temp range.


    but friction coefficient changes with temp too, eg

    graph for Hawk racing pads.. huge coefficients are possible.. but tradeoff with low temp
    HP+ would be good road pad. Black would take a bit of heating on first brake application (after any extended cruising), but while warm would be good too
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  9. I think from recollection that the XVS 650 has a drum rear brake, DH. That wouldn't induce a whole lot of confidence in braking power, particularly under load. I imagine you rear brake first then ease on the front for a short stop. I think your problem is the power of your rear brake. Drum brakes have a spongy feel (more mechanical). The harder you press the more the bike seems to slow down. Sometimes to the point you feel like you're standing on top of the brake pedal!

    Yamaha are a bit weird regarding the brakes on their cruisers. The XVS 650 is such a great bike...and they don't put disc brakes on the back??? The same as my Roadliner 1900cc. It doesn't come with ABS??? When I need to shorten up in a hurry I down shift...and squirm all over the road. And that's before even touching the brakes! A big difference from the Triumph Storm ABS. That'll stop on a penny fully loaded. Just gotta remember what bike I'm on and watch my spacing.

    I really don't know about your problem, DH. Moding the front brakes may not be the solution. Putting a disc on the rear would certainly go towards helping...but I guess by then you'll be eyeing the XVS 950. Now that's got a rear disc!
  10. Yeah, for short stop (or I have a pillion) I throw all the anchors out and downshift - it just means you have to plan ahead for your breaking! I do plan to move to the 1100 at some point.
  11. is it a single disc front end?

    swapping forks and front wheel to get a twin disc will approximately double your braking capacity :p
  12. Sorry. The maths teacher in me cannot let this pass. 20% larger diameter gives you 44% larger force, as force is directly proportional to the surface area. Surface area is given by Pi x radius ^ 2

    Otherwise, a very useful post.
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  13. yeah, single disk, I have looked around but it seems nobody has done that particular conversion.
  14. #14 oldcorollas, Jun 19, 2015
    Last edited: Jun 19, 2015

    sure it's not the length of the moment arm?

    eg, force F at distance X = turning moment of FX
    increase moment arm by 20%, so 1.2X, turning moment = 1.2FX
  15. The 950 looks like it come only with cast wheels, where the 650 are spokes.
  16. Have you locked up the front yet? Or run out of brake lever travel? If no to both, then try. Squeezing a little more. In my experience on the xvs1100, the limiting factor is tyres and my nerve. It stops reasonably well with good tyres (not long lasting ones or stock ones).
  17. No locks up, just looking for a bit more comfort :)
  18. #18 oldcorollas, Jun 19, 2015
    Last edited: Jun 19, 2015
    braking torque is directly proportional to disc radius.. and so is also proportional to disc diameter
  19. Ah. I see what you are saying now. We were at cross purposes. Yes, you would be correct then. I thought the implication was that there was more disc to clamp to, rather than just a larger radius disc.
  20. nah, is simply about leverage..
    now if we are talking heat generation, energy dissipation, torque required to accelerate and decelerate the disc etc etc.. then we get into mass, which depends on volume, which depends on surface area :) but it's a little complicated (although the equations are not that difficult, just not really forum material..)

    adding twin disc front end would be a great upgrade.. apart from all the complications and legalities..
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