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lyinlow
12-19-2006, 12:01 AM
just curious if anyone has used a rear caliper off of a bike and then used a master cylinder off a car?


reason i ask is i have a suzuki swift master cylinder and pedal assembly in the buggy and i want to use a motorcylce caliper.. you guys think this idea will work out for me? im thinkin ill just have to get a adapter to go fromt eh steel car line to the flex line of the caliper as it has the banjo fitting on it


any thoughts?
Trevor

Rorty
12-19-2006, 12:32 AM
Yes, use a 3/4" MC and a pedal ratio of around 6:1.

lyinlow
01-28-2007, 04:19 PM
might be a dumb ? but what do you mean use a 3/4" MC * *and also how do i set up a 6:1 ratio???

thanks in advance!

Trevor

KWiKSand
01-28-2007, 04:30 PM
3/4" MC = 3/4" diameter cylinder Master Cylinder

1:6 ratio on the pedal would be 1" of pedal length on one side of the pivot bolt and 6" on the other side of it, or some ratio equivalent to that.

masterfabr
01-28-2007, 05:22 PM
No such thing as a dumb question unless *you've already screwed up and didn't ask first. [smilie=biggrin.gif]

plkracer
01-28-2007, 05:30 PM
Another question, but the same thing, not trying to hijack. What if I'm using 3 motorcycle calipers on one master cylinder? Maybe go to a larger master cylinder than 3/4? Thanks.

renegadespec1
01-28-2007, 05:32 PM
Lyinlow,
I used a Geo Master cylender in the Wife's buggy I don't know how great this one works, but have used car masters in the past with no problems... They tend to have a really tight pedal feel because they push a lot of fluid compared to the small amount that the smaller bugggy calipers take to be actuated...Hope this helps you out ...BTW the local auto parts store can hook you up with the fittings and hard line...There was a thread awhile ago on using plastic line but I can't tell you the name of the thread... [smilie=drool.gif]

masterfabr
01-28-2007, 05:39 PM
Calipers only displace a small amount of fluid when applied. The piston/pistons only move a few thousandths when applied.It's the *pedal ratio (pressure)that you're after.YOu should be ok with a 3/4" bore.

masterfabr
01-28-2007, 05:40 PM
Calipers only displace a small amount of fluid when applied. The piston/pistons only move a few thousandths when applied.It's the *pedal ratio (pressure)that you're after.YOu should be ok with a 3/4" bore.

renegadespec1
01-28-2007, 05:46 PM
Master,
If you take the diameter of the car caliper and compare it to the bike caliper it takes alot more fluid to move the piston on the car caliper volume wise... I tried a stock pedal assembly once and a foot wiggle put you in the harness...

masterfabr
01-28-2007, 06:11 PM
I'm using a 3/4" bore at a 6:1 ratio with 3 wilwood 2 piston calipers and have what I like. With just one caliper it would be too large a bore.I agree,spec.I was assuming there were going to be 3 or more calipers.

masterfabr
01-28-2007, 06:12 PM
I'm using a 3/4" bore at a 6:1 ratio with 3 wilwood 2 piston calipers and have what I like. With just one caliper it would be too large a bore.I agree,spec.I was assuming there were going to be 3 or more calipers.

Rorty
01-28-2007, 09:15 PM
It's all about displacement. A 5/8" bore M/C will result in more pedal travel than a 3/4" bore M/C.
Lyinlow, the 6:1 pedal ratio is the working length of the pedal versus the length of the lever. In other words, it's six times as long from the pedal pivot to the theoretical centre of the pad than it is from the pedal pivot to the M/C pushrod pivot.

If you wanted to maintain a certain pedal travel but had to swap to a smaller M/C, you'd have to reduce the pedal ratio. Conversely, if you wanted a shorter amount of pedal travel without having to remake the pedal, you'd have to swap in a larger bore M/C.

Personally, I prefer a long (travel) pedal in an off-road car as it doesn't immediately lock the wheels up and provides more "feel".

Bugpac
01-28-2007, 09:22 PM
I got 2 1" mastercylinders i would part with, lol. Im using 7:1 ratio pedal myself....Not sure how its gonna work yet but wth!! * Ill try it anyhow...

nutnbolt2002
01-28-2007, 11:01 PM
Don't you have to apply more pressure to the master cyl. when you use bigger bores?

Rorty
01-28-2007, 11:17 PM
Don't you have to apply more pressure to the master cyl. when you use bigger bores?

Yes.

Rorty
01-28-2007, 11:53 PM
Don't you have to apply more pressure to the master cyl. when you use bigger bores?

Yes.

renegadespec1
01-29-2007, 05:13 AM
Guys,
I'm pretty sure Lyinlow is using the master cylender out of a car, and it has a front and rear ports, so the rear port is only pushing one caliper, but the front is pushing 2...but the pistons in the calipers are less than 1/2 the size of the pistons in the calipers in a car... I could be way off here but that has been my experience...I'll go lay by my dish now...

Rorty
01-29-2007, 05:32 AM
He should be using a single port brake cylinder like a clutch M/C. When did he say he's using a twin port cylinder? *[smilie=blink.gif]

Rorty
01-29-2007, 05:32 AM
He should be using a single port brake cylinder like a clutch M/C. When did he say he's using a twin port cylinder? *[smilie=blink.gif]

renegadespec1
01-29-2007, 05:46 AM
He should be using a single port brake cylinder like a clutch M/C. When did he say he's using a twin port cylinder? *[smilie=blink.gif]

Hey Rorty,
On his 1st post, Suzuki swift is a car, the same as a Geo metro... I have one here and it is a 2 port single res. and I think that it is 65% front 35% rear at least that is what the parts guy said *[smilie=blush.gif]

Rorty
01-29-2007, 05:51 AM
[smilie=ashamed.gif] Got it. OK, well he should be using a Girling single port or similar.

renegadespec1
01-29-2007, 05:58 AM
Rorty,
I'm just curious... I'm putting this set up... in this buggy so the wife has a chance to get the feel of buggies verses a car, should I have used something different? *This master is as light if not lighter than most racing stuff, and she won't have to learn brake bias I would just like to get your opinion...BTW seat looks great... I think I'll be braking one up in the not too distant future

Rorty
01-29-2007, 06:10 AM
Forgetting about the weight, you could use the one from the Geo, but you'd probably have to work out the bias with some sort of bias valve.

Don't forget to post pics if you make one of the seats.