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#Post#: 8407--------------------------------------------------
Brake pedal dimensions
By: Moogie38 Date: March 15, 2023, 8:47 pm
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I have been reading through the posts on here about that people
are using for the braking systems on their cyclekarts.
I found Stefans post giving details about the force on the pedal
against breaking force and noticed it stated a pedal length of
130mm and a length of 40mm for the pivot to master cylinder push
rod, but that was using a different master cylinder than I have.
My parts are,
1996 Honda CBR 600 front brake caliper, with 2x25.5 pistons.
[attach=1]
Suzuki GSXR 750 rear master cylinder.
[attach=2]
And a Gemini 254 x 4mm disc.
If someone is using a similar setup to mine could they give me
an idea of what the length to pushrod should be ?
[attach=3]
Thanks, Noel.
#Post#: 8408--------------------------------------------------
Re: Brake pedal dimensions
By: StefanN Date: March 16, 2023, 3:04 am
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Hi Noel,
You need to know the diameter of the master cylinder to
calculate this. There is also an amount of personal preference
on pedal feel. I’m happy to help if you can find the master
cylinder diameter.
#Post#: 8409--------------------------------------------------
Re: Brake pedal dimensions
By: Moogie38 Date: March 16, 2023, 4:19 am
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Thanks Stefan, as far as I can find out the bore size is 14mm.
A firmer pedal is something I would be more used to.
Noel.
#Post#: 8412--------------------------------------------------
Re: Brake pedal dimensions
By: Moogie38 Date: March 16, 2023, 10:17 am
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Incase you need to know the stroke, it's 18mm.
#Post#: 8414--------------------------------------------------
Re: Brake pedal dimensions
By: StefanN Date: March 17, 2023, 4:28 am
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Hi Noel,
Huge caveat: I'm just sharing some idea - you've got to satisfy
yourself with the safety of the design and implementation of the
brakes on your cyclekart.
OK some calculations:
I'm assuming:
- an all up mass of 200kg (CK and driver)
- both rear wheels keyed to the axle
- pedal foot force to lock wheels 30kg - you can see what this
feels like by sitting in a driving position and pushing your
foot against some bathroom scales
With your master cylinder and calliper combination and a pedal
length (pivot to where your foot presses) of 130mm, the calliper
should be connected at 32mm from the pedal pivot (at 90 degrees)
and will give a foot travel of about 13mm. There's lots of
assumptions in these calculations.
In terms of heat, because of all the variables, the only sure
fire way of knowing is to stress test the brakes somewhere safe.
However, looking at the energy that a GSX750 would need to
dissipate through the brakes (allowing for speed, mass,
front/back brake ratio), its about 3 times what a cyclekart
might, so that would suggest its not a daft calliper to use.
Remember though that typically Cyclekarts brake cooling is
compromised.
I've got no experience of using a bike rear brake master
cylinder. I think they are often orientated vertically? I
assume mounting them horizontally could lead to difficulties
with bleeding the brakes. Can anyone shed any light on this?
#Post#: 8415--------------------------------------------------
Re: Brake pedal dimensions
By: Moogie38 Date: March 17, 2023, 6:49 am
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Thanks Stefan, that gives me a starting point, all I can do is
try it. I have an idea to aid cooling, just need to see if I
can make it fit.
The club kart that Steve Vinson and Dennis Thomas built uses a
very similar setup to what I have, even the caliper looks almost
identical.
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