theprisioner
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| posted on 14/7/14 at 11:24 AM |
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J15 front brake bite
When I built the J15 I also did the Willwood vented disk conversion on the Triumph/Caterham upright on the front suspension. Now that I have decided
to track the J15 I am finding the brake bite an issue. I want to drill the front disc. I have access to a CNC mill with a rotary table so I can
precisely place the holes to avoid the webs. Can anyone suggest why I should not do this mod?
I have drilled discs on my Westfield and the bite is wonderful.
All comments welcome!
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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Slimy38
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| posted on 14/7/14 at 12:06 PM |
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The only reason why I can think not to do it is that I'm not sure why drilled discs would affect the bite? Isn't it more likely an
imbalance between the calipers and your choice of master cylinder?
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Alfa145
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| posted on 14/7/14 at 12:21 PM |
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I always though drilling was to increase the surface area to provide slightly better cooling under heavy braking and help remove gas buildup under
heavy braking.
Drilling yourself is not such a good idea imo. Too much pressure causing minute crack could be fatal if it broke at speed.
To get more bite you want softer pads or a change of cylinders. Having more cooling with drilled and vented disks would stop heat building up and stop
the pads reaching their optimal operating temperature
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Jenko
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| posted on 14/7/14 at 12:51 PM |
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I would consider all aspects of the braking.....The J15 is clarly a light car, especially at the front. Are you sure that the full vented discs are
not 'too good'...sometimes with a smaller disc set up, it's far easier to get a bit of heat into the brakes, and with a bit of heat
comes possibly a bit of extra bite.....Other option is to maybe playaround with the bias.....I can't see how drilling helps, but I've
never had drilled discs, so could be wrong.....Just a thought
MY BLOG - http://westfieldv8.blogspot.co.uk/
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theprisioner
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| posted on 14/7/14 at 12:57 PM |
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AP racing do not appear to agree..................
http://www.apracing.com/products/race_car/formula_student/sae/brake_discs.aspx
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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Jenko
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| posted on 14/7/14 at 01:16 PM |
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OK...AP know far more than any of us, and the reasoning they state seems perfectly sound.
So, based on thier advisement, it would appear drilling the discs (obviously allowing for the bedding in, and crack issue they mentioned) would give
you better bite. Would be interesting to get before and after comments from your good self.
[Edited on 14/7/14 by Jenko]
MY BLOG - http://westfieldv8.blogspot.co.uk/
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Alfa145
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| posted on 14/7/14 at 01:24 PM |
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RedDotRacing say:
FF - Drilled and Grooved Disc
The Drilled & grooved range of discs, available for most road vehicles, deglaze the pad and vent gasses that build up between disc and pad during
braking. As a result brake fade is significantly reduced.
The additional drillings dissipate heat more effectively giving an increase in performance than the XJ range.
Suitable for road and light competition use..
(http://www.reddotracing.co.uk/)
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jeffw
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| posted on 14/7/14 at 01:47 PM |
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Is this not more likely to be a Pad selection issue? What pads are you running?
All x-drilled discs are actually cast like that not drilled. Drilled disc could well shatter. Vented plain disc should be fine in something enclosed
like a J15 (plain non-vented might overheat).
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britishtrident
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| posted on 14/7/14 at 03:14 PM |
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Most likely a Pad friction material issue and/or pedal ratio/master cylinder bore issue.
Minted M1144 is regarded by a lot builders as being streets ahead of anything else for this general size and weight of car.
Measure the master cylinder bores and pedal leverage ratio, cars without servo require smaller bore master cylinder than modern tinntops to give a
reasonable pedal force.
[Edited on 14/7/14 by britishtrident]
[Edited on 14/7/14 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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mcerd1
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| posted on 14/7/14 at 03:23 PM |
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even AP say there is a risk of cracking with drilled discs - so I'd leave DIY drilled discs to a last resort
pad choice and the ratio of the piston size to the master cylinder is were I'd look first
2 different pads that both stop you just as well as each other - but could feel totally different
eg. I've used several ones on my tin-top, motorcraft ones worked well and lasted along time, OE mintex ones stopped and lasted just as well, but
the mintex ones just feel better and have a nice bite to them 
(also OE mintex ones are ~%10 cheaper  )
[Edited on 14/7/2014 by mcerd1]
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Alfa145
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| posted on 14/7/14 at 03:23 PM |
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I've got solid discs and M16 callipers running Mintex M1144 pads. Not had them overheat on tack yet in my Stylus, which is as enclosed as the
J15, but they do get warm, no fade to date either.
Although saying that I probably never did more than 10ish laps before needing to give myself a rest.
Perhaps I'm just not trying hard enough
[Edited on 14/7/14 by Alfa145]
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twybrow
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| posted on 14/7/14 at 03:43 PM |
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quote:
Originally posted by Alfa145
I've got solid discs and M16 callipers running Mintex M1144 pads. Not had them overheat on tack yet in my Stylus, which is as enclosed as the
J15, but they do get warm, no fade to date either.
Although saying that I probably never did more than 10ish laps before needing to give myself a rest.
Perhaps I'm just not trying hard enough
[Edited on 14/7/14 by Alfa145]
What size mcs are you using? I also have poor bite, and I run grooved discs with the Wiwood setup and it isn't all I hoped for in terms of bite
and feel.
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Surrey Dave
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| posted on 14/7/14 at 04:48 PM |
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Mintex
For what it's worth the difference between standard pads and Mintex 1144 was night and day on my Locost.
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theprisioner
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| posted on 14/7/14 at 05:16 PM |
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Which was night and which day and which is better?
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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Surrey Dave
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| posted on 14/7/14 at 05:22 PM |
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Ho Ho!
With standard pads in M16 calipers the brakes were terrible, almost impossible to lock the front wheels, probably dangerous.
With Mintex1144 the brakes were progressive and had good feel , and could be locked if necessary, changed the car significantly.
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theprisioner
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| posted on 14/7/14 at 07:15 PM |
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I have the Mintex pads but the performance is such that there is a delay before effective braking i.e. poor bite. A friend suggested groves which is
just as easy to machine but what is the collective wisdom about the possibility of cracking issues?
http://sylvabuild.blogspot.com/
http://austin7special.blogspot.co.uk/
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Alfa145
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| posted on 14/7/14 at 08:15 PM |
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For the sake of a price of disks is it really worth potentially risking your life?
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britishtrident
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| posted on 15/7/14 at 06:41 AM |
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The info on the AP website gives the impression it is is written by a sales "engineer"
Drilled or grooved discs are not a miracle cure for anything, they first became popular when disc brakes first appeared on motor cycles around 1970,
the main reason for fitting them was to improve wet weather braking. Motor cycle brakes run without splash shields, in wet conditions particularly
motorway journeys where the brakes are used infrequently a wet oily film can build up on the discs that creates a split second delay before the pad
bites the metal of the disc surface, drilled or grooved discs reduce the problem.
Unless your brakes are getting smoking hot any other advantages drilled discs give are tiny. if they are getting smoking hot while they vent gas from
under the pad they also increase the chances of disc failure or warping.
If the pads are genuine M1144 deglaze the pads and discs with 80 grade production paper and measure the piston in the master cylinder and calliper
and estimate the true pedal leverage ratio. If you do the maths on the brake hydraulics you will probably find the front brakes are only getting
about 1/4 the hydraulic pressure they would get in a tintop for the same pedal force.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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