mcg
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| posted on 19/9/18 at 02:52 AM |
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Brake set up and technique for track driving
Excellent day at Lydden Hill on Saturday. A number of issues but now have the winter to work through them.
Brakes continue to be an issue. Pedal travels 70% of the way in before having any meaningful bite, and still can’t lock up the fronts.
I have had feedback from the locost community on the issues on this before and am working with someone to solve. My questions this time around are
more general:
1. For hard track driving, braking and down shifting, is it normal to need to blip on downshifts, and ideally heal and toe? If so, can this be
achieved with normal pedal box set up for locost with duel MC and brake bias bar? Or..
2. Is it a good idea to consider servo assisted brakes?
Look forward to hearing your thoughts!
Thanks
Matt
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Nickp
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| posted on 19/9/18 at 06:01 AM |
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Firstly, you should never need a servo on a 7 type car unless there's something wrong with your right leg / foot 
Good heel and toeing should smooth out the downshifts and help prevent lock ups. Personally I don't do it and have managed just fine all these
years on road and track. Your pedals need to be set up right to do it well, and if yours has 70% brake travel then I'd say you've got no
chance with it as it is. Sounds like you might have a mismatch between master cylinders and calipers or too much slack on the push rod from pedal
(depending on your setup, got any pics?)
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rodgling
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| posted on 19/9/18 at 06:25 AM |
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1. You don't 100% need it, but it does make braking on the limit a lot better / smoother. Without it there's a good chance of locking the
rears when you downshift under hard braking (as the rear is unloaded anyway). I modified my throttle pedal so that there's a second part which I
can use my heel on, this works extremely well from the point of view of being easy to get my feet in the right place.
2. No it's not. You probably need to get the right master cylinder / brake sizes / decent pads / brake balance, maybe bleed the brakes, etc to
get the system working well. With well set-up brakes 7-type cars will brake very well.
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cliftyhanger
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| posted on 19/9/18 at 09:00 AM |
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And you really don't want the rears locking up before the fronts. That can end VERY badly.
As above, sort the balance out. You can either reduce rear efficiency, or better improve the front brakes (bigger discs, bigger callipers, or easiest
better pads)
The long travel could be all sorts of issues, and that needs attention but won't affect balance (or shouldn't unless there is a fault. It
is2 master cylinders with a balance bar so smaller master for the front would work, but increase pedal travel even more)
If you cannot press the pedal hard enough, a longer pedal/change pivot point (again longer travel) or if you do have a weakness, a servo may be
required.
It may be worth reposting details of cylinder sizes, and what brakes you have front and rear...and what pads you are using.
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mcg
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| posted on 19/9/18 at 11:02 AM |
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Thanks all for the replies. I have M16's at the front with standard road pads, and sierra calipers at the back, again with standard pads. Home
made pedal box based on 'book' geometry with balance bar added. 0.625 MC for the fronts and 0.7 for the rear.
quote:
Originally posted by cliftyhanger
And you really don't want the rears locking up before the fronts. That can end VERY badly.
As above, sort the balance out. You can either reduce rear efficiency, or better improve the front brakes (bigger discs, bigger callipers, or easiest
better pads)
The long travel could be all sorts of issues, and that needs attention but won't affect balance (or shouldn't unless there is a fault. It
is2 master cylinders with a balance bar so smaller master for the front would work, but increase pedal travel even more)
If you cannot press the pedal hard enough, a longer pedal/change pivot point (again longer travel) or if you do have a weakness, a servo may be
required.
It may be worth reposting details of cylinder sizes, and what brakes you have front and rear...and what pads you are using.
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cliftyhanger
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| posted on 19/9/18 at 12:33 PM |
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I would try 1144 pads at the front, with some more bias towards the front.
"Standard" pads varies wildly, from whire-box stuff made from cardboard to something like normal mintex. 1144 will have a whole lot more
bite.
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