RazMan
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| posted on 10/5/07 at 04:39 PM |
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Do the pads look anything like this?
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 11/5/07 at 01:46 PM |
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quote:
Originally posted by flak monkey
So summary:
Fr - Dynalites with 309mm OD discs.
Rr - Powerlites with 273mm OD discs.
50/50 setting on bias bar.
I have based the calcs on a CoG height of 400mm, sound reasonable?
I can send you the spreadsheet if you want to have a look?
If you are on msn it would make it easier.
David
Thanks for that David - I nearly missed it and thanks for the U2U.
I was intending to fit the same size disc up front and your figure would suggest that I need to go bigger still. However I have one final favour to
ask 
I have just received my order from Rally Design and they have sent 25mm piston size (not 34mm as I specified) Any chance you could do the calculatiuon
once more with the smaller piston size?
Thanks again 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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flak monkey
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| posted on 11/5/07 at 03:07 PM |
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Bearing in mind my spreadsheet only gives you the ideal theoretical set-up, it doesnt take into account the fact that the brake balance is
significantly different at lower decelerations. JAG helped me a shed load with my calcs for my dissertation. I just happen to have studied it for my
dissertation.
I reckon, with 25mm 4 pots on the back and 273mm discs all around you will need (for 1G deceleration) clamping forces of:
8695N Front
6455N Back
To get this theoretically you need:
0.625" m/c on both front and rear circuits
59% rear bias on the bar
And you are back to a 485N pedal effort
I will email you a copy of the spreadsheet and let you have a play with it. I'll try to explain how it works in the email 
David
Sera
http://www.motosera.com
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RazMan
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| posted on 13/5/07 at 04:05 PM |
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Update:
Thanks for all your help David - it is much appreciated.
I just thought I would post a couple of pics of my rear brakes.
First there was this ......jpg)
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 13/5/07 at 04:05 PM |
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.... and now there is this .....jpg)
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 13/5/07 at 04:08 PM |
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Old disc was a bog standard Sierra jobbie - fine for stopping a Seven but a bit overworked in my middy.
The new setup is a 4 pot Supalite handbrake caliper and a 273mm solid disc. It should stop me far better but I havent had a chance to try them out yet
as I discovered that I had the wrong type of brakeline fitting AFTER I had cut the old one off  So I'm off to my hydraulic factor
tomorrow.
They look good though 
[Edited on 13-5-07 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 21/5/07 at 12:00 PM |
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Another Update:
These brakes are still a challenge but I think I have another plan.
I have now also fitted 285mm discs on the front and retained the Dynalites. This has increased the mechanical advantage of the caliper and therefore
improved the braking ....... slightly.
There is no doubt that the car will now stop quite effectively but the pedal pressure required is astronomical! So I am now going to try and increase
the pedal ratio which is presently at 4.4:1. If I raise the pivot point towards the bias bar I reckon I can increase the ratio to more like 6:1.
I've just got to work out how to do this with the least amount of modification to the pedals and master cylinder mountings.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 24/5/07 at 10:10 AM |
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Yet another Update:
I recently asked Keith Wood at Aeon about any possible solutions to 'scary brake syndrome'. With some magic calculations and a lot of
thought, Keith came up with the simplest solution - the pedal ratio needed to be increased. This was achieved by making a new pedal which had the bias
bar moved 10mm closer to the pivot point, increasing the ratio from 4.4:1 to 5.5:1. The difference is nothing short of miraculous and I can now lock
the front wheels at will, but still with plenty of 'feel' on the pedal.
For everybody's reference my setup is as follows:
Front - 285mm vented discs with Wilwood Dynalite calipers.
Rear - 273mm solid discs with Wilwood Powerlite handbrake calipers.
Presently the master cylinders are 0.625" front & 0.70" rear but Keith reckons both need 0.625" as the front is now somewhat
overbraked, despite having the bias bar fully towards the rears. I might even swap them over and see how the brakes feel like that before investing in
a new m/c. My theory is that a smaller rear m/c will need a smaller caliper piston to achieve the same amount of pedal travel & therefore balance
with the larger fronts.
Flak, would you mind running this combo (and the swapped version) through your formula and letting me know which one would work best?
[Edited on 24-5-07 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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ChrisGamlin
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| posted on 24/5/07 at 11:39 AM |
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If you want to borrow a 0.625 Girling (needs remote reservoir) I can lend you mine if you cover the postage
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flak monkey
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| posted on 24/5/07 at 12:04 PM |
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quote:
Originally posted by RazMan
Flak, would you mind running this combo (and the swapped version) through your formula and letting me know which one would work best?
I'll do it tonight for you Raz
Sera
http://www.motosera.com
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RazMan
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| posted on 24/5/07 at 09:55 PM |
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quote:
Originally posted by ChrisGamlin
If you want to borrow a 0.625 Girling (needs remote reservoir) I can lend you mine if you cover the postage
Thanks for the offer Chris. Due to space limitations I had to modify the existing m/c to fit in so I think I had better buy one to hack to pieces
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 24/5/07 at 09:57 PM |
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quote:
Originally posted by flak monkey
I'll do it tonight for you Raz
Thanks matey - it's been a mad week and it's not finished yet
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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flak monkey
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| posted on 25/5/07 at 06:36 PM |
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Sorry about this Raz, day later than expected but heres the results:
With your current set up, with the 0.7 on the back and 0.625 on the front, as you are experiencing the rear is miles underbraked, even with the bias
bar adjusted all the way which wont give you enough adjustment as you need it set at about 70% to the rear and 30% to the front. Your pedal effort is
a more repectable 370N or so.
With 2 0.625 m/cs you will keep the same pedal effort but you will be able to reduce the brake bias to about 60% to the rear, which should be within
the range of adjustment you have.
The balance is certainly miles better with 2 0.625 m/c's.
David
Sera
http://www.motosera.com
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RazMan
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| posted on 25/5/07 at 07:00 PM |
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Thanks a million David - I don't think I'll bother with swapping the m/cs around and just get another .625" m/c for the rears. At
least I will know that I've made the best of what I've got - with your help of course
Thanks again
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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flak monkey
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| posted on 25/5/07 at 07:07 PM |
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I will run it with them swapped for you now. Will only take a couple of mins.
Sera
http://www.motosera.com
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flak monkey
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| posted on 25/5/07 at 07:10 PM |
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See, 3 minutes
With the swapped you can set the balance bar to 55% rear 45% front, but your pedal efforts back up to 430N according to my model.
Up to you, both will work of course.
[Edited on 25/5/07 by flak monkey]
Sera
http://www.motosera.com
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britishtrident
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| posted on 25/5/07 at 07:47 PM |
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In old money that is almost 100lbs (actually 96.5 pounds force)
Anything over 70lbs is really hard work.
[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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RazMan
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| posted on 25/5/07 at 10:53 PM |
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quote:
Originally posted by britishtrident
Anything over 70lbs is really hard work.
You should have tried pushing my pedal when I had 0.75" m/c front & rear then! Two feet on the pedal just to stop at junctions
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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