Hi Toms, Whose maths are you querying ? Jim
From: Tom Walker Sent: Monday, July 27, 2020 3:12 PM To: [email protected] Subject: Re: [Quantum Owners] Brakes, jumping to conclusions and maths Are you sure about the maths there? With the 4-pots you've got a total 3060mm2 of cylinder per wheel (regardless of which side of the disk they are on) vs 1810mm2 for the original calipers - which is about 40% more piston per wheel. So for a given pressure of fluid pushed (N/mm2) from the master cylinder, the slaves will exert 40% more pressure (F2=F1xA2/A1) but your foot will have to move 40% further (F1d1=F2d2). If you can live with the pedal travel, then for the same leg work you will be applying 40% more pressure to the disks. Add to this the fact that with the four pots you have that pressure over a slightly larger pad area, and of more significance at a greater distance from the axis giving greater braking torque - the braking efficiency increase will be more than the simple 40% calculation. If you fit a bigger master cylinder (for argument's sake let's say you find a cylinder which is 40% bigger) then you will negate the need to push the pedal so far, but at the expense of physical effort as the pedal pressure will need to be higher. As it happens I've got the HiSpec 4-pots on my 2+2 but with 305mm rotors (you need 16" wheels). On the back it's the Fiesta Centre rear-disk conversion (I think they are Escort disks with a Granada caliper, but I may be wrong). Under the foot it's got an adjustable front/rear brake bias pedal box with 0.75" pistons for both front and back and most recently, about 4 years ago, I fitted a remote vacuum assistance unit (designed for Robin Reliants - I think?!?) but to be honest for various family reasons, I've not driven it yet, so I can't tell whether it's brilliant or a death-trap. I can tell you it's really really really dusty. Tom On Mon, 27 Jul 2020 at 09:37, Jim Hearne <[email protected]> wrote: I’m afraid it looks like my calculations disappeared in one of my PC upgrades. I know on my final setup i drilled a new hole in the brake pedal further up from the existing XR2 one. I think that was to give me more pressure in the brake system at the expense of a bit more brake travel. As Bill says, you need to upgrade or replace all the bushes and pins in the linkage. You can also make sure that the pushrod in the servo is adjusted correctly so that there is no play between it and the piston in the master cylinder. Most people don’t know that is adjustable. Be careful though, the pistons in the master cylinder have to return to the full idle position to allow any pressure in the system to fully disappear when you release the pedal. If you leave pressure on the pistons in the master cylinder via the servo then when the brakes get hot the expanding brake fluid has no where to go and gradually holds the brakes on, BTDT Jim From: russ price Sent: Monday, July 27, 2020 9:18 AM To: Quantum Owners Group Subject: Re: [Quantum Owners] Brakes, jumping to conclusions and maths Thanks Bill your reply certainly does help. I have fitted braided braided lines but the linkage could do with a bit work. So all i need to do now is find a servo + mastercylinder the same dimensions or as close to the Fiesta items as possible, there is plenty of room and fabrication of the servo tower/bracket if it needs changing should not be problematic. That is of course unless someone has a mk2 servo they want to sell. On Monday, July 27, 2020 at 8:36:46 AM UTC+1, Bill Allison wrote: Hi Russ I hope these comments will be useful: Your standard setup: Caliper piston area 2 x 1810mm2 = 3620mm2 Hi-Spec setup: Pair of twin piston calipers (a pair of opposing pistons exerts the same clamping force as a sliding caliper with a single piston) 4 x 765mm2 = 3060mm2 Difference = (3620-3060)/3620 = 85% So on the face of it you need a 15% smaller (area-wise) than standard master cylinder to get the same braking effort, BUT, you need also to take account of the increase in leverage due to the larger discs: 265/225 (the effective diameters) implies a 17.5% increase (area-wise) in m/cyl size. The two as near as dammit cancel out, so you actually need to not change master cylinder size! I have not incorporated rear slave cylinder size in the calcs because the rear pressure limiting valve takes them out of the equation at quite low pedal pressures. I hope that helps. Regarding pedal feel, it's pretty much essential to replace the rubber flexible hoses front and rear with braided teflon lines, I found also that pedal feel can be further transformed by removing play at every point in the longish route from your foot to the master cylinder, including setting the m/cyl pushrod clearance. Best regards Bill Bill Allison Borders Group of Advanced Motorists National Observer (Cars) 07702 739474 01750 22550 (before 21:00 please) www.bgam.org.uk and www.bgam.org.uk/ydi www.iamroadsmart.com www.facebook.com/BordersAdvancedMotorists The contents of this message, and any attachments, may include information that is private and confidential and should not be read by persons other than the intended addressee(s). IAM RoadSmart nor the sender accepts any responsibility for viruses and it is your responsibility to check the email and any attachments. If you have received this email in error, please inform the sender and delete the message from your computer. IAM RoadSmart is a trading name. IAM RoadSmart is a trademark. Charity number: 249002 (England and Wales) SC041201 (Scotland). Registered Address: 1 Albany Place, Hyde Way, Welwyn Garden City AL7 3BT. On Sunday, 26 July 2020, 10:54:37 BST, russ price <[email protected]> wrote: After fitting Hispec 4 pot calipers and 280mm discs i thought i should do something about a probable leak from the master cylinder, the clue being rust and bubling paint on the servo. The trouble began when i sheared off a stud holding the m'cylinder to the servo, no problem i thought i have a Mondeo m'cylinder/servo which i have heard is used as an upgrade and a bigger m'cylinder is probably a good idea after going from 2 to 8 pistons on the front. This i now believe was an olympic standard jump to the wrong conclusion. If i have done the maths right, ( I would be grateful if someone checked my results) i need to go down in m'cylinder bore size. Now i know calculations of braking forces are really complex but this just about the "feel" of the brakes. Here are the figures i used, original calpers single 48mm piston, new calipers four 31.2 mm pistons, rear slave cylinder 17.5mm, original m,cylinder 20.6mm, mondeo m'cylinder 25.4 Which give an original set up m'cylinder/caliper ratio ~ 1:23, original m'cylinder + new calipers ~ 1:20, mondeo m'cylinder + new caliper ~ 1:13 So given Fiesta mk2 servo's are not exactly thick on the ground i thought about a set up similar to that recently used on 003, ie. landrover servo + Mk1 19mm m'cylinder which should give me a ratio ~ 1:23 I would really appreciate it if anyone can say to me " Your are talking nonsense and here's why......" or " Yes that should work but be aware of ......." -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/5e0fda55-6bbe-41f8-9fb4-400ad2881832o%40googlegroups.com. -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/5623fde2-4cea-4541-8f7e-1130aa49bfc1o%40googlegroups.com. -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/BFF5A83EAE124030BEC84565F3C63ED7%40JimQuad. -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/CADjwJF7tc%2B4YgmtB6iRvith1pxgFcypkTiDaZm9z%3DuzW6Z3H0Q%40mail.gmail.com. -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/24304672A8A846FDBED2B2E5EF282FAA%40JimQuad.
