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'85 front calipers question - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums - Lotus Community Partner #ForTheOwners Jump to content


'85 front calipers question

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Hi, looking for some information about piston surface area for the brakes,  the rear stays standard so I presume I can't go too big at the front?  I have 285x26 discs up front so not too big,  the smallest 4 pot pistons I can find already have 1,25 times the surface area of the single pots I have now.  does anybody know how much I can go bigger but still keep a good balance between the front and rear?  for the little europa I seem to have the same problem, the balance bar in the brake pedal is way of so I need smaller pistons at the front as well.  just wondering how much smaller lol.  best would be to buy smaller for the europa and put the wilwoods from the europa on the esprit but maybe this is overkill as well.  for the esprit I have 4 pots that have twice the surface area so way too big....

thanks, Rick

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no I did not and to be honest I have no idea how that works as the pressurized brake oil works on the surface area only.   I'll dive into it, thanks! 


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My way of looking at this is as follows: caliper hydraulic force translation is the product of line pressure x surface area of the driven piston(s). So I prefer to resolve your concern in that the 4-pot divides the line pressure between two operated halves, and this is why such calipers equate with a single pot sliding caliper in which the total line pressure (force) is applied through the one piston while the force is split between the two halves of the 4-pot. This holds true when comparing sliders with 2-pot also.

I've done quite a bit of analysis on this subject, planning to upgrade my S2 brakes as well. Factors to bear in mind include: rear tyres 10% taller than front, differing rotor diameters ( early Esprit meaningfully ), M/C bore diameter, use of vacuum booster, etc. Your overall fore/aft balance of braking force, taking the above into account, should be 62/38 for a rough start. I note that Lotus 1st re-engineer of the brakes upped the front rotor diameter keeping all else pretty much as was. Work through the figures for your car and let us know what you think.


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