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910Esprit

wilwood piston size and maths question....

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Hi Anyone know what size pistons are used in the 'kits' offered by the specialists such as PNM?   2 sizes of wilwood pistons  seem commonly available - either 1.75 or 1.38?    supplementary question, Are there any boffs on the site that can remember their Pi to tell me how both compare to a single 54mm piston in fluid displacement terms?

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Volume dispaced = area x piston movement. 

Area = Pi R2

If you're comparing calipers with pistons on both sides, then just do area, if you're comparing a sliding calliper (so piston/s on just one side then simply use 2xarea.

 

 

1.38 inch = 34mm = 17mm radius 289mm2 per piston, 

1.75 inch = 46mm = 23mm radius. 529mm2 per piston or roughly 1.8x the area of the  1.38inch piston.

54mm = 27mm radius, 729mm2 per piston roughly 1.5x area of the 1.75mm piston, or 2.5x area of 1.38 piston

 

Don't know how many pistons you're comparing, so cannot complete the comparison.

Edited by andydclements

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The Wilwood upgrade for Esprits by PNM typically uses a 4 pot caliper....don't know the sizes, or the standard caliper piston size either. Can't find the sizes in the manual....I can measure the standard size tomorrow, which will let us do the sums for each of the other piston sizes...

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Thanks guys.   The 54mm is a girling M16 type caliper, so I suspect that's the standard size in my turbo.  I was considering moving to a 'budget' 4 piston setup.  e.g. Wilwood.  So, I was just trying to see how the volume of each of these compare.   Generally, I'm happy with the balance and clamping force of the standard set-up so, I don't want to overbrake the front.  

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One of the Esprit owners here in oz has Wilwoods on his car with I think 305mm discs. With our legislation he had to have his system passed by an authorized engineer so all the sizes pressures etc were correct and working properly.

 

Shoot me your email and I'll pass it on to him to contact you.

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I have the PNM conversion on my 82 turbo; best thing I ever did....with it the brakes are significantly better and there's no sign of front/back imbalance. Should have done it years ago....

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I have 4 pot wilwoods conversion on mine. Previous owner never mentioned it and was a nice surprise. Very good brakes albeit mine squeal a bit but could be down to pads.

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Bumping this old post as I am also curious about various piston areas used in 4 pot upgrades for the G car, Hispec/PNM, Wilwoods etc.

Ebay has a ton of Wilwood and Brembo calipers, if I could get the balance right I can mill some adapters.

 

Anyone have any piston sizes that have worked for them? Or disc upgrades to fit under the 15" BBS wheels?

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PNM has a wilwood brake kit now availlable for the S1,S2 and S2.2 esprits.

It is a more recent product then the other kits for S3 and turboesprit.

 

Because S1,S2 and S2.2 cars have 14" wheels ( wolfrace or speedline) instead of 15" for the later cars, the kits use the standard 246mm discs ( plain or grooved version)

I wonder if someone already installed these 4 piston wilwoods and share the experience here.

Is it worth doing ?

 

I did refurbish my calipers and my brakes are in perfect technical condition for the past 4 years. But they remain standard 1 piston Opel calipers.

Should I consider them.

 

Geert

Edited by gvy

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If I recall correctly Lotus tested the 2/4 piston caliper at the time and they choose the single piston as they was better for brake balance. PNM kit looks interesting but I would stick with the original ones.

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It's unusual for me to disagree with Giorgio...but the 4 pot front brake PNM kit I fitted to my 82 Turbo has been a magnificent improvement to the whole braking experience, and I would recommend the system to anyone. It's changed the whole business of driving for the better.....Can't say anything about other models, though.

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John,

 

It is your comments in other topics that did me thinking about an upgrade

But the S1,S2,S2.2 kit uses the oem (not to big) 246mm discs.

In your case,Turbo esprit, may be you went to a bigger (and ventilated disc), which will improve braking considerably.

 

That is why I d love to hear from a S1 or S2 owner.

 

Geert

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It's unusual for me to disagree with Giorgio...but the 4 pot front brake PNM kit I fitted to my 82 Turbo has been a magnificent improvement to the whole braking experience, and I would recommend the system to anyone. It's changed the whole business of driving for the better.....Can't say anything about other models, though.

 

Agreed. Mine is still bedding-in but already a big improvement.

 

The only concern I have is the kit involves throwing away the backplate. There is no rear seal on the bearings on the original design, just a bit of felt, so I am not sure how well the water will be kept out of the bearings without the backplate.

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