Wilwood brake upgrade

[meeka]

I am planning to upgrade the front brakes on my 1968 2+2 with a Wilwood package from XKS. I'd be grateful if someone could let me know whether the existing master cylinder will still be adequate or whether it also requires any change or upgrade. Many thanks, Graham.

[abowie]

As long as it is in good condition it will be fine.

[vipergts]

Out of interest why Wilwood? It's more than likely that Ive been doing something wrong but I can think of 3 occasions where I have fitted Wilwood calipers to various cars and NONE of them have worked well. I know the US are keen on them. I use AP for most applications now

[trondvo]

I have Wilwood callipers with non vented discs on my '61, very happy with the setup. I bought them 10 years ago and they were bolt on, restored the originals and stored them. The brakes are well balanced and work fine together with the original rear callipers, original master cylinder is perfect with Wilwood's, at least the non vented version. Will also install a Wilwood set in the '62 I am restoring.

[PeterCrespin]

I have wilwood calipers with non vented discs on my '61, very happy with the setup.... Will also install a Wilwood set in the '62 I am restoring.

There are lots of these calipers, which model/version?

Pete

[trondvo]

Sorry, my first answer was a little misleading, you *must* have the adapter but no modifications to frame/etc. Wilwood 120-4993, they are now out of production. There may be better sources but here is one.

http://www.summitracing.com/int/parts/w ... /overview/


Summit suggest 120-6818 as replacement

http://www.summitracing.com/int/parts/w ... /overview/

JCNA writeup on Wilwood install.
http://www.jcna.com/library/tech/tech0021.html

Maybe our host or someones machine shop could make a batch of these adapters if enough interest. The rest of the parts are regulars service shop items, I will shoot a photo of the setup on my 61 and post it.

[trondvo]

Pix of wilwood on my '61





Barely visible with the black calipers.

[jag68]

I used Wilwood's (front and rear) on a couple of E Types that I raced for about 14 years. I have mixed (probably mostly negative) feelings about them. As to compatibility with the master cylinder you will have a problem if you use Wilwoods with large pistons. You need to try and match the total square inch area of the Wilwood pistons to the stock piston system. Too big and you will need to push so much fluid that you can (as I did initially) have a pedal that goes all the way to the floor. Stock Girling or Dunlop pistons at 2.125 dia have an area of 3.55 sq. inches. You will be ok if you use 1.62" dia Wilwood pistons in whatever caliper you buy (I'm assuming that they are Dynalites) which will give you 4.12 sq inches per side of the caliper - a 16% increase. Also - you can't put a bigger master cylinder on your car without completely changing the power boost system - this is not something you want to get into - trust me on this one.

[jag68]

Graham I should also add that different piston sizes in the front undo the work that Jaguar did in balancing the system. Bigger front pistons mean the rear brakes do less work.

[trondvo]

According to the JCNA article Wilwood fronts and installing the old front cylinders on the rear calipers would be wise, but thats a little more work than I wanted. It may happen when I rebuild the rear end or clean up and detail the IRS.

Since my car is for summer cruising the upside of the Wilwood fronts far beat the potential disadvantage. You can install a dual brake proportioning system and fine tune the brakes. Just a little piping and two brake bias/proportioning valves needed, plus a lot of testing. My car is better with the wilwoods, thats a personal opinion based on a relaxed driving style.

All said I am considering putting the originals back on the car, may want to have them sleeved first. They should be good enough for the action the car see and brake balance may be more fun than straight line stopping power. I like the idea of cars being just like they made them back in the days, including flaws and everything.

Of course racing is a whole different story and it may be true that you get what you pay for.

[jag68]

I'm sitting here with a glass of Scotch and nothing to do so I thought I'd do some calculations. Assume you used the 2.125" inch pistons (front pistons) on the rear, and Wilwoods with four (per caliper) 1.75" pistons on the front (biggest pistons available on the DynaLite I believe). The stock setup has a total piston area of 23.82 square inches (s.i.) consisting of 14.2 si in the front and 9.625 in the rear. The front back ratio for balancing is 67% . The upgraded system has a total area of 33.25 si consisting of 19.25 front (remember 8 pistons here) and 14.2 in the back, for a ratio of 72% So far so good - it's balanced enough. However.....

The stock master cylinder on a 4.2l is .750 in dia (.442 si) and has a maximum stroke of 1.3" (figures from the Jaguar manual). If the brake pads move 1/64 of an inch (.0156") from retracted to contact the disc with force how much fluid must it push. In the stock system .372 cubic inches (ci). In the upgraded system - .52 ci. Problem is the stock piston can only move 1.3 inches max with a total fluid displacement of .57 ci. I don't actually know how far you have to move the pad for full hard contact with the disc, say in a panic stop, because you will get some flex in the calipers, and also expansion in the flexible brake lines sopping up extra fluid. Anyway you are way too close to disaster here for me. (Bye the bye switching to "motorcycle" brake lines (stainless steel encased) for the flexible lines will give you a noticeable improvement in brake feel - there really is a lot of stretch in the stock lines.)

[trondvo]

I think they recommend the small piston Wilwood caliper, I have not had enough morning coffee (its too early for Scotch) to digest your calculations but very interesting. :) Good points, I may reconsider the brake setup on my '62 FHC which will be a grand tourer as it was intended. The '61 will have to live (happily) with Wilwoods for some time. What is the common opinion on the complete Coopercraft setup? Any other brake systems for a grand tourer? Want to use the 62 coupe between Norway and down and over the Alps a couple times a year (5 speed is on the list).

[Heuer]

I only have experience of the Zeus callipers and they have been superb over 45,000 fast miles and many Alpine passes. They look unassuming, are very similar to the originals in most people's eyes and have been tested over millions of miles as they were developed for London Taxis, then Land Rovers and finally found their way to classic cars. Great company to deal with, no bulls**t about funky colours/logos/hewn from billet/specially designed for the E-Type etc etc - they just do the job brilliantly. I asked CMC whether my brakes needed 'upgrading' and they said they were as good as any E-Type they had driven and to leave them alone! For the Rallye des Alpes I fitted S3 ventilated front discs (cross drilled to wipe the pads clean) and Greenstuff pads and the set-up remains that way to this day