I know guys put series I front calipers on the rear. Did a search and no luck (hard to pose a question). Since my other post bit**ing about my leaking calipers I thought I’d put fronts on the rear. Don’t have the unit out as yet but I can see the pads are wet, so the whole works has to go. The question is:
Same carriers, parking brake set up, etc.? Any clearance or unexpected issues? Must admit I’m lazy as I have the old rears and the defective, resleeved fronts in the garage attic and could compare them, but that not only takes effort on my part, but may not reveal a subtlety that actually doing the job would reveal.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
Why would you want to put front calipers on the rear? Wouldn’t you end up with horrible brake balance?
If you check my original description of my set up, notice I have 4 piston English calipers on the front. Despite what some have suggested or warned about, it stopped straight and true with the small originals on the rear and the big fronts.
The ser.1 E fronts calipers were 2 1/8" . In the '60’s Datsun used the same calipers on one of their models. You can still buy the Japanese calipers brand new, on line for $88 each at (factorynissanpartsonline dot com). Back then E drivers put these calipers on front and rear and even now still see no difference. Back then the difference between the Datsun price and the Jaguar price was huge, and I guess it still is. The part # is 41100-14600 .
If that works out it is one of the best tips I’ve ever seen. Even the “original” guys might not object since they are so hard to see.
If those are factory Japanese parts it would be truly golden.
Thanks!
They are painted green and the Japanese name is stamped on the side, but they are the same. I haven’t had a leak in them yet. On the other hand, I have had trouble with re-sleeves and re-builds that can get expensive to fix.
When I had my ‘64 OTS fully restored by specialists they installed the Nissan calipers. When I questioned it they told me that the Japanese copied the Jaguar calipers exactly so they bolt right on and that they would be trouble-free. Twelve years later the brakes continue to be exactly that…trouble-free.
Glad to hear. If I had the sense to search this years ago I’d be easily thousands of USD’s ahead and hours and hours of agony. Again, I’m happy with the 4 piston fronts, but really didn’t need them.
I wish I could find the part number I ordered but the Japanese calipers that I purchased a couple years ago (I think they are for a Datsun 2000?) actually say Dunlop on them and are silver:
Silver and Dunlop would be better, but I’m OK with green or whatever in the rear. I guess I’ll have a similar set up, but I’m not positive if the part number I ordered was for the relatively larger piston or not. OK with me either way. I need to see If I have the CuNi caliper lines left over - I think with the rear assembly out I’ll put the better lines on right away.
The guys who say ‘Just take the rear end out’ may not only be sort of right, they may be REALLY right.
I used the stock Jag E-Type parking brakes. I rebuilt them and had them plated. They work just fine. (I used the stock caliper brackets to hold the Datsun calipers).
The size of the pistons needs to matter Larry. Virtually all braking systems have a front to rear bias of 60/40. Jaguar achieves this by having smaller pistons in the back than the front. If you calculate piston area front and rear you will see the rears are 40% of the total area. You must NEVER alter this ratio to less than this (more won’t kill you - less may very well). What will happen under moderate to severe braking is that your back end will come around on you so fast you have no chance of catching it.
That is what is said: when I installed the Wilwood fronts, I experienced no sensible difference in pedal feel, travel, or (track tested) brake balance.
The Wilwood calipers I installed on the front have 1.75" diam pistons, 4 per caliper (9.62 sq in per wheel). With the 2.125" calipers in the rear (2 per wheel, 7.09 sq in per wheel) I have a front/rear bias of 58% front 42% rear. Very close to the 60/40 ideal. I can always install a proportioning valve in the system if the bias is off, but I suspect this is good.
If you increase piston size front or rear or both and every thing else remains the same you will get more pedal movement - immutable law of physics - you are moving more fluid, though you may not notice the extra movement, or the greater mechanical advantage to the pedal.
Doug - take the car to an empty parking lot where you can’t hit anything and at 30 mph hit the brakes hard, better if it’s wet. Then you’ll know
I understand the physics–and was prepared to do the front-to-back swap, based upon recommendations of folks in this here very Forum.
It never needed it. The pedal did not sink lower than it did with the stock front. I did a lockup test, on a track, and the fronts locked up long before the rears.
I never checked, but it’s possible way back, when Dad first prepped Tweety for racing, they did that swap.
All I know is I saved mucho dinero, over rebuilding the front Dunlops!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
20
Remember that six small pistons isn’t necessarily any more braking power than two or four larger ones. In fact, I wonder why six-piston calipers are even a thing.
There are other ways to alter brake balance, including going to larger diameter discs.
