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MG Midget and Sprite Technical - Princess calipers

Hi, ive got some princess 4 pot calipers, hole centre pickup alright, what discs can i use either vented or unvented and what other thing do i have to alter.
PP Lawson

Princess calipers are a direct bolt on replacement for the stock caliper - we had them on the racer.

They have to be used with a solid disc ie un-vented.

Our set up was using modified Allegro discs which, IIRC bolt straight to the back of the hub because they have the correct bell offset, however they need to be turned down to just under 9" diameter.

The other problem you will have using Allegro discs is that, owing to the size of the bell, you have to modify the pads very slightly (remove a section of the centre of the leading edge).


Deborah Evans

And:


Deborah Evans

Another option would be Spitfire discs but these would require a spacer to be machined up to go between them and the hub.
Deborah Evans

I am so envious of you folks over in GB who have access to all those neat parts such as the Princess calipers and Allegro discs. Wish we had the same over here, unfortunately those are extremely rare on this side.
Bill Young

Bill,

www.petermayengineering.co.uk

I'm sure Peter will ship overseas!

Debs, are you and/or Jason coming out to play this season?

Nigel
Nigel Pratt

Princess calipers are now available as new units - there was an advert in one of the Classic Cars magazines back in August I think.

I've just put huge brakes on the racer (along with alloy front hubs) so I'm guessing our car has the biggest brakes of any Class B car - I'll do a separate thread about them because I will be offering a kit.

Nigel, I am certainly hoping Jason will be back out this season since I've just refreshed the engine! Last year financial constraints lead to him not racing but (I think) these have now been overcome. Having said that I won't be around for the whole season because I am spending a lot of time in the USA, although I hope to do the Birkett again.
Deborah Evans

So are you going to bring any of those kits with you?
David "wrong side of the pond" Lieb
David Lieb

"because I am spending a lot of time in the USA"

Deb, from all of us on this bbs: thank you for going over to get Prop's engine running! :)
Arie de Best

LOL Arie, unfortunately New York State is a wee bit of a way from Missouri otherwise I would!

David, watch this space if plans come to fruition.
Deborah Evans

Bill - am doing a trip to Canada in April/May, if you need any parts and I can get them in for you - let me know and I'll at least get it some of the way ...! Probably wouldn't be tripping south of the border - paperwork is nightmarish enough, without adding to it :(
rachmacb

Rach, thanks for the offer but unfortunately there's nothing left in the car budget right now. It would have worked out pretty good otherwise as I have relatives in the Toronto area and some good friends going up for the MG 2010 meet during the summer.
Deborah, it's hard to see from your photos but how much clearance is there between the caliper and the lower A frame at full lock? That's where I ran into clearance problems trying to adapt 4 pot calipers to my car a few years ago. I tried a Volvo as well as a Mazda caliper but both were too long and would hit the lower A frame at full lock and compression/extension of the suspension.
Bill Young

Speaking of Princess calipers, I've found these:

http://www.hispecbrake.co.uk/calipers/b4%20Princess.htm

will they bolt onto a standard midget hub? I'd assume so if the normal princess ones do, they're not all that expensive (makes me think what's wrong, they're under half the price of a KAD set....)

Rob Armstrong

LOL Arie, unfortunately New York State is a wee bit of a way from Missouri otherwise I would!


DEB you sexy babe!

Let me know when your comming ... Definately an insentive to get the midget running...Ive always wanted to spend a weekend at the chelsea hotel in lower manhatten. sort of a hippie / artiest area of the city

thats right ... same place that leanord cohen got head from janis joplin on the un-made bed, and where Sid Vicious of the Sex Pistols shot and killed his girlfriend, bob dylan lived and snorted so much coke no one knows what the heck he is singing, the guy that wrote the book and super un-godly boring popular movie space odasey 2001...lived there also HAL, I must contact earth, I cant let you do that dave"

http://www.hotelchelsea.com/

Here is a youtube song by L. Cohen on the chelsea hotel...I Just love this song, its how I became more aware of the chelsea then in just passing

http://www.youtube.com/watch?v=pGfgMYfdBFc

Jez what a cool place and a great song.

So DEB, seriously, let me know When your comming state side.
Prop

Those HiSpec callipers should bare no interference problems.

"Calipers are available to suit discs from 12mm to 35mm."

Not very clear what dimension its reffering to.
Alex G Matla

Alex

Thickness of the disc - obviously vented discs are thicker than solid...

Deb

'Biggest brakes on any Class B car' - probably just about.. Although I've been running Capri 2.8 vented discs (245mm/9.65") and Wilwood calipers since 2000...

Cheers

James
James Bilsland

Bill, there are absolutely no clearance problems between the Princess calipers and the wishbone at full lock whether under bump or rebound.

Our car was raced extensively throughout 2007 and 2008 by both Jason and myself (including the 2008 Birket 6 hour relay race at Silverstone) and we had no issues in the braking department.

In fact the brakes on the car were so good that the first time I ran the car at Snetterton I hit what I thought was the braking point for the entry to the 'Esses' at the end of the 'Revett Straight' (braking from around 130 mph) and ended up having to re-accelerate back to the corner apex!

The reason for binning the Princess calipers was not performance but weight - they are uber heavy!
Deborah Evans

Ive got a pair of princess calipers in the garage that my son removed on his converted Honda CRX to fit Alloy calipers .
2 questions will they fit behind all 13 inch wheels , alloys and steels . And whats the exact size the Allegro disc needs to be turned down to, just under 9 inches, but how much under? ..
R Mcknight

We ran the Princess calipers with KN Minotaur 13" x 6J and 13" x 5.5J wheels with absolutely no problems.

With the standard Rostyles we use as 'transit wheels' we used a 5mm spacer and, again, there were no clearance issues.

Unfortunately I don't have access to the racer just now because it is down near Winchester and i am in deepest darkest East Anglia. I will be going back down there in a fortnight so I will measure them for you.
Deborah Evans

Deborah,
Ive got all the dims of discs and calipers on my cad system now, just cant see how you managed to fit allgro discs. The bells on the discs are not a square section like the midget, they go out at an angle towards the caliper. If i were to use this combination i would have to move the caliper out 10mm so that the calipers would not foul the bells on the discs. The only thing i can think of is the offset, hole centre to top edge of caliper (19.5mm) is not the same as yours.

Phil
PP Lawson

Phil,

As I stated earlier, you have to turn the Allegro disc down - I should be able to get the diameter for you next W/E.

The Allegro disc bolts directly to the Midget hub. As you say, the Allegro disc bell is angled but this produces no clearance problems with the Princess Caliper (albeit the caliper is close to the bell) which bolts directly to the Midget upright.

Where there is a problem (and I quote my first post):

"The other problem you will have using Allegro discs is that, owing to the size of the bell, you have to modify the pads very slightly (remove a section of the centre of the leading edge)."

In other words, owing to the angle of the bell and the proximity of the caliper it is the BRAKE PAD as needs modified.

We ran this set up for 2 complete seasons with modified Mintex 1177 pads with no issues.

I'll try and get some more photo's next W/E.
Deborah Evans

Hi Deborah, you were going to try and post some more photos and also give cut down allegro disc diameter, any luck yet.. Thanks
R Mcknight

Deborah, I've looked around on line a bit for the new Princess calipers, but so far the only thing I've found is the HISpec aluminum bit and those are pretty dear. Peter May doesn't show anything in his site. Does anyone have a source or even some engineering drawings of the size that I can use to compare with some calipers available here in the US. Looks like Wilwood might have a caliper that would fit, but would need a custom mounting bracket machined as none of their radial calipers comes in a 3.25" center mounting.
I'm upgrading the brake masters to a three cylinder configuration with a balance bar and would like to install some new front calipers along with that if I can. What size master cylinder bore do you run with the pricess calipers and what is the piston size in them?
Bill Young

I checked out the Princess calipers, but boy, ain't they heavy??? Decided against for that reason alone.
D le Versha

I think the calipers we need are the Wilwood M16 Powerlite 4 pot solid UNF . If the princess calipers fit onto a ford escort , then these calipers must fit onto the sprite as they are replacement for the heavy Princess calipers .


http://www.rallydesign.co.uk/index.php?cPath=562_588

Or am I barking up the wrong tree . Good price as well £99 , same price as new heavy cast calipers on Ebay .

Roy


R Mcknight

Roy, I would be very interested to know if you find out whether these will fit or not. Sounds like a good solution at a good price!! I guess you would need to fit Allegro discs??
David Banks

i think that's £99 each +VAT
d cusworth

Hi David , spoke to my son who bought a pair of Wilwoods from Rallydesign. They fit to the Ford upright using an Alloy adaptor . So if Princess calipers fit a Ford Escort and bolt straight on then these calipers are a direct replacement using the adaptor that is supplied for the Ford M16 fitment .

I will be doing this conversion in the future, but have more pressing mods to do first .

Oh yes still waiting for Deborah to give us the Allegro disc diameter. HELLO DEBORAH .

Roy
R Mcknight

according to my period Unipart catalogue, Allegro discs are the same as Maxi, and are 246mm x 9.5mm
HTH
David Smith

Hello Roy - would you mind to keep me posted on your plans to fit these Wilwood calipers etc??? My email address is listed above. Cheers. David
David Banks

This thread was discussed between 10/02/2010 and 25/03/2010

MG Midget and Sprite Technical index

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