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Rear Disc Brakes for a Sunbeam Alpine! Tiger?

cobraii78

Donation Time
Dan, I am very interested in a set of these for my Series V with stock rearend. Please let me know as soon as you have a price etc. Thanks,
Mike Spencer
 

Hoghead

Silver Level Sponsor
My problem on the Tiger is matching the rear brakes to the big Wildwood brake kit on the front, so this is not the solution for me. It may well work with stock Tiger front brakes, but I would need to know a little more about your parts spec to comment.
The Wilwood kit needs 15" wheels so a lot more options on the rear

This is not my first go around with rear discs, and I have learned a bit more since my 1980 approach of simply finding something that will fit on the rear, while using a proportioning valve to try and match the front brakes. Complicating the issue is weight transfer and all that entails, tire grip, tire size, pad coefficients, pad area, calliper piston area, rotor OD, fore/aft car balance, pedal ratio, proportioning valve slope, master cylinder bore, deceleration rate, centre of gravity height, ............ This latest rear brake design attempts to take these issues into account.

If one wants to use more common .40 street pads on the rear, then more clamping force is needed in combination with a larger OD rotor, to match the Wilwood fronts. The 93-98 Lincoln MK Vlll single 45.2mm piston calliper, on an 04 Mustang Cobra 11.65 OD rotor, in combination with a .37 slope Wilwood proportioning valve is a good match to the Wilwood front kit with .046 pads.

A .75” bore, dual circuit master cylinder is used to keep the hydraulic pressures up and leg pressure down as there is no servo in the system. Nothing new here, and I used one from a Ford Courier pickup. With the .75 master, leg force will be acceptable using the stock Tiger pedal ratio - a higher ratio pedal would be better.

The system is fitted now but I am now redesigning the bracket to rotate the calliper downward to gain a bit more calliper to frame clearance. These brakes will not fit using the stock 13” wheels.

The only bespoke part is the mounting bracket to fit the Lincoln calliper. Machine work is required to bore the hub on the Cobra rotor, drilling the rotor for our stud pattern, and facing the stock hub to insure it is flat.
 

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260Alpine

Silver Level Sponsor
Hoghead, Good solution to balance the larger Wilwood front brakes. The 87-88 Turbo Tbird and others tbird caliper.jpg tbird rotor.jpg uses the same caliper with a smaller diameter rotor with stock Alpine 4 bolt pattern. You would need a different bracket.
 
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Bill Blue

Platinum Level Sponsor
My problem on the Tiger is matching the rear brakes to the big Wildwood brake kit on the front, so this is not the solution for me. It may well work with stock Tiger front brakes, but I would need to know a little more about your parts spec to comment.
The Wilwood kit needs 15" wheels so a lot more options on the rear

This is not my first go around with rear discs, and I have learned a bit more since my 1980 approach of simply finding something that will fit on the rear, while using a proportioning valve to try and match the front brakes. Complicating the issue is weight transfer and all that entails, tire grip, tire size, pad coefficients, pad area, calliper piston area, rotor OD, fore/aft car balance, pedal ratio, proportioning valve slope, master cylinder bore, deceleration rate, centre of gravity height, ............ This latest rear brake design attempts to take these issues into account.

If one wants to use more common .40 street pads on the rear, then more clamping force is needed in combination with a larger OD rotor, to match the Wilwood fronts. The 93-98 Lincoln MK Vlll single 45.2mm piston calliper, on an 04 Mustang Cobra 11.65 OD rotor, in combination with a .37 slope Wilwood proportioning valve is a good match to the Wilwood front kit with .046 pads.

A .75” bore, dual circuit master cylinder is used to keep the hydraulic pressures up and leg pressure down as there is no servo in the system. Nothing new here, and I used one from a Ford Courier pickup. With the .75 master, leg force will be acceptable using the stock Tiger pedal ratio - a higher ratio pedal would be better.

The system is fitted now but I am now redesigning the bracket to rotate the calliper downward to gain a bit more calliper to frame clearance. These brakes will not fit using the stock 13” wheels.

The only bespoke part is the mounting bracket to fit the Lincoln calliper. Machine work is required to bore the hub on the Cobra rotor, drilling the rotor for our stud pattern, and facing the stock hub to insure it is flat.


I cannot see that you state a problem. What needs to be changed? BTW, what is a .37 slope proportioning valve? Sounds like it limits rear pressure to 37% of front pressure. If that is case, I'd say you should use Saturn calipers and experiment with rotor diameter.

Bill
 

DanR

Diamond Level Sponsor
Gentlemen, My sole intent is "Fitting Rear Disc Brakes to a STOCK Alpine & Tiger Rear Axle" not a different carrier/axle.

Application of the "KISS" principle: Keep it simple stupid, helped me stick to the stock Alpine&Tiger axle/carrier. An additional safety feature, fairly inexpensive without lots of modification for the everyday Sunbeam was and is my goal.

Even the simple idea of letting the prospective buyer purchase rotors direct from a Vendor and then preparing or having prepared the rotor to fit the hub makes for a potential Logistical problem in that not all potential buyers would have the expertise or machine shop available to drill and align the rotors for their Sunbeam.
 

Hoghead

Silver Level Sponsor
Hoghead, Good solution to balance the larger Wilwood front brakes. The 87-88 Turbo Tbird and others View attachment 18305 View attachment 18306 uses the same caliper with a smaller diameter rotor with stock Alpine 4 bolt pattern. You would need a different bracket.
I did not know that the 87-88 Turbo TBird was the same

Be very careful to get the 93-98 Lincon MK Vlll as the earlier callipers are for thicker .945 rotors and the piston will pop out of its bore when the pads wear if using the 04 Cobra .710 thick rotors. This calliper was also fitted to 93-97 T-Birds, and perhaps the Cougar and the Taurus, but do your homework on the years.
 

Hoghead

Silver Level Sponsor
Gentlemen, My sole intent is "Fitting Rear Disc Brakes to a STOCK Alpine / Tiger Rear Axle" not a different carrier/axle.

Application of the "KISS" principle: Keep it simple stupid, helped me stick to the stock Alpine&Tiger axle/carrier. An additional safety feature, fairly inexpensive without lots of modification for the everyday Sunbeam Alpine was and is my goal.

Even the simple idea of letting the prospective buyer purchase rotors direct from a Vendor and then preparing or having prepared the rotor to fit the hub makes for a potential Logistical problem in that not all potential buyers would have the expertise or machine shop available to drill and align the rotors for their Sunbeam.

I am using a stock Tiger rear axle, and understood from the title of your post you were uncertain if this mod would work on a Tiger.
While the front brakes on a later Alpine and Tiger are the same, the weight, weight bias, and centre of gravity height of the Tiger is different. Throw the typical Tiger mods into the equation and a new model is required.
I am all for a KISS solution for the stock Tiger Owner. Your design may well work on a stock Tiger, and easy enough to answer given the
CF of the pads F and R, pad area/height, and rotor OD. I can assume proportioning valve, MC bore, piston area, tire size, and tire diameter in the model.

For those with larger than stock front brakes another solution is required. Dan Walters came up with the 04 Mustang Cobra rotor idea and all I did was mate it to a bigger calliper. Perhaps there is a better or KISS way and I am all ears.

You might be able to keep it really simple and not do any machine work, but as the rotor is mounted to stock hub, that mating face must be true and parallel to the hub tapered bore. I did not do this the first time round and had .006 runout on my car - marginal, but I have seen worse on other Tigers.
Try it using the stock unfaced hub, check runout, then decide what you can accept
 

Hoghead

Silver Level Sponsor
I cannot see that you state a problem. (QUOTE)
Take a look at the Wilwood front kit specs - 11.75 rotors, radial callipers with 4 x 1.75 pistons, and with a nominal friction rating of .046.
The problem is that this is a lot bigger than stock Tiger/Alpine and needs correspondingly larger rear brakes for a balanced system.

(QUOTE) What needs to be changed? BTW, what is a .37 slope proportioning valve? Sounds like it limits rear pressure to 37% of front pressure. (QUOTE)

Making it more confusing is that it is really not a proportioning valve at all but more of a regulator.
Not all proportioning valves are the same slope nor the same knee point. The slope is the rate at which rear brake line pressure builds, after the point where pressure limiting begins (knee point).
Google is your friend - https://www.apcautotech.com/getmedi...f-bf7e4451801b/brake-proportioning-valves.pdf

(QUOTE) If that is case, I'd say you should use Saturn calipers and experiment with rotor diameter. (QUOTE)

More likely both a larger OD rotor, and larger piston area calliper is needed with the Wilwood front kiT
 

DanR

Diamond Level Sponsor
Thanks for the clarity that your rear is stock Tiger, Hoghead! I assumed your rear was non stock, I must read more carefully:)

My problem on the Tiger is matching the rear brakes to the big Wildwood brake kit on the front, so this is not the solution for me. It may well work with stock Tiger front brakes, but I would need to know a little more about your parts spec to comment.
DanR's COMMENT: My idea is to adopt a caliper compatible to only stock front brakes. The Saturn calipers are 32mm pistons.

Hoghead: ....."so this is not the solution for me."
DanR: Assuming again, the reference is to the Saturn?

Hoghead: Complicating the issue is weight transfer and all that entails, tire grip, tire size, pad coefficients, pad area, calliper piston area, rotor OD, fore/aft car balance, pedal ratio, proportioning valve slope, master cylinder bore, deceleration rate, centre of gravity height, ............ This latest rear brake design attempts to take these issues into account.
DanR: Agree there are complicating issues you mentioned, but I believe have been
successfully applied.

Hoghead: The system is fitted now but I am now redesigning the bracket to rotate the calliper downward to gain a bit more calliper to frame clearance. These brakes will not fit using the stock 13” wheels.
DanR: "These brakes.... " for clarity, are some you have mounted on your Tiger! I am not yet satisfied that the Saturn Caliper will fit the 13" Wire or Steel Alpine/Tiger wheels.

Hoghead: The only bespoke part is the mounting bracket to fit the Lincoln calliper. Machine work is required to bore the hub on the Cobra rotor, drilling the rotor for our stud pattern, and facing the stock hub to insure it is flat.
DanR: Same machine work for the Saturn Rotor.

And thanks for your insight! I am not trying to reinvent the wheel:) All good advice is most certainly appreciated. Hope you get a solution for your Tiger too!
 

Warren

Bronze Level Sponsor
There is certainly a lot to consider. I have stock Tiger front brakes and the Fiat X19 rears. The e brake works well .
I have autocrossed the car and done really well on a 1 and 2 gear course keeping up with cars having 60 to 100 hp more.
I'm interested in a change as I have the single Wilwood master and I like it but it's aging . I'm really happy to not have to adjust brakes or mess with a proportioning valve. I had one of those on my Falcon with a disc brake conversion in the front. I'm happy to see guys make more than one adapter system and sell on their mods . I like to see a less expensive alternative to Wilwood front and rear systems. Like I'm really going to need to do repetitive panic braking or track the car on city streets to the local C and C.
 
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Hoghead

Silver Level Sponsor
If Dan can make this work, then seems like a great bolt on, single source, solution for a stock front brake car.
 

DanR

Diamond Level Sponsor
I have a question
If this works ? for Capris DIsc Brake REverse Caliper - RS Motorsport - Capri      DSCF9194.JPG why want this work ? for wire wheels Rear DIsc with rotor inside of hub adequate clearance        20191221_175523.jpg OR This ?Rear DIsc with rotor inside of hub adequate clearance        20191221_175516.jpg Notice the calipers are fitted behind the hubs.... it appears the caliper and hub mate flush in the 1st PIC. The calipers and hubs do so in the 2nd & 3rd PICs also.
 

260Alpine

Silver Level Sponsor
Dan, May work on the wire wheels. A lot of the conversions just bolt to the brake drum. The 13" steel wheel needs the support of the original hub. I've never seen a rotor behind the hub or axle flange on the rear. Probably no one wants to pull them to change rotors. Lots of front hubs do as you have shown with the Capri front.
 

Bill Blue

Platinum Level Sponsor
Dan, as near as I can determine, the caliper clears the wheel. The interference appears to be located at the outermost caliper bracket where it holds the sliding pin. If so, it looks like it would be very lightly loaded and could be trimmed without sacrificing strength. Could you post a photo showing the contact point on the brake component?
Bill
 

DanR

Diamond Level Sponsor
I don't think the back side will run true and have the support needed without the flange.

Dan, May work on the wire wheels. A lot of the conversions just bolt to the brake drum. The 13" steel wheel needs the support of the original hub. I've never seen a rotor behind the hub or axle flange on the rear. Probably no one wants to pull them to change rotors. Lots of front hubs do as you have shown with the Capri front.

Dan, as near as I can determine, the caliper clears the wheel. The interference appears to be located at the outermost caliper bracket where it holds the sliding pin. If so, it looks li Could you post a photo showing the contact point on the brake component?
Bill

John, I have six or eight hubs all have a machined "backside" that measure true based in comparsion to the front finished face. By rotation with the hub on the axle and caliper mounted (backside) I can not detect any out of balance (untrue). Part of my concern is what appears a lack of support between the hub and caliper at the backside. More study?

Jim, Unless I am not seeing what I think I am seeing the PIC I "Copied" from the site you provide me with: the link at RS Motorsport, in POST #54 the PIC shows a rotor behind a hub like I am referring to in my "other wire hub/rotor" 2 pictures. Maybe I am not understanding what you mean? Below is a hub with the rotor in the rear as I am
proposing for 13" wire and steel wheels
file.php

If the only reason is that no one wants to be bothered with pulling the hub to a make an improvement on their brakes seems kinda dumb. IF front hubs can be mounted that way? Why not rear?

Bill, It does look like it would be very lightly loaded and could be trimmed without sacrificing strength "at one point ( along the bottom) but at the top edge it may cut into the body too much! I intent to try mounting the caliper a bit closer to the hub by shortening the space between My Bracket and the OEM bracket another small amount. I have already spaced it down some.

Back for more test...
 

260Alpine

Silver Level Sponsor
4 lug spacer.jpg Dan, that picture is a front Capri hub with spacers inbetween the caliper halves to allow a vented rotor to fit. That is what I proposed for the front of the Alpine. The Capri caliper is identical to the Alpine except for Metric bolts and cotter key size. As far as I know rear discs are always on the outside of the hub. You can use a spacer with dual pattern to clear the wheel. The rear track is a little narrow anyway. Bill is right on seeing what hits and maybe clearancing there?
 
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