- This topic has 29 replies, 5 voices, and was last updated October 9, 2005 at 4:49 pm by
.
-
Posts
-
-
The old tech e-mail section contains a post where the writer claims to have used volvo 4 piston brake calipers on his sunbeam. My local parts guy was nice enough to order one in for me to look at (this was a Girling 4 piston front caliper from an early 70’s volvo 140 series if my memory serves me). The main obstacle seems to be the bolt pattern – the volvo measured 3” (center to center), while the sunbeam is more like 3 1/4″. Can someone enlighten me as to how the volvo parts were used?
Thanks in advance! -
I think we could just have the holes cut with a mill so they are the same spacing as the Alpine caliper. Have been crawling the junk yards looking for one to try either the Volvo or a Toyota caliper but so far no joy. I did look at a Alfa caliper and while it centers it is also to far out from the center of the rotor.
-
I didn’t think there was enough (any?) material there to cut wider mounting holes, but if you find one take a look and see if you agree – maybe I’m missing something.
In researching the subject of 4 piston calipers, I found an interesting website: http://www.outlawdiscbrakes.com their model M-16 has 3.25″ spacing, and appears to be the same caliper that the Jensen Healey crowd is using successfully (see http://www.jhps.com big brake kit).
Does anybody have any experience with these?? -
You could be right on the hole moving but being it is only 1/8th inch it could work. I am still looking for a set to try this on my S3.
On the Outlaw calipers… ummm I just happen to know a little something about those…
have a set on my SV V6 project what I can tell you is they bolt on will require some work for the line to fit up and have only a very little bit large piston area than the stock caliper but they do weight much less. The car is not driving yet so I cannot say how much if any they improve braking. I found a somewhat local speed shop who ordered them for me and drop shipped them from Outlaw. The calipers were somewhere north of $400 with pads and shipping, they are very slick looking by the way. -
-
Todd,
The pads are a bit bigger have not measured and figured surface area but would guess a third bigger. Have been told the piston area is what makes a difference in clamping so if all things are equal such as caliper distortion and ability to resist boiling then the same size piston area no matter the number of pistons will give you the same braking. I want to think the more modern design of the Outlaw caliper would result in better brakes but…. will just have to wait and see.Since you are interested in brake upgrades here is a view of the rear brakes I am working on.
This is on a Tiger rear end but would work on an Alpine rear also. The rotor is off an alfa has been reduced in diameter and also had the center hole opened up to fit the hub. The caliper is from a Merkur Scorpion, made up my own weld on bracket. The piston surface area of this caliper is right at half the front caliper so should be balanced from what I have read and learned about this brake stuff.The Merkur caliper has a built in E brake that is cable operated the plan is to use a set of Ebrake cables [Lokar copies] and hook it up to the stock e brake handle.
-
Very interesting Jim! Are you running a stock master cylinder or something special? Are you planning on using a booster? I eliminated mine many years ago, but at today’s speeds (80mph very common on our local interstates) I feel like I’m at a disadvantage vs modern cars. Going back to a booster will create some under hood packaging issues for me due to the layout of my V6 conversion, so I have been investigating other possible options. I also had stumbled across the Toyota 4 piston caliper – although I haven’t found any specs on the mounting spacing. Do you have this info? Maybe its time to visit my local parts guy to see if he has one on the shelf.
-
I have a NABCO master cylinder that I am going to use think it is off a Colt. Dual circuit with a .700 bore.
figure to have to use a proportioning valve with this mix of brake parts but am not over worried about it.I had thought to use a servo [actually have a new Lockheed in a box] but decided to go dual circuit so that pretty much ends any thoughts of a servo on the SV.
The Toyota calipers are pretty common and the parts house will most likely have a set on the shelf, the bolts are on 3 1/2 inch centers.
Had give up on figuring out how to put a set of cheap 4 piston calipers on an Alpine but your post and the S3 I just got that is minus front calipers sparked my interest again. Located a set of Volvo calipers today at the junk yard so tomorrow I will see if I can HB them on the car. I had forgot the volvo units have two lines feeding them but that will be cake if I can over come the bolt spacing.
-
-
-
Jim E-
I am interested in more info on that master cylinder. It looks like it will bolt right up in the original location.
Do you have part numbers and availability? What other changes, if any, did you have to make to get it to work? What about the actuating rod (a.k.a. the clevis rod) – could you use the original one?
Could you write a tech tip for the Rootes Review?
Thanks.
Fred Baum
Editor, Rootes Review -
Jim E-
I am interested in more info on that master cylinder. It looks like it will bolt right up in the original location.
Do you have part numbers and availability? What other changes, if any, did you have to make to get it to work? What about the actuating rod (a.k.a. the clevis rod) – could you use the original one?
Could you write a tech tip for the Rootes Review?
Thanks.
Fred Baum
Editor, Rootes Review -
Fred,
I do not have the part number but these NABCO master cylinders were used on lots of imports so should be simple to figure out, I will work it.The fit to the hole in the firewall is good, the rod that came with the unit I have is adjustable and should work with no problem. Think it would not clear the rear carb on a stock Alpine cannot say how it would do on a Tiger.
I have not got to the point of installing this M/C yet so can only tell what I think not what I have done on this. May or may not be willing to write this up will think about it when I see how it goes would also like to check and see if it will clear or not on a stock engine car.
-
Jim,
Obviously your satisfied that you have enough material left in the mounting area after enlarging the holes. If you have the opportunity, perhaps you can snap a picture of the modified caliper.
As far as the plumbing goes, what you need to do is to move that nice dual master cylinder over from the SV! My understanding is that Volvo plumbs their brakes so that they have 1/2 of each front caliper + one rear brake on each circuit.
You don’t appear to need any help, but if you are interested in how someone else handled the plumbing check out http://www.jcna.com/library/tech/tech0031a.pdf (I found it amusing that someone with the resources to run a Jag XKE would object to paying for 1 hour of machine shop time.)
We are all looking forward to your road test results and the Volvo vs Outlaw comparison test!! -
The piston area of the Volvo caliper works out to be the same as the stock Sunbeam caliper so there is no advantage on paper as far as clamping force goes.
Used a die grinder and rat tail file to open the holes up would be better to have it done on an end mill. Seems like there is enough material in the mounting area for this to work. Still I am not suggesting anyone try this or any other brake modifications on my word.
Thanks for the link will take all the help I can get!
-
-
-
Yeah mostly there is no advantage other than you can buy a set of these at the corner parts house pretty cheap and rebuild kits are easy to get.
Same goes for the Outlaw M16 caliper the piston area is the same as the stock caliper. But the Outlaw is only 3 pounds or less.
The Toyota caliper might be a better choice for more piston area.
I had heard for several years of the Volvo caliper being used had never seen it done or even heard how it was done. Did not know the piston area was the same until I got the junk yard calipers home and measured. With the plumbing issue and the piston area being no larger I would not suggest anyone use the Volvo caliper.
-
I read a quote on the Internet (probably the same place Jim did) that clamping force (braking) is only increased by increasing piston size. Based on what I learned in high school physics class that is a true statement, but I believe it is an over simplification of the braking system in our cars.
If brake pad size was irrelevant, there would be no reason to make your pads any larger than your pistons. If you look at any modern high performance car you will see multi-piston calipers, large brake pads and big rotors. When I sent an e-mail to England asking about Austin Princess 4 piston calipers, I was informed that they are almost impossible to find, because the MG & Triumph club racers buy them all up. I assume these guys aren’t trying to impress the chicks – they buy them because they work better.
Perhaps John or another club member can discuss this issue on a more scientific level then I can. Otherwise perhaps we can do a comparison
test between the cars Jim has modified and stock.In answer to Johns question above, Beck Arnley rebuilt Volvo calipers available from Rock Auto for under $40 with no core required. I don’t think you can rebuild your Sunbeam calipers for anything close to that.
-
You would think the 4 piston and larger pad would be better but not by the numbers. Have had this explained several times by several different folk. Being I am no smarter than I aught to be I bow to the numbers and hope the final product is at least as good as the stock set up.
I have found with stock calipers that the cheap semi metallic Saab pads seem to stop better. Key word here is “seem” have no real test data other than seat of the pants feel. Still for $20 and a few minutes to swap the pads it is a cheap date.
Oh and the Saab pads do not seem to eat the rotors.
-
Jim,
I found info on the Toyota caliper pistons: they have diameters of 1.685 and 1.345 inches per side (leading piston is larger). What measurements did you get for the stock Sunbeam and Volvo pistons? The outlaw M-16 pistons are 1.5 inches each per their web site.Thanks for the tip on the Saab semi-metallic pads – is there a particular Saab model & year to ask for, or should I match them up by size?
-
-
-
I have been trying to post this for a few days but it hasn’t gone.
I’ll just ramble on here for a while. When fitting a different front brake system to a Sunbeam, I would rate the selection on the following criteria. This is not necessarily in priority order.
· Lighter weight
Lighter weight of the brake assembly improves the ride and handling· Increased piston area
Under equal hydraulic pressure, the clamping force of the caliper is only increased by increasing piston area.· Larger disk diameter
Brake torque is a function of the clamping force, the friction coefficient between the pad and the disk and the radius of the pad centroid from the axis. As an example, if you increase the piston area by 20% and the disk diameter by 10% you will increase the braking torque by 32%. The downside is the larger package.· Vented disk
Although a larger brake pad area is an important criterion, vented disks are more important. Most modern cars have vented front disks that have vastly improved cooling. Because the Tiger is a light vehicle this may not be an important criteria but there must be a performance improvement to give us justification for the modification, right?· Increased pad area
Brake pad size is not irrelevant. The coefficient of friction of the pad on the disk surface is generally dependent on the pad material and the pad and disk temperature. This is where pad size becomes relevant. Passenger car pad material is selected that has a coefficient of friction that remains consistently high under normal operating conditions so that the driver experiences good braking performance. If the brakes over heat, as when the car is going down unusually steep grades the coefficient of friction reduces drastically so fading occurs. For this reason, larger pads will give better braking because they can absorb more heat before fade.
When racing type pads, usually high metallic, are used, a different phenomenal occurs. When cold, these pads have very low friction and when hot the friction is high. When with these pads are used in a road racecar, the temperature stays high while racing so the braking torque stays high, minimizing fade. If used in your normal passenger car, the pads stay relatively cool so high pedal pressures are required to stop the vehicle.· More pistons
Smaller multiple pistons will fit within the pad area and spread the clamping load out evenly to reduce uneven pressure across the pad. You can only count the pistons on one side of the disk.· Smaller package
If a smaller package were found that would allow the disk and caliper to move outward, the steering arm could move out and allow an improvement in steering Ackerman.· Low cost of installation
Machining is an expensive proposition if you have to pay someone to do it. Finding parts that can be retrofitted with a minimum of machining would make the modification achievable for more of our members.· Available new and used parts over a long term
There must be used parts in junkyards that fit. If parts are used from a low production car, it sometimes doesn’t take long before the replacement parts cost more than Sunbeam parts. I modified my rear brakes using Mazda 1985 RX7 components because the junkyards were full of good parts. Now they are all gone around here and if parts stores have them they ask a premium price.· Looks good
When we show these brakes to someone it’s nice to hear “Wow” when they look at them!· Other
Now, tell me what I forgot to mention.I’m interested in the ideas that some of you have and I hope you will keep putting them put them in this Forum. For your information, I fitted a 2002 Mustang Cobra caliper with a 10”x 1” vented disk to a Sunbeam spindle. It will fit on either a Tiger or Alpine and have an increased braking torque of 43%. That increase would cause a front to rear brake balance problem. It looked good with the polished Cobra name on it. However, because of the heavy vented disk, the assembly weighs 2.6 lb more then the Sunbeam assembly. I feel this is unacceptable.
-
Thanks John! That was very informative. One followup question that I think I already know the answer to: The weight of your wheel/tire package would also be a factor. More rotating mass would logically seem to be harder to stop. I noticed a big difference when I “upgraded” to TRX aluminum wheels – I could no longer lockup the brakes. The wheel/tire combo weighed about 5lb more than the steel wheels I took off, but also greatly changed the shape of the tire contact patch. So its hard to say exactly what caused what.
By the way, didn’t you use to run TRX tires on your Tiger? I understand they are out of production now.
Jim, I agree with all your calculations except for the Sunbeam. I get 3.54 – or as you said – basically the same as the Volvo and Outlaw. I don’t know that the 3% increase offered by the Toyota would even be noticeable.
-
I have been following this thread with interest and have a few comments.
First, the equation for frictional force between rigid materials does NOT include the contact area. The only factors that matter are the materials and the force pushing them into contact. A simple explanation is that if you double the contact area, you also cut the contact pressure (PSI) in half so the net effect is zero.
Second, when different size caliper pistons are used, the larger piston is on the TRAILING side to equalize pad pressure.
Third, if you use a caliper with more piston area (to me, 3% is not a significant difference), what are you going to do about brake balance? By all accounts, the rear brakes on an Alpine / Tiger are basically along for the ride and parking. Increasing the front brake force is not going to help the situation.
Fourth, the Volvo / Capri calipers should provide the same braking performance as the Alpine pieces at a drastically lower cost. Has anyone noticed what VB thinks a set of reman Alpine calipers are worth?
Finally, I think the real issue is the non-vented rotor. The Alpine brake setup was state-of-the-art in 1959, but technology and driving conditions have changed over the last 46 years. A system that can handle more than a couple of hard stops from high speed before the fade monster shows up would be nice. Dale’s Restorations offers a vented rotor setup that uses a spacer in the Alpine caliper for $250. There are lots of other possibilities, but they are probably going to cost considerably more and will probably require larger wheels.
That’s about a nickels worth.
-
One good nickel deserves another!
1. The “poor man’s” rear brake upgrade is to switch to Series I/II rear wheel cylinders. These are 7/8″ vs .70, which is a 56% increase. I found an interesting website (by a TR6 owner) who made this change and documented the results: http://www.cs.du.edu/~ljanssen/tr6_brakeinstall.html.
2. Keep in mind that our discussions are based on “all things being equal”.
The trade off for increasing piston area is increased brake pedal travel. If we are too aggressive in our upgrade, we run the risk of running out of travel, and we will have to increase the master cylinder diameter. Once we do this you have changed our mechanical advantage, which is directly proportional to the areas of the two cylinders (or cylinder and piston in this case). This is why it is normally recommended that you use the smaller diameter Series I/II master cylinder when removing the servo – it increases the mechanical advantage.3. I’ve owned my Alpine for 26 years and can’t say that I’ve ever experienced brake fade. Perhaps it is the way I use the car (touring/commuting- no autocross or competition of any kind). My desire is to improve the first stop – I’m not so worried about the 4th or 5th. I’d like to find a cost effective solution, since I’m the only person in the family that can drive it.
-
Yes Todd, the whole tire, wheel, brake, spindle and suspension contribute to undesirable unsprung weight.
I still have Michelin TRX tires. I like the wheels so I spend the premium on tires from Cooker. I just replaced them after 15 years and 50,000 miles because of all the discussion on tire age. When I got them off, there were no cracks or checking that would lead to failure but they were beginning to get worn and hard. For the price of the rear tires alone I could have bought a complete set of wheels and tires.
As for rear brake effectiveness, the rear is the first place to start to improve Tiger/Alpine braking. By replacing the poor performing rear drum brakes with proper disk brakes you then start using the rear to help stop instead of just the fronts. Because disk brakes are self-adjusting, you drastically reduce pedal travel the same time. You can then use a smaller master cylinder, eliminate the lousy booster and end up with less pedal travel then stock. You have to be concerned if you increase the front piston area too much you will affect the front-to-rear balance. Rear disk brakes are also lighter!
-
-
Actually, I just read an article (discussing modern cars) that stated rear disc brakes carry a weight and cost penalty. The author felt that in many cases rear discs are overkill for today’s front drivers.
Having driven otherwise identically equipped Ford Tauruses back to back, there is no doubt in my mind that a properly engineered rear disc setup is superior.
In my mind it kind of boils down to: A) Is this project within my capabilities? Am I sure that I am going to make the car better and not worse? (Being able to share ideas with other club members on this forum is certainly a terrific advantage!) B) Does the improvement justify the cost – with the cost obviously being effected by how much of the work I can do myself vs having to pay someone else to do it. (Also most of us take pride in doing it ourselves when possible).
-
- You must be logged in to reply to this topic.