AP caliper pistons

[nulrich]

I notice the AP LD20 calipers come with aluminum pistons, I assume because that's the standard configuration now (amusing considering the weight of the caliper itself). Are they legal to run that way, or do you have to replace them with steel pistons? The SCCA rules doesn't seem to allow anything but "ferrous" materials in the brake caliper and disk.

Nathan

[kea]

As far as I know, steel pistons are still required and are available for the CP 2505 brake caliper.
Keith
Averill Racing Stuff, Inc.
www.racing-stuff.com

[R. Pare]

The ferrous rule pertains to the body material, not the pistons, even though it isn't stated as such.

[Purple Frog]

I heard at the PRI show that AP is not making the steel LD20 anymore.

I need to follow up on that rumor.

I got to say, after walking the show floor, it seems silly to be still insisting on steel calipers... So many less expensive and lighter alternatives... and did i say prettier?

[kea]

"I heard at the PRI show that AP is not making the steel LD20 anymore."
Before we go down the alloy caliper road, maybe we should make sure this is really true. Of course, the other reason this could be true, is that no one is buying them new anyway! In which case, there is no need to change the rule, the used market must be supporting the obvious, minimal replacement market.
Keith

[Larry]

I tried to get alloy calipers approved for FF, but got shot down and then trampled on! There are PLENTY of good alloy calipers available at prices less than either the LD-19 or LD-20.

...it seems like anytime you try to make FF either more modern or more affordable, you are viewed as a heretic who is intent on causing the next world catastrophe. Oh, well...

Larry Oliver
International Racing Products

[RussMcB]

Playing devil's advocate:

All of the current FF & FC competitors have perfectly good (non-sexy) calipers. A new rule allows lightweight calipers. What does that do to every competitor? Either they spend money to get the better/faster parts, or they choose to continue spending money on the things they would have anyway (rather than the new calipers), and they become a little bit less competitive.

[Bob Wright]

Uh...I asked an AP rep at PRI directly whether they are making Ferris LD19 and LD20 calipers....the answer is NO and they don't even have the molds anymore. They were very quick to say they have aluminum bolt on duplicates.

This may not be a big thing for those who already have cars, but what about mfg's (Piper, VD, Carbir, and others) who have to put a used caliper on a new car? That is an issue.

[dc]

Playing devil's advocate:

All of the current FF & FC competitors have perfectly good (non-sexy) calipers. A new rule allows lightweight calipers. What does that do to every competitor? Either they spend money to get the better/faster parts, or they choose to continue spending money on the things they would have anyway (rather than the new calipers), and they become a little bit less competitive.

True Russ, but anyone who goes out to buy aluminum calipers to be a few pounds lighter is already spending LOTS on their cars in other areas to reduce weight (and disposable income). They don't necessarily care about the costs. You could say the same thing about drilled rotors, gun-drilled axles or any other whizzy parts. At least these would be something to replace an item no longer in production.

[R. Pare]

....... but what about mfg's (Piper, VD, Carbir, and others) who have to put a used caliper on a new car? That is an issue.

Carbir and Piper already use our versions of those calipers (the -20 size specifically), so availibility new is really not an issue. If the rules change, we'll just start producing a billit alu version as well.

[Camadella]

I think that requiring relatively sophisticated, purpose-built race cars to have iron calipers is like NASCAR requiring cars to have carburetors.

There is no good reason not to allow alloy calipers, in my opinion.

Cheers,

Chris C.

[nulrich]

The ferrous rule pertains to the body material, not the pistons, even though it isn't stated as such.

Hello. Thanks for the info. Can you point me to a reference allowing aluminum pistons? Not much of an advantage, I know, but I think I would prefer the LD20 boat anchors since they are so much stiffer than the alternative.

I do understand the theory behind not allowing aluminum calipers...but all the "ferrous" rule does is increase the cost of a properly designed caliper.

Regards,

Nathan

[R. Pare]

Never been a ruling as such. However, the generally understood ferrous reference (at least at the time the rule was written) was to the body material, not to the other components that made up the full assembly - otherwise, the seals would also have to be ferrous!

[RussMcB]

If, and only if, someone approached the CRB and said "I cannot get legal calipers for my FF/FC race car", and provided proof, then I would understand why the rule change should be considered.

And I think a rule change would need to somehow avoid disenfranchising the FF/FC competitors that are currently using heavy calipers (all of them) and do not want (or can't easily afford) to upgrade.

Otherwise, it's unnecessary rules creep. Every SCCA race car class has restrictions. Why is this restriction different?

[Wahawk]

Does anyone recommend the ICP caliper for FC?

Dave

[Rick Iverson]

Disregard.

On duty for twenty something hours and made a vicious and uncalled for comment. She was a beauty, but way out of line. Sorry!

[DaveW]

Does anyone recommend the ICP caliper for FC?

Dave

I do:

http://www.apexspeed.com/forums/show...ht=icp+caliper

[Steve Demeter]

Have not had to touch mine for 4 years.

[racer27]

Have not had to touch mine for 4 years.

Ditto - rebuilt then when I got them 3 years ago, not been touched since. Gonna rebuild them this season as preventive maintiance.

[R. Pare]

A quick estimate off the top of my pointy head is that we've sold over 1500 of them over the last 18 years to FF, CFF, FC, and S2 - far more than I ever though we would. As with any product, there have been some complaints, but over all, extremely few. If the rules change, our porduct offering will change along with it.

[DaveW]

Never been a ruling as such. However, the generally understood ferrous reference (at least at the time the rule was written) was to the body material, not to the other components that made up the full assembly - otherwise, the seals would also have to be ferrous!

Along with the crush washers used for banjo bolts... Joke - these are not actually part of the caliper.

[R. Pare]

But Dave - just think how long the seals would last!

[sidney]

Carbir and Piper already use our versions of those calipers (the -20 size specifically), so availibility new is really not an issue. If the rules change, we'll just start producing a billit alu version as well.

Is the only reason you would produce an Al version wieght or something else? Would you attempt to produce a 4 piston unit versus 2? I'm just wondering what the real advantages and disadvantages are between an ICP iron unit and a comparable Al unit.

[R. Pare]

At this time, the primary reason for producing ferrous calipers is that the rules require ferrous.

Secondary to that is cost - ductile cast iron castings are cheap compared to alu, and it retains its strength better when hot - aluminium doesn't do that very well, though some alloys are better than others.

When designing in cast iron, it is a LOT easier to maintain the stiffness so that the caliper feels the same as the original AP units - which is what guys are going to compare them to - yet be a lot lighter - it all depends on where you put the material. The reason behind the modular design of our caliper is that it makes it very versitile - changing the layout for different rotor widths and mounting layouts is very easy and allows us to replace other, older, calipers designs like the Girlings and ATEs on old FFs.

If you were to do an aluminium LD20 version, you can get the same stiffness, but it has to be much bulkier - even if you copied the layout of the AP unit exactly, it would still be less than 1/2 as stiff, and you would feel the difference. Cast iron is also a lot harder to abuse and break over the years.

Alu has the advantage that machining it is a lot easier, so you can make it out of billit in small quantities without gaining all that much in cost.

Personally, if I were to try to make the "ultimate" caliper, I'd weld it up out of 4130 sheet, like the construction of steel sheet uprights. The stiffness to weight ratio of steel is better than that of alu, so if done correctly, you could dramatically decrease the weight even when compared to our cast iron unit, but I doubt that there would be many guys willing to shell out the $$$!

For FF, FC, and FB, the LD20 pad is more than adequate size-wise, with the exception being on the front of an FB once the performance reaches its potential, so for the most part I'd stick with making 2-piston calipers, and wait to see how the demand shakes out for good quality 4-piston calipers for FB.