21 replies to this topic

[etrusco]

Anyone know where I could find blueprints of the front OE AP calipers found on the VX220/turbo? I'm trying to design/put together a complete brake system using performance aftermarket calipers, rotors. Would do the measurements myself, except that the car is put away for the winter and 500km away form where I live. Maybe someone has already measured up recorded these dimensions?

[etrusco]

Should I conclude that its close to impossible to get factory blueprints for the OEM front AP calipers, and no-one ever cared to meausre?

[Thorney]

I'm afraid the ownership of the caliper design remains with AP and with Lotus/Vauxhall. I've got copies of these and the AP kit we developed but would get my ass sued from here to eternity if they were released. Without wanting to overtly promote the AP kit we sell here what is it you want to achieve?

[etrusco]

Don't wan t to get anybody sued, so best keep blueprints in your safe with the crown jewels John. I'm an engineer at training and just call it a professional deformation, but I like to make my own version of things mechanical. I want to adapt several Wilwood brake parts, among these 4 pot, forged radial mounting calipers (similar to OEM APs) I have left from MX-5 turbo racer. I wanted to compare the blueprints in order to machine brackets and relevant mounting hardware.

[Jim_Cross]

Playing with brakes...I hope you've got a lot of confidence in your engineering abilities

[etrusco]

By the way Thanks as usual for being the first to tackle the hard questions that everyone else seems to be dodging in the forum

[Thorney]

Willwood? Hmmm. I've been fortunate enough to see some of the deflection tests of these and a few other manufacturers calipers in a test rig. The result was AP, Movit and Brembo calipers performed almost identically, Stoptech did well on lateral deflection but less well of longitudinal and Willwood failed miserably. One well known manufacturer in the Uk deflected roughly 300x more than a Brembo one of similar size. The technical information I saw was way above my understanding but what it did teach me was that whilst calipers may look alike the way they are made and type of material they are made of makes a huge diff.

[robfenn]

I presume the Wilwoods are billet not cast then John? The worst are supposed to be Hi Spec when it comes to strength. AP Racing run tests against Brembo and i have been assured AP Racing are always just in front. Funnily enough, despite Brembo owning both companies, they share no parts or development. -Rob

[etrusco]

Very interesting John. Do you know if this caliper deflection test is published somewhere on the Web so i can have a detailed look? Maybe it was my very model Wilwood caliper that failed miserably, in which case it's heading straight for recycling

[jules_s]

By the way Thanks as usual for being the first to tackle the hard questions that everyone else seems to be dodging in the forum

wtf?

perhaps we arent anywhere near qualified to answer the question, and also understand there would obviously be copyright issues posting that sort of stuff when you are going to rip it off.....

i dont think 'dodging the question' is the phrase you were meaning to use there

[etrusco]

OOOps, ticked someone off

[QUOTE]wtf?

perhaps we arent anywhere near qualified to answer the question, and also understand there would obviously be copyright issues posting that sort of stuff when you are going to rip it off.....

Didn't mean any offense by that, just thanking John for being always supportive/critical and prompt in giving his professional advice.

By the way, blueprints of caliper dimensions are all over the Wilwood site... and i asked where I could find some, NOT FOR ANYONE ON THIS FORUM TO POST THEM HERE!

Furthermore no-one is ripping anything off as I said I already had calipers and just needed blueprints for comparisons sake

[Thorney]

Very interesting John. Do you know if this caliper deflection test is published somewhere on the Web so i can have a detailed look? Maybe it was my very model Wilwood caliper that failed miserably, in which case it's heading straight for recycling

Not a chance.

Its probably not surprising to know that car tuning is no less thorough than any other business (from the decent people anyways) and the first thing any supplier/designer does when creating something is buy everyone elses and test them. The first thing I do with any ECU map is test them with those od other people to see how they compare, if need be I'll retro engineer someone elses stuff to improve my own - life really.

Common knowlefge in the trade is that HiSpec make the worst (but seem to mow out a lot of kits so can't be all bad) but I personally wont touch them with a barge pole due to the stories I've heard from trust worthy people and sight of tests on their stuff. Willwood's reputation isn't much better, in the US they are seen as the chav upgrade for show and no go (stop) and I've seen a set fail at Castle Combe with disastrous consequences in a 205 (straight into the wall at Quarry )

When I approached AP for the kit I helped develop they were quite open about how they did it and supplied me with a huge amount of technical data that I had to sign agreements not to disclose.

General view is that Brembo are the best, Movit (who use Brenbo bits and sort their own fixing kits) are good but expensive and AP the same as Brembo but are lighter - hence I pisked them for the VX kits. As it happens we've now pretty much adopted Ap for al the BMW stuff we do too - if it works then it works.

[Ducati996Senna]

John, having seen the purpose made VX 4 pot calipers from AP. They are very close to the inner wheel face. As the balance is maintained as per the standard arrangement, does this mean the braking efficency remains the same? Is it that the only difference is a 4 pot braking force through smaller pistons dissipating heat better. Maybe I'm missing something but, any increase in braking by changing to these 4 pot calipers would upset the brake balance.

[Thorney]

Paul, thats the point......as stock we DON'T have an equal bias set up. Regardless of the testing we've done look at the anecdotal evidence from people who complain of the rears locking up too quick, the rear pads wearing 50% faster than the fronts (even taking into account the thinner pad size) and boiled fluid even in road use. The AP kit was specifically torque balanced to equal up the balance between front and rear. The next change we're running is a slightly larger ali belled disk on the rear - you don't need a larger caliper and this will retain the balance. Remember the 'development' of our brakes was basically take the calipers off the S2 Elise, chuck em on the VX and slap a price tag on it. Almost no reference was made to the fact that (VXT's especially) are 150kg's heavier and 90% of that extra weight slapped firmly over the rear axle. As a result our stock brakes cook the rears, lock up the back tyres and boil fluid. The process of the AP kit involved a lot of measurements of disk sizes, caliper deflection tests, hose length etc etc then a long period of me ragging the car round MK's roundabouts and numerous trackdays with temp paint on all the equipment. This is certainly not a case of just putting a big set of calipers on the car. Also remember that the piston sizes are custom to the VX, they don't exist on any other caliper - these are fine tuned to the torque balance the car needs.

[Ducati996Senna]

Cheers, so infact it does have more front braking capability. I wasn't trying to suggest that they have been thrown on. I just wasn't aware of a brake imbalance on standard brakes. That said, I hadn't done any track days on standard brakes. But when you consider the weight variation between the 2 cars on the same system there must have been. Thought Vauxhall/Lotus may have addressed this in the tandem master cylinder (not knowing the internal bore sizes of the Lotus and vx master cylinders). I guess the fact that it has abs allows them to mask the problem.

[Speedstar]

@Thorney: "Common knowlefge in the trade is that HiSpec make the worst (but seem to mow out a lot of kits so can't be all bad) but I personally wont touch them with a barge pole due to the stories I've heard from trust worthy people and sight of tests on their stuff." Please tell me more about the stories and the people......I´m very interested.

[Thorney]

Well I'm not in the buisness of slagging anyone off, all I can say is my own dealings with them have been short and disappointing. There was a long thread on an Audi forum a few years back regarding a kit they made for an RS4 (might have been an S4) and it ended with the guy literally having to go down their and threaten violence to get his money back. I'm sure they do some nice stuff for in some nice applications but not for me.

[Speedstar]

In this forum however still nobody made bad experiences with HiSpec? Radical has HiSpec brakes and the brakestop is super. In the German magazine "SportAuto" the brakes were praised.

[Thorney]

Oh sure, but I can only go on my own experiences....they've all been bad, sorry.

[Speedstar]

Oh, I´ve seen that you are a professional dealer. You sell AP-Racing.

look and see...click!