Need advice for drilling holes into front control arm/knuckle.

[jizzle85]

I need some advice on the front control arms of my S5. I know Alot of you will tell me to not do it and how unsafe it is yada yada yada. So, with that said I need some advice from the views of individuals with engineering backgrounds or maybe R&D. Here's a little bit of info on my project I'm working on. I'm fitting brake rotors from an R8(365MM diameter) and calipers from the 2015 Cadillac Cts-v. I went into the project thinking I had to machine some brackets to adapt the caliper. But turns out, the calipers fit relatively well already. With some minor trimming with a grinding wheel and drilling 2 holes, these will fit just fine. Good thing the front knuckles were designed and built extremely strong and beefy from the factory. The location that I will have to drill holes is pretty thick and there is allot of material to support it. The newly drilled holes will interfere with the factory holes. They'll actually oblong them a little. My question is, in my picture you can see the blue dots. That's where I'll be drilling. The factory holes measure .570 in diameter, and I'll turn a plug either out of steel or aluminum to press into the factory holes and they'll go flush front and back,from there I'll drill my new holes. That way the hole is greater reinforced and I can drill straight instead of the drill bit "walking" on me. I'm a machinist/cnc programmer by trade and I think this is a good approach to what I need to accomplish. I never would attempt this normally, but after Iv had my hands on this knuckle, I'm confident in the drilling idea only because there is so much material all around the holes. This brake setup is literally almost there. They clear the factory 19 inch wheels so that's good news as well. Here's some pics to get you an idea. The caliper is being held on with one bolt at this point for mock up reasons, so if you can imagine in your head that I need to let the caliper slide downwards a little and then the bolt spacing from knuckle to caliper is very close. So I think with my project I'm opening up the options for us B8 platform guys that don't want to spend big$$$$ on a BBK or even going with the big$ RS5/SQ5 brakes. Know we can have something that really stands out :-) thoughts.

Edit.... I'm having trouble attaching pictures. When I get it figured out, I'll reply with them.

[jizzle85]

http://www.a5oc.com/forums/#/forumsi.../113033?page=1

For the time being,I guess I don't have permission to post attachments. Use this link to my other thread to view the pictures. If attaching links to other forms is against the rules, my apologies. I didn't see that in the rules here.

[Rocket Tech]

Not exactly sure what you're doing but based on the description sounds like you're going to plug the existing drilled hole using a plug, machine the surface flush, then come back and drill a new hole slightly offset. The plug you install won't really have much strength since you'll be removing about half of it and what remains will basically be a curl of material sandwiched between two helix forms. For something like this I would plug it as you suggest, weld it into place, then re drill and tap. I would do this for hardware I didn't care about losing, but not sure I would do this for something my life depends upon. Interesting project, good luck! Are you doing this for aesthetic reasons or for better braking?

[jizzle85]

I'm doing it for appearance reasons mostly and braking. I want something unique as well. The factory brakes are surprisingly very good for my daily driving habits and I can't really comment or give my opinion as to brake fade etc. I don't experience it for my driving style. Maybe if I tracked my car I would. I wouldn't mind doing an autox course one day tho. Anyway, back on topic. The plug I install would be loctite'd in place and when I drill the new holes,I would prolly end up drilling about 1/3 of the plug material away. If you feel the little mounting ears on the knuckle itself, it's pretty thick. I really don't feel I'll be sacrificing structural integrity with the newly drilled holes. One idea I had to help and increase strength to the mounting tabs I drill, is machine a bracket that will run on the backside of the drilled holes and it'll join them essentially. If I can get a moderator to allow me permission to post pics I can show you better what I mean. I don't wanna weld on the aluminum at all bc I think the control arm is heat treated and aged. I don't wanna aneal the material to a soft state because then I would be worried more about structural integrity. The plugs I press in place with serve 2 purposes. A little strength, and it'll keep the caliper from being able to move within the oblonged holes at worst case scenario if the mounting bolts came lose. But I'll safety wire the bolts as well. Did you see the pics in the A5 forum link I posted?

[Rocket Tech]

No, the a5oc link just takes me to the front page. I can't stand loading that site on my phone.

Seems to be a tremendous effort for aesthetic reasons. I haven't looked into bbk options for this platform but I believe there's an rs5 kit in the classifieds for a very reasonable price and it wouldn't compromise the integrity of your braking performance/durability. Given the cost for the caddy calipers and the personal time ivvrsment you're making in the end you're likely to have come out ahead going that route. There's something to be said for having projects that are unique and investing sweat equity into something - but I'm not sure this is the place to be doing it.

I haven't crawled under my car to see what the calipers and mounting points look like so I honestly have no idea what kind of margins were designed for these braking systems. Since it's an oem passenger vehicle application my guess is structurally these areas are well over designed for normal braking use, all bets are off for off nominal situations such as in a crash. But at that point you probably wouldn't care anyway.

[jizzle85]

http://www.dsmtuners.com/threads/eng...t-idea.501495/

This link should work. I hear ya about it being over developed/engineered. I thought the exact same thing once I got the calipers and rotors off. There mounting ears do not stick out very far and all the material in that area is extremely thick. I think if you were to see it in person for yourself, you might agree with how much material there is and exactly how much the new holes will be opened up. And about the investment, when it's all said and done I'll be about $1k into the project.

[JamesRS5]

No, it's not a good idea. Your plugs will have no strength so it will be the same as having an elongated hole.

Your best bet would be to at least try and pick up one of the original mounting holes, weld the other hole and re-drill the new hole location.

Personally I would fit a mounting bracket to the original calliper mounting holes and rotate the calliper to a position where it will fit.

[jizzle85]

There is absolutely no way to mount a bracket to the original holes and clock the caliper to fit. If I want to use a bracket to push the caliper out a little and mount everything using the original holes,I would need a bigger rotor.

[JamesRS5]

If you pick up the original lower mounting hole on the caliper and run the bolt through there, can you mark where the upper bolt will sit. If you have around 1.5D (bolt diameter) space between the old hole and the new one then you might be ok for hole clearance but then how will you have a mounting face running true for the caliper to bolt up to?

I have a full set of 8 piston RS5 brakes going spare, they are practically brand new and would look just as good painted yellow. It would be a bolt on conversion.

[jizzle85]

I'll check and Mark that location. I think if I did use any of the original holes to mount, it would have to be the lower hole for sure. How much are you looking to get for the calipers? I originally wanted to buy done RS5 calipers, but everyone wants way too much for them.

[JamesRS5]

I was going to sell the whole lot, front and rear rotors and calipers for $1000 (rear calipers have the EPB) They are the later design wave pattern rotors.

I left them at the workshop where we fitted my CCBs as the guy wanted to see if they would fit on his B6 RS4 project. I can ask if he doesn't want them if you're interested.
Have a look at my CCB thread, I think there's pictures of the old brakes on it.

[Drew0u812]

Is this caliper even a good match for the Audi's Master cylinder?

[jizzle85]

If the RS5 8 piston calipers work well, then I think these 6 piston calipers will work fine.

[Rocket Tech]

If the RS5 8 piston calipers work well, then I think these 6 piston calipers will work fine.

Are you basing that on piston area? Piston count isn't a good reference point for equivalency.

[jizzle85]

I'm basing it off part numbers. I originally was going to use the SQ5 brake calipers and they have more clamping force then the S5. And both vehicles share the same part number for master cylinders.

[JamesRS5]

Rocket Tech has a very valid point; you need to measure the size of the Pistons and make sure they are similar. The RS5 uses a brake booster which you may also need to install, you don't want the pedal hitting the carpet before the car starts slowing.

[jizzle85]

I have already done my research on this. Im well aware of what is needed for a caliper upgrade. This isn't my first rodeo. I'm not some kid that's blindly throwing parts at a car and wishing it the best of luck. There's plenty of other threads on other forums documenting similar projects like mine. The only thing I would suspect, is if a PROFESSIONAL driver took my car on a aggressive drive, he would notice something that might be off. In that instance, were talking a fine margin of braking that might be off. Nothing drastic. But an average Joe like me won't have any issues with braking going to work or the gas station. It'll be an upgrade for guys like me. Not everyone can go out and buy ceramic brakes lol.

[Rocket Tech]

You're asking for advice and I think you've gotten what you wanted (or didn't). Seems you're going to do what you want anyway. I've certainly done something similar for one of a kind hardware that I HAD to use - but that was always with the acceptance that the likely outcome would end in lots of fire.

I think the opposite is true - a professional driver on a closed course is going to operate the brakes smoothly and in a controlled manner. On the street, situations are much less predictable and emergency braking/high impulse loads are much more likely. It's this kind of loading that drives high dynamic stress that is more likely to lead to failure of the "repair" methodology you're planning to follow.

It's an interesting project but the cost/benefit/risk trade doesn't work out for me. Definitely wish you the best of luck!

[JamesRS5]

I have already done my research on this. Im well aware of what is needed for a caliper upgrade. This isn't my first rodeo. I'm not some kid that's blindly throwing parts at a car and wishing it the best of luck. There's plenty of other threads on other forums documenting similar projects like mine. The only thing I would suspect, is if a PROFESSIONAL driver took my car on a aggressive drive, he would notice something that might be off. In that instance, were talking a fine margin of braking that might be off. Nothing drastic. But an average Joe like me won't have any issues with braking going to work or the gas station. It'll be an upgrade for guys like me. Not everyone can go out and buy ceramic brakes lol.

Ok fine, only tried to help..
Good luck with your conversion.

[jizzle85]

I was referring to the master cylinder. I hope I didn't come off jerkish. Totally didn't mean to sound that way. My apologies if I did.

[Agilis]

Jizzle some advice: You sound like a nice, knowledgeable guy but you cannot ask for advice then get upset at the advice that you receive. There's a lot of knowledgeable members here who all have technical experience which carries a unique set of opinions that you may not agree with. Patience and understanding that others are just trying to help goes a long way here. Good luck with your conversion!

[auditink]

jizzle85,

This just doesn't seem like the best idea..... But it seems you have your mind set on doing it this way. I think maybe you were not looking for advice but maybe some reassurance that this method of drilling through the knuckle would work.... will it work, who knows... maybe.... BUT is it the right way to do it, NO. would I do it this way... HELL NO. Do it right the first time and don't try and try and engineer around what should be done in the first place. you are a machinist so why not machine a bracket to use all existing holes as they were intended. if you don't feel confident on making a bracket for yourself, there are others that can make this happen for you so you and everyone that drives around you can be safe. The control arms and knuckles are not as strong as you may think and you want to drill a hole where it was not engineered for the hole to be. even with that part of the knuckle having more material there, that material is there for a reason, and not to be drilled through for a set of calipers to fit. How often do people have bent control arms because they hit a pot hole and the control arms are pretty beefy. It just seems you are going about it the wrong way here. jizzle85, make a bracket and be done with it. I have a BMW M3 that I converted the stock sliding calipers to brembo calipers from a porsche 911. Did it fit or line up stock for stock....no , of course not, but with a bracket it fits perfect and was a simple install. A bracket is the right way to do this my friend.

also not sure if you did the math to calculate for brake bias but you might want to do that. Do you know what the stock brake bias is?

[jizzle85]

Jizzle some advice: You sound like a nice, knowledgeable guy but you cannot ask for advice then get upset at the advice that you receive. There's a lot of knowledgeable members here who all have technical experience which carries a unique set of opinions that you may not agree with. Patience and understanding that others are just trying to help goes a long way here. Good luck with your conversion!

I want to reassure everyone,im not getting upset with the advice given. More like addressing questions and concerns with the wrong tone of voice, but with typed letters lol. But I promise, it's purely taken out of context if that's how my responses are taken. I mean the best and have the best intentions. This isn't a project I'm trying to "cobble" together and ignore all safety concerns. This is still very much an idea of mine that I would like to utilize. I really like the style if this caliper, and soo many other platforms of cars had adapted this caliper with great results. All using brackets, welded together brackets, drilled holes and God knows what else? From what I researched and from people I know, they hadn't reported failures. I would very much like this to work so I'm trying to find the best solution. My ideas from the beginning are just that, ideas.. I drive my car everyday if the week. 20k miles a year and I have a family. So this needs to be a safe end result of a project.

jizzle85,

This just doesn't seem like the best idea..... But it seems you have your mind set on doing it this way. I think maybe you were not looking for advice but maybe some reassurance that this method of drilling through the knuckle would work.... will it work, who knows... maybe.... BUT is it the right way to do it, NO. would I do it this way... HELL NO. Do it right the first time and don't try and try and engineer around what should be done in the first place. you are a machinist so why not machine a bracket to use all existing holes as they were intended. if you don't feel confident on making a bracket for yourself, there are others that can make this happen for you so you and everyone that drives around you can be safe. The control arms and knuckles are not as strong as you may think and you want to drill a hole where it was not engineered for the hole to be. even with that part of the knuckle having more material there, that material is there for a reason, and not to be drilled through for a set of calipers to fit. How often do people have bent control arms because they hit a pot hole and the control arms are pretty beefy. It just seems you are going about it the wrong way here. jizzle85, make a bracket and be done with it. I have a BMW M3 that I converted the stock sliding calipers to brembo calipers from a porsche 911. Did it fit or line up stock for stock....no , of course not, but with a bracket it fits perfect and was a simple install. A bracket is the right way to do this my friend.

also not sure if you did the math to calculate for brake bias but you might want to do that. Do you know what the stock brake bias is?

I would most definitely like to use a bracket, and I'm very much on board with using a bracket. Like I started previously, this is an idea that I came up with and it's just that. An idea. Sure there are better ideas and that's why I'm here. Most things are better planned with cumulative thinking. I definitely wanna stay away from welding the knuckle, and drilling holes. Im working an an idea right now to make a bracket that will mount to the 4 bolts that hold the wheel bearing in the knuckle and that bracket will extend out to the caliper mounting pads on the knuckle. It's hard to get my hands on the car because I work full time and have a 16 month little girl that keeps me plenty busy. So for the time being I'm relying on pictures I have taken and the help of googled pictures to brainstorm ideas. This caliper is physically so big and the S5 knuckle does not have a lot of room to clock the caliper to fit best. I can literally only mount it within the mounting ears on the knuckle so is a tight place to fit something so big. If I could post pictures here, I can easily show you guys what I'm working with. I just don't have the permission from the mods to post pics yet I guess. And I'm not worried one bit or concerned with brake bias. This isn't a drag car,auto cross car or even a canyon racing car. I'm purely doing this for appearance factors. That and I'm bored and need something to do for my own personal tinkering pleasure. My bias might get thrown off a bit, but nothing that I would notice. I am ordering some Hawk HP pads and ECS 2 piece rear rotors on Friday, so whatever bias I might lose, can be made up for with the upgraded parts for the rear.

[jizzle85]

I was going to sell the whole lot, front and rear rotors and calipers for $1000 (rear calipers have the EPB) They are the later design wave pattern rotors.

I left them at the workshop where we fitted my CCBs as the guy wanted to see if they would fit on his B6 RS4 project. I can ask if he doesn't want them if you're interested.
Have a look at my CCB thread, I think there's pictures of the old brakes on it.

I sent you a pm but I'm not sure if it worked? It didn't show a sent message. Anyway I'm interested in the front calipers if your willing to come off them.

[jizzle85]

I do wanna add, and in all fairness that if I posted that I was putting RS5 or any other Audi product on my Audi car, no one would go against it and tell me it can't be done blah blah blah. But the minute anyone does something different and it's not an Audi product, everyone here loses their mind and gives resistance. That's one thing Iv noticed on these Audi forums. In particular it's from people with very expensive cars. This is just a ramble for arguments sake. And you can't tell me any different bc I have been reading all types of forums for 15+ years bc I have always been tinkering with car projects since I was a kid. But it's within the last 5 years Iv been into Audi vehicles and this very topic is what I have noticed about Audi owners. They are very resistant to change and creativity to trying something different that was never intended to be produced within factory spec of an Audi vehicle!

[Agilis]

I do wanna add, and in all fairness that if I posted that I was putting RS5 or any other Audi product on my Audi car, no one would go against it and tell me it can't be done blah blah blah. But the minute anyone does something different and it's not an Audi product, everyone here loses their mind and gives resistance. That's one thing Iv noticed on these Audi forums. In particular it's from people with very expensive cars. This is just a ramble for arguments sake. And you can't tell me any different bc I have been reading all types of forums for 15+ years bc I have always been tinkering with car projects since I was a kid. But it's within the last 5 years Iv been into Audi vehicles and this very topic is what I have noticed about Audi owners. They are very resistant to change and creativity to trying something different that was never intended to be produced within factory spec of an Audi vehicle!

Jizzle, I appreciate what you said. However... If you look at the trend that you describe, both here and on other forums, I think it is several factors that you must consider. For one thing, those with expensive cars are more inclined to not tinker or meddle around with certain features of the vehicle because if something goes wrong, it costs a lot to fix. Second, several owners come here asking for advice, ignore the advice, and end up making an expensive mistake only to come back asking for more advice on how to fix the mistake. This wears on people and causes a lack of trust in judgement. Third, when it comes to safety, that's when you really see opinions fly because like it or not, that is the reason why within the last 5 years you see people voicing their resistance. There has been a huge awareness in safety the last 5 years that no one wants to see a modification create a risk to someone's safety. For example, the first response to your advice request questioned safety.

Look, there are several members here that appreciate creativity and change. It's not that you are bolting on calipers from a Cadillac CTS-V that has members here giving you resistance. It's because you are possibly creating a safety risk and unless you can cover all your bases, and satisfy everyone's doubts, you will always have some who question your approach.

[jizzle85]

I understand and agree with you. I mean if I had $70k RS5, I'd be pretty particular. I didn't think of it that way. Well for all that curious,I will be doing a bracket setup. I jacked my car up to see if there is room on the knuckle where the hub bolts to it and where the cv shaft runs thought. I think there is in fact room to fit 3/8-1/2 inch plate steel to mount a bracket. I'll be able to mock something up this weekend so I can report back then. I ordered a spare knuckle encase I mess this one up ahs I can just swap them out.

[auditink]

I understand and agree with you. I mean if I had $70k RS5, I'd be pretty particular. I didn't think of it that way. Well for all that curious,I will be doing a bracket setup. I jacked my car up to see if there is room on the knuckle where the hub bolts to it and where the cv shaft runs thought. I think there is in fact room to fit 3/8-1/2 inch plate steel to mount a bracket. I'll be able to mock something up this weekend so I can report back then. I ordered a spare knuckle encase I mess this one up ahs I can just swap them out.

good to hear, keep us posted on your project and would love to see pics of your progress and finished brake setup when it's complete.

[Agilis]

I understand and agree with you. I mean if I had $70k RS5, I'd be pretty particular. I didn't think of it that way. Well for all that curious,I will be doing a bracket setup. I jacked my car up to see if there is room on the knuckle where the hub bolts to it and where the cv shaft runs thought. I think there is in fact room to fit 3/8-1/2 inch plate steel to mount a bracket. I'll be able to mock something up this weekend so I can report back then. I ordered a spare knuckle encase I mess this one up ahs I can just swap them out.

Excellent decision Jizzle! Wish I had half the technical experience to even attempt something like that. Maybe not the same modification, but the technical experience that comes along with attempting such a modification. Good luck and hope it all works out for you!

good to hear, keep us posted on your project and would love to see pics of your progress and finished brake setup when it's complete.

Yes! Please do!