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I’m looking at the WMW strut tower brace and the M7. They both look very similar, but why is the M7 a three piece bar in lieu of the WMW one piece bar connecting to the tower plates?
I went with the VIP because it seems like more thought went into the design of the plates. The notch on the bottom is curved instead of squared off and the bolt holes are full thickness using custom machined T-nuts instead of being recessed for the stock nuts. It would have been nice if the VIP was one piece, but it's three with small brackets at the ends of the bar. I guess this was their cost cutting measure to reduce wasted material. You can order the plates and bar separately over time, or save $19 by ordering them together.
There's another difference.
While the tower plates are similar enough to be basically the same, the cross brace is not.
The VIP "appears" to be a slightly better design. While the bar is a triangular shape (thicker in the center than it is at each end, it also..."appears"...to be a straight bar. The M7 is not a straight bar (not counting the two attachment points). It also has an odd cut in the bottom of it on one end. Why, I don't know, there is nothing near that cutout when mounted. The previous owner of my 05 installed an M7 bar. The bar is mostly useless in my opinion. The plates are nice.
ANY bar that has machined cutouts or has ANY bend in it is useless as a "brace". Why would one buy a bar that's already bent...when that's what its sole job in life...is to keep two things from collapsing onto each other..! Its "column strength" has been trashed before you even buy it..!
Another problem with the M7 bar (and possibly the VIP bar), is that the mounting holes are slotted. This yealds a purely "friction" joint. Friction joints are NOT strong in any way shape or form. I "sort of" understand the reason for the slotting of the mounting holes, but these cars are/were built to much tighter tolerances than the slots are long. Another bad design element.
1. The OEM, JCW bar is a straight bar. But it has light brackets. Won't help support the shock tower. No slots, good design. The bar length is adjustable.
2. The Racing Dynamics bar is a straight bar. I called and verified the carbon fiber thickness. It should be plenty thick for normal driving and a little help in "one" crash..!
3. There is another one that is very similar to the JCW bar, forgot the brand name. But it has light brackets. Won't help support the shock tower. A search of Mini suppliers will find it. No slots, good design. The bar length is adjustable.
For the best in bar strength...#1 and #3 above are the best two with #2 being third best.
What I did for my car, I used the Racing Dynamics bar and redrilled and tapped the M7 plates to accept it. I matched drilled the holes in the plates for the bar brackets. No friction fit slots.
I understand that what I did isn't a good way to go money wise (buying two kits !), that's why I recommend the OEM, JCW bar or the aftermarket kit that is similar in design.
There's a lot of good discussion out there on different bar designs. Here's my thoughts as a mechanical engineer.
1) The bend in the bar matters less than you'd intuitively think. I ran a little analysis on a rough model of the M7 bar, and it only compresses 13 thousandths under 1000lb compression load. Again, it's an approximate model and that 1000lb load is likely unrealistically high, but it illustrates the magnitude of the bending we're talking about. Is this enough to matter? I can't say for sure.
2) I wouldn't be concerned at all about elongated holes myself. Tension joints (relying only in the friction of the joint) are common in vehicles and tremendously strong when done right. In general, any joint that doesn't use a shoulder bolt is relying on friction to carry 100% of the load (you don't ever load on screw threads, and you don't use bolt shafts to carry any load where you care if it moves around under load). Using M7's installation torques I calculate a joint capacity of roughly 4000 lbs! You could hang the entire car from it and there's no way that sucker is slipping.
I would place the reputation of the vendor or shop as my highest priority. If they are doing things right, they will have simulated and designed the bar to withstand whatever you can throw at it.
Last edited by HaltCatchFire; 10-18-2018 at 01:48 PM.
I'm also a Mechanical Test Engineer (retired actually). Have been a Mechanical Engineer of various disciplines for over 35 years.
I've done countless (years worth) of "ACTUAL" (not computer based guesses), real world, column testing (compression and tension), both on custom designed test (one that I designed !) stands and store bought stands (Tinius Olsen and Instron Machines) .
First, a 1000lbs is nothing, (especially in a slow movement like a computer will provide). You need to test with a sudden "shock" parameter. Second, ANY bar that has been previously bent, e.g., structurally compromised...isn't worth a damn in the real world as any sort of real support mechanism.
I've tested, Carbon Fiber (tube and solid), Titanium (tube and solid), Aluminum (tube and solid), Magnesium (tube and solid) and even various materials of Honeycomb (inline with the ribbon direction).
So yea, I do have some background..!
BUT, it's your car, your money.
Me, I want real world support.
This is an interesting discussion. We use to sell the M7 bar, but when we told M7 about the things it needed to be improved upon they didn't care and were more concerned with the cost to make such changes and the profit that would be lost. That is why we started making our WMW bar as some have pointed out the issues with the M7 bar here and we wanted to make a proper, but cost effective bar.
1st thing we did was make it out of a proper billet aluminum. The M7 is made in china and we have found it to be more of a cast aluminum that is porous and have actually had the plates bend because of this. If you notice the regular M7 strut tower plates and the ones for the brace are made in two different materials. Their regular plates are actually stronger than the bar plates.
2nd make the bar one piece because with the bar being 3 parts like the M7 it will move at each joint and be less effective. This was a challenge as the reason the M7 bar is in multi parts is for shipping as it's much cheaper to ship short, especially when shipping from china. Also this eliminates needing another process of bending the material. They can just machine the shape the need for each end to get the curve needed to clear the airbox and cross the engine. Having the bars bent actually proved to be a challenge as the bends all had to be done in the correct spots and enough that it would hold the curve needed. This is how we have many bars with scratches in them as this process is not as simple as one would think.
3 make the plates use existing strut mount nuts. Producing each individual nut is costly and would increase the retail price even higher. Also unnecessary as we have used many plates for years with the stock hardware and know that it is a non issue or concern to do so.
4 make the bar attach directly to the plates. Again making a bracket to attach a bar to then attach that to the plates would have added another joint for movement, and make it less effective.
5 use studs in the end plates to attach the bar. Using bolts was not a good long term idea as you have to remove the bar to change the oil. We found that over time removing the bolts on the M7 bar in and out of the end plates would wear out the threads and eventually couldn't be put back in. Locking a threaded stud in ours made it so you only remove the nuts from the steel studs to remove the bar and simply go back on.
Now I know the concern over the bars being slotted has been brought up. Well this has to be done to make the bars fit all the cars. No two cars are exactly alike so there will be variation in the distance between the towers although it very slight. If you made a bar that was one solid length it simply wouldn't fit every car or would have to be forced on.
Our goal was to make the best bar we could at an affordable price. Sure it could be better but how many people would pay $300 or $400 for a strut bar. Not many and even at that price point the gain in a $300 bar to our $200 bar would you even notice? And if you could actually notice the difference between the two would you pay more for it?
This is an interesting discussion. We use to sell the M7 bar, but when we told M7 about the things it needed to be improved upon they didn't care and were more concerned with the cost to make such changes and the profit that would be lost. That is why we started making our WMW bar as some have pointed out the issues with the M7 bar here and we wanted to make a proper, but cost effective bar.
1st thing we did was make it out of a proper billet aluminum. The M7 is made in china and we have found it to be more of a cast aluminum that is porous and have actually had the plates bend because of this. If you notice the regular M7 strut tower plates and the ones for the brace are made in two different materials. Their regular plates are actually stronger than the bar plates.
2nd make the bar one piece because with the bar being 3 parts like the M7 it will move at each joint and be less effective. This was a challenge as the reason the M7 bar is in multi parts is for shipping as it's much cheaper to ship short, especially when shipping from china. Also this eliminates needing another process of bending the material. They can just machine the shape the need for each end to get the curve needed to clear the airbox and cross the engine. Having the bars bent actually proved to be a challenge as the bends all had to be done in the correct spots and enough that it would hold the curve needed. This is how we have many bars with scratches in them as this process is not as simple as one would think.
3 make the plates use existing strut mount nuts. Producing each individual nut is costly and would increase the retail price even higher. Also unnecessary as we have used many plates for years with the stock hardware and know that it is a non issue or concern to do so.
4 make the bar attach directly to the plates. Again making a bracket to attach a bar to then attach that to the plates would have added another joint for movement, and make it less effective.
5 use studs in the end plates to attach the bar. Using bolts was not a good long term idea as you have to remove the bar to change the oil. We found that over time removing the bolts on the M7 bar in and out of the end plates would wear out the threads and eventually couldn't be put back in. Locking a threaded stud in ours made it so you only remove the nuts from the steel studs to remove the bar and simply go back on.
Now I know the concern over the bars being slotted has been brought up. Well this has to be done to make the bars fit all the cars. No two cars are exactly alike so there will be variation in the distance between the towers although it very slight. If you made a bar that was one solid length it simply wouldn't fit every car or would have to be forced on.
Our goal was to make the best bar we could at an affordable price. Sure it could be better but how many people would pay $300 or $400 for a strut bar. Not many and even at that price point the gain in a $300 bar to our $200 bar would you even notice? And if you could actually notice the difference between the two would you pay more for it?
WayMotorWorks wrote - Now I know the concern over the bars being slotted has been brought up. Well this has to be done to make the bars fit all the cars. No two cars are exactly alike so there will be variation in the distance between the towers although it very slight. If you made a bar that was one solid length it simply wouldn't fit every car or would have to be forced on.
This is a mostly incorrect statement.
This comment would be correct if we were talking 60's or 70's cars. We are talking cars built after 2000..! These cars are built to a tolerance of about .015" in all critical areas. I know this for fact. My brother ran a BMW body shop for about ten years. He had to go to classes put on by BMW to tell their employees just how the cars were/are manufactured. BMW is VERY strict on how their cars are to be repaired. Their repairs are even to done to very high standards...to make sure everything fits and works as originally designed..!
Suspension parts, moving part (doors, hoods, decklids/hatches, glass, etc., etc.) fit.
So, yes, a slot (on ONE end) with about .020" might be required, but not .187"+ like these parts are built with.
Now, since the aftermarket has no idea how the cars will be treated after they are sold, some adjustment might be required. There are a couple of ways to make the strut bar kits actually useful..!
Make only one side slotted/adjustable NOT both sides of the bar, is a start.
The following is a couple of ideas for more properly designed strut bar kits -
1. Fit the bar kit to the car. Drill and "pin" the bar bracket to the tower support(s).
This would make the strut bar kit useful.
2. Make the slot a little longer, and manufacture shims to fill the slot, and are captured by the attachment fastener washer.
This would make the strut bar kit useful (though not as good as #1).
3. Make the strut bar adjustable...JUST like the rear control arm bars. Just like the OEM JCW bar is designed..! Very simple, easy to design and keep inexpensive. Accurate, will fit ALL cars, and actually works..!
Again, friction joints are useless, period. If you have a slot in a bracket, with a fastener going into that slot. No amount of normal fastener torque will keep that joint from moving under even a small jolt form a shock tower trying to move.
On the towers actually moving. DO THEY ?
I do not know how long the previous owner drove my car after installing the M7 bar kit. This kit is designed with outrageous sized slots, on each end of the bar. Pretty useless for any "actual" support..! One thing I noticed...there were NO witness (scratches) marks on the brackets from the fastener heads, indicating that the tower bracket was not moving under the bar bracket. Funny thing, the previous owner even had the tires (17" wheels) overfilled to 50lbs. each..! So a LOT of pounding was transferred to the body of the car from the road.
So, in reality, is IS pretty easy to design and build a "properly" designed strut bar support bar.
Something to ponder...when was the last time ANYONE saw a friction joint like this on a Daytona Prototype, an Indy Car, a NASCAR, a F1 car. ALL of these cars also have build tolerances, just like road cars. I can tell you, NEVER would a engineer/designer of these cars do this.
There's a lot of good discussion out there on different bar designs. Here's my thoughts as a mechanical engineer.
1) The bend in the bar matters less than you'd intuitively think. I ran a little analysis on a rough model of the M7 bar, and it only compresses 13 thousandths under 1000lb compression load. Again, it's an approximate model and that 1000lb load is likely unrealistically high, but it illustrates the magnitude of the bending we're talking about. Is this enough to matter? I can't say for sure.
2) I wouldn't be concerned at all about elongated holes myself. Tension joints (relying only in the friction of the joint) are common in vehicles and tremendously strong when done right. In general, any joint that doesn't use a shoulder bolt is relying on friction to carry 100% of the load (you don't ever load on screw threads, and you don't use bolt shafts to carry any load where you care if it moves around under load). Using M7's installation torques I calculate a joint capacity of roughly 4000 lbs! You could hang the entire car from it and there's no way that sucker is slipping.
I would place the reputation of the vendor or shop as my highest priority. If they are doing things right, they will have simulated and designed the bar to withstand whatever you can throw at it.
Good to see there is an ME amongst our local PIR Miniacs. Your short and concise post covered all the important points of the design of a tower brace and ABCs of mechanical fasteners. The bends in most of these bar is to accommodate the stock air box and ECU. From my recollection JCW has slight bend to it. In addition the attachment points to the the end plates are raised so it is still a triangle.
You just aren't getting it..! Computer "modeling is just that...Modeling..! A "pre-real world check". Initial check to "start with"..!
Sorry, the things I note are from "MY" (and others) personal experience as a (Professional) Mechanical Test Engineer. As previously noted, I've done this work as near daily life for over 35 years.
NOT only as computer models, but in "real world" , actual...testing.
There is a saying in the Aerospace Industry, "test as you fly". This means ACTUAL, real component testing. Both with Engineering Models and real flight components.
I've seen "friction" component tests fail well before the (computer based) "predicted" models proposed.
NONE of what my previous post has changed because of a given computer model..!. ALL of it is...again, real world, real component testing.
Sorry that you have a hard time absorbing this info.
You can computer model all you want, I'll stick to what I've seen, in real life testing, with work I complete on my cars and motorcycles.
People that work in real life components understand how things work in a much more realistic fashion than folks who sit behind a computer screen all day (without witnessing "real" testing), I know, I've been there and done that..!
Also...what the hell...you are bad mouthing the BMW engineers for THEIR strut design...!?
Again, your car, your money, you can do as you like.
Me, I'm sticking with real life testing knowledge. AND for that matter...a lot of common sense.
As a wise man once said, "can't argue with....".
PNW, why does your strut mount have alot more thread coming through than mine? are the studs on the IE fixed camber plates longer? I'm on stock strut mounts and I barely fill the whole nut with thread.
PNW, why does your strut mount have alot more thread coming through than mine? are the studs on the IE fixed camber plates longer? I'm on stock strut mounts and I barely fill the whole nut with thread.
Here are the answers for your multiple choice:
1) As OCR so expertly pointed out, the bolts holes are crap on the M7 bar which features slotted bolt holes or they are just plain sloppy. These resulted in the fasteners having to clamp the two pieces together and to rely on friction to prevent them from shifting relative to each other. I have to torqued the fasteners beyond yield so now they are a cm longer to compensate for the "crapy friction joint" .
2) The M7 bar's design is just fine - at least for someone like me that ignorance is bliss. I religiously torqued the fasteners to what M7 instructed like a blissful sheep being led to the slaughter house. I have no idea why my bolt threads sticks out more than yours. As OCR stated - you "can't argue with ...."
3) I disrespected BMW and think I know best . I ditched the perfectly good OE camber plate and installed, again poorly designed Ireland Engineering's fixed camber which has longer studs - hence the extra thread shown.
As OCR so eloquently stated any slotted holes are no good as they relies on "friction" to prevent the two joint pieces from shifting WRT one anther, here goes his theme that "can't argue with ...".
Here is the car trailer that I recently acquired. The trailer is not built with precisely machined bolt holes, nor are their any "pinned" joints. Worst, all the structure fasteners are T-bolts that are held in slots of the extruded aluminum. All are what he referred to as "friction" joints so are no good. To his expert judgement - it just ain't gonna fly as they say in aviation. Is this a case of crappy engineered product where disaster waiting to happen?
Well dang, I didn't mean to spark quite so much contention with my quickie simulation. Anyhow, thanks Way for the background on your bar. Some good info, particularly about transferring the thread wear to a steel stud instead of the aluminum plate. Makes sense.
Originally Posted by pnwR53S
From my recollection JCW has slight bend to it.
You know, I thought it was straight for a long time then I saw this picture, I think you're right! Looks like the whole bar sits at a slight angle and then curves down right after it clears the airbox.
That's good to know - I've been considering a bar for a little while but wasn't sure if I'd notice. I might make it my next CNC project if I find the time and a length of high-quality 6061...could be a fun experiment.
And sorry but I can't help but leave this image of the lone friction bolt and its slotted hole keeping the rear wheels attached to every Mini out there (rear trailing arms).
Last edited by HaltCatchFire; 10-21-2018 at 09:47 PM.
Weren’t those added on the facelift, and possibly the 2nd gens and later, when they switched to an eccentric bolt to allow a little bit of camber adjustment?
Weren’t those added on the facelift, and possibly the 2nd gens and later, when they switched to an eccentric bolt to allow a little bit of camber adjustment?
I know my 2006 has them, looking at the Pelican article on adjustable arms it says the slots were added after some nonspecific point. Without them, I think you adjust using slotted holes in the bushing mount point instead. I can see why these made things easier.
I received the WMW brace yesterday and dropped it off to be powder coated bronze like my wheels. It does have a big section of the brace cut out, :( , and I can flex it by hand with a little pressure. I wonder if it didn’t have the cut out there would be clearance with the DDMW air box (props to DDMW for sending me new logos for Powder coating)
Hopefully with both bolts bolted down there is less chance of flex. I wont be able to do a seat of pants comparison between stock and just the brace only because I’m changing pulleys, intake, and adding KW v2’s all at once.
I received the WMW brace yesterday and dropped it off to be powder coated bronze like my wheels. It does have a big section of the brace cut out, :( , and I can flex it by hand with a little pressure. I wonder if it didn’t have the cut out there would be clearance with the DDMW air box (props to DDMW for sending me new logos for Powder coating)
Hopefully with both bolts bolted down there is less chance of flex. I wont be able to do a seat of pants comparison between stock and just the brace only because I’m changing pulleys, intake, and adding KW v2’s all at once.
Most of modifications on my Mini were incrementally added, and it has been most interesting to experienced the improvements from each change. In the case of the M7 strut bar it was installed together with the cabriolet front braces. I have little doubt that the improvements are mainly attributable to the strut tower brace.
You can always defer bolting the cross bar till after you test out the other suspension and chassis mods. That would be what I would do.
I dont think it matters if the brace is flexible as its function is to stop the top of the strut towers moving apart during cornering. As the load goes onto the outer tire during cornering it pivots the strut about the control arms causing the top of the tower to move outwards.
The handling of any stock Gen1 MINI is superior in capability to the driving skills of most owners.
My car accelerates quicker along with both handling and braking better than any stock Gen1 and many Gen2s. It goes faster than I care to drive but yet I have a cross brace with slotted holes.
I also put baseball cards on my bike spokes and everybody knows it went allot faster. Slotted holes or not, my brace looks good on my "cute" car.
Read this thread. Seems to me that if BMW was as strict about how their cars are engineered and manufactured as they are about how they are repaired, we wouldnt have to repair them so often, need strut tower braces, fluid filled dampers, fuel pumps after only 60,000 miles, passenger side fuel sending units that allow me to run out of fuel when my gauge still reads 1/4 and many other items that each of you can probably relate from personal experience. The only positive thing I can say about my R52 is it’s fun to drive. Imagine how much more fun it would be without constant repairs to keep it on the road.
To ad to the conversation, I’ve often wondered if the inherent sway that I feel in a R57S would be helped with bracing but none of the manufacturers websites seem to have anything that would fit. Just a little improvement would go a long way as going topless is going to change anytime soon. Appreciate any input.
10-17-2018, 11:32 AM
has slipped. I was very skeptical with the M7 3-piece bar until I seen and felt an installed one first hand. To me it is a stronger bar than the JCW - which is gorgeous to look at.
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