I did the same repair after on my Clubbie Estate after a 2 month old new mount was failing using a bolt and a nylock nut so it was installed but not super tight and the rubber could still flex as needed, no trouble since either.

I had to repair the center mount because I couldn't find the heavy duty version at the time. It failed and I glued it back together with some anerobic black RTV and drilled a tight hole for the center bolt. I think I even used the RTV on the bolt when I installed it. Over a year later and it's still working with the 2 inch Maniflow.

Much wiser words!

Great input, thanks guys -

" I think part of the trick is to ensure that when you install the system, the hangers need to be in a relaxed state - no axial pull or torsional load on the rubber. "

Wise words.

Make the rubber hangers last even longer by rotating them 180 degrees when they start to appear too saggy.

And cross speed bumps at an angle. One wheel at a time.

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Acoustics and sound transmission: everything transmits vibrations (vacuum being the absense of 'everything') to some degree. Everything also absorbs vibration to some degree. Softer things absorb vibration better than stiffer/harder/denser things. Solid exhaust mounts obviously transmit the most vibration to the car body. Increasing the preload on the resilient part of the hanger would increase the amount of vibration transmitted. The second part of the problem is that materials absorb better at certain frequencies but may be very poor at other frequencies. So, to opimize resistance to transmission, one should assemble a selection of materials that cover the range of frquencies to be absorbed (but I digress....).

As noted elsewhere in this thread, the exhaust support system is pimarily intended to provide flexible support so that the system can move about to a certain degree to absorb engine movement, thermal expansion/contaction, etc. The support system also needs to maintain that suport under normal loads - the static and dynamic forces at play on the exhaust system as one drives down the road. It is not intended to withstand impact on speed bumps etc.

The stock rubber/steel composite supports should be adequate to support the mass of a typical Mini exhaust system. I think part of the trick is to ensure that when you install the system, the hangers need to be in a relaxed state - no axial pull or torsional load on the rubber. The angle of suspension should be close to vertical, but isn't critical. 

My central hanger is the stock square block one that came on the car. (I'm not sure why in this pic it seems to have a twist on the rubber! It has recently been removed and reinstalled, so should be correct now.) This is the 3rd exhaust system I've had on it, and I wouldn't be surprised if it is original to the car. The flat steel strap is connected to one leg of a U-bolt type clamp.

My rear hanger is one of the smaller round type, also that came with the car. I fabricated the strap from 1/8" x 1" stainless steel, with one clamp bolt and a slotted hole at the top.

To install the exhaust system (working alone.. no kids to help), I supported the assembled long pipe and muffler with blocks of wood under the muffler at the correct height until I could work the front end onto the header outlet. Then with the middle clamp and the rear strap slack, I positioned them so the system would hang from the bobbins without the nuts installed. Then I tightened clamps beginning at the front and did the bobbin muts up last. Each hanger strap is in a 'relaxed' position, and the bobbins are only resisting vertical shear forces.

Note the muffler has the hanger bars for the later style rubber pretzel hangers. My subframe being original isn't in prime condiion, so I wasn't about to try adding the corresponding muffler hanger brackets to it. I have my doubts about the petzel style hangers anyway.

T'was Kevin's idea -

Oh, that's really cool - you're using a rubber mount to reduce noisy buzz of the facet.  That is some great thinking.

I've never had the bobbins fail, but then, things don't usually sit on the car long enough to fatigue...  That said, however, I did notice that the standard bobbins that I have used in the past do have some stress cracks and I'm not sure that I'd trust them long term.

Yes, the C-19G3258 is as beefy as it looks - pretty much a lump of black plasticy stuff.  I'm really not sure what it is, polyurethane or what, but it's pretty hard.  I'm using one as the RC40's rear mount. 

I'm using the C-19G3257 in the middle and as the (sideways) mount for my fuel pump on the rear subframe web.  I really like these, as you can regulate the rubber's pre-load via the nut, so it serves really well as a fuelpump mount, and as the bolt that the clamp and bracket attaches to passes through the rubber block and metal 'cage', it really can't fail as an exhaust mount.

This image is DRMINI's, but it's the same as what I've done.  Fits the pump perfectly, and with only one hole through the subby. 

I was just kinda wondering, though, why one would use a relatively soft mount in the middle and hard-mount the rear?  Or, as the factory did, soft and soft?

Sounds like someone (Todd) needs to start another thread "Let's see your longest lasting rear exhaust hanger" thread. Funny, I was just looking at mine last night and thinking that it looked like a future roadside emergency necessitating baling wire purchase.

I've finally given up and hard-mounted it with an aluminum bracket.  A few months ago the bobbins gave up and I had use my belt creatively along with the boot lid.  Had to close the boot lid on the belt after wrapping the latter around the pipes to get home.

Exhaust mounting has been something I've redone so many times I would write a book if I ever figure out a solution that lasts with time and speed bumps.

Liking that C-19G3258 if it's as beefy as it looks.  The problem I've encountered with the rubber ones is that they must be aligned exactly right without any directional or shear load.  Which we know is hard to achieve when the pipes are going this way and you need them to jog a little that way.

I should be hanging the new Maniflow center exit large-box twin-box system on Friday. 

So, as I've got several options at hand, I'm curious to hear which rear-most exhaust mount you'd all recommend. 

I have available:

2 x GEX7251 Standard 'bobbins'

1 x C-19G3258 Competition-type rear mounting

1 x C-19G3257 Heavy-duty center mount w/ through-bolt

Maniflow offers standard bobbins as well as heavy-duty bobbins (which I'd forgotten to order at the time I'd ordered the system, but have since ordered them (and a sticker for the toolbox) and should have them next week...), so I'll have to make due with what I have. 

The reason I've included the heavy-duty center mount (rubber block w/ through bolt), is that as you tighten the nut on the through bolt, the rubber block compresses and the mounting gets 'stiffer' due to pre-load.  My suspicion is that this could function in a similar fashion to the bobbin-type mounts, in that it would also dampen vibration to some degree. 

What do you think?