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Dinan rsb comes with poly bushings. The BP brackets will be a bit harder to clamp down, use mole grips with tape on the ends to not mar the finish

I run poly fronts as well, I think those are the ones? I did the install about 8 years ago...
 

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The Dinan instructions say use the Stock bracket with their $0.01 metal tab. Ignore those instructions. Go with the BeastPower brackets or the steel ones. Use the Poly Powerflex or similar bushing available in the UK as you all have an entire cottage industry supporting FI and all forms of racing. Someone has to make those bushings over that side of the pond. Use can get away with the M5 sized ones without any issues on install. Just make sure you use a silicone based grease not oil/petroleum based.

The OE rubber bushing vs Poly
With the Poly you get instant resistance so the bar bends. With rubber, the bushing compresses then the bar bends. There is ZERO NVH from using the poly bushings. Trust me on this item as I am anal to extremes.
 

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You haven't broken one... yet...
They're Aluminum. They break.
The OE Aluminum ones break all the time. You have to pull them off and see the cracking/break at the insert tab or at the hold down bolt end. Everyone who has posted over the past 20+ years had an INSTANT failure after track day, but only noticed the clanking days/weeks later. This is one of the cheapest "fixes" you can do to resolve a known weak point. Oh, do not forget to replace the end links at the same time. I recommend either Lemforder or Meyle HD units. Again cheap insurance as you are already 50% there as you will have to remove the upper 16mm bolt. :)
 

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Your UK source SuperFlex advanced polyurethane suspension bushes

Dinan bar is 17 MM when measured, order bushings to match

For those who need to know specs, here is a post from 2008 on the stiffness of the Dinan bar vs OE M5 bar.
... the torsional stiffness of a round bar varies with the 4th power of the diameter as ECB has shown. 17^4 / 16.5^4 = 1.13, so the Dinan bar is 13% stiffer when set to equivalent moment arm as the stock bar. You can move it to two stiffer locations, but I don't have those moment arm measurements handy at the moment though. If you want something even stiffer, Eibach makes an 18mm rear bar for the E39 which is 41% stiffer. However, I've found the Dinan bar set in the middle position (along with my other mods) is just about the right balance of roll stiffness. If you go with the larger Eibach rear bar, I would go with their 28mm front bar also (stock is 27mm).
 

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Discussion Starter · #27 ·
The Dinan instructions say use the Stock bracket with their $0.01 metal tab. Ignore those instructions. Go with the BeastPower brackets or the steel ones. Use the Poly Powerflex or similar bushing available in the UK as you all have an entire cottage industry supporting FI and all forms of racing.
Yeah I noticed the Dinan instructions said not to lubricate the Dinan bushings, the whole instructions are suitably vague, perhaps they mean petroleum based lube and aren't talking about silicone grease etc.
 

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Discussion Starter · #28 ·
Your UK source SuperFlex advanced polyurethane suspension bushes
Dinan bar is 17 MM when measured, order bushings to match
For those who need to know specs, here is a post from 2008 on the stiffness of the Dinan bar vs OE M5 bar.
... the torsional stiffness of a round bar varies with the 4th power of the diameter as ECB has shown. 17^4 / 16.5^4 = 1.13, so the Dinan bar is 13% stiffer when set to equivalent moment arm as the stock bar. You can move it to two stiffer locations, but I don't have those moment arm measurements handy at the moment though. If you want something even stiffer, Eibach makes an 18mm rear bar for the E39 which is 41% stiffer. However, I've found the Dinan bar set in the middle position (along with my other mods) is just about the right balance of roll stiffness. If you go with the larger Eibach rear bar, I would go with their 28mm front bar also (stock is 27mm).
That rear bushing price is pretty good. Do you know if they are legit? The powerflex ones are twice the price, maybe it's the brand name and colour. This PF one is described by some as 17mm and by others as 16.5mm, I would have to check that with them. Maybe some are rounding it up.

Eibach was my first choice for a while but it might have been a risk with the overall stiffness and I found out it was discontinued anyway so a non-starter (I only found one for sales in Singapore at nearly 3x list price LOL excluding shipping and tax. However I didn't know so much about the Dinan at that stage (thanks everyone for the pointers).
 

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Discussion Starter · #30 · (Edited)
i don't suppose it matters if I mix brands of poly bushings on the ARB to get the right sizes for the Dinan rear and M5 front bars? I was thinking Powerflex 27mm on the front and Superflex 17mm on the rear. Otherwise if I stick with one brand, Powerflex only do a 16.5mm rear and Superflex only do a 26 or 29mm front one which isn't ideal.

Edit: StrongFlex actually do a 17mm rear and 27mm front bushing! Guess I'll use them. mgdmb, would you use the red or yellow ones? I was assuming red as they state yellow are harsher.

 

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Poly is poly. I'd just use the same durometre F/R. As to red / yellow, depends on use case, but I run yellows on the S2. But I track it a lot and don't mind a bit more NVH (and it's honestly not bad anyway...)
 

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Eibach has moved on way past making parts for 20 year old cars like the E39. The bars are no longer available for any application I can find in the USA.
I would recommend a poly that the street focused rather than Race Track focus if that will be 90% of your driving time/mileage.
 

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Discussion Starter · #34 · (Edited)
Eibach has moved on way pass making parts for 20 year old cars like the E39. The bars are no longer available for any application I can find in the USA.
I would recommend a poly that the street focused rather than Race Track focus if that will be 90% of your driving time/mileage.
Yeah I guess they don't sell many E39 ones any more, the cars that were going to be upgraded have already been upgraded.

I am only putting poly on the sway bar bushings, the rest of the suspension bushings I am going to use the stock M5 stuff from BMW as part of the suspension upgrade to Intrax and B8s, see how I get on with it. So I assume if I am just doing the sway with poly, from your earlier comment about NVH, I could go with the track focussed Strongflex bushings (90ShA) rather than street focussed ones (80ShA) for road use without affecting the ride?

I see VAC Motorsports have their own branded brackets that look pretty similar to the Beastpower for slightly more money but if everyone is using Beastpower then I will try those.
 

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Personally I would go with the softer of the two as even that bushing will be many steps harder than the OE bushing. My recommendation is always defer to how you plan on using the vehicle 90% of the time rather than building something that would be great on the 10% by not suitable at 85-95% street driving. Remember these 5 series cars were designed as executive sport sedans not boy racer cars. It you like that overly stiff ride, wide boot spoilers, and slammed bodies then I would recommend looking at M3. There is a large group of owners who enjoy that style.
 

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Discussion Starter · #36 ·
Personally I would go with the softer of the two as even that bushing will be many steps harder than the OE bushing. My recommendation is always defer to how you plan on using the vehicle 90% of the time rather than building something that would be great on the 10% by not suitable at 85-95% street driving. Remember these 5 series cars were designed as executive sport sedans not boy racer cars. It you like that overly stiff ride, wide boot spoilers, and slammed bodies then I would recommend looking at M3. There is a large group of owners who enjoy that style.
Thanks for your 2 cents. What are the purple ones you've got in yours, Powerflex 95ShA? Or something else?
 

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I upgraded years ago so things might have changed but at that time, Powerflex didn't make a bushing for the rear Dinan bar. It'd be nice if they did. I think I put a 16.5mm bushing in and it was not easy but was possible. Really would like a proper 17mm bushing.
 
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Discussion Starter · #39 ·
I upgraded years ago so things might have changed but at that time, Powerflex didn't make a bushing for the rear Dinan bar. It'd be nice if they did. I think I put a 16.5mm bushing in and it was not easy but was possible. Really would like a proper 17mm bushing.
yeah i'm definitely putting in a 17mm bushing, strongflex do one, maybe some others too. Powerflex still don't do a 17mm.
 

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Discussion Starter · #40 ·
Thanks, yeah that would be $175 delivered to the UK, a bit painful but if they are worth it...They do look very thick. The Turnersport ones look slightly thicker than the OEM but not by that much. They claim they are a lot stronger though.

VAC motorsport actually wanted $70 for delivery to UK as opposed to $55 for bimmerzone lol, not good value! For a pair of small brackets. Shocking.
 
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