9 replies to this topic

[JonnyAlpha]

Hi fellas,
Can someone confirm a couple of nut sizes for me (been asked loads) the ones I need to confirm are:

The captive nuts that hold the radius arm bracket to the LH and RH front ends of the Rear Subframe.
The Nuts that fit onto the threaded bolt on the LH and RH rear of the rear Sinframe. The studs that hold the rear subframe mount.

The 2 x captive nuts in the rear side of the front main spar of the rear sunmbframe. Just under the handbrake guide, one holds the exhaust bracket, can't remember what the other was.

Thanks

[zerobelow]

Sorry I can't recall exactly the sizes, but maybe a few tips until someone more useful can reply: The default size for things seems to be 5/16 unf. For the rear subframe, start there.

 

The radius arm brackets were 5/16 unf on mine -- a new heritage subframe. However, they were messy threads, since they were tapped from the factory by using a tapping bolt (which was the final fastener in my case). Putting it back together, I found that using allen cap bolts was easier on the 2 bolts that will be hidden by the radius arm -- unless you have very thin walled 1/2" sockets (grab the 1/4" drive ones if you go standard bolts). The length on those should be short -- I think 3/4" or so. Too long, and the threads sticking through apparently tend to rust, making later removal harder.

 

The bolts holding the trunnions to the car were 5/16 unf as well. Length, I think, was 2" to 2.5" on the long ones.

 

Not sure on the exhaust hangers,my car had welded hangers.

 

If you keep a supply of 5/16 unf stuff, you'll be in good shape. Add in 1/4 unf and 3/8 unf, you'll be better. I also found a bit of 5/16 unc and 3/8 unc in the engine bay, too.

Edited by zerobelow, 04 March 2014 - 05:48 PM.

[tiger99]

The rear subframe trunnion bolts and camber bracket bolts are indeed all 5/16" UNF, as are many other bolts on the Mini, with some 3/8" UNF, and both 5/16" and 3/8" UNC on the transmission case, where the coarser thread is better in the soft alloy.

 

There are many different lengths used. The other thing that needs to be specified when procuring bolts is that they MUST be grade 8.8 in most cases. The stronger grade 10.9 is ok in a few places, but not in others, and 12.9 should not be used at all, as although having a higher tensile strength, ductility is lacking and the fatigue strength, which matters in many cases, may be less than the common 8.8 bolt. Beware of being supplied bolts made of mild steel, or any grade less than 8.8, or Chinese cheese.

 

If you go to the link below, select, say, item 115, and click on buy now (don't need to buy!), then it brings up the part number, price, diameter which is 5/16" UNF, and the length, which is 2.5" for the longer trunnion bolt.

 

Edit: I forgot the link, here it is now:

 

http://www.somerford...roducts_id=3568

Edited by tiger99, 04 March 2014 - 07:50 PM.

[JonnyAlpha]

Thanks guys, I sort of knew it was 5/16 but could not remember whether  it was UNF or UNC I also tried a 5/16 UNF in the Radius Arm Bracket Encapsulated Nut and it didn't seem to want to screw in and I did not want to force it. The internal thread is full of crap so i'll clean it and have another go.

 

Where I am working at the mo has a nut and bolt store so I might be able to get a small supply however are the grades marked on the bolts??

[tiger99]

Yes, they are marked, and normally show 8.8 on the bolt head, but there are other ways of indicating the strength too. If they are not specifically marked, they are mild steel, NOT for use on any car! I posted some links about this topic here:

 

http://www.theminifo...gine/?p=2335347

[bikewiz]

Here's another link 

http://www.boltdepot...rade-Chart.aspx

[tiger99]

Yes, good link, but be aware that a US grade 5 bolt is similar to ISO 8.8, so if the bolt has the three radial lines at 120 degrees to each other, it is ok. You don't need a US grade 8! You may find the three lines and 8.8 on the same bolt, if it meets the ISO and ANSI standards.

 

It is very annoying, and potentially dangerous, that different parts of the world still use different bolt gradings. In WW2 the Unified bolt series was developed, to ensure compatibility of spares, and was successful as far as it went, but 70 years later, the job still is not done completely. The ISO standards are supposed to prevail, but too many vested interests in the US do not agree. Sometimes, they have very good reasons, for example the UNJ aerospace thread is stronger than any other.

 

Still, there is one very big advantage in the US not having fully standardised and gone metric, yet. The supply of UNF/UNC bolts in the UK may dry up, but we will be able to source them from the US for a very long time, and US bolts are of decent quality, not like certain Chinese items.

[bikewiz]

Yes, good link, but be aware that a US grade 5 bolt is similar to ISO 8.8, so if the bolt has the three radial lines at 120 degrees to each other, it is ok. You don't need a US grade 8! You may find the three lines and 8.8 on the same bolt, if it meets the ISO and ANSI standards.

 

It is very annoying, and potentially dangerous, that different parts of the world still use different bolt gradings. In WW2 the Unified bolt series was developed, to ensure compatibility of spares, and was successful as far as it went, but 70 years later, the job still is not done completely. The ISO standards are supposed to prevail, but too many vested interests in the US do not agree. Sometimes, they have very good reasons, for example the UNJ aerospace thread is stronger than any other.

 

Still, there is one very big advantage in the US not having fully standardised and gone metric, yet. The supply of UNF/UNC bolts in the UK may dry up, but we will be able to source them from the US for a very long time, and US bolts are of decent quality, not like certain Chinese items.

Agreed I've used some US grade 8 bolts as the strength is slightly higher than ISO 8.8 but lower than ISO 10.9 I had a bunch of problems with the 5/16 x 24 UNF bolts on the tie bar stripping before even coming close to the 20 ft/lbs dry torque, I put it down to cheap non genuine bolts that I bought from one of the Mini suppliers.

[bikewiz]

Another link in regards to US spec grade 5 and grade 8 bolts.

http://tinelok.com/g...de-8-fasteners/

[Guess-Works.com]

Watch out  Tiger... That's twice you've mentioned Chinese...

 

The Racism police will be after you ;)