U-bolt nut size

[tingo]

I'm going to have to cut the nuts off my u-bolts on the rear suspension. I can't shift them after a week of soaking in Plus-gas.

Do you know what size nuts I will need to replace them? I don't want to buy new u-bolts as I am only undoing them in order to fit a new bump-stop.

Do you keep a spare set of nuts which are generally useful for the 1000? If so what sizes?

Thanks.

[bmcecosse]

Chassis nuts/bolts tend to be BSF thread - and engine etc tend to be UNF thread. And - replacement parts tend to be Metric thread these days! So - there are various possibilities for your U bolts - what spanner size fits them snuggly ? And - have you tried heating them ? A gas blowtorch should do the trick. If they have been assembled correctly - there should be a thick 'full' nut against the spring pan - followed by a thinner 'lock' nut. You need to get the lock nut off first - don't try to wind them both off together.

[tingo]

The nuts are between sizes on my imperial spanners. I was able to "tap" one of the metric spanners on with a hammer, possibly 13mm?

I haven't got a blow torch, but I have got a hot air paint stripper - like a hair dryer only VERY hot. Would that be a good idea?

[bmcecosse]

Get a blow torch - VERY cheap at Lidl/Aldi etc - worth weight in Gold. The nuts are probably 1/4" Whitworth then ! BSF thread. You will need some Whitworth spanners/sockets for jobs around the chassis.

[tingo]

I don't understand these different types of imperial spanners
1/4" sounds like 6mm to me, not 13mm.

I'm sure you are right but GRRRRR anyway.

[paulk]

1/4" whitworth refers to the threaded bits width and type
1/2" AF is Across Flats (ie bolt head size)
and 13mm spanner is again across head (a 13mm head spanner is usually M8 or 8mm thread)

Hope I have spread confusion

[mike.perry]

Some of the more common threads are
BSF = British Standard Fine. 1/2" BSF = 16 Threads per inch
BSW = British Standard Whitworth. 1/2" BSW = 12 TPI
Both these threads use Whitworth Spanners

UNF = Unified Fine. 1/2" UNF = 20 TPI
UNC = Unified Course. 1/2" UNC = 13 TPI
Both these threads use A/F Spanners

There also such things as pipe threads which are tapered and also metric threads.

There are exceptions to the thread / spanner rule, for instance the Series MM S/V engine uses metric threads but has Whitworth heads on the nuts and bolts.
The M1000 wheel stud uses a UNF thread but has a Whitworth head on the wheel nut

[minor_hickup]

I believe the thread is 3/8" BSF, so you need a 5/16" Whitworth spanner/socket

[linearaudio]

.....the Series MM S/V engine uses metric threads but has Whitworth heads on the nuts and bolts....

I've not heard of that one before! Can anyone give an educated guess why our great British motor manufacturer should have gone metric that early in life? Was the side valve design "borrowed" from abroad maybe?

[mike.perry]

Something to do with using French Hotchkiss engines in the past but standard British spanner was Whitworth

[tingo]

Thanks for all the input. I am no less confused!
It looks like I have three options:
1) Buy a blowtorch and a 1/4" or 5/16" Whitworth spanner
2) Buy a new set of u-bolts with matching nuts
3) Use a hot air paint stripper, a metric spanner and a bucketful of luck. Probably followed by number 2)

[8009STEVE]

4) angle grinder followed by 2)

[tingo]

quicker and easier but it would be more satisfying to get it apart

[d_harris]

If its really that hard to get apart then theres a fair chance you will shear the bolt, so I'd go with Steves Suggestion...

[mike.perry]

If no angle grinder then hacksaw and hard work. If you order the new U bolts tomorrow morning by the time you have sawn the old ones off then the new ones will have arrived!!!!!!

[bmcecosse]

The hot air thing will not work - don't waste time on it. The blowtorch WILL work - buy one !