Bolt sizes

[Ride_on]

I always knew Volvo's where metric, but on trying to source nice shiny replacement bolts for my rebuild I am confused by pitches.

Seems cars use 'Metric Fine', which are signified by yellow coating. Anyone confirm or deny this?

http://www.namrick.co.uk/acatalog/Home_ ... ts_29.html

I thought most bolts where standard, but the brake carrier bolts where 'fine'.

[Ride_on]

Also, anyone know the spec of the spire plates?

The metal clip things that the wings etc bolt to, using woodscrew type threads.

My best guess seems to be 6mm dia threads = No. 12, which is what most are selling, or is there a metric version?

[volvodspec]

yup, nearly all bolts/nuts on a 300 are metric, and some bigger bolts are metric fine
wishbone bolts, front subframe bolts, 360 engine mount bolts etc etc, all metric fine. color isn't allways zink-yellow though but thats a small detail

i thought the brake caliper bolts were M16x1.5 but not sure on that; can measure it tomorrow eve as i have a few spare lying around

[Chris_C]

There is a mix of fine and standard, also some metric threads have 2 or 3 "fines" defined in the standard. Best is always to measure, but things like 1.7 starter motor bolts are random and rare M8 with 15mm head rather than 13mm. Currently that part number related to a 13mm head replacement though... so you need to buy a whole new set of round the corner spanners....

Also a number of imperial fixings as I'm sure you know dotted round on brakes, seatbelts etc.

[Ride_on]

Its for rear suspension at the moment, measuring with verniers looks like 1.5mm pitch (peak to peak using 10 gaps), so these are standard according to Namrick

Spring end x4 : M10x100x1.5mm
Spring Shackle x 2: M10x130x1.5mm
Axle-spring plate x 4: M10x40x1.5mm
Axle-Spring plate + strengthener x4: M10x50x1.5mm
Axle-Hub x 8 : Cap socket M10x45x1.5mm

The spire U clips seem to be No. 14, accoring to some random american web site (6.3mm, I measure 6.1mm)

Quite a difference in price eg for M10x100
N&B £1.13 (68p for 10+) (grade not shown)
Namrick: 58p (Grade 8.8 for hex bolts and 12.9 for Socket)

The grade is the max force per csa, right?

[Alex Laidlaw]

As a general rule on the 300s and most 80s/90s cars anything M10 or smaller is standard ISO coarse thread, so stocking these sizes is helpful. Anything larger tends to be much harder to guess and as Chris says a number of imperial fittings still crop up.

Renault have a love affair with M7 threads, which is rather annoying because nobody else uses them and they're difficult to find. There are plenty of examples of this on the F7 engines, not sure if there on the 1.7 engine as well.

You can get most fasteners for a lot less than that website posted earlier in the thread. You won't be able to get anything non-stock size (usually including M7!) unless you want to buy a box of a 1000.

[Alex Laidlaw]

The grade is the max force per csa, right?

It's a rating of tensile and yield stress, which is force over area. The first number is the tensile strength (in 100x MPa) and the second number is a ratio of yield/tensile strength. Always check what is written on the heads of the bolts you remove and never use a lower grade bolt than you remove. Grade 8.8 is the general absolute minimum to use anywhere, they're so cheap there's no point risking using anything less unless you're into mass production.

Use stainless steel bolts with great care. They use a different head marking system and are generally sold in low tensile varieties. They are also prone to binding when threaded into something that is also stainless steel. Assuming you are not building a boat, so don't use them for anything structural.

[Ride_on]

yup, nearly all bolts/nuts on a 300 are metric, and some bigger bolts are metric fine
wishbone bolts, front subframe bolts, 360 engine mount bolts etc etc, all metric fine. color isn't allways zink-yellow though but thats a small detail

i thought the brake caliper bolts were M16x1.5 but not sure on that; can measure it tomorrow eve as i have a few spare lying around

Are they not M10? I'm pretty sure they are finer pitch than all the other 17mm head bolts (ie <1.5mm), or do they have a larger shaft than normal, making it look finer.

[Ride_on]

The grade is the max force per csa, right?

It's a rating of tensile and yield stress, which is force over area. The first number is the tensile strength (in 100x MPa) and the second number is a ratio of yield/tensile strength. Always check what is written on the heads of the bolts you remove and never use a lower grade bolt than you remove. Grade 8.8 is the general absolute minimum to use anywhere, they're so cheap there's no point risking using anything less unless you're into mass production.

Use stainless steel bolts with great care. They use a different head marking system and are generally sold in low tensile varieties. They are also prone to binding when threaded into something that is also stainless steel. Assuming you are not building a boat, so don't use them for anything structural.

I know SS is more brittle, I was just concerned about the stretch to torque ratio for higher grades. I guess might not stretch as much, but will end with the same holding friction for the same torque.

Probably not that critical in the springs, but the hubs are and I have selected 12.9 grade. I think the OE bolts say 8.8 on them.

Also most nuts on my car (1987) seem to be squashed bolts (ie they have some locking friction), I've selected nyloc mainly, but again the hub-axle socket bolts are quite short (not much sticking out the other side) and its close to the brakes so heat could be a problem. Either problem 'might' be ok, but any recommended substitutes?

[volvodspec]

caliper bolts are M12x1.25

std metric tread;
M6x1
M8x1.25
M10x1.5
M12x1.75
so all the leafspring and axle bolts you mentioned are standard M10, and all in 8.8 grade.