ARP flywheel bolts - UK supplier on page 2

Hi

Have just got a set of 'Eurospec sport' flywheel bolts for 6 bolt 228mm flywheel (G60 type). $80 USD for a set of 6 bolts but when this is 2:1 like now, a more reasonable 40 (and as they are small, chucked em in my bag to bring home from US trip last week).

Very interesting specs. They are made by ARP (ARP Pro stamped into the head), 12 point 19mm head and have a shank on the bolt unlike vag ones (6 point 17mm head). 2 sizes in the packet, 'master bolt' size 10.1mm dia shank (x1) and others 10.6mm dia shank (x5). For reference, std vag ones have no shank, are threaded all the way, and across the top of the thread are 9.7mm dia. So basically the flywheel is slack on the bolts.....could be why there are the occasional flywheel bolt failures then.....

Very nice, only issue is that they came with no torque procedure - have emailed eurospec asking for one

Cheers

Rob

 

Just to mention they don't have any thread lock sat on the threads ready to go (just adding, though I know you know this!)

So as Rob basically says, bizarrely all VW 6-bolt flywheels have one hole slightly smaller than the rest. I showed this to some VW chaps recently and it was news to them too.

Why would anyone know after all? VW appear to make no use of this by using identical sized bolts for all production applications (AFAIK).

Would be nice to answer this one if anyone knows....

 

The only thought they had was that it could be to counterbalance one of the 6 flywheel bolts that is apparently every so slightly off the same circle as the rest, but the logic failed when we checked where the two positions were (bolt off centre and smaller flywheel hole were relatively).

 

latest - torque figs are as for std bolts

 

IIRC there are two torques - one for the bolt with a shoulder & one without. Spotted it in an old Haynes recently when doing the clutch on the Mk1. Just worthy of a mention.

Anyone got any comments on the bolt hole sizes and so forth? There's got to be a reason out there...

 

How much larger are the holes? Heat Expansion?

 

Effectively these are the sizes, since they fit snug in the flywheel holes, so read them as v. smililar, + a small amount to avoid interference:

Definitely not expansion related I would say.

 

production tolerances and 'use whats on the shelf' I would say

 

But very deliberate somewhere along the line.

 

very deliberate with the offset hole spacing and different size holes but not so clever fitting undersize bolts in such a critical application - its the bolts I was thinking were 'off the shelf' - the offset holes are so you can only fit the flywheel one way but why one is smaller than the rest stumps me

 

Gotcha.

Likewise, and others by the look of it...

 

I can't think of any reason to be honest...

 

Wouldn't they act as a wheel bolt, and just provide clamping force?

The bolt clamps the flywheel to the crank, the clamping force of the bolts holds the parts in place against each other, and there is no shear stress on the bolt once tightened?

Broke

 

you are kidding me - think about it - no shear stress on a flywheel ? only the engine trying to turn it and the wheels/brakes/transmission trying to stop it turning.....

the flywheel isn't dowelled or keyed onto the crank so the bolts act as both clamping and locating

 

Not kidding at all.

Take the engine power you speak of, send it through a trans for reduction and more torque, and the wheel bolts still clamp the wheel to the hub tight enough to not slip and shear the bolts. How do you reckon the engine, fighting the weight of the car, with reduction help, isn't able to shear the wheel bolts?

For that matter, how about the CV bolts holding the axles to the flange? They don't shear, and they're much smaller.

I still think the bolts get tensile stress clamping the parts, and not shear stress. If it saw shear stress, the bolts aren't clamping the parts properly.

Broke

 

The wheel studs have radiused seats to locate them, the flywheel as you know doesn't....

 

So the bolt threads are safe from touching the wheel becuase of the seats....and what keeps the bolt from shearing off at the hub surface?
I'll venture a guess that the clamping force provides enough friction between the wheel backside and the hub face to stop it from doing so

The radiused seats do no more to locate the wheel than the air pressure does. The hub locates the wheel in the center, the bolts hold the wheel to the hub. Use aftermarket wheels without a hubcentric ring to fit the VW hub, and you'll soon find the wheel bolts do not locate the wheel, the hub does. The hub locates and centers the wheel, the wheel bolts clamp it to the hub with enough pressure that the friction between the parts hold them in place. If the wheel isn't centered on the hub, it'll shake the front of the car to death on the freeway.

Look at failed wheel bolts and flywheel bolts....do they look sheared? Most I have seen are tensile failures.

Broke

 

m12 wheel bolts... kinda thick compared to the flywheel jobbies.

not a great design by vag on the flywheel dept.

 

that said, mine runs high 300lbft torque on vr6/abf/g60 type 228mm clutch and flywheel assy and is just bolted in the factory way with factory fixings.

8200rpm, 485bhp (so far) and 355lbft.... limiting factor is road tryes and effective "actual" torque going thru the drivetrain.
I have broken 5th gear early this year tho.. so there is some torque.

{touches wood}

 

off topic possible, I've just done a renualt cam belt, the crank pully is all wrong IMO, that free wheels if the centre bolt does not apply a clamping force between the outer pully & the crank edge

but it works