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Wanted - The stepped bolt that fastens the Grimeca caliper to the fork. Previous owner has welded a stud to the end of the stepped section, the weld has snapped when taking the caliper off to remove the wheel to change a tyre (does get a bit like a hole in my bucket I know).

Mdina don't list them and hopefully someone has a spare in their stash they are willing to sell before I resort to getting one made for me.

Thanks Robin

Hi Robin, will your bucket be repaired to see you at Erwood Sunday !?

Steve, I have a plan B to get a new bolt made, but have to wait until next week before this can be done. Won't be able to make it to Erwood on Sunday unless I come by car.

Starting with a bolt/Screw of an adäquate quality and the thick diámetro it can be made with a lathe easily. A friedlich of mine did it for me years ago

Hi Robin.

This probably doesn't help you in the slightest but I've just looked at my own 3½, and photos of about fourteen others, and all but two had the arrangement seen in the pictures below. It looks like a solid bolt at the bottom and stud/nut arrangement at the top.

I don't suppose it makes any difference, just an observation, really.

Hi Jen, yes that's the setup. Bottom bolt is m10 x 1 25, top bolt is stepped. A previous owner had welded a stud onto the shank. This was a bit wonky and broke when refitting the caliper after a tyre change. I'm getting one made up, not hard as Norbert said, but I don't own a lathe and was hoping somebody my have a spare to get me back on the road more quickly.

I have one from a 350, are you going to Hundredhouse Inn and/or Erwood Station meetings this weekend?

Firstly, the originals were definitely a stepped bolt, not stud&nut, but I believe that the large diameter part was a piece of tubing over the bolt as my original bolts stepped section disappeared when derusting whilst having it replated. This resulted in me using a long M8 bolt with with a separate piece of tubing over the bolt instead.
Worked perfectly all the time I had the original caliper on the bike.
Regards,
George

That's lateral thinking George. Great info. I am now sorted, borrowing one from Ian and getting a pair of stainless stepped bolts machined.

I don't think, that it will be a Problem. But stainless steel bolts woluld probably not be the first choise at that place, I guess. At least for MOT?

RobinSF1 wrote: ↑28 Jun 2025 17:21 That's lateral thinking George. Great info. I am now sorted, borrowing one from Ian and getting a pair of stainless stepped bolts machined.

Get some more made!
Ill buy a pair off you, and Im sure the club members will

norbert wrote: ↑29 Jun 2025 09:58 I don't think, that it will be a Problem. But stainless steel bolts woluld probably not be the first choise at that place, I guess. At least for MOT?

I would pick a high tensile bolt, 8.8.

A lot of load through the bolts if braking, generating a bit of heat. 150kg bike plus rider.

Must admit, I didn't think about material strength, but casting my mind back 40+ years to when I studied strength of materials, the cast aluminium boss of the fork leg and disk caliper are going to be more prone to fracture than the threaded section of an A4 stainless steal bolt, they aren't that massive. Whilst not as strong as a high tensile bolt, a suitable grade stainless bolt shouldn't be the weakest point. I've not done any calculations, may dust off my old books as I've not used any of this stuff professionally.

As an aside, I once owned a supercharged 2 litre Lancia Volumex and a front wheel came off whilst in the outside lane of the M6. All of the wheel bolts had sheared. A friend who worked in the school of non-destructive testing at the welding insitute examined the hub with the sheared bolts and his conclusion was that there was corrosion fatigue cracking.

There is a stainless high tensile equivalent. I think it is A4-80. Worth a look.