Grade 5 Titanium Caliper Mounting Bolts - Yes or No

[Soliton]

The rear calliper in the 1150r is mounted using two M10 x 25 torx bolts. The BMW fiche does not list a bolt grade but a check of the installed bolts shows they are 10.9.

A fiche check of the same bolts for the front callipers does indicate a bolt grade - M8X32-10.9 ZNS3 (Grade 10.9 galvanised)

10.9 has a rated yield strength of approx 940 MPa / mm squared and tensile strength of approx 1040 MPa / mm squared. These ratings are approximately 20% higher than a grade 8.8 bolt

The rated yield for a rolled grade 5 (6Al4V) Ti is approx 848 MPa and the tensile strength is approx 1031 MPa. These are averaged values generated using the minima and maxima for the material. If the absolute minimum values are used they are lower than the 10.9 spec

My question is... is it safe to use Ti bolts to mount callipers. The bolts themselves run through cast aluminium. The aluminium at the mounting point is thinner than the diameter of the bolt and from a materials perspective is a significantly weaker material.

This suggests that any failure will occur in the calliper itself , or the point at which it mounts to the fork/ bevel box before the bolt itself fails. I have seen one fail and this is exactly what happened.

Any advice/ practical experience/ horror tales of catastrophic failures?

Rs,

Sol

[AZBMWRIDER]

I work in commercial aviation and titanium fasteners are used to reduce weight, corrosion resistance and high temp applications, never used in high stress areas .

I'd use a high grade steel bolt, like you said the caliper will most likely fail long before the bolt fails .

[riceburner]

I work in commercial aviation and titanium fasteners are used to reduce weight, corrosion resistance and high temp applications, never used in high stress areas .

I'd use a high grade steel bolt, like you said the caliper will most likely fail long before the bolt fails .

That.

On a BM the weight saving from a couple of Ti bolts will be irrelevant. You'd save more weight taking off a t-shirt.

Its nice to have Ti, but if it's not going to help in any way then why spend the money?

[sweatmark]

People use the rear brake?

[riceburner]

People use the rear brake?

Hillstarts.

[EasyBee]

https://www.asphaltandrubber.com/lifest ... otorcycle/

[Soliton]

Sad fact of the day regarding cost of titanium bolts....

I called BMW Australia to obtain a price for one of the bolts in question. The asking price was AUD$ 26 that equates to approximately USD$ 18

If I purchased Grade 5 (6AL4V) Titanium bolts, rolled not cut at full retail price they are AUD$10 (approx USD 7) If I take the time to buy them from the factory (and yes they will sell them individually) they are AUD$3 (approx USD 2)

BMW parts are appallingly expensive here. They are much cheaper in the US but US postage rates are quite high. Generally the best compromise in Australia is parts from the UK. When cost and postage is combined the cost is half or two thirds the local price.

Rs,

Sol

[riceburner]

Sol, I had no idea you were in Oz! I thought you were based in the western US for some reason.

Hope you're not too badly affected by the wildfires.

[Soliton]

It’s Australia, it floods, it burns.

This past five months have been a bit grim but everyone just tries to get on with what needs to be done. I spent some of the new year helping at an evacuation centre but one of the odd things that brought it home to me was putting on my helmet and realising it reeked of bushfire. Our place is ok at the moment but in 2003 I had toddlers at home and could see the fires from my doorstep.

Lots of folk have it much worse. I have job, my boys are fed and I live it a peaceful first world country. In the big picture , very little about which to complain.

Thanks for the thought though.

[sweatmark]

We had bad fire season in Oregon a few years back, with smoke that settled in valley for weeks making everything BBQ flavor. Forest fires were normal, just the wind patterns unusual.

Without local knowledge I don't know how to interpret the Aussie fires: seasonal, exceptional, unexpected? We also see reports of arson as cause.

Back to bolts: given crazy price of BMW fasteners, I would certainly choose stronger + affordable. I've done same for R1150R fasteners with low torque or "untorqued" role, like the Paralever strut rod, where I've used SS Nylon insert locknut instead of OE parts.