R1250GS calliper bolt length

[Daggerit]

Morning gents,

Just wondering if anyone knew, or could point me towards a site which could tell me, what the front calliper bolt sizes are for a 1250? Looking to put some slightly larger discs on so need some spacers and longer bolts but need to know the original length first. I'd take mine out and measure but my torque wrench has been lent out and I won't have it back for a while to get them done up again.

TIA

Dan

 

[Deleted account 191119001]

10 Hexagon-head bolt with shank M10X65 8.8 4 34117719823

http://www.realoem.com/bmw/enUS/sho...0-BMW-R_1250_GS_19_0J91,_0J93_&diagId=34_2619


Not sure about the thread though......

 

[Daggerit]

10 Hexagon-head bolt with shank M10X65 8.8 4 34117719823

http://www.realoem.com/bmw/enUS/sho...0-BMW-R_1250_GS_19_0J91,_0J93_&diagId=34_2619


Not sure about the thread though......

Yeah, wonder why they’re M10 versus the M8 of older bikes... And surprised they’re carbon steel rather than stainless too.


Sent from my iPhone using Tapatalk

 

[BillWright]

Hi

They are exactly the same on the 1250 as the 1200LC if that helps. I swapped the Roadlok over and used exactly the same bolts and spacers.

 

[Deleted account 190920001]

It's the same bolt from 2009 according to the part info.

Manufacturers will not use stainless steel for structural bolts as they are not the correct grade. Not to say you can't as I have done many times in the past but manufacturers simply won't.

 

[ChazzyB]

Bigger disks? Does it need them?

 

[Deleted account 191119001]

Bigger disks? Does it need them?

Good question, and for the not Engineer style person, what would the bigger disk do, I am asking in all honesty...

 

[ChazzyB]

I wonder how much clearance to the rim the calipers will have when mounting and removing them.

 

[autogs]

or even discs

 

[Deleted account 191119001]

or even discs

Feck off or I will tell Tarka..........

 

[ChazzyB]

or even discs

 

[Tarka]

Feck off or I will tell Tarka..........

You missed the "calliper" though......

 

[Daggerit]

Bigger disks? Does it need them?

I've found that they fade under heavy road use and since I want to take it on some track days with friends I want to make sure it can stop.

Good question, and for the not Engineer style person, what would the bigger disk do, I am asking in all honesty...

It just works on the torque principal in that if you move where you're applying a given clamping force further away from the wheel centre you get a larger braking force overall. The same as using a breaker bar versus a little ratchet for torquing a bolt. It means that you can get the same braking effect with less overall heat being generated in the system basically, which should keep my brakes working more consistently for longer. That's the theory at least!

 

[Daggerit]

It's the same bolt from 2009 according to the part info.

Manufacturers will not use stainless steel for structural bolts as they are not the correct grade. Not to say you can't as I have done many times in the past but manufacturers simply won't.

That's what I don't understand since something like an A4-80 stainless is almost identical in mechanical properties to the 8.8 that they put in. Granted it's probably more down to cost since they'll be a lot more expensive over a large number like they'd need.

 

[Greg Masters]

It means that you can get the same braking effect with less overall heat being generated in the system basically

Bigger brakes does not mean you generate less heat.

As you have already identified, larger diameter discs gives greater mechanical advantage but, because the swept area of the disc is also larger, you have a greater surface area for heat dissipation. This should, like for like, mean that the temperatures remain lower even though generated heat is the same.

Be careful with stainless bolts - they do funny things with brake components.

 

[fred_jb]

I've found that they fade under heavy road use and since I want to take it on some track days with friends I want to make sure it can stop.



It just works on the torque principal in that if you move where you're applying a given clamping force further away from the wheel centre you get a larger braking force overall. The same as using a breaker bar versus a little ratchet for torquing a bolt. It means that you can get the same braking effect with less overall heat being generated in the system basically, which should keep my brakes working more consistently for longer. That's the theory at least!

The brakes convert the kinetic (speed related) energy of the bike into heat. A given reduction in speed will result in a specific amount of energy being turned to heat in the brakes. With bigger disks it may be spread across a slightly larger amount of metal, but I would think any difference in temperature will be marginal, and may even get hotter if the bigger disks allow you to slow down faster, with the increased temperature being due to the same energy going into the brakes in a shorter period of time.

 

[Daggerit]

Bigger brakes does not mean you generate less heat.

As you have already identified, larger diameter discs gives greater mechanical advantage but, because the swept area of the disc is also larger, you have a greater surface area for heat dissipation. This should, like for like, mean that the temperatures remain lower even though generated heat is the same.

Be careful with stainless bolts - they do funny things with brake components.

So are you trying to say that although the mechanical advantage is higher (so assuming that for a given pressure of the pads against the disc the actual braking force is greater), that you wouldn't generate less overall heat? The physics of that doesn't make sense in my head because, given you slow the bike the same rate, the actual work done by the system is less surely?

For the bolts, are you talking about there being a galvanic corrosion issue or something different?

 

[Boxflyer]

Here's the parts from RealOEM

 

[Daggerit]

Thanks for the responses guys!

 

[Greg Masters]

So are you trying to say that although the mechanical advantage is higher (so assuming that for a given pressure of the pads against the disc the actual braking force is greater), that you wouldn't generate less overall heat? The physics of that doesn't make sense in my head because, given you slow the bike the same rate, the actual work done by the system is less surely?

For the bolts, are you talking about there being a galvanic corrosion issue or something different?

For a bike being slowed by its brakes, the amount of energy (e) that is converted to heat can be expressed as:

e = (mV12) - (mV22)​

where m is the mass of the bike; V1 is the speed of the bike before braking; V2 is the speed of the bike after braking. Brake disc size doesn't enter the equation.

It should be noted that the function is not linear. The heat generated slowing from 120mph to 100mph is massively more than slowing from 30mph to 10mph.

I think that if stainless was best for brake components, they would use in OE in production.