Torque value 1997 K1100 front caliper bolts...

Hi Everyone-

I'm usually over in the airhead and vintage sections, but have a question that brings me into the K bike zone.....so I hope I posted in the right place!

I'm building a /2 conversion bike (1965 R50/2 with a 1974 R75/6 engine), and doing a front disc brake conversion. I'm using a Brembo 4 pot from a 1997 K1100 (and other bikes from the era I believe), and am wondering if anyone cal tell me the torque value for the body/bridge bolts securing the 2 halves of the caliper body together.

On disassembly for cleaning, it would appear that the longer outer bolts had some kind of factory thread locker on them, but the shorter inner ones did not. New pads arrive tomorrow, and so would like to get it ready for mounting.

Any insight is appreciated!

Thanks in advance,

ECJ

Hello,

According to the factory K1100 repair manual, "The brake caliper halves must not be unscrewed."

The manual does not provide a torque value.

Regards,

View attachment Doc1.doc

what about for a rebuild...?

Hi richo2006-

Thanks very much for the response! I wasn't able to open the attachment, but since rebuild kits are sold for these calipers (that include pistons and seals), the only way to do that is by separating the halves, so a torque value must exist somewhere. I'm sure I could follow general torque specs for this size fastener, and use Loctite on the 2 outer screws, but since it's such a critical piece of kit, actual values would be nice!

Surely someone has rebuilt one of these and knows......

ECJ

Clymers suggests:

Install inner two bolts first @ 18.4-25.8 ft.-lb. (no loctite)

Then install the outer two bolts with red loctite @ 3.6-7.4 ft.-lb.

BUT, there appears to be some confusion/typo as far as to the table number in the manual. So use only if it makes sense. Remember, you are threading steel bolts into aluminum. Don't strip out the caliper threads!

I have no experience with the 4 piston calipers.


It does make sense that the outers are used as bridge bolts and over tightening would distort the caliper. The low torque would require the loctite to maintain tightness.

Lee-

Nice! Thanks. It does make sense, although that is quite a low torque number for the longer outer bolts, even with Loctite, but I suppose possible distortion, as you suggest, may be the reason. The higher end of the inner bolt torque numbers is about right where I torque cylinder head studs on an airheads aluminum crankcase, so that number also makes sense.

Can you say more on the confusion/typo you mention?

Thanks again,

ECJ

One thing to verify before bolting the halves together is the surface trueness on the threaded half of the caliper. It’s common for the steel bolt torqued into the aluminum caliper half to cause the surface to well up around the threaded hole. That has to be surfaced down to a true and flat surface or the caliper halves may not draw up and seal. Some elbow grease and a surface plate and very fine sandpaper are usually all that’s required. Wash everything thoroughly before assembly.

Best,
DG

Hello,

You remove the pistons by using compressed air.

Hopefully you're able to open this attachment.



Regards,



View attachment brake Caliper.pdf

Thanks for the attachment, richo2006! I was able to open it this time.

DG-

Good point on mating surface flatness. Both surfaces looked good, but I will check again more thoroughly before reassembly. I'm a machinist and a welder by trade, and so am very picky!

I'll report back after getting it back in service.

Thanks all!

ECJ

ecjjce said:

Lee-


Can you say more on the confusion/typo you mention?

Thanks again,

ECJ

Click to expand...

They say refer to torque values in table 12. There is no table12 in that section, only a table 11.

It lists inner and outer caliper "mounting" bolts. I wouldn't call those bolts mounting bolts, but there are not inner and outer bolts that mount the caliper to the slider.

Mounting bolt torque values....

Lee-

Copy that. Appreciate the clarification!

Speaking of caliper mounting bolts, i.e. the bolts that mount the caliper to the slider, would you happen to have those recommended torque values?

I made up a small 'double eared' plate from 1/4" cold rolled 1018 steel that I will TIG weld to the right trailing arm of the Earles fork to hang the caliper from. The plate has tight locating/through holes, and the caliper body will be bolted and torqued against the back of this plate, so having those values would be helpful if easily available. I also assume that these bolts should probably get Loctite (and probably blue).

All best,

ECJ

ecjjce said:

Lee-

Copy that. Appreciate the clarification!

Speaking of caliper mounting bolts, i.e. the bolts that mount the caliper to the slider, would you happen to have those recommended torque values?

I made up a small 'double eared' plate from 1/4" cold rolled 1018 steel that I will TIG weld to the right trailing arm of the Earles fork to hang the caliper from. The plate has tight locating/through holes, and the caliper body will be bolted and torqued against the back of this plate, so having those values would be helpful if easily available. I also assume that these bolts should probably get Loctite (and probably blue).

All best,

ECJ

Click to expand...

the mounting bolts should be 24 foot pounds - the same as on the K75s.

Paul-

Fantastic. Thank you.

ECJ