Any suggestions for upgrading my brakes please?

[TaskMule]

Decelerating a 500kg mass at 1g takes a force of 4.9kN. 500kg is about right for a fully loaded GS and a Moto GP bike can brake at 1.5g, which is way too extreme for the road. 4.9kN at the tyre is about 15kN at the caliper mounting surface (the tyre radius is about 35cm and it's 12cm from the axle to the mounting surface). That's about 4kN per bolt. The shear strength of an M10 bolt is typically 23-35kN. That might imply that if you could brake at 5g, you might shear the bolts. But that is not the case as the majority of the load is carried by the friction between the mating surfaces, because they are clamped together. You would need to be able to brake at 10g+ before the bolt strength became an issue.

So, no, I don't think it's unwise!

As long as the bolts are the correct diameter for the caliper hole, which they probably are then it's perfectly fine. You may want to lightly squeeze the brake lever, with pads in obviously, while you tighten the bolts. But really there's little room for misalignment.
I do agree with a previous post that the original calipers with a new set of brake pads would have given you the results you were seeking. The money spent on the calipers would have been much better spent on new disks to go along with those new pads. If you regularly changed your brake fluid the original calipers should be 100 percent.

 

[ProdigalGS]

If your going to post stuff up here your going to get posts that you agree with and those you don’t. Just for the record I’ve had a few gs 1200 and I can’t remember having brake problems.

I am totally happy to receive posts I don't agree with, that's one of the reasons forums exist. I am not happy to receive offensive posts that criticise my riding when the poster knows nothing about me. That's just rude behaviour by someone with no social skills, as you can see from some of the replies.

I don't have a 'problem' with the brakes, they just don't operate as well as I would like them to, and I am trying to find the best way to address that. I can't recall exactly how they functioned when the bike was new but I also don't recall being disappointed with the progression as I pulled the lever harder.

 

[Spook1969]

I don't have a 'problem' with the brakes, they just don't operate as well as I would like them to, and I am trying to find the best way to address that. I can't recall exactly how they functioned when the bike was new but I also don't recall being disappointed with the progression as I pulled the lever harder.

Have you tried new pads?

 

[ProdigalGS]

There is a thread on here somewhere (maybe 1200/1250 Water cooled thread) that goes into detail about changing the front callipers to M50 or Stylemas. The options were to either remove the dowels or as you say recess the replacement callipers to fit the dowels. From memory the OP of that thread determined that either option was viable

The Stylemas have smaller (30mm vs 32mm) pistons which in theory means you have to pull harder for the same retardation but with less travel. Obviously life is more complex than that but I didn't want to start messing around with different diameter caliper pistons.

 

[ProdigalGS]

As long as the bolts are the correct diameter for the caliper hole, which they probably are then it's perfectly fine. You may want to lightly squeeze the brake lever, with pads in obviously, while you tighten the bolts. But really there's little room for misalignment.
I do agree with a previous post that the original calipers with a new set of brake pads would have given you the results you were seeking. The money spent on the calipers would have been much better spent on new disks to go along with those new pads. If you regularly changed your brake fluid the original calipers should be 100 percent.

I'll take photos when I have taken the old calipers apart, so you will be able to see for yourself. The brake fluid was changed every 2 years from new but that doesn't stop piston corrosion on the 'outside' of the seals or crud build-up. Your comment implies that no caliper should ever need rebuilding if the fluid is changed regularly. I'm not sure I agree with that.

And I reserve the right to buy new discs! This is not about saving money but about getting the best possible braking on a 9 year-old bike. Based on the many helpful comments, I concluded that the calipers and pads were more likely to merit attention than the discs, so that's where I'm starting.

Thanks for the comment though! These are judgment calls and you may well be right, maybe new pads would have sufficed. I still don't regret buying the calipers as they were such good value.

 

[ProdigalGS]

New calipers arrived today, complete with pins, spring clips and banjo bolts. The colour is 'titanium', which I actually prefer to the OE black, which always looked dirty. Note the hole for a 10mm bolt but with no room for the dowel.

 

[GTMorgan]

Pretty sure those dowels will just pull out with a bit of twisting force, many other bikes do not use dowels so the combination of bolt strength and friction of the mating faces is more than enough.
You will just need to apply the brakes before tightening the calipers to centralise them, no need to do this with the dowels as there is no movement once located.

 

[Wapping]

It goes without saying that I’m a “member”

Upstanding, is the word you missed.

 

[Danny]

There's nothing wrong with the power, the brakes work, but the increase in lever pressure required to stop faster (so to speak) seems excessive. Maybe they have slowly degraded over time without me noticing.

And please, no more advice on how to ride a motorcycle.

Is it possible the increase in lever pressure is required due to you gaining a few lbs since first owning the bike?

 

[Spook1969]

Is it possible the increase in lever pressure is required due to you gaining a few lbs since first owning the bike?

So first he cant ride and now he's fat?

 

[ProdigalGS]

Is it possible the increase in lever pressure is required due to you gaining a few lbs since first owning the bike?

That made me laugh. I'm actually a few pounds lighter as I no longer spend my working life sat down, looking at a screen.

I've just fitted the EBC pads and gone for a short ride. First impressions are that they are a big improvement. Good initial bite and the rate of deceleration increases much more linearly with extra pressure. It feels like there is less travel at the lever, but of course there isn't, it's just that you get more deceleration for the same pressure. £60 very well spent.

It may well turn out that I didn't need new calipers but the old ones are cruddy and rusted inside, so I don't really mind. I won't get a chance to fit them for a few weeks.

 

[Danny]

That made me laugh. I'm actually a few pounds lighter as I no longer spend my working life sat down, looking at a screen.

I've just fitted the EBC pads and gone for a short ride. First impressions are that they are a big improvement. Good initial bite and the rate of deceleration increases much more linearly with extra pressure. It feels like there is less travel at the lever, but of course there isn't, it's just that you get more deceleration for the same pressure. £60 very well spent.

It may well turn out that I didn't need new calipers but the old ones are cruddy and rusted inside, so I don't really mind. I won't get a chance to fit them for a few weeks.

Glad you took my comment in jest, as it was meant to be.
Good to hear the new EBC pads are an improvement.

 

[Barnoe]

Is it possible the increase in lever pressure is required due to you gaining a few lbs since first owning the bike?

Crikey i need to upgrade!

I'm going with a second disc on the rear and a reverse thruster!