Rear Brake caliper upgrade
After upgrading the front brakes to the gleaming 6 pot GSXR1000 calipers the rear brake looked too old and big to be allowed to stay.
Initially I was simply going to swap the ZXR caliper for the Nissin item from a GSXR1000K1/2. This looked feasible by spacing the caliper on the hanger and hooking it up to the torque arm taking care of sealing some lube in the joint between caliper and torque arm.
However I never went ahead with that as the whole torque arm arrangement bothered me a lot. For starters the extra weight of the arm and of the bearings inside the caliper hanger are not beneficial to suspension action, but most of all I felt that no matter how well cared for the bearings in the caliper hanger were they never seemed to move swiftly enough for me to be convinced that there would be no effect on suspension movement.
So I set to find a way to do away with bearings and torque arm. I worked out what needed to be done, but I did not have the tools or skills to do it so I asked a local company ( Pretech Engineering ) to do it for me.
They modified the stock hanger by removing the bearings and machining replacement wheel spacers to suit. They attached a small fixed arm to the hanger with a long slot to allow it to anchor itself to a specially machined bolt tip threaded through the paddock stand attachements. This arrangement allows for wheel movement when adjusting the chain, but keeps the caliper secure in its position.
To be centered on the disc the Caliper itself needed to be spaced out on the bracket by placing two round spacers (4mm thick) between the caliper and the bracket at the mounting points.
Once I was sure I was happy with the arrangement I cut off from the caliper the small bracket used to connect it to the torque arm as this was now redundant.
It appears that the GSXR1000 brake disk is thinner than the ZXR item as I had to remove the heatshields from the back of the brake pads as otherwise they would not fit.
If you want to do the same mod, in the UK you can give Pretech Engineering a call. they have kep the specs for the job they did on my bike and should be able to replicate it easily. If you need to use a firm local to you any good engineering firm should be able to do the work given the details and pictures on this page.
The old ZXR caliper weighs 925g against the 600g of the GSXR one, then there is the now redundant torque arm which weighs in at 375g (including the bolt that connects to the frame). This makes for a saving of 700g most of which is unsprung weight!
Beware! Use only calipers from K1/2 model GSXR1000s. The later models look similar, but I believe have different bolt spacing which will mean they won’t bolt to your caliper hanger.