Sunday, 10 March 2013
Skorpion front brake modification
As I've owned my silver Traveller for over 12 years now, I thought it was time I started writing about some of the modifications I've done to it.
First article will be on the replacement of the standard Grimeca front brake master cylinder and caliper with Brembo units.
Before I start, the usual disclaimer applies – if you do any of the things detailed here and it goes wrong, don't blame me. You're big boys and girls, so you should know whether or not you're competent enough to do the work. If not, get someone else to do it. OK?
I did this modification four or five years ago, so it's been well tested. In that time I've been to the Alps a couple of times, so I've been up and down roads that look like this:
The standard Grimeca setup works very well, but is basically a cheaper copy of a Brembo and isn't as well made. It also lacks an adjustable lever, so the span may not suit everyone. Also, with the spares situation for Skorpions being a bit uncertain, it's always useful to know of an alternative part.
The caliper is a copy of the Brembo P 30/34 unit used on lots of European bikes, plus European built Yamahas, so is fairly readily available used on Ebay. Look for calipers with a 40mm spacing of the mounting holes – later ones are 63mm. One tip when buying one is to look for the smallest and least common bike it was fitted to as prices are lower – a caliper from a Cagiva 125 can sell for a half of what an identical unit from a Ducati 916 will, so shop around. The caliper (and master cylinder) I used were from a Cagiva Mito 125.
Basically, this is a straight 'bolt on'. The hose connection is the same thread so you could reuse your old hose. Both the Grimeca and Brembo calipers use a pad pin retained with a circlip. I've never been very happy with this arrangement, so have replaced it with a M6 nut and bolt.
You need to find a bolt long enough that the pads will slide on the unthreaded portion, and cut the excess threaded part off. Fit with a pair of washers and a nylon insert nut.
This is a common modification used by racers and will pass the British MOT (annual safety test). I think you have to drill through the inner hole to enlarge it to 6mm (I can't remember now).
This diagram shows the dimensions of the bolt
Despite what 'self appointed experts' might tell you, there is no difference between gold Brembo calipers and other colours. The calipers are just painted (not anodised), so you can repaint them if they are a bit tatty or if you just want another colour.
I had bought the master cylinder and caliper as a pair, but any suitable master cylinder will work. It doesn't have to be a Brembo, just as long as it has a 13mm piston diameter (Brembo cast the size on the bottom). As the Mito doesn't come with an adjustable lever, I fitted one from a Ducati 916. Again, the hose connection is the same thread, so you could use your original hose.
I compared the span of the levers between the Grimeca and Brembo master cylinders. Sorry the pictures aren't very clear but they were taken in a cramped garage as it was snowing outside!
Firstly, the standard Grimeca has a fixed span of c.120mm.
The Brembo at minimum is c. 105mm.
and maximum of c. 125mm
When I fitted my caliper and master cylinder I had a new hose made and used some shiny bolts, but you could reuse your existing parts.
In use the adjustable span is good as you can 'fine tune' it to suit your hand, and the setup has a better 'feel' that the Grimeca original, although it could have started to get a bit worn.
If any one else does a similar modification, please post details.