Thunderace rear caliper problem

[papercutout]

So I got myself a thunderace rear caliper the other day on ebay, nice and cheap. I need new rear pads anyway, so it seemed like an ideal time - the bike is a 1999.


Except it doesn't fit, absolutely nowhere near. What years Thunderace calipers were meant to be right (I did a LOT of hunting through this forum trying to find that out before I bought it, but found absolutely nothing from anyone stating any years). Mine was listed as being 1998/1999.

There's no chance this will fit at all, please see the pic. Even if I ground 1/2" out, the bolt holes still wouldn't line up! Does anyone know what caliper this bike is from? If it's a Thunderace, what year should it have been? And is there a bracket out there I could fit that it'll fit to? (e.g. TRX bracket)


Thanks for any help.

[noggythenog]

As far as ive read then the thunderace caliper doesnt fit.....only the fazer thou caliper will fit with slight modification.




I think what youve read is that allot of folk use the thunderace torque arm.


Gutted


Never mind, back on ebay papercutout

[kebab19]

The standard Thunderace rear caliper is not a bluespot, I know this 'cos I have one fitted on my own bike ... see picture of it in link about a quarter of the way down the 2nd webpage:
http://foc-u.co.uk/index.php/topic,8167.25.html
But the T'ace caliper fits onto a TRX850 bracket, not the standard FZS600 bracket.

That looks like the rear caliper off an early R1 (1998-99 4xv model).  Are the caliper's mounting holes about 82mm apart centre-to-centre? Sadly if that's the case it won't fit, and the R1 mounting bracket fits the swingarm & has no mounting point for a torque arm.
Bluespot rears from early 2001-05 Fazer 1000's and XJR1300s (can't remember which years) are the only ones where the mounting point holes definitely match the standard FZS600 mounting plate holes. 

[papercutout]

Ok, just rechecked the advert. My bad, it's advertised mostly correctly, I just got it all wrong. Too excited at getting a caliper cheap. Dammit! I'll just have to re-sell and I'll buy pads instead.

[kebab19]

If there's enough interest I'll look into the possibility of fabricating a rear mounting plate that supports these early R1 calipers; I've noticed there's 20 or more of them on ebay & they're bound to be less seizure-prone than the standard rear caliper.

[papercutout]

I'd be interested, but it doesn't look easy (since I wondered about it while outside, looking at it not fitting my bike).

Whereabouts in the country are you?

[kebab19]

There's the caliper you need (XJR1300):

# 281392917678

Not cheap but looks in pretty good nick

[papercutout]

PM'd about an idea.

[papercutout]

Ok, so hopefully this will come up for people who search in the future - I have a new conclusion:


An early R1 caliper has 38mm pistons, the same as the stock FZS600 ones, so probably not much gain. If you could get it to work... BUT no matter what I did (I spent hours making a small bracket and fitting/bleeding it so it was 'perfect') it wouldn't work properly. My guess is that the master cylinder for the rear brake on an R1 is bigger than the FZS600 one as it simply wasn't pumping enough fluid, even after lots of bleeding, to get the pads to grip the disc properly.

So conclusion is: R1 rear calipers have been tried, but they don't work. What is next that people wonder about? XJR1300? :p

[unfazed]

The only blue spot caliper that will fit is the one from the FZS1000 01-05 or the later XJR1300 from 2002 onwards will fit.

As Noggy says only the torque arm from the Thunderace will fit.

The caliper you have is most likely from an R1.

The original caliper is a good caliper and the problems with it stem from lack of maintenance.
Its design means that the drain holes in the bottom of the caliper are small and require regular cleaning to prevent blockage from road grime.
When they block the water and particularly winter salt laden water sits in the bottom and corrodes the caliper causing it to stick.
The blue spot calipers do not suffer like it as the pads are replaced from underneath which means the bottom is open and water drains off immediately. However they will also suffer corrosion (less so ) if not maintained

[papercutout]

You're definitely behind on the contents unfazed, we've established it's an R1 caliper already!

I don't really care about hearing the whole 'the original is a good caliper' stuff - I've searched so many caliper threads recently, I've seen loads of people (or possibly yourself in every thread) harping on about it. If it was that good, why do people replace them?



Anyway - another update. I figured what was causing the problems I was having yesterday, and I fixed it. I NOW HAVE AN R1 CALIPER ON THE REAR OF MY BIKE! And it works plenty strong enough to lock up the rear wheel...


The bracket is made from 5mm steel, as you can see I modified (cut) the standard bracket, so it isn't quite as thick. It's not all as neat as it could be, but it was my first attempt and it's holding up fine. I'm replacing the swingarm with one that has been powdercoated black soon, so it'll all be neatened up and presentable then.

[unfazed]

Would not say behind on content more like repeating what was already said.

Yes I have an FZS1000 one and R1 gold front ones.

My reason for changing was purely cosmetic and at £50 for a 10,000 mile old Fzs1000 Rear Caliper I decided to change it.

Now if I can get a gold spot one for the rear I will buy one and go back to having matching set again.

I also have a set of Gold R1 ones for the 1000 and it is for cosmetic reason, I just think they look better.

Making a bracket weaker is not a route I would take with brakes , but that is your choice.

[Lez72]

Making a bracket weaker is not a route I would take with brakes , but that is your choice.

+1

[Dave48]

Ok, so hopefully this will come up for people who search in the future - I have a new conclusion:


An early R1 caliper has 38mm pistons, the same as the stock FZS600 ones, so probably not much gain. If you could get it to work... BUT no matter what I did (I spent hours making a small bracket and fitting/bleeding it so it was 'perfect') it wouldn't work properly. My guess is that the master cylinder for the rear brake on an R1 is bigger than the FZS600 one as it simply wasn't pumping enough fluid, even after lots of bleeding, to get the pads to grip the disc properly.

So conclusion is: R1 rear calipers have been tried, but they don't work. What is next that people wonder about? XJR1300? :p

So how did you get round the hydraulics issue? Did you change the master cylinder? You mentioned difficulty with flow rate/piston travel.

[papercutout]

I'm not especially worried about the bracket guys - look how thick the aluminium is there, I've only taken it down by about 2mm (+ the 2mm 'bump' that is on top, and I've got 5mm steel in it's place). Most of the force will be through the front bolt, as that will hold it from being pulled backwards, the rear bolt will keep it lined up, and provide a bit of strength.


The hydraulics issue was being caused by the pads actually being sat funny, so that whenever the brake pedal was depressed it'd push the 'bottom' over, but not the 'top'. My brain wasn't tip top that day, so I noticed the problem, but not the cause. Yesterday I fixed that problem in about 5 minutes. It just needed a fresh pair of eyes!

So - there's no hydaulic problem. You just need to do a little chopping - up to you whether you do the bracket or the caliper, then make a very simple caliper bracket with 2 holes. Et voila! (I have a spare standard bracket here at home, and more 5mm steel, so I can easily remake it sometime, neater)