How to find out about my front end

[breakaway]

Here's a pic from the top:



I think those are adjusters?

[MSTRS:Me]

Sure are. The smaller hex nut adjusts spring preload. The round 'shaft' in the centre adjusts rebound damping. At the bottom of the fork leg at the rear below the caliper will be a screw that adjusts compression damping.

[vifferman]

Also, is there a way to test at home which (or if both) discs are warped. Prefrably without actually taking off the disc(s)

A crude way is to jack the front of the bike up, and spin the front wheel while holding a permanent marker pen close to the disk. Any wiggles will result in the runout being marked by the pen. I used this method with great success to mark my VF500's front disks, then straightened them using a combination of replacing spacers behind the mounting points (VF disks are not the floating kind with buttons, as yours are), and leaning on the disk with a big crescent.

But I'm sure any bike shop will measure runout for you with a dial gauge for a very few shekels - it's not a huge job. They essentially do the same thing as my 'marker pen' method, but use a runout gauge which touches the disk while it spins and measures lateral movement.

[breakaway]

So I drew on the discs with a florescent highlighter and rocked the bike back and forth - it resulted in the lines getting wiped out on both the sides. WTF?

Right Disc
Before:

After


Left Disc
Before:

After:


This doesn't look good

So what is the next step? Check for seized pistons etc? How do I go about fixing this? Also, I've sourced some new discs, and if need be I can purchase them.

Any help appreciated

[Mental Trousers]

Can't tell from those pics but I'm guessing there's some lines showing after you gave the discs a spin?? I've had warped discs before and didn't matter what we did they'd always warped again when I got them hot so I replaced them with some EBC wavies.

Go to http://www.goldfren.cz/catalog.htm and have a look at the brake pads catalog. If you print out pages that look similar to the pads in your bike onto A4 paper the pictures of the pads are the exact size of the real thing. So you can lay your current pads on the picture to find the exact pad. Then have a look at the list for the pads to see what bike the calipers probably came off.

Looks like you've got the disc nailed but you can check it against a parts fiche. Goto http://www.ronniesmailorder.com/fiche_select.asp pop in the details for a tri-arm and then take a look at the parts diagram for the front disks. That'll show you the bolt pattern etc so you can confirm it really is off a tri-arm.

If it definitely is off a tri-arm you can use the brake disc catalog to at http://www.goldfren.cz/catalog.htm to find out which bikes use will accept the same disc. Shouldn't be too many with upside downers in that list eh.

[breakaway]

Can't tell from those pics but I'm guessing there's some lines showing after you gave the discs a spin??

Nope, there isn't, that's what's worrying me. On the right disc, all the lines got wiped off. But on the left disc, they got a bit smudged. I presume the lines should be intact on both sides if the discs weren't warped?

These are new pads, but I've had them for about 400km now, and they should be worn in. I have noticed that the front right disc is warm after I bring the bike to a stop only using the rear brake. I'm SURE that one is grabbing / warped / whatever. But as in the photos, the lines got wiped from both sides so it has me a bit worried.

When I went to get new pads, I went to the shop and told the guy there about how my front end is all random, and he brought out several pads and matched them against the outside of the caliper, and said that's it. So I got a pair, and we went to put them in a couple days later, and to my surprise they were smaller than the ones we had taken out - about 80% the size. Howver it was decided by my experienced friend that it would be alright to put in the pads. (See pics below)

What we removed:


What we put in:


Could it be that the piston isn't retracting properly or something because the amount of surface area that it has to push on isn't as much? However that doesn't make much sense since it's only happening on one side.

What I want to know: Why are the lines getting rubbed off? Something is definitely up here. What could it be? Seized calipers? Warped discs? Combination of both?

[Mental Trousers]

1st thing to do is seals. Doesn't seem to be warped discs if the lines are wiped out/smudged evenly all the way around. Warped discs leave some lines and wipe out others. But if 1 disc is warm when you haven't used the front brakes then it's most like the pistons aren't retracting properly cos the caliper needs a damn good clean out.

[breakaway]

But if 1 disc is warm when you haven't used the front brakes then it's most like the pistons aren't retracting properly cos the caliper needs a damn good clean out.

Requesting instructions

[Grub]

I have another observation altogether about how the bike is sitting. Does it feel twitchy and prone to oversteer? It looks extremely head-down. While that might look cool, it is probably seriously fing up your handling.

[Mental Trousers]

Requesting instructions

Get someone who knows what they're doing to show you.

[breakaway]

I have another observation altogether about how the bike is sitting. Does it feel twitchy and prone to oversteer? It looks extremely head-down. While that might look cool, it is probably seriously fing up your handling.

It feels alright, but I might have gotten used to it :\

Other people who have ridden it have told me that it 'feels wrong' though.

Could you please elaborate "Head Down"?

[Grub]

Could you please elaborate "Head Down"?

From my recent reading about suspension and setups, the bike is designed to sit fairly level. If the arse is higher than the back, they are unstable and twitchy and at the extreme end, prone to tank-slappers.

Then there's all the stuff Honda spent years in R&D like preload, rebound and compression rates. With a new front end that looks as low as yours I'd guess that none of those things are right on your bike.

Here's a few links that might help to explain it all
http://cbrworld.net/forums/thread/856.aspx
http://www.sportrider.com/bikes/146_...ngs/index.html
http://bikershangout.net/forums/showthread.php?t=5376
http://www.bikersoracle.com/cbr600/f...hread.php?t=34
http://www.kgrant.co.uk/Per_Handling2.htm
http://www.gostar-racing.com/club/mo...ion_set-up.htm


There's some really good stuff there.

[riffer]

I've just had a look at the pics you've posted here.

The brake calipers are definitely the same as the RF900R so any pads specified for that bike will be the right ones.

Another point - on the RF900R the brake pads have shims on the back edge to help with getting the pads to seat properly against the disk.

You don't look like you have those shims on. Small point I know and its probably nothing but I'll mention it anyway - it could be a combination of no shims and incorrect brake pads (as in they hang a bit out of the caliper and don't get pushed evenly in by the pistons) could be creating a bit of a shudder at brake stage.