Author Topic: rear caliper seals (Read 6730 times)

born to be mild · « **on:** 25 February 2012, 05:33:29 pm »

Hi All,
Im replacing the seals on my rear brake caliper, the main seal went in with a bit of a struggle but not too bad, the dust seal is a total pig to get in as it seems to be too big on its O.D. , being a tightfisted old bugger I bought what looked like reasonable aftermarket seals -Nikone 293800, certainly they seam to be the same as the old seals although its had to tell exactly. Does anyone have any tips on doing this job? Ive just spent an hour struggling with the dust seals and its still not in, Im tempted to put the old one back in at this rate.

Gnasher · « **Reply #1 on:** 25 February 2012, 06:12:46 pm »

First check the new seal against the old the diameter should be the same if anything the new one's will be slightly smaller, if the new one is bigger you've bought crap copies. You also state the main seal was difficult too providing you've thoroughly cleaned the rebates the new seals should go in with no problems at all if they dont something is wrong, if left they will grip the pstions giving you binding.

I never use pattern seals ever only OE.

born to be mild · « **Reply #2 on:** 25 February 2012, 07:27:38 pm »

Cheers Gnasher, hard to tell exactly but the new one looks to be the same size as the original. i cleaned the rebates with brake cleaner and an old toothbrush prior to trying to fit the new ones.

Gnasher · « **Reply #3 on:** 25 February 2012, 08:09:17 pm »

Have a good look in the rebates all the sides should flat and the corners perfect right angles, you tend to get oxidation build up on/in those areas any build up will stop the seal from seating.

His Dudeness · « **Reply #4 on:** 25 February 2012, 08:56:38 pm »

i had the same problem with cheap brake seals. had to buy yamaha ones in the end. i'd only buy genuine seals now

born to be mild · « **Reply #5 on:** 26 February 2012, 10:48:13 am »

cheers Your Dudeness and you too Gnasher, it looks like I'll have to splash the cash.

red98 · « **Reply #6 on:** 03 March 2012, 09:00:46 am »

have you tryed soaking the seals in brake fluid this sometimes helps...ive not done a fazer but its worked on lots of other seals..........

DryRob · « **Reply #7 on:** 03 March 2012, 02:10:39 pm »

Mine were abit tricky when I did the old 600 caliper so I ended up getting someone who was more patient than me to do it, they went in eventually

born to be mild · « **Reply #8 on:** 04 March 2012, 10:14:41 am »

Thanks guys, i did dip them in brake fluid first to ease them in, Ive ordered the Yamaha ones now.

born to be mild · « **Reply #9 on:** 10 March 2012, 10:05:51 pm »

Post script to the above, the Yamaha seals slotted almost straight in, lesson learnt there. By the way, I got them from Padgetts mail order, not too dear and good service. Sadly after swapping the seals, the brake fluid, polishing and regreasing the pad pins Ive still got crap brakes on the back with a half mile of pedal travel. Back to square one, bleeding the caliper every hundred miles or so.
Such is life, dear reader........

Fazerider · « **Reply #10 on:** 11 March 2012, 01:01:42 am »

Did you replace the seals in the master cylinder too, or just the caliper?
Is the disc good? Any visible runout will push the pads back further resulting in excessive lever travel.

UG · « **Reply #11 on:** 11 March 2012, 06:57:21 am »

Have you tired WEMOTO, I used them to rebuild a set of GSXR750 front calipers and they were half the price of a main dealer.

born to be mild · « **Reply #12 on:** 11 March 2012, 04:18:41 pm »

Hi Fazer Rider, I didnt do the MC seals as last year I found that I could temporarilly fix the problem by bleeding the brakes,hence my theory that the fault was with the caliper. The MC seals went on my other bike resulting in no brake at all whereas at the moment I have braking but lots of pedal travel. i havent tried it on the road yet but I dont think that the disc is at fault as the clearance between disc and pad on the side that I can see is constant as I turn the wheel.

Gnasher · « **Reply #13 on:** 11 March 2012, 05:34:15 pm »

Quote from: born to be mild on 11 March 2012, 04:18:41 pm

whereas at the moment I have braking but lots of pedal travel.

Providing you fitted the seals correctly and made sure the small seal/washer that goes between the caliper half's is both present and correct fitted your problem is it's air matey good old air in the system. On a standard rear there are two bleed nipples, bleed the inner first then the outer the rear caliper are normally very easy to bleed, if you're doing everything correctly and still cant get a result strip it and rebuild it again.

born to be mild · « **Reply #14 on:** 11 March 2012, 10:49:20 pm »

Cheers Gnasher, I didnt disturb the caliper half seal, you dont see them advertised much so Im guessing that they dont fail often, I didnt realise that there's a sequence to which nipple to bleed first so I'll give that a go.

Gnasher · « **Reply #15 on:** 11 March 2012, 11:01:20 pm »

Make sure you push the pistons right back then start bleeding.

born to be mild · « **Reply #16 on:** 12 March 2012, 08:57:51 am »

thats something else that I didnt know about so thanks very much.

janner_10 · « **Reply #17 on:** 13 March 2012, 11:23:33 pm »

Be interested to see how you get on - im having the same pedal travel problem after rebuilding my rear caliper last weekend.

born to be mild · « **Reply #18 on:** 21 March 2012, 09:08:29 pm »

Postscript to the above for anyone doing this job, incl you Janner, heres what I found out in my adventures in brakeland;
Dont use non OEM seals, even the mid priced ones like I tried, they dont even go in properly so forget them working for any length of time, the Yam ones went in a treat, cost £25 as oopsed to £7, but seven quid wasted.
I used a syringe to refill the system, fill the resevoir to min level then pump it in via the bleed nipples, when you stop getting bubbles in the res', start sucking out with the syringe on the nipples instead constantly topping the res' up,,dont let it run out !!!, [ cheers Gnasher for the tip about doing the inner nipple first ] .dont crack the nipples open too far, Ive a theory that they suck air in along their threads. When the rate of bubbles starts to slow give the caliper a tap to dislodge any air pockets, not as daft as it sounds, I got a bit more air out like this, then when your pedal is getting firmer but youre still getting air out, probably mainly from the threads or around the bleed hose/nipple surface, not genuinly from the system, stop using the syringe to suck, with the syringe and hose still attached just push the pedal down, slacken the nipple -tighten the nipple-let go of the pedal several times til by this point the system should be bled and no more bubbles. Oh happy happy happy feeling playmates !
Lastly, adjust the pedal position properly, doesnt affect the length of travel, I know, but when its positioned right it feels like theres less travel.
And that, boys and girls is my experience of resealing the mediocre back brake. I got mine finished tonight and it feels tons better, lets hope it stays that way. I hope that this helps anyone who like me isnt an expert.Thanks to all on the forum as ever who've chipped in with suggestions, Im pleased with how its turned out and enjoyed doing it, well, most of the time..

Fazerider · « **Reply #19 on:** 22 March 2012, 10:20:52 am »

I had a similar problem: miles of pedal travel which I took to be one of the seals in the master cylinder failing rather than air in the system because the brake did feel firm once the lever had moved about 2".. not that spongy feeling air gives.
Bought a bunch of other stuff from my dealer at the same time so have only just noticed he stung me £48 for the Yamaha seal kit.

Anyway, it did the trick in my case. Though I discovered I couldn't bleed all the air out of the master cylinder with it mounted on the bike... you need to be able to tip it from side to side and tap it to shift all the bubbles to the top. Loosen the banjo on the top of the cylinder to let them escape rather than trying to pump them down to the caliper.

janner_10 · « **Reply #20 on:** 27 March 2012, 11:22:08 pm »

Thanks for all your info Born - tried all your tips to no avail. In the end I brought a recon'd rear master cylinder from ebay for £12 - back break is bloody perfect now.

(The tell tale sign for me was the lack of a little woosh of fluid into the reservoir when the pedal was depressed)

unfazed · « **Reply #21 on:** 28 March 2012, 12:55:03 am »

Fit a Fzs 1000 rear caliper (01 to 05 model) and problem solved. Never had an issue with the rear brake since fitting it, looks better also

DryRob · « **Reply #22 on:** 28 March 2012, 05:03:48 pm »

This trick with bleeding at the banjos, does it compromise the seal that the crush washers make?

Fazerider · « **Reply #23 on:** 28 March 2012, 08:11:23 pm »

Quote from: DryRob on 28 March 2012, 05:03:48 pm

This trick with bleeding at the banjos, does it compromise the seal that the crush washers make?

It's not something I do unless I've had the banjo off completely, but I've never had a problem re-using the copper washers. Just make sure you don't get dirt under them. So long as the area is clean and the surfaces are undamaged they reseal fine. The tiny deformation they undergo when the banjo is nipped up isn't enough to work harden them.

bikemad62 · « **Reply #24 on:** 17 April 2012, 07:53:36 am »

I got a couple of usefull tips from a main dealer mechanic for the seal problem (1 )Use rubber grease on the seals when fitting the grease sits in the gaps topping the crud building up and the pistons slide in dead easy. (2) is a cleaning tool get an old pushbike spoke sharpen the end then bend it close to the end and this makes an awesome cleaning tool for the seal slots. Bend the other end into a handle.and buy good seals not cheap ebay ones.