Cibbersicks Posted February 20, 2014 Report Share Posted February 20, 2014 Without going into too much detail about what I'm up to, what would the ideal tolerance be for the bobbins on a FULLY floating disc brake? The rattly type For example, I would have thought 0.5mm on diameter would be ok, as that's only 0.25 on the radius of the bobbins? The steels do move a fair bit on the carriers don't they? Tom EDIOT: Beg y'pardon. Completely cocked up what I meant I don't mean diameter - I mean the tolerance laterally in terms of how much the steel can move side to side on the carrier. Tolerance on diameter should be around 0.2 I believe Link to comment Share on other sites More sharing options...
thefatman Posted February 20, 2014 Report Share Posted February 20, 2014 I've a set of PFM's on my vfr, loads side to side is the answer, none front to back is the important bit. Link to comment Share on other sites More sharing options...
Cibbersicks Posted February 20, 2014 Author Report Share Posted February 20, 2014 Yeah that's what I meant but it came out wrong in my first bit haha! Specifically, how much is loads side to side, in MM? Link to comment Share on other sites More sharing options...
Evilchicken0 Posted February 20, 2014 Report Share Posted February 20, 2014 Depends on the spring washer ... If they rattle, but have front to back movement then the spring washers hve got flattened. Get the spring washers and circlips replaced and they won't rattle. They still need to be in the middle of the caliper though. Link to comment Share on other sites More sharing options...
Cibbersicks Posted February 20, 2014 Author Report Share Posted February 20, 2014 I'm talking about proper race discs sorry, I don't think they have spring washers one there. Proper race discs rattle like fuck Link to comment Share on other sites More sharing options...
Bungle Posted February 20, 2014 Report Share Posted February 20, 2014 I'm talking about proper race discs sorry, I don't think they have spring washers one there. Proper race discs rattle like fuck I have a pair of fully floating Brembo cast iron discs on one of my bikes & the mot man said they were a fail due to ANY movement. I explained they are designed to have lots of side play due to expansion as they were not stainless. It took some getting through to him but he passed it in the end. This might not have answered your original question, but mine have been fitted with new spring washers & bobbins & they still move & rattle like fu*k. Link to comment Share on other sites More sharing options...
Cibbersicks Posted February 20, 2014 Author Report Share Posted February 20, 2014 Could you have a quick look and see how many mm they move side to side please? My race Nissins are the same but I want to get an average measurement Link to comment Share on other sites More sharing options...
Bungle Posted February 20, 2014 Report Share Posted February 20, 2014 Could you have a quick look and see how many mm they move side to side please? My race Nissins are the same but I want to get an average measurement My bike is away at the moment, but I will be paying it a visit over the weekend & will take a measure. I do know though that they move a lot when they are cold. Link to comment Share on other sites More sharing options...
YZ faybo Posted February 20, 2014 Report Share Posted February 20, 2014 My brembo sbk's have 1.2mm play on the inside and .7mm on the outside surface and are quite new. Hope this helps. Link to comment Share on other sites More sharing options...
Cibbersicks Posted February 20, 2014 Author Report Share Posted February 20, 2014 Lovely stuff that's just what I need cheers Oh how thick are your washers please? Link to comment Share on other sites More sharing options...
dansp1 Posted February 20, 2014 Report Share Posted February 20, 2014 I have a pair of fully floating Brembo cast iron discs on one of my bikes & the mot man said they were a fail due to ANY movement. I explained they are designed to have lots of side play due to expansion as they were not stainless. It took some getting through to him but he passed it in the end. This might not have answered your original question, but mine have been fitted with new spring washers & bobbins & they still move & rattle like fu*k. Fully floating brake discs are designed to have some movement. Care must be taken to not unnecessarily fail these items for security. That is what the mot regs say. my ISR full floaters have loads of movement side to side (but none rotationally) Link to comment Share on other sites More sharing options...
Evilchicken0 Posted February 20, 2014 Report Share Posted February 20, 2014 Fully floating brake discs are designed to have some movement. Care must be taken to not unnecessarily fail these items for security. That is what the mot regs say. my ISR full floaters have loads of movement side to side (but none rotationally) It says in the MOT testers online manual about fully floating discs. I have the Brembos iron rich discs too. Link to comment Share on other sites More sharing options...
Mark/Foggy Posted February 20, 2014 Report Share Posted February 20, 2014 You're not going on the road Tom, so won't be an issue for you. Answer, 'cause I'm assuming that you're thinking rears - is anything that you think you can get away with. I'd stop at 2mm float i.e. 1mm off centre line. This does of course make getting the alignment of your disc central in the first place - difficult, so you need access to loads of shim material and patience. Pack the disc central in the disc bobbins and then shim the caliper off the hanger until you're exactly right. From then on you should find that the disc will 'centre' on the bobbins as it gets some speed up (general principle of vertically orientated rotating objects is to centre, think gearboxes are on horizontal shafts for a good reason). Rattle in the paddock, silent on the move. Assuming that the caliper is clean and square to the axle, you should be alright. You'll go through disc bobbins though, and it's probably worth putting a dab of epoxy on the circlip eye holes, binding to a plain shim washer underneath for a hint of security. QD rear is it Tom? Link to comment Share on other sites More sharing options...
Cibbersicks Posted February 20, 2014 Author Report Share Posted February 20, 2014 Thanks Mark, Yep it is for a rear. I'm considering getting a disc made to my spec and I'm having a go at designing the whole thing. Got everything done apart from the bobbins so that's why I wanted to know about the correct sort of tolerances. At the moment the flat disk (Braking wave) is perfectly central and square to the caliper due to the hanger I've had made. As long as the disc is made to the same dimensions as the Braking one centralisation should be fine. I'll take a bobbin out of my front disk and take some measurements. Not full QD yet, will be though soon. Link to comment Share on other sites More sharing options...
Mark/Foggy Posted February 20, 2014 Report Share Posted February 20, 2014 Bobbin material choice here could be key. I'm going on what Spondon were doing an age ago and the knowledge base is now shafted. You're certainly gonna have to make sure that the radiuses chosen particularly where the rim meets the hat, are compatible with the chamfer on the disc. Detailing of the circlip slot are gonna be critical as well. Not a job for an amateur. I'm thinking you'll be into 7075 with a post machine temper to get it into T6 plus condition. Off the shelf bobbins are sure to be easier. In truth I'd go direct to Yari at ISR or check out Beringer for something that'll work. Both should swallow a .DWG and come up with something quickly and you'll save yourself a world of potential pain. Both options trick and slightly unusual, both able to supply colorways, material choice and unusual bobbin solutions if you want to avoid re-engineering a wheel to suit a Brembo or Nissin race disc. Link to comment Share on other sites More sharing options...
YZ faybo Posted February 21, 2014 Report Share Posted February 21, 2014 My circlips are 1.2mm thick and two thin steel washers at .7mm together. I have a tiny blob of araldite holding the circlip to the washers but not any other surface to reduce them spinning to much without hindering side movement. Hope this helps. All parts are brembo. Let me know if you need the carrier thickness. Link to comment Share on other sites More sharing options...
Farmfab01 Posted February 21, 2014 Report Share Posted February 21, 2014 I bought a set of used CBR 929/954 PFM front brake discs from ebay for my Daytona 955 race bike & they have around 0.75mm forward/back play, I was concerned at this so I rang West Performance (the manufacturer) who insisted this was ok with their tang/slot/circlip disc design, I think he said the limit was 1.5mm with the PFM design but I'd need to check. Edited to add - you can't have play like this on bobbin type Discs Link to comment Share on other sites More sharing options...
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