CF Front Brake Caliper Adapter

I'm upgrading the front brake on my Mk3 to a 12" floater and a 4 piston Tokiko caliper off a GSXR 600. I'd like to have a Carbon Fiber adapter made instead of the usual 1/4" aluminum. I'm wondering how much thinner I can safely go. I've read that CF is 20% stronger (shear or pull strength) but most of the force on the adapter is compression, yes? Would resistance to forces be the same in both directions? 1/4" less 20% is 1/5" or could you go 3/16" or even 5/32"? And how much resistance to torsional forces are needed? I intend for the adapter to have a U shape cross section so that should make it very resistant to twisting forces. Finally does anyone know a fabricator for this, and what kind of cost should I expect?

Thanks for your help.

Ridedrms

hehehe bet this idea has cost some restlessness trying to get to sleep. See if CF being used on moderns and what features they have to avoid delamination, vibration loading on fastening points fragmentation, brake fluid tolerance with sufficient reserves built in to still be worth whiile for a few oz saved. I'd think after you find someone willing to take legal risk to supply a road going vital item or equip for DIY - a one off could run into some grands of money digits.

You can buy CF sheet in reasonable thickness but have never heard of caliper adapters made out of CF in general. :shock:
Titanium would be up to the task.

jneale828 said:

I'm upgrading the front brake on my Mk3 to a 12" floater and a 4 piston Tokiko caliper off a GSXR 600. I'd like to have a Carbon Fiber adapter made instead of the usual 1/4" aluminum. I'm wondering how much thinner I can safely go. I've read that CF is 20% stronger (shear or pull strength) but most of the force on the adapter is compression, yes? Would resistance to forces be the same in both directions? 1/4" less 20% is 1/5" or could you go 3/16" or even 5/32"? And how much resistance to torsional forces are needed? I intend for the adapter to have a U shape cross section so that should make it very resistant to twisting forces. Finally does anyone know a fabricator for this, and what kind of cost should I expect?

Thanks for your help.

Ridedrms

Click to expand...

I wouldn't do that.

Carbon fibre itself may well be as strong as you've described, but its the resin that creates the sheet that would most likely crack and weaken and lead to de-lamination in such a stressful environment.

I've used carbon fibre sheet for all sorts, inc footrest hangers and engine mounts in the past, but I'd never use it for brake mounts, its simply not worth it, failure will likely result in death!

If its weight saving you're after, stick with alloy or titanium, design carefully and mill / drill holes.

If its looks yours after, still do the above, then get them carbon 'wrapped'. I've never done it myself as is a bit too 'false' (making something look like something it is not) but it does look the part if that's your thing.

MK3 adaptor would be in tension, not compression, on the front which makes the idea of using CF a strange one, as it is better to compress material. Also, if the Tokico pistons are different diameter, the caliper will need to lead with the the correct diameter pistons - it would still work, but here in the UK would be a big issue with insurance if involved in a serious accident if found to be fitted incorrectly.
If CF fails, they you may not get a second chance, as I'm pretty sure the front wheel will stop in one rotation.

About the lightest safest way w/o being an experimental sacrifice like prior new materials experiments in air craft with tails falling off over oceans, might be to weld on a plate of alloy [with brake fitted and locked on rotor for perfect alignment then sculpt it back to pretty. I used 7757 TS plate on Peel as its a lot harder tougher and somewhat heavier than 6160 TS ya don't need very much and I figured it'd resist wallowing out of mount holes over time and loads. Frames and swing arms and forks made of CF have bushes and plates and other hard points cast in to take shock-vibe loads locally and not splinter carbon back to fuzz. Ti is tricky to weld and drill and machine and not weldable to Al so would need a couple extra fasteners adding back some of the lightness lost. Seat pans, fairing and covers are a no brainer CF use to loose a few more oz to lift up on drops.

Thank you all for your responses. Had not considered vibration leading to delamination of the bracket. Embedded metal bores would make a lot of sense, but would mean more complexity and weight, No wonder no one does it. Back to the drawing board. Alloy will do just fine. Thanks for the tip on the different alloys available.

Ridedrms

I see rusted spokes on brake hub side so we know caliper can get dang hot so another factor on how much cooking cycles the CF resin should stand. Would definitely have to be floating rotor as side flexture is not a strong point of any composite built light enough to gain something. Like they say in many sports, if ya an't falling crashing now and then then ya just ain't really trying, same with many new ideas. I'd bet ya could make a mount out of JBWeld by golly but its steel filled so alloy likely lighter and prettier. So would sheet metal Ti yokes or CF yokes float higher in water?