david knight
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| posted on 8/8/12 at 10:48 PM |
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Lightweight and cheap Cortina discs and calipers?
I’m building a lightweight single seater car (appox. 300-400kg). I’m going to use alloy uprights and hubs. However I don’t want to use the Wilwood
Powerlite 4-Pot and Cortina disc as I think this is over enginering the braking system for such a little car and because it’s going to cost an arm and
a leg to go down that route.
My research so far shows that a Cortina disc weighs 4.05kg and the walwood callipers are about 1kg each
Cortina disc :
http://bremboaftermarket.com/En/Car_Disc_Catalogue/Catalogue_Detail_Image.aspx?Code=c208f082-2e3b-4431-8a74-4e803749ed21
I’d like to use a Mk1 Escort disc these weigh 2.3kg and the callipers look quite light but the disc is not designed to mount onto a Cortina hub. the
bolt hole diameter (PCD) is larger and the inside radius that the hub fits into is smaller.
Escort Disc:
http://bremboaftermarket.com/En/Car_Disc_Catalogue/Catalogue_Detail_Image.aspx?Code=0ffa6de5-38cd-4ec6-aab8-5c560673d15b
Has anyone heard or know of a way to fit these discs to these hubs?
Could I get an escort Mk1 alloy hub with this disc PCD that fits onto a Cortina stub axle?
How hard / expensive would it be to get the escort discs drilled with new holes and the centre opening enlarged? Sounds like a quick job on a big
lathe.
1 option I have considered is using a mazda 121 disc:
http://bremboaftermarket.com/En/Car_Disc_Catalogue/Catalogue_Detail_Image.aspx?Code=ed763ed8-027a-4b0a-9ae4-cab65aa7459d
these weigh 3kg and have a PCD of 94mm this is 1.54mm larger than the Cortina. Could this be adjusted to fit with a file? Thats only about ¾ of mm on
each bolt hole.
Dose the centre opening have to fit tight against the hub? in this option there would be a gap (i cant see any recess on the alloy hub to take the
discs). I’m not sure this option is worth it for a 1kg saving on the disc
DRD racing make grass buggies that use 4 pot callipers off a CBR1000rr bikes on their own 5mm custom discs. I suspect this is good enough to get you
out of trouble when drifting around a 400m ovel circuit but no good for a road application. Would be fantastically light and cheap though, discs are
£8 each and a set of callipers on ebay are £100
am is missing something obvious, are there smaller lighter discs options for the Cortina hub for a reasonably priced?
Also, any thoughts on light weight calipers?
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matt_gsxr
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| posted on 9/8/12 at 07:32 AM |
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Not sure on the answers here. Lots of people have considered, prototyped motorcycle calipers for car applications but I am not sure how many have
actually made it to the road. It is one of those areas where you can't afford to get it wrong. Also the packaging inside a 13inch wheel can be
tricky as the bike disks are often large diameter.
The links to the bremo site are awesome, lots of great information there. Have you considered pug disks? those guys really like to keep unsprung
weight down, mounted from the wheel bolts (same spacing as Ford). I haven't used them but they might be an option.
http://bremboaftermarket.com/En/Car_Disc_Catalogue/Catalogue_Detail_Image.aspx?Code=56a08a8f-75bb-4254-b09b-d0f3162e8122
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Wadders
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| posted on 9/8/12 at 08:35 AM |
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Why not just machine the cortina discs down to a suitable size, they are designed to stop a 1.5 tonne car and will have a big safety margin built in
on top. 300kg is really not much to stop.
Or for ultimate weight saving, machine up some ally bells and get the discs lazer cut.
Have a look round the hillclimb paddocks for inspiration, most of the single seaters will be a similar weight and are running big
slicks, yet the brakes are usually tiny.
Al.
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b14wrc
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| posted on 9/8/12 at 10:37 AM |
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Hi,
The Escort disc could be redrilled to fit the back of cortina hub. I redrilled a pug 406 283mm disc to fit on the back of the cortina hubs and
it's worked quite nicely. Managed to squeeze Brembo 4pots on and it all fits under a 15" rim. 
Rob
20vt powered rear engined locost
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MikeR
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| posted on 9/8/12 at 11:24 AM |
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I'd have thought that 300kg plus driver (so 400kg) is probably around the limit of a big touring bike (i'm thinking bike around 80kg, two
riders up to 100kg + margin of safety).
How close do you want to push it and if its not for the road ...... perhaps an option?
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MikeRJ
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| posted on 9/8/12 at 01:22 PM |
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A big touring bike (e.g. Triumph Trophy, Honda Pan European) will be heading towards 300kg without any riders! The really big lumps like a Goldwing
are over 400kg fueled up but with no rider or pillion.
A 50cc scooter probably weighs in at 80kg, but even the lightest 600cc sports bikes are around 160kg without a rider.
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gdp66
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| posted on 9/8/12 at 02:29 PM |
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Is this for a grand prix midget racing , as they tend to use self built uprights with motorcycle calipers.
or go and have a look at grass track cars.
or jedi's
http://www.gpmidgets.co.uk/
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iank
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| posted on 9/8/12 at 05:21 PM |
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If you don't need a handbrake radial motorbike calipers are ideal for rear brakes.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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david knight
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| posted on 9/8/12 at 06:14 PM |
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Thanks for the pointers. I will defiantly consider Peugeots disc. It’s also good to hear that someone else has drilled discs for new bolt geometries
and fitted to the back of a Cortina hub.
As for bikes I did look at the goldwing disc and callipers initially, as you quite rightly point out they are 400+kg bikes but their discs are much
bigger (in diameter) which would mean running the caliper on a smaller radius and I’m not sure what problems that could lead to. I think that if you
go for a smaller disc you need to make it thicker to dissipate the heat, I suspect that there is a limit to the size of disc you can fit into a bike
caliper. Bike stuff is also relatively expensive. When someone builds a successful kit with bike brakes on then I can see it becoming common practice
but until then I think I will keep clear!
I took the plunge and purchased some alloy Cortina uprights off ebay yesterday so I’m now committed to Cortina hubs. I was planning on using DRD
racing alloy hubs as they have both the 108 ford and more standard 100PCD wheel bolts holes. I phoned them today only to find out that the hub is
based on a Vauxhall viva (I had in my head for some reason that this was Cortina based). Bugger, they were also the best price!
I was planning on using lightweight mazda mx5 wheels as they are cheap and very light weight (4.8kg) can anyone recommend a good secondhand alloy
wheel using 108PCD (ford) wheels? I’m looking for 13 or 14 inch rims 5 to 6inchs wide
I would just like to add that this site is brilliant! You guys are a gold mine of information and advice.
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