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Replacing rear drum brakes with motorbike disc setup - <650kg car
bennjamin - 10/6/16 at 01:58 AM

hey everyone

I have a small convertible which I am converting to a big motorbike engine - it comes standard drums front and rear.
Fronts will be something disc and custom - but I wonder about replacing the rears with motorbike discs for both alittle weight loss and why not.
Considering the car will have 160-180hp , and less than 650kg (depending if I run a partial roll bar etc) would some bigger front bike brakes be suitable ?

If so are there some well known kits made to suit BEC type builds ? I know of a KAD to suit minis - same sort of weight so might be an option.

I continue searching and researching and will update this thread too for future reference

many thanks Ben


britishtrident - 10/6/16 at 05:27 AM

A lot depends on weight distribution, old Mini racers of roughly the same weight most of which was on the front end used to run with almost zero rear braking, but when the static weight distribution has a rearward bias then 50-50 using the same sized discs and calipers is the usual starting point.

[Edited on 10/6/16 by britishtrident]


StevieB - 10/6/16 at 06:24 AM

If you're thinking of using motorbike discs, I don't think they'd be up to the job on a long term basis. Most 1000cc bikes use twin discs up front, on a bike weighing a damn sight less than a car - and the discs are usually fairly big too.

Wilwood calipers are pretty light and probably offer the best solution (similarly the KAD units you've already seen). If you're running as a road car, this would be the best option.

That said, drum brakes are pretty light and if you can run minifin drums, then that's probably the best lightweight solution IMHO.


bennjamin - 10/6/16 at 06:49 AM

Thanks for the replies guys

The Honda comes with alloy fin type drums on the rear standard - if it's all the easier I'll measure them and keep if OK. I am trying to use the entire rear as well.

Thanks for the info !

PS I'll update with another brake question soon thanks


ian.stewart - 10/6/16 at 07:08 AM

http://retrorides.proboards.com/thread/119012/1967-honda-s800-f20c


Ugg10 - 10/6/16 at 07:12 AM

If it is a road car then you may want to chech whether it needs a parking brake on the rear, don't know of any bike calipers that have a handbrebrake


nick205 - 10/6/16 at 12:53 PM

Personally I'd be inclined to use another road cars rear disk brakes to ensure you have a suitable handbrake system.


jambojeef - 10/6/16 at 04:13 PM

Ref:handbrake - Some bike calipers have two sets of pistons with separate fluid connections - the Dual CBS brake systems off Honda Blackbirds, VFRs etc have them and are cheap.

Means a hydraulic or hydro-mechanical hand brake can be designed and fabbed if needs be - I like the idea a lot and looked into it a bit.


Wadders - 10/6/16 at 06:27 PM

Have CBR600 discs on the rear of mine, no problems to report callipers are pug 106 for the handbrake. if it had been a track only car originally, i would have used bike callipers too for the weight saving.

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