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Dawes Double Edge Brake Disc Size

Ian Lewis2021-03-28 10:44:48

Hello, would anyone with a Double Edge to hand be able to tell me the diameter of the brake discs, please?

We have a 2009 Discovery Twin with the same frame and disc hubs, and am considering converting it to disc (as it presently has the drawbacks in terms of dishing etc, but none of the advantages).

Many thanks.

Giles Bresnen2021-03-28 11:14:17

Hi Ian,  we have a 2012 discovery twin. We have a 200mm disc on the back and a 180mm on the front. I think you can fit any size disc as long as you get the right caliper post adapter for the front and rear.. 

Vernon Hunt 2021-03-28 11:16:13

Hi Ian, 

The rotor size depends on the adaptor mount, I have 203mm fitted currently, front and rear.

Certainly wouldn't go any smaller, in fact I'm considering increasing but stock on larger rotors is limited.

Hope this helps.


Giles Bresnen2021-03-28 11:22:00

Shimano SA-MA-R203 P/S is the mount we have on the rear for 203mm disc, no number on the front.

Ian Lewis2021-03-28 11:46:17

Thank you both, I had a spare caliper, 180mm disc and mount and they clearly fit OK, just wondered how much larger you can go.

My one other disc bike, a Surly Straggler, only has clearance for 160mm discs, so wanted to know in advance what definitely fits before trying to source parts.


Christopher Boocock2021-03-28 12:26:38

HI Ian

I upgraded my brother in law's Discovery Twin with these parts from CRC last May:

LifeLine Essential Inner Brake Cable - Tandem
Tandem -  sku566949
Quantity: 1  
    Subtotal:    £102.37

Shipping to  
United Kingdom:     Free

Total:    £102.37

You saved:     23% (£30.06)

Shimano RT66 Disc Rotor (6 Bolt)
Silver, 203mm,  -  sku319053
RRP  £24.99 | Saved  20%
Quantity: 2  (Subtotal:  £40.00)
Shimano M375 Disc Brake Caliper
Black, Cable Operated -  sku693684
RRP  £29.99 | Saved  23%
Quantity: 2  (Subtotal:  £45.98)

Shimano Mount Adaptor Rear Post to IS
Black, 203mm -  sku41260
RRP  £9.99 | Saved  30%
Quantity: 1  

Shimano Mount Adaptor Front Post to IS
Black, Front 203mm,  -  sku38589
RRP  £9.99 | Saved  30%
Quantity: 1  

From memory it was straighforward other then fitting rack and mudguard mounts around the rear caliper. I had to extend and swap cable outers too. Worthwhile upgrade. Not sure if larger discs would fit - I think the rear was close to the frame. If you need more stopping power then perhaps other cable calipers are worth a look. Off road, my wife and I have the Shimano Ice Tech 203mm rotors to help brake recovery. The previous Formula steel rotors would warp.

Hope it goes well.

Chris :-)

Bob Gairns2021-03-28 12:46:48

We have a Discovery Twin of similar vintage and I recently upgraded the Rear 203mm Avid disc system to Spyre dual cylinder cable brakes and fitted the Avid to the front. It wasn’t totally straight forward as the post mount needed filing down to get the required clearances and I had to get very creative to refit the mudguard on the caliper side-plastic spacer ex. Sewing thread reel. The rear upgrade was a straight swap with no fit issues. Bob

Ian Lewis2021-03-28 12:56:24

That's useful Chris, thanks - I built 2 solos from framesets in 2017/2018, and looking at the price of parts now compared to then surprise... so all of that worked fine with the standard combined shifter/brake levers?


Bob, out of interest how does the Spyre compare to the Avid For braking power? Both seem to have their proponents, my one disc brake bike has hydraulic Tektro calipers so I have no experience of either.

Christopher Boocock2021-03-28 13:32:45

Hi Ian - yes, all that worked fine with the original shifters and brake levers. I can't remember exact year of tandem or shifter and lever models but I can check if necessary.

FWIW on Emma and I's road Cannondale we have Avid BB7 and 203mm rotors and they work well. We are about a 160kg all up weight and ride ups and downs of Sussex. Not done laden touring with alpine length descents though. In the distant past I rode Peugeot tandem on alpine roads with rim brakes and rear drum. Worked fine so long as we kept braking distances long and didn't let speed get too wild. Discs definitely have the greater stopping power - especially in the wet. For offroad, I've got a pair of 4pot Zee calipers waiting to go on the mtb tandem which will take Shimano finned pads - very conscious of not wanting to lose brakes or warp a disc when two up!

Bob Gairns2021-03-28 16:27:38

Ian- the Spyre is a better all round brake than the Avid as it pushes the pads from both sides. Much easier to stop it rubbing which is a constant feature of the Avid single cylinder which relies on the single piston to push the pad onto one side of the disc and then the whole thing onto the other static pad. Having had Hayes hydraulic brakes on our mountain bikes for years there is no comparison really but the Spyre is as close as you can get on a cable system. I have yet to change to compressionless cable outers  and an upgraded inner cable however they are on the list of things to do and are in the workshop. The  long route to the rear caliper and the separate cable outer sections makes me suspect it won’t make a huge difference but that is what I was recommended to do by a fellow club member when I upgraded our wheels to shiny black versions that would look naff if I scored the rims with traditional brakes.

Lawrence McPhillips2021-03-28 17:45:56

I'd second the view that the Spyre is a good brake.  I replaced a single piston Tektro Lyra caliper with a twin piston Spyke and the improvement was not subtle.  Once adjusted, the pads stay in 'synch' with each other and give very good stopping power for quite light lever pressure.

It is worth spending a bit of time getting the cable routeing spot-on and as friction free as possible for best performance.



Christopher Boocock2021-03-28 17:46:18

Hi Bob - our Avid's haven't rubbed at all. It's a while since I serviced them but I've been impressed at how well the single piston design works. Ours has the red fine adjust knob on it. Re: outers: Not sure which ones you mean but I recall a long time ago being cautioned against advice to switch to gear style outers for braking as they can split lengthwise under high brake cable tension.

Bob Gairns2021-03-28 18:13:10

Chris- I have these cable outers to fit so they should be ok. 


I can get the Avid to run free with the said red adjuster but it needed constant attention to maintain brake performance and once I saw the twin piston system there was no going back. 


Christopher Boocock2021-03-28 19:06:41

Thanks Bob - link appreciated! Interesting looking set - when you've got them fitted, please let us know how they perform and what the lengths are as supplied. Thanks :-)