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 Post subject: Disc Rotors
PostPosted: Tue Feb 04, 2014 1:27 pm 
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Posts: 44
Location: Enfield, London
Hi - I've a disc rotor query that some of you chaps and chapettes may be able to answer.

Rotor size obviously matters to braking, but what about rotor brand/type?

I'll explain:

I've built up an old Kona HT - see pic below - which had mounts on the rear for the caliper to meet with a 140mm disc rotor. I found out after buying a set of Avid BB7 mechanical discs (how to operate hydraulics through one brake lever is a future question!) which came with a pair of 160mm rotor. So, I called every LBS to find a 140mm and the fifth shop I called had one. However, it was a crappy tektro heavy-as-heck chunk of metal. But, it was later afternoon and I wanted to ride the next day - that back brake was the last piece of the build to get this bike on the trail! So, I forked out (waitt for it) £22.95 for the rotor and got it on the bike. The issue - my front seems to grab on fine with the Avid 160mm rotor matched to the BB7 caliper. The rear is, well, crap! I've ordered a 140mm from Superstar to try it out (looks better, weighs just under 90gr and is half the price of the crappy tektro one!) but I'm wondering if the rotor (brand/type/material) makes that much difference??

The eagle-eyed among you will notice there's only one brake lever - I run both brakes into one dual-pull lever (necessity, not fashion or function!).

Thanks :)


[img][IMG]http://i1370.photobucket.com/albums/ag251/gturbett79UltraHound/KonaLD_Jan14_3_zps2f7b19f5.jpg[/img][/img]

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Last edited by UltraHound on Tue Feb 04, 2014 2:24 pm, edited 1 time in total.

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 Post subject: Re: Disc Rotors
PostPosted: Tue Feb 04, 2014 2:12 pm 
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Posts: 1335
Lots of questions here.

If it were me I'd ditch the 140's, they are a bit of an off size, the standard ones are 160, 180 and 203mm, the bigger the better braking power but they also add a bit of weight (but not much), you find a lot more choice in these sizes.

Most forks and frames can fit adpters to change sizes, from 160 to 203, etc..most frames and forks will take all sizes although with some the design means the max maybe 180, etc.

Mechnical brakes are notorioulsy pretty awfull, if you have poor braking performance its usually due to the hydrualic system, air in it or contaminated pads, etc..but that wont apply to you....I believe you can adjust mechanical ones but not sure.

Rotors dont vary much in construction, pads do..generally the softer normal pads or the harder 'metal' ones.


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 Post subject: Re: Disc Rotors
PostPosted: Tue Feb 04, 2014 6:22 pm 
Posts: 1694
Get some adapters dude £10 from superstar and every combo possible plus they do dirt cheap rotors


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 Post subject: Re: Disc Rotors
PostPosted: Tue Feb 04, 2014 6:47 pm 
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Posts: 44
Location: Enfield, London
Thanks, guys.

140 was standard rear size on xc bikes in early disc braking days, but seldom seen now, I know. Adaptors don't work - well, might if I used about 10mm spacing, which would look ridiculous and leave it open to greater likelihood of movement. It's a 2006 steel framed Kona and just doesn't like the adaptors - bought one of eBay (IS to IS as it's for the rear) and tried others in LBS; no joy. The 140mm, while not ideal, should be workable for the back and for xc type riding. It'll do...then I'll save the big brakes for the FS :)

I did order today a new 140mm rotor from superstar - just £13! So it'll be worth a shot.

Thanks

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 Post subject:
PostPosted: Wed Feb 05, 2014 8:19 am 
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Posts: 2082
Location: Southend
The rear brake should be smaller than the front and the majority of your braking should be done by the front so if you run a 160 or 180 up front that will complement the 140 out back. Never seen a dual pull lever. That scares me lol. If the brakes are shit they need a clean or a tune or just bedding I properly ?

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 Post subject: Re: Disc Rotors
PostPosted: Wed Feb 05, 2014 10:59 am 
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Posts: 1151
Location: Harold Wood
^^What Jon say's^^ Can be a pain setting up brakes that was not designed to run on that model bike! Ideally you want a 70,30 split as said more braking force to the front!, (70,30 being in your fingers lol) so maybe the the dual pull system is effective on the front as shorter cable ??? & longer rear cable (more stretch) & flex in the lever! I've never seen a pull system like that before maybe a crazy old skool system lol! Maybe worth looking into hydraulic set up, sold my avid 5's on ebay for £60 the lot! bracket wise Hope tech, Superstar Avid ect ! I run Hope M4'S with hope brackets & rotors but it does take a while adjusting & centralising the pads & rotors to get them spot on! once setup it transforms the feel in the lever well worth fine tuning! P.s nice Kona I used to have a Cinder Kone :thumbup:


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 Post subject: Re: Disc Rotors
PostPosted: Wed Feb 05, 2014 12:03 pm 
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Posts: 44
Location: Enfield, London
Thanks for the info, chaps.
The dual pull is because I can but only hang on withy left hand. :)
Tom Wheeler type brachial plexus (nerves from upper spine that control arms) injury, but it's more than 11yrs old now. The dual pull levers were designed for cycle polo.
I'll be going hydraulic with a thumb rear brake lever on a full sus - been talking with LBS about a build - but trying to keep this 1x9er as simple as poss. Getting a full sus built for marathon riding as the HT is fun, but quite harsh. My old full sus has been demoted to something for training my huskies! :)

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 Post subject: Re: Disc Rotors
PostPosted: Wed Feb 05, 2014 2:23 pm 
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Posts: 1151
Location: Harold Wood
Ok now I get it!, sorry to hear mate!, been looking at 1x10 setup for my next bike myself , should be all good as long as I choose the right chain ring&bash! Hydraulic setup would be ideal smoother operation & better bite! Kevlar pads!


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