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Technical & Reference Section => Tech and Restoration => Topic started by: Horseye on December 23, 2012, 03:41 PM

Title: Wheel size bungle?
Post by: Horseye on December 23, 2012, 03:41 PM: Hi ,

I picked up a pair of 20 x 1 3/8 Araya 7x for my Hutch build project. I'm surprised to see the diameter is considerably bigger than a "normal" 20x1.75 BMX wheel. I haven't got brakes etc yet but it looks like it might be difficult to make them fit because the wheels are so much taller.

Can anyone shed any light on this? Have I goofed in my naivety?!

Dan
Title: Re: Wheel size bungle?
Post by: GavinDavis on December 23, 2012, 03:46 PM: What do thy measure? Are you sure its not just an optical illusion due to how thin they are?
Title: Re: Wheel size bungle?
Post by: pkripster on December 23, 2012, 03:52 PM: He's got horse eyes lol
Title: Re: Wheel size bungle?
Post by: Jon The Bassist on December 23, 2012, 03:54 PM: Wheels measured in fractions (eg 1&1/8, 1&3/8) are different diameter to those measured in decimals (eg 1.5, 1.75").
Sheldon was the guru and explained it here: http://sheldonbrown.com/tire-sizing.html
Title: Re: Wheel size bungle?
Post by: AKGOFF on December 23, 2012, 06:06 PM: It's something along the lines of:

The thinner the rim (1 3/8 & 1 1/8) the bigger the diameter but also the 'depth' of the tyre decreases to compensate.

I think.

Adam
Title: Re: Wheel size bungle?
Post by: Horseye on December 23, 2012, 10:41 PM: They're definitely bigger. Jon the bassist / Sheldon Brown has the answer.

These wheels will fit in the frame and forks but I don't know how/if I'll manage to get the brake blocks aligned to the rim, they're about 2cm further out...

Thanks for your help and any more advice/tips welcome!

Dan
Title: Re: Wheel size bungle?
Post by: griff on December 23, 2012, 10:50 PM: Quote from: AKGOFF on December 23, 2012, 06:06 PM
It's something along the lines of:

The thinner the rim (1 3/8 & 1 1/8) the bigger the diameter but also the 'depth' of the tyre decreases to compensate.

I think.

Adam

The master of theoretical bike building has spoken :4_17_5:
Title: Re: Wheel size bungle?
Post by: GavinDavis on December 23, 2012, 10:58 PM: Quote from: Horseye on December 23, 2012, 10:41 PM
They're definitely bigger. Jon the bassist / Sheldon Brown has the answer.

These wheels will fit in the frame and forks but I don't know how/if I'll manage to get the brake blocks aligned to the rim, they're about 2cm further out...

Thanks for your help and any more advice/tips welcome!

Dan

You need mini brakes bud......like the smallers dia compe calipers :daumenhoch:
Title: Re: Wheel size bungle?
Post by: Jon The Bassist on December 23, 2012, 11:13 PM: My little bro no5, Hutch expert with 1 & 3/8 wheels:

(http://sphotos-a.ak.fbcdn.net/hphotos-ak-ash4/332272_10150996719015372_362596238_o.jpg)
Title: Re: Wheel size bungle?
Post by: pkripster on December 23, 2012, 11:19 PM: i know bungle he lives dwn my road
Title: Re: Wheel size bungle?
Post by: Pooch on December 23, 2012, 11:20 PM: Quote from: pkripster on December 23, 2012, 11:19 PM
i know bungle he lives dwn my road
zip it...!!!
Title: Re: Wheel size bungle?
Post by: T WILD on December 24, 2012, 09:54 PM: You need calipers off a racer/road bike
Title: Re: Wheel size bungle?
Post by: Andy68 on December 24, 2012, 10:25 PM: It's all about the rolling diameter with tyre = 20''. :daumenhoch: Little side wall on ya 3/8 tyres so rim diameter larger than ya 1.75 rims and so on.

You'll defo need shorter reach caliper, not sure which one tho, you'll have to measure. Plenty of Dia Compe, Weinmann 730's etc out there on ebay. :daumenhoch: