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 Post subject: confused over bike sizes
PostPosted: Fri Mar 11, 2011 12:46 pm 
Dirt Disciple

Joined: Sun Mar 06, 2011 6:55 pm
Posts: 20
Location: CHESHIRE
Hi, can anyone offer some quick advice and help for a newbie please, I am looking to buy myself a bike I am 5'10" with inside leg of 30". Looked up on t'internet and most charts I have seen suggest a bike of 18 - 19" would be about right, yet I have seen bikes on here (same height owner) with much smaller frames sizes, but with the seats set very high above the handlebar height :shock: . so I am confused as to which is right and therefore what to look for, most riding will be weekend pleasure 50/50 road / trail and I think a hybrid or hardtail would be the sort of bike I should be looking for.
Can any of the more experienced offer some guidance

Thanks in advance
Normski.


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 Post subject:
PostPosted: Fri Mar 11, 2011 1:02 pm 
National & North West AEC
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Joined: Mon Nov 03, 2008 12:43 am
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Location: Macclesfield Forest
For mountain bikes I've always worked on the formula:

Inside leg measurement minus 12 to 13 inches equals frame size.

So for you that would be 30 - 12/13 = 18 or 17 inch frame.
(Frame size is generally the seat-tube measurement from the centre of the BB to the top of the seat-tube. There are some exceptions like GTs which are measured centre BB to centre Top Tube)

I've a leg measurement of 32 and ride my own bikes ranging from 19" to 17". In general I'll plump for 18" or 19", but some smaller frames seem to fit pretty well and offer greater stand-over height.. (My modern DMR is only 14").

Perhaps the more important measurement to consider though is effective top tube length or reach.
With an 18" frame for example, alot of older mountain bikes have relatively short top tubes of around 22", utilising a longer stem to stretch out the riding position. The more modern 'genesis geometry' favours a longer top tube, maybe 23" combined with a shorter stem. This compensates for the effect of longer forks on steering.

Obviously there is plenty of variation between manufacturers and models and the measurements above are approxiamations as a guideline.

I not recommend going for too small a frame with loads of seatpost hanging out of it. This will place extra stress on both the frame and the post, leading to potential failure.

So in short, go for a 17" or 18" frame.


Last edited by drystonepaul on Fri Mar 11, 2011 1:07 pm, edited 1 time in total.

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 Post subject:
PostPosted: Fri Mar 11, 2011 1:06 pm 
Retro Guru
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Joined: Thu Aug 06, 2009 5:48 pm
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If you're new to all this, it's probably best to size the bike by your body measurements, even better to go to a bike shop, get sized up and try a few out if you're able to do that. You'll find as you get used to riding different bikes, personal preference starts to come into play and that's why you'll see people riding smaller bikes than they "should" be riding. For example, I'm 5'11 with something like a 32" inside leg and I usually ride 17" frames, simply because I feel happier on a smaller frame.


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 Post subject:
PostPosted: Fri Mar 11, 2011 1:49 pm 
Gold Trader / PoTM Winner / RB Rider
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i have the same measurements as you and tend to ride 16-18" but as DSP says, reach is important too


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 Post subject:
PostPosted: Fri Mar 11, 2011 3:51 pm 
Gold Trader / MacRetro rider
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start with a 17/18" ,one of the first things to do when you
get a bike is to make it fit you so your comfy on it
contact points (saddles pedals bars/stem )are all a personal preferance thing

i'm 6' and ride 16"-23" frames


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 Post subject:
PostPosted: Tue Mar 15, 2011 2:48 am 
retrobike rider
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I'm about you height give or take an 1" I haven't measured myself recently enough to remeber. Inside leg is 32" and I ride a 16" as I like the shorter reach which creates a more relaxed position but also gives me around 5/6" of seat post showing which is about right if you want to be able to fit a rear light and mudgaurd in the winter. It also gives me a safe standover height with about 2/3" of clearance on my crotch.


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 Post subject:
PostPosted: Wed Mar 16, 2011 11:19 am 
retrobike rider
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Location: rutland
Pretty much ignore seattube length , it's adjustable . A much more important measurement is the top tube length . Get a good comfy length with a suitable sized stem ( I prefer not much longer than 50mm but many are happier around 100mm , depends greatly on your riding style and where you ride ) . Next thing to worry about is the axle to bar height measurement ; again find something comfy that suits you personally . Best to go to a shop ( kinda why they exist ) ordering online is something best left to those who have already worked out their favourite lengths and angles . Nothing worse than seeing someone on a too big/small , long/short bike .

My explosif is something like 13" centre to centre and I'm 5.10 :lol:

The length and bar height is spot on for the bikes intended use , sprinting through tight corners . The small frame is stiffer and a fraction lighter than the " correct " sized equivalent , offers immense standover clearance for any sudden step off the bike moments too .


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 Post subject:
PostPosted: Wed Mar 16, 2011 1:02 pm 
Dirt Disciple

Joined: Wed Jan 05, 2011 11:21 am
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i'm 5'10" 30" inside leg and ride a small inbred and a med rockhopper but the inbred feels much better to ride 8)


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 Post subject:
PostPosted: Wed Mar 16, 2011 1:17 pm 
Moderator /Lincs, E & S Yorks Deputy AEC
Moderator /Lincs, E & S Yorks Deputy AEC
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Joined: Mon Nov 26, 2007 6:16 pm
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Location: RetroModding™ since 1988
Agrees with Perry...

Seat tube length is not the most important measurement

Top tube length is an important measurement

Stem length affects the handling, short = sharp/twitchy. long = slow and sluggish. A 80-90mm stem is a good start point, depending on what style of bike it is

Stand over (distance between your crotch and the bike top tube whilst stood over the bike) is also important, 2" is a good start point. It's not nice banging your obvious and necessary on the top tube.

I'm 5'9"/5'10", 31" inside leg & ride 16", 17" & 18" bikes, saying that height and leg are not the definitive measurements for bike sizing, they give a start point though.


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