bike sizes/road/mountain

[h90]

I have a road bike size 54 and it seems just right.

I am 1.70 meter with rather long legs but not freakish long.

No I look at some Thai second hand FB pages and the have frames 49 and 52 mostly.

Are they very short or are the measure something different? In compare to my staff I am average some are taller some are shorter. 49 seems extreme short or I understood something wrong.

Also they have cheap Mountain Bikes. I am an street racer, but would like to explore a bit with the MTB. and there are great second hand offers. If I am 54 on the road bike is my frame size for a MTB also 54?

Edit size 47

[moonoi]

Mountain bike sizing is different from road and generally in inches. Probably 16" should be the right size, maybe 18".

Road bike sizing can be confusing as well, as not all manufacturers use the same measurement, some use center-center (c-c) and some center-top (c-t).

Both start from center of the bb, but one stops at the center of the top tube and the other at the seat clamp. Which means that the sizes are not directly comparable.

What you need to do is find the geometry of the bikes you are looking at and compare to your current one. The most important are stack and reach, followed by top tube length.

Sent from my iPhone using Tapatalk

[bobfish]

Try the Size my Bike App. On ios but I'm sure on Android too.

MTB frame is smaller sizing than Road to allow for dynamic weight shift. [often need to get the family jewels back and out of harms way]

Within MTB sizing, XC will generally have bigger [TT length] reach than AM than DH/DJ etc.

[h90]

Mountain bike sizing is different from road and generally in inches. Probably 16" should be the right size, maybe 18".

Road bike sizing can be confusing as well, as not all manufacturers use the same measurement, some use center-center (c-c) and some center-top (c-t).

Both start from center of the bb, but one stops at the center of the top tube and the other at the seat clamp. Which means that the sizes are not directly comparable.

What you need to do is find the geometry of the bikes you are looking at and compare to your current one. The most important are stack and reach, followed by top tube length.

Sent from my iPhone using Tapatalk

Thanks....I hoped for an easier way....

[john_bkk919]

Easier way: As moonoi suggested, most manufacturer size charts will recommend about a 17" frame for a 170cm guy. Some call this a Medium.

A Small would be about 16". Unfortunately, many manufacturers only offer 16" or 18". At your height you're probably between these two sizes. Trek Marlin does come in 17.5 (w/ 29 inch tires) and is easy to get, if that helps.

Since you like to 'size up' slightly on a road bike (ride a 54cm frame), an 18" size might be right for you. Or not.

Best to sit on a few bikes. Good news is, most shops here have 16-18" on display - just ask first as some can be moody. You could also find a local slow ride group and during the socializing someone might let you try their bike for size.

At the end of the day I wouldn't obsess about it too much. You'll know from riding. Can sell the bike on FB if it's really not working out and get a different size or a better bike once you're sure.

If you can find a good store that will help you intelligently with a basic bike fit that IMO is probably more important than saving a few thousand baht.

[MaeJoMTB]

MTB sizing also depends on your use.

Downhill needs smaller than cross country.

I'm 182cm

Downhill 18" fits, anything bigger and I'm crushing my parts.

Cross Country 19.5" is just right, I can get full pedal power.

Road Bike

56cm is just right.

[bobfish]

MTB sizing also depends on your use.

Downhill needs smaller than cross country.

I'm 182cm

Downhill 18" fits, anything bigger and I'm crushing my parts.

Cross Country 19.5" is just right, I can get full pedal power.

Road Bike

56cm is just right.

Correct!

[john_bkk919]

I sized down a little on my recent XC bike and found it gave a 'sportier' ride, more fun on trails. Don't know about downhill but have heard people choose even smaller frames.

From OP's comments and other threads figured he was looking at inexpensive Craigslist hardtails for light trail or construction zones in the city

[h90]

I sized down a little on my recent XC bike and found it gave a 'sportier' ride, more fun on trails. Don't know about downhill but have heard people choose even smaller frames.

From OP's comments and other threads figured he was looking at inexpensive Craigslist hardtails for light trail or construction zones in the city

Right....non asphalt streets in the south. due to rain they sometimes don't look like a street, something that could be only used with a 4x4 car. And mostly asphalt street till I get to rough area. So yes hardtail. Yes inexpensive, as I don't know how often I'll use it and I am more of a road bike person.

[h90]

Easier way: As moonoi suggested, most manufacturer size charts will recommend about a 17" frame for a 170cm guy. Some call this a Medium.

A Small would be about 16". Unfortunately, many manufacturers only offer 16" or 18". At your height you're probably between these two sizes. Trek Marlin does come in 17.5 (w/ 29 inch tires) and is easy to get, if that helps.

Since you like to 'size up' slightly on a road bike (ride a 54cm frame), an 18" size might be right for you. Or not.

Best to sit on a few bikes. Good news is, most shops here have 16-18" on display - just ask first as some can be moody. You could also find a local slow ride group and during the socializing someone might let you try their bike for size.

At the end of the day I wouldn't obsess about it too much. You'll know from riding. Can sell the bike on FB if it's really not working out and get a different size or a better bike once you're sure.

If you can find a good store that will help you intelligently with a basic bike fit that IMO is probably more important than saving a few thousand baht.

That thought is good ....I may just buy a cheaper second hand on FB. If the size isn't good, I just sell it again on FB. If I get more into MTB, I can still buy a better one later.

I guess I was overthinking things again.....

[Puwa]

Here's a good resource: http://www.singletracks.com/blog/uncategorized/mtb-frame-geometry-part-1-how-it-fits/