Sizing Query for new bike

mike_swindon

Hi all,

Im thinking about joining in the commuting fun now winter is slowely passing and the lighter evenings are here!

I am 6' and ride a 17" Giant Reign1 MTB, im looking at getting last years Felt QX60 to commute on to work but the sizing is in CM's!...do i just comvert the cm's to inches to get the sizing formyself?

I dont want a massive frame with little standover as i have traffic light to stop at!

The choice i have it 50, 53 or 56 cms.

Thanks for any help.

Mike

Random Vince

hi, i'm just over 6ft and ride an 18 inch mountain bike and a 58 inch road bike with a fair amount of seat post stuck out.

my bikes are currently sat next to each other and as you'll see from the photo the saddles sit at about the same height (been using the mtb on road when the road bike was broken, it normally sits a little lower) but the top tubes have a fair bit of difference as I occasionally want to put the MTB's saddle right down for crotch clearance on jumps etc

mike_swindon

Can anyone else advise me as to what size to get? Shall i get the 50cm if i want it similar to my MTB?

Thanks,
Mike

alfablue

A 17inch mtb frame may be measured in a few different ways (often centre of bottom bracket to centre of where the top tube dissects, but there are other approaches). What you really need is the "effective" seat tube height, so the height at which an imaginary horizontal top tube would dissect the seat post, and compare this on the two bikes.

You also need to compare reach, so the top tube length plus stem length. To a lesser extent the stem height (and / or head tube length and any rise on the bars) will have some effect too.

Dimensions of apparently the same size frame can differ dramatically between brands, for example I needed an extra large cannondale MTB when I used a medium-ish Rock Lobster - each brand has its own approach (and they are not always that logical), so you need to look at actual detailed measurements not quoted frame size. It won't be reliable, either, just to convert the MTB inches to the Felts cm, they are likely to give very different bike sizes (more so if it were a true road bike frame, maybe less so as it is an MTB-like fram, but nevertheless, it is not a reliable way to work out your size).

You can get the details of the Felt geometry here (click on the "Bike Geometry" link at the bottom of the picture) and you can make measurements on your MTB to compare, just make sure you are comparing like with like, i.e. the same measurement taken in the same way.

Having said all of the above, the only proper way to tell is to try one in the shop.

edit: Just looking at the felt geometry, in their 52cm size they quote seat tube height in two ways,"ST C-C" will be centre to centre (as I described above) at 461mm, and "ST C-T" which I think will be the seat tube length to the imaginary horizontal intersection with the top tube, and this is 520mm, so 60mm difference. Compare this latter measurement with the same on your Raleigh. Likewise, Top Tube (TT Horiz) is quoted for effective length (the distance on a horizontal to where it would intersect the seat tube) at 580mm, whereas the actual TT C-C is shorter at 554mm, it is the first measurement that matters, make that same comparison.

mike_swindon

wow, thanks for the greatly detailed reply. And as you said, the only proper way is to try one for size as it were!....Only issue is i cant get hold of this bike local to me, so it will be a mail order jobby.

Ill get on the case of checking the dimensions now.

Thanks again,
Mike

alfablue

Hi Mike

Note I updated my last posting with more detail.

I understand the problem - if its the bike you want at a good price, got to get it! Bear in mind some online retailers are better than others if you need to return it. Wiggle are very good in this respect, they have several Felt hybrids.