Bike fit question, which is the more important measurement?

UndercoverElephant

Hi Chaps,

Just popping over here from the commuter section, hope you don't mind. I'm planning on getting my first road bike whenever my company manages to sort out the bike to work scheme. It will be for commuting, but I'd like to make sure I get the right size.

I got the Missus to measure me using the Competitive Cyclist fit calculator last night, and it seems I'm rather short in the leg, compared to the body. The results were suggesting I needed a 57cm-ish seat tube, but a top tube length nearer 58.5/59cm.

Now, the bikes I'm looking at seem to have either 55cm for both measurements, or 59 for the seat tube/ 58.5 for the top tube. I realise that the usual way is to go for the smaller frame, and add spacers/longer headset, but the larger frame would fit lovely for my trunk, but may be slightly long in the leg.

Which is the more important measurement, in your venerable opinions?

Slow Downcp

Definitely top tube as there's less scope for adjustment if you get this wrong.

Also, don't necessarily rely on the results you got off the online fitting tool - I did this some time ago and the results were strange to say the least. People of the same size may have different flexibility etc. If you're buying a new bike, any good LBS will include a fitting service - I had a fitting session at Epic recently and, despite thinking I had a reasonably good set up, quite big changes were made. The result is a faster, more comfortable position.

UndercoverElephant

The fit calculator I used does apparently give some slightly iffy results if you get any measurements wrong; They do mention it in the blurb. I think though it's looking about correct for me, I'm 6' 2" high and have an inside leg of 33", rather shorter than the average for my height.

I guess I could always get high heeled SPD shoes if the seat tube is too long

Thanks for your help.

il_principe

Slow Downcp wrote:

Definitely top tube as there's less scope for adjustment if you get this wrong.

Also, don't necessarily rely on the results you got off the online fitting tool - I did this some time ago and the results were strange to say the least. People of the same size may have different flexibility etc. If you're buying a new bike, any good LBS will include a fitting service - I had a fitting session at Epic recently and, despite thinking I had a reasonably good set up, quite big changes were made. The result is a faster, more comfortable position.

+1 It's not just about measurements either, it helps if the LBS can see your posture etc on the bike as well.

amnezia

Top tube length is always hard to calculate due to the difference between bikes with slanting top tubes and straight top tubes. A lot of the calculators assume a straight top tube where as many bike these days have an angled top tube. Only way to ensure a good fit is to try the bike out.;

bigflangesmallsprocket

Kinesis frames have slightly longer top-tubes and have a good rep. Apparantly their training frames have loadsa room for big tyres and mudgaurds, and have all the requisite holes too.

Claud Butler...erm...don't know if any of these have gaurd clearance, but I was looking at them a couple of years ago, and noticed some had LONG top-tube length. My reasoning was that I reckoned they used the same frames for drop/straight bars.

Crezor

The TT seems to be the harder one to get an accurate measurement for but I feel that it's also the more important one to get right. Granted both the TT and ST can be "adjusted" through changing components, raising and lowering things, etc. but the TT less adjustable overall so it's better to get that close right out of the gate IMO

redddraggon

Reach is the most important value by far.

a_n_t

Seems abit long for the toptube but who knows!

I'm 6'2" and have a 57cm tt with a 12cm stem

S2driveruk

Slow Downcp wrote:

Definitely top tube as there's less scope for adjustment if you get this wrong.

Also, don't necessarily rely on the results you got off the online fitting tool - I did this some time ago and the results were strange to say the least. People of the same size may have different flexibility etc. If you're buying a new bike, any good LBS will include a fitting service - I had a fitting session at Epic recently and, despite thinking I had a reasonably good set up, quite big changes were made. The result is a faster, more comfortable position.

heh, I wonder who that could have been oddly enough I have actually lifted the seat about 3cm and its made it feel better as the leg extends slightly further. Still, that print out was really odd so don't believe everything you see on paper!

Cheers
David

Slow Downcp

S2driveruk wrote:

Slow Downcp wrote:

Definitely top tube as there's less scope for adjustment if you get this wrong.

Also, don't necessarily rely on the results you got off the online fitting tool - I did this some time ago and the results were strange to say the least. People of the same size may have different flexibility etc. If you're buying a new bike, any good LBS will include a fitting service - I had a fitting session at Epic recently and, despite thinking I had a reasonably good set up, quite big changes were made. The result is a faster, more comfortable position.

heh, I wonder who that could have been oddly enough I have actually lifted the seat about 3cm and its made it feel better as the leg extends slightly further. Still, that print out was really odd so don't believe everything you see on paper!

Cheers
David

Hi David,

How you getting on with the Bianchi? I've actually dropped my saddles quite a bit more - Epic don't take any body measurements, but just look at the rider on a turbo and do a few balance tests to check for position. The only thing they measured was the angle of bend in the leg when at the lowest point. Seemed odd at first, particluarly uphill, but overall seems to be for the better.

S2driveruk

short answer....loving it, just wish i had more time on it!!!