MNT raamisuurused vol. N

[Mati]

Ühes ost-müük teemas kerkis taas raamisuuruse diskussioon. Sellega seoses meenus mulle üks vastava teemaline jutuke Cyclingnews'i nõuandeosakonnast. Panen selle originaalis kopi-pastana siia ka. Point on see, et tänapäeval ei ole võimalik raamisuurusi üldistada erinevate rattatootjate lõikes. Reaalsus on erinev, 2-3 cm siia-sinna on norm? Lisaks õhku mõte, et mis on ikkagi see toru mille mõõt õige raami suuruse paikka paneb?

Küsimus
Modern frame sizes too small?
I am doing some research for a local touring club (SCBC). I agree with your statement on older bikes since I still have mine. One thing that I have found is that every company measures their seat tube length from a different point. It seems to me that they used to measure center to center but now they are measuring center to top or center to top of the seat clamp, which could result in a shorter head tube. Compact frame measurements are even worse as they seem to be a guess. Case in point, I have a 59cm Lemond, 60cm Cannondale, 61cm Fuji and a 62cm Trek and all have relatively the same top tube within millimeters of each other.

Why can't manufactures give a double measurement like the old Colnagos such as 60 x 59? To me, the top tube length is more important since a seat tube can be adjusted 20mm more easily than a stem, which if over compensated for could cause an ill handling or unsafe bike.

Vastus
Steve Hogg replies:

I couldn't agree more. Many years ago, all seat tubes were measured centre to centre. This makes sense to me because if you are designing a frame with a CAD program or even on graph paper, you need to work along centre lines and that used to be the case. Cannondale were the first manufacturer that I am aware of that started measuring seat tubes from centre to top, possibly because their larger diameter top tubes skewed the measurement in terms of what most people used as a point of reference; i.e. a skinny tubed steel frame.

Anyway, centre to top seemed to become a peculiarly American thing initially, which made no sense to me as all the other frame dimensions were measured centre to centre. I think what happened is that once centre to top became the de facto American standard and given the size of the place as a potential market, many manufacturers obliged by framing their geometry specs in terms that Americans had become used to.

No problem with that but I wish there was some convention on what centre to top means. For Cannondale, Klein and others it means centre of bottom bracket to a point on the seat tube that is in line with the top of the top tube. For others it means from centre of bottom bracket to the top of the seat tube including any seat tube extension that may be there.

A few years ago Trek won my unofficial award for the most confusing range of measurements. Their carbon frames were measured from centre to seat tube top and the seat tubes had a modest extension. Their aluminium range (2300's etc) were measured the same way with a substantial extension on the seat tube yielding a much lower top tube for the same nominal seat tube length. To Treks credit though, they supplied bikes with generous steerer tube lengths.

Merida use a very long seat tube extension and measure centre to top meaning if you buy the same nominal seat tube length as you would with other brands, the front end of the bike is a long way further down than many buyers expect it to be.

The other frustration is that many manufacturers supply incomplete geometry making it harder than it should be to compare dimensions. Colnago win the prize for the most complete frame geometry charts. They are a little hard for many to read at first because no matter how you measure a frame, Colnago have that dimension on their geometry charts. If you take the time to wade through the complexity, at least you have a level of certainty to what a rider may be considering purchasing.

[Kuldar]

Canyon rataste lehel on päris popp perfect position system:
http://www.canyon.com/tools/pps.html
mis peale strateegiliste mõõtude sisestamist näitab virtuaalset passatkat (start ->) nii maanteka kui baigi jaoks. Näed nö. ennast kõrvalt... muudad raamisuurust, mnt-valikud: alt või linkidelt, sportlik asend või "turist" jne.
Vaevalt et see nüüd universaalne fittingu mudel on (a mängida on ikkagi kihvt:), eri tootjatel erinevad geomeetriad jne.jne. Kõige olulisem on ära tabada oma jaoks õige top tube pikkus (sloping geomeetria puhul effective), millest möödapanekut ei korva stemi pikkusega ja sadula setback`iga mängimine.