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26" vs 28" wheels on TT bikes?(9 posts)

26" vs 28" wheels on TT bikes?Kjull
Dec 1, 2002 10:41 PM
Hi,

I've learned that sometimes one uses 26" wheels and other times 28" wheels on the time trail bikes.
Why is one favoured from the other, and what decides which size to choose?
Personal flavour, course profile/layout or others?

Kjell Eirik
Norway
re: just to standardize the vernacular... 650C vs. 700C wheelsAkirasho
Dec 2, 2002 2:02 AM
... there are a few schools of thought... and you've got options depending on what works best for the individual.

I've got both types and don't notice a significant difference (suffering is suffering regardless of wheel size).

http://www.slowtwitch.com/mainheadings/techctr/geometry.html

http://www.bicyclesports.com/technical/davespage/index.html#072699



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Akirasho....Starliner
Dec 2, 2002 8:54 AM
The GT looks to have a shorter seat tube than the Cervelo - the difference in seat & handlebar height appears much more significant than any difference in BB height between the two.

I was recently considering a particular TT frame, but was hesitant to move on it because its seat tube was unusually short (51), while its top tube was standard (58) for a guy around my height (6'1"+).

I think you are around this same height... how do you think that 51-ST/58-TT frame would work for somebody our size? An uncomfortable fit?
Akirasho....str8dum1
Dec 2, 2002 11:36 AM
height difference is due to 700 vs 650 wheels (duh)

as long as the top tube is the correct length, you can get seatposts in almost any length. I have never seen a production bike with said geometry. even compacts are only like 51, 56.

that 51 could be c-c seat tube but really 56 c-top if it has a mast or something. regardless, u can buy a long seatpost.
Akirasho....Lactate Junkie
Dec 2, 2002 4:27 PM
No it's not--duh. Smaller wheels don't make you closer to the ground. Need to find another reason.
Akirasho....gray8110
Dec 2, 2002 7:02 PM
The top tube is definitely lower on the GT than on the Cervelo.. The smaller wheels would make a very small difference assuming similar geometry.. but geometry isn't the same.. compare the steerer tube angle.. It is nearly vertical on the GT bike, very quick steering and the steerer on the Cervelo is very relaxed.. The difference is huge. Assuming the bikes are the same size, to put the same top tube height on the 650c GT, the steerer tube would have to be REALLY Long.. That would make the front end noodly.
yes differnt geo, but look at wheelsstr8dum1
Dec 3, 2002 12:11 PM
the 650 wheels are about 1/2 a line smaller than the 700. the seats are about 1/2 a line different in height also.
still not correctStarliner
Dec 3, 2002 2:33 PM
You're basing your conclusion on the bottom to top difference in wheel dimension, when the bottom to axle measurement is the correct basis to the incorrect point you're trying to make.
... actually...Akirasho
Dec 3, 2002 7:36 PM
... the two share 'pert near the same size (61/Large) and geometry 'cept the headtube on the GT is about 1cm shorter...

Indeed, the challenge of riding the GT for me is that I suffer a bit from Dunlop's Syndrome... my belly done lopped over my belt... so that 1cm difference is noticable at the very least... and at the present time (still in treatment for my syndrome) is only ridden over shorter 10 mile TT courses.

When I sized the GT, I based the lion's share of my decision on the top tube and effective seat tube lengths (again, near identical to the Cervelo), wishing, hoping and praying that that short headtube wouldn't haunt me too much. Because the bike uses an Ouzo Pro Aero with a CF steerer, additional spacing would be impossible.

As far as seat tube length is concerned, it would depend on the adjustability of the frame/post in question... the GT is adjustable, and believe it or not, it could actually be raised about another 2 inches! Some aero frames (with aero or proprietary posts) have limited adjustability and seat tube length could be critical... but generally, I'd worry more about top tube and head tube.

I like top tubes in the 58 to 59.5cm range and this works well for me (both on the road and on a specialty rig)... your results may vary (Dunlop's and flexibility being a couple key factors). Indeed, the original fit on the Cervelo called for a 110mm stem... it now sports a 140... butta. If possible, set yourself up on a fit fixture and play with the numbers (some shops/owners might let you play around for a six pack and a loose meat sandwich)... a good friend of mine uses a LOOK Ergo stem and an adjustable (fore/aft) seatpost to dial in his fit.

We abide.

Remain In Light.

Be the bike.