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GT ZR 3.0 sizing question(7 posts)

GT ZR 3.0 sizing questionmaximum15
Nov 6, 2002 4:01 AM
I am currently riding a '99 Trek 2300, 58cm. I am thinking about purchasing a GT ZR 3.0 frame, but I haven't been able to locate any info on how GT sized their road bikes. Can someone tell me if it was center to center or center to top. Any recommendations on GT size selection that would be comparable to a Trek 58cm? Thanks, Ken.
GT measured C-to-C. Can't help you with the trek comparo. nmRhodyRider
Nov 6, 2002 7:18 AM
My 56 is a little big...shawndoggy
Nov 6, 2002 9:39 AM
I don't know about Trek comparisons either, but betcha you could get away with a 56. I think that the frames are measured C T C (e-mail chuck at to confirm), but if you look at the frame the seat tube actually goes past the top tube by a cenimeter or two.

I was riding an old (1st gen) steel 55 cm LeMond, and I had a little more post showing on that bike than I do on this one, FWIW. I'm sure I could have gotten away with a 54.

BTW, I like the frame -- it's stiff and stable at speed.
measure it...C-40
Nov 6, 2002 3:36 PM
If you measure your Trek, you'll find that that a 58cm actually measures close to 56cm center to top.

If you're buying the GT frame from a retailer or an individual, either should be able to take a center to top measurement for you.
58cm ZR 3.0 runs largecking17
Nov 6, 2002 6:24 PM
The 2001 58cm GT ZR-3 runs large - more like a 59-60cm bike if you compare it to other manufacturer's bike specs. I am exactly 6 feet tall and the 58 is too big for me. The top tube is 58.5cm. Unfortunately the shop I bought it from sold me the wrong size and I did not find this out until I had a bike fit through a Serotta dealer experienced with bike fit and Serotta test/fit bike. (Hey, we all make mistakes as beginner roadies - lesson learned). A 56cm GT or 57cm "regular" bike is more my size. Otherwise, the bike is excellent and if you are on a budget, it is the best value in a 105 equipped race bike for only $1,000. See the posts in the reviews section.

The specs and dimensions (in inches) from the 2001 GT web site are below...

Available Sizes: 48cm • 50cm • 52cm • 54cm • 56cm • 58cm • 60cm
Available Colors: Lotto Yellow

Frame ZR-Road, double butted aluminum
Fork GT CR2.0 carbon fiber 1-1/8" threadless alloy steerer
Crankset Shimano 105 52/42/30
Pedals Ritchey Pro Road
Bottom Bracket Shimano Hollowtech
Front Derailleur Shimano 105
Rear Derailleur Shimano 105
Shifters Shimano 105 STI Flight Deck compatible
Freewheel Shimano 9 speed 12-25
Chain Shimano HG 72
Rims Mavic CXP-21
Tires Panaracer 'GT Racing'
Front Hub Shimano 105

Rear Hub Shimano 105
Spokes DT 15 gauge stainless steel
Nipples Brass CP
Front Brake Shimano 105
Rear Brake Shimano 105
Brake Levers Shimano 105 STI
Handlebar Syncros Ergo bend
Stem GT aluminum forged, front loading
Grips Black cork
Headset Tange Seiki DX-8 1-1/8" threadless
Saddle Sella Italia SPX
Seat Post GT aluminum alloy
Seat Clamp GT integral clamp

ZR chassis with custom-machined and butted aluminum tubing

New GT CR2.0 carbon fiber fork

Shimano 105 group

Selle Italia SPX saddle

Syncros ergo-bend handlebar

Frame Size 48 50 52 54 56 58 60
Head Tube Angle 72.0 72.5 73.0 73.0 73.5 74.0 74.0
Seat Tube Angle 75.0 74.5 74.0 73.5 73.0 73.0 72.5
Top Tube Length 20.5 20.9 21.3 21.7 22.2 23.0 23.4
Bottom Bracket Height 10.6 10.6 10.7 10.7 10.7 10.7 10.9
Chainstay Length 16.1 16.1 16.1 16.1 16.1 16.1 16.1

thanks for the excellent input, now for a 54 or 56 ??maximum15
Nov 6, 2002 6:41 PM
The Trek is an early '99 (actually made in late '98) and the paint is peeling pretty badly. It is to become my rain bike. The GT would be my everyday commuter bike. I plan to move all the Trek's Ultegra stuff to the GT and downgrade the Trek to 105. Since the Trek measures about 55 c-t-c and that is how GT measures, top tube length seems to be a very important deciding factor. I currently have a 120mm stem on the Trek and the top tube measures about 22.3 inches. The decision on a 54 or 56 is going to be a tough one. I may need input from the board here.
Close to 56cmcking17
Nov 7, 2002 4:06 PM
How tall are you and what is your inseam in centimeters? That will narrow it down a bit. Then measure your current 58cm bike and compare to the GT sizes... likely you'll end up near the 56cm GT. Your current bike's top tube length is nearly identical with the 56cm GT. They come (at least the 58 did) with a 130mm stem.