embankmentlb

This is a project I have started and stopped several different times over the years. It is an early 90s GT Continnum with 700d wheels. Ultimately, my intention in to make it into a 650b drop bar gravel bike. After giving some thought to why I can never seem to complete the task it comes down to I do not like the Suntour ECE group. It just feels very cheap and low quality.

My dream would be to convert the drive train to a 3 x 9 Shimano setup, I have most of the parts already.

The biggest issue in doing this seems to be the existing 7 speed crankset.

Question? Can modern chainrings with ramps and pins be had if so will they work as this crank was designed for 7 speed?
Can a more modern triple road crank be fitted to this frame with a 73mm bb?
Thank you in advance for your help and ideas!

maddog34

as long as they're the correct BCD, they should bolt right up. i mix/match 7-8-9 drivetrain parts frequently.

the difference comes with the Derailleurs and cassettes, not chainrings... the 9 sp. ders. are narrower.

you can easily upgrade to Hollowtech II if you want... the HT II BBs fit right in, and so will the HT II MTB cranksets.
they will also reduce bike weight by a pound or more too, especially if you go with Deore or better.

be aware, a 9sp. cassette will NOT fit where a 7 sp was, unless you find a spacer behind the cassette.... they WILL fit where an 8sp. cassette was.... and so will a TEN sp. MTB cassette.

Andrew R Stewart 

700 D Bicycle Tires from Harris Cyclery (ISO/E.T.R.T.O. 587 mm) (sheldonbrown.com)

here's a link to an explanation of 700D sizing. Before you spend much $ make sure you can get tires that fit.

I might buy a used 1990s MtB and swap over the parts then sell off that MtB. Andy

embankmentlb

I have been researching this bike for some time. Many people say 650b tires will mount right up to these wheels. I will probably build new wheels in 650b anyway.

Arrowana

The bike likely has a Suntour cassette hub, which would make it incompatible with any Shimano cassette. So building new wheels makes sense. I have seen an example of 650b tires on a 700d rim, seems like a perfect fit.

A more modern but still square-taper road triple will likely work, but other spindle types are not likely to work. If you install it with the correct spindle length and the chainrings hit the chainstay, then it's not going to work.

Replacing the chainrings with 9-speed ones will also likely work, though there is a very slight chance that the chain could be capable of getting caught between chainrings while shifting. If you shift a bunch on the test ride and it doesn't happen, then it's likely going to be fine.

embankmentlb

Thanks for a the responses! I spent a few hours this weekend maintaining the GT and even went for a couple of rides. Everything works fine. My biggest gripe is the Suntour paddle shifters. They shift, index fine, but are simply cheaply made.
I,m thinking if I can replace those with thumb shifters the experience will be much better. Everything else left as is.