Cycling UK Forum

Many thanks, nsew and gaz,

for your further useful suggestions.

As soon as I have a good solution, I'll post here to let you all know what it is.

Chris

Does anyone know where I can find the maximum tyre size for a (road) front derailleur? I cannot find that in the Shimano documents.

PaulS wrote:Does anyone know where I can find the maximum tyre size for a (road) front derailleur? I cannot find that in the Shimano documents.

laterally? It depends on chainline mainly plus a few other things. The type of FD wouldn't make a very big difference.

Radial clearance is primarily about the frame geometry.

cheers

PaulS wrote:Does anyone know where I can find the maximum tyre size for a (road) front derailleur? I cannot find that in the Shimano documents.

Component manufacturers wouldn't be able to give you that information because it depends on too many variables to guage with any certainty, for example chainstay length, rim width and how it affects tyre width, etc. It'll be more suck it and see.

If you have a 28.6 seat tube you could also try a 34.9 band on front MTB mech but with an asymmetric shim to bring the range of the cage to suit a slightly narrower chainline. I haven't tried it but it's a thought.

https://www.sjscycles.co.uk/gear-spares ... hed-split/

Thanks for the replies. I spotted that Campagnolo quote maximum tyre size for a front derailleur as 32mm. And Shimano say their GRX gives wider tyre clearance, but doesn't quote a limit. That got me thinking, and measuring.

https://www.campagnolo.com/UK/en/Compon ... derailleur

https://bike.shimano.com/en-EU/product/ ... 810-F.html

For my next project I would quite like wider tyres, and up to now I hadn't considered the limitations of the front derailleur. I was worrying mostly about the frame and the brakes. Tyres probably 40mm or thereabouts. Don't really want a 1x drivetrain.

GRX uses a different chainline to more conventional 'road' stuff

cheers

I have a Campagnolo 9 speed triple front mech on my everyday bike. It is running 30-39-48 rings but is designed to suit a 53 tooth as standard. Despite the 5t difference in the top ring it produces a superb, near silent shift across all the rings and doesn’t need to be set high even with a 9t ring difference between rings. Given the shift is that good I figure it could probably deal with your set up.

Brucey wrote:GRX uses a different chainline to more conventional 'road' stuff

Well spotted, thanks. Looks like GRX will take 42mm tyres with the double chainset.

https://www.bikeradar.com/news/shimano-grx/