tdilf

I run Shimano 2 X 11 drivetrain with 38c slicks on my Niner. Today I threw on some 40c tires with a slight knobby pattern and was surprised to see how close the front derailleur was to the tire when shifted into the big ring (about 2mm). I run a Shimano Tiagra front derailleur and was wondering if there is a clamp on style front derailleur that would provide more clearance. I was thinking GRX but that probably has a different pull ratio. I would love to have a 42c knobby on the rear on some occasions but it will not work with this front derailleur.

unterhausen

Pretty sure the GRX has the same pull ratio. One possible issue is that it's meant for 2.5mm wider chain line. Hard to imagine this is a real problem, but it's good to keep in mind. The other option is a cx70, if you can find one

Koyote

I believe the GRX fd might require the matching GRX crankset...But both will work fine with the rest of a Shimano drivetrain, and will indeed give a bit more tire clearance. They will also give a better chainline on a bike with 135mm rear spacing.

Another option is to bring your bike to a good shop. They might source a different fd that will give more clearance with your current crankset. unterhausen 's recommendation is probably worth checking out.

zen_

Can you post a picture of the clearance?

I attached 2 photos showing the difference between the newer style Shimano FD (R5801 7000 8000 9100 GRX) that pulls a bit differently, and an older 5700 FD on my road bike (with a wider seat tube too). The new style FD actually seems to poke in a little more than the older FD, but as others have mentioned, if you switched to a GRX FD with a GRX crank, that would bump out the Q-factor 2.5mm, I believe.

The real problem here though is that the rear tire is coming in too close to the seat tube for wide tires with a FD. Notice that on my gravel bike with 700x40c (effectively) tire, the wheel is far enough back to completely clear the FD altogether. I think your best option here if you want wider tires is to switch to 650b, if that will clear the FD altogether. I would hate to see you spend a bunch of $ on a new FD and crank just to have the same problem, although the newer style FD does pull a little easier, and look cleaner (when the top cap doesn't fall off and get lost..).

tdilf

I did just change the bottom bracket and crankset. The new crank is an Easton that has a wider Q-factor. I had to add spacers mostly to the drive side which would push the big ring further out. This would also make the front derailleur pivot more to make a shift. I will go grab a photo.

Bryan C. 

Common issue with that style FD. Get a Shimano 105 or Ultegra derailleur as noted in the pics zen posted above. The modern versions of those FD have addressed that issue with a newer design.

For the GRX FD, might be worth checking out too. The Tiagra 4700 series is a 10 speed drivetrain but uses the current 11 speed pull ratios.

Shimano also sells a braze on clamp that can be used with their higher end derailleurs. https://bike.shimano.com/en-EU/produ...SM-AD91-L.html

mstateglfr 

Bryan C already said what needs to be done, but ill jump on and confirm it, for what thats worth.

The 4700 Tiagra group may work fine, but its terrible from a compatibility perspective. Its alone on an island for the most part and super confusing what parts are interchangeable with other group levels.

4700 is 10 speed, but the shifters pull the cable the same amount as the 11 speed groups. This makes for an inelegant setup on rear shifting, but makes for fine front shifting(since both 10 and 11sp are 2x).
The long arm design of 4700, 5800, and 6800 FDs was dropped for a reason- tire clearance doesnt work well with some bike designs.

Get yourself an R8000 FD, watch a youtube video on how to set it up(because its different from other designs, of course), and you will have more clearance. The fact that your Easton chainrings are pushed out further could be an issue if they are really far out, but if your current 4700 FD has the reach to shift both rings, then an R8000 will have enough reach.

tdilf

Thanks for the insight guys. I have been upgrading this bike since i got it (originally with Tiagra 10 speed). Now it is mostly Ultegra 11 speed except for this pesky front derailleur. I will look at the new generation Shimano front derailleurs.

mstateglfr 

Oh, well if the shifters and rd are already 11sp, then for sure just grab an r7000 fd and call it a day.

Also, I have a couple r7000 and an r8000 fd on my bikes and I cant tell the difference. They weigh the same, set up the same, and have the same stiffening bolt(a new feature on shimano FDs).

Elvo

Yep an FD R7000 will solve this problem for $30